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25th Aug 2021, 09:00 PM #1
Interesting comment on Utube about use of spring washers on towbars
You may find this interesting
John Cadogan the Automotive Engineer has some interesting comments to make on his U tube videos on NOT fitting a spring washer on vehicle towbar.
There is the original video that generated some dissent
https://www.youtube.com/watch?v=XjWH5G2sSgw&t=227s
and discussion of those comments on a following video:
https://www.youtube.com/watch?v=vaWqB09RHBk&t=1650s
I certainly had no idea about NOT using spring washers.
Grahame
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25th Aug 2021, 09:22 PM #2Diamond Member
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Spring washers suck. We make and repair a bit of gear for the mining and quarrying industries at work and spring washers have caused more problems than they have solved.
Its amazing how many people don't realize that bolts actually stretch and work like a spring when you do them up.
The video was good except for where he kept referring to the prop bolt as a M25.
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26th Aug 2021, 06:46 PM #3Most Valued Member
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There are four things that I absolutely, positively hate when dealing with bolting up components that need to stay in place and are under load.
1, Spring washers.
2, Mild steel bolts, (it's worth taking notice of how many plasticine bolts are factory fitment to motor vehicles).
3, Soft mild steel washers.
4, Nyloc nuts, (nylocs are soft and strip easily, there are many better locking nut choices such as cone locks).
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26th Aug 2021, 10:20 PM #4Most Valued Member
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27th Aug 2021, 09:36 PM #5Most Valued Member
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I've seen lots fitted to trucks and other more severe applications where the nyloc nut has mushroomed on it's contact surface thus leading to a loose condition and seen many stripped both during the tightening and unfastening phases, even with cheap Chinese rattle guns and hand tools. I will certainly agree that a brand new Nyloc will lock quite effectively provided it is not exposed to too much heat, although the latter cannot really be blamed on the fastener in any case.
None of the truck dealerships I've performed work for, (Isuzu, UD, Mitsubishi/Fuso, Volvo, Mack and Kenworth), would accept Nyloc nuts being used to attach turntables to prime movers and none of those makes use Nylocs in any chassis application.
I'm not against Nylocs and I do use them for non critical jobs, but I will never use them for real load bearing work.
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28th Aug 2021, 12:06 PM #6Senior Member
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When I change or fit up towballs I use a flat washer then the nut tightened up then use the nut from old towball as a locknut. Never had a issue and it saves the thread on towball from being damaged offroad.
Slightly off topic but have seen quite a few towballs recently with date of manufacture stamped on them. I change out towballs on average about every 2 years, just something that was mentioned to me years ago.
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29th Aug 2021, 11:59 AM #7Golden Member
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29th Aug 2021, 02:14 PM #8Most Valued Member
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I'd agree with that, with one qualification, that being that there is no point putting a Grade 5 Nyloc (or any other type for that matter) nut on a grade 8 bolt and expecting it to do it's job. Very few places supply grade 8 Nylocs and it is incredibly rare to be informed about the grade discrepancy between the nut and the bolt set you just bought.
I once had an employer that insisted upon the following when fastening down truck trays and drawbars - yes even Ringfeeder or Bartlett Ball drawbars. Grade 8 Cad plate bolts inj either 1/2 or 5/8unf, thick mild steel washer on both head and nut sides, spring washer and finished off with a grade 5 nyloc on the other side. If that's not a mish mash of faulty theories then I don't know what is. Worse still, our certifying engineer never batted an eyelid.
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29th Aug 2021, 03:49 PM #9Intermediate Member
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Have a read of this: https://ntrs.nasa.gov/citations/19900009424
Page 9 says helical ring washers are useless.
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29th Aug 2021, 04:30 PM #10Most Valued Member
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29th Aug 2021, 04:40 PM #11Most Valued Member
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31st Aug 2021, 03:51 PM #12Most Valued Member
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That is a fair point, however a large part of the shear strength in many bolted joints comes from the friction caused by the mating surfaces being held tightly together by the forces acting as a result of the tensile strength of the fasteners holding the surfaces together. While it may have occurred somewhere at some time, I can't ever recall seeing an engineering drawing specifying a grade 8 bolt with a lower grade nut.
For my money, if I need a grade 8 bolt, I want a grade 8 nut on it.
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