Alternator belt tensioning device

[Roberto]

Hello,
I have two alternators with belts of very different lengths. When I need to tension them I use a wooden hammer handle to move the alternator body and then tighten the locking bolt, the result is often far from perfect in particular for the shorter belt whose alternator sometimes outputs >70A.
I have seen some people have fitted a turnbuckle between the two bracket bolts, on other solutions seen on the web the turnbuckle is inserted between the two pulleys; on my alternators those methods cannot be used.
I would like some sort of variable length rod or device to be inserted inside the slots of the brackets (two red lines), then for example by screwing/unscrewing a nut increase its length as to move the alternator bolt until the proper tension is found, lock it in place, then unscrew the device and remove it. Does such device exist? Searching the internet gives links to additional belt tensioning devices which are to be fitted permanently, additional pulleys etc, and I have no place to install them.


Or could this sort of inflatable cushion be of any use?
Thanks

 

[mrangry]

Something like this maybe?

Alternator Tension 5 1/2in Adjustable Tensioning Rod Car Alternator Bracket | eBay

 

[fisherman]

I did my own, piece of studding, welded on where the slot is, right angle bracket to attach to the alternator wind out with a nut. A better one had the studding sitting in a tube attached to the engine block stud, nut welded to the alternator fitting, t bar to turn the studding. Lock nut.

If you google for volvo 240 alternator tensioner images you can see a similar idea.

 

[vyv_cox]

Should be easy enough to weld a nut onto the end of the slotted bar, then drive a bolt against the existing clamping bolt.

Alternatively it is possible to buy very small turnbuckle devices for this purpose. The alternator belt on my kit car is adjusted this way

 

[Refueler]

Replace the slotted arms with suitable turnbuckles .... but then you need ensure that belt is running true alignment.

But why not just get the correct belt for the job ??

And anyway - a belt should not be force tensioned ... it can be too tight in fact ... destroying bearings etc.

 

[Alicatt]

Mine will be getting a new belt and the alternator a new pully wheel as the one on it is worn out, it's on the list of things to be done before next season starts

New engine mounts will also be getting put on the boat as one rubber has completely detached and another is well cracked.

The list goes on...

 

[wonkywinch]

After many years fiddling with cars, I've never tightened any more than gentle pressure on a piece of 2x1 wedged between the dynamo (early days) or alternator and the engine block.

Correct tension can be judged by being able to rotate the belt along it's longest span by 90 degrees (not pulling it up and down as I see many people do).

 

[Martin&Rene]

The "inflatable cushion" (Winbag) works great, as it holds the alternator in the right position whilst you tighten the bolts. Money well spent. Get it here

Winbag Inflatable Air Wedge 160mm 160mm x 160mm - Screwfix

I also put a nut on the extension of the bolt to further ensure the alternator does not slip in use.

 

[Plum]

Hello,
I have two alternators with belts of very different lengths. When I need to tension them I use a wooden hammer handle to move the alternator body and then tighten the locking bolt, the result is often far from perfect in particular for the shorter belt whose alternator sometimes outputs >70A.
I have seen some people have fitted a turnbuckle between the two bracket bolts, on other solutions seen on the web the turnbuckle is inserted between the two pulleys; on my alternators those methods cannot be used.
I would like some sort of variable length rod or device to be inserted inside the slots of the brackets (two red lines), then for example by screwing/unscrewing a nut increase its length as to move the alternator bolt until the proper tension is found, lock it in place, then unscrew the device and remove it. Does such device exist? Searching the internet gives links to additional belt tensioning devices which are to be fitted permanently, additional pulleys etc, and I have no place to install them.
View attachment 169950

Or could this sort of inflatable cushion be of any use?
Thanks
View attachment 169952

This looks good Indigo Electronics Atomic 4 Belt Tensioning Device and I am sure you could make one yourself.

Www.solocoastalsailing.co.uk

 

[fisherman]

Belt failed one day, and took the half the fan blades off the pulley. The alternator kept shaking loose we crawled home in dirty weather. Only the pinch bolt then. Since then I made sure I had link belt aboard.

 

[MontyMariner]

This is my tensioner

 

[Roberto]

Thank you very much everyone! A lot of interesting solutions, once back to the boat will see what I manage to fit.

ps I do have a length of Link belt too, should the inside belt break it would be faster to replace.

 

[fisherman]

This is my tensioner

View attachment 170016

That was my rig up. I wanted the improvement, the studding in a socket at the bottom, with a T handle on the top end, thread in the block.

 

[MontyMariner]

should the inside belt break it would be faster to replace.

When I had two belts, I put a spare belt in place and tied off for use if the in use belt broke.

 

[Dino]

I picked up a zin plated bottle screw in my local engineering supplies shop. I cut the two eyes in half. I just put the bottle screw between the two pulleys and extended the bottle screw. Very simple solution but it worked 100%

 

[penberth3]

When I had two belts, I put a spare belt in place and tied off for use if the in use belt broke.

Good idea. That used to be the practice with big stuff where the whole machine had to be split to change the belts.