PTO Shaft Length - minimum overlap etc

[aesmith]

Hi,

Something that's been bugging me for a while, the shaft for the mower is a bit too long. It doesn't close right up, at the shortest position it is still extended by just over 30mm. But it only has enough clearance to attach or detach from the tractor when the mower's right on the ground when there's 65mm extended. I can't do it when the mower's on the trolley I made for storage.

So far I've been working around it by connecting the PTO before the lift arms, so I can push the mower away a little.

So ideally I'd want to shorten the shaft by around 40mm, but I want to make sure the reduced overlap won't be a problem.

Currently the inner part is 770mm long, extended length is 835m, minimum overlap is 705mm, or 27.75". Or you could say the overlap is 84% of the length.

If I take off 40mm it becomes 730 long, minimum overlap of 625 (24.60"). Around 75%.

Any concerns? It's a 25HP tractor and a 4' rotary mower (what we call a "pasture topper")

Thanks.

 

[ptsg]

I've read on manuals that the minimum overlap is about 150 mm. Personally, I like to have as much as possible without any bindings or issues connecting the PTO shaft.

You'll be perfectly fine with the amount you need to cut to make it easier to work with. 600mm+ is plenty of overlap.

 

[aesmith]

Thanks. I read the 6" recommendation but don't think I'd be happy with anything remotely that short, give were taking about near to 36" between the UJs.

I saw another recommendation that the shaft shouldn't extend by more than 30%. If we're taking about the tubes then with 40mm cut off I have a closed length of 730, max extension 835 or around 15%.

So I think I'll just do it. As I said it's been bugging me.

 

[Roadworthy]

The shortened shaft should be fine. Just remember to cut the same amount from each half.

 

[aesmith]

The shortened shaft should be fine. Just remember to cut the same amount from each half.

That's always advised, but the two new shafts that I shortened both started off with the inner already shorter than the outer.

So my process is to cut the measured amount off the outer. Then test fit the inner and measure how much needs to come off. From memory it was something like 10 or 15mm less.

 

[nyone]

Your machine is 25hp and it's a mower and more than likely has swinging blades. 6" overlap should be more than enough.

Most 25hp lawnmowers are running the same HP though a belt that lasts hundreds of hours without swinging blades.

 

[airbiscuit]

 

[Williy]

willy

 

[aesmith]

That's always advised, but the two new shafts that I shortened both started off with the inner already shorter than the outer.

Just to illustrate that point here's the shaft after cutting 40mm off the outer and before cutting the inner. You can see only 15mm or so needs to come off.

These are the actual offcuts. Without doubting your comments that I'll have miles more overlap than needed, I don’t see why I'd want to sacrifice an inch by cutting the same length off the inner.

 

[AndrewInOz]

agree , no point shortening either tube beyond that required achieving desired collapsed length.

However, I make a point of leaving the safety shield exact or 5mm too long so the plastic bottoms out before either end metal does.

This gives the operator a visual on what internal clearance is left during unusual maneuvers like reversing a mower into an upward inclined bank. Or after grabbing the wrong shaft...