The pulley is going to move no matter what. That is it's intended operational behavior.

Try a little blue loctite on the key screw before you turn it in and let it sit 24 hours before using it

 

In my experience, the RM decks and pulleys are not as beefy AND they rust more than the left-hand discharge decks.

Bent and rusty pulleys will cause extra jumping of the belt AND the rust will eat the belt in no time at all. The belt dust is telling a story. The worn OEM belt is telling the same story.

I don't remember if it was this thread or another, but the bellcrank, as it is called in the parts manual, has to freely move if it is on a welded to the deck pivot shaft.

If your bellcrank is one piece with a shaft, then you need to check the play in it. If it is able to move too much, that is a problem. Then you should consider welding a shaft onto the deck and using the bellcrank that pivots on the shaft.

As for the adjuster rod, the new rod is like a yoke and pin on the end that attaches to the front of the deck. You can have this made very easy or weld up yourself. You just need the same size, 5/16" I think, threaded rod. Then weld a strip of metal on each side of the rod and drill it for a pin. Of course, you will buy a piece that is longer than what you have.

Those are 2 changes that I have seen that Ingersoll did as the RM decks aged.

My other trick is to get the rust off the deck pulley. When I am doing this I am also changing the bearings. I tighten an old bearing into my vise and put the shaft into the bearing. Two bearings are better if your jaws are big enough. Then I put a sanding disk with 50-80 grit paper in my angle grinder. When you run the angle grinder all the way to the bottom of the V the pulley will spin fast. Then watch the surface and slightly tilt the grinder to clean the full surface. The top is tricky to do. You can't lift much and have to press into the v harder than the bottom.

A wire brush will not work on the scaled rust. And there is a risk with the grinder. But the way I see it is if it is rusty and needs cleaning, it needs cleaning. If you wreck it trying to clean it, well then you need a new one either way.

 

SSMEWING – I pulled my RM44 deck apart to remove the spindles and found the OEM C23949 belt I had recently replaced was worn down to the point which it no longer had any tension. All three spindles were heavily pitted and there was a lot of rubber dust around the front spindle. I pulled out all 3 spindles and cleaned the v groves in the pulleys with a 120 grit sanding disk on my angle grinder using an external variable speed controller to keep the speed low. The pulleys cleaned up well but the pitting is still obvious. I purchased a new OEM C23949 belt at the local dealer and installed it. The deck now mows better and I don’t see any rubber dust around the front center spindle. I also monitored the belt width with my caliper. After 2 hours of mowing, I saw minimal belt wear.

 

While cleaning up the pulleys in my RM44 deck I noticed a bit of a design deficiency in the internal belt drive. I'm sure some people might agree or disagree with improving a 30 year old design that has worked for 30 years. I acknowledge my decks internal pulleys are worn out and need replacement however I do not plan to replace them due to my RM48 rebuild project nearing completion.
The design deficiency I noticed is all about belt routing to achieve good belt wrap on the pulleys driving the blades. As an electrical engineer not a mechanical engineer I understand the power transferred has to do with the belt width, angle of belt wrap around the pulley and the tension of the belt.

Looking at the pulleys in my RM44 deck,
The center spindle pulley has about 110 degrees of belt wrap.
The spring tensioner idler pulley has about 90 degrees of belt wrap.
The right (discharge side) spindle pulley has about 180 degrees of belt wrap.
The left (inside) spindle pulley has about 160 degrees of belt wrap.
Adding all the angles up 110 - 90 + 180 + 160 = 360 = complete circle.

Belt slipping most likely occurs at front center spindle pulley. This spindle pulley has the least belt wrap and is driving two other spindles pulleys which both have great belt wrap. I've seen decks with spindle pulleys with low belt wrap but the spindle pulleys are being driven not driving two other spindle pulleys. The pile of rubber dust around my front center spindle in my post above confirms where the slipping occurs at.

 

While cleaning up the pulleys in my RM44 deck I noticed a bit of a design deficiency in the internal belt drive. I'm sure some people might agree or disagree with improving a 30 year old design that has worked for 30 years. I acknowledge my decks internal pulleys are worn out and need replacement however I do not plan to replace them due to my RM48 rebuild project nearing completion.
The design deficiency I noticed is all about belt routing to achieve good belt wrap on the pulleys driving the blades. As an electrical engineer not a mechanical engineer I understand the power transferred has to do with the belt width, angle of belt wrap around the pulley and the tension of the belt.

Looking at the pulleys in my RM44 deck,
The center spindle pulley has about 110 degrees of belt wrap.
The spring tensioner idler pulley has about 90 degrees of belt wrap.
The right (discharge side) spindle pulley has about 180 degrees of belt wrap.
The left (inside) spindle pulley has about 160 degrees of belt wrap.
Adding all the angles up 110 - 90 + 180 + 160 = 360 = complete circle.

Belt slipping most likely occurs at front center spindle pulley. This spindle pulley has the least belt wrap and is driving two other spindles pulleys which both have great belt wrap. I've seen decks with spindle pulleys with low belt wrap but the spindle pulleys are being driven not driving two other spindle pulleys. The pile of rubber dust around my front center spindle in my post above confirms where the slipping occurs at.

View attachment 62441

Al though I understand more belt wrap is important, I don't know how critical it is in this application. I would think, if belt slippage was a problem, vendors would be selling more of the under cover belt,, and owners, across the board would be complaining with early stall outs of their mowers.

Based off the 4 or 5 I've restored of these models,, the belts hadn't seen much for maintenance, let alone, removal of the top cover.

Perhaps, vendors could indicate if the lower belt gets replaced often,, or owners could indicate, if they replaced that lower belt often? This would give you an idea of the degree of problem?

I know, on the board here, we hear a lot about shredded belts,, but usually, it is the main top belt that owners are talking about.

 

Plan A
My initial plan was to add a fixed tensioner between the left and center spindles to add belt wrap to the center spindle. I mocked up a factory idler pulley C12251 (Stens 280-719) with about ¾" clearance to the center spindle and ¾" clearance to the tensioner spring mounting bracket. I drilled a 3/8" hole and filed the hole square with a ¼" triangular file. Next I installed a 1.75" grade 5 carriage bolt with an extra washer on the head. The extra washer prevents the square section of the carriage bolt from sticking through the deck causing the idler pulley not to sit straight up and down when the pulley is under tension. In order to match the height of the factory idler pulley, I added two ¼" thick washers (McMaster 91117A222) and a flat washer (0.050" thick?) to the carriage bolt. Next a factory idler pulley was mounted to the carriage bolt. I used blue loctite thread locker on the flange nut. A longer belt was obviously needed. I estimated the RM44 C23949 belt was 4" too short and that the RM48 C23950 belt I had was too long. From the belt PDF linked below, the internal RM44 C23949 deck belt is 76.5" (page 10) with an "A" cross section. From page 2 of the same PDF, an "A" or "4L" series belt is ½" wide. (RM48 C23950 is 81.625" long). I spent some time on Google figuring out the belt numbering for 4L belts. I ended up buying a 4L800 belt which is 80" long, only 3.5" longer than the RM44 C23949 belt. The 4L800 part number breakdown is 4L = ½" width, 80 = length in inches and the last 0 is the length in fractional inches? 4L805 would be 80.5" if it was readily available.

The 4L800 belt fits well with a slight increase in tension. The distance between the tensioner bracket and tensioner (where the spring is) increased from 3.78" to 4.23".
Initial results were quite good. The first time I engaged the deck at half throttle or slightly less my 16hp vanguard nearly stalled. Now I have to raise the throttle a bit above half throttle. The deck mows much better in deep grass too.

RM44 belt length PDF
http://manuals.casecoltingersoll.com/ServiceManuals/Belt Guide Manual 9-51590_watermarked.pdf

 

Problems with the setup-
I did notice that my belt is riding up the new fixed idler pulley to the top idler flange. The belt is approximately 0.2" higher at the fixed idler than at the left side spindle pulley. The belt then has to drop 0.2" between the fixed idler and the front center spindle pulley in a relatively short distance. The fixed idler pulley bearing is good and tight and the pulley is within 0.010" of level when measuring all 4 sides compared to the deck top surface. I also put a magnetic angle finder on the leveled deck and confirmed the pulley is parallel to the deck. A new idler pulley didn't fix the problem. I ended up adding a washer between my 0.25" spacers to put the fixed idler pulley on a slight angle. This fixed the belt tracking problem on the fixed idler. The belt now rides in the middle of the idler. I feel like this is a bit of a bandaid fix but its working. The fix survived a second mowing (2hrs+ per mowing) without any issues. I would appreciate any kind of feedback or parts suggestion.

 

Plan B-
I went on craigslist and looked at a whole bunch of mowing decks and studied the belt routing and belt pulley wrap. What I determined was the spring tensioner pulley could be moved toward where the spring mount is to increase the front center spindle belt wrap without adding another fixed idler pulley. The spring mount would have to be relocated. In the attached picture, the spring tensioner pulley would be moved several more inches to the left. I am just using a RM48 C23950 belt for illustration.
I also took a look through the old Case mowing deck parts manuals and also found examples of better front center spindle pulley wrap by moving the tensioner pulley in the same direction. I haven't made up my mind yet but I may do this mod on my RM48 deck instead of adding a fixed idler pulley.

 

I think you may be the only person having this problem.

The spring stretch in the first deck was not even close to enough. Belt was too long.

The picture of the RM48 is the same.

I have never had deck belt slippage when it is done as factory built with the right belt.

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I think you may be the only person having this problem.

The spring stretch in the first deck was not even close to enough. Belt was too long.

Its a new OEM belt with OEM pulleys. I haven't changed anything.

 

I don't understand how we got from a problem with the PTO to deck belt slipping to fixing a problem on the deck belt. What fixed the original issue???

 

Grinding the rust off the deck top center pulley and a new belt fixed the original issue. The rusted pulleys shredded the original belt to the point where it was thin and sank deep into the pulleys. When I attempted to clean up the deck drive pulley I found the internal deck drive belt shredded due to rusted pulleys which I also fixed.

 

I have found springs that ate longer than stock.

If everything is as it should be, meaning original, you should have to stretch that spring to just barely get the belt on. By this I mean you should struggle with the leverage needed on the wrench.

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I have found springs that ate longer than stock.

If everything is as it should be, meaning original, you should have to stretch that spring to just barely get the belt on. By this I mean you should struggle with the leverage needed on the wrench.

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The tensioner spring has a decent amount of tension. I quickly gave up on using a 12" ratchet in favor of a 24" breaker bar when installing the belt.

 

For both the X (LH) and RM (RH) decks, we sell easily 10:1 of the PTO drive belts vs. the deck internal belts.

We have many customers running 7+ full cutting seasons on internal belts ... some to almost never be changed. Easy up to 500 hours.

I suspect the origin of this concern was addressed correctly ... rusty and pitted pulleys will shred belts in no time, good tension or not.


Brian