[VAC] Re: Stromberg Brakes

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxxxx>]

I've not worked with a Stromberg hydraulic brake coupler but with
hydraulic cylinders on farm equipment, its always a pain to connect if
it is warmer than when the equipment was last disconnected, or if the
lift cylinder is holding machinery elevated. Because there's pressure in
the slave cylinder and lines. In motion hydraulics there is a tendency
for air to move out of the cylinders (running up to 2500 PSI, several
times brake line pressure) so there's no air cushion, and there's not a
severe problem if air is introduced at the coupler. So what I do is tap
the male coupler ball that seals the end of the coupler against the
tongue of the equipment to release hydraulic oil. Makes a mess though...

In a brake system air isn't wanted and there's not enough volume moved
to move the air to the pump where it can be vented to the reservoir.
Brakes aren't generally a circulating system.

Problems with coupling probably did annoy users of the Stromberg system
(along with severe braking system failures when couplers disconnected
while at speed) enough to cause the system to be abandoned. Agreed that
the current electric systems don't sample brake line pressure well, but
if the wire to the trailer breaks, it only kills the trailer brakes, not
the tow vehicle too.

Gerald J.