Help needed with alternator Tensioner

[tvacc]

Hi all.

Sort of off the wall here. I will post pictures later to further image what I need.

I have an Elan with a alternator and toothed belt drive. The belt is just not tight enough. Makes a hell of a racket bouncing in an out of the grooves (I suspect that is what the noise is. I get a heck of a lot of thumping and bopping noise when I put a piece of wood between the alternator and my ear).

There is virtually no adjustment. Just a mounting hole and bolt. I need some sort of mounting adjustment slotted thing to allow me to put a little more tension on the tooth belt. Anyone have any ideas?

[billwill]

Are you unable to use the mounts built for the more usual configuration with a V belt?

Can't help much else without a photo of your configuration.

[tvacc]

Ok, hope this helps.

[rgh0]

Normally the top adjuster bracket goes of the middle bolt of the three yours appears to come from the top bolt. The belt is also normally a little longer so the alternator is swung out a little further from the block. You appear to have the reinforcing plate on the 3 front cover bolts which is good as vibration from the alternator can crack the cover ( especially in a race engine). Hard to tell from the photos but the top arm to the alternator appears it may be an integral part of the reinforcing plate - normally it is a separate component.

The original Lotus alternator bracket was a U shape section that spanned the thickness of the front cover and was located by the same bolt at the front and rear of the cover. There was then a flat arm welded to that U shaped section with a slot that lined up with the rear of the top alternator attachment point for adjustment.

Your current tensioner arm appears very thin and with the bends in it will be flexible and the alternator may be moving about. The arm will also eventually fatigue and crack at the bends.

.After cracking failures with the original Lotus bracket and many bent arm variations I now use a 3mm thick straight arm from the rear of the front cover centre bolt out to the alternator and then use a couple of spacers about 15mm dia and 15mm thick to fill the gap between the arm and the alternator top bracket.

For a road car with an alternator not sure the benefit of a toothed belt and the 1 inch wide belt sure takes up a lot of valuable real estate in what is normally a tight area in front of the engine.. I see 1/2 inch tooth belts fitted on race engines between the water pump and crank when no alternator is fitted as its easier to fit than a V belt when no adjustment is present.

cheers
Rohan

[billwill]

As you see from this diagram below, the standard dynamo or alternator pivots on its two bottom bolts and the top of the dynamo/alternator can be moved away from the engine to tighten the belt.

The top is then held in place by an arm which has a long slot in it instead of just a bolt hole, so loosening it at both ends and the lower pivots allows the alternator to move to tighten the belt to the desired amount, then the bolts can be tightened again.

At the bottom, the front bolt is a normal one, securing the front of the alternator to the bracket, but the rear one is a thin bolt with a sleeve over it, the outer dia of the sleeve is a sliding fit in the pivot hole in the rear plate of the alternator, so it pivots, but if the alternator metal expands a tiny bit, or the engine bracket expands, it slides along the sleeve instead of cracking the back plate of the alternator.



http://www.rdent.com/manuals/index.html

[tvacc]

Does anyone have a spare slotted adjustment arm?
Does anyone have a source for one. Sort of tough to make without the fabrication tools.

I could slot a piece of bar stock, but it will be tough with those thin top and bottom sections.

[pharriso]

Does anyone have a spare slotted adjustment arm?
Does anyone have a source for one. Sort of tough to make without the fabrication tools.
.

Talk to Ray at RDent, he sells a complete alternator kit, he may sell you just the bits that you need.

[tvacc]

no, He does not have a solution.

[memini55]

From what I see I would take the top bracket off and find a good shop with a mill and make a new bracket with a longer tab and have the tab slotted with the end mill. Not a home shop solution but would be an easy one with the right tools.. If your present tab is long enough take it off and have it slotted. You can find out by just taking the top bolt out and prying the alternator away from the motor to see what it takes to get the tension you want. With it being a toothed belt it does not need to be very tight.