Straps and Shackles

neilly said:

you used US tons you pillock. In your conversion if you cannot see that the trusting you understand lifting is a joke!
get a grip
cheers

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Ah yes so I did, a short rather than a long ton, how remiss ...

So are you going to answer any of the questions asked ?
Are you perhaps questioning that the defenders chassis steel has a yield strength of more than 550MPa ?
Do you think its made from a high carbon structural steel perhaps type S500J0 ?
What force do you think will pull off a tow hitch from a landy ?

miktdish said:

Ah yes so I did, a short rather than a long ton, how remiss ...

So are you going to answer any of the questions asked ?
Are you perhaps questioning that the defenders chassis steel has a yield strength of more than 550MPa ?
Do you think its made from a high carbon structural steel perhaps type S500J0 ?
What force do you think will pull off a tow hitch from a landy ?

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Depends on how rusty the chassis is, I suppose.
I have seen the entire rear crossmember of a Series, with the tow hitch attached, fly through the air during a failed snatch recovery.
Which is why I never do snatch recovery.

miktdish said:

Ah yes so I did, a short rather than a long ton, how remiss ...

So are you going to answer any of the questions asked ?
Are you perhaps questioning that the defenders chassis steel has a yield strength of more than 550MPa ?
Do you think its made from a high carbon structural steel perhaps type S500J0 ?
What force do you think will pull off a tow hitch from a landy ?

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I only asked to see your math behind your statements, But I suspect there is none.
But now you are asking me to do the work for you??

Here is a hint, so far you have misidentifed the number and sizes of the bolts required to hold a winch or towbar in place on the front of a LR defender or the rear crossmember.

Now seriously I give up discussing this with you as I am sure you will just post another YT video or another document you found on the internet.

As for being remiss on the US tons vs Imperial Tons, that is just being damn stupid, and yet you want to tell me I cannot convert from Tonnes to Tons. You are a class plonker.

Cheers

As an engineer I can not believe anyone is assuming uniformity in shear strength across defender chassis. I've had good fenders and crap ones, all straight out of the factory and no consistency between them. Some have rusted, some haven't, all used the same. I wouldn't assume anything when it comes to landrover quality control-except there wasn't any.

kermit_rr said:

I'm not clever enough for all this. I have no clue how much force of going to be involved when i stamp on the accelerator so I'm more gentle when using a skinny rope versus a big fat one

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I use the same theory when recovering tratters. Gentle take up of the strain rather than a sudden pull, means yer less likely to pull the rear cross member oft.

Hippo said:

I use the same theory when recovering tratters. Gentle take up of the strain rather than a sudden pull, means yer less likely to pull the rear cross member oft.

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Just look at the picture I posted. The 110 is at 45 degrees down a muddy slope. My rear cross member and his were fine. The forces involved were huge (and no I didn't bother to calculate!) I know that both vehicles were sound
Those that would not help a fellow LR driver stuck down a hole because they think their vehicle is not up to it are very poor examples of human kind......

My Old Landy said:

Just look at the picture I posted. The 110 is at 45 degrees down a muddy slope. My rear cross member and his were fine. The forces involved were huge (and no I didn't bother to calculate!) I know that both vehicles were sound

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The coefficient of friction is greater than 1:1 if the load is heavier to drag than to lift.
Your landy wieghs circa 2 ton.
The forces involved are (with a straight pull) less than 2 tonne. So you are right @My Old Landy not a problem at all, at all.

I'd recommend you always do a rough calculation and understand the forces involved. If you know when your towbar/x-member/winch/shackle/strop is going to fail then the chances are that it won't and you will be able to recover from any situation.

miktdish said:

I'd recommend you always do a rough calculation and understand the forces involved. If you know when your towbar/x-member/winch/shackle/strop is going to fail then the chances are that it won't and you will be able to recover from any situation.

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I saw a fellow LR driver in dire straights. He and his newly rebuilt 110 were nose deep in a muddy pit. I could have used the CB to radio for a posse of drivers to turn up and discuss the strength coefficient of British Steel pressed and welded 40 years ago. I decided instead to help the poor chap who was panicking that he had just thrown £20k into a pit in the wilds of Bedfordshire! I too am a qualified engineer with 40 years experience. That experience has shown me that my gut feeling is usually correct. I looked at the situation and responded accordingly. That is all through the very solid rear cross member and 4 x M16 bolts that hold the recovery point on. As an aside, the front recovery points on my 90 are steel tubes welded through the chassis and have 3/8 BSW high tensile bolts going through them and the 10mm thick side plates that are welded to a 12mm EN16T cross bar that is placed through holes in said plates. I seriously doubt I could generate enough force to even bend, let alone break that especially as I put a yoke between the two for front pulling

So, as a qualified engineer, you have re-engineered your recovery points significantly increasing the strength so that you "gut tells you" you can pull "huge loads".....
What you have done is provided a system that far exceeds the breaking strain of the attached strops and shackles.
Which has neatly brought us back to the original point of this thread and agrees with everything ive said.

Your gut feeling and engineering experience has provided a couple of recovery points that would be still attached to the front third of the chassis and the 30 or 40 Ton load you were trying to move with the other half of your 110 attached to the anchor.
You'd probably be sitting there looking at your engine and gearbox if your straps could take the strain and you load slid away. But your recovery points would still be good, the 10mm thick side plates and your 12mm EN16T alloy steel cross bar would be as straight as a die.

How thick is your chassis ?
2.5mm ? (I think I read somewhere that Richards use 2.5mm mild which was 25% heavier than standard).
EN16T eats mild steel for breakfast.

I look at things slightly differently and try not to apply more than 5000kgs to the anchor points on my D90 as I have calculated that my chassis will rip apart at approx twice that load.
I have a Goldfish winch rated to 11500lb (5216kg) with 11mm Dyneema rope (5896kg).
I use 5/8" rated 3.25T, green pin shackles and 3 ton (WWL) lifting slings and straps.along with a couple of 10ton recovery straps which I use to connect to anchors/wrap around trees.

I calculate what the load is so that I don't ever put more than 5000kg on a single line, strap, sling or anchor point on my Defender. I've dragged loads up to 20 ton using a series of pulleys with less than 3 ton on my winch.
None of that is a 'gut feeling' it's calculated (back of a fag packet but still calculated) .....

Most people aren't qualified engineers of 40 years experiemce and don't have access to welding and fabricating equipment or exotic alloy steel. I get the impression that the OP falls into that category as he was confused by shackles having a lower rating than straps. Hopefully those questions have been answered and he realises that he doesn't need anything special to pull up to 5000kg which is the equivalent of hauling 2 landrovers up the face of a cliff.

miktdish said:

Your gut feeling and engineering experience has provided a couple of recovery points that would be still attached to the front third of the chassis and the 30 or 40 Ton load you were trying to move with the other half of your 110 attached to the anchor.
You'd probably be sitting there looking at your engine and gearbox if your straps could take the strain and you load slid away. But your recovery points would still be good, the 10mm thick side plates and your 12mm EN16T alloy steel cross bar would be as straight as a die.

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What absolute rubbish. The frame will not tear in half before the shackle gives way. You always give anything like that a failure mode to protect the major component.

With regard to straps, one has to be careful on how the straps described, what the intended purpose is, what material they have been made from.

SWL is an outdated expression meaning safe working load and is no longer used

WLL means working load limit. For lifting straps there is a 7:1 safety factor so a strap with a WLL will have a breaking strength of 14 tonnes when NEW.

Steel shackles will typically have a safety factor of 5 or 6 to 1 over the WLL

Towing normally means applying steady load whereas recovery can involve shock loads.
Tow straps sold by the car shops are often rated by weight of the car they can tow on tarmac road and is not a WLL or break strength.

Most tow straps/lifting straps are made from polyesters such they have low extensions. That means high peak loads when used in a shock loading situation

Recovery straps are made from nylon and has much higher extension to break than polyester which means lower peak forces in shock loading situations. Recovery straps do not have a WLL.


Brendan

Hi @neilly

Hope they’ve checked the bolts before hand, lol

must admit very impressive of how much stronger the chassis’s have become, plus surprising how many don’t check there towing / recovery strops for their age

My Old Landy said:

What absolute rubbish. The frame will not tear in half before the shackle gives way. You always give anything like that a failure mode to protect the major component.

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So let me say that again as I think you missed what I was saying ....

You have (using your gut feeling) engineered "front recovery points on your 90 using steel tubes welded through the chassis that have 3/8 BSW high tensile bolts going through them and 10mm thick side plates that are welded to a 12mm EN16T cross bar that is placed through holes in said plates with a yoke between the two for front pulling" ... on a standard 2.5mm mild steel box section chassis.

So these plates, tubes and the cross bar are where exactly ?
Above the dumbirons in front of the forward cross-member between the forward chassis legs or between the dumbirons, effectively bracing them together below the chassis ?

Stengthening that area surely exposes the area behind the forward x-brace (where the 4 holes are before the front spring retainers and shock turrets) as being the next weak point ?
Or do your additional 10mm plates extend past then towards the engine mounts where the chassis offers a taller profile section.just in front of the gearbox x-member ?

You are right in saying that the chassis (even the standard chassis as in the pic) shouldn't give way before the shackles break (ie they are the weak point) but what shackles are you using ?
Earlier you said you used 5/8" 3.25T WWL shackles. These are rated with a 5 (or 6):1 safety factor. 5:1 = 16 tonne.
You also said you used 6 and 10 tonne 'towing' straps.

Why have you added all of this additional strengthening again ?
My point is that all this strengthening you have added will hold fast but the chassis 'will' tear in half as it is weaker ....

miktdish said:

So let me say that again as I think you missed what I was saying ....

You have (using your gut feeling) engineered "front recovery points on your 90 using steel tubes welded through the chassis that have 3/8 BSW high tensile bolts going through them and 10mm thick side plates that are welded to a 12mm EN16T cross bar that is placed through holes in said plates with a yoke between the two for front pulling" ... on a standard 2.5mm mild steel box section chassis.

So these plates, tubes and the cross bar are where exactly ?
Above the dumbirons in front of the forward cross-member between the forward chassis legs or between the dumbirons, effectively bracing them together below the chassis ?

Stengthening that area surely exposes the area behind the forward x-brace (where the 4 holes are before the front spring retainers and shock turrets) as being the next weak point ?
Or do your additional 10mm plates extend past then towards the engine mounts where the chassis offers a taller profile section.just in front of the gearbox x-member ?

You are right in saying that the chassis (even the standard chassis as in the pic) shouldn't give way before the shackles break (ie they are the weak point) but what shackles are you using ?
Earlier you said you used 5/8" 3.25T WWL shackles. These are rated with a 5 (or 6):1 safety factor. 5:1 = 16 tonne.
You also said you used 6 and 10 tonne 'towing' straps.

Why have you added all of this additional strengthening again ?
My point is that all this strengthening you have added will hold fast but the chassis 'will' tear in half as it is weaker ....



View attachment 239537

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That pic is pure undressed porn.

No idea what else you lot are talking about.

J

miktdish said:

So let me say that again as I think you missed what I was saying ....

You have (using your gut feeling) engineered "front recovery points on your 90 using steel tubes welded through the chassis that have 3/8 BSW high tensile bolts going through them and 10mm thick side plates that are welded to a 12mm EN16T cross bar that is placed through holes in said plates with a yoke between the two for front pulling" ... on a standard 2.5mm mild steel box section chassis.

So these plates, tubes and the cross bar are where exactly ?
Above the dumbirons in front of the forward cross-member between the forward chassis legs or between the dumbirons, effectively bracing them together below the chassis ?

Stengthening that area surely exposes the area behind the forward x-brace (where the 4 holes are before the front spring retainers and shock turrets) as being the next weak point ?
Or do your additional 10mm plates extend past then towards the engine mounts where the chassis offers a taller profile section.just in front of the gearbox x-member ?

You are right in saying that the chassis (even the standard chassis as in the pic) shouldn't give way before the shackles break (ie they are the weak point) but what shackles are you using ?
Earlier you said you used 5/8" 3.25T WWL shackles. These are rated with a 5 (or 6):1 safety factor. 5:1 = 16 tonne.
You also said you used 6 and 10 tonne 'towing' straps.

Why have you added all of this additional strengthening again ?
My point is that all this strengthening you have added will hold fast but the chassis 'will' tear in half as it is weaker ....



View attachment 239537

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I do not misunderstand anything you are saying. I am using the jate ring points and have made my own to fit through those points. They are already strengthened. The strap or shackle will break first. The chassis is constructed so it is not a simple shear path. There are tubes side to side along it that transfer the loading throughout. You are taking a simple metal shear strength and trying to imply that it will just shear. You seem to have no understanding of metallurgy or design and construction for maximised strength.

I'm sure there was something years ago about suspending a mini from a single strand of nylon

kermit_rr said:

I'm sure there was something years ago about suspending a mini from a single strand of nylon

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I once watched a Land Rover being lifted on one inch of weld on a mild steel hook! Without a shock load, many things seem to go far past their theoretical limits

marjon said:

That pic is pure undressed porn.

No idea what else you lot are talking about.

J

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Choices, choices!
More popcorn or get up at dawn to witness the handbags flying?

Still trying to find the SWL of the tree I’m going to use as an anchor

any ideas.?

Hicap phill said:

Still trying to find the SWL of the tree I’m going to use as an anchor

any ideas.?

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Exactly lol