Caroni Flail Belt Failure

[Eagleview]

Well until now i did'nt realise how puny that spring is . Theres no way that spring can keep the belts as tight as they need to be . If you can't keep your hand on a cover that is nowhere near the belts and has a supersonic air stream inside it to keep it cool , how hot are the belts getting ? After all the belts are made of rubber , and probably Chinese rubber too boot . I would strongly suggest making a solid threaded link , turn buckle or chain so that they can be adjusted correctly . It would be no different that the way you adjust the fan belts on an engine or any other thing with belts for that matter . I can see in my mind when that rotor strarts to load up and the torque of the tractor is kicking in , that idler would be moving away from the belts . If you want to test this , block the rotor with a piece of wood and put a big shifter on the gearbox spline and apply some torque , i'll bet the belts push the idler away without a lot of effort .

 

[SPYDERLK]

Well until now i did'nt realise how puny that spring is . Theres no way that spring can keep the belts as tight as they need to be . I can see in my mind when that rotor strarts to load up and the torque of the tractor is kicking in , that idler would be moving away from the belts . If you want to test this , block the rotor with a piece of wood and put a big shifter on the gearbox spline and apply some torque , i'll bet the belts push the idler away without a lot of effort .

The idler is on the slack side. I agree the spring is much too weak tho. The belts should be strung tight to carry that much power.
larry

 

[KevPH1]

Pulley misalignment could be a factor. If the belts are forced to operate on pulleys misaligned. The belt tend to twist and roll over in the belt groove.

Apply a straight edge cross the pulleys to confirm alignment. Adjust pulleys, as needed, on the shafts to improve tracking.

Maybe changing the gearbox oil to an semi-syn. or full syn oil will help in dealing with the heat issue. Good luck!

 

[IslandTractor]

Well until now i did'nt realise how puny that spring is . ...... I would strongly suggest making a solid threaded link , turn buckle or chain so that they can be adjusted correctly . It would be no different that the way you adjust the fan belts on an engine or any other thing with belts for that matter . .

I understand your point. I wonder however what the effect of using a solid link rather than a larger spring would be with regard to shock loading when the mower hits something. I presume that the spring loaded idle provides a measure of "slip clutch" effect and that it might be preferable to get the right size spring rather than a solid link. In your example of solid links in automotive serpentine belt systems, there is no need to allow for a shock load. On the other hand maybe the proverbial 3/8 inch deflection slack is adequate to allow emergency slippage on the flail. Does your flail have a spring loaded tensioning pully?

 

[IslandTractor]

I checked and measured the tensioning spring. It is a simple 1/8 inch (0.15 inches by micrometer) by 3 inches extension spring with standard machine hooks. I forgot to measure the diameter but it is about an inch. It should not be too hard to find a heavier duty replacement but I haven't tried yet.

I also tightened mine up by another inch and a half. I'll do some mowing and see what the effect is on belt guard temperature.

Also, the belt size appears to be a B43 17x1090 (I presume millimeters).

(Note: 1 hour of medium/heavy mowing left the belt cover too hot to touch for more than a couple of seconds even after taking up most of the adjustment on the spring.....Will look for a heavier spring first and also, per IronHorse's suggestion, a chain to replace the spring.)

 

[Reg]

They're tight enough on mine.

OK, so I'm running off the 1,000 RPM gear at 54% engine speed to get 540 actual RPM, so I'm not putting out a ton of power, but the belts are tight enough to stall the tractor when the mower jams on a thick bush stem.
If they were SLACK they would burn up, probably squeal on start-up too.

 

[SPYDERLK]

I checked and measured the tensioning spring. It is a simple 1/8 inch (0.15 inches by micrometer) by 3 inches extension spring with standard machine hooks. I forgot to measure the diameter but it is about an inch. It should not be too hard to find a heavier duty replacement but I haven't tried yet.

I also tightened mine up by another inch and a half. I'll do some mowing and see what the effect is on belt guard temperature.

Also, the belt size appears to be a B43 17x1090 (I presume millimeters).

(Note: 1 hour of medium/heavy mowing left the belt cover too hot to touch for more than a couple of seconds even after taking up most of the adjustment on the spring.....Will look for a heavier spring first and also, per IronHorse's suggestion, a chain to replace the spring.)

Have someone alternately rev the tractor while you watch the belts exit the driven pulley going toward the idler. Does one arc off differently than the others as it accelerates? If so they are not sharing equally. Could be a pulley circumference match descrepancy. One groove may not be the same as the others. Thatll cause some heat because they slip a little all the time.
larry

 

[pax]

Have someone alternately rev the tractor while you watch the belts exit the driven pulley going toward the idler. Does one arc off differently than the others as it accelerates? If so they are not sharing equally. Could be a pulley circumference match descrepancy. One groove may not be the same as the others. Thatll cause some heat because they slip a little all the time.
larry

Before I would conclude that the pulleys are mis-manufactured I would suspect the belts are not identical. I have a 7' tiller that I have used for close to 30 years now that uses 6 matched belts between the pto shaft and the gear box that is on the side of the tiller. The key to replacing these belts is that they need to be MATCHED. I had it explained to me that just because belts have the same number does not mean that they will be identical in size. There are slight variations in the manufacturing process and I had to always purchase belts that were made in the same manufacturing run, and thus "matched" to each other. I learned the hard way when I first relpaced the belts and just bought 6 belts. When I put them on and tightened things up I could immediately see that there was something not right. Some were floppy loose while some of them were stretched very tight. I went to the place I bought the belts and told them the problem. The guy kinda laughed and said I needed to have asked for "matched" belts and that would solve my problem. It took me a few different shops to find one that had 6 "matched" belts in the size I was looking for, but I finally found them and when taken home and installed, they fit perfect. The last time I replaced them I was working as a the parts manager of an ag dealer and ordered my own set of 6 matched belts from our supplier. In fact whenever I ordered belts of any size I would always request matched sets.

Just something I hope will save someone else some grief.

 

[Reg]

Visit Gates.com to read up on belts; Vee, notched, matched, & however else.
Same size in a notched version is more efficient, due mainly to less energy required to bend it.

Beyond some point MORE tension is harmful, both to the belts and (perhaps) to the shaft bearings as added side load.

 

[SPYDERLK]

Visit Gates.com to read up on belts; Vee, notched, matched, & however else.
Same size in a notched version is more efficient, due mainly to less energy required to bend it.

Beyond some point MORE tension is harmful, both to the belts and (perhaps) to the shaft bearings as added side load.

Notched is more efficient as you say, but they have to be run tighter to avoid slip. The V on the solid belt bulges as it bends around the pulley, aiding grip. Also notched belts crack when continuously flexed backward over an idler.
larry