Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.
5 posts • Page 1 of 1
I need to disassemble a dirt bike crank but the wheels are not solid steel. Much of the material is plastic to reduce crankcase volume. See picture, The black is plastic. Does anyone know what type of tooling is used to support one wheel so the pin can be pressed out? I'm thinking of a small horse shoe shaped piece that will then be supported by steel bars on each side in the press. Still, the width with be pretty narrow, only about 0.100" on the sides so not a great amount of support.
Is it a rebuildable item, crank kit available? Generally needs approximately 4 to 6 tons pressure to push out the crank pin and if you have only have 100 thou space and the compressive strength of the plastic is questionable I would be looking for a new crankshaft. 20 years I rebuilt many cranks for the Go Kart fraternity, those days we added epoxy to the webs to increase crankcase compression.
I don't see any complete cranks available. Rod kit is on order. They can be rebuilt but I'm just not sure what fixture is used to get them apart. .100 is side to side so a shorter reach for what ever i used for support. With a 180 degree rotation there is more like 0.200 but it means what ever support is used would have to reach deep into the crank. (this description must be hard to follow)
If preservation of the plastic is paramount, I would consider a carbide drill or EDM to cut the crankpin out. With one side and the connecting rod removed there should be a lot more surface available to press the other side out. I suspect the plastic might have originally been considered expendable.