On 12/27/20 12:58 PM, mrspeed700 via groups.io wrote:
No they won't work,? electric brakes are self energizing and won't modulate like hydraulic brakes would
Yes they will. A drum trailer brake consists of a backing plate, two shoes and a cam attached to an arm with an electromagnet on the end. The electromagnet is positioned to touch a smooth part of the side of the drum.
When current is applied to the magnet, it is attracted to the moving drum. The drum movement causes the arm to slide on the drum, the cam rotates and the brakes begin to be applied.
The more current applied, the stronger the drag and thus more braking. If full 12 volts is applied, most trailer brakes (unless the trailer is overloaded) can skid the wheels.
Old fashioned brake controllers consisted of a cylinder which was spliced into the vehicle's hydraulic brake plumbing. This cylinder pushed against a spring. Also attached to the cylinder was an arm that swept over a wirewound resistor element. The harder the brakes were applied, the further the arm was moved and more current was applied to the trailer brakes.
Modern controllers are electronic and contain an accelerometer.
After installation, the vehicle is parked on a level surface. A little lever or knob on the side is used to zero the accelerometer so that it detects no change in motion due to gravity. The controller is typically mounted at a 45 deg upward angle so the driver can see the display and can move the manual application lever to apply braking without pressing the brake pedal.
in operation, when the vehicle brakes are applied, the accelerometer detects the deceleration and applies current to the brakes. The embedded processor contains algorithms to compensate for braking on a hill. It contains a separate algorithm to relax the trailer brakes when the vehicle starts to move from a stop downhill. On a downhill, the accelerometer would detect apparent braking and continuously apply the trailer brakes, preventing the tow vehicle from moving, absent the hill compensation algorithm.
That said, designing a controller to operate electric brakes as the primary brakes would be a very complex project, one that I would not want to take on. Only one aspect is providing proportional pedal resistance as the brakes area applied just like hydraulic brakes. Absent proportional resistance, as you apply the brakes, the g force will push your leg forward, applying more braking in a positive feedback loop, locking up the wheels and maybe even standing the car on its nose, depending on where the batteries are located.
When I had to sell my car, I had identified an automotive axle that would replace the stock one with much better brakes. Faded memory can't recall the car model. Someone else had identified an automotive brake assembly which could be bolted to the existing axle. Pinto lingers in my memory but I'm not sure.
Yet a third option is to buy a hotrodder's universal brake assembly from some place like Scummit and make or have made an adapter plate. That would probably be the overall simplest option.
John
NeonJohn
Dave Schwartz