Sprocket location

[GuinnessGuy74]

Ok, I need some help here. I am building an Arachnid with a 13hp GX390 clone and a TC40 converter.

Since I am using the TC40, I am running a jackshaft. Is there any consequence to putting the sprocket on the outside of the subframe closer to the wheel? I thought about running the shaft and pillow blocks outboard. If I run the jackshaft the other way, the sprocket will be almost in the middle of the axle. This worries me from a ground clearence perspective.

Figured some of you might know if putting the sprocket this far outboard on the axle as any load/torque conequences? Oh, at it a 1-1/4" solid aluminum axle, and 60T sprocket...10T on the jackshaft...

Thanks for any help!

Jim

 

[Doc Sprocket]

I generally tend to shy away from having the sprocket outboard. My reasoning for this is that it requires the wheel to be even further from the bearing's support and therefore increases the shear forces on the axle.

See if you can redesign things such that the sprocket ends up inboard, close to a bearing. Add another bearing or lengthen the jackshaft if need be.

 

[GuinnessGuy74]

I hear you about not moving the wheel, but as per the plans there is PLENTY of space between the wheel and bearing. You can see in the photo's of Austin's build here http://www.diygokarts.com/vb/showthread.php?t=9463&page=3

As you can see, there is plenty of room on the outboard side of the bearing. I am using 20" rear tres, so my clearence will be a lot less, but I could still get the sprocket pretty close to the outside of the bearing and still have room to spare. I hesitate to cut the axle down as the front end width is pretty wide. Perhaps a mod to the rear subframe to make it a little wider, but it's too late now....

Anyway, from a power perspective, does an outboard sprocket have any detrimental effects?

Thanks!
Jim

 

[theo]

It will be ok if you have the sprocket up close to the bearing, even if the sprocket is inboard, it should be close to the bearing.

 

[GuinnessGuy74]

Thanks Theo. I appreciate the help!

Jim

 

[Doc Sprocket]

but as per the plans there is PLENTY of space between the wheel and bearing.

That may well be- but it also wouldn't be the first time I was aware of potential flaws in these plans.

Anyway, from a power perspective, does an outboard sprocket have any detrimental effects?

Sure- more unwanted leverage on an axle end that may already be prone to flexing a bit much.

I'm not saying, "It won't work", and I'm not saying, "it WILL fail". What I am saying is it's a better idea to rework things to put the axle sprocket in a more desirable location, and to minimize the distance between the bearings and wheel hubs.

 

[anderkart]

If you go outboard, I was thinking you could give the axle more support by adding a second axle bearing on that side:

 

[Doc Sprocket]

Not a bad idea- might help stabilize things a bit. My concern is that I'm under the impression this is an off-road kart, and therefore the axle will take quite a beating compared to an onroad kart. I know I thrash the wee outta mine...

 

[anderkart]

Yeah I'd noticed he was building an Arachnid, just thought that pic would help illustrate my suggestion.

 

[GuinnessGuy74]

Thanks guys. I appreciate the help. In the back of my mind I was wanting to widen the rear. I now know I should have done it...

Too late now. I will consider welding an extension on to hang another bearing on each side to beef it up...

Jim