Chain making a popping sound /slipping on jackshaft setup

[jamessepck]

Hey guys, so i am very new to the whole go kart thing. Rebuild and old manco american cruiser for my daughters birthday and switched it to love axle. Added a jack shaft to keep the axle gear small because of the 13” tires. I have a 12 Tooth clutch going to 26t in and 10 out. Then to a 36t axle sprocket. Ive checked the alignment over and over and cant see an issue. The kart runs fine on the stand but as soon as its on the ground the chain starts popping at takeoff. I will add a picture of the setup and maybe some better ones tomorrow after daylight. Any help is much appreciated.

 

[mckutzy]

Offhand it sounds like a mix of chain types...
#35 for the clutch and maybe 40/41...

Or sprocket misalignment...

 

[jamessepck]

Checked the pitch on all sprockets. They are all 35s. Used a strait edge to lone up the sprockets but evidently im missing something

 

[Budget GoKart]

The jackshaft is flexing support it on both sides it should fix it

 

[landuse]

The jackshaft is flexing support it on both sides it should fix it

I wouls agree with this. Your jackshaft is just hanging out there with no support, an the flexing would then cause the chain to pop off.

I have circled the area in red.

Also.....your clutch looks quite far from the engine. Have you got a spacer between the engine and clutch? Maybe some more pics from different angles might help us

 

[itsid]

yepp.. what they said!

Since it'd be hard to add a support there,
you can just move everything closer together and shorten the free side of the jackshaft.

bring both jackshaft sprockets much closer together (if they're C-type sprockets they can touch and will still clear the chain with just a washer between them)
same gap for the inner sprocket to the bearing.

And that means you'll have to move the axle sprocket of course, but there appears to be more than enough keystock to do so.

that should already do the trick.

'sid

 

[jamessepck]

Good stuff guys, i will give that a try after work today and see how it goes. Thanks so much. Will update later this evening

 

[jamessepck]

So i came home from work and shifted the jackshaft and sprockets over as far as i could to shorten the run out on the free floating sode of the jackshaft. Lined everything up, tightened the chain, cranked it up, then it started jumping again now chain is loose. No sure where to go from here

 

[mckutzy]

You have to orientate the camera to landscape, so the pics show correctly...( I have reuploaded and re-orientated the pics)

With that being said...
What chain is popping off... the clutch chain or the rear chain?...

Edit: Off hand Im going to guess the axle is popping off....Due to unsupported flex in the middle of the shaft.

You mostlikely are going to need to add another pillowblock right underneath the frame. This will brace the axle properly, under load.

Also slightly unrelated... An added measure to keep you clutch on the shaft, use a bolt on the end of the shaft, secure with BLUE loctite.( Yes it probably has a setscrew, but this way itll stay for sure...Especially if it has an added in key, not an integral key)

 

[Karttekk]

"You most likely are going to need to add another pillowblock right underneath the frame. This will brace the axle properly, under load."

I was just about to suggest the same thing. Weld a bracket or brace under the frame and directly over the end of the flexing jackshaft to support another bearing. When you accelerate under load the shaft flexes and dumps the chain.

 

[jamessepck]

Sorry about the pics being turned, new to this! I see what your are saying guess i just wasnt thinking about that axle flexing. The chains arnt popping off but are making a popping sound which im aure would eventualy pop off. Thanks and it looks like i have some more fabricating to do!

 

[Karttekk]

The chain isn't staying down in between the teeth due to excessive flex under torque load. Something is wobbling instead of running true.

 

[jamessepck]

Alright guys ended up putting some heavier bolts and nuts on my jackshaft bearings and it held where it was supposed to. Let my daughter ride it in the yard and it did good. I do think the clutch is getting way too hot though. Actualy smoking! Should i may be looking into torque converters?

 

[JTSpeedDemon]

Try a bigger axle sprocket. I'm guessing a 44T or so should do you good. Maybe bigger.

 

[jamessepck]

Well the kart still has 13” tires and im afraid since she will be riding in the yard and on a dirt trail i was afraid the bigger sprocket would be digging a furrow!

 

[mckutzy]

Have you been oiling it every 2hrs of use???

Ratio sounds good.. almost what I have... And I have much bigger tire...

 

[jamessepck]

Literally just got the kart finished and got my daughter to drive it a while so havnt reoiled but jt hasnt been ran for two hours either.

 

[itsid]

Hmm.. nono.. I think you're close to success now..
you're not far off from the original setup now...

two things though:
1) it looks like the axle srocket is not inline with it's driving sprocket, it looks to have an inboard offset.
loosen the set screw on the axle sprocket and remove the clutch for a minute,
spin the jackshaft by hand as hard and fast as you can and see if the axle srocket tries to self-align. (they usually do)

2) the chain has too much slack; remove a link (maybe half a link if you think it's getting too tight) but as it's now especially the secondary chain is too long.

see the original 425 chain tightening instruction for reference:
https://assets.americanlandmaster.c...n-Kart/425426_chaintighteninginstructions.pdf

with proper chain tension and sprocket alignment I cannot imagine the jackshaft to flex any longer.
the axle might but frankly with proper chain tension that shouldn't be too much of an issue.
unless that's just a 3/4" axle in which case it indeed needs a third bearing close to the center somewhere

Oh wait.. the 425B was a one wheel peel kart IIRC...
so that live axle was an afterthought by either you or a PO...
you sure it's perpendicular to the kart's central axis and parallel to the jackshaft at all?

'sid

PS to remove half a link, you need to buy a half link and replace a full link of course ...

 

[jamessepck]

Man you know you karts. I added the live axle and im pretty certain everything is in line. I dont know much about karts but i work on cnc machinery for a living so i was lucky enough to take the thing to the shop and run a dial indicator down all the shafts and axles to make sure they are lined up. Also, i should have said in the above pictures, that is what the chains looked like after it slipped. I had them tight with about 3/8” slack before. My bad should have stated that. I will check that alignment on the drive sprocket tomorrow though. Thanks again everyone, really good stuff

 

[JTSpeedDemon]

BTW a 44T sprocket will not be anywhere NEAR digging into the yard with 13 inchers. I run 13s ATM, and I have good ground clearance with a 66T #35 pitch.