One way roller starter clutch design. 1

[AsHRITH S]

Hello all,
I am looking for some inputs for designing ONE WAY STARTER CLUTCH for 2 Wheeler's. What are the resources that i can refer to carry on with design? Also,Is it a critical parameter which has to be addressed with deep understanding. In fact I am aware of how important inertia consideration in any design is. I hope someone will help me out knowing things in a better way.

 

[BrianPetersen]

Have you taken apart the one that any motorcycle engine has, to understand how it works?

 

[AsHRITH S]

Yes,I did. I am looking on how to apply inertia relation into it so as to know inertial effect on its performance characteristics.

 

[BrianPetersen]

Inertia of what - the starting motor, or the flywheel on the engine?

The starting motor generally has a very large gear reduction, often in two steps, before it gets to the input side of the one-way clutch. The starting motor had better have enough torque to crank the engine over at ANY point in its cycle. Otherwise, you just know that at some point the engine is going to stop in the worst possible orientation, and the starting motor had better overcome that, or else. The very large gear reduction ensures that the inertia of the starting motor itself will dominate ... but I'm not sure why you consider this to be so important.

The engine needs enough inertia in the flywheel to keep it running reliably at idle speed and then some. At this point the starting system is irrelevant.

In practice, during cranking, the overrunning clutch will release during expansion strokes and re-engage during compression strokes if the engine is experience half-hearted ignition or fuel delivery, until the expansion strokes get strong enough for the engine to keep running and thus completely overrun the starting clutch all the time.

What is your concern with the inertia?

 

[AsHRITH S]

Thanks for your concern BrainPetersen,
I am aware that the reduction is so large during cranking at the ring gear of starter clutch, to quote the reduction is in the range of 15:1 to 20:1. By this it is clearly indicated that starter motor inertia will dominate the flywheel inertia and helps in easy cranking of the engine.
But,my concern is to know the inertia effect on the Starter clutch which is mounted on the flywheel which in turn is rotated by the crank shaft after the engine is cranked. As we know, the real working of starter clutch starts here by free wheeling of the larger diameter ring gear and thus stopping power transmission back to the starter motor and prevent catastrophic failure of it.
Now, at this condition starter clutch will rotate at higher RPMs along with magneto/flywheel.Because of this rotation it will be subjected to inertial forces. Will this inertia affect the performance of the starter clutch in any way ?

 

[BrianPetersen]

Real world experience with millions of motorcycles built in the last several decades would suggest that the answer to your question is some combination of (1) no, and (2) whatever effect there is, has been dealt with.

On the one that I've had apart most recently, the spring-loaded rollers are in the part of the mechanism attached to the crankshaft, which means that as the revs go up (overrunning the clutch) the centrifugal action will act in the direction of throwing the rollers outward into their little ramps (against their springs, which are quite weak), which is in the direction of disengaging the clutch. Beyond some threshold RPM, I'm sure the rollers have pushed back against the springs far enough to be fully disengaged and not even touching the part that's driven by the starting motor. There's oil splashing all over the place in there, too.

 

[AsHRITH S]

Thanks a lot Mr. BrianPetersen for the best explanation which i have ever read.
I'll be looking forward for your continued support.