Take the "Bane" out of your Banebot P60s - Solution to Banebot P60 Weaknesses

[Kevin Sevcik]

Originally Posted by Jonathan Norris

- with that high of a planetary reduction, the loads on last couple stages are pretty significant, to the point where I don't think those mild steel planetary gears will last very long.
- I would also be very concerned with stage plates in the last couple stages, the pins that the planetary gears rotate on are only press fit into the mild steel and have been known to come loose and destroy the gearboxes.

Point of order. The gears are definitely mild steel, but the ring gear is aluminum and likely to fail first.
Also, the carrier plates are definitely NOT mild steel. The guys that can run our pmi gun are out of office this week, but I had a scrap carrier plate to play with. 20 minutes, a butane soldering iron, and a cup of water took the carrier plate from 22 HRC to 40+ HRC. Definitely not a mild steel.

[sanddrag]

Originally Posted by Kevin Sevcik

20 minutes, a butane soldering iron, and a cup of water took the carrier plate from 22 HRC to 40+ HRC. Definitely not a mild steel.

Now THIS is some good information. Did it warp or deform at all to where it would become unusable? I bet a map gas or oxy-map torch would be able to get it up nice and glowing in a bit less time. I totally wish I had a spare one to attempt making a bulletproof P60 with some mods.

[Kevin Sevcik]

Didn't bother measuring it, but completely subjective testing in a P60 suggests no significant warping. It felt slightly rougher than a virgin one, but my hardened plate was already slightly bowtied and deformed from the above mentioned shocks.
Also, 20 minutes encompassed the whole heat treatment, including a 5ish minute soak at something above 1550F/bright red. Don't be knockin' my butane iron/torch.

Before anyone tries this for realsies, I'd recommend a little more research on someone's part. Possibly mine. I'd like to know the actual alloy so I can figure out a real heat treat procedure for it, including a temper. I said 40+ HRC for a reason. I tested multiple locations on the thing and my haphazard heat treat gave me hardnesses ranging from 40 to 60. This does not inspire confidence, and I'd really recommend a good tempering to relieve some of those stresses and reduce the chances of fracturing as your exciting new failure mode. Brittle fracture is obviously an even worse failure mode, since you've moved from a gradual semi-predictable failure to an instant an catastrophic one.

Finally, you're going to want to harden to shaft as well if you're expecting this to increase the life of your transmission. A stock transmission fails by deforming the shaft as well as the plate.

[Teched3]

Originally Posted by fox46

Ether, here are the hand drawings that the guys have been working from. Not all the dimensions are on them but anything that is missing is pretty easy to figure out. Hope this helps.

All excellent feedback regarding the banebot mods. That is what this "project" is all about. Some of us want a Corrvette for the price of a Fiat. Some things I noticed for those of you planning on modifying the banebots:

The drawing is missing the rear guide pin on the output shaft that centers in the 3rd stage carrier plate. Is it machined integral with the output shaft, or a pin pressed into the shaft.

Are you using extended inner race bearings where the spacer is located?

Is there any problem with the spacer moving off center when you grease and reassemble?

Banebots has been very responsive to suggestions for improvement. You should talk to them. Thank you for doing this.

[fox46]

The drawing is missing the rear guide pin on the output shaft that centers in the 3rd stage carrier plate. Is it machined integral with the output shaft, or a pin pressed into the shaft.

I am not sure I follow you on this- our P60s didn't come with any kind of a guide pin. I think I can imagine what you are talking about though- is it a pin that locates the 3rd carrier to the output shaft? I noticed there is indeed a hole through the center of the carriers but there is no bore machined in the output shaft.

Are you using extended inner race bearings where the spacer is located?

No, they are just regular bearings. I suppose you could put a spacer between the races but we are just leaving it up to the spacer on the output shaft to space them.

Is there any problem with the spacer moving off center when you grease and reassemble?

The spacer can sometimes slide out of line but all you have to do is use a screwdriver to poke it back into position from the other side before sliding the shaft on. The spacer is machined with chamfers so that it is somewhat self-centering and will slide onto the shaft as long as you get it close. The fit between the shaft and spacer does not have to be tight as it just keeps the bearings from wandering along the shaft.

I like the hardening- it will probably solve some of the issues but I would be very leery about the possibility of making the parts brittle- especially the output shaft interface. let us know how it works out!

[sanddrag]

So, today we had our first BaneBots failure. It's a 256:1 P60. It slightly spun the ring gear and really seized the whole thing, before we even made it to the field. It sees only about 10 or 12 lb-ft average load, not accounting for acceleration of the arm or shock loading. The shaft is well supported. It has probably only 50 cycles of our arm on it. We took it apart, and found the DD hole in the final carrier plate and the DD shape on the output shaft to be significantly yielding/deforming. We had that welded up at the regional. Also, in place of the roll pins on the end block, we had them put in a couple weld beads, and file it flat, to match the flats on the gear. It seems to be okay now, we'll see how long it lasts.

Also, one interesting thing we discovered is that the optional Steel ring gear has slightly different dimensions than the Aluminum one. It shouldn't be different, but it is. The distance across the flats is different.

[billbo911]

Originally Posted by sanddrag

So, today we had our first BaneBots failure. It's a 256:1 P60. It slightly spun the ring gear and really seized the whole thing, before we even made it to the field. It sees only about 10 or 12 lb-ft average load, not accounting for acceleration of the arm or shock loading. The shaft is well supported. It has probably only 50 cycles of our arm on it. We took it apart, and found the DD hole in the final carrier plate and the DD shape on the output shaft to be significantly yielding/deforming. We had that welded up at the regional. Also, in place of the roll pins on the end block, we had them put in a couple weld beads, and file it flat, to match the flats on the gear. It seems to be okay now, we'll see how long it lasts.

Also, one interesting thing we discovered is that the optional Steel ring gear has slightly different dimensions than the Aluminum one. It shouldn't be different, but it is. The distance across the flats is different.

When you have time, take a look at this possible solution, it might just do the trick. There is a question as to it's legality according to this year's rules, so please think it through before you implement it.

[fox46]

Well we just got back from our competition in Boston and this mod DOES INDEED FIX THE P-60 ISSUES! We ran the whole competition without a single failure with these modifications. In fact, while testing our autonomous program we hyperextended our arm and one these little guys stalled with a fisher price motor on it and then proceeded to rip our counter-balancing gas shock right off its mountings without any damage to the gearbox. If you are having P-60 woes, here's your way out.

PS: We elected to run the steel ring geas.

Best of luck!