Recovery and Towing

[cosrec]

I'm not to well up on the towing arrangement on that truck but to me it looks like by attempting to pull the Disco out with the winch/tow rope quite high up has transfered the forces generated to the weakest point which in this case looks to be the mid point of the chassis, add to this the front being chained to the front vehicle has caused some damage.

 

I can see what they were attempting to do and I've done this many times myself, attaching 2 vehicles together and using their combined pulling power to rescue a bogged vehicle. Now this should only be attempted if you know what your doing and full control should be exercised over the drivers of all 3 vehicles, ie 1 man in control of the job, as long as everybody is driving in the lowest gear possible, in low range all axles/diff locks etc in, then it should be ok. This shouldn't be attempted when trying to winch a bogged vehicle out.

 

I would always prefer getting the winch out in most cases as it's safer, more controlled, less likely to cause any damage and easier to stop if something looks like it could go wrong.

 

If you look and listen closely they are using the winch on the wrecker but its stalling thats when the big guy junps in and tries to drive and yank it out. To me its just abuse of equipment. There is still another winch on the back of the wrecker (its a twin boom wrecker) not being used bit of thought and rigging that should have been no problems with that job

[recymech66]

If you look and listen closely they are using the winch on the wrecker but its stalling thats when the big guy junps in and tries to drive and yank it out. To me its just abuse of equipment. There is still another winch on the back of the wrecker (its a twin boom wrecker) not being used bit of thought and rigging that should have been no problems with that job

 

Yep seen, haven't got any sound on the computer I'm watching it on, I was assuming they were trying to pull it out with both vehicles as the front vehicles spinning his wheels. Seems to me that the trusty shovel would've made some difference if the wrecker wasn't up to the job.:-D

[antarmike]

It would have made sense to fit the recovery gear to the wrecker properly. This should not have happened with what they are doing, (though I don't think it was very sensible.. It is not how I would recommend going about it anyway)

 

I suspect no proper super-chassis has been added to spread the forces from the wrecking gear, Inadequate flitch plates and so on.

 

I suggest it is more down to making sure the gear is up to the job, making sure that the converted wrecked has been adapted with enough extra metal where it needs to be to stop it pulling apart, rather than a problem with technique.

[cosrec]

Yep seen, haven't got any sound on the computer I'm watching it on, I was assuming they were trying to pull it out with both vehicles as the front vehicles spinning his wheels. Seems to me that the trusty shovel would've made some difference if the wrecker wasn't up to the job.:-D

That thing with the wheels spinning seems to be a misconseption that two wheels spining can hold better than four with with the brakles on (dont think they have cross axle difflocks). Agree a bit of ground work would have helped.

[cosrec]

It would have made sense to fit the recovery gear to the wrecker properly. This should not have happened with what they are doing, (though I don't think it was very sensible.. It is not how I would recommend going about it anyway)

 

I suspect no proper super-chassis has been added to spread the forces from the wrecking gear, Inadequate flitch plates and so on.

 

I suggest it is more down to making sure the gear is up to the job, making sure that the converted wrecked has been adapted with enough extra metal where it needs to be to stop it pulling apart, rather than a problem with technique.

 

Probably a lot of truth in what you say about a subframe not being fitted. In the vidieo you can see the vehicle start to rise and then lower as the winch is let out a couple of times

if a snatch block had been in the system it would easilly have reared of the floor.

But i will stick to what i said if you have a vehicle winching out the back and it is holding to the piont where it starts to rear, tethering the front will cause it to bend at some piont. I used to own a scammell crusader fitted with an eight inch box subframe that bent just above the rear axle bump stop trying this method. Although i got away with a lot of times before that on various vehicles So my advise is dont do it

[paulob1]

Probably a lot of truth in what you say about a subframe not being fitted. In the vidieo you can see the vehicle start to rise and then lower as the winch is let out a couple of times

if a snatch block had been in the system it would easilly have reared of the floor.

But i will stick to what i said if you have a vehicle winching out the back and it is holding to the piont where it starts to rear, tethering the front will cause it to bend at some piont. I used to own a scammell crusader fitted with an eight inch box subframe that bent just above the rear axle bump stop trying this method. Although i got away with a lot of times before that on various vehicles So my advise is dont do it

 

hmm we had a stuck ural on slab common, it took my stalwart, doubt you can bend her chassis, the zil 131, they are very flexible chassis and two unimogs, we lined them all up and away we pulled and out she came...cant think how we could have done that differently at the time but...we had no pulleys, the winch on the ural is about 6-7 tons, with a pulley it may have come out on her own, my stalwart was stuck in almost exactly the same place, she had bellied out, thats because I have lowered the suspension bars by about 3 inches to improve on road reliability in the tracta joints/shafts..anyway my winch is just 5 tons on a straight pull she would not budge but using a 6 ton (4 times safety) pulley she came out relatively easily...my faithe in her winch has been restored, I will be making sure stolly 1 and 2 never go out without a pulley block again thats for sure...

[cosrec]

Ok so I posted suggesting it was not a good idea to try tethering down a wrecker when winching or lifting. So I thought I had better explain why.

Here is a drawing I hope will make clearer. In the drawing at the top is a wrecker that has been designed to work to the limits of the chassis. The designer of the gear has optimised every part of the design and has worked out that it needs a 10 ton winch on the boom for lifting and a 15 ton winch mounted in the chassis for straight pulls. As with every thing the gear is designed to be built to do the job and be built to a budget. So a subframe is made to hold this gear and keep it attached to the chassis. The brackets holding the subframe to the chassis are carefully calculated to be able to hold all the stresses and feed them back into the chassis in the strongest places. I have represented these brackets with blue boxes. Notice the bracket nearest the cab is very small this is because when working at the limit of the wreckers design all it has to do is lift the weight of the cab and front end it is not carrying any of the lifting or winching forces.

So a few calculations

When lifting

Front axle weight X wheelbase divided by overhang = 5 X 12 / 6 =10 tons

When winching

Front axle weight X wheelbase divided by height winch rollers = 5 X 12 / 4 =15 tons

Weight imposed on rear axle roughly 25 tons

So it now looks like second drawing.

Designers a happy fellow he knows his gear will stand it and the chassis will be OK afterwards even though it is a funny angle

 

Then some Moron hangs on to front bumper and tries pulling it back down will post forces involved next

 

 

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Edited March 2, 2011 by cosrec

[paulob1]

tis pretty obvious when you think about it but not so obvious when you are just trying to help someone out, if the truck rears you are loading it up incorrectly. if it stays level different matter mostly..

[cosrec]

Just around the corner is a loaded 10 ton truck the driver thinks it’s a good idea to hang this on to the front bumper and pulls the rearing vehicle back down. With this truck it is quite easy because of leverage to impose what would be the equivalent of an extra 5 tons to the front axle. The front axle is now just touching the floor unless something has broken. Re do the calculations and you find the if lifting the rigging has 20 tons on it If winching the force on the rigging will be around 30 tons the weight on the rear axle will be around 45tons. The designers of the recovery gear and the chassis will both allowed a margin of overkill in their designs but I think both would agree giving this much abuse is taking the P.

If you think about you can also arrive at the above dangerous damaging situation with out realising. Same wrecker with a big winching job to do. You rig up with a snatch block hung back to wrecker and fasten loaded truck to front end of wrecker and start winching every thing sledges back then the scotches spade or legs get grip. Only thing is now you can’t tell when the vehicle starts to rear but you are applying huge overloads to the axle chassis sub frame more than enough to start snapping bolts and bending things.

So my advice is don’t do it never try tethering a wrecker down whether lifting or winching it’s your final safety valve before things start going wrong.

One last thing. Sub frames originally Holmes twin boom wreckers were fitted directly to the chassis with no sub frames and they had no problems with bending chassis except when being abused. I don’t know for sure but I don’t think the 969 DT has any sub frame fitted perhaps someone on here could verify. The twin boom by the way is the only exception I can think of fastening a wrecker down but only when doing split boom side winching.

Edited March 3, 2011 by cosrec

[cosrec]

Last time i promise i will mention it but dont tether a wrecker when winching or lifting unless you want a big repair bill or worse. Heres a picture to make you think if some wise guy tryed hanging on to this one and pulling it to the floor it would be transmitting about 110 tons through the chassis rails and into the central bogie suspension point. because of the leverage of the chassis length it wouldnt take a lot to do this.

 

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[rbrtcrowther]

I really like the yellow wrecker with what looks like a martian crane on it. Could you tell us a bit more about it mabey some more piccys in action?

[cosrec]

For sure it was a foden gun tractor chassis when bought it had 23000 miles on it. The original gun tractor body and atlas crane and bodywhere removed and a new subframe fabricated and massive rear legs made. next i fitted two extending side legs an independant underlift and refitted the atlas crane to just behind the cab. next the whole crane and winch assembly from the martian was droped on. and some fancy locker bodies made. Although we build many recovery vehicles in our workshops for our selves and customers in our workshops this old lady was my own personal project and was built in my spare time. It was supposed to go on front line duties in our fleet on police contract but Foden(Paccar) refused to up rate its GTW above 38 ton. So it was only used for assisting other vehicles on road jobs. It did do however many heavy jobs off road. we used it for 7 years and its only problem was it chewed the oilpump in the transfer box up which destroyed a couple of bearings. New bearings were easy to obtain but the pump was a problem. It was a good of road truck although it shared the same problem as the foden adopted by the british army she was top heavy. We sold here to a company from the North of Scotland and from pictures i have seen she has had a front mounted winch fitted.

These pictures show the martian which donated its recovery gear. One of the old girl before she got dressed up and makeup on

 

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[cosrec]

[ATTACH=CONFIG]42094[/ATTACH]First one the casualty was recovered sucsessfully but didnt make through the night

 

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[cosrec]

This is at looks now

 

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[rbrtcrowther]

Very nice, In fact If i win the lottery i might have to build one just like it. Great pictures too i always like to see them working. I always thought an AEC militant would benefit from a Martian crane and winch.

[CRSCRS]

Last time i promise i will mention it but dont tether a wrecker when winching or lifting unless you want a big repair bill or worse. Heres a picture to make you think if some wise guy tryed hanging on to this one and pulling it to the floor it would be transmitting about 110 tons through the chassis rails and into the central bogie suspension point. because of the leverage of the chassis length it wouldnt take a lot to do this.

 

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Cosrec, just out of interest what did you have hanging on the back of the cables ?

Cheers Chris?

[cosrec]

Cosrec, just out of interest what did you have hanging on the back of the cables ?

Cheers Chris?

 

Bit of a story behind it was digging out depth of 20ft and to eradicate Japenese Knotweed it was left in hole over night when the floods came in Doncaster. Next morning was completelly under water. I am still mystified how thet were going to get it out of hole if it hadnt floooded

 

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Edited March 4, 2011 by cosrec

[DAVEPAUL5]

Very often when using the winch on a cent arv. the exhaust pipe and silencer got white hot, s

o hot you see the gasses swirling around inside,considering you were in a small gap in a armoured turret surounded by 3 petrol tanks 2X60 gals, 1X100 gal tank with a Rolls B81 screaming its nuts off 2 ft behind you with the rope on top of the engine covered with a bit of tin so solid you could dent it by hand, you can well imagine how nice it was especially in the summer.

[cosrec]

Very often when using the winch on a cent arv. the exhaust pipe and silencer got white hot, s

o hot you see the gasses swirling around inside,considering you were in a small gap in a armoured turret surounded by 3 petrol tanks 2X60 gals, 1X100 gal tank with a Rolls B81 screaming its nuts off 2 ft behind you with the rope on top of the engine covered with a bit of tin so solid you could dent it by hand, you can well imagine how nice it was especially in the summer.

 

 

Shows how nieve i am i didnt now till i read your post and did a bit of research they had a seperate engine driving the winch. Know what you mean about the RB 81 engine the martians we had were both fit to roast you when they started to pull. You could see the exhaust glowing cherry red through the floor boards at night. When you stopped after a run they could be heard ticking and cracking as they cooled down. Cant have been pleasant living that close to one

[cosrec]

One of the best photos i have seen on this sight. I have a couple of questions to ask about the picture are both WLF the same model or is the one on the left the all power operated eg luffing and slewing i can see the one right is manual. reason i ask is the main winch on the right looks much bigger. one other question is it me or is the soldier on the extreme left an American his hat looks like American issue. Why do i think this is a good snap because i think it captures the atmosphere on a tough recovery job pefectly. The guys are grafting hard but coming to realise they arnt winning some back up has arrived and though tired they going to get the job done.

 

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[Degsy]

I doubt he is American. Looks like a British officer to me, my old man called them forage caps.

Edited March 12, 2011 by Degsy

[Big ray]

I doubt he is American. Looks like a British officer to me, my old man called them forage caps.

 

You are quite right, he `s definitely british.

[nptimber]

One of the best photos i have seen on this sight. I have a couple of questions to ask about the picture are both WLF the same model or is the one on the left the all power operated eg luffing and slewing i can see the one right is manual. reason i ask is the main winch on the right looks much bigger. one other question is it me or is the soldier on the extreme left an American his hat looks like American issue. Why do i think this is a good snap because i think it captures the atmosphere on a tough recovery job pefectly. The guys are grafting hard but coming to realise they arnt winning some back up has arrived and though tired they going to get the job done.

 

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i agree it is a good picture just noticed the scammell pioneer has lost its front left hand mudgard you can see the tyre tread

[antar]

Nobody seems in the slightest concerned about all those wire ropes under tension.

[cosrec]

I doubt he is American. Looks like a British officer to me, my old man called them forage caps.

I go with your knowledge just done a search for forage cap got this picture says american and british officers wearing forage hats. Didnt know british milatry issued with them.

 

 

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