Overstressing PTO U-joints?

[DieselBound]

Pictures worked the other day. Suspect a system glitch: I'll follow up to make sure they show up for posterity sakes. The pictures really don't add any insight into the problem, just shows what the cutter looks like with the top link fully contracted.

This is a slip clutch shaft, so swapping ends ain't going to be possible without disassembling the U-joint on the slip clutch end.

Again, the previous owner appears to have had a problem as well: he had a Deere, probably 45hp-ish. If I am to believe him, and by the newish appearance of this shaft, he had recently replaced this shaft because he couldn't find U-joints for the previous shaft. Because of this I do not believe it's anything to do with my tractor or my use, but something else.

On the individual shafts, is the larger diameter piece supposed to go on the tractor end? That's how this one is set up. pmsmechanic might be on to something regarding the proper alignment of the joints: I'd never think this would be an issue, so perhaps that would be the case with most others as well; NAPA didn't seem to be concerned; I didn't, however, provide both shaft sections.

I'd like to check the rear (mower end) section, but am not sure how to get the plastic shield's cover off. There's these plastic (white) tabs that say "PRESS." I'd attempted to do so (on the other end) but was unsuccessful in getting the plastic housing to separate: I'm guessing that the tube disconnects from the collar- this is what I want so that I can expose the shaft to inspect for straightness. If I can get this off I'll upload a picture of all these bits (no assurances that this site will display it!).

 

[RickB]

Unless the person doing the assembly has a special talent for creative stupidity it is impossible to assemble a tri lobe or lemon shaped PTO shaft and get the joints out of phase.

 

[DieselBound]

Unless the person doing the assembly has a special talent for creative stupidity it is impossible to assemble a tri lobe or lemon shaped PTO shaft and get the joints out of phase.

To help clarify, I believe the issue is with the orientation of how the U-joints are installed (maybe the alignment of the yokes?) and not with the alignment of the shafts (which are keyed).

 

[RickB]

To help clarify, I believe the issue is with the orientation of how the U-joints are installed (maybe the alignment of the yokes?) and not with the alignment of the shafts (which are keyed).

Again, not possible under anything approaching normal repair methods. The yokes only fit the tubes one way, just as the tubes only fit together one way.

Google universal joint phasing and see if yours are phased properly.
You don't have to guess or speculate.

 

[DieselBound]

Again, not possible under anything approaching normal repair methods. The yokes only fit the tubes one way, just as the tubes only fit together one way.

Google universal joint phasing and see if yours are phased properly.
You don't have to guess or speculate.

I only had to look at the shaft to see, so yeah, got i!

Pretty much without a clue here. Previous owner had this issue and now I'm having it.

 

[MHarryE]

I read above yours should be a Bondioli Series 4 which has a 35 HP capacity at 540 rpm. The capacity rating is with u-joints straight and drops quickly with misalignment (I know j-joints are intended to transmit power around corners but they do it with a cost in driveline life).

PTO Driveshaft - BONDIOLI & PAVESI - Page ndeg 13 - PDF Catalogue | Technical Documentation | Brochure

the link is to the 250 page bondioli & pavesi pto driveshaft design manual.

Torque limiters (assuming yours has a slip clutch) can have a large variation when left sitting. Page 142 of the design manual covers friction clutches.

 

[Rock knocker]

Unless the person doing the assembly has a special talent for creative stupidity it is impossible to assemble a tri lobe or lemon shaped PTO shaft and get the joints out of phase.

To help clarify, I believe the issue is with the orientation of how the U-joints are installed (maybe the alignment of the yokes?) and not with the alignment of the shafts (which are keyed).

The shafts normally have a key way so while they may appear the same on all sides they can't go together unless the u joints are phased. And because the yokes are welded to the shafts it is unlikely this could get messed up.

Sorry tp reiterate what has already been stated.

 

[Xfaxman]

Here is a visual aid, because some shafts can be put together out of phase or a repair job may have welded the yokes on wrong.

 

[DieselBound]

Can I point out that it wasn't me that raised the issue of the "out of phase" U-joints? I just kind of jumped on it (before I actually looked) in more or less of a crapshoot hope thing.

According to the manual for this cutter it says that it's a class 4 drive line. Gearbox is rated 110hp. Bush Hog states that the MINIMUM HP is 40. No reference to what the "maximum" would be. And of course, there's no mention of whether this is engine or PTO HP they're talking about.

Harry, yes, it's a Bondioli: there were two different ones spec'd, but the one on this unit is a Bondioli.

In my mind I'd figured that this cutter would work on my NX. Apparently the shaft won't (and I don't want to try patching around this problem with a torque limiter), in which case is it possible to up-scale the shaft? I'd hate to have to get rid of this cutter, but if it ain't going to work it ain't going to work.

How can one bend a shaft? I'm really thinking that the thing was bent when I got it: always had a bit of a vibration to it. And most likely it was the bent shaft that caused the U-joint to fail (not my use).

 

[RickB]

Bush Hog has been making rotary cutters for more than 50 years. You don't have to re-engineer this driveline or up-spec it. You might have to buy some parts or maybe even a new shaft. There's nothing special or unique about connecting a 286 to an NX 5510. Find a Bush Hog dealer or a retailer of farm equipment parts that understands PTO shafts and get yourself fixed up. Do learn how to service the slip clutch and make sure it is done at least annually.

Download your rotary cutter operator's manual and parts manual here:

http://www.bushhog.com/uploads/documents/BHRotaryCutter280-285-286-287OM-09.pdf

http://www.bushhog.com/uploads/documents/BHRotaryCutter280seriesPM-11.pdf

All the parts for your shaft are available generically or from Bush Hog.