Can I shorten a solid splined PTO shaft and re-weld?

[RichardDLee]

Hello,

I have just bought a second hand Yanmar RS 1303 tiller in pretty good condition. The problem is that the PTO shaft is too long.

Now it's not a regular new type of shaft which is nice and easy to shorten, it's a solid cylinder of metal splined for the last 6 inches and just plain cylinder behind that.

My question is...... Can I cut out the non splined cylinder section and reweld the splined section back onto the shaft?

I will only be tilling for a few hours a month, not constant or daily use.

Will it be impossible to get straight? Will I just ruin bearings?

Will it be strong enough to hold?

I bought a new PTO shaft but I realised that the 2 yokes length was the full distance between tractor and tiller, this tiller was meant for my tractor so why is it not easy to get the correct shaft?
The distance between the 2 bolt cut outs on each splined when mounted is only 420mm, am I being daft?

Somebody please help.....

Thanks.

 

[Shield Arc]

I'm not quite catching onto what you want to do, can you post a picture of the shaft, and mark where you want to cut it?
Never did a PTO shaft before, but have done drive lines for trucks. I take them to a drive line shop for balancing.

 

[Jesse masterson]

try it!! Worst it can do is break! I've welded similar hardened metals before with good results but the heat can cause it to become to brittle! Never know! 7018 can do a lot!

 

[Soundguy]

I'm not quite catching onto what you want to do, can you post a picture of the shaft, and mark where you want to cut it?
Never did a PTO shaft before, but have done drive lines for trucks. I take them to a drive line shop for balancing.

what he's describing is a setup that will need the tube seperated from the yoke, cut that end and reweld to the yoke. at the mating section there is only a short section of collar at the front of the tube wher ethe inner and outer couple

 

[RichardDLee]

Hi,

Yes I need to cut it off the yoke, remove six inches of non splined cylinder and weeks the splined section back onto the yoke.
Leaving me with a six inch splined shaft rather than a 12 inch shaft, where 6 inches are not splined and six inches are splined.

If I just cut the end off, I'd be cutting all of the splined section off leaving me with a useless cylinder.

I can get a picture in the morning.

Thanks everyone.

 

[Ed of all trades]

I have replaced the old 1" square shaft and used the old yoke, should be the same thing and we had no problems at all. Just make sure you are centered on the yoke.

 

[JCByrd24]

I'm assuming the yolk is welded on currently otherwise you'd be going about this differently. I'm also assuming originally there was a hole in the yolk to make it a relatively brainless operation for the assembler/welder. If so it will be easier to keep straight if you grind the weld off and remove the tube from the yolk. This will give the same assembly method as factory original rather than trying to splice the tube. May require a little more work but will be better in the end.

 

[LD1]

What is the gearbox on the tiller like? Is it the same as the tractor side with 1-3/8" 6-spline?

In any case, you can likely get a new shaft for under $100 delivered. Then cut to length.

Just mentioning this in case something goes wrong. IF It were mine, I'd try to cut and weld what you have first.

 

[LD1]

What is the gearbox on the tiller like? Is it the same as the tractor side with 1-3/8" 6-spline?

In any case, you can likely get a new shaft for under $100 delivered. Then cut to length.

Just mentioning this in case something goes wrong. IF It were mine, I'd try to cut and weld what you have first.

 

[Sodo]

Now it's not a regular new type of shaft which is nice and easy to shorten, it's a solid cylinder of metal splined for the last 6 inches and just plain cylinder behind that.

I did exactly what you are saying ( if I understand you correctly ). Here's how I'd describe the PTO shaft that I shortened. It has a yoke (with a u-joint) on the tractor end, and a simple PIPE connecting the middle, and a splined insert welded to the other end. I shortened it by cutting a section of the pipe out of the center. Then welded it back together.

Yes you can do this easily. Clamp the pipe sections in an angle iron to align it, and tack it lightly 3 or 4 times around and convince yourself it looks straight before welding the circumference.

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I hope this is understandable. It's perhaps the MOST important detail of the simple project you propose.

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There is a very important detail here, FAR more important than a few hundredths of runout in alignment. You MUST maintain the "timing" of the U-joints. This is not a critical alignment, but you should be able to get it within 1/8" or 1/16" pretty easily and it will run perfectly quiet (for a PTO). It's not a driveshaft on a Cadillac.

But if you happened to weld the two halves together a full 90 degrees out (the worst possible chance alignment), you could destroy the shaft and all your u-joints and woodruff keys and crossbolts and gearbox in a matter of minutes. See the pic below, which shows a similar arangement of timed u-joints. You need to look at your shaft parts and end up with an alignment (of the yokes) like this.

When you bend a u-joint, it causes a pulsation in the rotational speed. For something like a steering shaft, this is not very important, but for a shaft rotating 540 RPM this is a big deal. When a pair of u-joints are timed, each u-joint 'cancels' the pulsation of it's companion u-joint. In the special condition that the input shaft and output shaft are perfect parallel, this cancellation is "perfect" (to "zero"). Normally any attachment that uses u-joints will try to maintain the input shaft and output shaft "parallel" over the course of their range of movement, and especially aligned "parallel" while doing the "work".

OTOH, if you set (in error, and welded) the u-joints 90 deg out of alignment, each u-joint's pulse would ADD ontop of the others pulse, and the pulses are DOUBLE intensity. Around zero degrees, it will be a quiet shaft.

Heres another pic, not welding but showing how u-joints splined together, the proper spline position must be chosen upon assembly. Typically a PTO shaft will have a "rectangle" assembly that ensures it can only be assembled 180 degrees out (=zero) and never 90d or 270d.