TheSamba.com :: View topic

Sun Jan 05, 2020 9:18 pm

Please don't yell at me if this is a silly question. I'm on some pretty serious pain meds right now but had this idea so I'm asking about it here.

I had some problems in the past with my stub axle nut unscrewing it self. I fixed the problem with a new axle and brake rotor but am still pretty paranoid about the nut backing off. Yes, it has the cotter pin in it but it did the other three times that it backed off and ate the pin in half. It wasn't pretty!

I got to thinking that if the "cotter pin" was stronger, it could have prevented the nut from backing off in the first place. So I did a little research into cotter pins. It seems that cotter pins are by design soft so they can be easily bent into place and then removed again. As far as I can tell, "soft" means edible!

So why not use a stronger security type pin? Is there any reason to not use something that is stronger than the soft cotter pin? For example: A run of the mill 1/8" dowel pin has a hardness of at least Rockwell C47 and a shear strength of 2600 pounds. A split pin with a cotter pin thru the middle to help keep it in place has a shear strength of over 3000 pounds! That's a heck of a lot more than a comparable sized cotter pin!

Yeah yeah I know that "it's been that way for a bazillion years and works well if everything else is in good shape so why change it now" etc. etc. My point is that it could be done better. Thoughts?

Mon Jan 06, 2020 12:42 am

I've seen people replace the cotter pin with a small bolt or wire clip type thing so I don't see why not. But I would be asking why you are having issues with shearing the cotter pin off. I've never done that before, even when I used a smaller wrong size cotter pin in a pinch. Are you torqueing the axle nut to 300 ft-lbs?

Mon Jan 06, 2020 4:56 am

I just use R clips. Spring steel so they're harder than a cotter pin and reusable too.

Mon Jan 06, 2020 7:10 am

Like said above, you should be torquing the crap out of that rear axle nut. I have never used a torque wrench to put one on, I just use a nut whacker and a hammer, but its definitely a couple hundred ft-lbs of torque. The pin is just there to prevent catastrophic failure.

Mon Jan 06, 2020 8:36 am

Like I stated in my first post: I fixed the problem with a new axle and brake rotor but am still pretty paranoid about the nut backing off. Yes, it has the cotter pin in it but it did the other three times that it backed off and ate the pin in half.

It doesn't seem to be backing off anymore but I'd like to be sure or at least as sure as possible that it won't back off. The R type spring clip sounds like a good idea. I may try one with some safety wire around the narrow end to keep it in place when I go thru brush and stuff. Yes, it's getting torqued to 300lbs. I use my rail for exploring old mines, trails and ghost towns with my wife.

Mon Jan 06, 2020 11:44 am

Wulfthang wrote: I use my rail for exploring old mines, trails and ghost towns with my wife.

Ah shit, I'm jealous. I can't think of a better pastime.

Mon Jan 06, 2020 3:37 pm

We uses the "hair pin" clips on our Auto X buggies, but it was only for "show"...

Dale

Tue Jan 07, 2020 5:40 pm

In my decades of offroad racing, I've seen LOTS of racers use R clips, many with a zip tie or safety wire on the end tor double insurance.

But as said above, If the nut is properly torqued, it should never back off anyway. Drum or disc brake hub may be bad or bent, too much wheel offset can contribute to trouble, badly out of balance or bent wheel assembly, bad bearing thrust spacer(s)...etc.