PTO Alignment(?)

[genusCastor]

A couple months ago I bought a used Yanmar-Cub Cadet SC2400, has a belly mower and end loader.

I've had the mower deck off a couple times now, and I'm pretty well certain there's only one orientation of the PTO that allows the shaft to slip on. I see one groove on the deck (female coupler) that is wider than the rest, and a groove between two splines on the tractor (male end) that seems to be filled in making a spline that's wider than the rest, and apparently those two (wide groove and wide spline) must be aligned. Any other orientation and the shaft will not slide all the way on.

I discovered this anomaly the first time I hooked the deck back up. Yesterday, even though I understood(?) the specific orientation, it was still difficult to get it lined up. Can't see that well up underneath there. Prolly took me close to an hr to get that thing back on. Seemed like it anyway, I dint time it.

Does this sound familiar? I did some innerweb research but can't find anything about this. I'm thinking I could dremel whatever it is between the two splines on the tractor shaft and then it would go on in any orientation. I can't imagine any functional reason it would be designed to be specifically oriented, it can't be blade timing ... can it?

- djb

 

[oosik]

There HAVE been those times...... I get frustrated and go back in the house to have a cold drink of water. The ends of my PTO shaft will line up with the PTO stub on the tractor & implement in just about any way. As long as the splines align.

However - split the PTO shaft into two parts and there is only ONE way it goes back together. The actual shaft is square. One side of the square being longer than the other three sides. This forces you to reassemble the two halfs in one specific configuration.

BTW - I would not recommend doing any drastic grinding until somebody with more specific knowledge than I, can advise you. A couple of picture would certainly help.

 

[genusCastor]

In all my years of being around farm equipment I've never seen a PTO like this before. But I've never worked with bottom mounted PTOs, they've been all rear PTOs.

On one site, if I was reading it correctly, the reason for a "keyed" PTO is so low RPM pieces of equipment can't be accidentally hooked up to a high RPM PTO. If that is all this frustrating design is for, I'll be grinding out the fill between splines on the male shaft so it will fit the female coupler in any orientation.

- djb

 

[CobyRupert]

However - split the PTO shaft into two parts and there is only ONE way it goes back together. The actual shaft is square. One side of the square being longer than the other three sides. This forces you to reassemble the two halfs in one specific configuration.

When the PTO shaft splits into two parts (and normally telescopes when assembled) they need to be reassembled in one specific configuration ("in phase") so you don't get uneven speeds and wobble.
I'm not sure if this applies to OP's situation as it seems he's trying to put a PTO shaft on spline.
Picture would help.

 

[genusCastor]

When the PTO shaft splits into two parts (and normally telescopes when assembled) they need to be reassembled in one specific configuration ("in phase") so you don't get uneven speeds and wobble.
I'm not sure if this applies to OP's situation as it seems he trying to put a PTO shaft on spline.
Picture would help.
View attachment 613993

If phasing is the issue (as indicated by the drawing you posted) I wonder why phasing would be important on a bottom mounted PTO, but not a rear mounted PTO? I've never seen this on a rear PTO.

- djb

 

[genusCastor]

I'm not sure if this applies to OP's situation as it seems he's trying to put a PTO shaft on spline.

Just noticed the square PTO shaft in the pic. The shaft on this mower deck is, indeed, splined, not square.

- djb

 

[CobyRupert]

Just noticed the square PTO shaft in the pic. The shaft on this mower deck is, indeed, splined, not square.

- djb

...but are there universals joints (u-joints) that need to be connected "in phase"?
That is, are you connecting two sections of one (1) PTO shaft together?
I thought not. I thought you were connecting one yoke end of an assembled PTO shaft (hopefully "in phase" with itself) to tractor's spline?

Phasing is required between opposite ends of the PTO shaft (Shaft is required to be in phase with itself.)
No "phasing" is usually required between the pto shaft and the fixed tractor spline

Phasing is important on any PTO shaft (bottom or top) or drive line that has u-joints at each end.

 

[genusCastor]

Just noticed the square PTO shaft in the pic. The shaft on this mower deck is, indeed, splined, not square.

Maybe "PTO" is not even the correct terminology.

I'm referring to the shaft that drives the belly mower. It would look like pic below if totally removed, I am just dealing with separating the splined part of the shaft:



Sorry, and thanks for the responses.

- djb

 

[genusCastor]

...but are there universals joints (u-joints) that need to be connected "in phase"?
That is, are you connecting two sections of one (1) PTO shaft together?
I thought not. I thought you were connecting one yoke end of an assembled PTO shaft (hopefully "in phase" with itself) to tractor's spline?

Phasing is required between opposite ends of the PTO shaft (Shaft is required to be in phase with itself.)
No "phasing" is usually required between the pto shaft and the fixed tractor spline

Phasing is important on any PTO shaft (bottom or top) or drive line that has u-joints at each end.

Ah, OK, I see what you're talking about...

What I'm doing is not like connecting an implement to rear PTO. I'm separating the shaft. It may be that the PTO shaft of, for example, my bush hog, does have a specific orientation to slip the thing together. It's been a long time since I've had one apart.

So this means I'm stuck with having to get that shaft together in a specific orientation.

Thanks again. I think I got my answer. User error. :laughing:

- djb

 

[CobyRupert]

For others following along:

Yes, the splined male/female parts of the 2 shafts that slide together at the 7" mark have to go together so that the two universal joints at the end are "in phase" with each other (as shown).

The yoked ends of this shaft can then mount to the tractor's or mower deck's pto shaft (spline) in any orientation. Just like with a rear PTO.
Yes, I'd bet the 2 sections of your Bushhog's pto shaft can only be slipped together in one orientation.

Yep, you're stuck cursing for an hour.