Chain gets loose and then tight when rotating. Some specifics too...
The tight and slack were simultaneously observed on both sides of the chain going to and from the sprockets on the two jackshafts. I checked to see that the alignment between the two gears were correct and the chain was centered on the teeth. I found it OK.
There are two jackshafts I have for a huge lowering ratio I want to achieve. I still use two belts with pulleys but they are not giving any problem. There was a belt between two pulleys and one was very small diameter 1.7 inch. I had slipping so I went with chain instead.
Before I got a 28 tooth sprocket that I was waiting to be mailed to me I used two 18 tooth sprockets. There would be no assistance in lowering the ratio with that but I wanted to see how it would work.
It had no problem other than I was only getting a 14:1 ratio from the pulleys and belts and I wanted more for off road trail and hill climbing. I also intend to have slow speeds under 5mph with out having to pulse the throttle for parade events.
Then I got the 28 tooth sprocket and the 18 tooth sprocket with a new chain on the two 5/8 inch diameter jackshafts with keys installed. This now added to my lowering ratio. 14 * 1.5 = 21:1 ratio.
I heard the chain making a sound and found it got tighter and looser as it turned. I was only turning it by hand. I would not trust running the engine with it this way.
Just to see I went back and set up the two 18 tooth sprockets and I noticed it did the same but very slightly. Nothing looked out of round on the sprockets, but I noticed it got the chain the most tight only when the keyways were opposite facing away from one another. Also visa/versa, when the keyways in the two jackshafts where closest adjacent to one another the chain slackened the most.
This would have me believe that the sprockets even though not out of round are not centered on the jackshaft exactly. The set screw pushes on the key into the jackshaft’s keyway. This then I think makes the side of the sprocket with the set screw, by the keyway, move a slight amount away from the center of the jackshaft. This essentially makes it an effective out of round. It could only happen if the fit of the sprocket was loose on the jackshaft.
With the two 18 tooth sprockets having this tightening and loosening effect, it was not anywhere as pronounced as with the 28 tooth sprocket and the 18 tooth sprocket. I had to fix this as I would no way be starting the engine and running it like this.
I noticed that my new 28 tooth sprocket fit tighter, so I think it is not the problem. I have a new chain, but will eventually set up with using the same older chain that did not have as much problem when used with the two 18 tooth sprockets.
Further I have bought two new jackshafts and got a newer 18 tooth gear also, so I’ll be giving it a try later.
I wondered if some brand new chain that looks fine and is lubed and nice and flexible could accentuate the effect of the keyway and off centering. This maybe if the links were not exact to standard of a #35 chain.
The 28th tooth sprocket and the older 18 tooth sprocket together have that thing about the keyways facing one another or opposite one another; I wish to know if this has ever been observed before by anyone.
With the two new jackshafts I hopefully eliminate the possibly of bent jackshafts. It should mean the newer 18 tooth gear and the 28 tooth gear being better centered in relation to the jackshaft.
I'll know in the next couple of days when I can get back to trying the new parts and see if the problem is solved. Then to see what 22:1 with a 3hp Briggs can climb.
MT
http://motorbicycling.com/showthread.php?p=528756#post528756
The tight and slack were simultaneously observed on both sides of the chain going to and from the sprockets on the two jackshafts. I checked to see that the alignment between the two gears were correct and the chain was centered on the teeth. I found it OK.
There are two jackshafts I have for a huge lowering ratio I want to achieve. I still use two belts with pulleys but they are not giving any problem. There was a belt between two pulleys and one was very small diameter 1.7 inch. I had slipping so I went with chain instead.
Before I got a 28 tooth sprocket that I was waiting to be mailed to me I used two 18 tooth sprockets. There would be no assistance in lowering the ratio with that but I wanted to see how it would work.
It had no problem other than I was only getting a 14:1 ratio from the pulleys and belts and I wanted more for off road trail and hill climbing. I also intend to have slow speeds under 5mph with out having to pulse the throttle for parade events.
Then I got the 28 tooth sprocket and the 18 tooth sprocket with a new chain on the two 5/8 inch diameter jackshafts with keys installed. This now added to my lowering ratio. 14 * 1.5 = 21:1 ratio.
I heard the chain making a sound and found it got tighter and looser as it turned. I was only turning it by hand. I would not trust running the engine with it this way.
Just to see I went back and set up the two 18 tooth sprockets and I noticed it did the same but very slightly. Nothing looked out of round on the sprockets, but I noticed it got the chain the most tight only when the keyways were opposite facing away from one another. Also visa/versa, when the keyways in the two jackshafts where closest adjacent to one another the chain slackened the most.
This would have me believe that the sprockets even though not out of round are not centered on the jackshaft exactly. The set screw pushes on the key into the jackshaft’s keyway. This then I think makes the side of the sprocket with the set screw, by the keyway, move a slight amount away from the center of the jackshaft. This essentially makes it an effective out of round. It could only happen if the fit of the sprocket was loose on the jackshaft.
With the two 18 tooth sprockets having this tightening and loosening effect, it was not anywhere as pronounced as with the 28 tooth sprocket and the 18 tooth sprocket. I had to fix this as I would no way be starting the engine and running it like this.
I noticed that my new 28 tooth sprocket fit tighter, so I think it is not the problem. I have a new chain, but will eventually set up with using the same older chain that did not have as much problem when used with the two 18 tooth sprockets.
Further I have bought two new jackshafts and got a newer 18 tooth gear also, so I’ll be giving it a try later.
I wondered if some brand new chain that looks fine and is lubed and nice and flexible could accentuate the effect of the keyway and off centering. This maybe if the links were not exact to standard of a #35 chain.
The 28th tooth sprocket and the older 18 tooth sprocket together have that thing about the keyways facing one another or opposite one another; I wish to know if this has ever been observed before by anyone.
With the two new jackshafts I hopefully eliminate the possibly of bent jackshafts. It should mean the newer 18 tooth gear and the 28 tooth gear being better centered in relation to the jackshaft.
I'll know in the next couple of days when I can get back to trying the new parts and see if the problem is solved. Then to see what 22:1 with a 3hp Briggs can climb.
MT
http://motorbicycling.com/showthread.php?p=528756#post528756
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