How to Tension an Alternator Belt?

[mfleming]

I have a B&C 60amp alternator on my brand new IO-360-M1B. Today I decided to tension the alternator belt. None of the manuals (B&C or Lycoming) give any hint on how to put the alternator in tension so the bolts can be tightened.

In years past, the only alternators I remember installing had a square face that would except a 1" wrench...that made it easy...tension the alternator, tighten the mounting bolts and go!

My first inclination was to use some sort of lever but on close inspection, the only thing to lever against is the engine case or other fragile bits.

So how is everyone accomplishing this without putting any of the fragile bits in jeopardy?

PS - All the other threads that started off by asking this question ended up quickly turning to 'how to check belt tension' and never answered the question.

 

[Robin8er]

I’m pretty sure I just pulled on it with one hand while tightening with the other. Not scientific at all, but to my knowledge I’ve never had it slip.

 

[GOFT]

Not really what you are asking, but ways to tension the belt.

https://www.lycoming.com/sites/defa...ernator Belt Tension, Methods of Checking.pdf

 

[mfleming]

https://www.lycoming.com/sites/defa...ernator Belt Tension, Methods of Checking.pdf

Yup, thats the answer all the other threads got.

 

[mfleming]

I’m pretty sure I just pulled on it with one hand while tightening with the other. Not scientific at all, but to my knowledge I’ve never had it slip.

Really, well I didn't think it would be that easy...I'll try that tomorrow and see how it goes and if I can get the 11 to 13 ft/lbs of break away torque..

But I'm still all ears to hear other methods...

 

[Toobuilder]

My go to tensioning tool is a bicycle tire iron levering between a convenient part of the case or ring gear and the alternator body. I have also used a piece of wood, screwdriver, claw hammer, and wrench over the years.

 

[Stoo]

A piece of 1x2 pine wedged between the case and the alternator worked for me.
Stewart Willoughby, 6

 

[rv8ch]

I’m pretty sure I just pulled on it with one hand while tightening with the other. Not scientific at all, but to my knowledge I’ve never had it slip.

Same here, but I installed a slightly larger pulley on the alternator, which would of course increase friction.

 

[RVFan671]

Me too

I’m pretty sure I just pulled on it with one hand while tightening with the other. Not scientific at all, but to my knowledge I’ve never had it slip.

Same thing for me. You don't want to over tension the belt anyway so don't get it too terribly tight.

 

[planenutz]

As above suggestions to achieve the required tension - but once you have the tension where you want it, spin the prop around half a dozen rotations and check the belt again. This allows the belt to settle into the groves and evens out the tension over the full belt.

 

[plehrke]

My go to tensioning tool is a bicycle tire iron levering between a convenient part of the case or ring gear and the alternator body. I have also used a piece of wood, screwdriver, claw hammer, and wrench over the years.

Just replaced my belt and used a steel bar between lower engine case and upper alternator body.

 

[Majorpayne317641]

I only use my hand to “tension” the belt. The way we operate these engines does not require anything special for this set up to work. Too tight will be a problem, belt slip may be a problem but only over a really long period of time and you will see the black powder around your pulley that is slipping. You may also not get the alternator output you desire.

I know this from personal experience in dealing with tensioning a serpentine supercharger belt to a 1000hp engine I have. Huge headache to keep that belt from slipping but also not so tight as to rip it to shreds. The times that this particular setup has issues is when I’m bouncing off the rev limiter and revving the engine in ways you would never do to an aircraft engine. That’s why I think it is not the issue some think it is.