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Unread 09-20-2017, 06:34 PM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by CEF View Post
Well, I was thinking more along the lines of this: https://www.amazon.com/150-Pieces-Co...dp/B01BGZ9VJS/
I'm really really really not a fan of cotter pins, so I'll admit that I'm biased. But I don't like the idea of those cotter pins spinning around at a couple hundred RPM on the inside of my robot. Plus, I feel like using cotter pins would require extending the shafts moreso than any other method.
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Unread 09-20-2017, 07:56 PM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by CEF View Post
Well, I was thinking more along the lines of this: https://www.amazon.com/150-Pieces-Co...dp/B01BGZ9VJS/
Don't. You'll thank me when your robot's wheels stay on after a hit.

That particular type just needs enough force to get past the center section it's supposed to be in and it's out. If it flips at 90* to the axle it needs a lot less. Guaranteed some poor kid is going to forget to flip it down to lock it, and that fact will be missed when the bumpers are installed.

Can it be done, and done well? Yes. But the risk is too high.
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Unread 09-21-2017, 10:14 AM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by Cothron Theiss View Post
I'm really really really not a fan of cotter pins, so I'll admit that I'm biased. But I don't like the idea of those cotter pins spinning around at a couple hundred RPM on the inside of my robot. Plus, I feel like using cotter pins would require extending the shafts moreso than any other method.

Castellated nuts (slot nuts) and cotter pins have held many an automotive and truck double tapered wheel bearing together. At 60 mph they reliable spin a whole lot faster than anything in a robot.

Cotter pins are intended as an anti-rotation device, not as an axial retention device. A 1/8" 316 stainless pin likely would not break in competition, it would take about 2000 pounds of shear force. It's certainly stronger in shear than an E-Clip. There are simply a lot better methods available however.

A low resource team can end drill the shaft ends as close to on center as possible; and then use a self-tapping screw and washers to retain the axles. You could even make tooling to do this consistently with a hex hub and AndyMark flat plate (AM-2069). Install a drill bushing in the center hole.


http://files.andymark.com/LayoutPrin...late+REV+2.PDF
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Unread 09-21-2017, 10:45 AM
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Re: Westcoast Drive bearing + axle retention

We Loctite the inside retaining bolt, but not the outside bolt of our drive train shafts. This allows for easy maintenance. Part of our pre-match checklist is to check these bolts since it's an easy 10-second check.

We had a "very successful"(TM) match in 2017 without an outer retaining bolt. The bumper kept the wheel on. I don't recommend doing this intentionally.
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Unread 09-21-2017, 11:05 AM
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Re: Westcoast Drive bearing + axle retention

Quote:
Originally Posted by InFlight View Post
Castellated nuts (slot nuts) and cotter pins have held many an automotive and truck double tapered wheel bearing together. At 60 mph they reliable spin a whole lot faster than anything in a robot.

Cotter pins are intended as an anti-rotation device, not as an axial retention device. A 1/8" 316 stainless pin likely would not break in competition, it would take about 2000 pounds of shear force. It's certainly stronger in shear than an E-Clip. There are simply a lot better methods available however.

A low resource team can end drill the shaft ends as close to on center as possible; and then use a self-tapping screw and washers to retain the axles. You could even make tooling to do this consistently with a hex hub and AndyMark flat plate (AM-2069). Install a drill bushing in the center hole.


http://files.andymark.com/LayoutPrin...late+REV+2.PDF
Yup. I've used castle nuts quite a bit on my Baja team. We try and use safety wire for all of our positive locking, but for the wheel spindles, there's no way to, so we use castle nuts. We've never lost a wheel, but we've often done post run check-ups and noticed missing or damaged cotter pins. We've been considering different alternatives the past two years, but the moral of the story is that we're trying to move away from cotter pins.
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Unread 09-21-2017, 11:47 AM
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Re: Westcoast Drive bearing + axle retention

For those using bolts instead of using a thread locking compound many of which can damage plastics I suggest nylock bolts. https://www.mcmaster.com/#thread-loc...crews/=19hbwks Very effective in my experience.
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Unread 09-21-2017, 12:02 PM
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Re: Westcoast Drive bearing + axle retention

Quote:
Originally Posted by InFlight View Post
A low resource team can end drill the shaft ends as close to on center as possible; and then use a self-tapping screw and washers to retain the axles. You could even make tooling to do this consistently with a hex hub and AndyMark flat plate (AM-2069). Install a drill bushing in the center hole.
Another way make a tool for this is to use a 1/2" hex coupler and a short piece of thunderhex. The coupler "couples" the shaft you want to drill and the piece of thunderhex, and you can use the thunderhex center hole as guide to drill the other shaft.

But if you have that, you can just use all thunderhex and avoid all the drilling...
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Unread 09-21-2017, 12:03 PM
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Re: Westcoast Drive bearing + axle retention

Pwnage used these external retaining rings.
No special tool beyond a flat blade screwdriver.
McMaster_98420A138
https://www.mcmaster.com/#catalog/123/3311/=19hc1wv

You can download our 2017 robot CAD using this link to see how they were applied.
https://grabcad.com/library/2017-pwnage-frc-robot-cad-1

Or you can download this assembly work instruction.
https://www.chiefdelphi.com/media/papers/3392
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Unread 09-21-2017, 12:20 PM
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Re: Westcoast Drive bearing + axle retention

In FRC we use a 10-32x3/8 bolt and washer with no loctite in our axles. This is the only thing we've tried and we like it.

An option one might consider in the vein of snap rings are 'spiral rings' which need no tools to install, provide a continuous support surface, and are nearly impossible to pop off unintentionally. See: https://www.mcmaster.com/#91650a420/=19hcdlp This has worked well for me outside of FRC.
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Last edited by JamesCH95 : 09-21-2017 at 12:26 PM.
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Unread 09-21-2017, 02:10 PM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by Cothron Theiss View Post
Clamping Shaft Collars
This is the easiest to manufacture, but you have to buy and keep shaft collars on hand. Also, the shaft collars can become loose at critical moments.
I can't even begin to tell you how many wheels we had come off in the middle of matches during the 2016 season when we only used shaft collars (good thing we were running an 8WD) This year we switched to tapping the axle and using washers and bolts for retention and boy do I wish we had taken the time to do it that way in 2016! It takes very little time and can be done with very basic tool. I highly recommend it!
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Unread 09-21-2017, 05:44 PM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by kristinweiss View Post
This year we switched to tapping the axle and using washers and bolts for retention and boy do I wish we had taken the time to do it that way in 2016!
We used bolts last season and ran into a problem: The wood frame of one of our bumpers was slightly pressed against a bolt. Over the course of several matches, there was enough friction to actually unscrew the bolt from the end of the axle. We drilled a hole out of the wood frame to solve the problem.
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Unread 09-22-2017, 12:00 AM
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Exclamation Re: Westcoast Drive bearing + axle retention

We countersunk thick flat washers to use with flat head screws.
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Unread 09-22-2017, 12:11 AM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by Richard Wallace View Post
We countersunk thick flat washers to use with flat head screws.
That's a clean looking solution. Is it shorter than a thin steel washer + button head screw?
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Unread 09-22-2017, 12:11 AM
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Re: Westcoast Drive bearing + axle retention

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We countersunk thick flat washers to use with flat head screws.
I'm intrigued by that mix of belt and chain on the outside of the drive rail. Care to share how that went and why you guys chose it?
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Unread 09-22-2017, 12:37 AM
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Re: Westcoast Drive bearing + axle retention

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Originally Posted by Selle2.0 View Post
That's a clean looking solution. Is it shorter than a thin steel washer + button head screw?
Yes, that is why we did it.

Quote:
Originally Posted by Cothron Theiss View Post
I'm intrigued by that mix of belt and chain on the outside of the drive rail. Care to share how that went and why you guys chose it?
No issues through five regular season events. We wanted extra confidence for the middle wheels of our 8WD, and weight savings for the corner wheels.

Our climber PTO is powered though one of the corner belts, so they really are strong enough.
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