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M936 Boom Safety - No Check Valves?

Mullaney

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Safety First - So I don't kill myself or somebody else...

I am new to the M936, but reading the TM seems like the right thing to do. TM 9-2320-272-10 (Pages 2-136 to 2-140) show and explain the use of Shipper Braces that provide boom stability on the road. The TM also explains those other two arms for the boom (called Boom Jacks) that attach to boom then sit on the ground for heavy lifting.

In a "past life" I worked for a company called RH Bouligny. They were a steel high-line contractor (now defunct) that used primarily WWII era IHC's, Deuces, 5-Tons, Dodge Weapons Carriers and M4's. All were heavily modified for working where nobody else wanted to go. In the swamps and in the Virginia hills. I loved that job. Anyway, as the years went by I went from being a wrench turner to a hydraulic mechanic.

Earlier today, I raised the boom on my M936. Max up with Max extension on the Crowd Boom. The great news is that there was no "popping" sound as it sat there. No obvious leaks - although I can't imagine why because the deck is pretty nasty. The boom sat like that for about 4 hours. I was preparing to stow the boom and decided to climb up and press the far left lever (boom control) forward to verify that the check valves were functioning correctly. It should not have moved - but it did. This boom does not appear to have check-valves?

Everything we used had "CHECK VALVES" in the lines where a boom was in the air. Where a catastrophic hydraulic line failure would cause the boom to come crashing to the ground. Again, this truck does not appear to have that safety feature. Is that normal?

Picture below shows the M936 lifting without the Shipper Braces. It is a rotator. If they hadn't intended it to be able to pick and swing - the Shipper Braces would have been attached permanently - right? One of the uses for this truck is to remove and replace a 5000# rocket pod from a MRLS. Pick from behind, rotate to the side, drop on the new pod... Rotate being the key.

Just thinking out loud here, but I would think dropping that - if a hydraulic hose busted would cause a really bad day.

Wrecker Operation Pg2-136.jpg
 
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simp5782

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The holders that were on it when I dropped it off were for transport. Not lifting. There are actually boom jacks for heavy lifting


@Csm Davis has them available.

When lifting you try to not use the boom lift for heavy items that could blow a hose.

Wrecker boom height should remain in the same spot while lifting and use the winch on the boom. It is stronger than the boom Hydraulics. Then you bring the crowd to bring it lower/closer
 

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Mullaney

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Thanks Wes. I agree 100%. Shipper Braces (holders) are definitely just for transport.

The TM does specifically say that "heavy lifting" should be accomplished using the winch and not lifting with the boom hydraulics. It also specifies the use of a pair of Boom Jacks as well.

Thanks for the lead to CSM Davis so I can pick up a pair! I have one "foot" back there and a pair of spades - but nothing else :-(
 

simp5782

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Thanks Wes. I agree 100%. Shipper Braces (holders) are definitely just for transport.

The TM does specifically say that "heavy lifting" should be accomplished using the winch and not lifting with the boom hydraulics. It also specifies the use of a pair of Boom Jacks as well.

Thanks for the lead to CSM Davis so I can pick up a pair! I have one "foot" back there and a pair of spades - but nothing else :-(
@Csm Davis has a full basic issue item wrecker setup he can set you up with.
 

Csm Davis

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Okay so as to the check valves I am 90 percent that they are there but as you said for a catastrophic failure not the easy down of the control valve, yes they are supposed to come down when the truck isn't running and you push the lever. It is not a power down system. Pretty sure if you get a good load on the boom and go full down you can make them catch but fair warning you can bend the boom if you shock it hard, so I would suggest around 750 lbs or so to test them. I have the boom test for the Army around here somewhere, but I have slept since then.
 

Mullaney

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Thanks CSM Davis. If you happen across that Army Boom Test manual, I would love to have a copy. I didn't crawl around on the deck. It is still somewhat nasty. Fixing and cleaning as I go... I will get down there and look for the valves.

I won't be shock testing the boom! Awful lot of things that I don't know about these new iron horses, but hydraulics I do understand. Everything is done gently. Ease back on the valves, swing slowly and plan a gentle stop... Hydraulic winches get the same treatment and you should never hear the crowd boom "go thunk" inbound or out either. :cool:

Completely unrelated, but I have been teaching my son to operate our fork truck at work. First time he was in the seat, he was bumping (yank, snatch jerk) the up valve. I almost stroked out!! Explained slow, easy and gentle... We definitely got that problem solved PDQ!
 

zebedee

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Thanks Wes. I agree 100%. Shipper Braces (holders) are definitely just for transport.
... AND for suspended towing (could be considered "transport" I guess) - that's why they are adjustable in height. They stop forced swing on corners and shock load on the boom cyls when recovery off road etc.

Testing procedure is :- allowable creep (ie., hyd fluid lost past cyl/valve seals), at test load (no idea how much), over set duration (don't know that either!!!).
 

Mullaney

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Thanks Sir! I had found that "support for towing" last night in the TM. Little one line statement. Guess they figured the operator would have gone to school - or maybe have been ground crew on the machine.

The testing specs seem reasonable. At least it is a measure of how bad it is or isn't.
 

Mullaney

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When I do a display at a show or an event I use a clam shell safety thing I made that I put over the bloom HD cylinder so it will not come dwon it someone pushes the controls.
Absolutely! Your version even has a "lockout tagout" tab on it... I just have to make sure to avoid the soft metal where the seals live. That is definitely the way to go!

I have made those in the past but they weren't nearly as nice. Mine were hack jobs with a big pipe and a torch. That hinge and locking tab is definitely FIRST CLASS!

Hopefully with permission? I am going to build myself a pair of those...
 

M35A2-AZ

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Absolutely! Your version even has a "lockout tagout" tab on it... I just have to make sure to avoid the soft metal where the seals live. That is definitely the way to go!

I have made those in the past but they weren't nearly as nice. Mine were hack jobs with a big pipe and a torch. That hinge and locking tab is definitely FIRST CLASS!

Hopefully with permission? I am going to build myself a pair of those...
Sure, more then welcome.
 

Mullaney

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Sure, more then welcome.
Better than that.... Don't know WHY it didn't dawn on me before: Would you m35a2-az be willing to build a pair of those clam shell sleeves for me? Obviously not free... I have more than enough things to work on and fix.

Today I got the 4th "screw jacks" unfrozen (picture below). Yesterday I got the second (of four) outrigger slides out of their pockets. Yes sir, I definitely have plenty of projects and would be happy to pay you to build those safety sleeves if you have the time and inclination. ;-)

All Four ScrewJacks UNSTUCK!.jpg
 
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