Ted,
Yes, that would be full application current draw. (As if you had connected
the brake magnet directly to a 12 volt battery) The brake controller in your
tow vehicle varies the voltage available to the magnets, which regulates the
amount of braking force.
I would not wire the brakes in series because losing one magnet means losing
the brakes on that axle. Trailers are not normally built with an
over-abundance of brake capacity. Losing brakes on one axle could be very
hazardous. The original question concerned a 4 horse trailer. 10" brakes a
usually rated at 2500 lbs./axle brake capacity and 12" brakes are usually
3500 lbs./axle. Four horses would weigh what? 5000 lbs.? Add to that the
weight of the trailer, tack, feed, and personal gear and it's probably at
the maximum of the brake system capacity. I wouldn't want to take a chance
of losing half my brakes. Electric brake magnets are designed to rub on the
inside face of the drum. Eventually, the magnet wears down and the windings
are exposed. They short against the drum and the brake stops working. A
severe short can cause all 4 brakes to quit working, especially if it is in
the magnet closest to the point where the brake power wire meets the front
axle. Path of least resistance.
I spent five years working on tow vehicle wiring and trailer electric
brakes. I've seen what can happen when trailer brakes are lost and I
wouldn't recommend a wiring approach that increases the chance of that.
John
-----Original Message-----
From: Ted Hintopoulos [mailto:hint@northnet.org]
Sent: Thursday, August 31, 2000 7:27 AM
To: mil-veh@skylee.com
Subject: Re: [MV] Towing 12 v. trailer with 24 v. M35
>Electric Brakes on average can draw arounf 3 amps each. So if you have
>brakes on one axle you will draw around 6 amps. My Trail King lowboy draws
>around 12 amps total for dual axles and uses a 20 amp fuse......
Is that full application current draw? In other words, there is no
in-between,
either they are full on or not.
>For the brakes, how about wiring the brakes in series pairs and powering
them
>with 24 volts?
This would be a good solution. It assumes that the coils in each wheel are
not internally grounded. I've not had to take a trailer w/ electric brakes
apart
to make that determination. Also, if you loose one coil in the series
setup, you loose
both series connected brakes. But I think that to can be solved.
On a two axle system, wiring an axle 24 Volt would be fine. If you loose a
coil on
one axle, you still have the remainder. Just like modern hydralic brakes
with the dual master cylinder.
Getting back to the original note that started this dialog,
my understanding was that the lister, wanted to construct something
simple, and RELIABLE, so if he needed to tow someone elses civi trailer,
he can without redoing anything on that rig. Just plug and tow.
A universal adapter.
That would interest me as well.
Ted.
MVPA 1705
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This archive was generated by hypermail 2b29 : Sat Sep 02 2000 - 09:32:39 PDT