Taking hydraulic motor apart for new seals

[Richard]

So I have an old 15 foot 'Terrain King' (now owned by Alamo) hydraulically powered flexwing mower. (a speed increaser attaches to PTO and hydraulic pump attaches to increaser then powers the blades)

Cut a field a week ago and noticed that one blade section cut like a ginsu knife.... the opposite wing cut like 50% and the center section was strange, it didn't cut much, just ripped up some of the taller stuff (think knee height).

So I presume the motors are at issue since if the primary pump didn't work, none of the blades would work. None the less, they might all need attention!!! So I'll start at one end and see what happens.

Here's the motor after having taken it off the housing (the lower part of the housing is what the blade carrier is attached to)

I have NEVER ever done anything like this but presume it can't be too complicated.... Note however, most of those bolts are UNDER the lip of the top section. Can't get to them with my impact. My crows foot is also useless.... this is going to be brute force with a box wrench (and these things are TIGHT AND old)

I don't know the names of the parts....but the two side "boxes" (fluid input and output) have to come off as well as the pressure relief (which is what it's currently sitting on.....on top/bottom) I took all the attached items off. The two side boxes had a single O-ring and the pressure relief box had three small ones, about the size of a dime. No picture of that one!

So my impact wrench was utterly useless on these bolts that connect the halves together. Crows foot also useless.... what to do? The instructions (yes I have a manual and actually read it!) calls for putting this in a vice. Guess what I don't have. So.... maybe I can get some leverage by holding it and using a longer "bar" (wood clamp) to hold it from twisting as I try to turn the bolts...... didn't work.

BUT ALAS.... I am a persistent little fool and willing to keep fighting the fight. Besides, I have a backhoe. What on earth you wonder, does a backhoe have to do with this? Well.....think of those threads where people ask about uses for a backhoe.....are they "REALLY" that useful???

HA! I laugh in thy face!!

Yet another useful use to add to the "why should I buy a backhoe" question.... I put some wood down, put some wood on top and clamped it. No, I didn't put the 16,000 pounds of weight on it (or whatever the machine weighs) BUT, I was able to hold the motor in place while I took my box wrench and pounded on the wrench with a 5 pound hammer and finally got the bolts loosened up. I then had to flip the motor over to get the other side.

Now, reading the instructions, they say "place thumbs on the shaft, grab the lips of the top half and gently pull straight up. If it's stuck, you can tap it with a wooden or rubber mallet. Well.... that was written for Shirley Temple.... this thing wasn't coming apart. Hit it with the rubber mallet....I DID finally see an edge of light but my poor little thumbs didn't have the strength to push it through.... so.... pulled out the puller and came off easy-peasy.

I might add... I'd noticed a leak on the underside of the mower, where the blades come through. This suggests to me that this motor is leaking which means I need bottom seals which is really why I'm doing this. So back to directions.... "gently tap on the lower gasket all the way around to tap it out from above" (OMG, who writes this kind of stuff..... yeah yeah.... I tapped it into gasket purgatory.

Might be worth knowing I'm taking the guts of this to the hydraulic shop and buying three sets of everything so I can do all three motors. Now the directions call for you to "go back to your vice" (uh oh....) and use the vice to press fit the new lower seals in. This might be an issue. This was VERY difficult to extract (both of them) and no, I won't smash it with the backhoe stabilizer.... I might take it to my machine shop friend but don't want to impose. I might buy an extra set of them and see if I can simply tap them in with the socket method. If I booger it up, I'll have a spare for a new plan "B"

Now....what I can't yet decide......do I take the impellers apart? As best I can tell from the instructions, there aren't any seals in that section. The instructions DO show how to take it apart.....but I'm thinking there's no need to if there are no seals in there....after all, why take it apart to just put it back together? If I'm wrong on this, I'm happy to hear input.

Here's what it looks like when split. I've already removed the O-ring.
Did this yesterday so don't have the replacement seals yet.

 

[Richard]

Oh, and the thread "Harbor Freight Tools that DON'T Suck"......

We will NOT have their Crows foot wrenches on that list.....because they DO suck. You can see my cheater bar in the tractor tire picture.... I snapped the 3/4" Crows foot in half. Given how contorted I was trying to use my knee & body weight to help hold the motor in place and my other arm to apply the torque.....and the foot snapped....

To add insult to injury, both of my arms are now what I call 'noodle arms'. I've had surgery on one shoulder, broken the upper (large) bone on the other arm, broke a wrist... so I don't have anywhere near the strength I once had (getting older doesn't help either!!)

Heck.... your 3 year old child/grandchild can probably beat me at arm wrestling.... and this damn crows foot snaps. I'm glad these are the only things I have from HF.

 

[oldnslo]

Richard
The main leak point on gear motors is between the tip of the gear teeth and housing so would suggest carefully removing the gears from the gear case and looking for wear. Typically the shaft bearings get slightly oval from pressure pushing the gears towards low pressure side and this allows the teeth to rub and also make the gear case slightly oval. This wear allows oil to slip past the gear teeth and the motor runs slower under load.

great write up how you managed to take that motor apart.

 

[Richard]

Thanks...

Question, keeping in mind this is my first disassembly.... will these things be evidently visual?

(obviously if it's egg shaped that should be visible) but what I mean is are we talking in the thousandths? How tight do the tolerances need to be? I don't know how old this thing is but I'm guessing it's from 1983 given the manual that came with it (someone hand wrote that on top)

I'll try to take it apart & give it a look-see.

 

[oldnslo]

Richard
Not exactly sure on tolerance but the brass colored pieces are side loading plates for the gears and have the blueish colored seal on them when you slide those out you will see or feel a step in the bore where the gears run. Bore should be same diameter for seal plates and gears.

take pictures or notes so that you do not put those side plates in the opposite way they come out.

you are doing great for first time on the disassembly of this motor

 

[Richard]

Question.... would it be reasonable to expect a hydraulic (or pump repair) shop to have access to these type parts? (are they common?)

Edit to add: I think this mower was made in 1983 if the handwritten date on the manual means anything. I know that Alamo doesn't support it anymore.... they had a kit you could order that had all the needed parts (evidently)

 

[ptsg]

Once a gear pump or gear motor eats the housing around the gears, there's usually no hope for it to be repaired again and has to be replaced with a new unit.

The wear will be visible once you take the gears of the housing. You'll have the good surface where the figure 8 bronze parts sit to compare with the possible worn out surface where the gears work.

 

[Richard]

Ok, so your kick in the pants is all I needed. Dont' have much to lose, this isn't too complicated (for how it's put together) I laid down a board and as I took a part off, put it down in perspective and in order. I just reassemble in reverse. So...what happened?

I took out the little (plastic?) wishbones that were imbedded in the brass thing.

Viola...now I can see the full gears. To my highly sophisticated & trained eye (HAHAHAHAHAHAHAHA) Nothing seems outwardly obtuse here but then.... I didn't know one day that a flying object was flying towards my face at an incredible speed and would leave harsh red marks... such is a slap in the face!!

Let's yank them out and see what we see. Are those ground markes from fabrication (doubt it) or are the gears grinding? Shrugs shoulders. The gears don't show any obvious grinding issues. But then again, not knowing exactly what I'm looking at/for nor how obvious it might be...

Oh, and now we're down to that pesky Shirly Temple separator that the book simply says "insert both thumbs and gently pull up without bending" I swear, if I had Godzilla thumbs....I could first breath fire on this and then maybe wiggle it out.

Time to go to my tool box and look for a cheater to get it started. Ah... found something. Got it wiggled loose and pulled out. HOWEVER, unseen in this picture is UNDER this item, I saw what looked deceptively like a piece of O-ring material that was trying to hide from view. HUH??

Another beauty shot... I couldn't decide if I should use a flash or not. Do you see my little culpret in there trying to look innocent?

Seems I can't attach any more pictures??

I know a way around that!

 

[Richard]

I see you responded... I've not read it yet, I'm on a roll!


Here are the gears

another cavity shot

What I found at the bottom of the barrel!! (though I don't know how significant this might be???)

 

[Richard]

You'll have the good surface where the figure 8 bronze parts sit to compare with the possible worn out surface where the gears work.

So I'm inferring on what you've said that I've not really looked at the right parts yet. I need to go out and look at the shaft where the bronze parts reside and see if (maybe with them installed) there appears to be any free play??

Even if that's not what you meant..... tis where I'm going now that I'm curious.