Mowing Mower Belt

marrt · May 27, 2003

Over the weekend, I decided to take one on the 60” mower spindles off to see if I could determine where all the grease goes. Before I mow my three acres, I always grease the spindles and it takes 10-12 “pumps” of the grease gun. That’s a lot of grease. I couldn’t determine where the grease goes but I did discover another problem. My belt is about to break in 5 or more places. In a couple places, the belt is torn all the way through except for the last 30 percent or so. I thought I would just go online and order a heavy duty Kevlar belt. However, the PT belt is ½” and 122” long. It is made by Jason Industries and has an “A 120” stamped on it. The problem is…I can’t find ANY A 120 belts, Kevlar or not. Anyone have a source on these other than PT?

My thinking is that the belt should be 5/8” (which are readily available) for this application. Unfortunately, the pulleys are ½”. Would a 5/8" belt work? I would consider changing the pulleys but that is a bigger proposition as I have no idea who makes the PT spindle or if I could get an aftermarket replacement. Any ideas?

Bob999 · May 27, 2003

I have an old catalog but in it Grainger carries your belt size--although not in Kevlar.

Sedgewood · May 27, 2003

MSC ( www.mscdirect.com ) offers two:

A Goodyear at $29.99

( Click here )

A Made in USA at $18.93

( click here )

I've also had good luck at NAPA

Sedgewood

Charlie_Iliff · May 27, 2003

Marrt:
My belt on the 72" also developed cracks on the v pulley side, I assume because of the idler pulley against the back. After the cracks developed, I mowed a few more hours without failure. Apparently much of the cord strength is in the back third of the belt.
I replaced mine with a NAPA belt.

Anonymous Poster · May 28, 2003

hey mart - just curious, how many hours did you get out of the belt?

marrt · May 28, 2003

Guys,

Thanks a lot for the suggestions. I ordered a Dayco cog belt from Granger. The cog feature should help relieve some of the tension on the inside of the belt as it goes around the idler pulley. 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…. The bottom line is that PT definitely uses the wrong size belt given a reasonable estimate for the HP requirements of the mower. That said, belts aren’t all that expensive so I guess it doesn’t matter in the long run. I know that some of the larger PT tractors have a commercial mower option. From the size of the belt enclosure, I’m guessing these mowers have double pulleys.

Ed, my tractor currently has 106 hours. The belt hasn’t actually broken yet and I think Charlie is right about most of the chords, and therefore strength, being on the outside of the belt. Therefore, the belt may last a while longer. I mowed two more hours on Monday anyway. I don’t guess it will harm anything if it breaks so I may wait until its convenient to replace it. Just want to make sure I have one on hand when the time comes.

Also, did you ever get around to fabricating that attachment adapter to use 425 attachments with your 1845? I’m thinking about trying to find a used 1430 or 1845 and would be interested in keeping some of my 425 attachments to use with the larger tractor.

Sedgewood · May 28, 2003

marrt: I know that some of the larger PT tractors have a commercial mower option. From the size of the belt enclosure, I?m guessing these mowers have double pulleys.


Ha! Yeah, right - they went all the way up to a single "B" section belt on my 6 ft roughcut mower. It broke in less than 50 hours - partly I think because I tightened it a bit thinking slippage might account for the poor cut. It didn't. And so far so good on the second belt (a NAPA).

Sedgewood

Anonymous Poster · May 28, 2003

Hmmm - not many hours - I was just curious because
I inspected the belt on the 425 before i delivered it to my brother in law - it had about 3/4 of a summer use on it and it looked good - I also wonder where all that grease goes - it seemed like it would take half the tube

I did build the converter plate - I have to get some photos and post them - I have done a number of things - getting behind posting what I have done - I have been really busy

I works good - it would be a pain if you used the attachment all the time - it would be better to just change the plate - I use it for attachments you only use a couple times per year
(and I share with my brother in law)

Bob999 · May 28, 2003

I know that some of the larger PT tractors have a commercial mower option. From the size of the belt enclosure, I’m guessing these mowers have double pulleys.


I have the 72" finish mower and it has a single "B" section belt!

marrt · May 29, 2003

I did build the converter plate - I have to get some photos and post them - I have done a number of things - getting behind posting what I have done - I have been really busy


I hear ya. I have made a couple mods as well and bought a tow behind mower. However, I can't find time to get some pics posted. I am interested in your design though. I still haven't figured out how to do it. I would also only need that capability for a couple of implements that I would use occasionally.

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