OT- Ever had V-belts shrink?

[Gordon Heaton]

I put two automotive-type belts on a machine with a slip/tensioner engagement mechanism. The drive-to-driven pulley distance is fixed, the pulleys are dual groove cast iron. The belts went on easily and had plenty of slack when 'disengaged'. I ran the machine (an Ariens Rocket tiller) hard for 45 minutes, engaging and disengaging the drive many times, everything working well. Then it started to rattle & smoke. Now with the tensioner backed fully away, the belts are fairly tight! Almost an inch shorter in belt length. Crazy?

The orginal belts weren't available locally. They were a non serrated deep V profile. The replacement belts were also deep V, but serrated crossways to enhance flexibility I guess. They seemed to fit the grooves very well, and don't seem to be 'riding up' right now.

Any ideas?

Thanks.

 

[J. Randall]

No, but have had just the opposite, stretch .
James

 

[bob11x]

IMHO, a modern corded fractional horsepower belt should not shrink or stretch. All the belts we sell are Kevlar corded.
I would suspect a lower unit issue in the tiller causing a increase in the center to center of the drive + driven pulleys. Some tillers move the engine up to cause tension, maybe something there also.

As far as stretch, apparent stretch is usually caused by pulleys wearing the V too wide - common on mowers run in sandy conditions. This is a problem on self propelled mowers especially since the pulley is right above the blade stirring up sand and dust. MTD and Toro both require blade hub (pulley mad to it) replacements frequently in dusty conditions. Many customers try new belts, but the V is just worn too wide and the belt doesn't drive on the bottom.

The other thing that happens is the belt rolls over or comes off violently and breaks the cords internally. The it becomes a big rubber band, and does indeed stretch.

bob

 

[Gordon Heaton]

Yeah, I've never seen them shrink either. Seems impossible. Now that the sun's up, I'll go take another look. I hadn't noticed any slotting on the transmission mount but maybe its there. This thing is used in very sandy, dusty conditions. Thanks for the input.

 

[David J.]

Yes we have....I'm guessing one belt is a forward and the other gets
tensioned for reverse??
If they are slightly short, when they heat up in use, the reverse belt will
start to drag....more load...more heat...etc.
Tiller belts always seem to be odd ass sizes and because they are so
short ( usually 32-34 in range) you have very little margin to have
them work well. Sometimes you can go longer and slip a shim
of some kind under the engine to get it "just right".
As already pointed out a worm gear may be failing also, or just
low on oil.( if it's a worm drive)
Dave

 

[Gordon Heaton]

Thanks, Dave.
I tore it down this morning. The input shaft bearings (tapered roller) were loose, but not enough to change pulley spacing. Oil was checked before and after running. The transmission mount has 1/2" long slotted holes, but they were fast at the minimum spacing. The belts were almost tight! I'm sure I shouldn't use the serrated belts though. Too much friction. The pulleys did get really hot.
Still guessing I guess.

Gordon

 

[WHHJR]

Grain of salt... I have been told that rubber shrinks when heated.. This was in regard to rubber hoses.

I am not the xpurt but...

 

[David J.]

Gordon,
As a test, assuming that one of belts is for reverse, just leave
it off and till for a while to see how it goes. If every thing works
ok order the correct belts.
Dave

 

[petersen]

The kevlar belts are notorious for shrinking if you slip and
burn them

 

[Gordon Heaton]

David, there are two fwd drive belts (matched set) and one reverse. It won't disengage now because the two drive belts are so tight! I'm going to need all new (again) belts to make another attempt. In any case, after I started dissassembly to find out how to tighten the input (worm) shaft bearings I decided to take it all the way to inspect/replace bearings and seals.

Petersen, I had no idea that could happen. That's for sure what I did though. The adjustments looked fine to me, but I've decided I really need fully sheathed belts to minimize friction and heat buildup. I just could'nt find them in the right size the day I looked.

Many Thanks to all of you,
Gordon

 

[MwTech Inc]

Long.long ago in a different galaxy far , far away ...................


wait that's a another story

For a period in life I was an Ariens dealer for about 11 years.

Buy Ariens belts, they are not a standard belt. You will never find a belt that will work exactly right.

Lot of those belts were made in 1/8 th's lengths. 31 3/8 would be an example. Some had weird side angles, depth of sides etc.

 

[Gordon Heaton]

Oh man! I was afraid someone would say that! I've seen Ariens belts online for up to $70 each. (of course that wouldn't be for this application). The numbers on the original belts are legible, I just need to find an OEM source.
Thanks!

 

[waynes]

Yep,

Definately had belts shrink, but not V belts. Those flat types that go around the pants shrink on a regular basis.

 

[MwTech Inc]

Well. unless something has changed you may find the OEM source but they won't sell to you.

We tried for years to break into the source etc . even back then some belts were high. No luck. Strictly made for Ariens, period.

Those belts for the tiller were not that costly anyway.

Course you can keep trying other belts until you spend more money messing around then just buying the right thing

 

[Gordon Heaton]

OK. What I meant to say was find a supplier who stocks genuine Ariens parts. I've ordered them once before from a local implement dealer but that was years ago. I'll see if he can still get the right stuff.