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The danger of modifying trailers

kendelrio

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I have berated myself and beat myself up about what I'm posting. I'm not posting it for us to dog pile on me. I understand I made a mistake and fortunately no accidents happened, no one was injured and I now know how to correct my mistake.

This is an infomational post to help keep someone else from making the same mistake I made.


First, a little history about me:
I've driven nearly every type of commercial truck/tractor combination you can with the exception of drop decks and low boys. Class "A" driver with bulk liquids, hazmat and double/triple endorsements. Other than that- yup. 52' vans, flatbeds, bulk liquid, doubles, triples, 27' dump combinations etc. Drove them and in probably 700,000 miles, only had one incident where my truck slid in ice while my trailer was offtracking pulling out of a truck stop and the trailer hit another truck. Other than that, not even a fender bender. I try to be as safety conscious as I can.

I understand weight distribution, axle loads etc.

What I'm discussing today is the "wiggle" factor or "trailer sway". When you load the rear of a trailer heavier than the front of a trailer and you end up with something like this:


I bought an M1061A1 flatbed trailer with the idea of building a dove tail so I could carry my M37 and M715. The trailer is more than rated for both of their weights on and offroad. (5,500 WoW for the M715 and 5,987 W/W for the M37):

Screenshot_20230406_073724_Gallery.jpg

After building the dovetail and hauling the M-715 a few times:

trailer 2.jpg

I noticed the 5 ton seemed to want to "float". I couldn't figure out what was going on.....

What I was dealing with was trailer sway! It was so slight because the weight of the five ton didn't allow it to become more pronounced. I felt it in my gut, like I was losing control of the trailer but couldn't figure out what was causing it. I honestly thought it was because I was unfamiliar with the towing characteristics of the 5 ton. (Never drove them in the Marine Corps and everything I've learned has come from owning Bertha). As far as trailer weight goes, I know the front of the M715 is heavier than the rear, so I figured it can't be trailer sway because the front of the trailer should be heavier than the rear due to the engine etc being up front.....

The number I should have paid attention to on my data plate was this one:

Weights circle.jpg

Fully loaded with 10,000 lbs, there is only 445lbs on the lunette. I added at LEAST 300 pounds to the back of the trailer, and having the weight of the M715 behind the wheels didn't help either, so I literally have no tongue weight to speak of.

So! To correct this issue, I have the option and ability to add several hundred pounds to the front of the trailer while keeping it under its GVWR. I'll be adding an electric winch, tool box and battery to the front in order to get some weight back on the front of the deck. I'll be taking truck and trailer to a local truck stop to scale it and ensure I get back to a proper weight ratio.

Lessons learned:
If something feels wrong, something probably is. Stop and figure it out.
When modifying any equipment, take into account EVERY aspect of the modification. Honestly my biggest concern was the departure angle being affected by the dove tails, not the weight on the tongue
Always work within the limits of the equipment.
Realize mistake are and will be made, and try to minimize the effects of them.

Again, I'm glad no one was hurt through my ignorance and there was no black stain put on our hobby.
 

zebedee

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Thanks for sharing, as Rory says, it takes a big man...

I had a 1061, wanted to do the mod that you did, but sold it before I ever got around to the mod. (Found an 870A1 to go behind my 916A1).. My thoughts would have been to move the axles back to put the deck+tail/2 point jst infront of the axles mid point (walking beam pivot). The object to was to look similar to the LMTV trailer.
 

MarkM

CODE BROWN...It's all going to sh~t !
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I did something really dumb back in the 80s. I suspect weed had to be involved. Lol.

I "tried" to flat tow a 51 M42 using a 91 Mazda B2600 4x4. 5k plus lb M42 being flat towed with a 3k lb mini pickup, what could go wrong?

I had hauled all kinds of trailer loads with that truck including a 26' Searay with okay results believe it or not so I figured okay I can do this. After trying to pull that M42 I very quickly realized I was going to die if I continued. I made it maybe 5 miles. When the M42 truck wanted to turn the little Mazda had no weight to pull the back in line and I had a 60 mike drive to go.

I quickly (Thank God) secured a flat bed tow truck to haul the old girl home and that was the only smart move I made that day.

No matter how good a driver you are sometimes you have to get off your high horse and think about what lunacy you are about to embark on.

Mark
 

m1010plowboy

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I searched "tongue weight sweet spot" to better understand why the manufacturer data-plate had less than 10% tongue weight on your trailer. It was a big distraction and took hours to remember what I was supposed to be looking for.....maybe sweet spot was the wrong term.

It was logical to anticipate that the data-plate, low percentage tongue weight empty, could be carried to a comparative percentage with the load. I'll bet you were real close to it not being an issue or a story. It's always good to re-visit this stuff so thank you.


We upgraded to commercial hitches and added leaf springs to trucks while we made our mistakes. The photos and stories are mostly legendary only when we make mistakes. Putting 6000 lbs part way between the hitch and the wheels meant we'd be 1000 lbs over capacity on the tongue........which is pretty funny, after you spend the money to do it.

DSCF0964.jpg
 

kendelrio

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.

Hate to admit that I know nearly nothing - but I did save a picture from a 2014 post from @MWMULES .
This is how it is installed.

View attachment 894692

Thinking though... Is your lunette ring bolted on? If so, I know for sure on my M989a1 there is an extension bolted on.

.
Welded. Would you be willing to sell the extension?
 

chucky

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Im curious how that extention is going to change any of your problems ! With the axles in the center of the trailer they were wanting the brunt of the load on the trailer axles not on the hitch your not changing the balance of the trailer until you change postion of the load ! Try turning the truck around then pull it and see if it changes .
 

kendelrio

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Im curious how that extention is going to change any of your problems ! With the axles in the center of the trailer they were wanting the brunt of the load on the trailer axles not on the hitch your not changing the balance of the trailer until you change postion of the load ! Try turning the truck around then pull it and see if it changes .
I see what you're saying. My concern is that if I turn the truck around, I now have the frame weight of the truck plus the engine, transmission etc on the rear of the trailer and that will increase the sway.
 

chucky

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I see what you're saying. My concern is that if I turn the truck around, I now have the frame weight of the truck plus the engine, transmission etc on the rear of the trailer and that will increase the sway.
Have you tried it !
 

chucky

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The short trailers with axles doing all the work instead of having tounge weight to offset will feel different to pull ! You could always cut the trailer in half in front of the axles and add a few feet of floor to load weight further forward is the only way i see you changing the problem
 

Guyfang

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1680900717289.png

Back when I was contracting, maybe 2004 (?) I found one of there things in an empty Motor Pool. It was a door stop. Unit was down range. We were trying to clean the dump up before they got back. Unit was 1/7 SP/Arty. Took us a week to figure out what this thing was. At last the stay back Chief walked by and laughed. Said they called it the dog bone. He said what mostly happened to them was the Motor Daddy would hook the Motor Pool keys to it, so no one could put them in their pocket and take em home.
 
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