alangr Posted October 25, 2011 Share Posted October 25, 2011 Although related to DCC operation, I have a query about soldering which you guys may well be able to answer. To allow wagons to be detected using software (on DCC), a resistor needs to be installed across each wheelset for any wagon that is to be detected so that it pulls over (i.e. draws sufficient current to trigger) the detector circuitry. OK, I have installed a SMD reistor (with a lens, they are so small!), on the back of one wheel and connected between this wheel and the axle via the resistor with silver paint. Great, so far so good. I have then 'tinned ' the axle ready for a short wire to be soldered to the second wheel, thus completing the circuit for detection. What I cannot do is solder anything to the back of the second wheel. After looking around, I guess the wheels may be 'cast' and so of a metal that does not solder easily. Whatever, has anyone any useful dodge to get round this problem and allow soldering to wheels? Yes, I could use silver paint again to complete the circuit but this is not cheap and is tricky to use. Thanks Alan Link to post Share on other sites More sharing options...
kevindickerson Posted October 25, 2011 Share Posted October 25, 2011 I have then 'tinned ' the axle ready for a short wire to be soldered to the second wheel, thus completing the circuit for detection. What I cannot do is solder anything to the back of the second wheel. After looking around, I guess the wheels may be 'cast' and so of a metal that does not solder easily. Whatever, has anyone any useful dodge to get round this problem and allow soldering to wheels? Yes, I could use silver paint again to complete the circuit but this is not cheap and is tricky to use. Alan, It all depends upon the material used for the wheel, the majority of RTR stuff if I recall correctly are stainless steel* which is pretty much impossible to solder to with standard soldering equipment. Also you run the risk of melting the plastic insulator and end up with the wheel running out of true. The tried and tested method is using silver paint, I have heard from someone that it is possible to add graphite (ie from a pencil) to normal paint and this is sufficient to act as a detection resistor. The alternative I guess would be to add pickups to the backs of the wheels back to the bogie or chassis, then put the resistor there, it would also give you the opportunity to put tail lights on, but then this is probably just as costly and more time consuming than using the silver paint. Regards Kevin * I will quite happily be corrected Link to post Share on other sites More sharing options...
Tickplan Posted October 25, 2011 Share Posted October 25, 2011 If the axle is ordinary steel you could try soldering some springy wire onto the length of the axle with the other end simply sprung onto the cast/stainless/whatever metal wheel. I have done this the other way round i.e from rim to axle and was a tip from Chris at High Level Models. Good luck Bryan Link to post Share on other sites More sharing options...
JeffP Posted October 25, 2011 Share Posted October 25, 2011 Could you drill a small hole just less than the diameter of the resisitor lead/the wire you are using, between the wheel plastic centre and the metal bit, then force-fit the wire in? It would give enough contact, surely? Link to post Share on other sites More sharing options...
Edwin_m Posted October 25, 2011 Share Posted October 25, 2011 I don't think the silver paint is particularly expensive - I must have done at least 50 wheelsets and I haven't used up my first tiny vial of it yet - albeit these are N gauge and Farish wheelsets have one wheel connected to the axle so I don't have to worry about that end. If you can get it conducting at the resistor end then bridging across the plastic bush at the other end of the axle should be pretty straightforward. Link to post Share on other sites More sharing options...
alangr Posted October 29, 2011 Author Share Posted October 29, 2011 Thanks for all the replies. Kevin/Edwin_m: I did realise that simply continuing to use silver paint would (should) do the job; but having bought two vials and finding one had leaked and become solid before I had opened it and that the solvent used was extremely volatile, I wondered just how long the second vial would last. What silver paint do you use? Is is solvent or water based? I bought mine from Maplin and it is certainly solvent based! Bryan: the use of a springly wire sounds worth trying but I would be somewhat concerned about the possibility of intermittent contact. JeffP: Thanks; that is an idea and it might just be more reliable than a springy wire solution. So, guess I need to experiment - three things to try. Thanks again to all and to Andy at rmweb; the forum proves its use once again! Link to post Share on other sites More sharing options...
beeman Posted October 29, 2011 Share Posted October 29, 2011 At present fitting some 'MORE' coach lighting, Bachman wheels both on insulating bushes, so drilled thro one bush with .7mm drill at slight angle and press in a small brass pin so the wheel and axle are shorted, allowing pickup off the axle,so reducing drag against pickup on the wheel itself., You could do similar , drill each wheel and press in a brass pin for a 'solder tag' on the inside face of the wheel. you would really need a suitable bench drill though for small holes like this. It appears the Bachman wheels I am using are plated brass. Beeman Link to post Share on other sites More sharing options...
Edwin_m Posted October 29, 2011 Share Posted October 29, 2011 My silver paint came from Maplin too - not sure what it's based on but it doesn't smell as strongly as plastic weld or MEK or IPA or any of the other solvents I've used. Even after a short period of non-use the silver sinks to the bottom of the liquid but a good shake seems to restore it. Probably a good idea to make sure it stays upright, as if the silver bit is no longer covered by the liquid then it will probably go solid. The top of the vial is kind of hollow so after shaking some of the paint collects in it. Instead of using a brush I apply it by dipping into the top with the lead of a spare resistor, or anything similar that happens to be knocking around on the bench, as the quantity needed is very small. I think friction might also be an issue with options that involve pickups rubbing on the wheels, especially if you fit every vehicle in a long train. Link to post Share on other sites More sharing options...
alangr Posted October 31, 2011 Author Share Posted October 31, 2011 Yes, I think I will try the small hjole approach; thanks Beeman. I don't really like the idea of pickups and you are quite right that apart from possible contact issues, the friction build up for a long train could be appreciable. Edwin_m: I had noticed that the silver paint I was using settles out quite quickly and does need a very good shake before using. But it would be good if the solvent was available to aid in keeping the original vial in use (as it will thicken with evaporation, I guess). Thanks Link to post Share on other sites More sharing options...
alangr Posted December 10, 2011 Author Share Posted December 10, 2011 Just in case anyone is interested, I have been in touch with the makers of the silver paint sold by Maplin (Bondloc) who were very helpful. With no guarantee of success, acetone was suggested as a possible solvent 'thinner'. This seems to have worked for me. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.