jack shaft length question. Answers appreciated!

[wblupton]

I'm making a template out of wood to make a metal engine mount plate (so everything fits correctly) but I ran into a problem. I'm just wondering if the jack shaft can come out this far to reach the larger sprocket. I know the shaft goes under a lot of force but this kind of worries me due to the spacing of the pillow block bearings. Will this setup be okay?

I apologize for the horrible image quality but this is what I'm talking about.

 

[Doc Sprocket]

It might be okay, but it's not ideal. The chain should not be anywhere near tight enough to cause the shaft to deflect, but the torsional resistance created by pulling the chain may prove a problem. Best avoided. Can you extend the shaft all the way to the framerail and mount a bearing?

 

[wblupton]

Yeah that may just work but I would need a very long jack shaft. I'm already getting a 19" jack shaft that might do the trick, and I'm also going to widen the plate an inch or two to get the bearing closer. Thanks

 

[OzFab]

Is there any reason you can't move the axle sprocket in & shorten the shaft?

 

[mckutzy]

What is the dia. of the axle/JS shafts you are using.

And ya if you can move the JS sprocket closer to where is mounted, like wise the other sprocket the same.

 

[wblupton]

Fabroman, I would move the the sprocket in closer to shorten the shaft but too close and the axle sprocket will be hitting the recoil assembly. I moved the axle sprocket to what I felt like was a safe distance from the engine just in case if the chain throws (toystory mentioned this in my last thread).

Mckutzy, I'm using a 3/4" JS and a 1" axle shaft. I would do that but I would run into the same problem that I mentioned to Fabroman.

 

[OzFab]

Ok, fair point. What about runnung them on the other side of the engine?

 

[wblupton]

I have thought about it and tried setting it up but I ran into a lot of clearance issues again. I may be able to show you some pics of the setup and you could give some of your thoughts. Also, I been trying to keep the axle slightly behind the engine for better weight distribution. I don't want to be popping wheelies!

 

[mckutzy]

I looked on the other threads of yours to see the whole project. I forget what people build sometimes and dont remember who is who.

I see what it looks like now. Maybe extend your mounting plate over an inch or two, and mount the pillow block near the end of that.(properly supporting that underneath of course) You might need another aswell in the middle, just to keep things supported.

 

[spyder1968]

well said Mckutzy !

 

[wblupton]

I agree with spyder. thanks!

 

[mckutzy]

Thanks guys, Im here to help.

With a wood "template" it always helps, make all the mistakes you want before you cut metal.

Another Idea I just thought up of, If isnt a big problem to get a longer jackshaft, why not use on pillow block on the frame opposite of the motor, shim it to the level of the motor plate(if the frame is lower than the plate, might have to move something else) and keep the other blocks in there current position. The small/large sprocket could be spaced between the remaining width, allowing for a good guard to cover and easy access to that area.

 

[Doc Sprocket]

Another Idea I just thought up of, If isnt a big problem to get a longer jackshaft, why not use on pillow block on the frame opposite of the motor, shim it to the level of the motor plate(if the frame is lower than the plate, might have to move something else) and keep the other blocks in there current position. The small/large sprocket could be spaced between the remaining width, allowing for a good guard to cover and easy access to that area.

I coulda sworn I suggested that... Oh wait, I did!

Can you extend the shaft all the way to the framerail and mount a bearing?

 

[mckutzy]

Im sorry I didnt see that initially. Yes you made the better point.

OP what was the reason why you couldnt get/want a longer shaft like what toystory_4wd had said in his the second post.

 

[wblupton]

Well at the time I was not expecting this kind of problem and I honestly thought 14 inches was more than enough, until I ran into this "clearance" problem. I guess you win some and you lose some