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BMinor8806

Allis-Chalmers 914H PTO Hot

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BMinor8806

I've rebuilt and relined my PTO clutch on my 914H with a piece of leather. I glued it in with contact cement and all works well. Lately it's been getting so hot you cannot touch it after mowing. I replace the bronze bushing, the bearing was turning smooth. However the spring on this PTO does not turn when the tractor is running and it does turn on my 916H. Is there something I did wrong? The PTO fully engages and disengages properly. I'm stumped!

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BMinor8806

I checked the lining. It's all there. It engages smoothly and securely. I thought the same thing myself. Does the spring have to rotate being sandwiched between the locking ring and bearing surface? Maybe there's drag there. Also my bushing is starting to show wear already, I just replaced it a month ago.

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John_in_Oxford

Did the same "leather rebuild" as you, thanks to the info found on this forum.

The spring definitely DOES rotate.(edited)

The inner race of the ball bearing (with the bronze bushing installed), the front spring seat, spring, and rear spring seat - all act as one sub-assembly. (edited)

It's possible to still have lining material, yet the nose of the inner cone could still bottom out against the face of the outer cone.

I know, my first "leather rebuild" ended up in exactly this condition.

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BMinor8806

What bearing does the brake pads on the Pivot Assembly have to do with heat? My PTO Pivot has barely any if at all on it. Is it possible to replace those with leather as well?

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John_in_Oxford
quote:Originally posted by BMinor8806

What bearing does the brake pads on the Pivot Assembly have to do with heat? My PTO Pivot has barely any if at all on it. Is it possible to replace those with leather as well?


id="quote">
id="quote">When the clutch is engaged to drive the deck, the brake pads make no contact. When you pull the lever to disengage, that is when they come into play, and should immediately stop and hold the inner cone from turning. Literally, they are what do the disengaging.As far as using leather there - sure, why not?The pad material on my 3416H is nearing paper thin, but I just don't consider it an issue for the time being.The engineering behind this clutch is really clever - but it all hinges on maintaining proper bushing and bearing clearances. As soon as there is measurable wear in either, the 2 cones no longer center as well (because of the downward pull of the belt). That in turn, focuses the friction loading on only a part of the circumference of the cone, leading to accelerated wear on the friction band....which leads to more heat, more wear on the bushing - kind of a vicious cycle here - see where it all is heading?Additionally, that spring tension is critical too. I'm very sure the force exerted by that 40 year old spring in my tractor is less than when new.Just for reference: "The Book" calls for 1/8" rearward movement AT THE TWO CONES from fully engaged to fully disengaged. And when engaged, you need to be able to grasp that pivot assembly that pulls the inner cone back, and rattle it easily - to confirm it isn't preventing full engagement.This is why I'm seriously researching what it is going to take to put an electric clutch on mine.

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John_in_Oxford

A couple other things found out while decoding these clutches:

1. The ball bearing: Even a 40 year old ball bearing can still spin smoothly. BUT - there should be no, and I mean ZERO rocking action when you try to rock the outer race. Any at all is too much for that part number, and it is time for a new bearing.

2. Shaft wear: As a consequence of the bronze bushing wearing out, eventually, steel is going to contact steel. Once that happens, a bunch of small grooves are going to form, and that shaft diameter is gong to take a hit - depending on how long it was run. The obvious solution is to polish the shaft with 600 grit.

BUT: When the clutch is disengaged, that inner cone assembly is now riding fully on the bronze bushing, with the full downward force of the drive belt. So now you have those extra grooves - along with the keyway, working away at the bushing.

That doesn't happen when the clutch is engaged - everything turns together - inner cone, outer cone, and shaft.

Those of us who spend most of our time with the mower engaged - probably get good life from a repair. Those of us who spend more time with the mower off - hauling a cart or other non-mowing work - shorter repair life.

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HubbardRA

The spring fits against a washer that sits against a spring clip on the shaft. The spring should turn all the time. Either the spring clip is missing or popped out of groove on shaft, or it has worn through the washer. I had one do that and it messed up all the parts. I had to replace spring, washers, bearing assembly, and cone clutch. Mine also broke the spring.

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BMinor8806

That's what I thought. I have a 916H with good spring clips and the spring turns all the time and the PTO never gives me any issues. Also I don't agree with those of us that use the PTO all the time and have it engaged more makes it last longer. The 916H is over 30 years old ('79) and we only replaced PTO parts once. I'll have a look at the spring clips this weekend.

Thanks guys!

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John_in_Oxford

Hubbard knows. Got me so wound up, I just completely disassembled the one on my 3416H.

Round wire circlip in place both at rear spring retainer (next to frame)? - check

Round wire circlip in place in front of inner cone? - check

Assemble and observe clearances - check

Put it all back together and observe motion - WHOA!

There's just enough endplay in PTO shaft to push the back retainer against frame, holding the spring & everything else stationary.

Well, it's gonna continue to run like that until I fit an electric clutch. It's been running all season so far with no wear - so I'm good with that.

Hubbard is right - I'm gonna go back and edit the crap info out of my earlier post.

And yeah, if you don't use the clutch - it has to last longer.

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HubbardRA

Another thing that I have been doing is that when there is no attachment hooked to the PTO, I will engage the clutch so that everything rotates with the shaft and it does not even spin the bearing on the shaft.

After losing three of these units for various reasons, I am quite particular about how I set them up now.

The thin, stainless steel sleeve in the center of the bearing usually goes out on mine. I have replaced two of the bearings so far, since the sleeve can't be purchased separately.

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John_in_Oxford
Originally posted by HubbardRA

Another thing that I have been doing is that when there is no attachment hooked to the PTO, I will engage the clutch so that everything rotates with the shaft and it does not even spin the bearing on the shaft.

id="quote">Yup. I bought the Fafnir bearing (1100KRR) and machined my own bushing.

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John_in_Oxford

Soomething else I just finished doing: I machined off a clean face on the rear spring seat, and a recess on it and the bushed end for each circlip.

I found that especially the rear spring seat could push the circlip up and out of its groove back towards the recess where the pto shaft comes out of the frame.

I also changed down to a 0.165 wire size circlip from the original 0.175 circlip - in order to make sure the wire had at least 1/2 its diameter into the groove of the PTO shaft.

This is the spring seat with recess machined it:

http://i41.tinypic.com/npi8f6.jpg

This is the cone clutch end with recess and circlip in place.

http://i41.tinypic.com/44bbq.jpg

Because the wire is 0.010 smaller, it is impossible to rock it out of the groove in the PTO shaft.

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Brettw

I also believe, that is your read the service suggestions on the cone clutch assemblies, it recommends replacing the spring clip (circle clip, round wire clip) whenever you service the clutch assembly.

I might add, engaging/disengaging the clutch at a relatively low RPM will help with less wear and longer life. And if you have a vac unit, it is nice to have the PTO lever on the unit itself. I always idle down, disengage the vac unit, then the cone clutch. No sense using the cone clutch brake trying to stop a rotating piece of cast iron if I don't have to.

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BMinor8806

I'm going to take mine apart this weekend or next week to check the circle locking rings. My guess is my rear one went out locking the spring retainer to the frame. I'll probably need a new brass bushing as well. I'll let you know how it all goes.

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HubbardRA

Don't know what the "brass bushing" is. None of mine have had a bushing of that type. It sounds like John made a brass bushing to replace the stainless steel sleeve for his replacement bearing. Factory bearings do not have a brass bushing in them.

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John_in_Oxford
quote:Originally posted by HubbardRA

Don't know what the "brass bushing" is. None of mine have had a bushing of that type. It sounds like John made a brass bushing to replace the stainless steel sleeve for his replacement bearing. Factory bearings do not have a brass bushing in them.


id="quote">
id="quote">I used brass because that is what the remnants were when I disassembled mine.Thatfact , plus what I observed when operated, is what led me to believe the design meant for the inner bearing to remain stationary, and the brass bushing was the wear element.I'm sure the remaining bit is still floating around the lathe someplace, I'll snap a pic of it.I know the history of this machine, having talked to the original owner - who has left it parked for the last 20 years.BTW: I went to Joe's Outdoor Power today (just came back) and picked up a really primo BGB.This one I'll go through in the coming week, and see if I can make some improvements also before stuffing it in the machine.Pic of paper-thin old bushing:http://i44.tinypic.com/dm5v8x.jpgThread from this forum where the bronze bushing and bearing numbers was discussed a long, long time ago:http://simpletractors.com/Club2/topic.asp?ARCHIVE=true&TOPIC_ID=23918If I had known stainless (or similar) was used, I would have then gone that way, and would have re-thought how the clutch functions.Having a piece of bronze bushing that thin, pass thru both the ball bearing and spring seat - then not expect a fracture failure in a short time (where the spring seat abuts the bearing race) is a bit much.Just my 2 cents worth.

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BMinor8806

What is a good way to remove any shaft end play from the driven shaft of the BGB? I tore into my PTO today and it seems my shaft moves a little to make the retaining ring go behind the frame and prevent the spring from rotating. All other parts look good so I got luck there. I just need to tighten this up and put everything back together and I should be good to go. Do I need to remove the right hand side plate and install / inspect the shims? I'd hate to have to do this now but I might as well since it's half way tore down.

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HubbardRA

Sorry but I can't give you any info on the inner workings of the BGB. I have never worked on the insides of one. I have been able to purchase used BGBs in good shape for much less than the cost of parts to rebuild a BGB. The last one that I had to go bad ruined the shafts and the housing, so there was really nothing to rebuild.

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BMinor8806

Well, I took the rear plate off of the BGB tonight and I found that the snap ring unseated from its groove on the shaft. It had a ridiculous amount of shaft play and reseating it and torqueing the Transmission pulley solved the alignment issue. Now I just need to reassemble the PTO side and it will be good to go. Anyone know how think the brake pads on the pivot assembly need to be? I need to glue some leather to that before I can fully button her up.

Thanks for all of the input!

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Brettw
Well, I took the rear plate off of the BGB tonight and I found that the snap ring unseated from its groove on the shaft.
id="quote">

I think that's why they say replace the spring clip. I think it's only a few bux at the dealer.

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