New problem with broom - lost hydraulics

[dstig1]

So I was using my broom to clear the 4" of snow we got overnight and was going along fine. I get down the drive and back up and at the top use my momentary switch to swing the angle from right to left (it was full right and I wanted to go full left) and it moved left and then stopped dead. This is done with a diverter that pushes on a double acting angle cyl to swing the broom head. Done it plenty of times, but held the switch down longer than normal for the full side to side swing. Now I got nuthin'

Had the wife look at the PTO shaft while I was in the seat (can't leave the seat or kills the tractor) and she says it is spinning plus I can hear it. Gage right after the pump reads dead zero. Not even a blip when you engage the PTO. Broom won't spin and can't angle the cylinder either, not surprisingly with zero pressure. I pulled the whole thing off the tractor but haven't dug into anything yet. I did check fluid in the tank, and it is at normal level. Temp was pretty low on the fluid (as in not overheated but was around 70 F not not cold and thick either). I'm thinking internal pump failure, but this thing has less than 20 hrs on it so far. (Go look up my build thread in Build It yourself if you like.). I think the only next step is to drain some fluid, remove the pump and open it up to see if there is anything in there that blew up. I am puzzled by this as it has been working fine and I wasn't over-speeding it or anything crazy, plus the hydraulics have a pressure bypass valve at 2000 psi, so it should just bypass and not explode if overloaded.

Anything in particular to look for or any ideas what may have caused this? More to come but it may be a bit until I can get it drained and apart.

 

[Doaaj50]

Do you happen to have any pictures of where you were measuring the pressure at?

If a pump is really at 0 psi the shaft would be broken or not spinning for some reason. Typically you would have some flow out of the pump and should build up some pressure. A shaft can break but unless it has some sort of defect, running the pump at relief pressure should not do that type of damage.

Was there any noises that you heard when then system stopped working?

Any diagrams that you could provide would also be helpful. I am not as familiar with Kubota systems.

 

[oldnslo]

If I remember correctly the diverter is tied into the motor circuit. Does the swing cylinder hold position now or can you move the broom by hand? Just wondering if swing cylinder could have failed internally and jamed the diverter now allowing flow through cylinder vs the motor. Long shot but should be simple to check.

Other thing is confirm pump is spinning and that a key or something didn’t fall out so PTO shaft is turning but pump is not.

 

[dstig1]

Do you happen to have any pictures of where you were measuring the pressure at?

If a pump is really at 0 psi the shaft would be broken or not spinning for some reason. Typically you would have some flow out of the pump and should build up some pressure. A shaft can break but unless it has some sort of defect, running the pump at relief pressure should not do that type of damage.

Was there any noises that you heard when then system stopped working?

Any diagrams that you could provide would also be helpful. I am not as familiar with Kubota systems.

If I remember correctly the diverter is tied into the motor circuit. Does the swing cylinder hold position now or can you move the broom by hand? Just wondering if swing cylinder could have failed internally and jamed the diverter now allowing flow through cylinder vs the motor. Long shot but should be simple to check.

Other thing is confirm pump is spinning and that a key or something didn’t fall out so PTO shaft is turning but pump is not.

Yes, this is fully self-contained and does not interact with the tractor hydraulics. The PTO drives the pump on this. The diverter is therefore tied into the motor circuit, as that is all there is for the entire system.

I have not tried swinging it by hand but it did not seem to want to move on it's own while carrying it around on the FEL. The diverter should lock the cylinder fluid passages so I do not expect that it would be movable normally when the diverter is at normal motor position. And the fact that there is zero movement at the pressure gage tells me there is no flow at all. Normally I see near 500-1000 psi when spinning the broom in air. Pressure gage is immediately after the pump (after a 6' hose) right at the pressure relief valve.

I have not yet tried turning the pump by hand but need to. It is a splined shaft and appeared to be intact.

No major noises that would indicate an explosion that I noticed. Probably a clunk or something was all.

Everything was covered in snow and soaking wet, so i was going to wait for it to dry out first and then take a look more closely. Just looking for any thoughts ahead of that on what to look for/consider.

Thanks for the thoughts.

 

[oldnslo]

Dave
Agree on diverter being a slim chance but typically gear pumps don’t just completely fail. I did not follow your build post completely but is there any valves to start and stop or reverse the broom? If yes these could be suspects also.

 

[mrmikey]

Shaft didn't spin on the splines by any chance?

 

[dstig1]

Found the failure point. Pump splined shaft looked ok but a little dinged up plus some smeared metal in the splines. Couldn't turn it by hand (still connected) so I doubt anything internal is bad. Went and stuck a finger in the PTO shaft spline coupler and it was totally smooth, so the coupler spline sheared off. Next question is why?

I put power to the diverter and heard both circuits click with 12 v on each side so I'd guess it is not jammed up.

Need to order some parts now and see what I can do to repair the shaft. But no idea why it failed yet. Maybe my welding annealed it too much or something.

 

[oldnslo]

Interesting failure, if you try to file the PTO internal splines do they seem soft?

Welding could have annealed them.

 

[dstig1]

Looking up the parts I bought to weld up into the shaft coupler, it says "Made from machinable & Weldable Cold Rolled Steel" so that means unhardened mild steel. Methinks that is not strong enough for this application... Not sure where to find anything better so I have a lot of searching to do. This was one of the hardest things to find the first time around, so I may have to replace with the same and just be more careful (and keep a spare on hand)...

 

[oldnslo]

If the pump has a standard spline I believe companies like Dana Spicer, Muncie and others make yokes for them. If you have drive line (shaft) company in your area they could possibly provide one or make a drive shaft for you.

 

[dstig1]

Here is what the shaft looks like currently. I welded adapters onto the end for the pump. Pump is at the bottom of this pic. This was before I welded up the coupler. There is a solid 3/4x7/8" shaft coming out of the U-join yoke. This is welded to a shaft adapter and then welded to a 7/8" x 13 Tooth spline adapter that the pump slides into. Splines seem to be a dark art corner of the machine part world. I have found an SAE B spline that I think is the same as this pump shaft but cannot find any confirmation that these 2 are actually the same as of yet. It should be a standard shaft.

You can see where the pump mounts and the spline coupler that is now stripped sits:

 

[Doaaj50]

First of all, I am glad to hear you tracked down the problem.

One phenomenon that occurs on shafts is fretting corrosions which can lead to a spline failure. I have seen this many times between mating shafts that have relative motion between them. A tell tale sign of this is you will find a reddish/brown powdery residue on the mating shafts.

You can greatly reduce that failure by applying molybdenum disulfide grease to the splines when they are assembled. Keeping it greased regularly is also recommended.

 

[mrmikey]

Wonder if it's lack of or no lubrication? When I had my Goldwing (I think it was) the service manual insisted on Moly paste. Apparently it works on the molecular level and actually deposits itself on the splines so it's not metal to metal wear?
Just looking at your pic. If I was a betting man I'd say shaft alignment, you'd only have to be of a couple of tho and the splines would be constantly working up and down. I think there should be a U joint between the last bearing and the pump. My thoughts would be to turn the shaft around so the U joint is at the pump and turf the last mount with the flange bearing. Just my opinion so take it for what it's worth

Just noticed Doaaj50 mentioned Moly grease also...I gotta learn to read all the post ;-)

 

[k2man]

Did you make your splines in the shaft yourself? Did you make the mating splined hole? How many splines (grooves)? To transfer power, more splines are generally better. Matching the shaft splines to the hole grooves is also critical. I didn’t see a photo of your shaft.

 

[ArlyA]

Interesting that the shaft or splines failed. I'm following this to see how.

 

[oldnslo]

Dave
SAE - B 7/8” 13 tooth 16/32 pitch is a standard spline. Does your pump have a tapped hole in the center of the shaft. Not sure if all companies add this feature. If yes this can be used to hold spline yokes onto the pump.

I agree with others in suspecting you need a U-joint on both ends of the shaft connecting to the pump.

Nice job on building that frame to mount every thing

 

[mrmikey]

Nice job on building that frame to mount every thing

I meant to add that also, very neat professional looking job

 

[Doaaj50]

Another alternative to a u-joint could be to install an elastomeric coupling between the pump and the bearing. As long as your misalignment between those two shafts isn’t significant, a coupling with an elastomeric center could work.

The other advantage of a coupling is that it is very configurable. You find one hub that matches your pump spline and the other that fits your stub shaft coming through that last bearing and then the elastomer connects the two together.

Lovejoy or Rexnord would be two coupling manufacturers that you could investigate further if you are interested in that path.

 

[mrmikey]

Another alternative to a u-joint could be to install an elastomeric coupling between the pump and the bearing

That's an even better alternative, or a chain coupling. I believe a Lovejoy is more forgiving tho:

 

[ArlyA]

That's an even better alternative, or a chain coupling. I believe a Lovejoy is more forgiving tho:
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View attachment 775153

I like your solution.