PTO Shaft Size

[Walter63]

I am replacing the pto shaft on a 38HP tractor (Antonio Carraro) driving a 60" flail mower. The current shaft "bottoms out" when I raise the implement, causing damage to the lock groove in the splines. According to my measurements, I need 3 1/2" of telescoping ability on the shaft to avoid the problem. This is not an extreme amount of travel, however the shaft is quite short. If I cut down the replacement shaft to work, it will have only 3-4" of contact between the two shaft halves when in working position.
Is this advisable? Any suggestions? (The lift arm holes in the mower have already been extended to move the implement farther from the tractor. There is no toplink used, as the lift arms raise the whole mower deck.)

 

[tjkadar]

I am not sure about your specific piece of equipment, but ATI recommends no less the 10" of overlap in the operating position for the 'Scape Rake. While the 'Scape Rake is not a flail mower, they are similar type devices in that they have a rotating mechanism that is parallel to the ground (though the 'Scape Rake more closely resembles a tiller). Others might have more precise recommendations.

What type of Antonio Carraro do you have? Any pictures? How do you like it?

We looked at the Carraros, but because of the lack of dealers (our nearest is about 1,000 miles away) and expense we went with another brand. They do look like very interesting tractors though... I am still intrigued by them.

 

[Soundguy]

I'm having a hard time visualizing the problem. The current shaft bottoms out.. yet you can't cut it because it is too short??

Soundguy

 

[slowrev]

Wow, How can the shaft be that short ? I think we might need a picture or something.

Ben

 

[MMM]

I'm not real familiar with flail mowers. It must really be a short shaft! Will a toplink adjustment give more room? You should have a lot of overlap between inner and outer shafts. Plenty to cut shaft without worrying. Maybe it's the sheild that's bottoming, not the shaft itself?

 

[normde2001]

Same problem here. I'm also having a problem visualizing this.

"(The lift arm holes in the mower have already been extended to move the implement farther from the tractor. There is no toplink used, as the lift arms raise the whole mower deck.)"

A picture or 2 would help.

 

[Walter63]

Thanks for all the replies. The existing pto shaft was not cut down enough. When the mower is lifted, the shaft contracts until it reaches its minimum length. This happens before the mower is 100% lifted, so the shock damages the pto splines at the lock pin.

To operate properly throughout the range of lift, the shaft needs to have 3 1/2" of telescoping ability between its maximum and minimum length. Its a very close-coupled machine, meaning that the lift ams don't extend a long ways beyond the pto spline. The mower has already been modified to move it back several inches, by moving the lift arm pins. But its still pretty close.

Toplink adjustment is a moot point. There is no toplink, because the mower lifts entirely with the lift arms. That design gives it more flexibility to ride out differences in grade.

There may not be an easy solution to this problem. I'm just wondering what a safe amount of overlap is for a pto shaft, and whether anyone has encountered this kind of problem before.

 

[slowrev]

I would assume that the shorter the shaft the shorter overlap required. Just remove no more overlap than you have to I suppose. And do not run the mower in the raised position.

Ben

 

[Soundguy]

I'd have to agree.. if we are talking about a shorty pto shaft.. with? 1' of range of movement.. then I guess if you can keep 3" overlapped.. you are good.. etc? is this what you are asking.

The range of motion on that machine must be pretty non-linear if it is too far extended to cut it down when in 'operating' position.. but 100% compressed when not 100% lifted.

My next guess is.. that if it cannot be moved back further. that you may have to rig a limiter on your lift quadrant to MANUALLY prevent you from lifting it past a point where it may damage itself.

Soundguy