Banebot Transmission Issues

[Karthik]

Teams,

Just a warning to all, we recently purchased a 256:1 42mm Banebot transmission, and have had many difficulties. It turns out that the quality of these transmissions leaves much to be desired. The output shaft is attached to the last stage of planet gears via a plate with two flats cut in it. The thickness of this steel plate is insufficient and to worsen matters the steel is rather soft. We managed to round the hole in the plate after a mere two minutes of use. If teams wish to use these gearboxes, I strongly recommend modifying the internals to better transfer the torque via the shaft. In fact, The Team 1114 design team and I, strongly discourage teams from using these 42 mm gearboxes in any reduction above the 36:1.

As always, your mileage may vary. Good luck.

[Joel J]

Really didn't want to hear that :(. But I guess its good to know now, rather than later.

[Kevin Sevcik]

I'll second Joel J. Any recommendations for a fix for the trannies?

[Karthik]

I'll second Joel J. Any recommendations for a fix for the trannies?

We welded the output shaft to the aforementioned plate. It's holding up for the time being, no idea what the longevity of this solution is.

[Kevin Sevcik]

We're using ours in a pretty low-cycle application. We'll go with that and get some spares for backups now. Thanks again for the info before we trashed ours too.

[jgannon]

Karthik, any idea if this issue exists in the 36mm box too?

[Gamer930]

Be careful with the 56mm 12:1 gearboxes also. . . These are the ones made to run with the CIMs

On one gearbox the CIM Motor Shaft was bottom out in the gear box and we had to fabricate a .015 shim because it was running very rough and grinding. . . Seems decent now. . .

Now Thursday night we had problems with our other gearbox. . . We were running it and all the sudden it locked up. . . We took it all apart and there were bits of metal shavings mixed with the grease. . On the output shaft there is a gear that is loosely press fit and we found that when they fabricated the gear there must have been a small burr on the gear and when they press it onto the shaft it made a good indentation and created a circular groove on the shaft that it finally froze up. We washed up all the gears. Took some fine paper to the gear and shaft and regreased it. . . Seems to run fine now. . .

Just a word of caution. . . Highly recommend to take them apart immediately if you hear something not right and after you use it for a while.

[Karthik]

Karthik, any idea if this issue exists in the 36mm box too?

Yup, we just pulled apart a 36mm and noticed the same issue. Soft, thin plate, hard shaft going through it. It may not be as much of an issue with the less powerful Banebots motor, but it looks iffy.

Another issue with these gearboxes is that they use an unknown type of screw to hold the face plate on. We had to grind down slot screwdriver to make it fit. Frankly these transmissions seem like more trouble than they're worth. Definitely not as robust as we had hoped.

[cdfps]

We put both banebot transmissions on a little test platform robot (20lbs?) that we were using for coding while the robot was being built.

We were getting some strange behavior with one of the transmissions where it would periodically develop a tight spot. We ran in the transmission with an old CIM for about 10min with a battery and no load. No difference. We disassembled it and flushed it. There were little silver metal chips in the flushing.

We then ran it in backwards with a dewalt drill on the output shaft for a few minutes with no load and mineral spirits for a lubricant. After this, we flushed it again and blew it out lubed and reassembled it. It ran fine after this.

If you do decide to flush it, remember that the solvent will get into the output shaft bearings.

[Madison]

Karthik,

Can you say how much load, if any, the gearbox was under when you rounded the flats?

We recently ordered two of these for infrequent, momentary use and I'm worried that we'll tax them too much and find ourselves in a bad situation.

Thanks for the warning.

[Viper37]

Today myself, 3 students, and two Mechanical Engineer's spent 6 hours reworking the internals of the Banebot tranny's. We had to grind, file, hack, and rub these things to finally get the inner pins and screws from rubbing other parts of the transmission internals. We also had to re-tap some of the screw holes as some came stripped out FROM THE FACTORY.

An off the shelf part is supposed to go together without any trouble, and work. The Banebots transmissions are the farthest thing from that.

And for what we paid for them, it is totally unacceptable.

In my own opinion, they are a large step backwards from what we have been using the last few years.

[Karthik]

Karthik,

Can you say how much load, if any, the gearbox was under when you rounded the flats?

We recently ordered two of these for infrequent, momentary use and I'm worried that we'll tax them too much and find ourselves in a bad situation.

Thanks for the warning.

Madison,

We were moving a load of about 5 foot-pounds of torque, while shockloading by changing directions. So, I would call this a small to moderate load.

Also, our solution of welding the shaft to the plate has failed twice, we've re-welded it a third time. Since each piece is a different type of steel, it's just not working well. Also, you have to weld with the bearings in place and you're restricted to welding from one side.

In synopsis, these gearboxes are less than suitable. That's Karthik putting it mildly.

[sanddrag]

We assembled one of our Dual CIM kits today. As stated in the instructions, the key will need to be filed down to fit further back in the key slot for everything to fit together right. We put a wheel on the shaft and backdrove it. It feels nice. The motors haven't been run yet. Will update once we do. As a note, the dual motor kit adds only about 1/16" to the overall length of the gearbox assembly.

[Jack Jones]

Madison,

We were moving a load of about 5 foot-pounds of torque, while shockloading by changing directions. So, I would call this a small to moderate load.

In synopsis, these gearboxes are less than suitable. That's Karthik putting it mildly.

I'd say that's a small load. It's the equivalent of a 1 lb load on a 36" 1 lb arm - held horizontal. Who wouldn't dream of a achieving a 1 lb arm; and who wouldn't want to reach more than three feet?

Mid way thru the build is no time to be finding this out. If we bench tested every component, we'd still be three weeks into the build, with nothing designed.

We go into this knowing it's about teaching engineering problem solving; but it should not be about solving the supplier's engineering problems. I want to know if they plan on paying for our services!

Happy low scoring everyone!

[MrForbes]

The quick reversing of direction can be avoided with careful programming and control setup, and I have a feeling that this is much more likely the cause of the problem than the 5 ft lbs of torque.

It sure is nice to have this early failure report, so we know to be careful with the BB gearmotors, and have contingency plans in mind using either the Globe or window motors.

[Tom Bottiglieri]

Karthik,

Thanks for backing up our hesitation to use these gearboxes. It seems like everyone who's used these things before thinks they are garbage..

[Gdeaver]

Planetary gear boxes in similar form factor to the banes transmissions are used for motion control in industrial applications. They are extremely robust and typically last for years running under heavy continuous loads. The problem is this quality costs some serious money. I believe the entry price for the small ones is around 300$. Beyond what most teams want to invest in transmissions. The banesbot trans are affordable and something has to be given up to get in their price range. The first time I got my hands on the 56 trans I took it apart all the way. After that inspection, our team made the decision to spend part of our minuscule budget on 2 Andy mark transmissions. I don't think our team will regret it. I've seen some team with monster traction wheels and the banesbot transmissions. They are setting them selves up for problems. Used with the KOP wheel may be acceptable.

We may want precision planetary gear heads with electronically commuted brushless dc motors and fully programmable intelligent speed controllers and a micro itx robot controller with a high level development environment. But, our budgets allow for brushed dc motors, spur gear boxes, dumb speed controllers, PIC based microcontroller robot controller, and easy-c - mplab development environment.

[Joe Johnson]

The quick reversing of direction can be avoided with careful programming and control setup, and I have a feeling that this is much more likely the cause of the problem than the 5 ft lbs of torque.

It sure is nice to have this early failure report, so we know to be careful with the BB gearmotors, and have contingency plans in mind using either the Globe or window motors.

The last joint double D* on the Banebots 56mm Trans has given me heartburn since kickoff when the joint first caught my attention (actually I am worried about the same joint on the 42mm & 36mm too but only at the higher ratio -- read more here (http://www.chiefdelphi.com/forums/showpost.php?p=566658&postcount=14)).

I have done some calculations, some FEA's and finally this past week some tests. I am still working on my "final report" but here is my initial report. The joint fails under static loading when the input to the 12:1 gearbox is about 3X the 12V stall torque of the CIM motor. The joint fails under back and forth cycling at about 2X CIMstall.

From my point of view, the joint as shipped is not strong enough to be used with the 2 CIM adaptor from BB. It seems like it should be okay for use with 1 CIM with the 12:1 ratio but I am not sure because I usually estimate the dynamic loading to be twice the static loading. That would make the 12:1 gearbox right on the edge of acceptable. BUT, in this case, with teams rapidly switching from forward to reverse, I am not sure that a factor of 2X is enough.

The 56mm carrier plates are pretty soft. They are Rockwell A hardness of about 46 -- corresponding to a yield stress of about 64,000psi. It is not too hard to get a material with a yield stress of about 2-3X that number.

I think that that is probably where I am going to go with my recommendation. More to come.

Joe J.

*In many ways, double D's are not very effective torque transmitters, they cause stress risers and concentrate stresses on small sections of the joint. Splines are better because the distribute the stress to more material but not as easy to make.

[MrForbes]

Thanks for the analysis....I was referring to applications for the small Banbots gearmotors, not the 56mm version. Manipulators can be set up to have gradual acceleration, there should not be much requirement for quick back-and-forth motion, hopefully.

I agree that in driving applications the back-and-forth motion is pretty much unavoidable, so your single CIM per transmission recommendation makes good sense.

[JB987]

We were going to use a FP with a BB 42mm, 256:1 mated by chain with an additional 6:1 reduction to lift our arm (less than 3 lbs.)...our prototype has worked well but??? Would addition of gas spring reduce some of the shock and help us reduce our concern over these BB's...or should we start over?

[MrForbes]

we were planning on 8:1 chain with a 64:1 or 128:1 BB gearbox, and either the BB motor or the weak Mabuchi motor. Arm weight is similar to yours. We are planning on using a gas spring to take most of the weight of the arm.....and we are also planning on being able to start over and put a window motor or two on it to replace the gas spring and BB stuff if it doesn't work out.

[Jonathan Norris]

Now you just had to scare me Karthik... We ordered a pair of these early last week and have yet to receive them. With our troubles last year of using the FP in the 36mm gearbox's made for only a RS-385 motor under a low load application, I should have expected this. I was hoping these larger gearbox's would be able to handle the power of a FP motor. We will do some testing when we get ours in and see what we come up with... but now I am scared of these gearbox's... :ahh:

[Joe Johnson]

I am not saying teams should panic. I believe the BB transmissions are still a great bit of engineering. BUT, like all things they have limits.

I believe that the higher ratios are even useful, but more for speed reduction not torque increase. The output joint is the same for every ratio. If the torque gets too high it will break that joint.

Now to your questions:
Will a gas strut or other counter balance help? Yes it can but it is not a panacea. Counter balance is just flat out a good idea. Teams should do that regardless of what motors they choose.

Should you toss out the BB design and start over with a window motor? This is a tough question. The window motors are great motors too but they only have about 20W of power available. If you are doing some significant work with the motor, you will have to do it about 1/5 as fast with a window motor than with a BB motor. If you are using the higher ratio but you never stall the motor you are probably going to be just fine (try to limit impact loading if you can).

In rough numbers, I project that the 42mm gearbox will fail with repeated cycling loads of +/-350in-lbs. I project that the 36mm gearbox will fail with repeated cycling loads of +/-100in-lbs. If you can design your mechanism to keep your loads below these (with a safety margin that lets you sleep at night), then I think you should be okay.

Joe J.

[MrForbes]

Thanks again, you have pretty much mirrored my thoughts.

[ZZII 527]

Thanks for the warnings everyone. We have an FP motor with 42mm, 256:1 BB gearbox installed on our arm and an additional 7.2:1 chain reduction. So far, there have been no problems, but we are definitely going to look at the internals tomorrow.

I think many people have said it already: impulsive loading is the killer. One thing I can think of that might make a big difference: chain backlash. If on a direction reversal, your mechanism has significant momentum before the chain engages, the stresses will be enormous. Preloading your mechanism so that the chain is always in tension is always a good idea, but in light of the new gearbox info I think it will be even more important.

[DonRotolo]

Boy am I glad that we chose to use four KOP trannies instead of two with our 4 CIMs in the drivetrain. We also ran in each motor/trans combination without load for a few hours - they definitely loosened up after that and drew nearly half the current of when we first started.

Our design is such that a change now would be nearly impossible, so we're going with the KOP trannies - but we might just disassemble them, clean them out and refresh the grease.

The small 64:1 trans will be sued for a light load, but we ran that in as well.

Counterbalance was not somehting we considered, but in retrospect it should've been obvious - thanks Joe J for reminding us.

Don

[CrosbyAR]

Thanks all for warning everyone. Now everyone can spend time preemtively strengthening and modifying untill finding out later that we trashed perhaps an important component.

-Alex

[Joe Johnson]

One think I should have mentioned in my "DON'T PANIC" message above is that if you designed the gear ratio of your arm/mechanism right in the first place, you are probably never going to see any problems.

I have recommended that teams design the ratio such that the highest "normal" load the arm is expected to put on the motor would be 1/5 to 1/4 of the stall torque. This is good practice for a lot of reasons, but to my usual reasons I can now add one more: The Banebot Transmission will not see anything like the stall torque of the motor (assuming your don't run your arm into end stops or the ground or whatever).

For what it's worth.

Joe J.

[MrForbes]

This is good practice for a lot of reasons, but to my usual reasons I can now add one more: The Banebot Transmission will not see anything like the stall torque of the motor (assuming your don't run your arm into end stops or the ground or whatever).

limit switches are a good thing!

[Joel J]

One think I should have mentioned in my "DON'T PANIC" message above is that if you designed the gear ratio of your arm/mechanism right in the first place, you are probably never going to see any problems.

I have recommended that teams design the ratio such that the highest "normal" load the arm is expected to put on the motor would be 1/5 to 1/4 of the stall torque. This is good practice for a lot of reasons, but to my usual reasons I can now add one more: The Banebot Transmission will not see anything like the stall torque of the motor (assuming your don't run your arm into end stops or the ground or whatever).

For what it's worth.

Joe J.
I don't understand this.. you mean a Don't Panic for the fisher price, or for the BaneBots?

[sanddrag]

While we're on the topic, I'll write out our notes about the big planetaries (included in the KOP) and the dual motor adapters. The "step key" included with the dual motor kit was about 1/16" too long. Also, While it does keep them on, I'm not fond of the pointed set screws in the shaft collars. Also, the screws that hold the planetary body onto the backplate seem weak We broke one. The gears are alright. One of them had a slight bind and is pretty noisy. Not sure where the noise is coming from. When we first ran them, we drew 7.5 amps (at 12V) between two motors. After 15 minutes or so, that was down to 5 amps (for the both).

Use blue loctite on everything.

[Ben Piecuch]

Whoa, let me get a grip on what you're saying here Joe.

You're saying that the FIRST Supplied Kit gearbox, the 56mm, small CIM, primary drive 12:1 ratio gearbox is barely adequate (about 2x factor of safety) for a single CIM install under cyclic loading. Yet, FIRST and Banebots offer a 2x CIM adapter for use in these exact transmissions? Doesn't this 2x CIM adapter effectively reduce my factor of safety on that double-D to 1x?
(I won't even get into the gear change option that brings this gearbox to a 16:1 ratio...)

Is this a good thing? Am I supposed to feel confident in the fact that FIRST and Banebots have given us a product to hang ourselves with? And, to discover this at week 3 into our build? I'm a little disturbed here!

I can understand doing my own Due Diligence on a COTS part that I purchased for my robot. But I should't expect to have to do the same to a FIRST supplied and mechanically approved part(s.) Correctly me if I'm wrong here, Joe. (Please...)

BEN

[Dan Petrovic]

Is there any easy way to avoid this problem?

Such as supporting the drive shaft on both sides? I already knew that sideloads are never good for planetary gearboxes, but could they really ruin them like this?

[Rosiebotboss]

Whoa, let me get a grip on what you're saying here Joe.

You're saying that the FIRST Supplied Kit gearbox, the 56mm, small CIM, primary drive 12:1 ratio gearbox is barely adequate (about 2x factor of safety) for a single CIM install under cyclic loading. Yet, FIRST and Banebots offer a 2x CIM adapter for use in these exact transmissions? Doesn't this 2x CIM adapter effectively reduce my factor of safety on that double-D to 1x?
(I won't even get into the gear change option that brings this gearbox to a 16:1 ratio...)

Is this a good thing? Am I supposed to feel confident in the fact that FIRST and Banebots have given us a product to hang ourselves with? And, to discover this at week 3 into our build? I'm a little disturbed here!

I can understand doing my own Due Diligence on a COTS part that I purchased for my robot. But I should't expect to have to do the same to a FIRST supplied and mechanically approved part(s.) Correctly me if I'm wrong here, Joe. (Please...)

BEN

Ben and Joe,

You're both making me nervous. We are in the same boat. Having trusted FIRST to do some of the "due diligence" for us, we are using the 2 into 1 adaptor as well.
I do not have any experience with the set up yet as we have not powered up the drive train yet. Although, Ben, check the run out of the 2 spur gears that mesh the CIMs into the BB 'top hat'. One of the sets out of three we bought is out by a lot, probably 5-10 degrees. Too much for my taste, BB has an email to answer.

[dtengineering]

While the possible weakness in the 56mm gearboxes leaves me with some concern, the "don't stall the little gearboxes" warning was made last year.

http://www.chiefdelphi.com/forums/showthread.php?t=41335&highlight=banebots

In the right application, with proper design the small BB transmissions work great. We used a 5:1 reduction running off an FP on our shooter last year with no problems... and have a couple 256:1 ones sitting on the shelf waiting for a job to come along for them. Since they will run off FP's, which let out the "magic smoke" pretty quickly as they approach stall, we try to keep the FP's down to 10A or less and within the torque limits.

I am sure that as I type, however, there are people working on clarifying any problems with the 56mm gear box and developing a solution.

I'll keep my fingers crossed,

Jason

[Joe Johnson]

Many folks imagine that FIRST has more resources that they really have. As a practical matter, there is nobody in Manchester with team experience. There are great people working for FIRST, but they just don't have the team experience.

The 56mm Banebot transmission was designed specifically for FIRST. Banebots asked me to help them with the requirements, which I gladly did. At this point, I wish I would have spent more time analizing the gearbox. It was not until after the kickoff (when I saw the picture of the 4:1 gearstage from Banebots' website that allows the 56mm gearbox to convert to 16:1) that the double D joint came to my attention. I should have noticed it sooner, but it just didn't come to my mind.

FIRST insisted on the 2 motor solution. I was not a big fan of it, but I did not oppose it either. After seeing the double D joint, I was very worried.

Seeing a picture of a FIRST test mule made me think that perhaps FIRST did not do enough testing. The picture has been removed. For those who did not see it, it had a long unsupported shaft that simply could not have stalled 2 CIM motors.

Initial calculations did not provide comforting answers. I have spent 3 weeks getting the data I need to make a reasonable recommendation. Yelling the sky is falling when it is only an acorn is just as damaging to FIRST as failing kit gearboxes.

What I still don't know is what is the dynamic load that a single motor CIM gearbox with 12:1 ratio. We really need someone to build up a 120lbs test mule and just cycle it Full forward, full reverse for about 500 cycles and then open the gearboxes up to see how much the double d had turned into a bow tie*. This is a big question. Is this just a problem for the 2 motor CIM adaptor or is it a problem that is more widespread. At this point, we don't know.

The fix is not that hard, but it is not free either.

As to whether we should have caught this earlier, yes, I believe we should have. But, mistakes are part of the human condition. Me, FIRST, Banebots, the subcontractor that builds the parts, there is plenty of blame to go around.

Right now, we need to understand the extent of the problem and come up with the best solution possible.

Joe J.

* see the attached photo for an idea of what happens to the joint. This was done with 100 cycles of +/-40in-lbs torque (approx. 2 CIMs). During the test, it was clear that each cycle is opening up the joint. I started with about 180 degrees of backlash at the input to the transmission. By the 100th cycle, the doulbe d had opened to the bowtie shown in the photo and the backlash was over 270 degrees.

[MrForbes]

To help those of us who have not disassembled one of these gearboxes understand the situation, am I correct in assuming the output shaft has two flats on it, which fit into the Double D hole?

[Joe Johnson]

To help those of us who have not disassembled one of these gearboxes understand the situation, am I correct in assuming the output shaft has two flats on it, which fit into the Double D hole?

Yes, see photo below.

The shaft is essentially 2X as hard as the carrier. I think the easiest fix will be to get harder carriers made.

Joe J.

[Kevin Sevcik]

Joe,

What are the odds of getting a cad drawing of the carrier(s) to facilitate getting new ones EDMed or otherwise fabricated? Seems to me that enough teams are facing this issue that going in together on an order from eMachineshop or an EDM house would be fairly economical.

[NeedMoreEngines]

Well, I've been reading through this thread, and I'm about to throw up.

We bought the 2-CIM adaptor for the 56mm planetaries.
We bought the 16:1 conversion kits.

Somewhere, some mechanical engineer reading this post is laughing his head off.

We've basically done what everyone has been saying NOT to do.

What still bothers me is this:
Why would FIRST supply us with products that clearly were not properly engineered? Or, look at it this way. Maybe these things are substantial. FIRST usually does things the right way, wouldn't they have faith in the company that is supplying such a critical component in the KOP?

I...I don't know what to say. I am at a toal loss for words. I want to have faith in the 56mm's, but everyone is basically saying "ehh...notsomuch!"

[Joe Johnson]

Well, I've been reading through this thread, and I'm about to throw up.

We bought the 2-CIM adaptor for the 56mm planetaries.
We bought the 16:1 conversion kits.

Somewhere, some mechanical engineer reading this post is laughing his head off.

We've basically done what everyone has been saying NOT to do.

What still bothers me is this:
Why would FIRST supply us with products that clearly were not properly engineered? Or, look at it this way. Maybe these things are substantial. FIRST usually does things the right way, wouldn't they have faith in the company that is supplying such a critical component in the KOP?

I...I don't know what to say. I am at a toal loss for words. I want to have faith in the 56mm's, but everyone is basically saying "ehh...notsomuch!"

I cannot disagree with you more strongly.

It is not clear at all that we will see failures in the field of this joint.

Looking at the design, my gut told me that perhaps there might be a problem. I have done quite a lot of work to try to get the answer to the questions.

Again, you image that FIRST has a Great Oz working behind the scenes to ensure that there is never a mistake made. Trust me, there is no Great Oz. There are only frail human beings trying their best to get great things in the KOP without breaking the bank.

Now back to the problem at hand. Contrary to my initial gut feeling, my analysis up to this point leads me to believe that if the carriers were hardened to the same spec as the shaft, the gearbox will likely perform without failures, even for the 2 CIM + 16:1 set up. This is a pretty straightforward fix that should not cause an undue hardship on any team.

Again, the big unknow is the dynamic loading we expect. Is there a team availalble that can quickly adapt a chassis as a test buck for me? I want to do 4 tests each with a 120lbs robot, 500 cycles of
1) apply full forward,
2) reach full speed forward,
3) apply full reverse,
4) reach full speed in reverse
5) repeat

Test 1: 12:1 gearbox 1 CIM per side
Test 2: 12:1 gearbox W/2 CIM adaptor
Test 3: 16:1 gearbox 1 CIM per side
Test 4: 16:1 gearbox W/2 CIM adaptor

The motors/gearboxes needed to do these tests will be provided.

Are there any takers? PM me ASAP.

Joe J.

[Mark McLeod]

For a controlled test I'd think you'd want to put the test article in an enclosed track and let the RC run it back and forth autonomously.

Ramp up/down or jump right to full forward and immediately switch to full reverse? Could also run a variety of both to simulate different driver styles.

We can do that for you if you don't get a closer volunteer team. We have spare kitbots.

[Paul Copioli]

O.K. I have kept quiet long enough.

The bottom line is that FIRST had a solution for the kit drive train that could also be used for an arm. They used it for two years with the only reported failures being from teams who did not lubricate the gearbox. It was designed and TESTED before it was placed in the kit. A 120 lb. prototype mule was created, beat against a wall, durability tested and shipped to Manchester in August of 2004 so they could do more testing. It was already in the kit and no more work had to be done.

The Banebot solution was a cost down effort by FIRST, plain and simple. This is O.K., but testing needed to be completed.

My question is why wasn't the same rigor a MINIMUM requirement for the BaneBots solution? If this was not tested on an actual robot before delivery to FIRST, then that is a huge oversight ... HUGE!

Now Dr. Joe,

You and I agree about 99.5% on things engineering, but you and I are polar opposites on this one. You made this comment:

I believe that the higher ratios are even useful, but more for speed reduction not torque increase. The output joint is the same for every ratio. If the torque gets too high it will break that joint.

C'mon. You get the torque increase as a result of the increased ratio. It is there whether you want it or not. While you can design your arm to not need it it will always have the ability. If your arm gets stuck, wedged, etc. then the motor will output that torque and you will have almost nothing to say about it. Gearboxes must be designed so the motor is the weak link. If you are reducing the FP (or Banebot) motor to get to a reasonable speed, then you better design the gearbox to handle the torque.

If BB offers a 256:1 ratio that is meant for a specific motor, then it better be able to handle the torque. If they offer a conversion kit to add a second CIM motor, then the gearbox better be able to handle the maximum possible torque the CIM motors can output.

If the gearboxes are not designed this way, then we will have a lot of robots that can make a perfect circle with their drive base.

I am now officially worried about teams using the new kit transmission with 2 motors. My calculations do'nt look good ....

-Paul

[Dad1279]

Sorry Mike, although I understand your frustration, there will always be minor setbacks in life. A valuable lesson can be learned from this group working together to arrive at a solution. Remember, until 2 years ago, we didn't even get a frame or transmission in the kit.

Joe, you have a PM. Team 1279 has the transmission pieces available, and a prior year robot that we should be able to use as a test bed.

[Joe Johnson]

O.K. I have kept quiet long enough.

snip

The Banebot solution was a cost down effort by FIRST, plain and simple. This is O.K., but testing needed to be completed.

My question is why wasn't the same rigor a MINIMUM requirement for the BaneBots solution? If this was not tested on an actual robot before delivery to FIRST, then that is a huge oversight ... HUGE!

snip

If the gearboxes are not designed this way, then we will have a lot of robots that can make a perfect circle with their drive base.

I am now officially worried about teams using the new kit transmission with 2 motors. My calculations do'nt look good ....

-Paul

You have some good points. I am not happy that this is where the world ended up. There were supposed to be testing done. In retrospect, it was not enough. There is plenty of room for blame and finger pointing.

Believe me, I realize the damage this does to FIRST.

Me and others are trying to work out a solution.

Joe J.

[Dan Richardson]

Well this is a big, costly issue here. We are at the beginning of week 4 with a significant chance that drivetrains and manipulators will be failing cross the country. It is unfortunate that this problem has come around and who's fault it is, is truely unimportant.

What we need to do is solve the problem, thats what we are here for anyways. Its always been that way, and for the rest of your life in engineering always will be this way.

I thank Dr. Joe for his hard work to figure out the issue, and it is unfortunate that they switched from Paul's kit bot transmission but the switch was made so lets figure out something here.

I know the changes aren't "hard" but one of the issues I fear is the teams who are buying these gearboxes in the first place are not the most mechanically enabled. It is extremely likely that a majority of the teams who have purchased these, don't have the resources nor the required experience to change them.

Without any testing equipment of my own to verify the quality, I'm pretty much in prayer these transmissions don't fail on our manipulator. I won't even find this out until the early weekend. By then, we could be in significant trouble, but I'm still working towards a solution, and in the process would like to help figure out an easy way for teams to remedy the situation.

For example petitioning FIRST to bend the rules and allow FRC 2006 transmissions that Paul designed. Or perhaps come up with a unified design modifying the exsisting gearboxes such that failure will not occur.

I offer my help to work towards a solution, we all realise there is a potential problem, so lets all work towards the solution. The complaining should be avoided, and I appreciate those who are already working hard.

[Daniel_LaFleur]

Joe,

I am not a mechanical engineer, but I am the only engineering support my team has.

Our team has a 4 wheel drive skid steer (tank steering) system with 1 cim and 1 56mm transmission with the 16:1 change kit on each wheel. We are chaining the front and rear wheels together to avoid loss of power should a wheel be lifted off the floor.

Considering this is our drive train and the that we will be playing a good bit of defense (shock through the system), How concerned should I be with these transmissions and what can I do to correct the issue.

If we were to fabricate a new carrier, what sort of material would be sufficient? and can drawings be made available?

[Joe Johnson]

I am closing this and several other threads. Please continue the discussion on the following thread:

Banebot 56mm Gearbox -- Double D related (http://www.chiefdelphi.com/forums/showthread.php?threadid=53007)

Joe J.