bolt & crown nut with cutter pin

[ddace]

This question might seem lame but I want to know if it is at all possible, for a 1 inch grade 8 bolt torqued at only 200 ft*pound (very little preload) secured with a cutter pin, could come loose ?

This is to secure diesel engine mounts on a skid base. So the joint will be exposed to engine vibration and also engine torque. I realy need to maintain that small but minimum preload at all times.

thanks

 

[CWIC]

ddace:
This method is probably the most common for securing motorcycle wheels to the forks and rear swingarm. The wheels obviously see substantial torque during braking or acceleration. The beating they get driving down a road or off-road (much more severe) is constant and substantial as well.

Bikers call this the "Jesus Nut" for obvious reasons if the nut/cotter pin fails. The axles are not tightened very much (depends on the machine, so don't ask for a hard number) so that the wheel bearings are not destroyed in a short period of time.

 

[MintJulep]

A castleated nut and a cotter pin allows a relatively large amount of rotation between the nut and bolt. This might cause a change in your preload.

Why not use a stack of Bellville washers, or even a coil spring to establish your desired load. Use a nylon locking nut to maintain the right spacing.

 

[ddace]

thanks for the input guys

CWIC

I like the term "Jesus Nut" lol. I never herd that one before. But I see what you meen. That same principle is applied on front wheel bearings on most rear wheel drive vehicules.

P.S What is specifier/regulator?

MintJulep

What do you mean by "large amount of rotation between the nut and bolt". Is it the fact that the nut can lossen until it jams againts the cotter pin?

And what are Bellville washers?

 

[unclesyd]

CWIC purloined the "Jesus Nut" from the helicopter guys.
The nut that held the rotors on the drive shaft was called the "Jesus Nut" and was tightened with the "Jesus Wrench" made by Raymond Engineering. At the old NADP in Pensacola, Florida I never heard this nut referred to anything else.
Loss of integrity in this nut resulted in the worst possible situation for a helicopter pilot and his passengers.

 

[MintJulep]

Ddace,

In this case, "a large amount of rotation" may be 1 or 2 degrees. Doesn't sound like much, but could have a significant effect on the preload.

Bellville washers are conical springs.

 

[CoryPad]

ddace,

Yes it is possible for this joint to loosen. A castellated nut plus cotter pin plus stud/bolt with a cotter pin hole is a loose fit assembly. It can allow enough rotation of the nut before the nut contacts the pin to result in nearly complete preload loss. Also, the pin is not strong, so it can deform, allowing more rotation and preload loss.

A Belleville washer is a conical spring washer. There is plenty of basic information on the Internet. If you need detailed information for design purposes, try reference 2 here:

faq725-600



Regards,

Cory

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