Connect PTO shaft using pin or bolt?

[Richard]

I know the title might not make too much sense so here's the situation.

I've got a 10' Rhino mower. The shaft on it connects of course, to the PTO on the tractor.

To get into more detail, the "shaft" itself is actually connected to the ...what to call it... "yoke?". It's this yoke that actually connects to the PTO.

My question is regarding the attachment of the shaft to the yoke, NOT the yoke to the PTO.

The shaft itself is a 'star' pattern as opposed to square, oval... this star pattern fits into a star receptical in the yoke. The star pattern is what absorbs/transfers all the rotational energy from the yoke to the shaft and onward.

There is a pin. I think they call it a roll pin? It's something like 10mm x 70mm although the exact dimensions won't matter here.

My brother in law once said that this pin was broken. (I DID back into a stump pretty hard and jammed things)

However, this pin was SO entrenched that my BIL had to take a torch and burn it out. While he was doing that, I kept asking myself... "if it's so freaking hard to get OUT, why didn't you leave it IN?"

I digress....

Anyways, got new pin and put things together.

Just other day, mowing a flat field (and having been VERY careful about backing into things) all the sudden, it let go.

I'm a bit embarassed to admit, I spent 30 minutes searching all over the field for the missing shaft, only to find that it had jammed inside its other half and was hidden by a plug of dirt.

I've not yet fixed this.

I need to unplug the dirt, pull the shaft out, hammer out the now broken pin and replace it.

It looks like the pin itself has sheared. There are two tips visible on the yoke side and when I look inside the compressed shaft, I see the middle of the pin.

I've got absolutely NO idea how this happened

I called Rhino about the need for replacing with an exact pin and of course, they said I should.... however, he then went on to say that "if the pin is loose, you could use a bolt" Which is the very exact thing I was calling to see if I could do and he said "no"

So, I put it to you guys...

Although I've got a new pin on order, for future reference, can this rolled pin be replaced with a bolt instead? Would you simply put a lock washer on it? Would you drill a hole through tip of bolt and wire lock it?

The only purpose of this pin as I see it is to simply keep the shaft from sliding out of the yolk holder. It doesn't deal with any rotational energy....it's just a placeholder (as I understand)

This darn little $2.00 pin is shutting me down until I can get another one, so I've ordered FOUR!!! this will guarantee it will never happen again of course but I was simply wondering about using a bolt and if so, any certain grade?

 

[Soundguy]

IMHO.. I'd use the roll pin.. it isn't transmitting power.. it's just holding the sahft together.. My JD 15' batwing has a star pattern shaft.. never broke the old pin in it yet.

I suggest you quit using your mower like a battering ram and backing into things so hard that the shaft is colapsing and perhaps ? bottoming out and shearing that pin.

also lube that shaft.. it should move freely.. if not.. the pin takes abuse.. check for twists too.. though the star shafts aren't nearly as prone to twisting as the lemon or square shafts are.

soundguy

 

[Iplayfarmer]

You're breaking the roll pin because it's the weakest part of the shaft for the particular stresses you are putting on it. If you strengthen that part by putting in a bolt you're going to find the next weakest link. That next weakest link may be inside the transmission of your tractor or in the gearbox of the mower.

What would you rather do... be down for a few minutes on a regular basis to replace a roll pin, or be down for a few weeks to replace parts in your tractor's transmission.

I speak from first hand knowledge because I just got through rebuilding a transmission in a Massey Ferguson 1215 that I bought because a previous user had done just this. He kept replacing shear pins with stronger and stronger bolts until the gears inside the tractor broke.

I know that yours is not a shear pin under rotational stress, but the weakest link philosophy still holds true.

 

[Richard]

I suggest you quit using your mower like a battering ram and backing into things so hard that the shaft is colapsing and perhaps ? bottoming out and shearing that pin.

also lube that shaft.. it should move freely.. if not.. the pin takes abuse.. check for twists too.. though the star shafts aren't nearly as prone to twisting as the lemon or square shafts are.

soundguy

Interestingly enough, when I backed into that stump, (year ago) I really hit it.... the entire front of the mower (pull type) reared up a bit before I figured out exactly what was going on.

What I find most fascenating is, I clearly abused it at that point and my BIL had to FIGHT to get the pin out. Since fixing it, I've been very very careful about backing into things (honestly) and this pin has not received 10% of the abuse that prior pin had.... and yet, while in a flat field, it simply gave way.

On to lubing the shaft.... right now it's got dirt jammed in with it so I know it won't move without some effort. Aside from that, would you grease them or use lithium or even something watery like PB blaster? (I think it's called)

I never considered that simply use and the friction of the tubes sliding back and forth, would/could cause strain on this pin. Thanks for opening my eyes to that one.

 

[Richard]

What would you rather do... be down for a few minutes on a regular basis to replace a roll pin, or be down for a few weeks to replace parts in your tractor's transmission.

Point taken!! You're absolutely right.

 

[Ford850]

I don't understand why the pin holding the yoke is taking any stress. Do you have your PTO shaft cut to the proper length? Maybe it is too long and it is collapsing enough to slam into the yoke?

 

[Soundguy]

Once it got jammed up hard to deform it.. i bet the pin hole is egg shaped slightly now.

now that there is wear.. the forces the push and pull on that pin will add up as there is extra movement.

Depending on how bad it is.. this is the thing that I'd weld up and redrill.. or relocate the hole 90' away if possible.

Pull that shaft apart and clean with your choice.. the sand caked on it will cause it to drag and wear both the pin, pin hole and the shaft itself.

once clean, lube it with your choice of grease, and then put the shield back on it to kep it somewhat clean.

soundguy

Interestingly enough, when I backed into that stump, (year ago) I really hit it.... the entire front of the mower (pull type) reared up a bit before I figured out exactly what was going on.

What I find most fascenating is, I clearly abused it at that point and my BIL had to FIGHT to get the pin out. Since fixing it, I've been very very careful about backing into things (honestly) and this pin has not received 10% of the abuse that prior pin had.... and yet, while in a flat field, it simply gave way.

On to lubing the shaft.... right now it's got dirt jammed in with it so I know it won't move without some effort. Aside from that, would you grease them or use lithium or even something watery like PB blaster? (I think it's called)

I never considered that simply use and the friction of the tubes sliding back and forth, would/could cause strain on this pin. Thanks for opening my eyes to that one.

 

[Soundguy]

I don't understand why the pin holding the yoke is taking any stress. Do you have your PTO shaft cut to the proper length? Maybe it is too long and it is collapsing enough to slam into the yoke?

that's also my guess.. a pto shaft too long that is putting extra stresses on the roll pin..

soundguy

 

[intel]

I agree with soundguy and ford850.
Do you have your PTO shaft cut to the proper length? Maybe it is too long and it is collapsing enough to slam into the yoke?

 

[Richard]

Regarding shaft lubrication & stiction: This mower was bought used and had some issues. One of the issues was the prior owner, although selling this as "field ready" evidntly slammed the blades into something VERY hard as upon our purchase of this, we had to replace the mangled blades, the yoke that attaches to the PTO itself (which was like $500?) and the actual shaft that we're discussing here. So, it was a NEW shaft assembly that (last year) I backed up with and mangled the pin.

My BIL then took the shaft and as I understand it, cut some off. Did he cut enough? Did he cut off both ends? I do not know. I only know that he said he shortened the shaft.

Regarding pressure on roll pin: After last year when the pin broke, I reinstalled a new pin and it was a TIGHT fit. Maybe from a microscopic sense, the hole might have been enlongated...I don't know. I do know that I had to put some effort into it to finally get the pin in.

What is mystifying to me is having learned my lesson on backing up (supposedly), I've really been a good boy about that and this mower has NOT had the back-slam that it had last year when I found that hidden stump.

One reason I hit the stump so hard last year is the transmission on this tractor is kind of herky/jerky.... you can (sometimes) have your foot totally OFF the clutch and it won't move... then all the sudden WHAMMO, it hooks up and lurches. It's very tricky to "finesse" the tractor and now frankly, I don't really even try. Much too stressing to try to gently back up to something, only to then have it lurch.

I found out last night that my Father in law wants to try to sell the tractor at auction this weekend so I took the mower off.

I'll try to get a picture of the roll pin. I looked inside the yoke and ....how to describe this...

The yoke is let's say, a 2" hole. The outer part that the shaft inserts into is let's say, 1/4" thick. On the glance I took last night with a flashlight in hand, it looked more like the roll pin was cleanly cut inside the yoke. It should be VERY easy to punch out the little 1/4" pieces that are stuck in the holes of the yoke. I really expected to see more...how to say... strech marks? Meaning, where the shaft might have been pushed or pulled and bent the roll pin as it broke.

I've got my digital in my coat pocket here at work. When I get home I'll try to post a pic of it if I can (before we go out for a family dinner)

All I wanted to mention in this short book was, this was a NEW shaft so it didn't have any old rust or accumulations that a 10 year old shaft might have accumulated in it.

FIL spent maybe $1,500 to get this "field ready" mower, working. Oh...something else.... right AFTER we got it, one of the jack shafts twisted out on us.

We had to replace the blades, replace the bolts that hold one of the two gear boxes (the same gearbox that hold the bent blade) and the main input pto shaft. We did NOT replace at first, the slightly twisted jack shaft (that again, went to the broken gearbox with the bent blade)

I was cutting one day and the jackshaft gave way. It was already bent when we got it so it was weakened. It simply twisted out like an aluminum coke can. I replaced the shaft and the rubber dampers on BOTH sides of the main gearbox.

field ready indeed lol.

 

[Soundguy]

What tractor is this that has a sticky? bearing so that you are getting inconsistant clutching??? It's very dangerous...

As for the new shaft... might as well check collapsed length.. if all was cut off one side.. you didn't 'gain' very much.

soundguy

 

[Richard]

The tractor is an International 886. I think it's kind of a cross breed of gear and hydro. Meaning, it's got some gear sliders on the left side fender. I think (as in now know) it's got some transmission issues.... I used to have a Honda Accord, manual shift... if you were in 4th gear or maybe sometimes, 3rd... it would/could sometimes simply pop out of gear. Almost like it wasn't FULLY going into the gear. if you held your hand on the shifter, it wouldn't pop out.

This is kind of similar however, it's issue seems to be more going INTO the gear instead of popping out. If you need to change gears, you can often find yourself fiddling around with the gear selector clearly in "1,2,3,4" and STILL have to fiddle with it to actually get into gear.

Add to that I discovered it had a small hydraulic leak. When the tractor is on a slope and you go to reverse, or into forward from reverse, it doesn't always "go" Filled up with hydraulic fluid and that problem basically went away HOWEVER, there is still an apparent issue with rpm's. If you are at a low/idle rpm, put it into 1'st or maybe reverse.... it will just sit there (not always) and then suddenly, decide it realizes its in gear and go.

If the rpm's are up higher, this isn't such a problem....HOWEVER, when you are backing into something, before figuring out all these intracies, you might slow the engine down so it's moving slower, like when trying to slowly backup to attach something to the drawbar.....

My brother in law thinks this 886 has the better engine but that the 986 (which he has at his place) has the better transmission.

Regardless... I once made the comment that if they are going to try to buy something to cut the farm with, as cheap as possible, then you've GOT to expect some issues with said machine. If they bought something 5 years old, verses maybe 25/30, they might simply get a net 'better' machine (and I realize maybe not, if it was abuse....like for example....smashing into hidden stumps when going in reverse )

I've attached some pictures of the yoke assembly. The second picture looks to me like the rolled pin is hanging out a bit and is SUPPOSED to be like that (as though this was the outside of assembly and this is simply the extra length of pin)

I'm intrigued on how clean the cut seems to be on them. On the first picture, you can see the compressed shaft, hidden inside the outer shaft and the rest of the rolled pin in the middle.

 

[Soundguy]

That shaft has seen some better days.

Also.. I assume that machine has a torque amplifier?

soundguy

 

[Richard]

That shaft has seen some better days.

Also.. I assume that machine has a torque amplifier?

soundguy

Shaft: Probably 1 year old give/take

Torque amplifier: You're catching my ignorance... is perhaps that the feature where there is a lever on the dash and upon pulling this lever, the machine will stay in the same gear, same rpm's yet will still 'slow down' just a bit and as I understand it, allow more power to the wheels?

If so, then this machine, the 886 doesn't have it Our 986 does (BIL's)

If that's not a good description, then I don't know the answer.

 

[Richard]

Slight correction... I'm not sure that my BIL bought BOTH halves when he 'replaced the shaft'. It's possible he only replaced one half and if that's the case, I'm under the belief that he replaced the half that is the inside half (that connects to the pto yoke) and not the outer half.

 

[Soundguy]

That star shaft looks worse / more worn tht the one on my 1998 batwing mower .. and it's seen alot of mowing hours...

soundguy

 

[Richard]

That star shaft looks worse / more worn tht the one on my 1998 batwing mower .. and it's seen alot of mowing hours...

soundguy

That may be true, but that doesn't change the reality that at least half of this assembly, defined as yoke that attaches to PTO and shaft, is new (and quite possibly, both halves of shaft)


You wondered earlier about what kind of tractor had issues with the shifting and lurching...

Here's a picture of the gear knob. You can see the left knob (shorter one) has a slider and little notches where each gear is. This is the funky one that even though you are at a notch, it might or might not be in gear....you still have to fiddle around sometimes. More often than not, when you are in first gear (worst) but most of them are a bit problematic.

Once you are IN a gear, the tractor has no issues about jumping out of gear or anything....but for....being at low rpm's (idle) and you want to creep slowlyyyyyyyy..... you can sometimes take your foot off the clutch and nothing will grab for a moment....then all the sudden it's 100% grab.

Seems if the rpm's are a bit higher, this isn't as large of an issue.

I dont' know what kind of transmission you'd call this as it seems to be more of a hybrid gear/hydraulic. It doesn't act the same as the more traditional International 444 we've got (geared).

 

[Soundguy]

I think I'd be checking my hyd filters and the hyds for that control circuit.. if that is a hyd-clutch pack type of 'power shifter' tranny.. etc... wear mechanical linkage may even be the culpret.

I think you 100% completely misse dmy point about the wear and the grunge on the pto shaft halves and what it has to do with the roll pin shearing. I believe if you go back and re-read my previous messages you will see what i was saying.

As others have said.. it's surely not a rotational force shearing the pin.. that only leaves 2 directions.. and those have to do with the pto shaft!

soundguy

 

[gemini5362]

I could not tell from looking at it. You said you are getting a new pin from the dealer make sure they get the right pin for the machine. Not something that will fit. A lot of people make the mistake of calling a split pin a roll pin. They are not the same thing. If you are replacing a roll pin with a split pin you might see the split pin break more easily. For definition a split pin is a pin with a certain diameter that is hollow and has a cut down the length of it. A roll pin looks like you took thin spring steel and rolled it up until you got the diameter you wanted and then cut the rest off. The difference in shear strength between the two should be pretty obvious.

 

[Richard]

A lot of people make the mistake of calling a split pin a roll pin. They are not the same thing. If you are replacing a roll pin with a split pin you might see the split pin break more easily. For definition a split pin is a pin with a certain diameter that is hollow and has a cut down the length of it. A roll pin looks like you took thin spring steel and rolled it up until you got the diameter you wanted and then cut the rest off. The difference in shear strength between the two should be pretty obvious.

I think you get my favorite comment of the day award! I think you hit one nail right on the head...meaning.... given the two descriptions you gave, I know in fact, I installed a split pin.

Interestingly, when I first inquired about this, a rolled pin (I think I was told they were called rollED) was sort of like a wound up spring in that it had layers of rolls.

That is NOT what was received by me (from Rhino).

Upon installing the split ring, I noticed it wasn't 'rolled' but....since it was from them directly, I didn't give it any more thought.

I'm onto the phone now to call them about this difference.

Thanks for turning that light bulb on for me