Straps and Shackles

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I do like a good think while I’m driving...
Iv now found a large tree
How can the stitching on my tree strop be better than metal bolts holding my winch on?
Also the winch carrier has horizontal bolts do the calculations change for shear?
(As these go through the LR jacking points they are not tubed but the metal is thicker?
 
Hicap phill said:
I do like a good think while I’m driving...
Iv now found a large tree
How can the stitching on my tree strop be better than metal bolts holding my winch on?
Also the winch carrier has horizontal bolts do the calculations change for shear?
(As these go through the LR jacking points they are not tubed but the metal is thicker?
Click to expand...
What you need to do is weld a huge lump of steel to the front............. It worked for me!
 
My Old Landy said:
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.
Click to expand...

Ah, you have jate rings on the front ... "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" ...

You have strengthened these holes ?

normal_IMG_6000.JPG

...
These are in the dumbirons which have a gusset plate on the inside (sorry can't find a better picture)... which offers some tortional stablity
https://www.ebay.co.uk/itm/124568081465?hash=item1d00d61439:g:GysAAOSw~ZVgJBid

Found a better picture of some 'home made, uprated' ones... these are much thicker than the originals which are designed to be welded into the bottoms of the chassis legs. As you can see there is a small section of angle over where the kate ring would mount.

s-l1600.jpg


So you have 'engineered' these mount points to be stronger than a 3.25T WWL shackle ?
Can we see a picture ?

Just out of interest how are you generating such mahoosive loads that you have designed you car to take ?
Are you anchoring your D90 at the rear ?
 
miktdish said:
Ah, you have jate rings on the front ... "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" ...

So you have 'engineered' these mount points to be stronger than a 3.25T WWL shackle ?
Can we see a picture ?

Just out of interest how are you generating such mahoosive loads that you have designed you car to take ?
Are you anchoring your D90 at the rear ?
Click to expand...

I point you at these posts I already made.
My Old Landy said:
I have the 3.25t rated shackles. They fit nicely in the jate rings on a Defender. I use both 7t and 10t straps (ensure they are for pulling not lifting as it is a different load. Only buy properly rated gear and not something that says it is.
Click to expand...

My Old Landy said:
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 :)
Click to expand...

You seem to be digging for something. Neil has been at this recovery game for a long time and I have been in engineering my whole career (now retired at 55) and it seems that there are a few 'internet kings' that would have you believe because they shout the loudest they actually know something. I think we are done now, it has run its course. Enjoy your time off road and if you can, help someone who has come a cropper. You vehicle was designed to take a squaddie through the rigours of war and harsh, extreme climates. Pulling someone out of a ditch is not an onerous task.
 
miktdish said:
It wouldn't, that pull was less than 2500kgs .....
Click to expand...
No it wasn't, you seem to forget the momentary forces at work with a snatch. The vehicle was in mud down a 45 degree slope with no traction. I was, in effect, pulling it into the slope before he popped out. I could not gain enough traction to pull without a snatch.
 
Hippo said:
I will ask edgar but need to know the soil type its planted in, tree type and age.
Click to expand...
And if it was planted in a round or a square hole!
Never believed it was important until quite a large eucalyptus tree we had planted went over. It was obvious from how the roots had just gone round and round that it had not been planted in a square hole.
Whoda thort it?
(Twas on one of them scientific progs, or was it QI?):):):)
 
Found this thread really interesting , thanks so much for sharing , even like many of us who have done off roading for many years I still like to learn new things

must admit many moons ago when I had my series 3 I had a drop plate and was about to recover another landy using my tow ball that had got stuck in the mud , guy came over and told me that I should never ever use a tow ball for snatching or recovery , alas I was only in my 20’s then and to this day never done it

after the introduction of utube and watching many videos can really see why , plus am re reading the threads with regards to how a chassis can snap , must admit only ever seen rusted bits pulled off but think I’m reading it wrong

thks again

 
My Old Landy said:
<snip>
You seem to be digging for something.
Click to expand...

Yes information and qualification of your (and Neils) points.

You've explained what you physically did to your forward recovery points. I sought clarification, a 'why I did it' and possibly a picture.
You (in your last post) described your recovey as a snatch and suggested as you have in other posts that I don't know what I am doing - untrustworthy, obvoisly hasn't any real life experience, pillock etc etc.
You said that I "seem to forget the momentary forces at work with a snatch", well ... that's the first time you said it was a snatch and, yes I do recognise that the kinetic energy release of a snatch pull is significantly high, however, I don't use that technique as I don't think i'm able to reliably calculate the forces involved. I have a winch so don't need to 'snatch' anything.

I understand that the chassis is made from mild steel plate with a yield strength of 550MPa - I asked what you and your recovery mate thought/if you agreed and never got a response.
I asked what the pull off force would be for the rear tow hitch - no answer - 1 reckon it's circa 5000kgs BTW
I have reasoned that the chassis will deform at around 9000kgs and said that: I (fag packet) calculate the max load I put on my D90's chassis to never exceed 5000kgs.

No responses whatsoever other than you guys are so good you don't need to qualify anything. It's all in yoiur gut feelings.
I can't work on gut feelings, I need facts, if I design something and it fails folk may die so it has to be right.

There are likely a lot of people reading this that would be intersted in facts to.
Shouldn't these people (me included) be allowed to gain something from your experience and enginering skills ?
Why did you beef up your recovery points ?
What load will they now take ?
Have you ever exceeded a 9 ton load with your vehicle ?

Here is a very interesting artice that discusses many aspects of this thread - including @Hippo 's question about what type of tree (who even knew that was a thing ....)
It's even got some math in it, just for @neilly
https://www.4wdingaustralia.com/4x4/4wd-recoveries-guide-to-forces-and-sizing-recovery-gear/
 
miktdish said:
, I need facts, if I design something and it fails folk may die so it has to be right.
Click to expand...
@miktdish ,But you have not provided the facts and figures, only stuff that you seem to have grabbed out of the air and as you are not capable of understanding where you could not even define the difference between US and imperial tons , oh how remiss of you. Why should any of us believe your made up figures ( sorry , I meant fag packet calculations).

BTW , it was me that called you a Pillock not My Old Landy.

You will note I asked for your workings and you posted some article whihc you said was a reasonable facsimile, afte that you seemed to take offence .Rather than showing how you had calclulated it out. If you are so good at the fagpacket sums, then please show them. Or do you google an intersting article or youtube video eveytime you get stuck?

You are still a plonker.

Cheers
 
gstuart said:
Found this thread really interesting , thanks so much for sharing , even like many of us who have done off roading for many years I still like to learn new things

must admit many moons ago when I had my series 3 I had a drop plate and was about to recover another landy using my tow ball that had got stuck in the mud , guy came over and told me that I should never ever use a tow ball for snatching or recovery , alas I was only in my 20’s then and to this day never done it

after the introduction of utube and watching many videos can really see why , plus am re reading the threads with regards to how a chassis can snap , must admit only ever seen rusted bits pulled off but think I’m reading it wrong

thks again

Click to expand...


sorry G but I lost interest after he tried to tow that tree out:confused::confused::confused: your gonna break stuff trying that ****, no ****:eek::D:D.
He needs to buy a chainsaw:D:D.

J
 
its all about being sensible though o_O if you're going to do a snatch.. dont use a skimpy rope and a 20 yard run. of course, recovery points were checked during scrutineering, werent they?
if someone's been stupid enough to get stupidly stuck, say, up to the windscreen in sticky mud... a snatch isn't the right tool for the job.
you should plan for ropes/chains/wires breaking because it happens
 
kermit_rr said:
its all about being sensible though o_O if you're going to do a snatch.. dont use a skimpy rope and a 20 yard run. of course, recovery points were checked during scrutineering, werent they?
if someone's been stupid enough to get stupidly stuck, say, up to the windscreen in sticky mud... a snatch isn't the right tool for the job.
you should plan for ropes/chains/wires breaking because it happens
Click to expand...

Indeed and how many times have we seen that where someone has thought there 4x4 will drive through anything

must admit have seen some failed snatches using a kinetic rope but success with a very slow recovery using some ratchet straps , as u rightly say all about using a sensible solution including planning ahead as far as possible with the what IF’s of what could go wrong

must admit have got myself well and truly stuck in the past but learnt from , including never going off road on ur own

plus am I right in saying , ur using the same force on both a kinetic and strop , just the kinetic rope gradually increase’s the force over a longer period and therefore reduces the shock load

saw this pic the other day , looks like he’s using the tow ball

BDAB5039-A715-4B39-A4FC-BAD939757485.jpeg
 
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