Thread: Rear recovery hook

Originally Posted by cucinadio

ok ...what about if you use a shackel attached to the tow hitch the the hole with out the tow ball in ?......

cheers

That's fine if the towbar is strong enough. Some aren't.

Originally Posted by Dougal

That's fine if the towbar is strong enough. Some aren't.

well mate if its strong enough to pull a car trailer loaded with a S3 ...l don't think it will be a prob......

this is very interesting subject and its interesting to get a lot of differencing views...

cheers

Originally Posted by cucinadio

well mate if its strong enough to pull a car trailer loaded with a S3 ...l don't think it will be a prob......

this is very interesting subject and its interesting to get a lot of differencing views...

cheers

No, seriously it's not.

The average snatch strap has a breaking strain of around 8 ton. If your towbar (including chassis attachments) can't take a significant amount more than that, then it shouldn't be used.

Even a towbar rated to tow 3.5 ton may not be strong enough to snatch from.

Originally Posted by Dougal

No, seriously it's not.

The average snatch strap has a breaking strain of around 8 ton. If your towbar (including chassis attachments) can't take a significant amount more than that, then it shouldn't be used.

Even a towbar rated to tow 3.5 ton may not be strong enough to snatch from.

like i said it all makes for interesting reading ...but show me on research that has a hook with two bolts through the chassis rail ...is stronger than a tow bar attached at three point of the chassis rail's ?..

cheers

What's wrong with a 4.5T recovery hook? far more useful than tits on a bull.

If you're worried about the pin, take the towball off and put a rated shackle through the hole.

Originally Posted by Dougal

Do the maths.
Perception is often at odds with reality. Here're some FEA plots to prove it.

the problem with your theory is that the strap will not be a point load on the pin due to the thickness of the strap, it will be distributed along the pin, all be it not uniform.

If this was not the case then the strap would fail as it would not be strong enough to provide a point load.

1: isnt the breaking strain of a snatch strap a moot point if the more dangerous part, the shackles used to attach the snatch strap have a SWL of 4.5 tonnes? (breaking strain of?)



bit of a **** i know, but i figure i'm gonna end up in the weeds eventually.........

Originally Posted by black betty

the problem with your theory is that the strap will not be a point load on the pin due to the thickness of the strap, it will be distributed along the pin, all be it not uniform.

If this was not the case then the strap would fail as it would not be strong enough to provide a point load.

That's been discussed already.
Even ff you had a strop as wide as the pin, (i.e. UDL), the bending stress still reaches 750MPa for a 5 ton pull. Well beyond what you'd call safe and still 1.5 times higher stress than the towball which we all know is unsafe.

Originally Posted by cucinadio

like i said it all makes for interesting reading ...but show me on research that has a hook with two bolts through the chassis rail ...is stronger than a tow bar attached at three point of the chassis rail's ?..

cheers

Give me photos and measurements of your tow bar, I'll tell you (within reasonable limits) how strong it is. Landrover bars are stronger than most due to the centre rear mount, a lot of japanese vehicle towbars have to span between chassis rails unsupported.
Most towbars are let down on attachment points. Most 4500kg rated hooks are also let down on attachment points and the hooks themselves yeild before their rated capacity anyway.

IMO decent plate eyes are the best recovery points. Far supassing the strength of 4500kg hooks and offering more (& better) attachment options.

Sprint, SWL is safe working load, they'll start to yield (bend/stretch) if you exceed that but it takes a lot more to actually break a shackle.