What is the best Tow/Brake set up for a Towed Vehicle?

Daveinet wrote:

tropical36 wrote:
This so intrigued me, that I did some further research and found this, so I would like to hear more on how this could have possibly happened and maybe some others have had a similar experience.

"Since the tubes in a receiver fit tightly, there is only a shear load on the pin, with Very minimal (neglectable) bending load. If the jaws on the female part of the wagon hitch are 3" apart, and the receiver hitch is 1" thick, there is 2" of bending moment (or leverage) on the hitch pin. A pin or bolt will handle a ridiculous amount in a "shear only" setting. Especially "dual shear" where the load effectively has to shear the pin in 2 places for a failure (such as the receiver tube).
For example : a 5/8 pin: (.3125)^2 X 3.14= .30662 in^2 area of pin. If the steel is 75KSI material (1045 cold drawn), then each shear instance will theoretically handle 23000 pounds of shear load. Since the load is being spread over 2 instances (dual shear) it should hold 46,000 pounds before shearing. This all depends on the alloy of the steel being used in the pin of course. Hard to put 46K of direct drawbar load on a pickup. Not saying impossible, but hard to do."

After reading your post, makes me wonder if the tubes were not fully extended, which would allow it to get a running start.

Possibly and maybe if we could get sjholt to chime back in here, we might have a little more insight, as to exactly what happened with his experience. Certainly wouldn't want something like that happening with me.

tropical36 wrote:
This so intrigued me, that I did some further research and found this, so I would like to hear more on how this could have possibly happened and maybe some others have had a similar experience.

"Since the tubes in a receiver fit tightly, there is only a shear load on the pin, with Very minimal (neglectable) bending load. If the jaws on the female part of the wagon hitch are 3" apart, and the receiver hitch is 1" thick, there is 2" of bending moment (or leverage) on the hitch pin. A pin or bolt will handle a ridiculous amount in a "shear only" setting. Especially "dual shear" where the load effectively has to shear the pin in 2 places for a failure (such as the receiver tube).
For example : a 5/8 pin: (.3125)^2 X 3.14= .30662 in^2 area of pin. If the steel is 75KSI material (1045 cold drawn), then each shear instance will theoretically handle 23000 pounds of shear load. Since the load is being spread over 2 instances (dual shear) it should hold 46,000 pounds before shearing. This all depends on the alloy of the steel being used in the pin of course. Hard to put 46K of direct drawbar load on a pickup. Not saying impossible, but hard to do."

After reading your post, makes me wonder if the tubes were not fully extended, which would allow it to get a running start.

While it might not work in every case (depends on length of safety chains/cables), I learned years ago to criss-cross the safety chains under the hitch. That will often cradle the hitch if it pulls loose from the tow vehicle.

tropical36 wrote:

sjholt wrote:
The ReadyBrake break away works. I found that out when I broke a hitch pin.

These pins have been known to break and have often wondered about that... :E
I mean this thing actually sheared off both sides of the pin?

This so intrigued me, that I did some further research and found this, so I would like to hear more on how this could have possibly happened and maybe some others have had a similar experience.

"Since the tubes in a receiver fit tightly, there is only a shear load on the pin, with Very minimal (neglectable) bending load. If the jaws on the female part of the wagon hitch are 3" apart, and the receiver hitch is 1" thick, there is 2" of bending moment (or leverage) on the hitch pin. A pin or bolt will handle a ridiculous amount in a "shear only" setting. Especially "dual shear" where the load effectively has to shear the pin in 2 places for a failure (such as the receiver tube).
For example : a 5/8 pin: (.3125)^2 X 3.14= .30662 in^2 area of pin. If the steel is 75KSI material (1045 cold drawn), then each shear instance will theoretically handle 23000 pounds of shear load. Since the load is being spread over 2 instances (dual shear) it should hold 46,000 pounds before shearing. This all depends on the alloy of the steel being used in the pin of course. Hard to put 46K of direct drawbar load on a pickup. Not saying impossible, but hard to do."

two-niner wrote:
A shorten version. Unified braking, Roadmaster (Sterling) tow bar, breakaway cables. On the bridge between Bullhead City, AZ and Laughlin, NV.

Pin on hitch breaks (verified), towed brakes come on full, breakaway cables hold, Tow bar catches on concrete and like a pole vaulter does a 180 degree and goes thru toad a/c system and into engine oil pan. A lot of damage. USAA pays for towed repairs. Roadmaster gives new tow bar (Rick).

Was acceleratoring rapidly and in 2nd gear when this happened. Too late by the time stopped.

For me personally, I wonder if the two ten thousand lbs breakaway cables actually broke, if there would have been a lot less damage and the tow (06 Grand Vitara) would just be sitting there unharmed. The Unified worked as advertised.

Kerry (USAA did NOT raise our premiums and went after Roadmaster)

You're saying not to use any safety cables and just rely on the breakaway, instead of attempting to drag the toad with the brakes on?
Makes sense to me and there doesn't seem to be much consideration for what happens to your stuff, just as long as it doesn't go elsewhere.
Still hate the thought of the pin breaking and one must wonder how good and dependable they are, overall. Just hope those Chinese know how to make them, as I wouldn't know how to test it without some real sophisticated equipment.
What is the rating on these pins and do they make them for both 5000 and 10000 lb receivers? I can't remember what the rating was, on the one I bought.

mfinnerty wrote:
SMI X2

Me too ;)

A shorten version. Unified braking, Roadmaster (Sterling) tow bar, breakaway cables. On the bridge between Bullhead City, AZ and Laughlin, NV.

Pin on hitch breaks (verified), towed brakes come on full, breakaway cables hold, Tow bar catches on concrete and like a pole vaulter does a 180 degree and goes thru toad a/c system and into engine oil pan. A lot of damage. USAA pays for towed repairs. Roadmaster gives new tow bar (Rick).

Was acceleratoring rapidly and in 2nd gear when this happened. Too late by the time stopped.

For me personally, I wonder if the two ten thousand lbs breakaway cables actually broke, if there would have been a lot less damage and the tow (06 Grand Vitara) would just be sitting there unharmed. The Unified worked as advertised.

Kerry (USAA did NOT raise our premiums and went after Roadmaster)

I have had roadmaster system, M&G system and airforce one system. all systems had breakaway systems and all three systems worked great. I liked the last two systems best because all I had to connect to car at time of use was air line and lanyard for breakaway.took less than a min to hook car to M/H

I have just installed a READY BRAKE system on my m/h and towing a4350lb.srx.have towd it approx. 800 miles and seems to work grate. no drag down hills dash lite lets you know when the brake is on.

sjholt wrote:
The ReadyBrake break away works. I found that out when I broke a hitch pin.

These pins have been known to break and have often wondered about that... :E
I mean this thing actually sheared off both sides of the pin?