Mowing Mower Belt

Charlie_Iliff · May 29, 2003

commercial mower option. From the size of the belt enclosure, I’m guessing these mowers have double pulleys.


I think my 72" rough cut was referred to as a commercial mower that year. One belt only. I'd be surprised if they tried to put two on, since one breaking would invariably knock off the other one -- at least on anything I was running. /forums/images/graemlins/tongue.gif

Schultz · May 30, 2003

Maybe he's refering to the 3V type double banded belts. Some mowers like a Kubota I've seen use a belt that looks like a dual or side by side "A" belt with a conecting web between them. These belts are also comercially available, but you would have to change the pulleys to accomidate it.

Charlie_Iliff · May 30, 2003

dual or side by side "A" belt with a conecting web between them 

Sounds expensive. The double sided serpentine v belt on the John Deere 755 we have is about double the cost of the single belt on the PT. I'll go with the NAPA belt so far.

Bob999 · May 30, 2003

For those interested, Dayco has a very detailed build selection guide (in pdf form) on their site with lots of formulas to calculate the appropriate belt based on HP, torque, pulley size, etc…. 

I looked for this site but was unable to find it. I have a 62" ZTR mower which powers the deck with a single "B" section belt driven by a vertical pulley at the rear throught pulleys that change the belt to horizontal to drive the deck at the front of the machine. Your post made me wonder if this is not a proper application also and I would like to do my own calculations. Could you post a link to the information?

Thanks.

Charlie_Iliff · May 30, 2003

Bob:
A lot of machines use twisted belts to go from vertical to horizontal. Some belts are more flexible than others, so you do need to check the manufacturer's data.
Way back when, a Goodyear 3T was the only belt that would stay on a Corvair with vertical crank pulley and horizontal fan pulley over two idlers to 6000+ RPM. (In fact, both times the crankshaft broke the belt was still on.) The Paxton supercharger on that car had the blower pulley at apx a 30 degree angle to the crank pulley, with a full twist to reverse the rotation but allow the two sides of the belt to miss each other. Also good to 6000+. /forums/images/graemlins/cool.gif

marrt · May 31, 2003

Bob999, Here's the Belt Selection/Design Guide link I mentioned above: Belt Design Guide

Anonymous Poster · May 31, 2003

Guys I looked at a Steiner deck the other day and I could not believe what they had this belt doing - horizontal to vertical back to horizontal - front and back of the belt - and I know folks who have the Steiner and they are very reliable - so i guess you have to have the right

marrt · Jun 1, 2003

Retraction: Power-Trac belt is not too small.

Thanks to a headsup from Bob999, I need to retract my statement that the Power-Trac belt is too small for the 60" mower. Assuming the Gresen MGG20025BB motor turns about 3200 RPMs at 8 GPM, and creates 15HP to 18HP, the "A" belt should be fine (I originally "assumed" a much smaller RPM speed for the motor). In fact, at these high RPMs, a single "A" belt could handle up to 100HP!! I guess Power-Trac's reputation for over-engineering is still intact.

Attached is a picture of the belt I bought.

Bob999 · Jul 12, 2003

Re: Retraction: Power-Trac belt is not too small.

I opened up my deck today to clean and found that the belt was cracked all the way to the cords located on the outside of the belt. This deck only has between 10 and 15 hours on it. I think the problem may be that PT is not using a belt that is designed for the backside idler. The reference posted by marrt indicates that not all belts are designed for this application. An additional factor may be that the back side idler is not spring loaded so that any pulsation or shock load is not mitigated by the give of the spring loaded idler--putting additional stress on the belt.

johara1 · Jul 13, 2003

Re: Retraction: Power-Trac belt is not too small.

the big problem with the belt is running out of line. the deck is only 3/16 thick where the spindles mount,it will flex when you get into heavy grass. the blades that are on the 48"deck hit the sides in heavy grass, they where 3/8" too long.when they hit they left a mark that was 3/4" higher than the blade at rest. so i would think that indicates flex? my old gravely is 1/8" plus 1/4 plate on top of that. so it's twice as thick. one belt in 14 years and ihit things like bricks,rocks,and even a shovel tooth. the spindles are cheep too,they are not the quality i thought they would be. i don't think i would buy a deck again.the rest of the tractor is great