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Discussion Starter #1
Have a 40" square type commercial mower that I replaced the bearings in the drive head and painted it up to keep it from rusting. Drive is tight and has minimal drag and the two spindles, while not new, have low drag and spin freely. Added two new blades so it has cross blades like a 30".

Problem is it eats belts. Have new tension pulleys and new springs. Tension arms are not slack. Freshly greased spindles. Used 38" belts the first time and after they burned up used 37" belts which do fit but are tough to install (but keep tension longer). Using on a C8 in low axle gear high range in transmission and while it does load the motor when first engaging the drive, it mows and cuts well and the 7.6 hp handles it fine (pretty amusing since most 42" riders are at least 12-16 hp).

Any suggestions? Like the deck, and use it instead of the Craftsmen 42" 19.5 hp rider as it seems to give a better cut.
 

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Have a 40" square type commercial mower that I replaced the bearings in the drive head and painted it up to keep it from rusting. Drive is tight and has minimal drag and the two spindles, while not new, have low drag and spin freely. Added two new blades so it has cross blades like a 30".

Problem is it eats belts. Have new tension pulleys and new springs. Tension arms are not slack. Freshly greased spindles. Used 38" belts the first time and after they burned up used 37" belts which do fit but are tough to install (but keep tension longer). Using on a C8 in low axle gear high range in transmission and while it does load the motor when first engaging the drive, it mows and cuts well and the 7.6 hp handles it fine (pretty amusing since most 42" riders are at least 12-16 hp).

Any suggestions? Like the deck, and use it instead of the Craftsmen 42" 19.5 hp rider as it seems to give a better cut.
Have you used a long straight edge to make sure all your pulleys are level? Also on the same plane? Does the mower rotate easily with the blet installed? Sometimes a bearing can feel fine but tighten with any die load, (belt tension).

I too am amazed at the torque of these machines. Hope you get it sorted out.
 

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I would carefully inspect the v-groove area of all pulleys. It's very easy for them to get a little rust in there, and that makes them rough and hard on the belts. Even new mowers have this problem when some owners hose there decks down after mowing, and the pulleys sit till the next mowing and get rust on them.
 

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Using kevlar belts ?...Automotive belts wont hold up,anything using an idler pulley clutch needs a kevlar belt to last,and auto belts are different width and taper by enough to make them wear out and fail pretty rapidly.
Also a 37" belt doesn't have that much surface area,usually mower deck belts are twice as long--longer belt = more surface to take up load and heat..
 

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Discussion Starter #6
All belts have been Kevlar.
Pulleys on the spindles are very polished and have no rust. They do run warm! And I am running the mower w/o the top covers. Gear case pulley shows a little corrosion but it appears that the slippage is happening on the spindle pulley. Left side (from operator view) more than the right. Using one of the blades you can rotate the entire system with little effort with the PTO disengaged. No grease leaking from gear drive onto the belts.

Design of the mower only allows the use of 37-38" belts, one per spindle. Each belt only sees load from one blade set. Does not use a long routed in a circle belt like a sit down mower.

My only guess is that the spindles are dragging just enough to load the belts too much. But I can't understand why it mows so well, even in longer grass on the lawn.
 

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Have a 40" square type commercial mower that I replaced the bearings in the drive head and painted it up to keep it from rusting. Drive is tight and has minimal drag and the two spindles, while not new, have low drag and spin freely. Added two new blades so it has cross blades like a 30".

Problem is it eats belts. Have new tension pulleys and new springs. Tension arms are not slack. Freshly greased spindles. Used 38" belts the first time and after they burned up used 37" belts which do fit but are tough to install (but keep tension longer). Using on a C8 in low axle gear high range in transmission and while it does load the motor when first engaging the drive, it mows and cuts well and the 7.6 hp handles it fine (pretty amusing since most 42" riders are at least 12-16 hp).

Any suggestions? Like the deck, and use it instead of the Craftsmen 42" 19.5 hp rider as it seems to give a better cut.
I think I would try it with a single blade on each side like it was designed, and see if that makes a difference. You would think that would take some load off the belts.
 

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I just recently serviced one of these units. Agree to run the single blades as designed but also check the idler pivots for wear. This was my issue when breaking belts. So idler pulley was not running level. Replaced idler pivot and also switched to clogged NAPA belts and all has been fine.

Sent from my SM-G950U1 using Tapatalk
 

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Discussion Starter #10
1) Grass not overly long and has been dry.
2) Pivot posts for the adjusters are reasonably tight; not a lot of wiggle but the brackets that the idler wheels bolt to move easily.
3) Springs are new on the idler brackets.
4) Are the NAPA belts kevlar? Any idea of the part #? Cogged belts make sense as they do run cooler.
5) Not really sure why adding the additional blades would cause the load to go up so much on the spindles. Just running free the additional flywheel affect should help even out the impulse load on the belts. Most of the cutting is happening on the lower blade anyway.
 

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One thing you can look at, though you should notice the engine loading up. Put the whole machine on a level flat surface, and cut a block of wood just right so you have a feeler gauge, and check the blades for being level or a little lower in the front. If they are lower in the rear, the blade will have to cut the grass twice, doubling the load on the mower.

When I use the 40 inch commercial on my old L, I have to make sure the deck is leveled or tilted forward, or the tractor struggles to pull it. It takes all my tractor has to run that deck. I ended up modifying my 40 inch to make it level out, I am using the smaller 8 inch 4.80 tires. I think the later mowers used a larger tire and did not have this problem.
 

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Discussion Starter #12
The machine does tip back slightly, even though I have 16-6.50x8 snow blower tires on it. But the mowing load on the engine is really not bad, only starts to bog where the grass is really thick and/or too high.

Looking at 18-6.50x8 or 18-7.50x8 tires now. Don't want too big as the machine ground speed will climb and it works good right now in low axle hi range.
 

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If there grooves worn in the idler pivots, the pulleys will not run true. This was my issue with torching belts.

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The machine does tip back slightly, even though I have 16-6.50x8 snow blower tires on it. But the mowing load on the engine is really not bad, only starts to bog where the grass is really thick and/or too high.

Looking at 18-6.50x8 or 18-7.50x8 tires now. Don't want too big as the machine ground speed will climb and it works good right now in low axle hi range.
Try to judge where your skids are relative to the ground. The skids are what I had to modify on my mower, they would not let it drop enough to level out. Some dummy had cut them off anyway, so that helped make the decision to make new ones out of waterpipe, and bend them tighter so I had more room.

I have lots of washers on top of my front casters, only one or two underneath. And if you look at my mower underneath it looks a little ridiculous. I have only one or two washers on top of the blades against the spindles, and all the rest of the spacer washers are on the lower part to the nuts that hold the blades on. So my blades run very near the top of the mower deck, with all the shaft sticking out underneath to get a level 2 inch cut.

It cuts good though, I used it for years to cut 3 acres only using the old L mower, pulling me up hills on a sulky. I did have to slow for the very thick patches too.
 
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