I need some live axil design tips!

[Cory]

Originally Posted by Sh1ine

Actually we plan to use hex shaft, I failed to mention that in my post. The snap ring preforms without issue?

a properly seated 7/16" snap ring can take a 3,000 lbf thrust load, if I remember correctly. The key here is properly seated. As long as you can cut the groove properly, ensure proper axial spacing so the snap ring groove isn't interfered with, and don't re-use snap rings, you shouldn't experience any problems.

[Hawiian Cadder]

a little advice to you, DONT USE LIVE AXLE DIRECTLY OFF BANE BOTS P80's the e rings inside the gearbox break all the time, then they have to be taken apart and fixed.

we typically use collars, but we taper the edge on a mill or with a grinder so that the edge of the collar does not rub against the bearing seal. key-stock or hex broached axles are necessary to drive the wheel. with live axles i also would recomed a larger diameter of axle, while 1/4 or 3/8 axle is fine for dead axle, 1/2 or 5/8 is better for live axle, good luck.

[Trent B]

Originally Posted by Hawiian Cadder

a little advice to you, DONT USE LIVE AXLE DIRECTLY OFF BANE BOTS P80's the e rings inside the gearbox break all the time, then they have to be taken apart and fixed.

We direct drove 2 traction and 2 omni wheels off of P80s last year, but we had the shaft run through a bearing block first so the internal bearings of the gearbox wouldn't have as much load.

[KrazyCarl92]

I know for a fact that each of the crab drive modules on our robot this year had a snap ring (about 1/2" diameter I think, but don't quote me) holding them to the shafts that essentially bore the weight of the entire robot, which i would think would fall around 25 lbs per snap ring or so when you consider that they don't bear the weight of the wheels themselves and then the battery is added. So if you are concerned about their durability when bearing force, I would think it shouldn't be a concern. The only times I know of this season when we broke or warped a snap ring was when we were taking them off or putting them back on. They were very reliable for our application, but I can't say much about their application in live axle design.

[Travis Covington]

Originally Posted by Cory

a properly seated 7/16" snap ring can take a 3,000 lbf thrust load, if I remember correctly. The key here is properly seated. As long as you can cut the groove properly, ensure proper axial spacing so the snap ring groove isn't interfered with, and don't re-use snap rings, you shouldn't experience any problems.

This sounds right for ring shear, but if you use a material with a lower yield strength than the retaining ring itself, you will likely see a lower thrust load capacity due to groove yield. With 7075 or something similar, you should still get ~2000 lbf of thrust load capacity. These theoretical calculations assume a perfectly round retaining ring with no seam, so real numbers will vary.

[jspatz1]

If this is your first experience with live axles and with a new drive arrangement, it might be a good idea to build it initially with spacers and collars. There is a very good chance you will make changes and adjustments as you go along, which is easily done with spacers, but not with ring grooves. Hex shafts are a bit expensive to remake too many times. You can always add grooves and rings and remove excess length when you have the arrangement perfected. Buy a stick of nylon tubing (Mcmaster) which fits your shaft, and you can quickly make custom spacers as needed.

[Dick Linn]

These folks make nice shaft collars. I got some from MSC a long while back.

http://www.ruland.com/

If you need spacers, you might try making them from PEX tubing. It's tough stuff and CHEAP (like 30 - 50 cents per foot) if you can find short, straight lengths. Try Lowes or Home Depot.