Gearboxes? Help!

[IndySam]

Originally Posted by pauline589

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

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

[bardd]

Originally Posted by SuperNerd256

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)

^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

[davidthefat]

Originally Posted by bardd

^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.

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

[John]

Originally Posted by davidthefat

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

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?

[davidthefat]

Originally Posted by John

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?

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.

[MattC9]

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.

[John]

Originally Posted by davidthefat

mentioned that the hex shaft needed more spacing from the body.

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.

Other issue might have been a bearing that was not properly fastened that might caused the shaft to jiggle.

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.

[R.C.]

Originally Posted by bardd

^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.

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

[John]

Originally Posted by R.C.

If anything it should be less efficient than a correctly made/assembled gearbox regardless of plates.

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).

[Pauline Tasci]

Do any of you build/design your own gearboxes?

[Trent B]

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

[AdamHeard]

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).

Originally Posted by pauline589

Do any of you build/design your own gearboxes?

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.

[sanddrag]

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.

[ttldomination]

Originally Posted by pauline589

Do any of you build/design your own gearboxes?

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.

[bardd]

Originally Posted by R.C.

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

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.