cliff park Posted April 1, 2015 Share Posted April 1, 2015 Some time ago I acquired seven servos, they were being thrown away. I put them to one side until recently, and then thought of a use for one. I built a simple 555 timer based servo controller, only to find that six of the servos didn't work properly anyway. A couple of them would only go one way, three would hunt and not stay still, but all of them had working motors. Then I remembered that someone had used them without the electronics and I had a little play. Now it should be said that although my uncoupler idea was made using hacked servos this would work equally well, if not better, using normal servo controls. So, the uncoupler. I had working servos, sort of, and wondered if I could use one to make an uncoupler for good old fashioned Hornby/Triang/Mainline etc couplings. Starting with a basic uncoupling ramp the obvious problem is to make it go up and down. I played with linkages and bell cranks and then it struck me:- a cam. A cam is perfect at turning rotary motion into linear motion. http://youtu.be/ounJY5V1tGc I made the cam from 6mm MDF and the ramp and follower from brass sheet and rod. Note that all pictures are of my test version, not as yet on my layout. The switch is mounted on the bracket just for convenience. By the way the switch is a 2 pole change over with centre off. Once the cam has pushed the ramp up it will stay there with the power switched off. http://youtu.be/BKu30HhzTGg By the way the small cam follower roller is one pinched from a microswitch, without it the cam pushed the plate sideways so it wouldn't slide up easily. Hope this is of interest. If anybody wants to have a go and is worried about setting out the cam I will do another post PS Obviously I haven't painted the brass, or it could have a plasticard or similar top stuck on. Link to post Share on other sites More sharing options...
cliff park Posted April 2, 2015 Author Share Posted April 2, 2015 Couple of points I missed from the op. Servo is running on 1.5 Volts. Any higher and it seems a bit fast, even at this voltage it has plenty of torque. The two upright 'posts' are 4mm brass rod, threaded by me. I choose this method as I could easily solder them to the brass plate, and the length of the threaded section gave me plenty of vertical adjustment. These could probably be replaced by csk headed bolts, soldered to the plate. I wanted a smooth surface on top, so didn't want to drill it. Most of the fixings have slots to further ease adjustments. Link to post Share on other sites More sharing options...
AlbertTheFrog Posted April 2, 2015 Share Posted April 2, 2015 Looks useful, Cliff. I'm looking for a way to split rakes of wagons so the passive uncouplers won't do the trick. Out of interest, is the length of the brass plate important? I'd like to keep the uncouplers as short as possible. Link to post Share on other sites More sharing options...
cliff park Posted April 2, 2015 Author Share Posted April 2, 2015 It just needs to be long enough to cover two vertical dropper bits, plus a bit at each end for the slope. If it is too short it is very difficult to position the vehicles accurately. The longer the ramp , the less critical the position where uncoupling can take place. Link to post Share on other sites More sharing options...
RMweb Gold Stubby47 Posted April 2, 2015 RMweb Gold Share Posted April 2, 2015 Further thoughts ( other people's ideas ). If you mounted the cam lower and fitted the roller follower to the end of a square brass rod inside a square brass tube, you'd only need one support for the upper plate. If you made the upper plate out of clear plastic it would be less obtrusive. Stu Link to post Share on other sites More sharing options...
cliff park Posted April 2, 2015 Author Share Posted April 2, 2015 The problem with one 'riser' is keeping it vertical and stopping it twisting. I did experiment and it gets tricky. If you use a single, square riser you need a bit of play to allow it to easily rise and fall without catching, but then even a small twist means that It can finish up at an angle across the track, and not come down cleanly. I did consider something like telescopic plastic tube/rod. The tube fixed in the baseboard and the rod as the riser. I did, however, feel that the weight of the brass would help it all fall. If you go down the plastic road you might need a spring to pull it all down. Try it, and let us all know !! Link to post Share on other sites More sharing options...
cliff park Posted April 16, 2015 Author Share Posted April 16, 2015 I've just had a random thought. The same principle could be used to operate signals. With a counterweight to restore it, a slow speed servo, and if you made a cam like my sketch, excuse crude graphics, you could build in a bounce or two. Link to post Share on other sites More sharing options...
bigal10 Posted June 6, 2015 Share Posted June 6, 2015 I assume Cliff, you're not using DCC? However you and others may be interested in my DCC approach to this uncoupling ramp idea using servos in DCC.... Have a look at this thread, Under DCC Topics, "Uncoupler DCC - 00 gauge" started by model-trains on 4th Feb 2014. I think the original poster was looking for on-board decoupling from the Loco-Decoder, but all varieties are of interest to me. I posted photos and finally a video of the ramp in action Regards, Alan Link to post Share on other sites More sharing options...
Dazzler Fan Posted June 7, 2015 Share Posted June 7, 2015 +I think the brass plate may cause electrical shorts on the underside of locos Link to post Share on other sites More sharing options...
cliff park Posted June 7, 2015 Author Share Posted June 7, 2015 I don't think I have ever seen electrical connections or wires on the underside of locos. I chose brass so that I could solder the 'push rods' to the plate, this could all be plastic. The point of the post was to show a novel way, to me, of operating an uncoupler using a servo. I did have issues with the width of the plate, too narrow and it risked missing the couplings, too wide and it catches on brake gear etc on the underside of trucks and locos. Link to post Share on other sites More sharing options...
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