V2Rocket

Has anyone successfully come up with a stronger solution for the AC belt turnbuckle tensioner thing?

I have a collection of them but I know they have a habit of snapping under high stress situations, or simply out of the blue.

If my current avatar is any hint, my tensioner is about to see some pretty big belt tension/stress and I don't believe the stock piece is up to task. With a supercharger at full-tilt and AC on, the serpentine belt could be seeing up to around 40HP going through it.

How can we "build a better mouse trap" here? I am thinking maybe making a piece that straddles both the turnbuckle mounts (the steering tensioner and the AC tensioner bolts on the lower balance shaft bracket) so that end is secure, but figuring in adjustability at the other end is the question...

So...ideas?


I'm thinking something along the lines of what is used on many Japanese cars, visible below. The perpendicular long bolt pulls the alternator into tension, and the bolts parallel with the alternator shaft lock it in place. Mine would have to be much more heavy duty than this but the concept should work!



Here's an even better example.

Jfrahm

I have never had a problem with a non-damaged stock tensioner even with a supercharger (although I run the factory belt tension) and I feel that most of the issues are due to people damaging the tensioner and/or mounts when messing around with the tension without properly loosening and re-torquing the pivot bolts and eye bolts in the right order. The tensioner has tons of mechanical advantage and could probably lift the car with a hand tool, it can easily break the mounts off or bend/break itself with someone just starts wrenching on it with mighty fists of ham.

That being said there is an aftermarket tensioner or two available already, at least one with heim joints that preclude the need for loosening the eye bolts. I like the stocker myself and keep an extra one or two on hand in good condition.

-Joel.

V2Rocket

What supercharger are you using?
The stock piece is sturdy but I've just seen too many that broke off at one of the eyelets. Also as you get to the ends of its adjustability the threaded bits get kind of wobbly.

Jfrahm

928 Motorsports with a double sided belt conversion.

Yes, people break the eyes off the turnbuckles and bend the heck out of the assembly because they do not use proper procedure when they adjust the belts. That way you can direct all the force from the turnbuckle, probably at least 1000 pounds, on the ends or the ears or whatever they did not loosen properly. You can eliminate half the effects of this stupidity with a heim jointed turnbuckle but a dumb wrench will still be able to break the ears or the mounts. It's cheaper and easier just to do the procedure right.

0 - Soak with penetrating oil
1 - Break loose the turnbuckle lock nuts, observing the reverse thread (You need to do this with the assembly bolted in tight to avoid bending stuff)
2 - Loosen the pivot bolt(s)
3 - Loosen the eye bolts
4 - Adjust

Tighten in reverse. The assembly should be bolted tight before the locknuts are torqued.

The other thing I see is people leaving some of these bolts loose, which results in parts falling off out on the road eventually. Might also be real tough on the tensioner strut.

Jfrahm

Also if the tensioner is stiff, just remove it and sort it out on the bench. Do not force it with it in place. You'll just bend stuff.

Good used ones are cheap and new ones are not terribly expensive, the Rennbay ones look good for a reasonable price. Before messing with your belts take a good look at both tensioner struts and order replacements if they look sketchy. And hose them with PB Blaster or whatever for a day or two before you attempt working with some possibly bent, stuck or rusty ones.

Carl Fausett

It is our belief that there just isn't enough belt-wrap on the alternator and A/C head and that's why you have to tighten the belt so much it breaks the belt tensioner.

So we added an idler pulley to the alternator mount. Then the pulleys have more belt-wrap and the belts do not have to be tightened as hard. No belt slip, either.

Details here: http://www.944performance.com/

V2Rocket

Nice solution.
My SC bracket has provision for a big idler under the blower pulley to increase belt wrap so I'm glad I'm on the right track.

As far as the purpose of this thread goes, I think I have come up with something in my head that should work very well for my purpose...stay tuned.

No more rounded nuts or sheared off eyelets for me.

tj90

Spencer - wondering if you came up with anything better. Im stuck in strut breakage hell. Im thinking helm joints from Mcmaster as you pointed out in the other thread.... I really like your thinkiing on the alternator tensioners in asian cars. Do you think female helm joints would be stronger and an advantage than the male ones used. Just dont know how the females would work with the turnbuckles.

Jfrahm

This was covered in the other thread but for future searches...

These struts are plenty strong enough. I bet they could lift 1000 pounds. If they are breaking you have other problems. Damaged block ears, AC compressor ears, pivot bolts, strut alignment, accessory alignment (washer in the wrong place) balance shaft alignment (vibration) etc.

The main problem with these struts is that they are so strong people break the block with them when adjusting the belts improperly (see procedure above). Or if they are lucky they just damage the $15 strut.

tj90

Thanks Joel. I think I have one of the issues that you mention causing the breakage.

V2Rocket

As an update here, I'm going to stick with the standard tensioner rod for "base tension" but am adding a GM "automatic-type" spring tensioner to the loop to deal with AC/supercharger loads...pictures whenever I get the f***er running lol

azbanks

I had an issue with breakage on mine and it turned to be a missing bolt on the back of my AC compressor. It was allowing the compressor to shift out of alignment when the compressor engaged and that twisted the housing enough to break the rod end. I replaced the missing bolt and all is well.

tj90

Azbanks - thats a good thought. I was told to look for that too. Makes sense since the rod breaks near the mass of the compressor. If its not bolted down, it will wiggle out there.Ill report back after I get under there and inspect. Im going to replace the mounts too so Ive got my work cut out for me.