My Output Shaft Snapped.

[Fod]

Well, just based on a quick analysis using ANSYS, putting a radius as I showed reduces local stress by about 20%. Using the fatigue tool in ANSYS the same mod increases the safety factor of the entire shaft by about the same. I'm not saying these are absolute numbers as I don't have the exact material modeled or know the exact loading/cycle profile. I also had to increase the corner radius from my initial SWAG (scientific wild ass guess). However, it's a good indicator of the general direction and magnitude of the mod. So please let me know what I'm missing, I'm always looking to learn.


View attachment 7561View attachment 7562

Looking at the actual shaft though in Brian's recent photo, it doesn't seem that it's a sharp cut. It looks like there is a nice radius.

 

[Mark911]

It's possible. However, this is the view I was looking at. If there's a chamfer or radius it's pretty small.

 

[Fod]

It's possible. However, this is the view I was looking at. If there's a chamfer or radius it's pretty small.

View attachment 7563

Yeah, either way that's where it broke so that's the weakest section. Maybe the annealing could have been a little slower or they quenched it for a harder surface. Can ANSYS tell what's the best treatment for torsional and cantilever loads?

 

[Mark911]

All any FEA analysis software can do is use the user selected standard material properties in it's database or some other custom user defined material properties, it can't determine the best choice on it's own (I wish). I just used structural steel in my analysis. Although all the properties are important, the alternating stress curve is critical in life cycle analysis. Again, I wasn't looking for absolute numbers, just the general benefit of a radius on the O-ring shoulder.

 

[TCMB371]

The teardown has begun. More tomorrow.

 

[Redwolf]

 

[C5tor]

Warning: Explicit pictures to follow. There may be pictures of naked Altas.

 

[TCMB371]

Figured i might as well replace the drive and driven gears while I have this all apart. Can someone confirm the part numbers for the drive and driven gear for MXR?

From the old Alta parts list spreadsheet, i see there are two part numbers listed for each gear, each with a 00 and 01 variant.

Liquid has drive gear 4400050-00 and driven gear 4400055-01. Are these the correct ones?

 

[Rashid510]

4400050-00 is - GEAR, MOTOR PINION

4400055-01 is - GEAR, SPROCKET SHAFT

Those part numbers came from the last known data dump. We might have been doing some change control to adjust for suppliers but thats a moot point now. Those should be correct. They end up driving into the top level BOM which was the vehicle itself (aka the 2018-2019 model)

 

[TCMB371]

For science, heres how my original gears look after 190 hours. I cant notice any wear in them. For reference i have been using Lucas Oil synthetic 75W-90 gear oil.

 

[TCMB371]

Im having a bit of trouble removing the gears. Since the sprocket side of my output shaft is broken, i cant use the sprocket as leverage against the torque (70ftlb) of the nut holding the driven gear on. I dont want to jam something between the gears as that will add upward pressure to the motor shaft. Need to figure out a way to hold the driven gear in place so that i can remove the nut.

Ill probably figure it out but maybe someone can offer their advice. Is there a tool available to hold helical gears in place so that i can apply 75ftlbs to loosen this nut?

 

[Mark911]

Use an air or electric impact gun with a rag between the gears. Should spin the nut right off unless Alta used some kind of locktight. In that case, might need to apply some heat to the nut first.

 

[privateer703]

A piece of wood wedged between the gears has worked for me before, its soft enough it shouldn't damage the teeth but durable enough to take the torque required.

 

[rayivers]

Is there a tool available to hold helical gears in place so that i can apply 75ftlbs to loosen this nut?

I've had good luck with the Motion Pro 08-0427, on both straight-cut and helical. It seems to push against the tooth bases in a 'circumferential' direction, and the end engagement wedge has a slight tilt to it (probably for helicals).

 

[TCMB371]

So no concerns about applying upward force to the motor shaft? Maybe i worry too much lol

 

[rayivers]

Idk about the motor-shaft thing, but if you're concerned about it here's another tool I really like - the Motion Pro 08-0008 clutch holding tool. I've used it for a bunch of other things too, it's pretty versatile. Without protection it might chew the gear teeth a little, but if you're replacing them anyway maybe that doesn't matter.

 

[Rashid510]

So no concerns about applying upward force to the motor shaft? Maybe i worry too much lol

Shouldnt be an issue, especially in production we did a similar tool but with a chain and vice grip combo.

 

[Jared]

Shouldnt be an issue, especially in production we did a similar tool but with a chain and vice grip combo.

For what it’s worth, I rebuild Honda car transmissions, and they have three shafts with gears retained by large nuts that have to be removed. I take two pennies (1982 or older, so solid copper/not plated) stacked together and feed them into the gears to stop them. Never had any issue with damage to the gears or bearings, and this is cleaner and more predictable than feeding wood or a rag into the gears. Sometimes it takes nearly 200 ft lbs to break these nuts loose, especially if someone has been in there before and used an impact wrench to install the nuts. The pennies can usually be used a few times before the gear teeth cut all the way through them.

 

[C5tor]

For what it’s worth, I rebuild Honda car transmissions, and they have three shafts with gears retained by large nuts that have to be removed. I take two pennies (1982 or older, so solid copper/not plated) stacked together and feed them into the gears to stop them. Never had any issue with damage to the gears or bearings, and this is cleaner and more predictable than feeding wood or a rag into the gears. Sometimes it takes nearly 200 ft lbs to break these nuts loose, especially if someone has been in there before and used an impact wrench to install the nuts. The pennies can usually be used a few times before the gear teeth cut all the way through them.

Instead of saying “For what it’s worth…” you clearly should have opened with the phrase “For my two cents…” You rarely get the opportunity to use this phrase literally anymore, but here it is!

 

[VINSANITY]

The pre 1982 penny trick for gears is why I follow the forum so closely, some smart folks with lots of knowledge to share.