Overstressing PTO U-joints?

[Wagtail]

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.

View attachment 511017

Ta for that visual aid Xfaxman.

I read that the maximum working angle was 35 degrees.

 

[KYErik]

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).

Yes- you will need a bottle jack and a strong chain. Place the bottle jack on top of the outward bend and run the chain from one end of the shaft to the other and over the top of the bottle jack.

 

[Xfaxman]

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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).

The shaft can be bent buy lifting the bush hog with a top link that is set too long. The shaft will contact the front of the bush hog and bend. If the PTO is turned off, the operator won't know it happened.

 

[DieselBound]

Regarding Bush Hog making cutters for 50 years, they might have been making them for only 30 years when this unit was made Lots of manufacturers have been making the same product for decades and yet they will still produce some poor designs. While this is possible it's probably, in this case, not probable.

Rick, I have the manuals, thank you: that's where I got the HP specs; I had tracked the service manual so that I could get the specs for setting the slip clutch (before I first used the cutter). The ratings that folks here are stating for the shaft are all over the place/spectrum. "35 hp." And "There's nothing special or unique about connecting a 286 to an NX 5510" ( it "connects," yes, but the issue is whether it can operate at full range/power- so far it's proven not capable, though the question is whether it had a pre-existing condition that I wasn't aware of).

I've never had a PTO issue up until now. And now all of sudden I've got a mess. I always look to blame myself first but in this case I'm almost convinced that the previous owner (who ran a business clearing land) likely screwed this thing up.

Just want to make sure that if I shell out for a new, complete, PTO shaft that I won't be posting back here that it failed again.

 

[countrybumpkin]

You said the shaft had been replaced before you bought it, just curios if it was replaced with a smaller cheaper shaft, that has gotten bent and can't handle that size cutter?

 

[aczlan]

You said the shaft had been replaced before you bought it, just curios if it was replaced with a smaller cheaper shaft, that has gotten bent and can't handle that size cutter?

That is what I would look at first. If there isn't a part number, here is a page to help you figure out what model it is and from that you can check that it is rated for the HP that your tractor puts out: Royal Brass and Hose Blog

Aaron Z

 

[RickB]

Whatever. That machine is probably 10 to 15 years old at the most. That would be about half as long as I've been using, professionally repairing, and selling parts for Bush Hogs.
Good Luck to you.

 

[DieselBound]

Xfaxman, thanks for that input, that's kind of what I was after. How would one check for this? I don't have a quick hitch, and if anything I was tending to operate the cutter more with the tail end raised than drooping. I suppose that operating at near the minimum overlap (approximately 6 1/2") that with a replacement shaft I should be looking to have a greater overlap (ensuring, of course, that it's not fully collapsed when the top link is at its shortest).

country, I just don't know what the previous owner did. I'll try to do some more forensics on this thing: I've been busy with a bunch of other things and haven't had time to really scrutinize.

Aaron, that's an excellent link, thank you!

At this point I know that it's an Italian/Metric, class four shaft.

The more I think about this the more I'm almost positive that the shaft was bent when I bought this thing. The reason I suspect this is because the U-joint (tractor side) had one (or two) of the cups showing cracks (might even has been a small chunk missing) on the cup edges. Seems that a bent shaft would put a lot of stress on the U-joints.

 

[Xfaxman]

Xfaxman, thanks for that input, that's kind of what I was after. How would one check for this? I don't have a quick hitch, and if anything I was tending to operate the cutter more with the tail end raised than drooping. I suppose that operating at near the minimum overlap (approximately 6 1/2") that with a replacement shaft I should be looking to have a greater overlap (ensuring, of course, that it's not fully collapsed when the top link is at its shortest).

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The more I think about this the more I'm almost positive that the shaft was bent when I bought this thing. The reason I suspect this is because the U-joint (tractor side) had one (or two) of the cups showing cracks (might even has been a small chunk missing) on the cup edges. Seems that a bent shaft would put a lot of stress on the U-joints.

Adjust the toplink out as long as it will go. Don't turn on the PTO, slowly raise the 3 point watching the distance between the PTO shaft and the front edge of the mower deck.

The previous owner may have had a hydraulic toplink and forgot to retract it some after backing onto a down slope.

 

[DieselBound]

OK, will check!

Hydraulic top link kind of makes me nervous now. I actually struggled to get the rear of the mower adjusted correctly (keep in mind that I'd only operated it about three times) and just dropped the tail wheel bracket down in an effort to get the tail end up a bit more. So, if anything, I've been tending to get the tail UP more so than down.

The previous owner worked the snot out of this thing. Pretty sure that the additional 1/4" plate steel on the deck is because the deck had been ripped up: looking on the underside one can see this. Breaking U-joints and such... my money is on this thing having been very ABUSED: if I can get this PTO issue resolved I figure that I'd still be coming out ahead (vs buying a new one).

 

[DieselBound]

Took some pictures of the carnage.

Here's one showing the bend on the "shaft" piece. Also shows the "tube" piece, and from that you should see how well worn it is (metal is really gouged up; and, the range of travel seems pretty well established, predating my use); there seems to be a slight distortion in this piece, though it's very slight (almost looks like it twisted a bit). The pieces don't slide together fully, which shouldn't be any surprise. I failed to fully inspect the PTO shaft before and after purchase.


Here's one showing the slip clutch and the U-joint there. Kind of hard to see, but one of the end caps is cracked/broken. And the U-joint itself is loose/failing.


Note the pin walking out in that second picture (tube yoke). I'm wanting to say that it's happening on the shaft yoke as well. That rust isn't new!

The shaft yoke is beat up from the event I encountered. I suspect it's not reusable. And given that the guard is also beat up it's looking like I'll be needing everything except the slip clutch (though now I'm not certain what condition that it is in- I thought that I was able to get it to slip; I set it to just shy of spec (a bit looser).

 

[Rock knocker]

Time to buy a new shaft? The Bare Company PTO shafts that Washington Tractor sells are really nice.

 

[Wagtail]

Time to buy a new shaft

No question about it, buy an entire new shaft assembly. If that means a new slip clutch, then so be it. Cut it to your tractor/implement distance and keep that shaft dedicated to that implement only.

 

[DieselBound]

Yeah, pretty much figured this thing was toast. Wanted to know what may have happened so that I don't replicate this situation.

Rock knocker, thanks for the pointer there. I will talk to these folks and see if I wouldn't be best off with a 6 series shaft. They mention that one should reduce the HP rating by 40% for severe duty. I don't think I'm operating at a "severe duty" level, but it's not a bad idea to be a bit beefier. Series 6 is rated 64hp (PTO), and de-rating by 40% gives 40hp; tractor's PTO is rated at 43hp (it's an HST), so I'd be pretty close here. Also, the shaft length seems more appropriate: 65" open and 39" closed- I will remeasure, but I believe that I was about 58" open (maximum, a distance that I wouldn't likely see when in use, but it's the physical maximum based on my top link's extension); minimum number looks good as well; I'd have a normal working overlap of about 14" (vs. 6 1/2" with the series 4).

No pricing info, but would I be correct in figuring that I'd be looking at around $500?

I'm really figuring that the previous owner was undersized on the PTO shaft. As mentioned, I'm guessing his JD was about 45hp, which is about 37hp at the PTO. He ran this thing in what was obviously a "severe duty" application. A series 4 PTO wasn't the right match, especially if he didn't adjust the slip clutch properly (if ever).

 

[Wagtail]

Yeah, pretty much figured this thing was toast. Wanted to know what may have happened so that I don't replicate this situation.

It looks to me (by way of your photo) that the shaft is too short for the application. The previous user simply used a shaft that he had 'at hand' that 'sort of' fit and he wouldn't have to spend money on an extra, new one.

My recommendation is to measure the distance from your PTO to the implement (whilst mounted) and take that measurement to wherever you decide to purchase a new shaft. Do Not take the old shaft, or the measurement of the old shaft, as a guide.

 

[marchanna]

PTO shaft prices are all over the map. Spend a little time searching the web to find a good price. As far as I can tell the Chinese and Indian made ones are just as good as the Made in America ones (if they are indeed made in America).

 

[RickB]

PTO shaft prices are all over the map. Spend a little time searching the web to find a good price. As far as I can tell the Chinese and Indian made ones are just as good as the Made in America ones (if they are indeed made in America).

I'm pretty certain I have a suitable series 6 shaft with clutch at work that would retail for around $400 or perhaps a little less. And while I try to be competitive, I'm sure I'm not the WalMart of PTO shafts.
You are not going to find a metric style PTO shaft made domestically.

 

[DieselBound]

Wagtail, the previous owner had said that he had to buy a new shaft because he couldn't get U-joints for the previous one. Although he seemed like an honest guy it's hard to say what the real story is: clearly, it was disingenuous for him to make this point as it inferred that it was a good shaft, and, clearly, it was not. Yeah, not going to use this one to spec out a new one: I've talked to a local tractor dealer and they told me to bring it in- I told them NO.

Rick, I may take you up on your offer. Shipping, however, is likely going to bump things up in cost; and, once I figure out which way to go on this I'll likely be running more behind, time-wise (I have to what to see what the turnaround time is for ordering locally).

What are people's thoughts about a series 6 here vs a series 4? EricTheOracle is running his Woods BXX7200 off his NX6010HST using a series 4 PTO: he's fairly aggressive with things, so I figure that if a series 4 shaft holds up for him then I'd figure it would for me. It might be the shaft that came with my cutter was so far gone/abused that I'm overly paranoid. Which still brings me to the following question....

There is clearly a lot of folks running series 4 PTO shafts on tractors putting out well in excess of the 35hp that these shafts are rated for- why are the shafts holding up? Is this disparity managed by torque limiters and slip clutches?

I've got a local dealer (Washington Tractor) checking with Bush Hog on whether a series 6 PTO shaft is OK to run a 286. These folks, as Rock knocker noted, carry/resell Bare Co. PTO stuff, and I like the looks of these offerings from Bare.

 

[RickB]

My shaft is sourced form A&I. Perhaps you have a dealer for them nearby.

 

[DieselBound]

Well, Washington Tractor punted on me. I'd asked if they could find out if I was OK to run a series 6 shaft on the Bush Hog 286 and they said they'd check with Bush Hog. The next day (they were prompt!) they left a message telling me to talk to the Kioti dealer (I'd told them I had a Kioti). Lame... SO, after more research (and everyone here's input) I think that I'm a fair bit wiser and should be able to locate what I need w/o the assistance of the "professionals."

I measured 58 1/2" from tip to tip: cutter disconnected, so it's perhaps a little on the long side (cutter sitting down on the ground). I think that in the EA video Ted measures to one of the notches; that adds 1 3/8", so 58 1/2" plus 1 3/8" comes out roughly to 60". Reading on Royal Brass' web site they mention that shaft overlap should be no less than 1/3 the compressed length. If I take my 60" and divide by 1 1/3 I get roughly 45" as my collapsed size.

I'm going to measure the possible extremes (based on full extension and collapsing of my hydraulic top link) just to check that the shaft overlap could be properly maintained.

Realizing that I've bought several implements from EA (and that their video was mentioned in this thread!) I decided to see what they offer in the way of shafts and, lo and behold, I see this:

Class 5 Eurocardan PTO Shaft for 5, 6, and 7 Rotary Cutters

Series 5. 45" collapsed.

Pretty sure that this is a perfect match. And looking at it I can see how TOTALLY wrong the previous shaft was (not only for MY use, but almost certainly for the previous owner's use as well).