I have a spring loaded tensioner with a roller from BMI and the bracket is 3/16" and works fine. I think your bracket is plenty heavy even if it's good aluminum stock. I made one for my DB with some cheap gavanized stuff and it was fine, as long as the tenision is medium it'll track fine I would think. Aint but one way to know for sure! :thumbsup:
i agree with MDB. what u need is more of a solid mounted idler/tensioner. what i would do is install a guard that comes up just over the chain that rides on the idler gear and mount the idler gear close to the rear sprocket so there is more of an angle on the chain going to the rear sprocket. Here is a pic that i drew the red is the chain notice more of an extreme angle after the idler gear. there is almost 200 degrees around the sprocket where the chain is making contact also see the black line above the idler gear? what u want to do is make a plate that uses the idler gear mounting bolt that comes up and over the idler gear to prevent the chain from popping off the idler gear. i also have a vid of my doodle bug to show you what im talking about but i am using the frame rail that runs across instead of a plate above the gear.
notice how loose i am running my chain to? no real loss of power with a looser chain. I have raced 5 times on 10th mile dirt tracks same chain and not once did it pop i have some friends that took my advice and since they installed that guard not once did they have a chain pop off
notice how loose i am running my chain to? no real loss of power with a looser chain. I have raced 5 times on 10th mile dirt tracks same chain and not once did it pop i have some friends that took my advice and since they installed that guard not once did they have a chain pop off
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korndog
The spring loaded tensioner should keep the slack out of the top run of chain while that run of chain is being held taunt while the engine is driving the rear wheel. However, it seems to me, that when the throttle is closed, and the rear wheel then drives the engine, the bottom strand will then be the taunt run of chain. At that time the tension spring will be overloaded which will allow the top strand to be VERY slack. Looks like a sure disaster to me....am I wrong?
The spring loaded tensioner should keep the slack out of the top run of chain while that run of chain is being held taunt while the engine is driving the rear wheel. However, it seems to me, that when the throttle is closed, and the rear wheel then drives the engine, the bottom strand will then be the taunt run of chain. At that time the tension spring will be overloaded which will allow the top strand to be VERY slack. Looks like a sure disaster to me....am I wrong?
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Coming from the master fabricator, that IS a compliment! Thanks YH.
Thank you for the advice and taking the time to illustrate. One of the issues I have is that of the scrub brake. The other is that I am running a smallish 53 tooth rear gear. If I set the spring higher or move the unit back for sharper angle of attack, I will hit the scrub brake.
Thank you for the advice and taking the time to illustrate. One of the issues I have is that of the scrub brake. The other is that I am running a smallish 53 tooth rear gear. If I set the spring higher or move the unit back for sharper angle of attack, I will hit the scrub brake.
Thanks Salt. I was trying to figure out what happens during all phases of a pass and my brain started hurting. That's why I posted this thread.
So, you seem to be saying that on power-off, there will in fact be significant load on the idler gear. I'm not sure I'm seeing it. Once the clutch is hooked up, I think the spring no longer increases the tension on the chain. Doesn't it set the tension prior to engagement and then hold there until disengagement?
So, you seem to be saying that on power-off, there will in fact be significant load on the idler gear. I'm not sure I'm seeing it. Once the clutch is hooked up, I think the spring no longer increases the tension on the chain. Doesn't it set the tension prior to engagement and then hold there until disengagement?
Any spring loaded chain tensioner will only work on the 'return' run of chain. In this case there is a 'reversing' load. In other words the engine, when the throttle is closed, is being 'overun' by the rear wheel sprocket rather than the engine sprocket driving it. So the 'return' run of chain is then on the top side and the 'taunt' run of chain is on the bottom run where the spring loaded tensioner is mounted. As the tensioner sprocket is only held in position by a spring the load imposed by the taunt chain will move it and allow the top run of chain to be very loose. I am not going to argue with anyone that has such a set-up and is useing it without a problem....so far. But it still stands: A spring loaded chain tensioner on a drive that reverses is about as well designed and as useful as a mop with a rope handle. It will only function in one direction.