And now that wife is situated with rack its time for a new better rack. Discussions at work there were lots of folks happy with the NSR4 from North Shore Racks. Other folks love the OnOne rack but when I looked at it, a big fancy machined alloy tray that hangs back from the truck: even a huge American truck looked like it was training to carry 4 bikes.
Ordered the NSR4, arrived in 2 days from Vancouver, BC. Assembled and installed on truck in less than an hour, and that includes the time it took to coach the kids into doing the work correctly and spraying the insides with fluidfilm.
Now almost 2 years later and several hundred days of use, gotta say it was a really good purchase. Rack is super easy to load and unload, doesn’t compromise visibility while driving, and folds away to be invisible.
Only thing I don’t like is that the bolt that connects the rack to the hitch didn’t come with a lock washer, so comes loose in seconds. I bought a piece of junk 5/8″ hardened split ring lock washer, it worked for 6 months but then wouldn’t hold.
Lock Washers and correct use of fasteners:
Neat property of metals is that they act like springs, all metal can be moved a little and will bounce back to exactly like it was before. This is called ‘yield’ and different metals have different amounts of springyness. If you ‘yield’ the metal too much it ‘statically deforms’ meaning it takes on a permanent bend. If you ‘statically deform’ metal it weakens, keep doing it and it will eventually break.
The correct way to tighten a bolt is to give it so much torque that the bolt starts to yield (fancy word for stretch.) This stretch means the bolt is like a spring and more resistant to coming undone from vibration. Bolts must be sized so that force on bolt causes it to yield but never “permanently deform.” In the case of this hardened 5/8″ bolt the torque to reach yield would be huge. Unreasonably huge and probably break the trailer hitch huge. So you need another way to prevent it from coming undone.
Funny thing, split ring lock washer’s only valid use is for bolts through wood. For metal the washer won’t provide adequate tension to hold against vibration. This was conclusively determined in the mid-40s, theory was refined through the 50s.
Now there are good lock washers in the world: the belleville (conical washer) is my favorite. Why is it that no local store in seattle has a 5/8″ belleville washer in stock? Or any other modern lock washer? So here was have an entire society that can only buy the bad wrong broken sort of lock washers? What the heck? Is everyone asleep?
Anyway, the split ring washer will work until the edge on the split wears. So if you go that route buy 5-10 of them.
I’m trying to get a good lock washer but not willing to pay $7-$10 shipping for a freakin’ washer. Not even amazon has them.
Here is an article about the difficulty of securing a bolt and how to use a Belleville washer:
So, next step is to call a bunch of obscure places and see who will sell me a reasonable Belleville spring for my application. Almost seems easier to try and make my own!
The other alternative is some locktite RED. RED is the permanent stuff, it dries hard and when you try and unscrew the bolt it shears off the threads forming little blobs of plastic that prevent the threads from unscrewing further. Only way to undo it is to head the threads enough to melt the blobs. I won’t do this with the hitch because I don’t have a way to heat it so much.
Followup on 1/26/17:
Couldn’t find anyone local who could sell me a few Belleville washers. Sure I can order for like $25 but that ain’t happening.
So mid December when the next lock washer stopped holding I did break out the bottle of RED locktite, cleaned the threads with detergent and then isopropyle. Did my best to clean grease out of the rack threads… dosed the bolt with RED and drove it in.
Now 1.5 months later the bolt hasn’t moved a whit. I guess that’s the answer, just wait until I need to remove it.