Questions about M720 and brakes

[asajay]

Hey Coug,
I realize this is a really old posting, but I just found it today as I was (again) searching for anyone who had done an in-truck electric brake controller to air system.

What was your final solution?

For what it's worth, and I've forgotten to post it, I did an electric to hydraulic conversion on an M720 shelter dolly around 2020 when I picked up another TSC-60 system already mounted on a dolly. In my case, I purchased a Transtar electric to hydrualic system and the 7-way connector. I mounted the hydraulic box on the front half of the dolly. I had to do some creative replacement and management of the hydraulic lines to the wheels but in the end it all worked out great is is totally reverisble. One caveat though; I only did this to the front half, I did not do anything with the back half.

This setup gave me sufficient braking with a 1994 Ford F250 7.3L Powerstroke. Once I had the controller adjusted properly I could "feel" the tow braking just before the truck.

I would like to keep the original air-over-hydraulic system but don't have a good read on how to set that up in the truck to accomplish it. I think the last time I researched this it was about how to properly regulate the right amount of air using the electric brake controller. I was on a crunch to get this equipment moved so I went the cheapeast and easiest route.

I'm interested to know what you did.

Thank you,
Asa Jay

 

[Coug]

Hey Coug,
I realize this is a really old posting, but I just found it today as I was (again) searching for anyone who had done an in-truck electric brake controller to air system.

What was your final solution?

For what it's worth, and I've forgotten to post it, I did an electric to hydraulic conversion on an M720 shelter dolly around 2020 when I picked up another TSC-60 system already mounted on a dolly. In my case, I purchased a Transtar electric to hydrualic system and the 7-way connector. I mounted the hydraulic box on the front half of the dolly. I had to do some creative replacement and management of the hydraulic lines to the wheels but in the end it all worked out great is is totally reverisble. One caveat though; I only did this to the front half, I did not do anything with the back half.

This setup gave me sufficient braking with a 1994 Ford F250 7.3L Powerstroke. Once I had the controller adjusted properly I could "feel" the tow braking just before the truck.

I would like to keep the original air-over-hydraulic system but don't have a good read on how to set that up in the truck to accomplish it. I think the last time I researched this it was about how to properly regulate the right amount of air using the electric brake controller. I was on a crunch to get this equipment moved so I went the cheapeast and easiest route.

I'm interested to know what you did.

Thank you,
Asa Jay

I ended up not doing anything to it yet.

Nobody around here has a shelter to use with it that I could find for what I would consider a reasonable price, and I've been spending my limited funds on other projects that will actually get used more than once or twice a year.

Glad to hear that it wasn't too difficult to install an electric over hydraulic system to operate the brakes.

 

[asajay]

Looking back at my photos, I never did properly document what I did. I really only have one photo:


This is the front half of the shelter dolly, or as I got to know them when I was in the military, a "mobilizer." I apologize for the crudeness of the wiring install. This was taken after I got it home. I had to get it and the shelter it was attached to out of the yard it was in and didn't have time to make it pretty before leaving.

You can see where I mounted the Hydrastar on the frame rail between the uprights. From the top of it runs a normal auto parts store sourced flexible line with hard ends. It's a bit too long (hence the loop) but again I didn't have a lot of time and got what the parts store had in stock. The connections from the original master cylinder attached to the air-over-hydraulic actuator have been removed and attached to a T-fitting to send fluid to the left and right wheel cylinders.

A breakaway battery has been mounted to the drawbar underneath the spare tire. Wiring goes to a 7-pin (blade) RV connector and plugs into my truck. It's all controlled by an older electric brake controller. It all works, but only to the front wheels. To get brakes on the rear would require another Hydrastar unit and wiring to the back over the top of the shelter.

8,000 pounds total towed load. 6,000 for the shelter plus installed equipment, and 2,000 for the mobilizer. I had no issues braking, stopping and starting.

Well... not true when I first left the yard. The right -rear- wheel was locking up. So there I was on the side of the road, jacking up the rear half, taking the wheel and hub off, removing all the brake bits and putting the hub and wheel back on. There was no hydraulic action to the rears so it was of no concern to leave the brake shoes out. After that it towed home fine with about 97 degrees F at each corner each time I stopped and checked with a handheld IR gun.

Overall I think I spent between $800 and $900 after all the little bits and pieces, like brake hoses at the wheels needing replaced, split wire loom, etc. Yes it was a bit expensive.

The first mobilizer I got from auction (GovPlanet) out of Lakewood as I recall (before they re-contracted and moved). I got that one for $400 after all the state, local and federal fees. I've not added the Hydrastar to that one yet. I have two of these shelters now, each nearly complete AN/TSC-60(V)9 HF Communications systems. I need to service both sets of mobilizers for various things including new tires on one.

In summary, I think the Hydrastar system (or one similar) is probably the easiest ticket as long as you can find brake parts for the original backing plates, hubs and drums. And it's reversible... not that anyone might want to send this back to original, unless some museum offers me a really great price.

If you decide you might not want that M720 you have, I might want to talk to you about it. Just keep it in the back of your mind and PM me in the future.

Asa Jay