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You have electric brakes. When you apply current to the magnets, they want to stick to the inside of the hub. The rotation of the wheel drags the magnet along, pulling on the lever holding the magnet, which causes the level to pivot and spread the shoes at the top of the hub to actually apply brakes. Surge brakes have a sliding connection to the hitch ball receiver connected to a hydraulic brake master cylinder. The brakes on the axles are standard hydraulic brakes. When you stop, the inertia of the trailer pushes against the master cylinder, generating hydrualic pressure to actuate the trailer brakes. Electric brakes have better control, and have the advantage that you can apply trailer brakes independently of the tow vehicle brakes. Surge brakes are common on rental trailers, since a lot of people don"t have electric brake controllers in their vehicles. You absolutely need a brake controller, as the amount of trailer braking is controlled by the current through the magnets. If you simply apply 12 volts to the magnets, it"ll lock the brakes (and probably overheat the magnets). A good electric brake controller like the Tekonsha Prodigy runs around $125. A decent one can be had for less than $100, and for occasional use a cheap one would probably be OK. I"ve seen them as low as $50 or so, but have no idea how well these work. The output of the brake controller goes to one wire on each of the magnets, and the other magnet wire is grounded (doesn"t matter which is which, brake magnets are not polarized). Don"t depend on the trailer frame for a ground for brakes, as a lot of them use the ball as the return path. Provide a ground wire back to the tow vehicle. There are several "standard" ways of wiring trailer connectors. The 7-pin RV type is the most common, and you can get them at Wally World or most any auto parts place. The 4-pin flat connector commonly found on small trailers don"t have enough pins to accomodate a brake connection. We pull an RV as well as utility trailers, & I can guarantee you that you don"t want to pull more than a couple thousand pounds without trailer brakes (plus its illegal in most states). I had a trailer brake fail (broken wire) on the way from California to Colorado with a car on a 7000 GVW flatbed a year or so ago. Even with a one-ton dually tow vehicle, it isn"t an experience I would want to repeat. Keith PS - most states also require a breakaway switch on a trailer that heavy. The breakaway switch connects a battery directly to the trailer brakes if the trailer separates from the tow vehicle. You can buy complete kits (switch, battery & cable) if the trailer doesn"t already have one.
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