Jackshaft Bent

[JoshTehSquash]

Hello everyone, this is the rear end of my yerf dog to which i have just welded bearing mounts for my jackshaft. My friend just bent the shaft while pulling out of the steep driveway, between the right pillow block and the small sprocket. He was trying to stop at the top of the driveway, but the kart started rolling backwards and he slammed the gas. I think that the inertia of the kart rolling backwards combined with the sudden jolt from the engine caused the bend. Did his mistake or a lack of additional bearings cause the bend? I don't want this to happen while offroading, but adding more bearings would be extremely difficult. I figured that having the sprocket close to the bearing would provide enough support without needing one on both sides. By the way, the shaft is 5/8 diameter and i have driven it on the street and up the driveway without any issues.

 

[2SlickNick]

That sucks.....
Maybe a 3/4" js would be better.
Also could you slide that axle sprocket and js sprocket left a little ( closer to pillow block)?

 

[JoshTehSquash]

Unfortunately no, it would hit the engine

 

[2SlickNick]

Well then 3/4" bar might be your best option.

 

[mckutzy]

If you want to keep existing sprockets, make a plate to fit across both current pillow block locations. Extend it a little ways over to where the axle sprocket is relocate the bearing, As to give the support right next to the axle sprocket.

 

[gman3850]

with that long of jackshaft i would see if you can add 2 more pillow locks at each end

 

[firemanjim]

Well, since you already went 5/8" (I woulda gone 3/4") , what you could do to fix the problem on the cheap,is to just replace the shaft with same exact size. Order 2 5/8 bearings while your at it. The kind you put in a front wheel. Get the kind with a snap ring flange added to it. Don't skimp out, buy the sealed bearing. Its only a little more, but way better bearing.
You need 2 short (1/2" long) sections of 1.625" tube with a .125" wall thickness, and some 1/4" plate cut into 2 triangles. The tubes get welded to the tip of the triangle. The triangle welded to kart frame, at the 2 bars going up. Slide new shaft in. You end up with bearings on each side of sprockets.
Crude drawing added for your viewing pleasure.....
Y'all thought Doug's phone pics where bad..... This pos tablet beats em.....

 

[JoshTehSquash]

Thanks for the advice guys. I though 5/8 would be just fine, being used on so many karts. I also read that less mass rotating = less power loss but i guess i should've sacrificed that for reliability with 3/4...

Jim, thank you for the great idea but i could barely weld the angle iron on square, much less something that sophisticated. And i don't have a way of cutting tube perfectly square besides an angle grinder and some luck

I dont know... I was able to move the sprocket a tad closer so hopefully that helps. I'll try not driving like my friend and see what happens tomorow when i drive it up some slopes. If it doesn't work out, i may just eat the loss and step up to 3/4

 

[firemanjim]

You just need support at the ends of the shaft. Measure the distance to the venter of the shaft, from the uprights. See if you add pillow blocks there, or something. The shaft will work, just needs help. It would be a lot cheaper to just add some bearings, because in the long run, youre gonna have to do it to the 3/4" shaft too..... Just add it to what you got and go sling some dirt ......

 

[JoshTehSquash]

Very true, i should have support on the ends regardless of diameter. I think i will use more 5/8 pillow blocks mounted on some flat stock.