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.

 

[k0ua]

Here is one pamphlet on PTO overlap. It mentions 2 inches from bottoming out, and 1/3 of PTO shaft overall length of overlap

http://www.newtoncrouch.com/files/faq/pto_adjustment.pdf

 

[k0ua]

This landpride chipper manual calls for 1/2 overlap.. So the consensus is there is no consensus. 6 inches, 1/3 overlap, 1/2 overlap. Take your pick, but I say the more overlap the better, as longs as the halves don't bottom out.. The longer the shaft, the more overlap you need in inches, but if you use a ratio formula it should work for all lengths. I am sticking with my 1/3 story.

 

[Oldoak]

I say the more overlap the better, as longs as the halves don't bottom out..

Yep, that has always been my thinking. And the way I sized a PTO drive shaft for my tractor the few times I had to cut one down to fit. I also keep the shafts well greased along with the universal joints.

 

[k0ua]

Yep, that has always been my thinking. And the way I sized a PTO drive shaft for my tractor the few times I had to cut one down to fit. I also keep the shafts well greased along with the universal joints.

Yes, greasing the shaft is often overlooked by a lot of people, and that is why you hear these horror stories of the shaft seizing up. It makes sense to me that the fact that the shaft is constantly moving in and out as the implement is going over the terrain, that the shaft could use some lube.

 

[DieselBound]

I think that the variance lies with USE/IMPLEMENT. Different implements seems to have different requirements. Rotary cutters seem to have a lower overlap requirement while chippers seem to require a greater overlap. The Newton site looks like it's focused on spreaders and sprayers: what the PTO demands are here isn't clear to me; but, it's a different kind of application than that seem by rotary cutters. I'd think that rotary cutters, especially any operating in tough brush, would require a greater overlap.

Shaft that I am looking at (well, I went ahead and ordered it) will give me the 1/3 value at working length. This comes out to a 13" overlap (with 60" maximum shaft length). Again, Bush Hog states 6" as minimum. I am also going to go with a series 6 shaft rather than a series 4, which should give me a bit more strength. I suppose, however, that the slip clutch is supposed to intervene if the shock/torque loading gets too high such that it would start to deform the shaft (hammer U-joints) or the tractor's PTO.

Reading in another thread I saw it recommended to use Fluid Film for lubing the shaft. I'd never lubed a PTO shaft before (wasn't aware of this need), but will certainly be doing it now! (why this site is so great- you learn a lot of important stuff here!)

 

[k0ua]

Fluid Film would work, but to save the More costly FF for other uses, I just slather the inner shaft with my regular grease, and put a good amount on the inside of the outer shaft and put them together. Once a year should be suffecient, unless you store outside all the time in the weather, then more often as needed.

 

[Oldoak]

Fluid Film would work, but to save the More costly FF for other uses, I just slather the inner shaft with my regular grease, and put a good amount on the inside of the outer shaft and put them together. Once a year should be suffecient, unless you store outside all the time in the weather, then more often as needed.

:thumbsup:

 

[DieselBound]

To add a data point here...

Bare Company, from whom I'm ordering a PTO shaft from, says that their 39" collapsed and 65" extended shaft has a 15" overlap. So, I would guess that they are good with being less than 2/3 but better than 1/3. I picked this shaft because the 65" allows the possibility of running the cutter off of a quick hitch; and, it also has a convenient mechanism for getting the guard tubes out of the way (allows for easier hook-ups).

 

[Rara Avis]

Depends on the component...but 6 inches is minimum...In the collapsed position the driveline should be approximately 2" from bottoming out to prevent possible damage to the tractor or implement.

BEFCO - Technical - Technical Tips - Adjusting the Drive line to the correct length.