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Step 2Dummy axle
The first thing to set on the jig is to adjust the dummy axle to give you the correct bottom bracket drop.
The dummy axle is machined from threaded rod. I used 5/8" rod but you can use whatever is sitting in the remnant bucket at the local recycler. It should be bigger than 1/2" but smaller than 7/8". The bigger you go, the stiffer it will be, but if it's too big it might not work well with the smaller shrouded dropouts like the Ritchey socket dropouts.
Two recesses are turned into the rod at the appropriate distance apart. You'll have to make one dummy axle for each axle size. The end of the rod needs to be turned to press fit into the base plate - which conveniently is either an 8020 Manifold Plate (#2350) or a Base Plate (#s 2140, 2141, 2145) . The location of the hub centerline of the dummy axle will vary depending on how you make the bottom bracket post.
The general order of operations is this:
Base:
1. Center in the 4-jaw chuck.
2. Bore a hole to a convenient size smaller than the root diameter of the threaded rod you're using.
Axle:
1. Turn the press-fit section to size (about 1 thousandth over your bored hole, I believe) and part off so it's about .7" long.
2. Clamp the press-fit section in the chuck and rough out the closer recess.
3. Finish the recess to 10mm OD and face off the inside flat where the dropout will be clamped, so that it is located the correct distance from the frame centerline.
4. Flip the piece around and turn and finish the other recess. Since you flip the piece you can alway make your cuts close to the chuck so you don't have to turn it between centers. This is also handy if you have a mini lathe that wont fit the threaded rod through the headstock.
The clamping nuts are turned down so one side can fit into shrouded dropouts.
You could also modify this design to be adjustable over several hub widths by making the recesses wider and using multiple center sleeves. They would be held on center by drilling the sleeve and axle and fixing them together with a clevis pin.
It a (lathe-less) pinch, you could just start out with 3/8" threaded rod (or 10mm if you can find it) and use doubled-up nuts on the inside of the dropouts. The base plate would just be drilled and threaded for the rod. It won't be as sturdy as the above design but it wouldn't require any lathe work. You could always reuse the base plate later by boring it out to a larger size as shown in the original design. It actually wouldn't be a bad idea to have one dummy axle assembly built this way in case you end up building something with an asymmetrical rear end or an unusual rear hub spacing. See the second picture.
You can see in the last picture how the bottom bracket drop is set. A piece of a measuring tape from a Dollar Store tape measure has been glued to the end of the frame upright. A notch has been filed and inked at the center of the base plate as an indicator.
The dummy axle is machined from threaded rod. I used 5/8" rod but you can use whatever is sitting in the remnant bucket at the local recycler. It should be bigger than 1/2" but smaller than 7/8". The bigger you go, the stiffer it will be, but if it's too big it might not work well with the smaller shrouded dropouts like the Ritchey socket dropouts.
Two recesses are turned into the rod at the appropriate distance apart. You'll have to make one dummy axle for each axle size. The end of the rod needs to be turned to press fit into the base plate - which conveniently is either an 8020 Manifold Plate (#2350) or a Base Plate (#s 2140, 2141, 2145) . The location of the hub centerline of the dummy axle will vary depending on how you make the bottom bracket post.
The general order of operations is this:
Base:
1. Center in the 4-jaw chuck.
2. Bore a hole to a convenient size smaller than the root diameter of the threaded rod you're using.
Axle:
1. Turn the press-fit section to size (about 1 thousandth over your bored hole, I believe) and part off so it's about .7" long.
2. Clamp the press-fit section in the chuck and rough out the closer recess.
3. Finish the recess to 10mm OD and face off the inside flat where the dropout will be clamped, so that it is located the correct distance from the frame centerline.
4. Flip the piece around and turn and finish the other recess. Since you flip the piece you can alway make your cuts close to the chuck so you don't have to turn it between centers. This is also handy if you have a mini lathe that wont fit the threaded rod through the headstock.
The clamping nuts are turned down so one side can fit into shrouded dropouts.
You could also modify this design to be adjustable over several hub widths by making the recesses wider and using multiple center sleeves. They would be held on center by drilling the sleeve and axle and fixing them together with a clevis pin.
It a (lathe-less) pinch, you could just start out with 3/8" threaded rod (or 10mm if you can find it) and use doubled-up nuts on the inside of the dropouts. The base plate would just be drilled and threaded for the rod. It won't be as sturdy as the above design but it wouldn't require any lathe work. You could always reuse the base plate later by boring it out to a larger size as shown in the original design. It actually wouldn't be a bad idea to have one dummy axle assembly built this way in case you end up building something with an asymmetrical rear end or an unusual rear hub spacing. See the second picture.
You can see in the last picture how the bottom bracket drop is set. A piece of a measuring tape from a Dollar Store tape measure has been glued to the end of the frame upright. A notch has been filed and inked at the center of the base plate as an indicator.
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May 8, 2009. 7:34 AMajf342
says:
How wide did you make the recesses for the drop outs?
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May 8, 2009. 9:07 AM
drwelby (author)
says:
drwelby (author)
says:
I made them 3/8" wide.
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