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MuddyOval
Guest
Pulling on one frame rail of a ladder-frame truck? I saw a P38 Range Rover destroyed by doing that.
Safe to use recovery strap on hitch pin instead of shackle?
- Thread starter winkosmosis
- Start date
michaelgroves
Explorer
I'm pretty sure, given that AntiChrist recommended a bridle, that he meant recovery points attached to the frame rails.
ntsqd
Heretic Car Camper
It really is a combo of all of them, but it is mostly bending.
You can treat it like it is a simply supported beam and do a partially distributed load analysis on it, but first you need to know what the peak loading is and have an average width for the loop, while under load, where it goes around the pin.
Without exact numbers known to reasonably repeat it comes down to being a somewhat sophisticated WAG.
I'm somewhat doubtful of the bolt-on shackle mounts. I just don't see enough weld bead length on them to make me comfortable with using them.
A centered point attached to something able to distribute the load to both frame rails equally is my own preference.
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MuddyOval
Guest
For some reason I missed the bridle part of that. If the receiver is mounted to a cross bar between the frame rails that is strong enough to take the strain, then I'd just use a receiver hitch. The ones on the Discovery, for example, are bolted to a crossmember. The Class III hitch I had on my Wrangler was uber strong and tied to the frame as well. I just haven't seen any cheesy Class III receivers, personally. Most tend to be really stout.
Of course, there's always the guy who bolts a 2" receiver to the underside of a bumper and thinks it's strong. :Wow1:
Of course, there's always the guy who bolts a 2" receiver to the underside of a bumper and thinks it's strong. :Wow1:
michaelgroves
Explorer
As my earlier post said, the problem is that it might well not be strong enough. It's a long bar, designed to take towing loads, not a snatch pull right in the middle of it. If there's any chance of bending the pin, I'd say the bar is at much higher risk of bending!
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MuddyOval
Guest
most are pretty beefy though- look at some of the 'off road' bumpers people mount shackles to or weld on loops for shackles. Many of them are far weaker than a proper DOT approved class III hitch but people are slapping all kinds of recovery points on. It's kinda scary what people fab up and think it's all great but have no engineering background.
computeruser
Explorer
Excellent point. I'd hardly figure on the pin being the weak link, especially on the rusty old receiver hitch setups hanging off the back of so many trucks.
Utilizing two points at once on even a straight recovery would seem to inject unnecessary forces acting on the frame into the mix, unless there was some really good reason in a particular instance to do otherwise. One solid point for a recovery ought to get the job done most of the time. I had two bolt-on D rings (like the type bolted/welded to trailers) positioned just outside of the frame rails on the bumper of my YJ years back, and actually deformed the bumper by using a chain Y to which I attached a ComeAlong when pulling out shrubs. The bumper was OEM, 3/16" bent sheet (formed into a C channel). ComeAlongs don't generate all that much force...using one point would have been a better idea by far, even for pulling shrubs!
In a perfect world, I'd like to see JATE rings on the frame rails, which seems like a slick deal. But Jeep didn't think that was a good idea, for some reason or another. However, it might make for a fun fabrication project.
winkosmosis
Explorer
I had to look up Jate rings. http://www.landroverstuff.com/jaterings.htm
Can you run one of those through the hitch pin holes?
BTW I've seen a manual specifically say not to recover using two points. The force pulls the frame rails together.
The army recovery manual says to use a spreader bar
http://www.google.com/url?sa=t&sour...LmcWobOKBCRGY7HIA&sig2=gRuHpPU-lwtkS_0RSu4Izg
Can you run one of those through the hitch pin holes?
BTW I've seen a manual specifically say not to recover using two points. The force pulls the frame rails together.
The army recovery manual says to use a spreader bar
http://www.google.com/url?sa=t&sour...LmcWobOKBCRGY7HIA&sig2=gRuHpPU-lwtkS_0RSu4Izg
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MuddyOval
Guest
Don't use JATE rings for harsh recovery. For a mild pull without using kinetic ropes, maybe... but they are meant to tie rigs down, rig for parachutes or sling them from a helicopter- not yank the bejeebus out of them.
michaelgroves
Explorer
When I was in the army, using Jate Rings or equivalent, with a (long) harness was SOP for any vehicle recoveries. Always use a double recovery point if possible. The long harness prevents any significant force pulling the frame rails together. There really is no downside to the harness method.
The very worst scenario is to have a short harness - say, a short piece of chain bolted across in place of the crossbar, with the snatch strap pulling in the centre of the chain. If the chain were tight, the force on the chain (and the force pulling the framerails inwards) would be many times the force on the snatch strap! But as the harness gets longer, the inward force rapidly drops off.
I'd use a spreader bar if the harness were short, but otherwise it doesn't serve much purpose.
Antichrist
Expedition Leader
I'm not saying they aren't stout, but the fact is that are only rated to 10,000lbs (or less depending on what source you refer to).
I couldn't find in the link you posted where is says not to use two points. I did find where it said to use both shackles if at all possible (first paragraph under "Winch Safety").
In any case, a properly rigged bridle serves the purpose of a spreader bar, but is more versatile and, arguably, easier to stow.
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MuddyOval
Guest
I'm betting you were using a winch in a very controlled recovery- not putting a springy inertia strap on there and yanking the hell out of it. JATE rings are not rated for inertial recoveries. The bolts are smaller than the cross-pin on the previously debated hitches.
winkosmosis
Explorer
It was some other manual. May have been the FSM for my XJ
BIGdaddy
Expedition Leader
One thing I have to consider too, is that my jeeps hitch isn't the weak link on my rig. It's my rear axle. I've heard numerous tales of woe when a transfer case or transmission input/output shaft has grenaded or the same situation occuring with that weak rear axle.
This, pragmatically limits my use, in my mind:
- Using hitch for towing trailer or unobstructed disabled vehicle over smooth/graded surface.
-Recovering a similar sized vehicle via front frame mounted winch bumper only (using winch, not d-rings), never via inertia strap on hitch.
-Winching enhanced by strapping myself to a tree on rear hitch, applying tension, and then attaching front mounted winch to stricken vehicle. This works great on trucks larger than mine, (worked well recovering a dually with the grand vitara I used to have)
These are situations I see arising on a normal basis, and using others' catastrophic experiences as fodder, have become my SOP over years and
will continue to preserve my drivetrain.
R_Lefebvre
Expedition Leader
All this talk reinforces my feelings that... if I can recover with a *light* tug on the kinetic strap, then fine. More than that, I prefer to take the time to winch, if winching is possible (suitable anchor, etc.) Some of the violent snatch recoveries I see... yow.
Another aspect maybe worth discussing, is the rating of the kinetic strap vs. the weight of the vehicle. When I was doing recovery for a rally, I was using my 20,000lb rated kinetic strap, and it seemed to be stiffer than optimal for the light vehicles I was pulling. Seems like a lower rated strap for pulling cars would be stretchier, and gentler, whiles still getting the job done?
Another aspect maybe worth discussing, is the rating of the kinetic strap vs. the weight of the vehicle. When I was doing recovery for a rally, I was using my 20,000lb rated kinetic strap, and it seemed to be stiffer than optimal for the light vehicles I was pulling. Seems like a lower rated strap for pulling cars would be stretchier, and gentler, whiles still getting the job done?