Gearboxes? Help!
 

Hi! I'm Pauline from 589 Falkon Robotics. Since our inception in 2001 we have been using the AndyMark toughboxes a lot! I believe one year we created our own custom gearboxes and it went great, but that was over 5 years ago.
I am the head of the whole drive system team and really want to either build our own gearboxes or use better ones than the andymark tough boxes.

Don't get me wrong the Andymark toughboxes are awesome! Though we have been using our robot more and more every off season and the andymark ones are simply not holding up.

Any suggestions? Anything would help! :) Thank you!

Re: Gearboxes? Help!
 

Can you describe the failure you are experiencing. Pictures are a great supplement as well.

We make custom gearboxes for almost every system, and most are nearly identical in AndyMark in terms of what would wear out or fail.

If you're experiencing failure it's likely lack of grease, foreign debris causing issues, misalignment causing gears to clash, etc...

Re: Gearboxes? Help!
 

Are you asking for alternative gearboxes or an explanation on custom gearboxes?

If you're looking for alternatives, I would highly recommend CIMple-box, the ones that were in the KOP in the last two years. They're really sturdy, and even though they have only 1/3 of the toughbox's reduction, we got great speeds and intense pushing power with them.

If you're thinking of custom, I can't help unfortunately

Re: Gearboxes? Help!
 

The thing is we have had professionals look at the boxes (we broke down on a sponsor trip at an engineering company..so awkward). We applied as much grease as we have in years past, actually more than usual. My theory is just it had so much strain on it that is caused a misalignment in one of the gears. The mentor who is an expert on drive systems simply explained that "these gearboxes are only meant to last through competitions, we have used [our robot] more than any other. "

The pictures are here: http://imgur.com/A4mus,yHWxC,7Fs1Z,o...FlA T,RYjzn#1

Not all the pictures of parts have problems, I just decided it would be better to take pics of everything.

Re: Gearboxes? Help!
 

cimple boxes? I actually have built a few for testing code in the beginning of season? how many of them did u use on the drive system? one on each side?

Re: Gearboxes? Help!
 

Yes, and the same last year. In 2011 each powered three wheels, in 2012 four.
In fact, we were using the ones from 2011 since we got them until about a month ago (we're on a break), and they still work great. we used them on average about once a week for a few hours.
Again, highly recommended

Re: Gearboxes? Help!
 

Those appear to be the picks of a gearbox that was never properly greased.

Re: Gearboxes? Help!
 

;) That's what I said.

edit: Once it starts wearing down, it's a perceptual process. The ground up gear particles gets between the gears and further grinds them up.


Yes, the ones we used on the 2011 robot. They still work wonderfully. Second statement was not a question. From what I have observed on CD, most teams use 4 CIMs; 2 per gearbox.

Re: Gearboxes? Help!
 

I second this. I've looked through multiple gearboxes for use on our robots, and through all of them, the CIMple Box is by far one of the best. Very reliable, easy to mount, and saves teams a lot of money/time when designing a robot (no need to order different gearboxes, these come in the kit of parts!). 1 per side, and your drivetrain will be trucking all year long.

There's a reason that 1114 used CIMple Boxes in their Kitbot on Steroids. They're amazing.

Re: Gearboxes? Help!
 

How can they work perfectly fine for over 3 months and then all of a sudden just progressively get worse if it was not properly greased in the first place?

How did it operate correctly for such a long time?

Sorry, not trying to sound rude, I just really want to figure it out to insure it does not happen again!

Re: Gearboxes? Help!
 

One per side? Hmm.. I guess I can try it during off season. What is different about it that makes it so reliable?

Re: Gearboxes? Help!
 

Hard to say, just luck.

I don't see any grease on the gears or in the gearbox housing, and the condition of the gear and the shavings in picture 17 are classic signs of an improperly greased box.

Re: Gearboxes? Help!
 

Like the name suggests, it's very simple (3 gears, 2 of which are on the CIM motors), only 1 stage, so it's more efficient, and because of its simplicity, there are little to no possible failure points.

Just BE SURE TO GREASE THEM. (Caps and bold for emphasis)

Re: Gearboxes? Help!
 

hmmm okay! I'll for sure try it!

Re: Gearboxes? Help!
 

Alright! That would explain a lot! I'll look over the other gearbox and see if the same thing has happened! thank you!

Re: Gearboxes? Help!
 

No problem, I know the signs because I have done it myself :)

Re: Gearboxes? Help!
 

^That,
and I also think it has something to do with the fact CIMple-boxes are made mostly of plastic (which is ofcourse softer than aluminium), so gears lose less energy and are damaged less if (and they do) they scrape against the casing.

edit: This is wrong (except for agreeing with SuperNerd256).
For explenation (or excuse): http://www.chiefdelphi.com/forums/sh...7&postcount=30

Re: Gearboxes? Help!
 

We used the toughbox mini; which is essentially the toughbox's internals and a plastic casing.

Re: Gearboxes? Help!
 

The gearbox in the pictures (look at #15) is a toughbox mini

This is an original toughbox

I don't know much about the mini, but I do know the only toughbox we have on a competition robot has ran in about 50 matches, and in every demo we have had for the last 3 1/2 years, without any problems.

Also, looking at image #11, from the wear pattern on the gear it appears that only part of the gear (the bottom half) meshed with the other gear (the top has no wear). This may be how the gearbox is designed (I don't know, I haven't looked at one closely enough, but it may be an indication that the gears are not quite the right location. Maybe missing a spacer/spacer in wrong place). I would expect this to make it wear faster, maybe someone who knows more about this than me can answer that?

Re: Gearboxes? Help!
 

Regarding that, one of the engineers that helped us take it apart (We had LocTite on the shaft... Which is a different story) mentioned that the hex shaft needed more spacing from the body. That might have been a design issue, but the hex shaft was also worn away; which allowed the gear to shift from its correct position. We will need to do more investigation to confirm that.

edit: You can seen in pictures 13 and 14 that the corners on the hex shaft have been worn away. Not sure if that is significant enough to negatively affect the gear's position. Other issue might have been a bearing that was not properly fastened that might caused the shaft to jiggle.

Re: Gearboxes? Help!
 

The cimple box is great! but...

*WARNING*

The Cimple box is geared at about 4:1 and If you put a 1:1 sprocket ratio on there you will be going SUPER fast i'm talking 24fps. So please use the Double 12t sprocket on the output shaft (this comes with the gear box so you should have one) and use the 26t sprocket on the wheel. This will give you a nice 11fps speed.

This happened to me... but the opposite... I made the robot go to slow.

Re: Gearboxes? Help!
 

I think you are missing (or have put in the wrong place) a spacer of some sort. The hex shaft should not wear like that. I don't think it should even be touching a surface that it will move relative to (i.e., anything other than the gear, the race of a bearing, or a spacer that rotates with the shaft).

Unfortunately I can't confirm this as I can't look at the CAD file, and the pdf of the layout does not show the gears or spacers.

Any tiny misalignment in the shaft will increase the rate that it wears, and if the misalignment is large enough, it might stop the gearbox entirely. All parts should be secure, if something is capable of moving in any direction other than what is intended (anything other than rotation with the shaft), chances are something is wrong.

Re: Gearboxes? Help!
 

I fail to understand how that makes the cimple-box more efficient than a normal aluminum gearbox (al plates). If anything it should be less efficient than a correctly made/assembled gearbox regardless of plates.

Gears should never scrape against the plates. On a cimple box, the gear has a double protrusion, so it should never scrape against the gearbox.

-RC

Re: Gearboxes? Help!
 

This should be true. With all the parts that go into the gearbox, usually there are several ways to "make it work" that allow the motor to spin the output shaft, but only one is correct (and will make it keep working).

Re: Gearboxes? Help!
 

Do any of you build/design your own gearboxes?

Re: Gearboxes? Help!
 

I cannot find the pictures online right now (when I do I need to save them because I always have this problem) but your pictures are a deadringer for the wear a pair of our tough boxes showed in 09 as a result of the assemblers not putting in any grease.

What type of grease are you using?

EDIT: Here is the appearance of a completely messed up gearbox, no grease for an entire build season.



Set of photos

Re: Gearboxes? Help!
 

I agree with the above comments about grease.

We used AndyMark gears (which obviously are in AndyMark gearboxes) on all sorts of stuff. We reuse the heck out of them year to year, prototype to prototype as well. There isn't a 50 Tooth gear in our shop that hasn't been run a great deal.

In the 100+ AndyMark gears we've used in the last five seasons, only one was defective in manufacture (the hex bore was not aligned to the teeth and this gear wore oddly, but not enough to cause failure).

We designed and built 90% of the gearboxes on 973 vehicles for the last four seasons, plus numerous offseason items. As stated above, easily 80% of the gears in these gearboxes are sourced from AndyMark.

Re: Gearboxes? Help!
 

In 2009 I experienced similar failures of AndyMark 12 tooth CIM pinions. Teeth rapidly wearing/sharpening, even with grease. Once it starts, there's no stopping it, since the tooth profile has been altered (and you've now introduced debris into the geartrain). Switched to Martin gears for the pinions that year and never had a problem with those. If I recall properly (it was a while ago), the AM gear measured 22 on the Rockwell C hardness scale while the Martin measured 28. I think those particular gears have since been changed in the AM product line.

This year we made our own plates and shafts, but used all AndyMark gears. Not a single problem.

In your case, I'm going with the posters above: lack of grease. I don't see any other plausible explanation.

Re: Gearboxes? Help!
 

Actually, a few people commenting in this thread use custom gearboxes, but they are trying to get you to make a fully informed decision.

It seems to me, that if you feel like the AM gearboxes lack some level of quality, then perhaps you are not maintaining them properly. Of course you guys could have put the gearboxes through a particularly strenuous season/off-season, but many teams use the same gearboxes with little to no issues.

Most of the times, teams use custom gearboxes for the flexibility in design that they offers. People like to customize their ratios, build them to fit their chassis designs, and cut a lot of weight.

If this is the case, then the three criteria above are the first things you need to address.

For instance:

- What's the ratio? The ratio is important for obvious reasons, but it can be tough to nail down. This also requires you to answer exactly how the gearbox is being utilized. Is this going to be dedicated only to the DT? Are you planning on using it on manipulators as well?

- What's the interfacing? This needs to mount onto your chassis/frame. So you need to take that into account when you go into set up your gears/motors and when you go to design the side plates.

- Where can you be more efficient? You have to look into where you can be more efficient. This definitely includes weight, but gear usage is also a big one here.

I've never actually used/implemented a custom gearbox but I've designed/CADed multiple. Maybe someone with more experience would like to chime in with tips or suggestions.

- Sunny G.

Re: Gearboxes? Help!
 

You're right, and I apollogize. I wrote this thinking about one specific gearbox we didn't assemble correctly. I messed around with it alot lately and as a result I thought about it when posting.

I promise not to post at 4am again.

Re: Gearboxes? Help!
 

Though COTS gearboxes are recommended for teams who have not designed or prototyped custom gearboxes in the offseason, there are plenty of resources to help teams design their first custom gearbox, if you would like to give it a try.

To determine PD, OD, and center to center spacing of a gear, WCP has a neat feature on this page: http://wcproducts.net/how-to-gears/

To determine your desired gear ratio, use JVN's mechanical design calculator: http://www.chiefdelphi.com/media/papers/2059

In order to figure out mounting holes for a shaft encoder, check out http://www.chiefdelphi.com/media/papers/2681

Many of these resources make it easy to design a custom gearbox in CAD, but you do have to know what type of speed and ratios you want.

Re: Gearboxes? Help!
 

The Banebots p80 Gearbox is a workhorse. We've used 12:1 and 9:1 on our drive trains for direct-drive since we abandoned chain in 2008, and a 12:1 on our robot lift (with a 4:1 lead screw) in 2010, and have never had a failure.

The major caution there would be that BaneBots tends to run out very quickly during the build season, so buy early if you're planning on them!

Re: Gearboxes? Help!
 

We are using our summer to experiment with custom gearboxes and building our first west coast style drivetrain.

Here are some pics of our first custom gearbox, toughbox innards with custom sideplates:




We currently have on order a frame and gearbox plates from Team221.com: http://team221.com/viewproduct.php?id=108
When the plates arrive, we plan to machine lightening features to remove even more weight.

We are finding that the custom gearbox route is an interesting balance between cost, machining time, and design flexibility.

Re: Gearboxes? Help!
 

Just wanted to add a personal story about grease in a gear box...

A number of years ago we were at competition and were picked by another team for eliminations before lunch on Saturday. Naturally, we were all excited when we went to eat... then someone from the other team found us and said "we need help".

One of our mentors spent the entire lunch hour rebuilding BOTH of their toughboxes, which had failed in their last match. When it came time to add grease, he asked the team for some. One of their students pulled out the grease tube, and proceeded to squirt some on to a Q-tip. No joke. Apparently, when they put together their old gearboxes, this was how they greased them up. Our mentor asked for the tube, and right in front of their horrified faces squirted half of it into the gearbox.


That said, it is possible to put too much grease into a gearbox. For example, a sealed planetary like you can get from BaneBots will likely have issues if you pack it completely full of grease. However, we've found that the toughbox and CIMple box both have enough places where gear will work its way out that it's not really a problem. When our drivetrain first goes together each year, we let it run for an hour or two with no load, just to help wear in the parts a bit (we find it helps stretch the chain and then it meshes better with the sprockets). We fully expect grease to work its way out of the gearbox when we do this! If it doesn't, then we didn't add enough.

Re: Gearboxes? Help!
 

Bingo. We had both our toughboxes fail in 2010 because the original grease was cheap garbage. After nearly 100 matches it had turned solid and metal was the only lubricant that we had.

We now regrease before each competition. It's easy because there are holes that allow you to do so on the gearbox without opening it up! Just fill the sucker and tape over the holes.

Re: Gearboxes? Help!
 

I'm Glad I found this thread. I'm looking to experiment with a transmission that can take two motors. I thought of the CIMple box, because it comes in the KOP, and we have a bunch of them laying around. I was wondering if these were adequate, or was there an advantage to using something like a tough box, etc. From what I see here, the CIMple box sounds fine. Does anyone have alternitive views on a better choice for a dual motor transmission?

Re: Gearboxes? Help!
 

Define "better".

Single speed or multiple speed?
CIM or other motor?
Durability criteria?
Weight?
What does it need to attach to and how?


Any multi-motor gearbox on AndyMark will pass just about any FRC-type durability test. Most run with CIMs, but some run with others, or adapt other motors to mount like CIMs. Some are single speed, some are multiple speed, some can be stacked to get a higher gear ratio.

Re: Gearboxes? Help!
 

It all comes down to gearing. The CIMple box has some advantages because it consists of only a single stage of gear reduction, then a single chain reduction to the wheel. Less stages = higher efficiency = less parts = less complexity = less weight.

However, this means the internal ratio is limited and it might not fit in some drive setups.

Have you learned about drivetrain gearing or some of the other considerations of drivetrain design?

What wheels do you want to use? Why?
What configuration do you want to use for your gearbox? (direct drive? gearbox + chain?) Why?
Do you want to push? Why?
Do you want to have a high top-speed? Why?
Do you want 1-speed or 2-speed? Why?

Once you understand some of the tradeoffs there and have a better idea of what gear reduction you need before your wheels, you can then make better decisions about whether the CIMple box works for your application or whether you need something with more reduction, or 2-speeds, or whatever...

If you want to email me, we can talk through the goals you have for your drivetrain, and I can help you understand some of the tradeoffs you'll need to make. Then we can talk about COTS/Custom options to achieve these goals.

john.vneun@gmail.com
Tough to have that back-and-forth on a forum.

-John

Re: Gearboxes? Help!
 

You missed one (arguably) relevant question: How long does it have to run? If it only has to run ten seconds at the end of the match, that's one thing. If it has to run all two minutes, that's another thing. If it has to run all day at a demo, that's yet another thing. (We learned this nearly the hard way; after the season we stripped two CIMs off of our 2011 robot and used it for driver practice. Let's say we didn't get all the runtime we wanted before the motors were too hot to touch.)

Re: Gearboxes? Help!
 

Excellent point, Billfred. Al related a similar story in another thread recently; I recall that in Wildstang's case, they knew they would damage CIMs by continuous driving practice, pausing just long enough to swap in fresh batteries -- and they did it anyway because the practice time was more valuable to them than the CIMs.

Note also that a hot CIM case indicates a VERY hot CIM armature (that rotating electrical coil on the inside). Rated service life for a CIM, per its data sheet, is 1000 cycles of 6 minutes ON followed by 30 minutes OFF; the specified mechanical load during ON time is 4 lbf-in (64 oz-in) at 4320 RPM, with the motor drawing 27 Amperes from a 12 Volt supply.

In my lab we have set up a CIM with thermocouples on the case and on the brush holder (inside). We will run several cycles at the specified service life load point and record temperatures to make a plot vs. time. When I have that data I will post it. But even without temperature rise measurements, many of us who have run CIMs for driver training while draining several batteries can attest that they can get much hotter than we ever see during FRC match play.