crankshaft

[Jwestie15]

has anyone ever rolled their own, it would not be hard to turn and bore or balance plus you could have shiny alumium crank circles

 

[Frankenstein]

I'm sure somebody somewhere has done it, would be harder to balance out an aluminum one in that small size with the heavyish con rod and bits for the piston. Also if you have heavier flywheels you can keep the momentum in the engine better so lower rpms aren't affected as badly by load. Remember these are only 66cc motors...

 

[Jwestie15]

thats exactly why i want a lighter crank for more RPM potential, already have a sleeved cylinder and reed valve on the way from zeda with a 21mm oko, likely id take a moped con rod and piston and adapt them that con rod bearing being such and odd ball size and lack of thrust washers slightly pisses me off

 

[Frankenstein]

thats exactly why i want a lighter crank for more RPM potential, already have a sleeved cylinder and reed valve on the way from zeda with a 21mm oko, likely id take a moped con rod and piston and adapt them that con rod bearing being such and odd ball size and lack of thrust washers slightly pisses me off

Well.. Buy a crank, take it to a machinist and have him carb copy the parts you need, he likely has a press on hand that could remove the connecting pin from the 2 halves, then you can either keep it or get a working duplicate in the material you need. You'll have an already to spec con rod, and you'll know what bearing to look for and can add washers to your liking just make sure there's room between the checks for it. I'd say find out what thickness you want in the washers and have him machine away half that in just the area surrounding the pin hole so you can have a countersunk area for part of the washer area. He can press it back together and align the flywheels and you'll be good to go.

 

[MotorBicycleRacing]

has anyone ever rolled their own, it would not be hard to turn and bore or balance plus you could have shiny alumium crank circles

You will be the first which may be a warning sign...........

Aluminum flywheels are used but our motors doesn't have one.

Nobody gonna see the shiny circles, but maybe alumium is harder than aluminum???

 

[Frankenstein]

You will be the first which may be a warning sign...........

Aluminum flywheels are used but our motors doesn't have one.

Nobody gonna see the shiny circles, but maybe alumium is harder than aluminum???

I'd be most worried about where the small gear connects to the arm of the crankshaft, the torque could be too much for an aluminum shaft..

 

[Jwestie15]

im just suggesting turning aluminum weights the shafts would be steel and interference fit with key for added security

 

[Frankenstein]

im just suggesting turning aluminum weights the shafts would be steel and interference fit with key for added security

The key idea is going to be the best bet, even better that the machinist can also remove those shafts from the junk flywheels too just by putting in a lathe and cutting inward into the flywheel on its flat side. He can shave them down to the size that works and all that. You've got everything you need for the project except the billet aluminum and the guy to cut it!

 

[MotorBicycleRacing]

im just suggesting turning aluminum weights the shafts would be steel and interference fit with key for added security

Do it!
No high revving small engines [ or any others ] use aluminum cranks.........

The crank circles are revolving mass, not reciprocating mass.

 

[Frankenstein]

Do it!
No high revving small engines [ or any others ] use aluminum cranks.........

The crank circles are revolving mass, not reciprocating mass.

I guess the only advantage is it can accelerate quicker. But as you said (I did too) these are small, and small doesn't take much to get rolling.. If we were saying even just a v4 motor or anything with a substantially sized crankshaft the difference between steel and aluminum get to be more obvious, but then you are talking something like a hundred pound difference and cost to machine such a large piece of metal, for right now these crankshafts are utterly simple and so the price of a solid steel crank parts will be far cheaper than a precisely cut and assembled bi-metal assembly. Not to mention aluminum costs more in general than steel by volume..