Towbar as a recovery point....again

Submitted: Friday, Jun 04, 2004 at 23:17
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Earlier today on post 13,447 the subject of recovery points was raised.
Nobody mentioned anything about the idea of using the box hitch towbar, but leaving the normal box section in place.......but unbolt the towball (or in my case the TREG fitting). You could then simply place the rated shackle's pin through the hole where the threaded towball usually goes.
The possible downside of this would be that you'd be adding another potential "weak point" (being the weld of the right angle goose-neck) into the equation, but I would reckon that should be as strong as these newish specialised recovery-specific box-section gizzmos they sell with captive hooks or lugs to accept the shackle etc.
Any thoughts?
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Reply By: Truckster (Vic) - Friday, Jun 04, 2004 at 23:19

Friday, Jun 04, 2004 at 23:19
I'd rather take the tounge out, would make a Pi$$er missile.. just use the pin on the Hayman Reece as usually do...
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Follow Up By: Leroy - Friday, Jun 04, 2004 at 23:30

Friday, Jun 04, 2004 at 23:30
Ditto.

Leroy
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Follow Up By: Member - Roachie- Friday, Jun 04, 2004 at 23:30

Friday, Jun 04, 2004 at 23:30
Trucky,
That's what I've always done in the past anyway, just that a few blokes have talked about the snatch strap bending the pin....never had this happen to me or anyone I know, so probably isn't a real drama. I always carry a spare anyway, so if it did get bent the worst part would be the sheetload of time it would take to hacksaw through the bent one!!!!
Catchya
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Follow Up By: Truckster (Vic) - Friday, Jun 04, 2004 at 23:39

Friday, Jun 04, 2004 at 23:39
With 40+ recoveries, and some with heaps of left foot, Ive never bent 1.. But I do have 4 of the pins in the toolbox, so just grab the first oen I see
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Follow Up By: Bonz (Vic) - Friday, Jun 04, 2004 at 23:45

Friday, Jun 04, 2004 at 23:45
Same as what I do T-Man, same thing not as many recoveries but no bending and one or two had to pull very hard to get the Toyota out of the bog and nothing bent.
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Reply By: Foss - Saturday, Jun 05, 2004 at 08:36

Saturday, Jun 05, 2004 at 08:36
G'Day Rochie

From a mechanical point of view having the hitch carrier in situe and pulling on that make a lot more sense. I.E. Having the load of recovery put into sheer across two equal cross sections of the retaining pin were it goes through the drawbar and hitch carrier physically make for a stronger connection. With the strap end around the pin there is a chance that the pin will bend and/or deform the hole in the bar as it has little support from the cross section of the drawbar RHS, about 4mm either side wall thickness. When the hitch carrier is added that cross section increases to 8mm either side and the force is no longer exerted at the centre of the pin but at the carrier/drawbar intersection on both sides.

when force is applied to the pin alone the pin will deflect/bend. The ends that pass throught the tube of the draw bar will bare against the front of the hole and then as the pin deforms axialy (goes banana shaped) the ends will start to put pressure on the sides of the tube trying to colapse it inwards behind the pin and explode it outwards in front. This is very unlikely to actually happen, however these are some of the forces that are in play while this is going on.

So, looking at that it's pretty clear that if you have the hitch carrier in the drawbar all the force applied is transmitted into the work rather than some going into deforming the tube and some deforming the pin ETC. It may seem inconsequential as has been pointed out above but sooner or later the steel in the pin will have been deformed once to many times and it will just break. It would be unlikely that there would be any flying parts other than the strap as the pin would not pull out of the tube with the strap. I would expect the draw bar to suffer a little bit though.

hope this helps.
Cheers
Foss.
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Follow Up By: Member - Roachie- Saturday, Jun 05, 2004 at 22:34

Saturday, Jun 05, 2004 at 22:34
Thanks for a very technical view-point Foss. I even managed to follow what you meant....
I'm still working on the "reality" versus the "theory" in my ol' grey matter though.
Cheers mate.
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Reply By: Wayne (NSW) - Saturday, Jun 05, 2004 at 08:42

Saturday, Jun 05, 2004 at 08:42
Roachie,
You have raised a good point. Many years ago I hade a Nissan Pathfinder, had a tow bar fitted, but it was only a bolt on tounge type. The tow tounge was long because of the spare tyre sitting right on top of the tow ball. I made my-self a shorter tounge and used a bow shackel as a recovery point. What you are talking about is the same thing. The bend in the tow hitch and the weld could be a worry, but I thinf that you wil find that it will be strong enough. If I doubt and the recovery is going to be a lot of strain on the vehicle, go back to the pin only methiod or let a Toyota handle the recovery.
The use of the snatch strap the tow bar and the pin. The pin is a 16mm high tensile piece of steel that is not ment to bend. When a pin is used, all the force is placed on the area of the pin where it passes through the hitch and the hitch receive. This has a lot of shear force placed on it, but being a high tensile pin it will with stand the shearing force better that a mild steel pin.
When a strap is used the load placed on the pin is spread over the width of the
eye, which is about 45mm. If you would use a thin cable, all the load would be spread over say 6mm and that is when the pin could bend. What I an trying to say is that if the load is spread over a large area the pin should not bend. When we do the snatch recovery demostration on our training weekend we use the strap and pin methiod and have never bent a pin.
I would be more concerned about the quality and condiction of the strap. When ever I do a recovery on a vehicle I will allways use my own gear. The amount of times I have seen an un rated shackel being offered up and the owner saying "doesn't matter if you break it mate they are only cheap " or a strap that has more cuts and nicks than a blind man shaving.
When a recovery is being set up, there are a lot of things to look out for,your only limited to what gear that you have at the time, but never limit the safty factor.
I will now get down off the soap box.

Wayne
AnswerID: 61803

Follow Up By: Bonz (Vic) - Saturday, Jun 05, 2004 at 21:37

Saturday, Jun 05, 2004 at 21:37
Wayne,

Always use the rated shackle on the vehicle being recovered and the unrated shackle on your tow vehicle, that way when it lets go is cannons AWAY from your vehicle. Of course if your vehicle is a Toyota then the reverse is acceptable also.
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Reply By: GeeTee - Saturday, Jun 05, 2004 at 10:34

Saturday, Jun 05, 2004 at 10:34
From the above posts and earlier replies to my query it seems that experience from some indicates it is OK to use the pin method. I must make sure I have a new hacksaw blade in the tool box just in case asnd maybe get another spare pin ( I have one already).
Thanks GeeTee
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Follow Up By: Crackles - Saturday, Jun 05, 2004 at 19:46

Saturday, Jun 05, 2004 at 19:46
I've bent two pins using 10 tonne snatch straps in difficult recovery positions but never bent one in 20 years using the 7 tonne strap. When they do bend they tap out pretty easy without the hacksaw.
Cheers Craig.....................
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Follow Up By: Member - JohnR (Vic) - Sunday, Jun 06, 2004 at 11:35

Sunday, Jun 06, 2004 at 11:35
GeeTee have you tried to cut one with a hack saw. I just reckon it may be hardened.

Crackles, I have a question for you as I haven't used my 10 tonne snatch strap yet. Does the shock seem to be much greater for the towed vehicle with such a highly rated strap? Truckster did put up a link to a sports car losing half its gear with a big SUV pulling it

I reckoned with such a heavy vehicle approaching 4 tonnes I should have a heavier one........ have a lighter one too.
Cheers,
Who?
John

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Follow Up By: Crackles - Sunday, Jun 06, 2004 at 21:02

Sunday, Jun 06, 2004 at 21:02
John. On a heavey vehicle the shock is only slightly more than the standard strap. I wouldn't suggest ever using it on lighter 4bys as the strap doesn't stretch as much jolting them more.
Before using the 10 tonne strap, check your tow bar and that of the vehicle being recovered are up to the challenge.
At full stretch there is alot of preasure being released and I'd suggest that many bars and their tow points wouldn't last long. (eg:my rear bar has 10 bolts into the chassis)
Before hooking one up, asses if the tow point is strong enough by asking yourself. "Can this tow point take the weight of 3 Landcruisers suspended off it?" Because that in effect is what you are asking it to do. Possibly when a recovery needs a 10 tonne strap we should 1st concider using an alternative. ie: winch, jacking the car up or dig it out. Cheers Craig....................
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Reply By: Dion - Saturday, Jun 05, 2004 at 12:59

Saturday, Jun 05, 2004 at 12:59
I am sure there are probably others that do this, but so far it is only Holden ones I have seen. The Holden genuine hitch actually has a tube welded into the square section. When the pin goes through, it is actually more uniformally bearing weight over a lot more area, than just the walls of the hitch itself.

Cheers,

Dion.
AnswerID: 61822

Follow Up By: GeeTee - Monday, Jun 07, 2004 at 11:05

Monday, Jun 07, 2004 at 11:05
That sound good but how do you put the pin thru the eye in your tow/snatch strap ? ? ? Think about it.
GeeTee
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Follow Up By: Dion - Monday, Jun 07, 2004 at 14:34

Monday, Jun 07, 2004 at 14:34
There is nothing to "Think about it" GeeTee. I was merely pointing out that the Holden hitch has the tube in it so as the hitch receiver pin has more load bearing area, than other types of hitches where the pin bears on two sections of 4mm only.
To snatch with this tow bar, I do either of two things, remove the ball and use the biggest rated shackle I can in the towball hole or I put the eye of the snatch strap direct into the receiver. I have turned up a bush 50mm long, o/d of 40mm and i/d hole of 16mm dia. This bush goes into the eye before insertion into the hitch receiver before the pin is put through.
No bent pins yet.

Cheers,

Dion.
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Reply By: Member - Camper (SA) - Saturday, Jun 05, 2004 at 16:23

Saturday, Jun 05, 2004 at 16:23
On the subject of spreading the load across the whole surface of the pin I was going to cut a piece of really heavy wall pipe so that it is just long enough to fit into the socket in the centre of the towbar and tape it into the eye of the snatch strap. Then when needing to use the snatch strap when the bubble bath hits the fan, push the eye with its piece of pipe taped across it into the towbar socket and push the pin through the pipe. When the load comes on the pin will have to shear(as foss seems to suggest above) rather than bend, requiring stupendous amounts of force.
Anyway I discussed this idea with the Hayman Reece people at the 4wd show and did not even get to base one. They reconed that using the towbar socket in any way to snatch was a no no because it could seriously distort the bar, so I gave the whole idea away. But if truckster has used the pin for 40 recoveries with success maybe I'll get the drop saw ready and get on with it.
AnswerID: 61837

Follow Up By: Mark- Sunday, Jun 06, 2004 at 19:28

Sunday, Jun 06, 2004 at 19:28
Just a quick comment, may only be relevant in theory anyway, but the shear strenth of steel is much lower (by a factor of about 3-4) than its strength in tension (or compression).

The pin is in 'double shear' (two holes in the receiver) which is stronger than a pin in 'single shear'. There will be both bending and shear stresses on the pin using the pin only method. I'm personally more comfortable loading the pin in this way than converting most of the load into shear which your proposal would do.

BTW I've never bent one using a strap.
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Reply By: Member -Bob & Lex (Sydney) - Saturday, Jun 05, 2004 at 18:00

Saturday, Jun 05, 2004 at 18:00
Naturaly Haymen Reese said it's a no no, Public Liability if you do it & it goes pear shape ( but they said ). All that aside I use the pin.
AnswerID: 61856

Reply By: Joe - Saturday, Jun 05, 2004 at 19:30

Saturday, Jun 05, 2004 at 19:30
We did 16 recoveries over the last weekend and all with the pin method, no problem.

However from past experiences,it would be far easier to drop the snatch strap over a hook fitted into the hitch.In the situation when your hitch is below water level, in 18" of muddy cold water and you can't see anything, and you have to feel your way, the hook has a lot of advantages.
I"m planning to get a hook
REgards
Joe
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Reply By: Swerv - Monday, Jun 21, 2004 at 21:03

Monday, Jun 21, 2004 at 21:03
Gidday Roachie,

The idea has merit and could possibly be done in an emergency however the only problem that I can see is that, should you place the pin of the shackle through the eye there is the possibility of the shackle not being centrally located. By that I mean that if the distance between the eye and the thread of the shackle is say for example 50mm and the thickness of the steel used on the tongue of the towbar is only 15mm that means you have 35mm of the pin is exposed. Now if the shackle, when placed securely on the tongue should happen to slide down so that the body of the shackle is resting on the tongue, this leaves that 35mm of pin facing towards the ground and once the strain is taken up on the shackle, due to the kinetic stresses involved, it could deform the shackle.(I have actually seen the results of what happen when this has happened to a 19 ton SWL 'D' Shackle). The solution to this would be to have spacers made up to fit either side of the pin when it is located in the hole of the tongue. This will keep everyting central and keep the stresses concerned going down the centre axis of the vehicle. Just make sure that you use a bow shackle and not a normal type 'D' shackle as this is the only style of shackle that is designed to take sideloads. There is then still the problem of the weak spot possibly created by the weld.

I would personally not use the system the way I have described it because I don't like to damage
1) my equipment
2) the vehicle and
3) it makes an excellent missile.

My preference is to check out from what I am told is 'BIG BALLS OFF ROAD WEAPONRY' and get hold of on of the solid towbar recovery inserts. They are a great idea and seem to be a lot safer way to conduct the business of recovery/self recovery.

Just remember when it comes to recovery NEVER UNDERESTIMATE THE POWER OF MURHYS LAW and THE GREAT PUMKIN. They really do make a great team.....

All the best Merv.
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