cosrec

The lifting straps are wrapped around the drum and anchored to the chassis suspension pionts. This also holds the drum on to the rear cradle of the mixer as it is only held on by gravity

A third way of doing a roll over is a combination of lifting and straight winching and I would think it’s the method we use the most. Why because for reasons known only to rolled over vehicles they usually pick places to roll where access to topside is awkward. I haven’t put any calculations on but the lifting rope is taking more strain than when straight lifting but a lot less than when straight pulling. I have put some pictures on that show this method. Notice the boom is well elevated. The second winch is not doing any pulling as such only twisting axles down to get them to bite. Such is the nature of our roads straight on alignment to vehicles is often impossible so vehicle has to be parked at an angle hence two vehicles used as casualty would turn one over. Th[ATTACH=CONFIG]37104[/ATTACH]is vehicle had to be winched literally to ground level and only stabilised its self when ropes were slackened of allowing the drum to rotate s[ATTACH=CONFIG]37103[/ATTACH]lowly back to bottom total weight of mixer 32 ton Also the vehicle was initially laid over centre which increases force needed considerably

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What a bummer :embarrassed:

Once the vehicle has gone past the point of balance it goes in to freefall back onto the ground. Lets bust a myth here you hear people say “when a vehicle is winched over it can hit the floor then topple the other way”. With two exceptions when winching on to level surface there is no chance of this happening. The exceptions are fridges with swinging meat and half loaded tankers. Having said that just because it hits the floor and does not roll again does not mean it’s a good recovery. To me nothing looks worse than a vehicle hitting the deck with say front axle followed a fraction of a second later by the remaining axles. It is these multiple shocks in close succession that cause the damage eg floor boards to spring out lights and lenses mirrors falling of and on occasion’s bodies to split and collapse. If when you rig up you spend time and are aligned with the CG as you winch it over all the axles will hit the floor at the same time and the suspension will absorb the shock as it is designed to do. It wont look dramatic on a video but there again any controlled well carried out recovery wont.

If you where to film the two examples that I have used the MT and laden vehicle the MT one would probably look the most dramatic with dust and muck flying about as it hit the floor. Why because the laden truck would almost certainly be have to be winched until it almost hit the deck because the steel plate is offset to the side. Secretly I would be hoping for a bit of a rough landing so that it fell back over saving me sorting it out before towing away.

If you have any doubts and have no means of doing a controlled restraint a couple of old pallets under a couple of high side wheels will smooth things out a bit.

I have also used MT 25 litre drums with bungs in stood upside down under where wheels are going to land or even a couple of tyres on top of one another.

Another day same truck same load same driver and Guess what it’s rolled over again. I am beginning to have doubts about this driver.

How’s about this time trying a different approach. There is access to high side of vehicle. What will it take to lift vehicle over. Calculation is same as before but remember distance from fulcrum to where winch is hung is height of vehicle Therefore 160 x 8 / 12 = approx 10.8 tons, will be needed to raise vehicle.

Must point out a couple of things

Here this it true lifting and as such you are in the lifting regulation requirements and all that entails. In order for it to be a good recovery the actual lift needs to be inline with the CG. So if you only have one lifting line some form of bridal is required. This brings about a problem if you use the top lifting eyes of container to hang to the bridal will be at a great height before you actually start to lift container and with a lot of recovery vehicles you will run short of actual available hook height to get vehicle to point of balance.

To overcome this we sometimes lift initially at back corner until about 4ft off the floor and then put cribbing in place to hold in that position this is why you need those back doors in place for strength. Then if need be move to front top corner of container and do the same there. What has this achieved? It now means the bridal can be arranged by fastening to the chassis or bottom of container with the point the hook is hung to is closer to the floor giving more chance of getting it to the point of balance before losing all hook height. It also means the wheels are now firmly planted on the floor and bearing weight. In all probability the total force now required will be a lot less then first calculated giving more chance of a good outcome. All with out lifting more than about 5 tons Hope drawing makes clearer.

So go for it and up it comes.

May have noticed in my posts I have hinted a couple of times about a good recovery. What I mean by this is the vehicle ends up stood upright with no further damage.

If you think about it once the vehicle has gone past the point of balance in the examples I have given the vehicle is out of control and is totally in the hands of the CG pulling back it down to level ground.

What if the toppled truck above is a curtain sider? Surely you have to unload the goods then and through the top side curtain? Or do you take a view on the nature of the load and whether or not the curtain will support it during the lift?

Good question and i will try and answer but would like to post a little on more on roll over theory first. Suffice to say i have loathing to unload any vehicle if there is any chance of standing it up with out damaging further.

Same truck and driver but this time it has 6 ton of flat plate strapped down in the back of it. Guess what it’s flipped over again. In side the container two things could have occurred. Either the plate is still strapped flat to floor or it has broken loose and is laid flat in the side of container. What next well one thing you don’t do is open back doors to have a look. Why because all though the vehicle is laid on a level road it may have camber on it or be resting with a corner on a kerb. If you open the rear barn doors the container will distort you will be very lucky to get them to close again. With out these doors closed and locked correctly the whole integrity of the box has gone. This is even more important when dealing with Box vans Fridges even Tilts. The ends of the box are the only strong points you have to hang on to or wrap round

It is also very dangerous if you open them as you could soon end up will a couple of tons of goods on top of you.

So in the drawing I have assumed the plate has fallen over. This now puts the CG up around 8ft from the Fulcrum It also means the CG is offset to the side but that has no effect on the recovery at this stage we are only interested in where The CG is pinning it to floor. The CG when looked at from underneath has also moved near to rear of vehicle.

When the vehicle was MT the force required to pull it over was approx 7.7 tons Now if using axles force required will be 16 X 8 / 6.5 approx 20 tons 10 tons per axle. The axles will stand this but as I have said before it’s always wise to reduce strain on rigging. So I have shown a way of achieving this with the use of three sleepers. The rigging (bridal) are fastened to the top lifting eyes a job they are more than equal to. The force required is now 18 X 8 / 9 14.5 approx tons. It takes a little effort to adjust legs of bridal to right length so that all three axles touch floor together when starting recovery but let go and re rig it will pay of later in recovery. I think this example also what a small difference in weight can make. It makes you aware what forces are involved when moving up to loaded 44 ton artics say

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In haste trying to get boring bits out of way i forgot one very import thing. First thing to check on any roll over is are the brakes on. If the vehicle moves as it comes over the sidewalls of the tyres lose grip and it will crash back to the floor again. In extreme circumstances it can move that far it will tip the recovery vehicle over. Very good vidieo on Utube showing this happening.

Another little fact dont rely on transmission brake to hold vehicle they dont hold anything when set of wheels are off the floor If need be some good timbers back and front of tyres will do the job. Even on level ground you can be inadvertantly be making the vehicle tend to roll back or forth by not being exactly lined up with CG

During the initial part of the recovery it takes very little to dislodge grip on tyres. And i have had an occasion when the draught suction from a passing fridge lorry dropped one back down.

So pull as much as you want it will only sledge towards the winch force when rigged as per example. Until you get the wheels to touch the floor with weight on then bite you will do no good

What can be done to alter this? The first thing I would do is move the height I was winching from a good point would be out board of the front spring. This point will mean the winch rope from your vehicle will be going uphill. This has the effect of pulling and twisting the axle downwards on to the floor and causing it to bite in. It also has another good effect if you do the sums again the amount you have to winch has come down.

E.g. originally it was 12.5 ton now its 10x5/6.5= approx 7.7 tons a big difference just for moving winch rope. Every thing you can do to reduce strain on rigging is good and becomes even more so as you move on to heavier vehicles and can make all the difference between success of failure.

Ok checked all rigging again and have another go.

Vehicle cab comes up a little way chassis twists a bit then bang the whole lot crashes back to floor and your back to where you started.

What’s gone wrong? Its back to CG again for sure we guessed where it was looking from the front but ignored looking from the underneath. Again it’s a question of guessing where the CG is. On this next drawing I have made a guess where I think it is taking into account heavy bits engine box etc at front balanced by empty light container at back. Its clearer now the last attempt was a no boner from the start as hung only to front axle it was going to swivel around the point were CG was pinning it to floor. The ideal place to hang to would be straight in line with the CG. Alas the only place you can hang to anywhere around here is the chassis rail but it’s cluttered with fuel tanks or air tanks. The recovery truck only has one winch so the only option is to use some sort of bridal to attach equidistance from the CG in this example I think front axle and second axle would do the trick. As a little bonus this means the load taken by the axles is only half of 7.7 tons so after a few attempts try again and up she comes

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With respect to braking systems and the requirement for two seperate braking systems I recently had a new Passat as a courtesy car and as far as I could tell it only had one effective braking system, the middle pedal. Its hand brake was a button on the dashboard. It also automatically applied and realeased the handbrake automatically when you stopped for a certain amount of time. Do these actually comply with C&U? Give me a mechanical one anyday at least I can control that (and execute handbrake turns).

 

 

Mike

Ok vehicle design has moved on a bit from our last vehicle (brick). This one is a 6*6 flat carrying a 20ft container vehicle with a weight of 10tons. It has conventional road springs on it. For what ever reason it has fallen over on a flat road.

The first that springs to mind it to winch it over but we need know to if we have enough winch capacity. If we liken it to a simple bell crank lever the calculation is simple.

First we need a fulcrum this is the outside edge of the tyre where it hits the floor and pivots

Next we need to know where the CG is. One thing for certain it will be as near as dam it to the centre line of the vehicle when viewed from back or front in an upright position.

Its unladen so all the heavy bits e.g. axles engine chassis are near the bottom with lightweight bits high up. There is no exact way in recovery to say its here or there so a good guess is going to be the best we can do.

A general rule of thumb that has worked for me is a little bit above the height of the tyres. This has proved good for cars and all unladen flat bodied and lightly built box vans. On this vehicle I would guess the CG is around the 5ft mark

So we CG (10) times distance from CG to Fulcrum (5) divided by distance from Fulcrum to where we hang the winch (I have chosen mid way up vehicle for this example) (4)

So in theory a fraction over 10x5/4= 12.5 tonnes will see the vehicle stand up. In practice it won’t will explain in later post.

[ATTACH=CONFIG]36521[/ATTACH]

So why wont the vehicle stand up. There are two reasons. The first and I have deliberately stressed this.

Because a vehicle falling over on a level road don’t actually end up with its wheels touching floor. Or at least will have no weight on them

So pull as much as you want it will only sledge towards the winch force when rigged as per example. Until you get the wheels to touch the floor with weight on then bite you will do no good

In order to recover an overturned vehicle a bit of theory is required. You can go about it with the yank it over approach and get away with it’ but if its your pride and joy you not going be over happy if crashes to the deck and its got more damage then when it fell over.

I think it is important to understand why it fell over. May seem a bit basic but if you know why it fell over it is the same as a lot of things in recovery you can work it back the other way and use it to advantage.

So why did it fall over you could say going to fast or terrain or wind or maybe impact damage but basically it’s down to CG.

CG stands for Centre of Gravity.

In normal circumstance the CG is pulling a motor vehicle stood on level ground straight down with a force equal to the vehicles weight. The vehicle is stabilizing this force by spreading it through its wheels or tracks. All the time the CG is acting between outer edges of the wheels or tracks the vehicle will stand upright

If the CG is acting straight down through outside of one side wheels or tracks the vehicle is on the point of balance

If it’s laid flat on its side the vehicle is being pinned to the floor with a force equal to vehicles gross wt straight down through CG

Great so we know the CG is giving us problems but where is it.

To try and show more clearly I have put a simple picture on of a vehicle that looks very much like a brick stood on its thin side viewed from one end. This vehicle (brick) is of uniform construction and density through its length height and width therefore its CG will be at the centre of the vehicle (brick) from which what ever way it’s looked at. Sorry if this sounds boring bear with me next post will be more interesting

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Standard on Military Land Rovers mate, older MV's like Bedfords etc it's always best to form an apex using strops or chains reeved around the spring hangers, very strong. Quite a few vehicles have recovery eyes (Defence Standard) which are connected/welded to the chassis, these are obvious recovery attachment points and are extremely strong.

 

We are never taught to go around axles as most MV's have driven front axles and the casings (which the half shafts go through) could easily deform, and cause irrepairable damage. Army recovery mechanics employ some different techniques to civilian recovery operators due to the nature of the vehicles, however most recovery techniques can be used for both civilian and military. We could learn a lot about roadside recovery from the civilian operators, especially side over sides, or rollovers in civi speak..

As you quite rightly state recovery techniques vary between army and civilian life i think this is more to do with eqipment used then any thing else. Army eqipment is designed for straight forward lifting or straight winching out the back for the most part. Civilian eqipment is designed on a much more budget design but can do elevated winching with a twin winch system. But in general all recovery jobs are the same the whole world over. A successful out come will usually end with some compromise somewhere and be dependant on the knowledge of the operator. Will try and put some posts on for side over sides

Have read comments on MoD vehicles re recovery pionts. So its a case of using what you trust. The bulk of vehicles we attend are not fitted with any recovery pionts. As i mentioned in another post i have no problems using manufacturer fitted trailer hitch pionts but in the absense of these we advise all our drivers to hang on to axles on bogged upright winching. We dont even use tow bar hitches on cars anymore except for mild pulls having had these rip out of bootfloor when pulling out of dykes etc. Like Recymech66 pionted out there are differences between Mod and civillian ways of doing things but it is worth bearing in mind if your friend asks if you for a pull out of some mud say with his private car dont be tempted to use those flimsy lashing pionts or that stupid screw in eye that comes with them. You will probably be lucky and get away with it or it could cost you some apologies and money.

By the way if you decide to go along the route of using the J hook bridal i posted earlier they are always fitted upside down eg hung on from underneath.

I believe there was a long and short wheel base of the amazon chassis but cant be sure. As for whats on roof i think thats wreckage in back ground. As for windows would suggest sun reflecting maybe . Also i think there are four more people to right peering into wreckage to right of obvious person also another stood on crane operating controls

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Above is similar although not identical to what we use for recovery on all vehicles under 3.5 tons wether for pulling up slide bed or winching out. We place out board of spring mounts on conventional axles and as near to suspension/body mounts on all other vehicles.

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Hi i have some questions to ask not having any milatry background .

Before replying to any questions i looked at a lot of pictures on this site looking at different towing eyes.

This picture posed a few problems to me the lower nato type hitch looks like an after thought i wouldnt have thought the manufactuers would have compromised its hill climbing ability by sticking this here ???

Lower down are two more rings with shackles attached these look like lashing eyes to me .???

Higher up is another towing eye this dont look like its standard to me ??

Either side of this towing eye are two welded on lugs is this were you are supposed to hang to ???

One more nothing to do with recovery what colour is it sprayed ?? i think it it will be ideal for my leyland drop project it looks much yellower than usual or is it the light

Hmmm that isn't right either - the middle one is labelled right as you have shown it being pulled by spring hangers. But the lower one I still think should be same as middle, as forces must still be transmitted through hangers? :nut:

When you pull directly on axle you over come all forces that axle is causing then you only worry about the forces the next axle is causing in this case 1500kg

what i tried to piont out with drawing is as long as the axle can handle the strain you are imposing no more on mounting pionts than you would if using towing eyes certainly less than just using front hangers. Only difference in forces between two is direction

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Bit complicated but above is my take on stresses in different parts of system when winching a bogged down LR have guessed wieght at 3000kg and pull required to move it at same. Where figures say *2 i am assuming loads are being shared either side of chassis.

Suprising how same load in causes different stresses in diffent places.

Agreed - imagine dragging a bogged FH70 by the axles :nut: Snap!

using the axles is not a good idea!

 

once down on the slab, some know it all serge (names withheld to protect the innocent) got the landie bogged in, so he promptly started to recover it from the axles, he was told that's not a good idea, by me and some others, (but as i was only a lance jack at the time,and the others private's) we were told to shut up, "im a sergent"

so he continued, the rover bogged in and then the funny noises started to be heard until, "bang" one bent and damaged axle!

it gave way on one side and pulled it off! :blush: lesson learnt, and one red faced sergent with a slightly lighter wallet!

strong chassis fixings are the only point!

Something dont ring true with this will put a post on to say about stong fixing pionts but would suggest it was rigged to one side or something was snagged somewhere sure it was fastened to axle not just say one spring hanger

These jate rings standard on MOD vehicles

using the axles is not a good idea!

 

once down on the slab, some know it all serge (names withheld to protect the innocent) got the landie bogged in, so he promptly started to recover it from the axles, he was told that's not a good idea, by me and some others, (but as i was only a lance jack at the time,and the others private's) we were told to shut up, "im a sergent"

so he continued, the rover bogged in and then the funny noises started to be heard until, "bang" one bent and damaged axle!

it gave way on one side and pulled it off! :blush: lesson learnt, and one red faced sergent with a slightly lighter wallet!

strong chassis fixings are the only point!

Curious you want piont these out for me plus how you fasten to them. I work mainly on civvy landrovers so perhaps there is some strong pionts i dont know about on MOD landrovers

I had bum twitching just watching it