Caroni Flail Belt Failure

[IslandTractor]

I did some more mowing with the solid tensioner set up on the TM1900 today. Ambient temp about 80. I set the cruise control to run the tractor a bit slower than I was driving last week so I did not bog down at all. Temps made exactly as I described in the earlier post. Measured after about 2 hours of mowing (first in a lighter field then in the field that I was bogging down in last week).

Cover: 155F
Top pulley central 206
Top pulley near belts 215
Bottom pulley 206
Gearbox 130
Bearing on non drive side 88
Belts on top pulley 200 (measured last...and top pulley was about 200 at that time too....temps drop quickly initially.)

It looks like when I mowed at a speed that did not bog the engine I got pretty much the same temp readings as I had with the spring tensioner. Again, my conclusion is that there does not appear to be any significant difference between spring and solid tensioner.

 

[IslandTractor]

Both Davitk and John861 have indicated that their flails run considerably cooler than the Caroni. Maybe it is just a design issue then and the Caroni, being Italian, is a little hot blooded. Mine mows happily at the temps I was recording so I will just continue. No evidence of belt wear at all.

 

[SPYDERLK]

Both Davitk and John861 have indicated that their flails run considerably cooler than the Caroni. Maybe it is just a design issue.

Not tensioned by idler Id say....
larry

 

[davitk]

OK, so I felt generous today and decided to make you Coroni guys feel better. While mowing last week I discovered mowing in reverse with my Hanmey flail handled the 6' tall canary grass better, less bogging down and it seemed to clear the cut grass better. So today I started out mowing in reverse, 20 minutes later I started to smell the belts. Of course I have smelled them before, just raised the mower to let the clippings discharge, and kept on going, the belts would cool down and everything was fine. Well, not today. Another 10 minutes into the field and the belt cover began to emit smoke so I pulled up to the shop, pulled the still smoking cover off, and..... .....guess it's time to order some new belts. And maybe next time not put Corona (no pun intended) in the cup holder

 

[IslandTractor]

Must be "flail belt flu" season.

I have thought about removing or better modifying the Caroni belt cover to get more air circulation. I may do one of my temperature monitored test cuttings with the cover off first to see what kind of temp difference I can measure.

 

[wstr75]

Found this Ph.D. research work on the Internet:
Section 3 is hard stuff what with all the mathematics but a couple things stand out:
1. "It is known from scientific literature that because of the
force difference between
tight and slack side, different elongation arises in the
belt sides, which causes belt
creep along the arc of contact of the sheave. With
increasing the load belt creep is
transfered into belt slip, which causes temperature rising. "
2. He has a chart showing pulley diameter directly correlates with temperature rise.
3. He speaks of pretension force as also influencing temperature rise but does not give scientific information regarding that experimental information.

http://phd.okm.gov.hu/disszertaciok/tezisek/2001/tz_en1886.pdf

Tough read, but has many of the answers to the questions we've been discussing. To this layman, it sounds like running the belts on the loose side, running the PTO on the slow side (to reduce the creep to slip point), switching over to aramide belts, using largest possible diameter pulleys and adding more ventilation are all good moves.

From reading this discussion and doing some side research, it seems a belt tensioner is a good news - bad news but got to have kind of thing. Running the belt between two pulleys is 360 degrees of flex per cycle. Adding a belt tensioner adds about another 40 to 60 degrees of flex motion per cycle and it is also occurring around a small diameter pulley, which, research says is a sure fire way for raising belt temperature. To me, it seems the best set-up would be just two pulleys that are tensioned by a spring-loaded jack plate pushing one pulley outward.

 

[John861]

Another point about my Ford flail. The belt cover is open on the backside, so there is considerable airflow. The Caroni's seem to be covered up with the exception of a few louvers. Probably safer, but would cause higher temps.

-John

 

[IslandTractor]

Here is a quote from a Gates product engineer regarding heat buildup. some of these points have already been made but I thought it would be useful to someone reading through this thread to see an authoritative statement.

" Question: What are the primary causes of heat buildup in belt drives?
Answer: A belt drive's operation generates both internal and external heat. Belt flexing as it moves around the pulleys causes internal heat. Slippage between, for example, a V-belt and sheave, creates external heat.

Pulley diameter, load, belt flexing, belt type, maintenance, ambient temperature and air cooling are among parameters that affect belt operating temperature. To counteract adverse effects on belt temperature, apply these guidelines:
-- Use the largest pulley diameter possible. This reduces internal heat buildup due to small-radius bending. Plus, it reduces belt tension and bearing loads, increases air flow, and increases belt contact area, all of which minimize belt slip and heat buildup.
-- Follow proper installation procedures. V-belts require a run-in period and retensioning to ensure proper seating and non-slippage.
-- Install a belt guard that allows good ventilation. If additional measures are necessary, use forced ventilation or finned pulleys to dissipate heat and reduce heat buildup.
-- Select a flexible belt type to reduce heat buildup. Synchronous, V-ribbed and molded notched V-belts provide good solutions to temperature buildup, particularly for small-diameter pulleys.
-- If heat is a suspected problem, use pulleys made of steel or similar materials that conduct heat away from the belt. Plastic materials don't conduct heat from the belt.

Todd Sellden is the power transmission product application manager for Gates Rubber Company.

This article appeared in the June/July 2000 issue of MRO Today magazine. "

After reviewing this, it does seem that the Caroni is running hotter than desirable for max belt life. On the other hand, the diminished belt life would still allow at least a couple hundred hours on a set of belts even when used exclusively in heavy mowing conditions such as I documented. At about 45 bucks to replace a set of belts that is hardly a disaster.

One thought from the technical bulletin is the possibility of adding fins to the pulleys to increase air flow. I wonder if just MIG welding a few fins to the pulley would cause mischeive or accomplish increased air flow. Another alternative is to add some more holes to the belt cover. It currently has about a dozen or so louver type openings on the front and back. I wonder about drilling a number of holes large enough to increase air movement but small enough to prevent fingers entering to maintain the safety factor.

 

[Reg]

This has been down my priorities list, but I'm about ready for an update.
I guess we all describe things differently and support people hear them differently, so we get different responses from support folk.
Thats OK, I used to be one, in a different technology.

Agri Supply sent me 3 new belts a while ago, they were so short that I couldn't get the tensioner bolt to the hole, never mind through it to get the nut on. They were tough to get on and I did consider trying them with the tensioner removed.
I have doubted the "not enough tension" approach that some folk have taken here.
One thing I don't particularly LIKE is tensioners on the back side of belts, it just seems on an intuit level that it causes more flexing than needed. A 3 sheave idler on the inside would be more expensive and reduce the contact length that the belts have with the driving and driven pulley, so I guess the roller on the back was a reasonable design/manufacturing decision.
I procrastinated it for a while and eventually called Agri-Supply again to talk about the short belts. We played voice mail tag several times and eventually they left me a message saying that they wanted to resolve this by sending me a set of each of the next two lengths, 47 and 48 inches.
Yesterday I futzed around with the 46 inch belts and actually DID mow a short strip with the tensioner removed. They smoked as soon as I got into some medium stuff, so I took them off.
I put the 47 inch ones on, they slipped on very easily and seemed way too long. Even with them relatively slack the adjusting nut is halfway down the threaded adjustment rod, so there isn't much adjustment left once they stretch out and settle in a bit.
OK, so I mowed a bit with the cover off and watched for smoke, listened for squealing.
All seemed well and standing back for a big picture view I'm becoming convinced that the increased length of contact around both pulleys is GOOD, it is particularly noticeable around the driving pulley. I have more "wrap", less tension and apparently adequate total "grip". Whats to not LUV ?

Then things turned a bit ugly.
{This is a different subject, but I think it illustrates that I DO HAVE enough total belt grip.}

The mower jammed and stalled the tractor, no surprise I'm running on the 1,000 RPM PTO with engine revs very low. It took me a while to figure there was no trash jammed in there, but a knife was flipped and jammed against the left end plate.
If you've never LOOKED closely at the 1900BSC knife and rotors you may not have noticed that there is an apparent assembly error of the left-most shackle/knife set.
I did look when I first got the mower, so I "corrected" it.
All the other knife/shackle sets look like book-ends, a Letter "L" back to back with it's mirror image. The left most one was assembled as two Ls the same way around.
It seems it needs to be that way, so that when the mower stops and the knives fall that leftmost one does NOT fall wrong and jam against the end plate.
So don't "fix" what ain't broke (-:

 

[IXLR8]

I put the 47 inch ones on, they slipped on very easily and seemed way too long. Even with them relatively slack the adjusting nut is halfway down the threaded adjustment rod, so there isn't much adjustment left once they stretch out and settle in a bit.
OK, so I mowed a bit with the cover off and watched for smoke, listened for squealing.
All seemed well and standing back for a big picture view I'm becoming convinced that the increased length of contact around both pulleys is GOOD, it is particularly noticeable around the driving pulley. I have more "wrap", less tension and apparently adequate total "grip". Whats to not LUV ?

Reg.. you have dusted off some memory cells.. years ago when I was in college (about 1974) I vaguely remember doing some calculations on belt slippage wrapped around a pulley. There was a tremendous increase in grip for a slight increase in 'wrap around' on the pulley. Dang... I may have to so see if I still have those books and can remember how to do the calculations. If they are at the house... I can have something in a few days.. if they are in storage... it could be months.