M936A2 boom extension

[charlesmann]

has anyone attempted to add a jib to their wrecker boom? i need about 25 ft of stick with a lift rating of 2000 lbs, i was thinking, if i add a 10' jib, single part my cable and wind new, longer cable, i could get the length needed. thought?

 

[charlesmann]

out of all the mods folks have done, aint none of yaw got any insight to share? only reason for even thinking bout adding a jib is. our chilean bird is coming home by ship and the port cranes are expensive by the hr, and if we are down for any short amount of time, the crane will go to another job on the docks and no tellings when we would get it back. iv called several rental companies and no joy. haven't had time to call a crane and rigging place to see if they rent out their boom/crane trucks.
all we should have to do it put 6 blades on, but things happen and something could have gotten damaged during shipping or as with head seals, they could decide to leak and reseal after a ground run. either way, we are 19.6' to the top of the aft rotor and i need another 5-6' for blade cradle and a lil cable up room.
this extension is a last ditch attempt to make mission happen, but i'll only have about a wk to get it built, yank part my rear hubs, repack the bearings and get down to beaumont.

 

[zebedee]

Yup - I did it for my M816 so I could place timber roof trusses over the "House Of Wrecker" (The "Cottage Name" slate my wife got me for a present) as I built a lean-too which was then where I am tearing it down for restoration.

Don't know I still have any pics - previous lap top crashed.

HOWEVER - I think your plan for 2000lbs is excessive. I got an extra 18'-20' but the trusses were only low 100's of lbs.

I still have it so can get some pics of the components. I did not cut, weld or drill the original boom. It was all done using existing features, holes etc.

 

[WildernessJeep]

Do some simple moment of force calculations. A three meter extension with 2,000 pounds on the end is the equivalent of ~20,000 pounds on the tip of your fully extended boom. You would far exceed the mechanical limitations of the truck, which is dangerous with helicopters and things. Just get the local crane guys to hoist it for you.

 

[charlesmann]

Do some simple moment of force calculations. A three meter extension with 2,000 pounds on the end is the equivalent of ~20,000 pounds on the tip of your fully extended boom. You would far exceed the mechanical limitations of the truck, which is dangerous with helicopters and things. Just get the local crane guys to hoist it for you.

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yea, i did some calculations after zebedee sent me his reply. didn't get away from the hanger till a few hrs ago. yea, i probably wouldn't be able to lift even the head (900 lbs w/o blades), but a 350 lb blade and a 30 lb cradle, I'm sure it'll handle. as for using the local crane guys. we've tried that several times in the past, and it didn't work out well. we were loading a chinook hull onto a trailer to truck back to the west coast and they dang near dropped the acft off the edge of the trailer. claimed he couldn't see the ground guide. a few other times was installing blades and 1 guy his hand crushed between the pitch arm and the root of the blade. we told the crane operator where to set up and he didn't like it, so set facing the sun and couldn't see the hand signals for him to stop the swing. since this is my show this time, it'll be 1 of our guys, or me running the crane. the company is trying to get our mieda crane trucked to us, and we will just load it in the cabin and ferry it back. but thanks for the online calculator. i did it the old school way (pencils and paper) and came up with a slightly lower (still greatly exceeded limits) number. i forget about the online stuff, mostly bc the inter web isn't always where we are, and the old pencils and paper format works even with no electricity. again though, thanks for the calculator.

 

[charlesmann]

@zebedee
if you don't mind, if you can find the pics or find the sketch, that would be great. i do have some trusses in i need to install for an add on lean-to for my shop. last time i had to put up i-beams for the roof of my shop, as i was trying to shift the beam to its final position, the beam fell off the support leg, fell on foot, throwing me off balance, luckily, the house was 2' away and was able to catch myself before the beam dragged me off the conex and onto the ground. my next attempt, i kept the tractor fork under the load, and curled so if it fell, it would have slid backwards. doing sky monkey work alone isn't the best option, but only option i have.

 

[zebedee]

This the bare bones design for my fly jib - good enough for roof trusses. - Length of fly jib, height of goal post and lengths of tethers should be proportional to your needs. I can measure my pieces later if that will help. Try a search in wrecker mods for fly jib - I think I did a similar drawing several years ago.