Jackshaft / Swingarm - Shared Pivot

#1
Out of curiosity... has anyone got a decent design that would allow for a jackshaft and rear swingarm to share the same pivot point? I've been working to redesign the rear end of my MBX10 to include an extended swingarm and have some concern regarding chain slack as it relates to monoshock flex.

I know i can just keep the swingarm pivot and the jackshaft arm close and figure out a sprung tensioner mechanism, but i figured i'd throw this out there in the offchance someone else has been thinking on this also.
 
#2
Since you posted under the "all models" heading, I'll respond and say there are several examples out there with other models. I am very familiar with the Taco 99 and 100 which shares a pivot point.

As you have correctly surmised, having the points different results in chain tension issues that need to be solved. Hope this works for you.
 
#3
Appreciate the response.

It's real close on the Taco 99.



Same with the Taco 100.



Not shared though.

What i'm looking for is something along the lines of the swingarm mounted on the jackshaft axle. This wouldn't really be an issue if the swingarm itself were short, however, this 17 inches with a 12" monoshock. More or less utilizing the MBX10 frame and turning it into a pseudo MX. Compression from on the monoshock with that leverage behind it is most likely going to result in a few inches of travel, so the closer i can get the pivots together the better.
 
#5
Ah, ok. So they're just using flat bar drilled to what is probably the same diameter of the jackshaft roller bearing.

Hah... i might have been overthinking this a little.:shrug:
 
#6
I like the Sears Roper where motor jackshaft and wheel are all mounted on the swingarm/motor plate and pivot in the middle of the frame. kind of like the later Norton Commando.
 

Motra

Active Member
#8
The Tote Gotes with rear suspension and the Mini Gote use a shared pivot point. I've heard that pivoting the swingarm on the jackshaft doesn't work very well but I don't know why it wouldn't.
 
#9
I had to Google MBX10. If you don't bob the rear of the frame, or widen it, you'll have to have the swing arm outboard of the frame. Not enough room for all the gear between the tubes. Unless you box a swing arm with increased width in the back.

What you do with the frame is going to determine how you set up the swing arm and js mount. Take a look at the go karts with the live axles for some bearing/axle hanging ideas.
 
#10
Swingarm is A framed with a middle shock mount for the monoshock. It narrows toward the front to accommodate the narrow rear end of the frame which, as is, still houses a 145/70-6 tire, sprocket, disc, and a set of 1" spacers. So there is a bit of room to play with... about 10" i believe. Forward arms of the swingarm are lengthened to the mounting point via 2"x1/4" steel bar stock.

Monoshock mounts to a reinforced spine beneath the seat... heavily reinforced... i'd hate to have a monoshock break loose into my balls...

It should fit alright and allow for remounting of stock sized tire width and allow for tire height upgrade in the future.

As soon as i finish doing my welds i'll put something up. Everything is still tack welded to allow for adjustment. Given that i've yet to get my parts for the jackshaft i'm a little stuck in progress until it comes in.
 
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