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Discussion Starter #1
I parted the inner PTO shaft on my Farm King RFM two days ago. It is triangular and the break appeared clean, exposing white metal with no obvious stress riser or corrosion observed.

My BIL suggested attempting a weld repair; I am polling the forum to collect advice/experience with weld repairs of this nature before proceeding.

The yokes on either end of the shaft have a round plastic knob that rotates to allow connection to the Cat-1 splines on tractor and mower ends.

I can envision a weld repair as a risky procedure that may or may not work, may last a minute or a lifetime. The metal appears to me to be mild steel.

Any thoughts or experiences that I should be aware of as I move forward???

Many thanks,

Brian
 

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Personally, I would not attempt a weld repair to a PTO shaft. Reading your post about the break, it seems to me that it was too short to begin with. The shape of the triangular PTO shafts spread the moment load (twisting) about many faces. This is a very strong design for a twisting moment. The fact that it broke leads me to believe that the moment load was too high (RPM's too high when engaged), the contact area between the two halves was too small (most likely), or the PTO shaft was previously damaged and created a weak spot.

So if it was already too short, then it will just break again. If it was previously damaged, it will break again but somewhere else. If your RPM's were too high, then you shouldn't do that again (but I still wouldn't weld it).

Just my $.02
 

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I destroyed my RFM pto shaft a month ago,, the outer part split like a watermelon,,,

I found a drop-in replacement on eBay for $89 delivered.

Now, I have a perfect pto shaft,,,
 

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Discussion Starter #4
Personally, I would not attempt a weld repair to a PTO shaft. Reading your post about the break, it seems to me that it was too short to begin with. The shape of the triangular PTO shafts spread the moment load (twisting) about many faces. This is a very strong design for a twisting moment. The fact that it broke leads me to believe that the moment load was too high (RPM's too high when engaged), the contact area between the two halves was too small (most likely), or the PTO shaft was previously damaged and created a weak spot.

So if it was already too short, then it will just break again. If it was previously damaged, it will break again but somewhere else. If your RPM's were too high, then you shouldn't do that again (but I still wouldn't weld it).

Just my $.02
Ton^2
Thanks for your response. Your thought about torsional loading the shaft make a lot of sense to me, as does your advice about engaging the PTO at a lower RPM. After stops at Rural King and Tractor Supply today that yielded no spare parts joy, I found the replacement parts at Barnes Implement and have ordered a new inner shaft. Much to my great surprise and relief, the inner shaft tube is held in place with a steel roll pin; I won't have to have the tube welded to the cast iron yoke, as was my original fear.

The new inner shaft is slightly longer than the two old broken halves held together- this will place the end closer to the yoke on the mower end.

I should be back in the mowing game by this time next week, now I'll drink an adult beverage or several to celebrate.

Brian:bigbeer:
 

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I just did a shaft repair

I have a Sundown, made by King Kutter rototiller, inner shaft bent like a banana....Ordered new shaft "series 14" cut old one out and replaced w/ new....having said that I now have a 4" length of inner shaft for sale + shipping.... It is the triangular shaped shaft. So they can in fact be replaced, instead of buying new PTO linkage.
 

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I have cut about six inches off both pieces and later on added them on and actually got them straight enough. If it broke I would try and get a set of triangular pieces. They seem to fit into a socket at the yolk and have a round pin to secure them. I have never had need to try this but it would be less expensive than getting the same shaft. You did not provide information on how it broke. There are drive shafts with a slip clutch built in, differing diameter clutches, perhaps something might indicate this type of shaft could be considered.
 

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it is definitely possible to weld a driveshaft. I had to have a shorty made for my race car. They are setup and done on some type of a lathe. I would never attempt to do one. Just the slightest out of round and the life of bearings, seals and such is shortened tremendously. Not to mention a constant vibration.
 

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Something like a car the drive shaft turns pretty close to engine speed in high gear. I can see balance weights attached.
 

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I have welded the threaded rod that holds my 3 pt arm. I am lucky is does not have to be perfect.......

The hardest part in my opinion, was to weld it crooked enough that it will straighten when the weld cools
 

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Discussion Starter #10
Inner PTO shaft repair

I wrote last week about parting my inner PTO shaft on my '97 7ft. Farm King RFM. I received the replacement shaft and roll pin last week. The mechanical drawing suggested removing the roll pin and sliding the shaft from the yoke. As Lee Corso on ESPN's College Football Gameday says: "Not so fast, my friend..." We clamped the yoke in a vice, beat the shaft like a borrowed mule, applied penetrating oil, let it soak, then applied the old heat and beat method without joy. We found a very skilled mechanic who has a hydraulic press. We then removed a U-joint, exposing the shaft end and used the full 30 ton press to "slide" the shaft from the yoke. The mechanic suggested that the shaft may have been mis-sized for the yoke, given the scarring that remained. Thus followed a trip to the local implement store to procure a replacement yoke and U-joint. The mechanic ground a bit of paint from the yoke, polished up the shaft end, then pressed the shaft into the yoke using the aforementioned press. It took a very sharp drill bit to drill the pilot hole then the full diameter hole to accommodate the new roll pin. After about five hours of mucking about, I think I'm back in the mowing game. The mechanic is on vacation this week and was finishing up some other work Friday; We're very blessed to have people of his ilk in our part of Southern Ohio who will lend a helping hand for a very reasonable cost.

BTW - the shaft is triangular and is metric to boot. Replacing the entire driveline would have been $300 or so; I probably have $200 into the repair.

Brian :laugh:
 

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Intresting update. If someone was to remove the cross or spider which I think you are calling the U-jpint before going for help, or even at the onset there may have been other tactics. The shaft itself is about one eight thick in most of what I have. Cutting a slot lengthwise inside the part in the yolk makes stuff like that loose the forces causing high friction. A partial slot then pound with a drift and tear the rest perhaps. Even welding a few beads lengthwise inside should shrink it, you ended up trashing it anyway.

Do you know why it parted? Did you see drive shafts with slip clutches at the place that stocks triangular socketed yolks in metric sizes?
 

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Discussion Starter #12
Intresting update. If someone was to remove the cross or spider which I think you are calling the U-jpint before going for help, or even at the onset there may have been other tactics. The shaft itself is about one eight thick in most of what I have. Cutting a slot lengthwise inside the part in the yolk makes stuff like that loose the forces causing high friction. A partial slot then pound with a drift and tear the rest perhaps. Even welding a few beads lengthwise inside should shrink it, you ended up trashing it anyway.

Do you know why it parted? Did you see drive shafts with slip clutches at the place that stocks triangular socketed yolks in metric sizes?
Franklin- Replacing the spider may have been problematic given the roller bearings that were scattered everywhere when we removed it. I think that cutting anywhere in the cast iron yolk end would have made for a failure point down the road. We tried a couple of the methods you suggested, such as cutting a perpendicular slot in the shaft and beating a drift forced into the slot. We also discussed welding beads for access.

I don't know the failure mode; I do know that the relatively low cost of the yoke and spider made the sacrifice worth it to me. Getting back into the mowing game is what I was after and We achieved my goal. I'll be liberally applying the grease to the new spider and inner/outer shafts once it dries up enough to mow again.

I hope that you're not in the part of WVa affected by flooding; if so, I hope that the next round of rain misses you.

Brian
 
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