Jay brought one of his bikes to the test session done up with the same single speed mechanism, and while we were working out the intermediate section of the trail we both had troubles with chain poppage and gnarly noises coming from the units. It made for some sketchy moments but overall we had a blast. Once back to the car I checked out the unit a little more closely and found something interesting.
The mechanism is pretty simple, but to me the actual bolt holding the whole rig together just didn't have enough surface area to keep it from slipping.
You can see here that there was only about 1/16th" of the head of the bolt on each side of the plate holding the whole thing in place. Also, the in the top right you can see that the secondary pivot point was being held in place by the quick release nut. Additionally the bolt only reached about 1/4 way through the dropout threads. I decided that it could use a little more burly approach.
First step was getting the parts. Finding the bolt at Home Depot was a challenge, mainly because all of the stupid bolts they have are iin plastic bags. How are you suposed to test the thread pitch when they are in bags? It was actually funny. they have a display that you can thread bolts into to test, and for this application my bolt only went about 3 threads in and stopped. I basically just risked it by eyeballing the thread pitch and eventually pushing just the threads out of the bag the bolt was in to test it. Sure enough the new bolts only went three threads into the tester as well, so I knew I had the right size. In the lower photo you can see how much larger the new bolt is than the original.
I don't have any kind of miter for sawing bolts, so I came up with a different solution. I threaded the bolt through the dropout backwards and stacked a few washers on it to give a little bit of room for the bolt to go all the way through the dropout with a single flat washer and lock washer once completed. The idea was to keep the saw blade as flat against the dropout as possible to get a nice clean cut. Unfortunately the hacksaw blade was old and busted, which, ater about 30 mins of sawing resulted in this...
I headed back to Home Depot for some new blades and ended up finishing the cut in about 2 mins.
It may not be the most beautiful cut ever, but when I backed out the bolt it came out relatively easy and did not damage at all to the dropout threads. Once it was out I could easily thread it through from eaither side. I thought I was going to have to file it down or grind it down to make it easy to start, but that wasn't really necessary. So then it was all about reassembly.
If I had to do it over again I would probably opt for larger lock washers, but I was sick and tired of going to Home Depot and I think that the ones I chose will do the job fine. You can see that I also used a lock washer under the quick release nut, and I clamped the QR down good and tight. Plus the new bolt goes all the way through the dropout so there are a lot more threads holding it tight.
On my initial test ride, there were a few little knocking sounds, but I think that may be because I actually have the chain -reaaaalllly- tight. By the end of my test it had stopped protesting so much. I only took it up and down the driveway though. The real test will be next time I can take it to a trail, which I want to do as soon as possible. I'll try Gainesville College soon, and if it passes the test I am not afraid to take The Contraption to Chicopee. Can't wait to see the look on the MTB Freds faces when I roll around the the loop on some 700c's.
Well done! The contraption is radical dude!
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