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Old 09-30-2019, 08:43 AM   #1
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DIY Towbar: what a drag

Thinking about my SMB getting a little 'long in the tooth', and my desert meanderings. I know that AAA won't send a truck if you get stranded on a dirt fire trail, let alone well off the beaten path like Saline Hot Springs, where I came close to getting stuck a coupe years ago. My though is anyone with a strong towbar could help rescue me, if I get stuck a long way from home, or 50 miles from the nearest paved road; But I don't own a strong enough towbar.


I decided I needed a towbar, all figured out, well before I ever need it. Beside, one way to guarantee you'll never need to tow your rig, is to own a means in which to do so! (one of Murphy's laws I think)


Flat towing a car or truck isn't a big deal, I've done it too many times to count. But all lightweight cars. The key is having the right equipment, a strong, roadworthy connection between the rig being towed, and the tow vehicle.


With my van tipping the scales at 9000lbs, and looking around a Blue Ox and other commercial solutions, they are all high dollar, about $1k, and frankly not very safety inspiring.



So I looked at what the Military does, with the H1 Hummer. One problem with the Hummer towbar solution, just buying one from ebay, is the cost, the shipping cost, and getting the right adapter feet for it. I researched the heck out of the mounts and different light, medium, and heavy military tow bars, and was more confused than when I started. I even looked at a local surplus towbar intended for a 19 ton Stryker fighing vehicle, which was only $100 no shipping, but the 4" diameter x 8' long bars, 200lbs are way overkill, would need shortening, adapter feet, and modifying.






At the end of the day, the hummer solution: I'd be into it for $600-$750, maybe $900, and be stuck with a Lunette ring/Pintel deal.








Pretty strong stuff, folding (I like), but uses a Lunnette Ring and requires a Pintle Hook type hitch. I think the shipping weight is over 100lbs.



If I get stuck, and happen to have my towbar, I'd need to also have a Pintel hitch, which I don't own, add another $150-$400 depending, and maybe another 50lbs.



After considering all of that, I decided to design and fabricate my own, starting from a clean sheet of paper. The goal was to make something as strong as an ox, no heavier than it needs to be, say, less than 75lbs. keep the cost under $200 if possible.



I wanted a more common trailer ball set up, 2-5/16" I think, too, so one of my friends with a 1 ton truck can come get me if I get stranded. No Pintel necessary.



I just modified my front bumper with features like a towbar in mind. Without sounding too much like an engineer, I followed the load path, and strengthened the elements that during starting and emergency stopping are in compression and tension, by adequately reinforcing them. That starts with a solid foundation:












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Old 09-30-2019, 08:48 AM   #2
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Welded up and ready to instal


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Old 09-30-2019, 09:10 AM   #3
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The finished product, bolted joint on one side for ease of stowing (so I don't have to deal with a huge "Y" shaped weldment), welded on the other. 2-5/16" ball coupler rated at 14,000lbs





7/8" grade 8 connection bolts, too long, so the unthreaded portion is carrying the load. That bolt in double-shear configuration is good for north of 60,000 lbs of force per side. Somewhat down-rated because I'm using a 7/8 bolt in a 1" hole, for ease of assembly at roadside.





Arms made from 2 x 3 x 3/16 wall steel tube. I cut out a weird shaped section, used a torch and rosebud tip to heat and bend the 'ears' to mimic the coupler angle







reinforced with inner and outer 1/4" thick doubler plates






Rosette or plug welds hold the plates in, spreading out the load





Then welded along the edges


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Old 09-30-2019, 09:16 AM   #4
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Looks great! I did the same thing for one of my buddy's buses. He had a party bus business, and one of them was built on the GM P30 chassis with the 6.5L diesel. It threw a rod in Utah, and paying for a tow to Portland was prohibitively expensive, so I threw the welder in the van, and built a tow bar from scratch, knowing that was unlikely to be the first breakdown for that motor.

One thing I learned from the 800 miles tow: If the bus doesn't steer well on its own, it's not going to track well when being towed. So make sure you keep everything aligned well!

Also - I went with a pintle hitch because ball couplers can pry open the latch during hard braking when there's no tongue weight. No worries about that with a pintle hitch.
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Old 09-30-2019, 09:17 AM   #5
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7/16" of wall thickness total for a 'house pulling strong' connection








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Old 09-30-2019, 09:33 AM   #6
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Figuring out the coupler end.


I wanted 1 leg to be permanently affixed, the other a strong bolt connection





The welded leg is easy, the couple was manufactured with that in mind, making that connection a 'no brainer'. The bolted leg was a lot more trouble. Again, strong, stowable, relatively easy to assemble beside the road was the goal.











I decided I needed a couple 'nut plates' inside the bolted leg


I laid out, drilled and tapped some 3/8" steel plate for 3/8-24 threaded holes for the side, and a second one for the top





nut plates mocked up and in position









My wife did these rosette welds, her first attempt at welding anything
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Old 09-30-2019, 09:38 AM   #7
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bolted leg completed


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Old 09-30-2019, 09:41 AM   #8
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The finished prodect, still needs paint

I'm happy with the way it came out, well, I'm not unhappy...



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Old 09-30-2019, 03:02 PM   #9
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Cost breakdown:



14k lb Coupler, e-trailer $40
7/8" Grade 8 hardware $30
2 x 3 steel tube $120*
1/4" x 3 plate $45*

3/8" steel for nut plates (reclaimed from another project, zero cost)



*fortunately I have a friend whom I help out a lot on his projects, he bought the steel as part of a larger buy, and gifted it to me. So the steel was zero out of my pocket


Hours fabricating: 3 days ?
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Old 10-01-2019, 12:24 PM   #10
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Damn, your wife's welds are as good as any of mine, and I've been welding for most of my life. Nice set up, but now that you have it, you will never need it (assuming you bring it along).
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