M936A2 crane hydraulic winch

[charlesmann]

As to not hijack other threads with different issues. Current and past issues have been the crane winch will not lift know load weights, less than the advertised capacity or 20,000 lbs, ie. a log CAT scaled at 12,400 lbs. Doing some research here i found where a member was having a swing issue, which latter found out, was not a hyd issue, but a mechanical issue. I followed the TM to adjust the relief setting for the crane controls and found the relief setting was around 550 psi, not the 1350 psi as stated in the TM, and adjusted accordingly.

I have not attempted to pick up the log with a know weight, but instead tried to pick up the rear end of my other 936A2 I removed the drag winch, both lift cylinders 3 of the 4 rear tires, and the entire crane boom, leaving an empty hyd reservoir and the rest of the crane structure. According to the title, and a scale receipt from when i purchased both trucks, the operational truck weighed just under 36,000 lbs. the crane boom weighs roughly, 3000 lbs, the drag winch, according to the load cell read out on MAEDA crane, 1500 lbs, and guesstimating around 400 lbs for the lift cylinders and around another 1200 lbs in wheel assemblies, two empty fuel tanks and pivoting on the front end, I am guessing the stripped down truck shouldn't weigh over 20,000 lbs with respects to using the front end as a fulcrum.

If guessing the load shouldn't weigh more than 20,000 lbs, and my winch line is a 3 part, giving me the supposed capacity of 20,000 lbs, and the boom supports in place. What could be the cause for the winch not lifting its supposed capacity? I now can however, lift the rear of the truck by extending the inner boom, as where before making the adjustment it would not lift the load.

YES YES, i know, i can cause damage to the inner boom by lifting a wt. that possibly exceeds the capacity of the winch, but the amount i have stuck out (16-18"), I'm confident won't damage the inner boom, and if does, well, so be it.

 

[charlesmann]

Updating/correcting the above, i am running a 3 part line. With that, i should have a 20,000 lb lift capacity, which i dont think i have, unless the rear weighs over 20k, but i just dont see it.

 

[Mullaney]

As to not hijack other threads with different issues. Current and past issues have been the crane winch will not lift know load weights, less than the advertised capacity or 20,000 lbs, ie. a log CAT scaled at 12,400 lbs. Doing some research here i found where a member was having a swing issue, which latter found out, was not a hyd issue, but a mechanical issue. I followed the TM to adjust the relief setting for the crane controls and found the relief setting was around 550 psi, not the 1350 psi as stated in the TM, and adjusted accordingly.

I have not attempted to pick up the log with a know weight, but instead tried to pick up the rear end of my other 936A2 I removed the drag winch, both lift cylinders 3 of the 4 rear tires, and the entire crane boom, leaving an empty hyd reservoir and the rest of the crane structure. According to the title, and a scale receipt from when i purchased both trucks, the operational truck weighed just under 36,000 lbs. the crane boom weighs roughly, 3000 lbs, the drag winch, according to the load cell read out on MAEDA crane, 1500 lbs, and guesstimating around 400 lbs for the lift cylinders and around another 1200 lbs in wheel assemblies, two empty fuel tanks and pivoting on the front end, I am guessing the stripped down truck shouldn't weigh over 20,000 lbs with respects to using the front end as a fulcrum.

If guessing the load shouldn't weigh more than 20,000 lbs, and my winch line is a 3 part, giving me the supposed capacity of 20,000 lbs, and the boom supports in place. What could be the cause for the winch not lifting its supposed capacity? I now can however, lift the rear of the truck by extending the inner boom, as where before making the adjustment it would not lift the load.

YES YES, i know, i can cause damage to the inner boom by lifting a wt. that possibly exceeds the capacity of the winch, but the amount i have stuck out (16-18"), I'm confident won't damage the inner boom, and if does, well, so be it.

.
For whatever it is worth, we don't really get straight up hard evidence of the specifications on these trucks. The crane in particular has problems where you get pictures of (for example) the rotation manifold. All you get is the outline shape of that part in the TM's. The valve body in the gondola is the same. Both of those parts are "pull and chuck" if they need repair.

In a past life when it was my job to repair cranes, we had (paper) books of exact specifications that were to be verified. The hydraulic pump was XX gallons per minute and a given number of PSI that should be tested and confirmed as step one of the verification process.

Then as step two, we had test ports that were to have installed gauge points. One on the intake port of the valve body was always used. Naturally the pressure before the body and check valves should be the same as directly off the pump. Any deviation there indicated hose issues (internal collapse, etc). We also had measurement points for the lift cylinders and rotation manifold in two places. One on the left or right rotation and another to release the rotation brake. Verifying check valve settings on each motion to be tested.

Several "step" points after pressure testing, we had weight boxes. Known quantities of weight. No guessing, real scaled weights.

All of this aimless babble just goes to say that we had step by step processes to test everything. Grove Cranes, Baker Corner Mount Derricks, Telelect Derricks, HiRanger Bucket trucks, etc.

I happen to have a M1089 that has a "known to be" Grove Material Handling Crane. It has a built in electric overload protection box. There is NOTHING in any book I have found so far - and Grove has no desire to give me any details on how it functions. Just guessing that the military has that information somewhere. Also guessing that if the military had a problem that info would be made available from Grove. On the other hand, me as a second hand buyer of a retired military vehicle (even if I get killed using it) won't be given that information...

It sucks. I wish it wasn't that way, but all we seem to be able to do it GUESS at everything on these machines.

 

[simp5782]

M1070 weight distribution puts each rear axle at 7,000lbs

My 816 had no issue holding it off the ground to do all 3 rear axle tires. It will lift the 17000lbs on the front axle to change both front tires without out riggers.

It will lift an 870 off the ground completely

An 816 is a much more powerful creature over a 936 though in my opinion.

TikTok - Make Your Day

 

[charlesmann]

I can build enough boxes to total up to 20k, but will touch base with any local crane places and see if they have certified wt. boxes.

It just boggles me it wont lift its advertised limit. I do hear a very noticeable audio change in my pump now that i adjusted the relief psi. It is much louder with a high pitch whine, esp as im reducing eng rmp from 17-1800 down to idle.

I will do a tap test on the suction hoses from the resv. tank, to the pump and put a test port somewhere between the valve body and the, “ i think its called” calumniator. If im not up to 2000-2500 psi, then i have a place to start.

 

[charlesmann]

M1070 weight distribution puts each rear axle at 7,000lbs

My 816 had no issue holding it off the ground to do all 3 rear axle tires. It will lift the 17000lbs on the front axle to change both front tires without out riggers.

It will lift an 870 off the ground completely

An 816 is a much more powerful creature over a 936 though in my opinion.

TikTok - Make Your Day

What would make the 816 more powerful in the hyd department than the 936?

 

[simp5782]

What would make the 816 more powerful in the hyd department than the 936?

All the bypass and reliefs on the 936s much like the 1089s and 984s they just give out at certain pressure.

The shafts that drive the pump on the 816s just seem to be stronger lifting even when running at idle.

I have had front tires off the ground 5ft in the air with the truck still lifting what it needed to. Even the Oshkosh 2206s.


Using the cable for your lift makes it lift more rather than trying to use the boom.

I prefer the 816 cause it will pull and pull till something breaks or it will roll itself over doing it. It doesn't ever give out.

wrecker 816 vs 936 whitch is better

Need some opinions on which truck would be a better purchase. I'm leaning toward the 816 due to the manual trans but alot of 936's are coming out. Will the prices drop on the 816's ? Thanks

www.steelsoldiers.com

 

[KN6KXR]

Well here's $0.02.....
-I think the TM is wrong about the pressure relief. I found mine from RSMS at 2100 psi. Tried the 1350psi in the TM it does not work well. Put it back to 2200psi works great. I think the TM is for maybe the 816 and never got updated.
-I can get the front tires off the ground with a pull straight aft. And hang it there, too.
-I have one of each of the motors. Old one on the rotator and new one (with the bleed port I had to run back to the tank) on the hoist. According to my local guy I had go through the rotator motor: that motor orings were built for about 800psi before they leak.
-One of the best things I did for tuning the crane was to attach a gauge with quick connect where the test port on the hydraulic block in the gondola is. Couple of 90's, couple nipples and a gauge. Now I can monitor the pressure when I run.
-I haven't been able to see a difference in 1700 versus 1900 rpm. You MUST be in 5th gear though. I usually engage and throttle up from the cab then head back. You can hear it drop in someplace after 1600rpm. Once there I think that's as good as it gets.
-That 20k rating is with the boom stays and boom pinned. Outriggers out as well.
-I talked to a fellow who ran a motor pool in the sandbox about their weight tests. He said they would grab the closest thing to 5k pounds, extend all the way, swing 360. If it did that they put the test date on the boom. So there's your spec I guess.

Hope that helps. As for my swing issue I did get hold of another rotator bearing but need another crane. So I'm repairing an old M543A2 in trade for it's use to do the job. It's in my spare time so progress is slow. I replaced the injection pump on the M543 and got the motor running just last weekend. Now for the brakes..... I envy you having another wrecker handy I'm going that direction.

 

[charlesmann]

@KN6KXR

Correct, 20k with all the stuff you mentioned in place, as per the tm.
I couldnt, or i should say, didnt keep going on the relief screw, once i hit 1350-1400.
I just left my gauge hard lined, and eventually, will extend it above the top cover plate, once im done testing the sys. to see what my high pressure side is pushing and i might even install a flow meter to see what my gpm is.

My main pump may be taking a crap. I could pull the pump out of my spare tck, rebuild, install and give it another try.
Down side to that though, the few hoses left, might decide to rupture with the potential increase in psi and maybe gom with a freshly overhauled pump.

 

[KN6KXR]

I just did an upside down "U" and the gauge hangs under the cover. Easy to see but out of the way so I don't break it. A flow meter would be good but not sure if the data is really all that relevant. I mean.... pressure is where it's at it'll flow what it will. I would consider flow at a pressure more of a bench test thing than a field tool. YMMV.

Hoses are just the cost of doing business I guess. Mine are pretty good but if they start getting soft I'll have 3k ones made for sure. Maybe even soft wrap them to keep them out of the sun. Shoot I should do that now.

Consider doing a UOA on the hydraulic fluid. Blackstone will send you a free postage paid sample kit and the basic analysis is about $40. Seems if the pump is failing you should see debris in the oil. Seems like low hanging fruit?

 

[charlesmann]

YMMV???

Yes, hose are a cost of anything hyd, esp. with unk age hoses.

I can get free oap testing and kits that we send our oil and hyd samples to. If i had a reason to send a sample in, i will. But i replaced the fluid a yr ago, minus what was in the lines and pump, along with a cleaning of the filter. Didnt see any signs of failure in the fluid after running it through filtration and cutting the filter open.

Yes, i know the tests an analysis lab does is more than just cut a filter open and look at it, but i saw no qty of metals that alarm me. I got WAY more metal out of my xfr case when i did a drain and flush than i did out of the hyd system.

The gpm and psi, i want to know for a couple future mods i wanna do, but having a flow meter to do a couple tests at different intervals and phases of operations might hint to something hidden.

 

[KN6KXR]

Haha yeah YMMV="Your Mileage May Vary"

New fluid now aren't you fancy! I did the UOA because I wanted to skip the expense if I could. If you have new fluid you're good. I think the stuff in mine is at least ten years old and it's fine.

Post up what you find please. Wreckers are particular I read and soak up as much as I can about them.

 

[charlesmann]

Haha yeah YMMV="Your Mileage May Vary"

New fluid now aren't you fancy! I did the UOA because I wanted to skip the expense if I could. If you have new fluid you're good. I think the stuff in mine is at least ten years old and it's fine.

Post up what you find please. Wreckers are particular I read and soak up as much as I can about them.

Fancy, no, cautious and preventative, yes. For the reason you stated, unk old fluid, plus i wanted to make sure there were not internals breaking apart, and pulling a 10 gal hot (15-20 min to allow for settling of contaminates) sample from the bottom and ran it through the filter.

Testing and such will be this fall/winter when the sun isnt dragging its a$$hole over tx a d it cools down. Hopefully before i go for back surgery, i can get this stuff done.

Once i get the numbers, i’ll post them up.