Spring lock washer vs. internal tooth lock washer.
Spring lock washer vs. internal tooth lock washer.
(OP)
My company manufactures bridge crane and monorail systems. We have a current field issue in which the screw holding a trolley wheel keeps loosening. The screw is locked in place with an internal tooth lock washer, as shown in the illustration. The end user has asked for a torque value for this bolt. We normally use lock washers. Would a spring lock washer be a better option for this application?





RE: Spring lock washer vs. internal tooth lock washer.
Lock washers don't lock anything.
As a start, see FAQ404-1257: Is a lock washer an effective torque retention device?
There are many discussions on this site about preventing threaded fasteners from loosening.
RE: Spring lock washer vs. internal tooth lock washer.
http://www.boltscience.com/pages/helicalspringwash...
I've used Belleville washers on a lot of electrical equipment that thermally cycles with good success in not having them loosen. You might want to look into that type of fastener.
Dik
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
Do you use thread lock adhesives?
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P.E. Metallurgy, Plymouth Tube
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
How many users have a loosening problem?
Is this size trolley a new product, or a "mature" product with dozens of successful installations elsewhere?
Any chance your trolley is being grossly overloaded?
Is the trolley wheel bearing a ball or roller bearing?
Or a plain bearing /bushing of some sort?
If the wheel has loosened a few times, component mating surfaces may now be so torn up that "embedding" is now unavoidable and all bolt preload will be lost after brief service.
By inspection the head/shoulder on the threaded insert looks pretty thin to resist the clamping force I expect I would want to exert with the bolt. As others said, the first line of defense against fastener loosening is correct tightening, which will induce preload/clamping force greater than all loads experienced in service.
Here is a line out of some Military document about fasteners.
RE: Spring lock washer vs. internal tooth lock washer.
Try using nordlock washers
http://www.nord-lock.com/nord-lock/wedge-locking/w...
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
RE: Spring lock washer vs. internal tooth lock washer.
The trolley is a mature product. This particular issue came up only recently, and affects only a few units. I haven't gotten any word yet on if it's being overloaded or if there is any damage.
Additional info is on the updated attachment.