"Rescued" M816 Wrecker

[USAFSS-ColdWarrior]

Another thought would be to simply buy/borrow/use a DOLLY. Hitch the dolly to the Pintle Hook, back the Dolly's Fifth-Wheel under your "new" trailer, connect air and power, and pull away. No fuss. No muss.

 

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Another thought would be to simply buy/borrow/use a DOLLY. Hitch the dolly to the Pintle Hook, back the Dolly's Fifth-Wheel under your "new" trailer, connect air and power, and pull away. No fuss. No muss.

View attachment 689776

Dolly is out of the question because of how much of a pain in the ass they are to back up. Alot of the places I like to go aint exactly cooperative with the space required to back up a dolly.

The towbar mod is something that I was already planning to do eventually, adding the 5th wheel to it isn't much complexity.


Measuring out ideas for where exactly to place the mounts for the towbar. With them up higher it will make for the towbar being more flat when lift towing another vehicle which is good. Downside is if they are up that high then the 5th wheel will be angled forward pretty far.

Also did some more wiring on the tow lights. 50ft of harness for it, just have to order the trailer plug to complete the harness. Adds alot more light to the rear of the wrecker when mounted there.

 

[Csm Davis]

The under reach setups are great on the modern wreckers but have 2 big downsides for me. Very expensive, and kill ground clearance.

The other common Holmes towbar setup can be used to tow a 5th wheel trailer but it limits how tight of a turn can be made, air connections are in the way on this trailer. Plus for towing a 5th wheel it just doesn't strike me as a strong and reliable way to connect to the kingpin, compared to a 5th wheel hitch.

So got me thinking. I have the 5th wheel from a m931, medium towbar, some 3/8" plate, and the frame from the m51a2. Figure a way to make a similar Holmes 750/850 towbar. flip the towbar around so that the feet are mounted to the square tubing that the outriggers slide in. Either trade the outer tube with the lunette ring on it for one with the pin, or cut the ring off and replace it with a pin end. Then attach the 5th wheel to that end of the towbar.

If you go tow bar route use a pickup truck size fifthwheel much lighter and stil rated for your trailer. But as the chaplain pointed out that a dolly would be better, when you learn how to back it up. You can do it!

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[Csm Davis]

As to a reversed tow bar mounts, cut or remove the rear bumperets and or add the high mounted ones like Zebadee shows on the Australian 816

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[Csm Davis]

Here is my cut off bumperets

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If you go tow bar route use a pickup truck size fifthwheel much lighter and stil rated for your trailer. But as the chaplain pointed out that a dolly would be better, when you learn how to back it up. You can do it!

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As I stated earlier a dolly is out of the question, takes up too much room to back it up. Lots of the places I like to go are in the mountains, not exactly forgiving and space providing that backing up a dolly requires.

A pickup 5th wheel would work, but already have the one from the m931 sitting here and it allows side-side movement which is great for me.

Cutting off the bumperets would work perfect when towing with the 5th wheel. A bit low when lift towing however I do have 2 sets of those rear shackle mounts (second set from the m51a2 remains). Could remove the bumperets and mount the second set up high. If the height needs to be adjusted alot it wouldn't be difficult to pull the 2 pins and move the towbar up/down.

Guessing you are talking about this pic of Zeebeedee's?

 

[Csm Davis]

Okay so mainly just giving you crap about backing up a dolly, although it will turn tighter than just fifthwheel. And yes that's the upper mount I was speaking of. The upper hitch works great for trucks that have only over bumper mounts, like m35 and 809 series trucks.

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Okay so mainly just giving you crap about backing up a dolly, although it will turn tighter than just fifthwheel. And yes that's the upper mount I was speaking of. The upper hitch works great for trucks that have only over bumper mounts, like m35 and 809 series trucks.

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Yea sarcasm online, sometimes I read it right and other times goes right over my head, taking some of my red hair along the way haha.

For mounting the 5th wheel to the towbar heres what I'm thinking. Take the plate steel that is used for the adapters (1/2" or so) and mount them along the front and back edge of the 5th wheel base. Have the back edge of the 5th wheel base centered on top of the end of the towbar and run 2 pins down through the adapter plate/towbar. Then on the front edge of the 5th wheel base drill 2 holes there for pins to go through the adapter plate on that edge, and through the towbar. Lastly 2 more holes drilled in the front adapter towards the center for the lifting chains to connect to. That would secure the 5th wheel with 4 pins on top of the towbar, and leave the towbar angled for more side-side strength.

Sound solid enough?

 

[Csm Davis]

Possibly need to see it drawn out, but I just had a thought of using the upper and lower shackle mounting points we were just speaking of and using both to hold everything up

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Quick sketch of the idea. The 2 long rectangles are the tow bars and the disk is the 5th wheel plate. The short rectangle tying everything together is the front adapter for the 5th wheel.

View attachment 5th wheel setup.pdf



With your idea of using both upper/lower mounts together, like a rigid triangle? or hydraulic cylinders to raise/lower the towbar?

 

[zebedee]

How about making a lunette eye hitch extension/converter for the front of the trailer - quick attach to the kingpin of the trailer? I am sure the wreckers pintle hitch is up to it..





NB. This a purely an idea.
Extension of 'frame' to the left of the pic, then chaining to trailer frame would reverse forces on king pin - like a tru-hitch.

 

[USAFSS-ColdWarrior]

View attachment 689983

How about making a lunette eye hitch extension/converter for the front of the trailer - quick attach to the kingpin of the trailer? I am sure the wreckers pintle hitch is up to it..

I'd like to see some SERIOUS ENGINEERING ANALYSIS on the TORQUE MOMENT and DOWNWARD FORCES on the latch mechanism that engages your King Pin with this design concept.

Essentially, I see a FULCRUM effect with the pivot point being the leading edge of the trailer's Plate and Chassis. The Pintle Hitch/Lunette Ring would have upward forces while the Fifth Wheel's King Pin LATCH would have to have sufficient strength to prevent it from "slipping" off the lower end of the King Pin.

These forces multiply with a loaded trailer. And, they become DYNAMIC LOAD FACTORS when traversing any angular deviations in the road surface or any pavement (or off-road) roughness, MULTIPLYING the FORCES that are encountered.

Additionally, on A BOUNCE the FULCRUM moves TO the King Pin LATCH, and while the Pintle Hitch/Lunette ring moves "downward", thus BREAKING the contact of the rigging against the forward leading edge of the trailer AND, when this is lost/separated everything - YES, EVERYTHING can get catty-whompass in an instant.
So, I see a NEED for some sort of mechanical engagement at the trailer's leading edge to preclude SEPARATION in a BOUNCE.

Failing to consider these forces, and only looking at the forward (and backward when braking) forces induced when towing could prove CATASTROPHIC ! ! !

 

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Those up/down forces are part of what I like about the 5th wheel on the towbar setup. Same with the military 5th wheel since it pivots side-side and front-back, easing the forces on the kingpin even more.

There are 5th wheel hitch kits for the Holmes towbars so I know it will handle the stress. What I don't like about those kits is that it's not a positive lock on the kingpin like a hitch, it's just a tension hold. If there is a failure with the cable on the crane (breaks somehow) then with the civi kit the trailer is no longer attached to the Holmes towbar. By using a 5th wheel hitch in my plans if the crane cable fails for some reason the trailer stays connected to the hitch/towbar/truck. Falls to the ground yes but it won't separate from the truck.

Bear in mind with any of these setups the truck can't tow really heavy because the hitch sits way behind the axles. Same problem with lift towing so thats the way I'm figuring it's towing capability. Trailer that I'm picking up is the same size as the m146 and probably about the same weight (below 10k).

 

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Much better rear visibility with the tow lights hooked up.

 

[Another Ahab]

I forgot, red, have you got a back-up camera on the rig?

 

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Nope don't have a backup camera yet.

 

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Wasn't a planned modification for today but it ended up that way haha. Arrived at the wrecker this morning to work on the pickup and decided that I've had enough working in the sun all the time. I've removed/installed the cargo cover at least a dozen times, normally on my own, and it's a pain in the ass. Heavy and must be dragged up/over in steps. So the m36 cargo cover got some mods today to make it lighter and work better for my goals of a bimini top and a side awning, both of which must be easily removable. Started by cutting the end panels off the front/rear.




Noticed that with the cover turned sideways it was a close fit to the length of the wrecker bed. Placed the edge towards the top of the corners right where that little nub sticks out.





Somewhat stretched out, just tied off for now. Eventually will use 2 poles to hold up the outside edge of the awning.





Worked on the truck under the awning all afternoon, much cooler and no concern of sunburn. Thinking of cutting the cover into 2 pieces, the bimini top and the separate awning. Would make each section much easier to handle and that would allow the awning to be attached to either side as needed.

 

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Decided where to cut the cover and will be ordering a pair of tent poles to hold up the far edges of the awning. That project will take place later (wasn't a high priority project just didn't feel like working in the sun anymore).

Looks like my plan A option for borrowing a tractor to recover the trailer on monday has fallen through, so in a rush to try and get the towbar modified and 5th wheel hitch attached to it before then. It's going to be rough for now but don't have the time to finesse it at the moment (working this weekend).

Started by cutting off the bumperettes. Was going to unbolt them but as Csm Davis mentioned in another thread, it's a convoluted mess in that area.





Laying out some of the parts to get ideas





3/8" plate, getting the measurements and most of the holes taken care of. The 5th wheel plate and its original 1" thick adapter plates are being bolted on top of this 3/8" plate. The modified outer towbar legs are being bolted to the bottom side of the 3/8" plate, all grade 8 hardware. Eventually will use 2 shackle mounts bolted to the underside of the 3/8" plate at the front to serve as the lifting chain attachment points.





Started getting dark so packed up the tools and used the highlift jack to raise up the towbar/plate to get a better view of what the finished product will be.

 

[Csm Davis]

Yeah those bolts hold the whole rear crossmember in place. What are you going to hold it all up with?

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Planning to use a chain to hold it up.