C-81 PTO Issue

[mikemc53 10]

Not sure if this is the right forum, but all help is appreciated.

 

A small problem with the PTO set up.

 

I just put the deck back on yesterday so I had to take out the lynchpin that goes through the PTO clutch (I may be using incorrect terminology here – don’t have the manual in front of me) to install the belt at the PTO.

 

Everything seemed to go fine, and I have done this before but, something must have gone awry because after a few minutes of cutting I noticed that the lynchpin was gone…couldn’t find it anywhere. I grabbed a larger cotter pin and used that in place of the lynchpin but it doesn’t seem to want to work properly. The blades will engage when the arm is at about ¾ forward, but they stop when the arm is fully forward (just as they do when it is pulled fully backward and the PTO is disengaged). There is a small détente where things seem to work best. The clutch does not seem to disengage when the arm is all the way forward, but the pulley (and obviously the blades) do slow down and then stop.

 

Does it seem like there is something that the lynchpin does that a cotter pin won’t do? I’m sure I’m missing something but it can’t just be a coincidence that when the one pin was replaced with the other, this problem started.

 

By the way, I’m not sure how the original pin ever fell out because it clipped over itself pretty solidly.

 

Thanks gang.

[nylyon-(Admin) 7,256]

Sounds like the retainer clip fell off or broke off of the shaft.  Does the center shaft of the PTO move in and out?

[mikemc53 10]

Sounds like the retainer clip fell off or broke off of the shaft.  Does the center shaft of the PTO move in and out?

Yes it does (move in and out). Wasn't sure if it was supposed to or not.

[nylyon-(Admin) 7,256]

I suspect that the cotter-pin is rubbing the bell housing.

 

Part #11 is that I am talking about. It should be visible on the shaft (part 12). If it's not there, that may be your issue.

[dsholler 54]

I had a similar problem with my 414, which I think has pretty much the same PTO setup. The symptom was that the PTO would stop rotating even when engaged, and if I tightened it up (by adjusting the screw (part 25 above) it would happen even faster. In the end, what I figured out was that the retaining clip (Part 11) would pop out of the groove in the stub shaft (part 12) and the PTO would move away from the driven disk.

 

I also noticed hte PTO was pretty hot after running. It turned out that the problem was the front bearing (part 8) which was running rough.  It just made a little noise and had a slight amount of friction when moved by hand, (you could not hear it when it was on the tractor) but that was enough... I decided to go ahead and replace all of it.. the stub shaft, front bearing and main bearing, the race and the oil seals... Fixed it.. there is a thread here on RedSquare that has step by step instructions about how to rebuild the PTO.... I will find and post...

[dsholler 54]

Here you go.

[Jeff-C175 7,199]

I was just looking up some parts yesterday because my PTO is also 'tired'.

 

I suspect that all the PTO bearings are pretty much the same, and as it turns out the bearing is the same as one of the spindle bearings on my mowing deck. Nope, scratch that, I was mistooken.

 

106947 is superseded by 109842, while googling these parts I found this vendor page:

 

http://www.theoempartsstore.com/pages.php?pageid=15

 

Perhaps there is some useful info there...

[Jeff-C175 7,199]

Not trying to hijack Mike's thread, hopefully my questions will help him also.  Before I rip into mine, I need to understand it.

 

What exactly is holding the PTO pulley assembly on the engine?  If I were to swing the PTO rod out of the way, and remove the brake assembly, would it slide right off the shaft?  That's how it looks to me!

 

The stub shaft has two clips on it, one on either side of the outer bearing, yes?

 

And this assembly is pressed into the end of the pulley housing, yes?

 

The engine shaft just slides into the race and needle roller?  Nothing other than the brake and rod holding it on?

 

When the PTO is engaged, the stub shaft is pushed inward toward the engine, engaging the PTO clutch. 

 

The only thing keeping the PTO clutch engaged is that itty-bitty snap ring?

 

This puts a LOT of thrust on that bearing, doesn't it?  I am surprised those bearings last as long as they do.  I don't think I would skimp one bit on this bearing at all...

 

Do I have all this correct?

[slammer302 2,155]

K

[dsholler 54]

Jeff,

If I understand you right, you are correct, but I am not sure why this puts a lot of pressure on the bearings? The front bearing is held into the bell by the rear snap ring. The front snap ring fits in the groove of the stub shaft and keeps it in position relative to the bearing. (the bearing cannot fit out the front, it is pressed in from the back). The rod is then attached to the shaft, which presses the bell onto the driven disk. This does not need to be a huge amount of pressure, just enough to hold it firmly against that disk. Generally, you start out with it light, and just screw the trunnion thingy on there until it doesn't slip when running your heaviest device (usually the mower). I guess there is some pressure on the front bearing, but all it is doing is keeping there from being torque on the stub shaft. The main bearing slides in and out on a race, and should have pretty much no lateral stress on it, other than that exerted by the belt itself (which is why you should not make it too tight).

 

In my case, the front bearing wore out, and the main bearing, while not perfect, was probably good for a while. I just chose to replace the whole thing at once, because I did not feel like messing with it again, especially because I needed to borrow some tools from a friendly car mechanic to get the bearings out.

[Jeff-C175 7,199]

I'm sure I've got some misunderstandings now... and probably won't fully understand it until I take it apart.

 

Based on what I could see in the diagram it appeared that the outer bearing goes in from the front, and bottomed on a 'land' in the bell.

 

I thought stub shaft had TWO clips on it, in front of and behind the bearing.

 

I think what you are saying is that the stub only has ONE clip on it.  Then it must be machined with a land on the back that prevents it from coming through the bearing.

 

OK, so the bearing goes in from the back.  Got it.  And the inner snap ring holds the bearing into the 'bell housing' (aka 'pulley housing').

 

Where I see the thrust on the bearing is when the PTO rod pushes on the stub, it is pushing the outer C-clip onto the center race of the bearing, which then pushes the whole pulley housing toward the engine and engages the clutch.

 

What I see on the front bearing is AXIAL thrust...  no?

[dsholler 54]

There is some axial thrust on the stub shaft, which is obviously transferred to the bearing, since that is part of the assembly that does not rotate. the land in the bell housing is inside, and the front bearing is pressed in from the front, so that axial thrust is spread across the entire side surface of the bearing, instead of just the inner race (is that what you call the inner surface of a bearing? I have no idea).

the one weak point in this as you have pointed out is the c-clip that holds the stub shaft in place... and I found that this was the bit that failed when there were problems with the PTO (It kept popping out of its groove, and much to my confusion, would pop back in when I disengaged the PTO lever... )

I know that the prior owner of my tractor had replaced this bearing before, but that was at least 8 and probably more like 10 years before I did it...so they do seem to last a while, if not forever.

[Jeff-C175 7,199]

In message #10 you said: (the bearing cannot fit out the front, it is pressed in from the back)

In message #12 you said:  the front bearing is pressed in from the front,

 

So now I'm really confused.

 

Were you talking about the needle bearing being pressed in from the back?  And the ball bearing from the front?

 

If so, I'm back to my original understanding of how the PTO goes together.

 

The BALL bearing goes in from the front and seats on a 'land' in the PTO pulley housing.

 

What holds the 'stub shaft' into the BALL bearing?  It must have a machined 'lip' that prevents it from coming through the bearing, is that correct?

[dsholler 54]

I would have to take mine apart to look at the inside end of the stub shaft, but the outer end is only pressed against the bearing by the c clip. you are right, in that this c clip is what is pressing the bell against the driven disk..

 

However, my question was why this would be bad for the bearing, assuming you do not really crank the thing down, the axial pressure is only that created by the PTO lever. Does that seem like too much to you? I guess I figured the bearing housing would be strong enough that this would be OK, especially as the pressure is on the inner (non moving) race at the edge, and is against the rest in the bell housing which (presumably, again haven't looked this carefully)  was pressed against the outer race (since it is spinning)

 is it any different than the bolt that holds a wheel bearing onto a (non rotating) axle?  (other than you take the pressure off it every once in a while) )?

[Jeff-C175 7,199]

No, of course don't take it apart!  I'll be getting to mine soon enough... gotta fix that wobbly hub first though.

 

Ball bearings are typically designed for radial loads where the balls ride centered in the groove of the inner and outer race.

 

The way this bearing is being used, it's pushing the balls up against the side of the grooves in the races, in in/out instead of side/side.

 

I'm sure it's not too much for the bearing though, since I'm the one in my machine is original and only now 33 years later making some noise and running rough.  It just surprises me that a ball bearing will stand up to axial thrust as long as these seem to!

 

There ARE ball bearings that are designed as thrust bearings though... (prop pitch motors come to mind)... the races are designed for the purpose [sorta like a 'lazy susan'.]and they can only be installed in one direction.  Installed backwards and they will come apart quickly. 

 

If the wheel bearings you are talking about are the automotive type, those are generally tapered roller bearings, and designed specifically to withstand the axial thrust they are subject to.

[Jeff-C175 7,199]

Can I link to pictures on the web on this forum?  Let's try it...

 

This is a view of the type of thrust bearing I am talking about:

 

 

Typical wheel bearing looks like this, similar to a thrust bearing, but angled:

 

[Jeff-C175 7,199]

BTW, the specs on that bearing are: 0.75 ID 1.781 OD 0.61 H

 

Believe it or not, Timken (and others) have a tapered wheel bearing set WITH a seal that is the exact dimensions. 

It consists of three parts:

LM11949 Inner race

LM11910 Outer race

LM11900EA Seal

 

The three parts together can probably be had for less than the Toro OEM bearing.  Perhaps this is because it is the same bearing set that is used on MILLIONS of HD motorcycles on the front wheel.

 

I've got half a mind (so my wife says anyway) to buy one and try it.  If it don't work, I'm out $20.

[dsholler 54]

Hey, try it.. I am sure the RedSquare community would like to know alternative sources for parts.. the stuff from Toro is kinda ridiculous. Unfortunately, i am not terribly mechanically knowledgeable, so I end up buying stuff from them all the time.

[Jeff-C175 7,199]

I am going to try it... might be a while yet because I'm still waiting on parts to fix that wobbly rear hub.  I'll document and post when I do.

[mikemc53 10]

Well my travel schedule has kept me away from this until yesterday. The c clip was out of the groove, and it also appears to be a bit worn and sloppy. Anyway, I put it back and squeezed it as best I could...voila...it works. I cut a good chunk of field with it and it stayed, but I really will need to replace the clip, soon.

 

Thanks for all the help guys. I have said it before but it bears repeating...best forum around!

 

Mike

[oldredrider 2,548]

Since the clip is loose, you will need to replace the stub shaft also. The groove gets worn and until you put in a new shaft and clip, the problem will return.