Can I shorten a solid splined PTO shaft and re-weld?

Soundguy · Aug 8, 2014

nice pictoral, good job.

RichardDLee · Aug 8, 2014

Hi everyone,

Wow you've all given great advice, thanks.

Here is where I am at....

I have ground off the original weld and cut the tube at that point. Then pulled out the part of the shaft left inside the casting once cut.

That has left me with a lovely perfectly machined hole to set the cut down shaft into when welding it back on.

The problem is that the shaft has a slightly larger diameter than the hole, it's never easy is it!

Anyway, my uncle is now going to trim the shaft on a lathe so that it fits perfectly before welding it back in.

The balancing spoken of.. I understand the principle I think...... So I have to set the shaft correctly in the female section..... Then set the 2 yokes to the correct formation and then mark it so that I weld it back into the correct place?

Makes sense I think.

Thanks again everyone.

Soundguy · Aug 8, 2014

sounds like you are a weld away from having it handled.

Sodo · Aug 11, 2014

RichardDLee said:
The balancing spoken of.. I understand the principle I think...... So I have to set the shaft correctly in the female section..... Then set the 2 yokes to the correct formation and then mark it so that I weld it back into the correct place?

To clarify, it's not "balancing" it's "u-joint timing". Balancing and u-joint timing are two COMPLETELY different aspects of a PTO shaft. On balancing, there is so much slopping around on a PTO shaft I doubt balance is ever considered. I bet you can eyeball a shaft and decide if it's 'balanced' enough for PTO use.

For that matter you can probably eye-ball it (with a yardstick) and see if it's timed too.

RichardDLee · Apr 3, 2015

I thought I should finish this off.

I made sure the u joint timing was correct, then welded it up and it was all good.

I then refitted it to the tractor and tiller and it cut through clay like butter.

Thanks for all of your help.

Sodo · Dec 23, 2015

Ran across this great Youtube video showing how a pair of u-joints, when timed, produce a smooth output. Each joint cancels the pulsation of the other, perfectly. It also shows that if the input and output shafts aren't parallel there will be vibration (and lots of it). Most people know this from "lifting" a 4x4 truck. It's much less critical on a PTO shaft.

This video shows the effect of the input shaft and output shafts NOT parallel. You can't always control this on a PTO implement because the 3-point travels up and down in an arc, NOT vertical. And in many cases the top link is a variable length. But if you CAN choose a setting (3-point height, or top link adjustment) where the implement is operating with the implement shaft/yoke parallel to the PTO output shaft/yoke, this will be the smoothest operation, and everything will last longer. Bearings, u-joints, chains, sprockets, gearboxes. Everything.

For anyone cutting or extending a PTO shaft, the main issue in welding it back together is the u-joint timing. It's easy, and it's not critical to be accurate. You can be a few degrees either way. But only a few. A hand-drawn straight line on the shaft (before you cut it) is all the accuracy you need. Towards the end it shows what happens when a u-joint pair is "OUT of time". For example if a PTO shaft was lengthened or shortened and welded back together with the U-Joint pair "OUT of TIME"

Billrog · Dec 23, 2015

Why not just extend the ears on the tiller to get it farther away ?

jwmorris · Dec 23, 2015

Sodo, good video find. Any chance you have one for a double cardan joint and its effects on the misalignment?

Sodo · Dec 23, 2015

Sorry I don't know anything about double cardan joints. Found this by Googling "youtube double cardan joint" and YouTube offered a lot of videos about them.

k0ua · Dec 23, 2015

Sodo said:
Ran across this great Youtube video showing how a pair of u-joints, when timed, produce a smooth output. Each joint cancels the pulsation of the other, perfectly. It also shows that if the input and output shafts aren't parallel there will be vibration (and lots of it). Most people know this from "lifting" a 4x4 truck. It's much less critical on a PTO shaft.

This video shows the effect of the input shaft and output shafts NOT parallel. You can't always control this on a PTO implement because the 3-point travels up and down in an arc, NOT vertical. And in many cases the top link is a variable length. But if you CAN choose a setting (3-point height, or top link adjustment) where the implement is operating with the implement shaft/yoke parallel to the PTO output shaft/yoke, this will be the smoothest operation, and everything will last longer. Bearings, u-joints, chains, sprockets, gearboxes. Everything.

For anyone cutting or extending a PTO shaft, the main issue in welding it back together is the u-joint timing. It's easy, and it's not critical to be accurate. You can be a few degrees either way. But only a few. A hand-drawn straight line on the shaft (before you cut it) is all the accuracy you need. Towards the end it shows what happens when a u-joint pair is "OUT of time". For example if a PTO shaft was lengthened or shortened and welded back together with the U-Joint pair "OUT of TIME"