Making My Dropouts
Posted: January 13, 2012 Filed under: Uncategorized
Following on from my previous post, I’ve been back down to the workshop to do some more work on my dual-use dropouts that I designed to accept 120mm hub fixed wheels or 130mm cassette geared wheels with a derailleur.
Here’s a peek at what I’ve been up to:
Tapping M5 threads for the rack & mudguard mounts.
After tapping all the threads with cutting oil in the drill press chuck, I got pretty grubby!
I then had to degrease, wash and dry the dropouts ready for brazing.
I dried them with paper towels after using detergent and warm water to remove the degreaser.
I sanded the mating faces so the brass would take as well as I hoped it would.
Pre-braze cleanup completed.
I took this opportunity to file off the marks from the waterjet cutting process, as it would be much more difficult after brazing.
..It took a while..
I took a 2mm drill and cleaned out all the abrasive paper debris from the pin holes by hand.
Next, I fluxed up all the dropouts with Tenacity 125 flux, the same stuff they use in the autobrazers at work. I added some more after this photo was taken.
My NASA-grade Wilkinson FX497DBJ dropout brazing jig is set up in the vice. This hi-tech model allows all-round flame access.
I tacked the ends first to try and eliminate lifting of the track faces. This was about midnight.
Moving the flame around the dropout.
It was a little challenging to control the heat whilst looking for the brass to flow all the way through.
I moved the torch around underneath to try and spread the heat evenly.
My workshop-mate Ryan took these pictures. That's his torch and glasses too. Should've remembered that dust masks don't work with tinted glasses - some of your breath is channeled up around the sides of your nose and steams them up. At least in London in January it does.
It took some time to braze 12 of these..
..But I seemed to get better at it as I went along.
Filing the track slot flat and square after brazing.
I decided to get the dropouts shotblasted as the flux is not water soluble and there was a little blackening here and there.
Trial-fit to my road bike wheel.
I discovered a small obstacle, being that the quick release nut will not quite slide past the derailleur mounting bolt/pivot when removing the wheel. This isn’t as bad as it sounds, as there is plenty of metal that can be filed away so that the axle and nut can come forward a touch at the bottom of the vertical dropout slot. I basically just need to round the corner off like this:
I need to carefully file a new curve profile something like this so that the nut can pass the derailleur mount. A bit of weight loss won't hurt..
At least I didn’t order a thousand investment-cast pairs with this issue. Wilkinson Cycles is constantly striving towards improved design by research and development!
I also intend to chamfer the edges of the dropouts to a rounded curve by filing them. Laborious? Yes, but also very rewarding. I’ll get the track faces surface milled to make them exactly parallel to the back plates and exactly 5mm proud of the main droupout body.
I placed my tubing order with Reynolds today. Here we go.
Bye for now.