Banebot 56mm gearbox - double D - RELOADED
 

This thread is actually a continuation of this thread.

The thread was getting so long that I was worried that folks with dial up would miss the ship date waiting for the page to load.
It is a complex issue so I will try to summarize.

History:

• FIRST sourced Banebots for the 2007 KOP transmission in the Summer of 2006 after having evaluated prototype transmissions in both the 1-CIM and 2-CIM configurations.
• Shortly after kickoff, I became concerned about the double D joint.
• Analysis and Bench tests confirmed that there was reason for concern.
• Earlier this week a team first reported excessive wear in the D joint (the bow tie effect) confirming the failure predicted by analysis and demonstrated by bench tests.
• More test were done and a few more reports of bow tied carrier plates.
• FIRST published the issue in UPDATE #5, warning teams that there is an issue and that folks were working on it.
• Much help has been offered by the FIRST community to address this problem.

The data is not 100% certain, but here is where we stand as best as I can summarize:

• In some (but not all) conditions, the double D hole in the carrier plate will plastically deform into bow tie.
• The field failures up to this point show that the bow tie opens up gradually (many cycles not several fatal blows). As it fails, more and more backlash is observed in the gearbox.
• It is reasonable to expect that bow tie will eventually (after 100's of cycles) resulting in complete failure (though as of this moment, complete failure has not reported except as a result of a torque to failure bench test I performed)
• The carrier plate is significantly softer than the shaft.
• While the exact alloy of the carrier plate is not known, it is believed that the composition of the plate does not lend itself to easy hardening.

What is next:
Couple of teams have volunteered to be best subjects.
They will run a baseline set of tests to determine the extent of the problem
These teams will act as our proving ground to evaluate proposed solutions

Working together with Banebots, FIRST, and the ChiefDelphi.com I believe we are closing in on a set of solutions to this issue. Based on my communications with Ed Yackey from Banebots, folks from FIRST, and many in the larger FIRST community, I can assure you that everyone is committed to working this issue to a successful conclusion.

So what is that solution?
I cannot say 100% for sure at this point because there are still a few unknowns that could change the answer, but this is what I believe is the most likely scenario at this point.

Plan A:

New harder (RC 23) carrier plates. Hardness equal to the hardness of the output shaft. This should result in close to a 2X increase in the max torque

Plan B:

New harder carrier plates (RC 23) with square hole (rather than round with double D) Plus modifying or making new output shafts with square drive. Should give approx. 2X increase in max torque over Plan A.

Plan C:

Same as plan B only with harder (RC 40) carrier plate and output shafts. Should give approx. 1.5X over Plan B

1-CIM motor:

It is my opinion that Plan A will address this issue

2-CIM motor:

It is my opinion that Plan A will possibly address most of these failures but in order to fully address this issue for teams that are using 2-CIMs, we may have to go to Plan B.

Status:
We are working to have a sample solutions of Plan A to test for the weekend. We are in the process of planning Plans B & C but believe me, we will have them ready when the time comes. Also, I have not listed a Plan D but trust me, we will come up with a Plan D and implement it if that is what it takes to make everything come out in the end.

Closing:
This whole thing stinks. Nobody wanted this. But, I am proud of the many people who were part of the solution. And, yes, I say solution. The proof of the pudding is in the eating but I am quite confident that we have all the ingredients of a tasty dessert on the table.

Best Regards,
Joe J.

UPDATE:
I have just attached prints of the carrier (4:1 & 3:1) and the output shaft. I have versions with a 11/32" square hole. This is a commonly available broach size that is just under the 9mm flats on the DD (11/32" = 8.73mm).

I put these prints up here for 2 reasons:

• • 1st to get more eyes to look at the prints to find dimensions we have missed or mistyped.
  • 2nd to allow teams with appropriate resources to make the parts for themselves (and hopefully report back their success or failure)

Before I start a panic, note that NONE of the plans above involve teams making these things for themselves. If a team CAN make them for themselves, they may do so, but rest assured that we will not leave those who cannot stranded.

Some notes:
The material is spec'd at 1040 hardened, tempered to RC40. That is harder than we need. There are some who feel that the parts can be made from 41XX mat'l and not hardened. That is certainly true for RC23.

The square is just under the 9mm flats so it is possible that a team can modify the existing shafts to mate with a 11/32" broached hole.

These prints were not made to correspond to my organized Plans A, B, & C so they are kind of a mish-mash. Pick and choose as you see fit.

Please check dimensions for us. Check fits and tolernances too if you know what you are doing in this area. Report errors and clarifications needed.

Note that the dowel pins on the existing carrier are undersized 4mm pins. Brian Orr (my long suffering friend who did these prints for me -- staying to 11pm and his last day of working for Delphi -- special thanks to Brian whi is not even a FIRST fanantic.) sized the hole for such undersized dowel pins. If you are going to use standard 4mm dowels, you may have to open up the holes appropriately -- press fits are tricky be careful.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Great work on this, Dr. Joe. I know that the biggest priority is to get the 56mm gearboxes fixed, because the vast majority of teams will probably be using them for their drivetrains, but are there any similar plans in the wings for the 36mm box? I'm sure that there are a lot of teams worried about that one, too.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I don't understand something - is the problem in the banebot gearboxes or is the problem in the transmissions?

Thanks,
-Guy

Re: Banebot 56mm gearbox - double D - RELOADED
 

The Banebots 56mm Orbital gearbox is a transmission.

Re: Banebot 56mm gearbox - double D - RELOADED
 

There is one solution you missed...


Junk the whole things and get Andy Mark shifters!

:)

In all seriousness, we tried to make these things work out, but we aren't willing to take a chance on them.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I think it would also be a good idea to include the 42mm gearboxes. A lot of teams are using them with the FP motors and with less than 3 weeks left, redesigning a mechanism may be too much for some teams. It's a shame seeing some interesting designs or mechanisms be scrapped just because of one lousy carrier plate failing.:(

Re: Banebot 56mm gearbox - double D - RELOADED
 

I would like to thank Dr. Joe and all the others working to fix this problem. My team is using the banebots gearboxes and we feel it is too late in our design process to completely switch them out. We here at team 1676 anxiously await any solution to the problem. We would volunteer to help but unfortunatly our machining capabilities are limited and we usually have to outsource any custom cut or welded parts.

Thank you all once again for all of you working to rectify this situation.

Re: Banebot 56mm gearbox - double D - RELOADED
 

A note to all the folks concerned about the 42mm and 36mm gearbox:

I appreciate your concern but the cases have almost nothing in common with eachother.

Let me explain. The 56mm gearbox is PURCHASED by FIRST to put in the kit. While teams can use them for any purpose they see fit, the main purpose that FIRST decided to buy them is to drive robot chassis for teams with scarces resources. The reason I have been loosing sleep is that I believe that a drivable robot is so fundamental to a successful FIRST season that the mission of FIRST was at risk of being damaged if teams were going to see these failures in competition.

Now to the 36mm gearboxes. These are gearboxes that Banebots DONATED to the kit. More than that, they donated an extra motor and other goodies. Beyond that, they offer for sale other things that make building robots easier and more robust.

There is literally NOTHING in the FIRST KOP that cannot be damaged if used beyond their limitations. All KOP items, actually, all items have limitations.

In my work to solve the 56mm Gearbox Double D issue, I found that I could extrapolate some of my results to the 36mm gearbox that Banebots donated to the KOP as well as the 42mm gearbox that Banebots sells. I THOUGHT I was doing the FIRST community a service. I was offering advice as to what I thought a conservative use of these parts would entail.

While I am happy that I have perhaps prevented some teams from designing a mechanism that will break. I regret that many teams have inferred from this several false ideas:

• The 36mm and 42mm gearboxes are defective* -- THIS IS FALSE
• The 36mm and 42mm gearboxes are not extremely useful for a FIRST robot -- THIS IS FALSE
• FIRST and/or Banebots should do something to remove this limitation -- THIS IS FALSE

Perhaps my greatest regret is that my conservative estimates have caused significant financial damage to Banebots**. While I have not spoken to Banebots about specific numbers, it is clear that teams are mis-interpreting my conservative estimates to mean that they should not use Banebots' 36mm and 42mm gearboxes at all. Nothing could be farther from the truth.

While teams are free to do whatever they want, I really really hope that teams will think and act rationally. I believe that if they do, they will end up buying quite a few products from Banebots. I think this will be a good thing for a number of reasons not the least of which that FIRST benefits from companies like AndyMark, IFI, and Banebots being around and supporting FIRST. Sales are what keeps a business in business. Sales to FIRST teams make donating stuff (or selling it at a deep discount) to the FIRST KOP a lot easier to fit into a business plan.

For what it is worth.

Joe J.


*believe it or not, a team actually tried to return the KOP 36mm gearbox claiming it was defective -- this is insanity, not to mention about the most ungracious request I can imagine. Think about it, a company donates something to the FIRST KOP and a team has the audacity to request a cash refund because the part could, in theory, be broken. My blood boils!!!

**I will state again for the record, other than the fact that Robotic Amusements, Inc. uses Banebots as a supplier of some of its motors, I have no financial tie to Banebots at all. To be specific, they don't pay me, I get no commision, I don't get a discount or kickback on other sales, I am not a paid consultant for them, etc. etc.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Dr. Joe...

Team 166 has been following these threads and support everything you and all the other teams offering suggestions, perform testing, etc.

However, I believe that it would be a much easier task for those of us planning to manufacture new parts if we had drawings to use.

Are there any plans from BaneBots to supply the drawing for the carrier plate for the 56mm gearbox?

Please forgive me if this question has been answered in a previous thread. My time is limited to search for such information.

C. B. Petrovic - Team 166

Re: Banebot 56mm gearbox - double D - RELOADED
 

Lockheed Martin seems to be in the mood to detemine the carrier plate alloy. I found a sympathetic lab manager that has at his disposal all the NDE equipment we use making the space shuttle external tank. Are people still interested in this?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Joe, Many thanks to you and others for your tireless efforts to remedy this situation.
I agree, and I am sure you are right about the solution. It seems everyone involved was trying to do good. I hope that any losses (both tangible and intangible) are minimized for all concerned parties.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Good Idea. It was in the works but I had to sleep last night and I had my job to do this morning. I attached a zip file to the first posting above.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Thanks but I think the need for mat'l reverse engineering has past. BUT... ...you're on the list. We will keep you in our pocket for a later date when we might just pull you out and use you.

Thanks again.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Thanks again for your hard work this week, Joe. Cool heads will prevail and I hope we don't scare away suppliers...the more the better.

Thanks also for the drawings. I sort-of guessed from measurement, knowing it was metric, but that will help a lot. I am going to try to cut some test carriers out of O1 or A1 tool steel (similar in hardness to the 42mm carrier and capable of being tempered). It will mean hunting for waterjet time, which is tough because there is a class that uses them a lot right about this time of January/February. But I'll let everone know how it goes.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Good work on the drawings Joe. Is there any reason why a single plate couldn't be used for both the 4:1 and 3:1 ratios? Just rotate one bolt pattern by 36 degrees relative to the other. That might make the manufacturing of replacement plates more streamlined.

Re: Banebot 56mm gearbox - double D - RELOADED
 

got em!

thanks again, Dr. Joe...

C.B. Petrovic - Team 166

Re: Banebot 56mm gearbox - double D - RELOADED
 

Joe,

The material stated on your drawing. Is that the material we should make it out of, or the material it was made out of?

Re: Banebot 56mm gearbox - double D - RELOADED
 

I would like to add that we used smaller Banebots transmissions last year for Mabuchi and Fisher Price motors and found the quality and service excellent.

Re: Banebot 56mm gearbox - double D - RELOADED
 

There are many mat'ls that will work. I recommend that you talk to your source and pick one that has a RC23 hardness out of the shoot (i.e. without heat treating). The mat'l on the print is what I would do if I wanted to end up with a RC40 or so part. But you can relatively easily machine RC23 parts (or I should say, some machine shops can). Talk to the source about what they can get easily. If the mat'l is RC23 or higher, it should be fine.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

The only reason not to is that if you are making a bunch of them the price will be a bit higher. For ones and twos, the set up cost would swamp the extra machine time so it is likely that you could get all 10 holes for almost the same price as just 5.

You pays your money and you gets your choice...

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Joe,

First off, I want to say thanks for all that you, other volunteers in the FIRST community, and Ed at BaneBots have been doing to resolve this issue. We are confident that those involved will ensure that an excellent solution is arrived at for the problem with the 56mm gearboxes.

Our plan since seeing the 56mm gearbox in the KoP was to use the 56mm gearbox with the 2-CIM adapter and 16:1 gearing for our robot drive system. We based our decision to do this largely upon excellent experiences we had last year with the use of the BaneBots 36mm gearboxes (5:1 and 25:1 in low-load, high-rpm applications for our robot's shooter wheels and ball feed roller in "Aim High"), presuming that we would have similarly happy experiences this year. We purchased all the needed components for the above, as well as enough of everything to equip a complete 2nd drive base.

We have not yet tried driving the robot with the 56mm transmissions, so our carrier plates are still undamaged. I have a few questions that are probably shared by many other teams, so I'll ask them publicly so that all can benefit from the answers:

1 - Should we drive our 2007 drive base around (even though this will almost surely damage the carrier plates) for our testing so that we can proceed with robot testing even though we'll be damaging our currently undamaged carrier plates? i.e. Has it been decided that the eventual solution will involve giving new carrier plates to teams at no additional charge?

2 - We presume that the solutions will be applied not just to KoP 56mm gearboxes, but also to 56mm gearboxes which teams purchased from BaneBots?

3 - As one of the teams planning to use the 56mm gearboxes with 2:1 adapters and 16:1 gearsets, we'd like to know if we can help influence the decision to use Plan C for teams that purchased 2:1 adapters? (We view Plan B as a risky solution for 2:1 adapters and 16:1 ratios when used in the dynamic loading situation of robot drive.)

Thanks again for all your effort and that of so many others on this. As a team with almost no machining capabilities (we build the robot in team members homes), we're very relieved to see that the proposed solutions won't require our team to have parts machined or heat-treated!

Thanks again,

--ken

Re: Banebot 56mm gearbox - double D - RELOADED
 

Thank you very much for the drawings.

I see one problem: The dimension given on the square end shaft is 8.633±0.013. The problem I see is the hypotenuse of this square, as toleranced, will be between 12.191mm and 12.227mm. The smallest dimension for the hypotenuse, 12.191mm is equivalent to 0.480" and is larger than the ID of the bearing (0.472") on the 56mm Banebots transmission.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I believe the intent is to have a square with slightly rounded corners, since the shaft must be 12.0mm diameter.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Yes this is the intent. Machine them round, then cut in flats to make them square.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

By some twist of luck, my steel came early this morning AND I was able to get 20 minutes on the waterjet. So I now have four A2 tool steel 56mm carriers, which are about the same hardness as the originals but can be treated to pretty much anything from C20 to C40. I will probably shoot for C23 for now to match the current shaft.

My dimensions were as the drawings say, except:
a) I went tighter on the double-D: 0.470in (11.94mm) radius and 0.350in (8.89mm) flats. With the taper from the jet, this seems to be a good press fit, but may require some filing.

b) The pins will be press fit in the other direction, against the taper of the jet, so I just made their holes extra small, 0.150in (3.81mm), and I'll drill them out later.

The stock I used is McMaster part #9019K147, 18"x2"x5/32" A2 tool steel, but I wouldn't recommend it unless you have heat treating capabilities, since it comes soft (B89-99). I am just using it to have an adjustable hardness to play with.

In the attached picture, the two carriers at the left are the originals (1CIM, 12:1) with almost no visible damage after "mild" usage. The four at the right are the new A2 tool steel ones that I will try to harden to C23 for testing.

Re: Banebot 56mm gearbox - double D - RELOADED
 

1) From what I have seen, failure of the carrier does not damage any of the other parts. This is fortunate because I know there is almost no way that we could replace 2000 or so ring gears if they were damaged by the failure. Also, we have all but given up on the idea of hardening the existing plates, so, I think you should feel ok driving your robot with the transmissions you have in hand.

I have high hopes to have good data over the next few days (good meaning accurate, not good meaning I am happy with the result). I may amend my advice on this topic if I find that a short driving delay now saves a longer delay later -- but that is not the case from what I know now and I don't expect it to be the case later.

As to making the fix free to the teams, I am not the person to sign the checks so I hesistate to say yes, but I can tell you that this is the direction everyone I know is working toward. I have made the suggestion that we pay for it with a pledge drive at each regionals. Imagine something akin to public TV's pledge week ... MC "We are going to bring you the next match very soon it looks like it is going to be a doozy." Field announcer "...BUT FIRST, we need to have 10 more first time donors to the Double D club!" ;-) Seriously though, I think so. But I am not the final answer on that subject.


2) My primary focus is to get the teams that depended on the reliabilty of these transmissions a solution that will serve them well. I can't speak for Banebots, but everything I know about them leads me to believe that they will stand behind their products. Sorry for the refrain, but I am going to have to answer with I think so, but I am not the final answer on that subject.

3) As to Plan B vs. Plan C for the 16:1 2-CIM case, I will with hold judgement until we get some good data. The entire team is focused on getting a set of solutions that deal with all 4 varieties (12:1/16:1, 1-CIM/2-CIM). I have reason to believe that Plan A will cover both 1-CIM cases and that Plan B will cover both 2-CIM cases (actually, I have reason to believe that Plan A will actually cover most 2-CIM cases too but to be safe, I have argued for preparing Plan B so that it is ready if we need it). Plan C is then a contingency upon a contingency. But, we will let the data take us where we need to go.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

The 4140 prehardened stock has arrived for us as well, and should be in the hands of our model shop along with the drawing package.

Our plan is to remanufacture the 3:1 DoubleD plates and we should have some test results this weekend. We're running a 4 transmission/motor chassis.

C. B. Petrovic - Team 166

Re: Banebot 56mm gearbox - double D - RELOADED
 

Update:

I tried reassembling my 12:1 gearboxes today with the new press-fit A2 tool steel plates I cut and discovered a few issues with press fitting that I didn't think of:

1. I had to file out some to get it on at all, which is my fault because I went way under on the hole to be safe. Doing this, though, caused significant alignment problems. It was tough to get the press to go on straight and if it is even a little bit off, the gearbox will be tend to be stiff at certain positions.

2. Assembly was generally more difficult because of the extra constraint. I couldn't, for example, assemble the rest of it and slip the shaft in later.

3. Luckily this didn't happen because I over-filed a bit, but if you press it on real tight, it will be tough to get back off. I can't think of a good way to pull it back off since the plate comes so close to the bearing block.

So in conclusion, I think I'm going to file these out to be close fits, but not press fits. Loose enough that they will slip on and self-align during operation. If I cut more on the waterjet, I'll just make them 12mm x 9mm exactly.

Also, I was mistaken in my previous post: A2 tool steel will temper to C40-C65, not C20-C40. It comes already just below a C20. I will shoot for the low end of the tempering range, so as to avoid brittle failure.

Re: Banebot 56mm gearbox - double D - RELOADED
 

one could use a bearing separator, maybe?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Probably would work. I'm sitting here watching American Chopper and filing carrier plates...it's mildly relaxing. The next set I put on I hope never to have to take off anyway. I think after I finish with this gearbox stuff, I'm taking the rest of build season off. :rolleyes:

Re: Banebot 56mm gearbox - double D - RELOADED
 

At this point, we have machined carrier plates and axles out of the 4130 steel that we have on hand, using a square broach for the carrier plate. We have hardened at 1600F with an oil quench, and tempered at 800F.

A link to a table showing the strength characteristics of 4130 as a function of the temperature for temper is shown below:

http://www.eng-tips.com/viewthread.c...=116052&page=4

<<<<<
Following is a listing for tempered 4130 steel:

UTS YS

C F MPa psi MPa psi El RA HB

205 400 1627 236 1462 212 10 41 467
315 600 1496 217 1379 200 11 43 435
425 800 1282 186 1193 173 13 49 380
540 1000 1034 150 910 132 17 57 315
650 1200 814 118 703 102 22 64 245
>>>>>



The yield strength at this temper is 173,000 psi and the elongation at break is 13%, not too brittle.

We have assembled and broken in the gear boxes using no load and 8 volt power, running both ways until the gear box "sped up" from the polish established on all the parts. This was about a half hour in each direction. We then inspected for any evidence of metal chips, and installed them in the robot.

We should get a day or two of testing by Monday. After some agressive testing, we will report the results.

The material is from McMaster and you can make these parts easily if you have access to a lathe, a mill, and a heat treating furnace. This approach to the problem is best described as Dr Joe's plan C. If you don't have this equipment, I would suggest that you head to a local machine shop that can heat treat with suitable material and the existing parts to copy with the modified square hole setup.

If I bought material just for this task, I would use 4340 steel and suitably adjusted hardening and tempering temperatures in order to get a little more strength while maintaining toughness.

Well, I would really use maraging steel from http://www.onlinemetals.com if I ordered material just for this, but I won't get into that.

Eugene

Re: Banebot 56mm gearbox - double D - RELOADED
 

Update on the A2 tool steel carrier plates:

After cutting them on the waterjet, finishing the pin holes with a 5/32" drill bit, and filing the double-D to be a close fit, but not a press fit, I tempered the steel today. Here was my process:

1. Heat at 950C (1742F) for 20 min.
2. Air cool (A2 is air-hardening tool steel) until warm enough to touch.
3. Temper immediately at 650C (1202F) for 2 hours. Air cool. Repeat temper for two hours.

The high tempering temperature brought the hardness down to a C40 on one plate and a C39 on the other. (Tensile strength around 182 ksi.) I am hoping that this won't be too brittle.

A2 holds tolerance well in heat treatment, so the press fit pin holes worked fine. The double-D was a bit tight, but after a bit of sanding they seemed to go on easy. One gearbox assembly went smoothly. Putting the two stages in first and then fitting in the shaft later is much easier than messing around with a press fit shaft and carrier. It ran smoothly with the motor, drawing about 2.5A. (Is this normal? Good? Bad?)

The second gearbox is still having alignment issues, binding slightly in particular positions. I think the carrier plate may need some more filing to get it on straight. Maybe a fresh look at it tomorrow morning will do the trick.

So it is indeed possible to make a working HRC40 carrier plate out of A2 tool steel. It's a nice steel, because it can cool slowly, not deforming much, and still harden. McMaster also carries 5/32" (4mm) stock, saving one machining step. But it is somewhat expensive and needs to be heat-treated to get to the right hardness, so it probably isn't the ultimate solution.

The most important thing I learned so far is that a press fit makes assembly (disassembly) and alignment VERY difficult, and so I wouldn't recommend it. If I cut more, I'll cut them exactly 9mmx12mm. If the plate can self-align in the motor, it will run much more smoothly. But your results may vary, of course.

For now, I think I'm done. As long as the second gearbox goes together okay and nothing breaks this weekend when we drive the heck out of it, I think I'll be happy. We are using 12:1, 1 CIM per side, so I don't think I need to make a sqare-hole version in anticipation of needing the harder shafts. But I might cut some just in case..

Re: Banebot 56mm gearbox - double D - RELOADED
 

We draw about 5 amps with two motors, so yeah, I'd say you're good there.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Agreed, we used a 36mm, 256:1 gearbox to reduce the speed of a FP motor for ball harvesting last year. Worked well... Then again it was used for ball harvesting (which put very little load on the motor) not lifting an arm.

If a solid solution cannot be found in the next couple of days I would recommend that teams planning on using the 56mm gearboxes to drive their robot should seriously consider the single speed AndyMark (http://andymark.biz) gearboxes. They're the closest thing to last years kit transmissions, in fact I believe they might even be lighter than the old kit transmissions. At $98 a piece these teams should ask themselves if a headache is worth $200 +shipping.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I don't have anything to throw in about the actual process here, but for us, and likley many other teams, it is far too late in build to just "drop in" different transmissions. Believe it or not, it would take far more time, effort, and money to modify our existing chassis to use the AMs than to fix the already-mounted BBs. We will be looking into hardening once a final plan is developed, as a mentor fortunately works at a brazing company.

Re: Banebot 56mm gearbox - double D - RELOADED
 

We got a chance to test our 56 mm banebots transmission solution
today, using 12:1 gearing and two cim motors on each transmission.
As noted in the post earlier in this thread, we made new plates and
axle shafts out of 4130 steel, using a square hole, and hardened in
an oil quench at 1600F followed by a temper at 800F. The 4130 is
what we have on hand for heat treated welded parts, we would have
used 4340 for this application (or maraging steel considering the risk
to the function of the robot) if we had bought the material specifically
for it.

Our test was a half hour of ramming the robot into a old tire positioned
against a wall at full power from a distance of a foot or two, back and
forth. The test was stopped when everyone got bored of it. The
transmissions are doing fine with no apparent extra lash, but we have
not yet pulled them apart for inspection. We will do that when time
permits, there isn't all that much time available in the last two weeks
of the build period as we have our share of other problems to solve.

Have fun,
Eugene

Re: Banebot 56mm gearbox - double D - RELOADED
 

What wheel size, tread material, and floor/ground?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Wedgetop conveyor belting. Wheel diameter was about
5 1/2 inches. The robot was operated on carpet for the test.
Chain drive from the gear box to the wheels was 1:1.

Eugene

Re: Banebot 56mm gearbox - double D - RELOADED
 

Our team is also using these 56mm gearboxes. Now I have been reading through the forums and I am scared now! I am afraid these gearboxes will fail. We have signs of the gearbox binding or jamming. What is the best and simplest way to prevent this?

I am afraid that it may break like the images people have posted. What can I do to prevent this? From what I soaked up from previous posts is add lubricant, support the CIM, and break them in.

Also I found gear dust, very small amounts of metal inside the gearbox. What should I do?

Now I heard harding this plate may prevent the problem of the double D breaking. The problem is we don't know how to harden the plates, and I doubt we have the time. Also if these gearboxes fail, we don't have the money to replace them. So what should we do?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Don't be scared. Those with experience in these kinds of issues are working on a solution. They realize they have two weeks.

Small amounts of metal dust are not unusual, nor cause for panic. If you want, clean out the internals of the gearbox and re-lubricate.

The plates themselves are of a material that cannot be hardened, so again, folks are working on this and hope to have a solution. NOT having a solution might be a serious problem, they understand, so just the existence of this thread should be very reassuring.
===

For those really in a panic:ahh: , go to a local machine shop and get a quote on making a shaft, 3:1 plate and 4:1 plate all with the square holes, from material that will be hardened to Rockwell C 23 - one set for each transmission you have. Install those and, the current thinking is, you should be good (or at least a LOT better) to go. If the price is reasonable, have spares made for Just In Case.

Don

Re: Banebot 56mm gearbox - double D - RELOADED
 

All of the things you mentioned (lubricant, breaking in, supporting the CIM) are helpful. I'm guessing you are using just one CIM in each gearbox. The data and evidence so far suggests that if you treat this setup right, it will quite possibly survive without modification. Joe Johnson and BaneBots are working on a solution for making harder carrier plates that doesn't involve the teams doing heat treating themselves.

I can tell you from my own experiences (we are also running 12:1, 1 CIM per gearbox) that if you notice binding and the gearbox gets hot while breaking it in for a half hour, you may want to take it apart an look for tight spots. This will give you a chance to look at the carrier plate too for any signs of wear and add lubricant. There are instructions available from the BaneBots website for how to relieve common problems, such as the motor pinion sticking out too far.

Another fix that seemed to help yesterday was sanding (with fine grit) and/or polishing the round lip on the bearing blocks that fits into the ring gear housing and the flat surface opposite the carrier plate on the bearing block. This seemed to help with alignment issues, and the motor current went down by half an amp or more.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Don't panic about the gearboxes... be aware, but don't panic. You are in the same boat as probably close to 1,000 other teams and there is absolutely no way this boat is going to sink.

We have had some experiences with the 56mm gearboxes and have identified two problems, both with assistance from this forum.

1) The "Double-D" bowtie problem, which this thread is primarily concerned about, and which... as previous posts indicate, can apparently be solved by remanufacturing the final stage carrier plate. Given the sheer number of these gearboxes in circulation, you can expect that FIRST and Banebots will be involved in this solution. As for now, you can drive and test your robot. You may (will?) experience increasing backlash as the bowtie forms, but that is a ductile failure that should cause no permanent harm to the transmission. When (if?) a new final stage carrier plate becomes available it will not take long to insert. These transmissions can be rebuilt very quickly and easily with one 2.5mm hex key.

2) The "mounting plate" (aka spacer) problem. There is some variation in the thickness of the mounting plates for the trannies. This is more likely the cause of the metal and grinding that you have experienced. We found that three (of our four) BB 56mm gearboxes experienced this problem. The cause seems to be that the tranny is "too tight" when all the screws are done up, and the spacer that fits on the CIM shaft rubs against the gearbox end of the motor... since the motor appears to be aluminum in this place, and the spacer steel... well, that is probably most of the metal dust. Check to see if the end of the CIM surrounding the motor shaft appears to be wearing away and this will confirm this problem. We found that putting the spacer (that goes between the CIM and the first gear) on the lathe and turning about .010 off one end, then slightly grinding the motor shaft down to match has cleared up this problem and resulted in four nice smooth running gearboxes. In retrospect, we should probably have done this before "breaking in" the CIM... as the breaking in process seems to consist mostly of wearing down the end of the CIM. If you have access to a lathe (or even a vise, a file, and a steady hand) you should be able to solve this problem fairly quickly.

I would like to point out, that these are not solutions or observations original to our team, but rather are based on helpful posts by many other CD posters.

We have also noticed one other thing to look out for if you are using the Banebots encoders... some of the transmissions seem to have a bit of end play in the driveshaft. We have observed this on one of our four trannies in particular. The end play was sufficent that the encoder disk would move in and out enough that it would at times rub against the sensors on the encoder. A serrated steel disc rubbing against plastic optical sensors means it didn't take long before we were working with one less encoder.... we are considering a few solutions for this problem, but have not tried one yet.

Any suggestions CD community?

Thanks to everyone who has been posting their experiences and the teams who are leading the way in testing re-manufactured carrier plates. It has been about a week since the bowtie problem was first noted here, I believe, and it sounds like a solution is well in the works. That is an amazingly fast response, and just one more reason why FIRST is first.

Jason

Re: Banebot 56mm gearbox - double D - RELOADED
 

About the pinion, sorry, I haven't taken apart the transmission, but what is it? Where is it? Are there any pdf's or files that talk about taking the transmission apart?

Re: Banebot 56mm gearbox - double D - RELOADED
 

I know this isn't a full solution, but I think there are some things you can do to make the gearboxes live longer, at least through a regional competition, without spending much money or needing exotic machining abilities.

First, make sure the end play is properly adjusted. There is a spacer that goes on the motor to space the gear into the motor the correct amount, this procedure will get that spacer to be the correct thickness. Support the gearbox housing, with the shaft down, and make sure the gearbox is not resting on the shaft or bearing. Use a depth measuring device such as the pin that sticks out the side of a dial caliper, and measure the depth of the first stage planet carrier plate in the gearbox. The place you need to measure is shown in the photo. Now measure the distance D on the drawing from the motor mounting plate, to the end of the gear. The gearbox measurement should be larger than the motor measurement. Subtract the two measurements, this is the end play on your motor/gearbox. I suggest that a desireable end play would be 0.005 - 0.010 inches (0.13 - 0.25 mm).

The fun part is adjusting the end play. If there is not enough, you could turn the spacer in a lathe or file it down to make it shorter, or you could add a shim between the motor mount plate and the gearbox. Paper would probably be sufficient if it only needs a little bit of shimming, normal paper is about 4 thousandths of an inch thick.

If there is too much end play, then you need to make the spacer thicker. You can't use paper for this task, as things are turning, so you need something that won't wear easily, such as nylon, or steel. You might see if you can find a thin flat steel washer, or make your own using "shim stock", which can be purchased at some old-fashioned automotive parts stores, or places such as MSC or McMaster-Carr. You can also buy "round shims" at McMaster-Carr and probably others. If you have access to a lathe you can make some extra spacers, and play around with machining them to the correct thickness. There are probably other relatively easy solutions I have not thought of, hopefully others will let us all know what they are when the figure them out.

There are some other gotchas on the end play issue, such that you should recheck it after you have run in the motor/gearboxes, and again after they have been in use on the robot for a while. There is some end play on the output end of the gearbox, because of how the bearings are mounted. If your drivetrain design pushes in on the output shaft, then you may have problems with binding or excessive wear, so try to make sure it is not doing that.

The next thing to make the gearboxes live is to understand that the problems with the carrier plate being damaged appear to be due to sudden direction change. Talk to your drivers, and tell them that any sudden acceleration of the robot, especially a sudden direction change, is essentially abuse of the robot. The gearboxes will live MUCH longer if when you need to change direction, you make sure to come to a complete stop, then gently accelerate in the other direction. Jamming the joystick from one end quickly to the other end of it's travel is an invitation to disaster.

One possible method of ensuring that the motors are started in a controlled way, would be to have the programming team put a limit on how fast the PWM outputs to the drive motor speed controllers increase. If they allow only a small change per unit time, then the gearboxes cannot be damaged by sudden direction reversals, even if the driver gets a bit exuberant (and I do realize how exciting the matches are!). Look into this, hopefully some of the programmers here can come up with some code to control motor acceleration rate.

I think if you take care of your Banebots gearboxes, you should be able to get them to survive the season. If some of you can try out these suggestions and then take the gearbox apart and see how much wear they have, it might put a lot of teams' minds at ease....

Re: Banebot 56mm gearbox - double D - RELOADED
 

http://www.banebots.com/docs/GP-56012-Assembly.pdf

That doesn't show the internals of the gearbox, but the post above by squirrel explains some other internal fixes well.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Can someone please confirm for me: The 3:1 carrier plate is used in 12:1 transmissions, the 4:1 plate in 16:1 transmissions. You need one or the other if you are going to have new carrier plates made, but not both.

Is that right?

The thought is to get a price quote from a local machine shop based on Dr. Joe's prints. I plan on getting the 3:1 carrier plates plus the shafts, all at RC40.

Thanks,
Don

Re: Banebot 56mm gearbox - double D - RELOADED
 

the 12:1 transmission uses a 4:1 first stage, and a 3:1 second stage. The 16:1 transmission uses two 4:1 stages. The first stage carrier plate has much less load on it than the second stage, so you don't need a new first stage plate.

If you decide to replace the vulnerable carrier, you need a new 3:1 second stage carrier made if you are using 12:1 transmissions.

Re: Banebot 56mm gearbox - double D - RELOADED
 

The following table provides comparison data for 1040, 4140 and 4340 steel, that makes it clear what the best choice is if you are concerned about part failure.

http://www.auto-ware.com/techref/materials.html

Re: Banebot 56mm gearbox - double D - RELOADED
 

For any team this should help to reduce some of the problems with the end plate tha are occurring, and really I think this is good practice regardless of what motors/transmissions you're using. If teams need help with this just ask, I know some teams (ours included) have been doing this for at least a few years.

Re: Banebot 56mm gearbox - double D - RELOADED
 

With reference to Dr. Brooks' table in the above post of various steel properties, what degree of hardness do we need in the gearbox plate? This will help us decide which metal to start with.

We have access to a waterjet and a computerized furnace, and hope to make some parts. Hopefully we can make several.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Somewhere earlier in the thread, Joe Johnson posted some target hardnesses for different situations:

1 CIM 12:1 or 16:1 - HRC23. Any harder and the shaft becomes the weak link. But this should be enough to handle the torque of one motor in cyclic loads.

2 CIM 12:1 or 16:1 - HRC40 on the carrier and the shaft for the worst-case scenarios. Any harder and the steel may be too brittle.

Also, there are drawings in the first post for a plate/shaft with a square hole/end instead of the double-D, which will help with the stress distribution.

Dr. Brooks' team has made some HRC40 plates and shafts out of 4130 and my team now has two made out of A2 tool steel. I think 4130 or similar is the more appropriate choice, since C40 is almost off the charts low for tool steel. I got it because McMaster carriers 5/32" (4mm) precision-ground stock. Other teams and BaneBots are in the process of making and testing new parts.

Re: Banebot 56mm gearbox - double D - RELOADED
 

just wanted to post something so I get notified on updates.

we are using the 2 CIM adapter setup and I am now VERY concerned about our robot.

Will keep my fingers crossed that a timely solution presents itself, otherwise....:ahh:

Re: Banebot 56mm gearbox - double D - RELOADED
 

Re: Banebot 56mm gearbox - double D - RELOADED
 

I certainly understand your concern, but I believe that you will be just fine.

#1 the failure is not instantenous, but rather works itself overtime. The rate that it fails is a function of robot design (heavier robots with grippier tires make things worse) and robot driving (repeated rapid changes increase the rate). There are many many robots out there that would never know there was any issue with these transmissions if they we did not tell them (even 2-CIM per side teams).

#2 the fialure only hurts the carrier, not the rest of the transmission. This will allow teams to drive as is and implement the solution when we finally get to that point. (we are working out the details -- stay tuned).

#3 while we are still working out the details of exactly what is need to address the problem, the early reports from teams that have implemented various bit of the plan have been very encouraging. Again, let me repeat that FIRST and Banebots are very much committed to working with teams to address this problem in a timely manner.

Stay tuned.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Joe - thanks for those words.

I have read through ALL of the posts and see that many people (with FAR more brain cells than I have in this area) are working on the problem and a re VERY motivated to come up with a reasonable solution.

Our robot is definately going to fall into the "heavy" category and, we are using the High Traction wheels from IFI along with a set of the Coolie-Dualie Wheels from AndyMark. We may consider adding some "software" to our program to limit the forward/backward transitions to try and prevent some of the potential for damage.

In the meantime, our team is going to at least talk about some Risk Mitigation strategies today and come up with a "Plan B".

Keep plugging away, am sure there are a LOT of teams all in the same boat.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Reading from Mil Spec MIL-H-6875H

4340 1550F soak for half hour, oil quench, 850F temper, tensile is 200-220 ksi
4130 1600F soak for half hour, oil quench, 850F temper, tensile is 160-170 ksi
4140 1600F soak for half hour, oil quench, 850F temper, tensile is 180-200 ksi

Seal the parts in a stainless bag, flushed with argon, that is easily cut with shears while glowing so you can drop the parts in the oil quickly without them cooling off in air before the dunk. Tempering cooler will increase strength, but as you approach 700F the parts become brittle. These strengths are way above the strength of the factory shaft. You should make both parts, and use a square hole, to get the full benefit of the improved materials/geometry.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Here's a really cool McMaster white paper on steel properties and heat treatment:

http://www.mcmaster.com/addlcontent/...p?doc=88645KAC

If that link doesn't work, search the catalog for: 88645KAC

Re: Banebot 56mm gearbox - double D - RELOADED
 

If I took out the CIM spacer cut it down to the right size to fit and cut down the CIM's shaft to be flush with the gear, and Lubricated it would this help prevent Binding and a risk of the plate breaking?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Probably not. This would help the gearbox and motor run smoother, but it will transmit torque as well or better than it did before, meaning the double-D could still deform over time.

Update on the tempered C40-hardness A2 tool steel carriers: We finally got around to re-mounting and testing today. The HS kids enjoyed the opportunity to do wheelies and driving it like crazy in a confined area. After about 5-10 minutes of driving, a sprocket bolt fell off (somebody forgot locktite) and everyone suddenly had to leave instead of fixing it.

I wouldn't call this definitively tested, but they didn't fracture and there is no backlash to be seen right now. More testing to come tomorrow.

Our drivetrain is 1 CIM, 12:1, going to a 6WD. See attached pic.

Edit: Yes, I know the shafts aren't well supported. O_o

Re: Banebot 56mm gearbox - double D - RELOADED
 

Funny thing is that it does run smoother and no signs of binding, yet (hopefully never). How much torque does it really take to backlash it and break it?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Yep, ours ran much more smoothly too after some tweaking. I was just saying that I think the alignment and spacing issues are separate from the double-D issues. Solving one won't fix the other.

An earlier estimate from Dr. Joe was that 350 in-lbf, in repeated, high-cylce loading was a safe estimate for the amount of torque the plate could see before a problem occurs.

Re: Banebot 56mm gearbox - double D - RELOADED
 

40N*M? thats a lot for our drive system. Our drive systems stall torque is 38N*M.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I know the best solution to the carrier plate is a new properly heat treated replacement, but could brazing the shaft and carrier together overcome the problem? This might help if the spacing issue agravates the carrier wipe out.
A good 16% silver brazing rod and the proper flux should penetrate well. What woud taking the carrier and shaft up to 1300 - 1400 F do to the hardness? Water quench after?

Re: Banebot 56mm gearbox - double D - RELOADED
 

While the brazing may well reduce impact loading by reducing the amount of space for "play" in the Double D, and could serve as an emergency fix, I would suggest holding off on doing it for the moment, if you can.

I would be concerned about getting proper alignment of the carrier plate while brazing... yes, it can be done, but if it is done wrong you are deeper in the hole.

I share your concern about hardening... or softening... of the shaft. You don't want to weaken the shaft, yet at the same time you don't want to make it brittle. While I can't say for sure whether the brazing is likely to affect the shaft, or whether quenching would re-harden it, I agree with you that this is an unknown of no small concern.

I would be concerned that since the braze material is softer than the steel of the carrier plate that it will deform under static load, leaving you no further ahead than you were before brazing.

If a replacement carrier plate made of hardened steel becomes available it will likely be machined to fit the double-d of the shaft... which is now brazed into the old carrier plate.

I am hoping (rather anxiously now...) that the next team update from FIRST will address an official response to this problem, and that the official response will include replacement final stage carrier plates that will be available to all teams. (I am basing this on Dr. Joe's comments that everyone at FIRST and Banebots is working hard to address this issue and the high respect I have for the FIRST organization... I have no inside knowledge on which to base this.)

So if you've got a spare transmission on which to test this fix, I'd say sure... go for it... and let us know how it works. It just might work out okay, after all. But if you can still test drive your robot, despite increasing backlash, and have no spares, then I would suggest perhaps waiting a day or two before trying this fix.

The optimal solution does seem to be in getting some proper carrier plates manufactured and distributed to teams so that the gearboxes can do the job that they were specified to do. It shouldn't be that hard, nor that expensive, particularly if it is a co-ordinated response for all teams.

Jason

Re: Banebot 56mm gearbox - double D - RELOADED
 

Perhaps you didn't see one of the earlier threads on this subject, where welding the two pieces together was discussed, or where making the shaft one piece was discussed. The shaft is 12mm at the DD joint and the bearings, and 1/2" (12.7mm) at the other end. So, you need to braze it with the shaft installed in the bearings and the end mounting block. I would hesitate to do that....the heat would probably be hard on the bearings! plus you can't disassemble it without reheating and melting the braze.

Re: Banebot 56mm gearbox - double D - RELOADED
 

If the carrier material is the proper hardness, I don't think that brazing will significantly improve the performance of the joint. The problem is not the impact from the slop in the joint but the impact of the robot's momentum vs the rotational inertia of the armature of the motor.

This is why grippy tires play such an important roll in making the joint open up. Without grippy tires, the force from the robot momentum is limited by tires slippage.

As to the solution, I don't know all the final details, but everything I have heard so far seems to be reasonable. I am sure that some folks will still complain, but I think that most level headed folks will be okay with the plan.

Joe J.

Re: Banebot 56mm gearbox - double D - RELOADED
 

I was at FIRST HQ over the weekend on a different matter and spoke with the person who is responsible for the testing being done there on this issue. They were very frustrated at the time it was taking to get the new "improved" parts delivered for what will be a much more rigorous round of testing. At that time, Sunday afternoon, the parts were somewhere in transit.

Assuming the parts were delivered yesterday, as expected, today would be earliest we could reasonably expect results. Depending on the test program, which was not elaborated on to me, it might be several days before results are ready for general release. One thing they do NOT want to do is release a fix that then does not work. That would be worse than the situation now. So they are taking the time to do it right.

Another thing that needs to be understood is the small crew FIRST has working on FRC. I was introducted to about five of them. That was the whole FRC staff. These people all have duties to perform that are related to the Regionals and are therefore time-critical. Somebody has to plan the loading of all the boxes for the trucks, make sure all the equipment gets loaded in the boxes, make sure the boxes are properly loaded into the truck, and make sure the truck leaves on time, among other things. These tasks were planned and people and other resources were allocated well in advance.

The current test program is an un-planned task. It is a very important task and FIRST is very concerned that it be accomplished successfully, but it is still something that they have to divert some of their limited resources to cover. This is also their busiest time of year and people, even robot people, need to sleep sometime. So in spite of everybody's best effort it may take some time to get this resolved.

The good news is that the failure mode is slow and progressive and the fix can be installed at a Regional if needed. That gives at least an extra two weeks to deliver a fix. (Obviously the parts would be considered COTS items and could therefore be purchased if needed during the interim between ship and competition)

So keep on building your robots, handle them gingerly during testing and watch out for the start of any failure behavior. Make sure your trannys are accessable and easily removable. If you do these things you should be OK in the long run.

Re: Banebot 56mm gearbox - double D - RELOADED
 

If I had to do something and had no machining capability, I'd be tempted to heat and quench the existing carrier in a very cold brine solution, one containing about a pound of salt per gallon of water. I might even add some Jet Dry or other type of surfactant (or some "water wetter") to ensure a very hard quench. (People used to use a lye solution, but that's a bit dangerous.) The idea is to raise the boiling point and reduce the tendency for the water to form vapor bubbles at the interface between the quenchant and the steel, thus ensuring maximum heat transfer rate.

It is my understanding from research that steels with as little as .20 to .25 percent carbon can still be hardened to as much as 36-37 Rc by this method. PLEASE DO NOT TRY THIS WITH STEELS CONTAINING MORE THAN .40 PERCENT CARBON. THEY WILL SHATTER.

Some people swear by the "superquench" formula containing some dishwasher soap. I found this to be of interest: http://paaba.net/WeekendMet.htm

Re: Banebot 56mm gearbox - double D - RELOADED
 

Team Update #9 is out. In it the Carrier plate is addressed. Currently BaneBots is in the process of manufacturing new parts. The method of distribution is being worked on.

Excerpt from Team Update #9
"...Replacement plates are currently being manufactured by BaneBots for all transmissions distributed to the FIRST community. These plates will be available and distributed to teams by BaneBots at no additional charge. We are currently working on a distribution method to insure that teams receive them promptly...."

Re: Banebot 56mm gearbox - double D - RELOADED
 

YEAH, good news indeed :-)

Re: Banebot 56mm gearbox - double D - RELOADED
 

Just for completeness, we got the results back from a friend with a material lab. His considered opinion is that it is either 1018 or 1020 steel. So it's virtually impossible to harden without carburizing, likely even with your superquench method.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Just the news we're hoping for!!! Because they still haven't figured out distribution method, I figure teams will be making this fix at their first comp. I mean for teams to receive them by the end of next week, they'd have to ship out next Monday. Can they even make a couple thousand plates in less than a week?

Re: Banebot 56mm gearbox - double D - RELOADED
 

Check your rule book. The FIX-IT WINDOW rules allow for teams to buy/manufacture spare parts and replacement parts. Since stronger carrier plates are obviously replacement parts, the ship deadline is obviously not as important. Especially considering this is an official FIRST replacement part. At worst, I can see FIRST distributing these at the regionals. I feel safe in saying that any team could replace both carrier plates in under an hour with a little help.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Still only gives teams until the Friday after ship, 2/23.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Keep reading.

That said, a competition-day switch wouldn't faze me in the least. I have empirical evidence that shows even a marketing major can tear a pair of these down and rebuild them in well under an hour with one allen key.

Re: Banebot 56mm gearbox - double D - RELOADED
 

1018 and 1020 steel can be hardened somewhat. The critical part is the rate of cooling, which is the reason for the salt and surfactants. The vapor barrier between the hot steel and the quenchant must be minimized. The Manganese content of the steel may also be a factor.

Another method is to use a high-pressure stream, as in the case of the process in U.S. patent # 3294599. This patent claims an increase in strength from 40-60,000 PSI to 155-250,000 PSI in steels having from .08 to .25 percent carbon content.

Re: Banebot 56mm gearbox - double D - RELOADED
 

It's not the time required to disassemble the tranny to replace the plate. It's the time required to disassemble everything, get to, and remove the tranny that is a concern. Considering the number of teams who will still be getting their robot working during the day before/during practice rounds at the regional, having them at the regional will definitely cut into their time to get finished.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Before I could tell them not to bother, our (lockheed) lab guys snuck a carrier plate in between shooting space shuttle parts. I cast another vote for 1010-1020 series.

They used an X-ray fluorescent (XRF) machine to determine the alloy:

http://en.wikipedia.org/wiki/X-ray_fluorescence

The reson you need to put detergent in your quenching liquid, and that you can firewalk, was discovered by this stern looking indiviual:

http://en.wikipedia.org/wiki/Leidenfrost

My edition (27) of machinery's handbook lists this series in the carburizing heat treatable alloys table at 900C (that is 1650F in christian units) follwed by plunge in water/brine with 170C/325F optional tempering. So if you want to do some mad science, and get yelled at by mom for experimenting in the kitchen (for the tempering anyhow), boldly go, the replacements are in the mail if you wreck them.

Travis

Re: Banebot 56mm gearbox - double D - RELOADED
 

My team is experiencing 2 issues with the BaneBots 56mm transmissions.

Here's our setup:

• 4 56mm 16:1 BB Transmisions
• 4 CIM motors
• Each motor/transmission combination directly drives an 8-inch wheel.

Here are our problems:

1. Carrier plate issue.
   This is well understood so I won't take up space here.
2. Brass dust from the planetary gears.
   We drove our robot around for about an hour and had no problems. After that first hour we noticed that our robot was "swerving" a bit. After about 2 hours, we noticed that 2 of our wheels were very reluctant to rotate. After reading this thread, we disassembled our BB transmissions and found a lot of brass dust inside. We cleaned out all of the grease (brass paste at this point) and re-lubricated the transmissions with all-purpose automotive chassis grease. This seemed to improve our situation. However, one of the transmissions rotates well, 2 rotate fairly well, and 1 is still pretty tight.

Our next steps:

1. Break in the transmissions (no-load duration test)
2. Check for more gear dust
3. Monitor current draw from the CIMs

Any advice would be greatly appreciated.
Thanks.

Editor's note: I (Joe J) have closed this thread, but the Second Stage Sun Seizing discussion continues here.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Did you find any obvious wear points on the planet gears to indicate where exactly the brass was coming from?

What stage was most of the brass in?

Do you have the black steel wear plate installed between the 2 motor adapter and the first stage gearset?

Re: Banebot 56mm gearbox - double D - RELOADED
 

If this does wind up being a Thursday fix at the regionals, teams should prepare by making sure that they have a process for getting out the gearboxes. Something to press the pins out will be useful too...a table top drill press can probably work. And don't rush the job...it's better to spend an hour or two making sure the alignment is good and the gearboxes are broken in than to find out on Saturday that you have nothing but rounded off brass cylinders where your planets used to be.

That being said, if you are a team using 12:1, 1 CIM (like many rookies, I'd imagine), have been driving around for a while and haven't notice any major backlash problems, and have taken appropriate software measures to reduce shock loading, would you still repair these on Thursday at a regional? I'm not sure that I would.

Re: Banebot 56mm gearbox - double D - RELOADED
 

If the new plates don't have pins in them, you can quickly remove the pins from the old plate with a 1/8" pin punch (or a 16d nail with the point ground off), a hammer, and a small socket from a socket wrench set.

Installing them can be done with a vise or the hammer, but it would be nice to have a guide, such as a chunk of 1/4" or so thick aluminum with a slightly oversize 4mm hole in it, drilled as close to 90 degrees as you can get it.

Re: Banebot 56mm gearbox - double D - RELOADED
 

Concerning the pins. The new harder carriers from Banebots will have pins installed in them so removing them should not be required.

On another note, I am going to close this thread and start a new one here:

Banebot 56mm gearbox - double D - V3 - It's Show Time.

I will also start a new thread about the second stage sun siezing on the output shaft.

Joe J.