I searched through Model Railroader using some keywords. Maybe you can find something in them.
Search 1 using 'control' for keyword.
Search 2 using 'brake' for keyword.
Search 3 using 'momentum' for keyword.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
It might be helpful if you could narrow down the time frame a bit. Looking at the MR magazine index a lot of throttle articles come up, but what they actually contain would require looking at the magazines. Some of us have, or have access to, the old magazines, but searching through 10 year's worth would take a big effort.
I think a bigger question would be can you come up with the parts required to make the throttle. I suspect that many of the transistors that were available in the 70's are obsolete and no longer available.
MR, January 1986. "Build an Inexpensive Walk-Around Throttle."
The controller had five buttons. FWD, REV, INC, DEC, and Emergency Stop. You could unplug the controller and the train would continue to run while you walked to another location and plugged it back in. The longer you held down the INC or DEC buttons, the faster or slower the train would go with momentum effects being applied. The FWD / REV buttons would control a relay that would reverse the output polarity and thus the direction.
I built three of them and used them on my last layout before changing over to DCC. The article had a couple of errors in it that subsequent issues had corrections in. I used standard telephone plugs and receptacles for the controller cables to plug in to.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.