front coupling jaw for towing a 5-ton

[Robo McDuff]

Standard European trucks have (or used to have) a front coupling jaw dead center in the bumper. This mostly is just a re-enforced opening in the bumper where you can put the tow bar in and lock it with a pin. Farm tractors have them also.



The Daf army truck at right has both the two towing eyes as USA trucks have and the central coupling jaw with the pin sticking through it.

Did anybody ever modified a 5-ton or Deuce bumper to fit something like that?

I want to make one on our M51A2 and am pondering what is the best way to do that.



I don't want to make any construction in the center area below the actual bumper that will make problems to the winch cable. Cutting into the bumper where the US star is now is also not a good idea probably.

I was thinking about a removable set-up using with the original towing eyes as connecting points, but that is not so simple either since you would have both puling and pushing stability (when braking).

Anybody ever did this?

 

[Tow4]

I've seen dump trucks and garbage trucks that have a channel with a pin through it bolted to the front bumper to make it easier to pull them if they get stuck. Maybe you could make something similar to go on the front of the bumper that would also reinforce it.

 

[zebedee]

Front QD hitch

Hey Robo - always good to read your Euro posts.... kind of a remenisance for me...

I had designed this for my 816, haven't finished it yet. I guess you could substitute the NATO pintle for a slot and pin as per the DAF. On the wreckers and tractors there are the lower spade pockets that I used, you could fab some other kind of stabilising socket/shackle point...



Added benefit of these is for "nosing" trailers, "back loading" onto landing craft/flatbeds etc., where you are right over the pivot point of the item you are moving/shunting, rather than using the rearview mirrors.

In the States - they are not fans of using a rigid bar/tow pole(US) for pulling a 'casualty', opting to remove the second 'steering' person and relying on an 'A' frame/Hollybone/'Towbar'(US) with no driver.

Quick note.. Remembering too, that in Europe, a 'towbar' is what is mounted on the rear of a vehicle for attatching a 50mm 'ball' or jaw/pin or pintle hook to pull a trailer. US equivalent being a reciever hitch(US).

 

[73m819]

If you do the CENTER PULL without really building up the inside of the bumper center section, you WILL pull the center section into a big U, this section is very weak, every now and then you a truck on GL with a destroyed bumper caused be improper towing.

 

[zebedee]

Ron made a good observation - the stock bumper isn't that strong. I split mine while shunting in the yard when I backed past a 4"x4" post, just catching the edge. Post did not break and the bumper split on the bend... Must have been a bad repair in the past.

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What you could do is make a new front cross member that is stout enough, has the hitch in it - then use the stock front bumper, with a slot and the pin holes top and bottom, to simply 'cover' the "coupling jaw".



Not sure how the frame ends/bumper gusset plates would interfere, but they could be changed to suit the new X-mbr.

"NEXT!"

 

[Robo McDuff]

If you do the CENTER PULL without really building up the inside of the bumper center section, you WILL pull the center section into a big U, this section is very weak, every now and then you a truck on GL with a destroyed bumper caused be improper towing.

That's why I brought this up, even I can see that this front part is weak. Some newer European trucks without the standard coupling jaw use a special reenforced part which is mounted in front of the actual bumper and sticks out further forward. It would cover the whole bumper part from frame beam to frame beam, but looks horrible and is expensive.

I was thinking about all kind of constructions in front, on top and around the bumper but had not thought about making a real sturdy part BEHIND the bumper. Zebedee, you beat me to it. You guys are quick and good. Anybody did that already or you just pulled that out of your sleeve?

Fitting a special heavy duty part behind the bumper fitting directly to the two frame beams, and then just put the bumper in front of it should work without hampering the winch. I have to take the bumper off to straighten it anyway, so that should not be too much extra work, just have to figure out how heavy to make this new cross member with coupling jaw.

 

[jesusgatos]

Wondering how that would work. Sounds like you're talking about using something like a single towbar leg? Why? Seems like mounting something more like a traditional towbar to the shackle-mounts would be a much better solution?

 

[73m819]

If you are going to make a center pull using a MV bumper, I would make a plate to fit tight inside the contour of the center section, I would take right to the frame rails then WELD it in, NOT bolt it, the plate should be AT LEAST 3/4" thick, 1" would be better, when you make your center pull brackets, go THOUGH the bumper to the plate, weld to the plate, then weld the bumper to the brackets, you could also cut two slots though both the plate and the bumper, insert the pin brackets, then do a good 100% weld on the back of the plate and a good 100% weld on the bumper, if done right, it should look pretty good and pull the frame apart before you lose a bumper.
Still everything DEPENDS on GOOD and TIGHT bumper mounting bolts.

 

[Scar59]

subscribed for future reference, post #3 plans are spot on.
JC

 

[73m819]

Wondering how that would work. Sounds like you're talking about using something like a single towbar leg? Why? Seems like mounting something more like a traditional towbar to the shackle-mounts would be a much better solution?

ROBO is in Europe and in Europe this is how they tow using a SINGLE leg towbar, he wants to be able to be able to tow both ways (single and double leg), because very few towing outfits will be set up for a double leg towbar towing

 

[jesusgatos]

Thanks, know he's in Europe. Was just wondering why it's done that way over there.

If you are going to make a center pull using a MV bumper, I would make a plate to fit tight inside the contour of the center section, I would take right to the frame rails then WELD it in, NOT bolt it, the plate should be AT LEAST 3/4" thick, 1" would be better, when you make your center pull brackets, go THOUGH the bumper to the plate, weld to the plate, then weld the bumper to the brackets, you could also cut two slots though both the plate and the bumper, insert the pin brackets, then do a good 100% weld on the back of the plate and a good 100% weld on the bumper, if done right, it should look pretty good and pull the frame apart before you lose a bumper.
Still everything DEPENDS on GOOD and TIGHT bumper mounting bolts.

Would prefer to bolt something like this to a vehicle myself, and you'll end up with a lot stronger pull-point if you create some type of boxed structure. Much stronger than a piece of flat plate or C-channel. Tying into the shackle mounting points is also a good idea, knowing that they're designed to take those kinds of loads.

 

[73m819]

A 1" thick, welded in plate will give more support then the frame rails or mounting hardware can handle, if you start drilling holes for bolts, you WILL weaken the assembly, no matter how tight you get the bolts there still be some movement between the pieces of steel under high load, using box tubing in this use will be in fact nothing more then a large C-channel which in turn will be weaker than a 1" thick plate of steel because the wall of the tubing will be thinner, relying on the walls for strength but NOT providing strength where it is needed which is at the center of the bumper. The back of the tubing will not be doing much other keeping the walls from buckling, because the center of the front of the tubing will take ALL THE LOAD.

 

[jesusgatos]

Why would any holes would need to be drilled? There are already tons of bolt-holes in the framerails for attaching winch extensions and bumpers and whatever else. Maintain that bolting would be preferable to welding anything into place in this situation. Especially given the differences in material thicknesses you're recommending, and the intended use. If you wanted to weld a crossmember to the framefrails, still wouldn't weld a 1" plate directly to the framerails. Bad idea. Dunno how to address your assumptions about plate vs. boxed structured, except to say that you are mistaken. Boxed crossmember is going to be superior in every way to flat plate here. An I-beam gets the majority of it's strength from the distance between the top/bottom flanges. Rectangular tubing and boxed structures would further increase strength, mostly by resisting torsional rotation (twisting), which would be important in this application. Are you assuming that the mounting point would only be pulling on the front face of that boxed crossmember? Take a look at how I built the mounting points and receiver hitch for this rear bumper. Pierced through the crossmember. Super-strong.

 

[73m819]

NOT to the frame members BUT contoured to fit the center section of the bumper, from frame rail to frame rail.

 

[gimpyrobb]

I'd just put some shackle mounts on the bottom of the bumper, then you have 4 mounts, two on top, two on the bottom. Pull the pins from whatever you make, and you are back to "basically" stock front MV.

 

[Robo McDuff]

Ron and Zebedee, spot on. In Europe, its either a tow bar or a wrecker with spoons to put the front tires in. Never saw a truck being pulled with this double leg thingy. In addition, these center front hitches are very handy for taking a trailer "head on" for better maneuverability in yards. For example pushing a frame trailer under a load box on legs at night in a dark spot of a busy distribution center (had to do it, with the trailer head on I could manage, driving backwards not in a million years, let alone the few minutes I had for it.

Gimpy, that's basically what zebedee showed in his first post.

What I saw as problem, both strength-wise and also esthetically, is that making a slit in the center of the winch bumper leaves you almost without front-facing metal, like half an inch or less top and bottom. I know that the strength comes from some very sturdy horizontal plates, but it looks weird.

Maybe a variation of zebedee's first option is the best way, but not with a pintle hitch but with the coupling jaw inverted, or with a normal coupling jaw below the shallower part of the bumper. Bit in time pressure now, I will make some drawings later. Keeps the bumper original.

 

[jesusgatos]

NOT to the frame members BUT contoured to fit the center section of the bumper, from frame rail to frame rail.

Ah, now I understand. Would still be a lot stronger if you were to reinforce the bumper by boxing the backside, as opposed to just adding more material to the front of it.

Does the mounting point need to be at any particular height?

 

[zebedee]

Alternative, permanent mount idea to posts # 3 & # 5 . (Robo - I added a piece of the TM showing the "two leg thingey")



We also have to understand the purpose of the intended hitch:

Nosing trailers - strength not important - rolling resistance to be assessed, likely minimal.
Towing disabled truck on highway using rigid bar, tow pole(US) - strength more important, still consider rolling resistance.
Recovery of stuck vehicle - strength most important however use for this unlikely vs tow shackles/axle/frame.

Comment on rigid bar towing/tow pole(US):
In the US - even the military, occupancy of disabled vehicle is considered a no no. UK/Europe - not so much (short distances only - yard shunting, bump starting, just "round the block"), therefore disabled vehicle can be steered by driver. This negates the need for a Hollybone/towbar(US).
For off road operation, a rigid bar can be used to make a 12x12 combination of two trucks when front or rear truck is stuck in convoy and perfect alignment [for a towbar(US)] is not possible.

Further note on civi towing in Europe;
http://www.youtube.com/watch?feature=player_embedded&v=wUckxI8jW2Q Clip found on Recovery Mechanics Past n Present forum.
It seems that underlifts with axle forks are becoming redundant, due to questionable front axle strength. This has resulted in the towing industry reverting to frame end lift attachments which is full circle back to the military style of suspended towing. No more grubbing around under the truck...
NB. Not sure what would be used with front end damage but I am sure there is some kind of attatchment in one of those lockers!

 

[Robo McDuff]

Never saw those lift systems, amazing trick. That's probably why modern trucks - certainly tractors - often do not have these old type of front coupling anymore.

These triangle pulling systems, those legs are fixed or they vary in length when turning?

 

[zebedee]

......These triangle pulling systems, those legs are fixed or they vary in length when turning?

The detail in the top left of pic in post #18 is from the -10 FM for the 809 series 5 ton (operators manual), also covered in the towbar TM; 9-4910-593-12&P, in FM 20-22 Vehicle Recovery Ops and FM 4-30.31 Battlefield Damage Repair... All of these were in the Misc part of the TM section of this forum... but they are not there now!!........ Mods, what happened???

Legs telescope for initial setup, but are pinned at shortest length to allow a turn. It effectively turns a casualty into a trailer similar to the drawbar on the front of a dolly at the front of a full trailer (hay wagon style) not a semi trailer. Good for onroad towing solong as the tow vehicle has the mass (ballast) to overcome the tendancy of the casualtys steering to go straight on in a bend since the turning of the tow vehicle doesn't directly 'steer' the steering wheels of the casualty - like a dolly(full trailer)/hay wagon.
Many types of "feet" are required to match up with the tow shackle brackets of various vehicles inc, chain feet that clamp around an axle tube.

US wreckers used them for suspended towing (as detailed Off Road in above TM and FM's) from WWII up to M936's. Other countries had the opposite setup where the 'point' of the triangle was under the hook/point of lift, using a dedicated frame (look up Holmes 750/850 elsewhere on Forum - good thread is Wreckerbed modifications or wrecker wish list of mods). This setup aleviates an understeer situation and leaves the A Frame/tow bar for flat towing.

..... Anyway, we're getting off topic, however since you threw the curved ball (with the "triangle thingey") I guess it's ok for you to hijack your own thread!!