Circle-S Drive tensioner question

[dr.peck76]

Very good advice Papee, thanks. I have provisions for battery mounting under the bow deck(there is the possible intent of mounting a trolling motor) and also under the drivers seat. I did have some of the loose components just setting on the deck frame in front to make weighing easier.
Should we move this to a new thread??? I'll try to start a build thread. with more pictures

[dr.peck76]

Just wanted to post a pic here of what my tensioner turned out to be. The assembly is from a Chevy truck, mid 90's and I had a wider aluminium sleeve machined for it to handle the wider drive belt.

[Corky]

Looks like round one with the tensioner is ready to be run...Supposedly my Circle S redrive is in transit so I'll post a pic of the tensioner to complete your original questions when it arrives...

[dr.peck76]

I installed the belt last night and the tensioner seems to be doing its job. I hand cranked the prop and the pulley doesnt seem to add any effort. It actually seems smoother. There seems to be a bit of flex in the unit itself that worries me. But I can't see how to stop it. I guess I'll know for sure soon, keeping in mind to keep my body parts away from the plane of rotation until I have some confidence. Lol. I have to admit I am having an absolute blast with this project!

[dr.peck76]

Update: I ran my set up last and have mixed feelings on how it is working. It seems to control the belt slap at higher rpm but at lower speeds it shakes like cat in the dog kennel. I'm thinking I need to crank up the spring pressure. Any thoughts?

[Doozit20]

I think kirk was having similar issues with his setup. Not sure how he went about resolving the issue though. Seems like I read about it not too long ago somewhere on this site...

[dr.peck76]

"Re: aerokirk's build
A warning to other builders using the Circle-S reduction drive ... I have been trying to figure out how much tension (if any) should be put on the idler roller as the drive belt begins stretching. I have found that the idler arm hammers on it's adjustment screw as the idler roller rides the back of the belt (which has small grooves). On a couple of occasions I have found the adjustment screw has come loose due to this idler arm hammering so I called Chuck & Bruce for some idea of how to adjust it. The adjustment screw is a fairly large 1/2" diameter bolt with a 3/4' diameter locknut."

Found the post. Describes exactly what's happening to me. I'm not sure adding another washer will help though....
You ever been driving down the highway and seen the rear wheel on a minivan bouncing like crany as they were driving? That's a broken shock. Nothing absorbing or controlling the rebound forces. Kinda like my drive belt. .... Just thinking out loud.

[aerokirk]

In trying to figure out the best setting of my tensioning roller I eventually set it where the roller began hammering on the adjustment bolt and caused it to loosen, fall out and go through the prop ($160 damage). I've now backed off on the tension and allowed for belt slap at idle so it doesn't hammer the tensioning roller at higher speeds.

There was supposed to be a re-design of the roller assembly but not sure if Circle-S actually followed through on it.

[Doozit20]

I believe there is a little difference between your tensioner and the circle S one. Ive never seen one of the circle S ones so if im wrong here I apologize but if im not mistaken the tensioner on there drive units are a simple idler pulley that adds tension through the tightening of a bolt and nut where you are using a spring loaded one. Personally I like the spring one you have. It reminds me of the tensioner I had to replace on my timing belt on my ford ranger....same concept but of course almost all if not all vehicles have a serpentine belt tensioner as I know all here are aware of

[dr.peck76]

You're right Doozit. (According to what I've seen on the Circle-S) I think what is happening is the spring is not stiff enough to keep control of the belt slap through each power pulse of the engine. Kinda don't of like that minivan wheel the spring pressure forces it down but then the tire has enough rebound energy to bounce back up until the spring loads again enough to push back down.
I'm not sure if I should loosen the tensioner to take less energy from the belt slap or tighten it to try to control slap. Or maybe a shock absorber is the answer..... I know for sure a direct drive wouldn't have this problem! LOL

[Doozit20]

Yeah direct drive definitely don't have those issues lol. I like the idea of a shock absorber. It would surely slow down the fast slap of the spring that simply bounces with no buffer. It will be interesting to see what you come up with. Im curious as to why a serpentine belt dont do that as badly...then again they are serpentine and not cogged

[dr.peck76]

I think the serpentine belts have a much higher load at low speed. Alternator, power steering pump, ac, maybe a fan.... All this is somewhat constant regardless of RPM, our props on the other hand spin very freely at low rpm.

I am thinking of a shock absorber, I just have to find the right one

[Doozit20]

I think a shock might help...at the very least it can then say it has been tried lol. You also have to contend with the trust of the prop puahing and flexing things where a car has none. Another interesting thing to add is I have an alternator mounted on the front side of my 084 and I too noticed considerable bounce at lower rpms and then it goes away at the higher rpm range. I truely just dont pay it any attention honestly lol. My new build im thi king of rearranging all that stuff..mounts and what not.

[Corky]

Is there a pressure adjuster on the idler ??? This is the tough part of fabing up our projects...Generally when the idler starts to "bounce" supposedly it's seen it's better days...The idler you're using looks identical to the idler on a GM engine in one of our vehicles and that's the diagnosis I was given when I questioned that situation...But now it's being used for something out of the realm of usage...All you can do is try...

[dr.peck76]

"...Generally when the idler starts to "bounce" supposedly it's seen it's better days...The idler you're using looks identical to the idler on a GM engine in one of our vehicles and that's the diagnosis I was given when I questioned that situation

Corky! More good information!! This makes me think again more spring force is required to properly control the belt slap. When compared to a serpentine belt the cross section is much heavier and the center to center distance is greater as well.

I've never have a tensioner fail on me in a vehicle but it makes sense, less spring pressure= less control..... I wonder if adding another spring to pull the lever into to belt a little harder would work???

Anyway, I improved the fastener for the setup I have this eveng, making it a bit more rigid and it doesn't seem to be too bad. I fired it up and went through the lower rpms and found that the tensioner isn't out of control as bad as I first thought. The engine is such a high compression that until it warms up, it does shake a fair bit. Once the heat soaks in things settle down and everything seems to get better. Anyway I think In gonna load it tomorrow and give it a bit of a work out at the lake. Ice is still on so I shouldn't have to paddle back to shore when something goes wrong! Wish me luck

[Doozit20]

Hope all goes good for ya. Be safe out there and take pics.

[Corky]

OK guys as promised here's the pics of the Circle S tensioner...Very simple set-up with the adjuster bolt doing all the work...Everything seems to be aluminum except for the roller and the obvious bolts and nuts....

[dr.peck76]

Great pictures Corky. It looks like a fairly robust unit. I'm glad you finally received it, great workmanship. It looks very strong radially to the shafts, but I'm wondering how is handling the thrust force? Does it use cylindrical roller bearings or deep grove singles, or is there a dedicated thrust bearing? Obviously the unit isn't an option for me , I'm just curious. Thanks