vacuum brakes 1977 landyacht

[John]

Craig,

That was an awesome class on the Vacuum boost trailer brakes! Overall, how do they compare to the "standard" electric brakes?

Not that I'm going to change, just interested in braking differences.

Tks-John

[John]

My trailer brake line is tied into a 30A fuse. I realize that if this fuse blew/opened, I'd be without trailer brakes.

My question: If I had a surge that would blow/open the 30A fuse, wouldn't that same surge in higher enough also to damage the brake controller, making it inoperatable?

I think I'd rather replace a blown 30A fuse, which I carry extra's of, than to burn out the controller, which means I won't have any trailer brake controls until I replaced the controller.

Please correct me if my thinking is wrong.

John

[Action]

With out circuit protection (breaker/fuse) what would happen to that circuit should it ground out as by means the insulation chafing or if the wire got pinched. I would think a fire could result given the size of the wire in the photo.

With a resettable breaker at least the circuit has some protection and can be reset once the issue has been resolved. If the brake magnets have worn out* and trip the breaker at least there is some brake action from the tow vehicle. Certainally not enough. However, if there was a fire or even an extremely over heated brake circiut wire that melted insulation and other circuits, one may not have brakes anyway.

Just a Q.

*Checking the running gear at least once a year would seem to be prudent)

>>>>>>>>>>>>>Action

[davidz71]

Andy,
I only followed the installation manual that came in the Energize III brake controller you sold me.

John,
The disc brakes are really good if everything is working properly. I'm happy with mine and hear that they will outstop the electric drum brakes every time.

[FrankR]

Craig, I want to say I think you have done a very nice job. Your explaination is good. Your pictures are good. Your ideas are good. Thanks. On several Airstreams with vacuum disc brakes, I've made a few changes. I went to a auto/truck salvage yard and got a 12 volt vacuum pump. These pumps are used with all diesel engines and vehicles with turbos. The pumps are reasonable and every salvege yard has units. These pumps can be concealed under trailer framework in a convenient place. Power for pump can be provided by charge line from tow vehicle. With this pump, not lines are required from tow vehicle. All vacuum lines maybe constructed with big rig plastic/nylon line. It is very strong, works well with compression fittings, not real expensive, available in many sizes and found everywhere. Frank

[FrankR]

Craig, As mentioned earlier, the words and pics are great. Just a small observation. The circuit breakers used are not real wire/circuit protection. These devices will keep resetting forever. Even after the fire is really burning, the automatic resetting breaker will reset until the battery voltage is gone.
So I guess Andy should not have any fear of no brakes, with this setup. The best circuit breakers for this protection are the MANUAL reset type or one time fuses.
Yep, I know the auto makers use lots of these devices. I repair lots of electrical problems...... Frank

[John]

Craig,

It's cool that your trailer has disc brakes!

Sounds like a nice set-up!

John

[74Argosy24MH]

If you have a short that will blow a 30 amp fuse or breaker, it is a dead short. Electricity takes the path of least resistance, there will not be enough power at the magnets to operate the brakes anyway.

John

[davidz71]

Frank,
I remember a picture you posted showing the vacuum pump mounted in the basepan where the original powerbooster was located. It seemed like a clean installation and something a diesel tow vehicle could definately use. If my system ever failed and I could not find parts, I would definately go the route you have chosen. Also, point well taken on the circuit breakers and I now understand what Andy was trying to get me to understand. Sometimes I'm a little thick in the skull region.

[FrankR]

Craig, Did I mention you do nice work.
Your memory of past disc brake pics may be a little confused. I'm an old f**t with a failing memory.
The past picture was of a different type master cylinder to operate disc brakes. This method uses a electric motor to operate a hydraulic cylinder that applies the brakes. There is no vacuum needed. The electric motor system uses the standard brake controller.
My post about the electric vacuum pump mounted on trailer was for disc brake systems who continue to use the factory master cylinder system. Sorry for confusion. Disc brakes are the best.....

[acme]

Craig
i am finaly back to the trailer sure is fun to see it again! When I hook up the vacume line to the trailer I get the sound of air releasing, but no brakes. When I open a bleader valve no fluid or preasure. I tried calling inland RV. The woman who answered was very pleasant, she sugested I call Andy there tomorow. I am guessing it might be seals? I f anyone has any thougts I would apreciate them. Thanks again for all your help.

Tim

[Inland RV Center, In]

Sounds like the sync valve has gone bad. We can overhaul it for you.

Andy

inlandrv.com
airstreamparts.com
airstreamcandy.com

[davidz71]

Tim,
Andy knows his disc brake systems so he's probably right. Have you ordered a service manual yet from Helen Davis or could I help you with some xerox copies of schematic drawings?

[davidz71]

Frank,
You are correct and now I'm straightened out about the picture showing the electric motor and master cylinder sitting in the pan where all the guts from the old disc brake booster/stuff use to sit. I just figured that you were able to fit in a small vacuum pump unit next to a small master cylinder but that would definately would take up a little more space. Thanks for keeping me straight.