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: