View Full Version : Question Re: "V" belts:

02-01-2012, 07:48 PM
I have an older single cylinder compressor i picked up and have pretty well restored it.
It runs quite good, but can someone tell me WHY i cannot get the "Flutter" out of the "v" belt when it is running?
The "Flutter" is mostly on the bottom of the belt which would be the return side from the motor to the compressor pulley.
Pulleys are lined up as perfect as i can get them in three trys, Belt tension is as it should be, (This is a new belt,) Is it the single cylinder "Pulse" from the compressor that is causing this or??

Any ideas on how i can eliminate the flutter, i just find it annoying?


02-01-2012, 07:56 PM
More belt tension.

You think thats annoying, My multi ribed belt squeaks like crazy untill the belt 'jumps' one rib

Then it works fine.... So uhh, I leave it with one rib 'jumped' out of the grooves. Im sure its really just an alignment problem but its SUCH a pain to get at those motor/compressor bolts I just can't be bothered.

Forrest Addy
02-01-2012, 08:17 PM
Use V belts with a notched inner profile; the secvtion designation has an "X" - "AX' , BX" etc. These are more flexible and efficient than the standard ones.

Some prefer the linked V-belts where the belt section is composed of stamps short links that hen connected forms a V section. They are expensive but very smooth running and effective. They have the advantage of being "connectable" through openings so spindle don't have to be dissassembled to install a new belt. They are not as effective in transmitting power for small pulleys as the notched inner belts.

So if one had needed to replace the belt on his turret mill, an AX would be the better choice because of the very small first position on the motor's step pulley than a linked belt. I need to do that but have been dodging the task for several years. Hey! It still runs on bottom speed so long as I don't load it to slippage. Whatta a lazy butt I am.

02-01-2012, 08:21 PM
You could just put an idler wheel under the belt, maybe even a spring tensioned one. That would be better than overtightening, which would cause excessive wear on the bearings and belt.

02-01-2012, 08:23 PM
Just a guess, but the load of a compressor is very erratic. The power required goes from very high to little or nothing and back again quickly. If the valves are letting some air back into the cylinder it may even be turning the pulley at some part of the up stroke.

I think that will cause the flutter as the belt becomes loaded and unloaded.


02-01-2012, 08:43 PM
Something I've done to combat that is to mount a piece of flat metal so it's parallel to, but not quite touching, the loose side of the belt. When the belt begins to vibrate it will start slapping against this metal piece which will dampen the vibration. The amount of time the belt rubs the metal is quite low, so there's no significant drag induced or wear on the belt.

In the unlikely event that the natural period of vibration of the attachment matches that of the belt, it could make the problem worse. You'd just have to change the size of it, or possibly add some damping felt to it.

The things you'd play with is the spacing between the attachment and the belt, and the position of the attachment between the motor pulley and the compressor pulley.

02-01-2012, 08:44 PM
Re: The suggestion of an idler pulley:

Possibly,, i did hold a wooden hammer handle up against the bottom belt and it seemed to take the flutter away nicely.

Belt tension did not change it much at all, i have the belt snugged up to 1/2 inch of deflection in ?? 10 inches.

02-01-2012, 08:53 PM
There is always going to be "flutter" due to one side of the belt being in tension and one not during operation. Any time you add an erratic load (your compressor), it only makes it worse. As stated above, there are various methods of solving it. Personally I would NOT crank up the tension, but rather do as darryl suggested with something flat almost, but not quite touching the belt.

02-01-2012, 08:54 PM
Very likely the resonant frequency of the belt is near the stroke rate of the compressor. Changing tension will change that some but changing belt length will change it a lot (much harder to do). Changing the weight of the belt will also make a difference.

02-01-2012, 09:08 PM
Pulley sizes are 3 1/2in dia. on the motor and 10 inch on the compressor.

1725 motor.

Pulley's were lined up with a steel straight edge.

Don Young
02-01-2012, 09:23 PM
I think many compressors do that and one solution is to install some sort of shield so you can't see it!!

02-01-2012, 09:28 PM
Don you could very well be right!

I think i have noticed twin cylinder compressor belts fluttering come to think of it.
I just find it very annoying to see, and wondered if it was the compressor pulse creating it.

02-01-2012, 09:35 PM
We have literally hundreds of pieces of belt driven equipment at work to maintain, I would go to a AX or BX belt on that small of a drive pulley diameter, I would try snugging it up a bit more also. I get kind of anal about belt tensions and with some patience, trial and error you should be able to get most of that wave out. We have belt tension guages also but rarely use them unless it's very large or specialized, even then those are general recommendations.

02-02-2012, 01:46 PM
V Belts can vibrate just like a guitar string when the load torque frequency is near the natural freq of the belt length. If tension adjustments can't move the nat. freq. far enough away to avoid excitation, the simple fix is an idler pulley on the loose side of the belt.

My air compressor uses one of those multi-rib belts. For 30 years the original motor ran it without significant vibration. I replaced the motor and it has a good deal more starting torque. If I adjust the belt tension so that it runs without vibration, the belt squeals on start-up. If I tighten up the belt to eliminate the squeal, the belt vibrates like hell. There is no sweet spot. Looks like an idler pulley is in it's future.


Bob Fisher
02-02-2012, 05:41 PM
I like Don's idea the best. Have you tried a link belt, I use them on everything, and an pleased with the results. Bob.

02-02-2012, 05:53 PM
Guys i think i'll go probably with an idler pulley i have a few sitting around.

re: Link Belts: I like them,, but bought an industrial grade "V" belt for this thing,--- The "Green" "Gates" belt.

Last night i was thinking about this vibration belt thing, and remembered seeing it many times on the drive belts on the mower deck of my riding lawn mower.

So, using an idler pulley it appears will take the flutter away, so i will try that.
I dislike things that vibrate or flutter, like this belt, much nicer to run something that runs smoothly.
Thanks to everyone that posted ideas and suggestions, much appreciated!!