I have had a few cases where I needed to connect to a circuit board but keep the surface flat.  What I do is to drill a hole through the board and insert a brass or copper rod (or tube, if I need to tap the hole) of exactly the same diameter.  After soldering, I can file the surface flat.  It's not a very strong joint because of the nature of butt-soldering to think copper, but the thickness of the substrate offers some mechanical strength, and the joint is usually for electrical rather than mechanical purposes anyway.

Leaf springs certainly work, but I'd think this would be the perfect place for a springloaded straight pin style pickup, I saw it years ago on a tender truck.

You start the a sewing pin, a pair of small washers, a kadee knuckly spring, and a tube.  You'd assemble it so that the head of the pin faces the track, then the washer keeps the spring between the head and the tube body, and then you bring the pin back and bend it over at a 45-45 degree U.

It's a slick little system, I'll be using them on tender pickup s when I get around to that sort of business agian!

Ken,

That's another way of doing. I did just solder the copper strand to the ring and filed the solder joint down. The pin had no trouble traversing the slight rise as it went over the solder joint.

@ Benny,

Good idea for smaller spaces for picking up power from the wheel. The coupler spring isn't powerful enough to do what I need it to do. Might use your method for picking power off the trucks though.

Bernd

Having had 55 years experience of having model locos with wiper pick up from wheels, I'll offer that as one of the major causes of limiting smooth starting and stopping and slow running. The greater the pick up wiper pressure, the more friction is put onto the transmission.

IMO, FWIW, The best thing that ever happened to US model railroading was the split chassis and axle bearing  pick-up method.  I'm not criticizing using it for the crane rotation scheme, as it's function and relative motor power/gearing is quite different.

Hi Bernd,

I'm overwhelmed that you machined these contacts!

I also considered the PC board rings and tossed it out because I will not use straight copper anymore for electromechanical contacts because copper oxide always forms and is much less conductive than copper, eventually forming bad connections. Just think of having to disassemble your crane to clean the rings!

The wheel contact wires are phosphor bronze-- thinner than many people use, but used in pairs because even if one bounces due to mechanical movement the other is likely to keep contact. This "bifurcated" contact technique is used commonly in precision relays and motors. The bottom ring in the crane was also phosphor bronze ,005 sheet (or .003 or .008) hand cut. It survives with reliable contact much better. I used copper tape for the inside well ring only because it was easy and I couldn't find an easy alternative. Glued .003 precisely cut phosphor bronze sheet would also work-- but the cut is tricky to get precise. I think the best method would be dual pogo pins (gold plated) on a single lower ring, and the second contact made through the motor axle/housing. I used the inner copper ring to simply show an alternative. Do you really need two rings on the PC board?

Stay with it!

Best Regards,

Geoff Bunza

Hi Geoff,

I'm overwhelmed that you machined these contacts!

As I've said before I'm a dyed in the wool do - it - your selfer. I'd probably make the miniature motors and  gears if I had the equipment. That's just me. I also like to show that there alternatives to some items.

As far as the ring being copper. I have a piece of phosphor bronze and it's has oxidized quite a bit. I always remember the guys with the trolley lines cleaning their phosphor bronze wires that the trolley ran on. It may not oxidize as fast a s copper but it does. I'm going to keep with the copper ring and see what happens.

 The wheel contact wires are phosphor bronze-- thinner than many people use, but used in pairs because even if one bounces due to mechanical movement the other is likely to keep contact.

I take it you are talking about trucks on the crane. Why would you be concerned about bounce? The crane will not be working until it's positioned to do work. The only reason I would think of wiper bounce being a concern would be if the sound system was on in the crane while being pulled in a train.

The reason for two rings is for both plus and minus to be brought up to the decoder. Instead of having a contact on the wall of the ring.

One more thought of the two contact rings. If oxide becomes an issue using copper clad board I could then sweat solder on a layer of .003" or .006" thick phosphor bronze. Come to think of it I may just do that now before I glue in the ring.

I have an idea for picking up power from the wheel set, but first I need to purchase the trucks to see if it will be possible. I got the idea from Ring Engineering's EOT device. They claim it's close to friction free. I think I now why. I'll get into that when I get a set of trucks.

Thanks for the encouragement to stay with it. I have to now since I've made it available to over 60,000 readers. May take a bit longer than some like, but it'll get done as long as there is interest for it.

Regards,

Bernd

Oxidization is always a factor to consider.  I wonder if using some NO-OX-ID on the surfaces would provide any lasting benefits?

I made a set of contacts using strips of copper clad board and phosphor bronze wire.  I sweated some solder onto the copper as you mentioned, Bernd.  I use the contacts to allow the removal of a two story buildings exterior walls and roof from the foundation and interior walls/floors.  It passes power to the second floor and exterior shell for lights and signage to be mounted on the outside walls.  So far I I have not had issues with oxidation causing a loss of power.  Of course nothing is revolving and it's just powering lights, not a decoder and motors.

I received the cab rotation motor from Pololu today.  Really quick shipping I thought.  I'll definitely keep them in mind for future animation projects.  Thanks for directing me there!

Do keep going with the crane project!  I can wait patiently to see what you do next, but I would like to see how it all comes out in the end.

Not to fly off topic, but since Geoff mentioned machining...

I visited my local Sherline dealer last Friday and got to see and fondle the lathe and mill a bit.  I am really impressed with the quality of everything Sherline makes.  Rick, the proprietor of Dixon Forge, is a fantastic guy and a great modeler too.  He's building a scale machine shop that will all be powered by a scale steam engine and belt system.  Everything is going to operate!  Very cool.  I could have spent the entire day with him if I had the time.  Next time I visit him he says we can play with the tools some more.  I can't wait!

Looking forward to more on the crane when you are ready.

Two options:

One, you could gold plate the contacts.  Caswell Plating has kits for as little as $67.99

http://www.caswellplating.com/electroplating-anodizing/brush-plating-products/plug-n-plate-kits/plug-n-plate-gold-kit.html

The other option, a good bit cheaper, would be to use something like No-Ox.  It might have a side benefit of lubricating things nicely.

I always wanted to try plating. Do you have experience plating something and using it as a sliding contact surface?

No-Ox is great but only delays, and doesn;t solve the oxidation problem.

Best Regards,

Geoff

Common practice is to use trucks with metal side frames,and wheels sets with only one wheel insulated. (e.g.Kadees, but with NWSL or other similar wheels). Then fit the the wheel sets reversed in the second truck. That makes one truck live to the LH rail and one truck live to the RH rail -. You can then take power from the metal bolster bolts of each truck. Just make sure you have an insulating car floor first!.

If you can't get metal trucks in the pattern you want, there are shallow brass Pin-point bearing cups available that are designed to fit into plastic side frames.  Or in your case, you can likely machine those up yourself.

http://www.proto87.com/model-railroad-truck-spare-parts.html