When I bought my 751 Log Loader, I noticed that the internal wiring had been changed to permit it to run on a single-button controller. The only problem is it's requirement for a transformer with a lot of wattage, since two coils are being energized at the same time at some point. I bought a 2-button controller and changed the internal wiring on the Log Loader so I believe it pretty much runs as the factory intended - back in the day. Since my 2-button controller may be wired differently from yours, I am going to narrate this post for you to see the technique I used. My narrative is written using American Flyer terminology.
By observation or by the use of a continuity tester, either determine a common wire that will power both buttons in the controller or make a lead that splits and attaches to one of each of the pair of clips and to the fixed post of your transformer. When either the red or the green button is pressed, power is routed. With this particular accessory, a fixed post lead is routed - rather than a base post lead being routed. The Log Loader is wired with a base post wire connected to the base post on the transformer all of the time.
Take a motor lead that does not connect to the traveler clip near the flywheel of the Log Loader. Attach it to the wire coming out of the controller from the red button. When the red button is pressed on the controller, power will be routed to the motor via the fixed post of the transformer. The traveler clip is on the side nearest the flywheel and has a delicately-bent brass or copper strip that acts as a spring. When the raised tang on the flywheel presses the spring clip together, a mechanical/electrical connection is made. The lead from the wire on the rear side of the spring clip is the motor lead wire that goes straight to the base post of the transformer. The other side of the spring clip now also becomes a base post wire, but only when the spring clip is closed. That transient and intermittent base post wire goes to one of the wires coming out of the coil on the underside of the Log Loader. It is the coil that powers the lift, raising a log up to the cradle. The other wire coming out of the coil goes to the green button of the controller and when the flywheel is in it's proper position and the spring clip is closed and the cradle is ready to accept a log, stop pressing the red button and press the green button instead. The green button powers up the coil to lift a log to the cradle. Once the cradle is loaded, stop pressing the green button and press the red button again to move the log to the car on the track that is ready to accept a log. Continue pressing the red button until the log is dropped and the cradle is back down and ready to accept another log. Continue the process until you are happy. lol
OBTW: I made sure that the spring clip I mentioned was bent for a "hair trigger" contact. I felt it made everything work the best it could - given the rather clever, yet primitive design of the accessory.