Help with chain and sprocket issues

[Smitty484]

First post here looking for help on a scratch built bike frame is done now trying making it drive. I used all new parts bearings, shaft, everything's new. When I put the chain from rear wheel to sprocket on jackshaft it has a tight spot. Any help would be great. Thanks Matt

 

[ezcome-ezgo]

Welcome and please post some pics of what you are dealing with. It is worth a thousand words.

 

[Smitty484]

I'm trying to I only have an iPhone. You got any tips for that. Thanks matt

 

[Smitty484]

I can only do one at a time

 

[Smitty484]

Maybe I'm just over thinking it . Plus the gearing comes out to 7 to 1 I'm using 18" tires

 

[Smitty484]

I'm sure the frame isn't perfect ,very close but not perfect. But I figured if I do drivetrain last and line it all up as one it would be cool. This is my first try at this.

 

[machinist@large]

1) Find tightest spot on chain.

2) Adjust chain until there is ~1/16" of free play on one side of chain with it in that spot.

3) Rotate chain to loosest spot.

4) Check amount of play in chain; if it's less than 1/4" total, finish the build and ride the thing!!!!!!

 

[ezcome-ezgo]

So when you say "tight spot", what are you referring to? I think it looks like you're doing a nice job so far.

 

[Smitty484]

when I rotate the rear sprocket there is a point where the chain goes from feeling good to being almost to tight. 1/4" of play seams tight . I have 3/4 to 1/2" in one spot and 1/4" in another.
Is there a way to send a video ? Thanks matt

 

[mckutzy]

That's a cool looking bike... an another square chop... Only a few of us here have gone that rout..
Gearing is fine... I'm running that myself. (Check out my sig)
It kinda sounds like (assuming a varying tension is what your referring to) something is eccentric. Either the rear sprocket or the front; the jackshaft, or rear axle is bent.

 

[chancer]

Ok I have had this problem before, In my case...
The hub and Sprocket holes where not Exactly the same size. Less than 1/16 but not Identical.
So when I bolted them together all the play naturally falls to one side. [edit] yeah "eccentric"
They need to be centered.
This tiny bit of play becomes extrapolated (big word) it grows, as the sprocket tooths are larger than where the bolts are.
I put a little white glue, just to make the hub and Sprocket a leetle sticky, and make it easier to center.

I hope this helps, but I could be wrong. It happened once before! LOL

 

[Poboy kartman]

That's a cool looking bike... an another square chop... Only a few of us here have gone that rout..
Gearing is fine... I'm running that myself. (Check out my sig)
It kinda sounds like (assuming a varying tension is what your referring to) something is eccentric. Either the rear sprocket or the front; the jackshaft, or rear axle is bent.

My vote is the axle sprocket isn't completely centered in the mounting bolt holes...IDK?

 

[Smitty484]

Thanks guys for all the replies. I was thinking it was coming from the sprocket hub area. Plus the chain I have is 40 and it has a lot of room to slide around on the sproket was thinking 41 or 420 would be a better choice. All my adjustment for the rear wheel is in the jackshaft was thinking I need to make some way to adjust it more even . Was also thinking of making a chain tensioner.

 

[mckutzy]

Chain tensioning in a live axle fixed wheel base bike, is difficult at best.

In(our) your case, you'll need to either use a wheely(one with a skateboard wheel) chain tensioner, or come up with an Idea to move the jackshaft. Also keep in mind, if you move the jack shaft you have to move the motor( or at least have provision to allow it to move) and have space, so to allow to tension the front chain...

I spent about 4 months(or so....... almost a year) trying to come up with an idea to tension both chains easily. Not easy.....
Having right side drive makes this more complicated. Any questions more feel free to contact me on a pm and Ill go into needed details with you.

As for the eccentricity, shimming the space (while hub and sprocket are loose) between the sprocket, to keep it centered. A pop can or the like are good shim material.
Tighten evenly in a star pattern.

An idea that is relatively simple to adapt for use, is a "Harley" type of primary tensioner. Little plastic blocks that are adjusted to tighten the primary clutch/drive chain. A google of primary tensioner will show what Im talking about(if unfamiliar).

Over all this looks cool......very familiar.....HMMMMMM.........
I like it...


Edit: where abouts are you located...

 

[Poboy kartman]

George Clooney: "We're in a tight spot!".........."We're in a tight spot!!!"......We're in a tight spot!!!!!!"------From 'Oh brother ,where art thou?"

 

[chancer]

At least the Chain did not R -U -N -D -O -F -F!
Don't Mind Poboy "he's not Bonafide"
https://www.youtube.com/watch?v=pK3zSdpACp0

 

[Poboy kartman]

At least the Chain did not R -U -N -D -O -F -F!
Don't Mind Poboy "he's not Bonafide"
https://www.youtube.com/watch?v=pK3zSdpACp0

That's not the way I remember it....I kicked FreeRun.....errr....Vernon Walthrups butt and they told me to stay out of Wal-Mart!

Wait! You changed YouTube clips on me!

 

[chancer]

Sorry, this one was so short the address changed before I could copy it. So I had the wong won. had to go back and change it.
"and stay out of the Woolworths!"

You think thats all the woolworths?or just this one?"

 

[Smitty484]

I have a little adjustment here for the jack shaft . I think I mite have crap drive parts the sproket is deffanatly not running tru and this chain I got off of eBay is almost coming apart at some of the rivits.the engine mount isn't welded in yet so can do what ever there. Need some ideas to make adjusters on the jackshaft mounts that I pictured I was thinking some turn bolt push or pull kind of thing. Thanks matt

 

[chancer]

Here is an example of a push pull chain tensioner. Page 3 post 50
http://www.diygokarts.com/vb/showthread.php?t=5461&page=3

But the whole thread is good. It is from Mckutzy who posted above.
It is his way cool Square frame mini