In Need of Gears and 775pros

[michchinn]

Originally Posted by Aren_Hill

Since we are out of the 20T aluminum gears for this season, these gears are compatible but will require you to get them hex broached.
Martin Gears on Amazon

Also the steel gears may not wear as fast.

Will using a steel 20t gear in the 3rd stage accelerate wear on the aluminum 64t gear that it meshes with in the third stage?

Thank you all for your help and suggestions.

[aldaeron]

Originally Posted by michchinn

Will using a steel 20t gear in the 3rd stage accelerate wear on the aluminum 64t gear that it meshes with in the third stage?

Perhaps. There is a lot of discussion about 3rd stage gearing wear for a Ball Shifters on this thread. I would contact some of the folks on there that have put these gearboxes through very, very tough trials.

-matto-

[Doug G]

Originally Posted by aldaeron

Perhaps. There is a lot of discussion about 3rd stage gearing wear for a Ball Shifters on this thread. I would contact some of the folks on there that have put these gearboxes through very, very tough trials.

-matto-

We went to 3 regionals this year and wore through 5 20T VexPro gears with our 3rd stage of Ballshifters. We ended up switching to the Andymark steel gears (broached hex). At the end of our Idaho regional, our 64T VexPro gears were trashed, luckily we had replacements for those.

Some of our issues were due to the lack of securing the 3rd stage to the BallShifter. We were having a lot of binding when we tightened the 3rd stage too much, so we tried to find a happy medium between too loose and too tight, we think this caused some issues with gear tooth engagement when it experience shock loading.

This year was rough on drive trains.

[techhelpbb]

For those of you that broached gears how did you align things?

I tried a rotary broach in a Bridgeport but found it difficult to get a good center. The existing keyway in the gear would end badly on a coaxial indicator. I tried a few times with a 0.2 edge finder and the DRO but still managed to be broached straight but slightly off center.

It is either I am off center or my back plate protecting my chuck face is not rigid enough. It is strange because I drill out the hole to 33/64" and chamfer before I go in. Center does not move. I have not tried this much lately....maybe just have not gotten the knack of it.

[asid61]

Originally Posted by techhelpbb

For those of you that broached gears how did you align things?

I tried a rotary broach in a Bridgeport but found it difficult to get a good center. The existing keyway in the gear would end badly on a coaxial indicator. I tried a few times with a 0.2 edge finder and the DRO but still managed to be broached straight but slightly off center.

It is either I am off center or my back plate protecting my chuck face is not rigid enough. It is strange because I drill out the hole to 33/64" and chamfer before I go in. Center does not move. I have not tried this much lately....maybe just have not gotten the knack of it.

We use a standard push broach, and it works fine for keyed gears. Fine enough for FRC, anyway.

[techhelpbb]

Originally Posted by asid61

We use a standard push broach, and it works fine for keyed gears. Fine enough for FRC, anyway.

That is my Plan B. Kind of hoped to sort out where the weak points of Plan A were and if there where a good fix.

Originally Posted by R.C.

If you have a rotary broach, I would use the lathe instead of the mill.

Seems a similar alignment issue. Gear is just a bit too big for a 5C collet. Plus the collet would not likely provide the support for the thrust involved. It is an even number of teeth so a 3 jaw chuck will not engage the teeth all the way around. My 4 jaw Chuck are all independent so then I need to center. The way I center I guess I would need to turn down a rod snug to the bore and use a dial test indicator.

Any other ideas cause my press is looking good right now

[R.C.]

Originally Posted by techhelpbb

For those of you that broached gears how did you align things?

I tried a rotary broach in a Bridgeport but found it difficult to get a good center. The existing keyway in the gear would end badly on a coaxial indicator. I tried a few times with a 0.2 edge finder and the DRO but still managed to be broached straight but slightly off center.

It is either I am off center or my back plate protecting my chuck face is not rigid enough. It is strange because I drill out the hole to 33/64" and chamfer before I go in. Center does not move. I have not tried this much lately....maybe just have not gotten the knack of it.

If you have a rotary broach, I would use the lathe instead of the mill.

[BeardyMentor]

Originally Posted by michchinn

Will using a steel 20t gear in the 3rd stage accelerate wear on the aluminum 64t gear that it meshes with in the third stage?

Thank you all for your help and suggestions.

The answer is probably yes depending on the hardness of the smaller steel gear and coatings on the aluminum gear.

Good news though. for the run times of a typical FRC robot, it wont matter much. The larger gear will almost always wear more slowly than the smaller gear because each tooth on the larger gear will see fewer cycles. With matches only a few minutes long and seeing a maximum of 21 at an event (except for replays) the aluminum gear should not be seeing much wear in the 40 minutes or so it is going to be running for.

However, in the future I would advise you to not use aluminum gears unless you are right up against the weight limit or are using very large gears (team 25, I am looking at you with those massive gears on your wheels...) Steel has better wear and fatigue properties in general. If you are really concerned about durability of the gears you can always have them case hardened. I did this to an old toughbox that I use for a 6000 watt motor (~15 CIM equivalent) to power a silly electric racing car and I have run under load for about 15hrs with almost no signs of wear.

[Chris is me]

Originally Posted by michchinn

Will using a steel 20t gear in the 3rd stage accelerate wear on the aluminum 64t gear that it meshes with in the third stage?

Thank you all for your help and suggestions.

Yes, but if you properly lubricate your gears they will not wear significantly within the runtime of an FRC robot, and this will not compromise performance. Aluminum gears like to wear a little until they run nicely and then that tapers off for a bit.

However, I would advise you to not use aluminum gears unless you are right up against the weight limit or are using very large gears (team 25, I am looking at you with those massive gears on your wheels...) Steel has better wear and fatigue properties in general.

There is nothing wrong with using aluminum gears in FRC - the weight savings is dramatic and for most applications the strength is just fine. The aluminum gears Vex produces are of higher quality than steel gears from AndyMark as well - better tooth profile, more consistent manufacturing, etc. Wear and fatigue properties are not really a concern with 100-200 hour run times.

[Sperkowsky]

We have a 775pro but are out on long Island so a bit of a hike.