PTO DRIVE SHAFT OVERLAP

[Tomas]

I have installed a Pat's Easy Change on my cat. 2 3 pt. hitch. This has made some of my pto drive shafts have 1 1/2 -2'' overlap on the male and female sharts. I have 67 hp at the pto and am most worried about my 7' tiller. It is equiped with a slip clutch, but I also have lots of rocks.
How much overlap do you need? What is the downside of running it with 1 1/2'' overlap?
Thanks. Tom

 

[k0ua]

I have installed a Pat's Easy Change on my cat. 2 3 pt. hitch. This has made some of my pto drive shafts have 1 1/2 -2'' overlap on the male and female sharts. I have 67 hp at the pto and am most worried about my 7' tiller. It is equiped with a slip clutch, but I also have lots of rocks.
How much overlap do you need? What is the downside of running it with 1 1/2'' overlap?
Thanks. Tom

OMG stop now. Do no run this PTO with 1.5 inches only of overlap. You are supposed to have at the minimum overlap 1/3 of the total shaft length. Here is what happens. the outer shaft splits and the powered end flails around at 540 rpm in a big arc beating the he77 out of anything it can touch.. I have run one with 5 or 6 inches of overlap, and it worried me so that I bought another much longer shaft. You need to fix this now.

James K0UA

 

[Tomas]

Hi James.
You have made a believer out of me. I will replace the shaft.
Thanks for your insight.

Tom

 

[k0ua]

Hi James.
You have made a believer out of me. I will replace the shaft.
Thanks for your insight.

Tom

Good deal:thumbsup: We have had a few come on here with a shaft failure.. it is fairly rare but can happen, I just would not want a big metal baseball bat sized thing beating the heck out of the backside of my tractor if the outer shaft should split under load and come apart.. Ouch! goodness knows what could fly off!

James K0UA

 

[gwdixon]

Or...you could get a PTO shaft extender to make up the 4" difference like other Pat's owners have done.

Pto Adapter 1-3/8 X6 Spline Male X 1-3/8X6 Spline Female Pto Adapter

 

[thavil]

For only $20 bucks, I would suggest that you buy the PTO adapter that gwdixon mentioned versus buying new PTO shafts. I ordered the same adapter from Agrisupply last week and received it within 4 days. I hooked up my rotary cutter this morning and what a difference in shaft overlap. Much safer!!

 

[Tomas]

I have one of these on the way and will see if it gives me the 6-7" overlap I would feel comfortable with.
Thanks to all.


Tom

 

[bake321]

I recently bought a KK 84 inch tiller and the shaft that came with it only over laps 3 1/2 inches. The safety cover crumpled during use due to being to short. I would think that the OP would have the same problem. The shaft for this big of a tiller was only 19 inches ujoint to ujoint when closed. Waiting for some action from the dealer or KK.

Cary

 

[DieselBound]

Digging this out of the grave...

OMG stop now. Do no run this PTO with 1.5 inches only of overlap. You are supposed to have at the minimum overlap 1/3 of the total shaft length. Here is what happens. the outer shaft splits and the powered end flails around at 540 rpm in a big arc beating the he77 out of anything it can touch.. I have run one with 5 or 6 inches of overlap, and it worried me so that I bought another much longer shaft. You need to fix this now.

James K0UA

James, where did you get that metric of 1/3? I've been looking all over the place and I cannot find any sort of standard listed anywhere. I've seen it mentioned that the overlap needs to be as much as 2/3* the collapsed length. And then I see in some manufacturer's manuals that a piddly 6" is sufficient: Bush Hog lists minimum as 6" for my 286 cutter. Messicks also mentions 6".

* This was from/on a site that sells wood chippers and such, so perhaps this is more application specific.

Also, can a larger series shaft get by with less than the minimum set for a lesser series shaft if used on the same tractor and implement?

This all became a curiosity for me when encountering this problem.

 

[k0ua]

Digging this out of the grave...



James, where did you get that metric of 1/3? I've been looking all over the place and I cannot find any sort of standard listed anywhere. I've seen it mentioned that the overlap needs to be as much as 2/3* the collapsed length. And then I see in some manufacturer's manuals that a piddly 6" is sufficient: Bush Hog lists minimum as 6" for my 286 cutter. Messicks also mentions 6".

* This was from/on a site that sells wood chippers and such, so perhaps this is more application specific.

Also, can a larger series shaft get by with less than the minimum set for a lesser series shaft if used on the same tractor and implement?

This all became a curiosity for me when encountering this problem.

I saw it on some PTO manufacture site. I can't remember where. I will look. But I have also seen manufactures of mowers etc, list 6 inches as minimum overlap. Obviously on a short shaft as on some implements the overlap would be less than you would expect for a larger rotary cutter with a long shaft. It would make sense to me instead of specifying an exact overlap length, that an overlap ratio to the overall length would make a lot more sense. Example say your shaft was 6 foot long, Would 6 inches seem enough? I don't think so. But on an 18 inch shaft? Yeah you bet no problem there. Also it makes sense to me that the more torque that needs to be transferred the more overlap there should be to help prevent stress cracks from forming and the shaft splitting.