Forum article

Prepared by Tommy Day Originator Mike Green

mike green 3125 - Jan 17, 2018 at 5:47 PM Can anybody tell me what flux I need to use to solder between aluminium and steel. I need to bridge the insulation on wheel sets as both wheels are insulated and I want to use them for pickup, one side of the two bogies on coaches for LED lights.
Mike

DLOS - Jan 17, 2018 at 8:07 PM
Mike, Hah, not such a simple request. There are special fluxes for steel, but I use Bakers Fluid when I have to 'tin' steel. For the aluminium, see here at 'http://www.cupalloys.co.uk/soft-solder-fluxes/'. But, in my experience this is not as straight forward as soldering copper alloys. Hope this helps. David

R.Comerford21612 - Jan 17, 2018 at 8:25 PM
How about using a conductive paint across the join? If the loco is not using a motor any more current hungry than a Mashima 1833 the paint should handle the current.. Just a thought!
cheers
Bob

Morgan17782 - Jan 17, 2018 at 8:48 PM
Hi Mike
I assume that it is rim insulation. When I used to short out Romford 00 wheels many years ago I used brass tacks. Find some with a diameter a bit larger than the insulation thickness, drill a hole a few thou smaller than the tack, support the wheel well and press the tack through, cut off ends and clean up. Hard nickel or brass wire would also do.
Hope this makes sense.
Regards
Allen Morgan

Round18052 - Jan 17, 2018 at 8:59 PM
…brilliant idea !Dave

ChrisSimpson - Jan 17, 2018 at 9:01 PM
I found instructions how to solder aluminium to aluminium, on line, and was highly chuffed because I had several Westdale coaches to build. I envisaged soldering the ends to the roof and sides. Try as I might I could not get it to work. I gave up in the end. Suggest you follow the other solutions offered.
Chris

R.Comerford21612 - Jan 18, 2018 at 8:20 AM
The method Allen mentioned certainly works I did some in HO years ago. However I just used dressmakers pins.
cheers
Bob

Jim Snowdon - Jan 18, 2018 at 8:32 AM
Given that the original post refers to carriage lighting and aluminium, I would read this as appertaining to the last generation or Jackson/Romford rolling stock wheels, which were machined from aluminium and fitted with axle bushes to provide the insulation. The technique of jamming a pin between the wheel and axle may still work (I have never needed to try it) but is on a different scale to breaching rim insulation.
Jim

mike green 3125 - Jan 18, 2018 at 3:54 PM
Thanks for all of your replies, Jim you have it exactly, I have been able to tin the steel but one bogie the ally will not take the other one took but it appeared to be the paint on the wheel that acted as flux. I think I will now try drilling a hole in the bush, which has a flat where I cut it away to bridge with solder, and hammering gently a coned piece of copper from the earth wire out of T&E power cable.
many thanks for you suggestions, will let you know if I an successful.
mike

ChrisSimpson - Jan 18, 2018 at 4:14 PM
The guide to soldering aluminium that I found explains that the Al oxidises so quickly that the material has to be continually abraded/scraped under flux, while being heated. I could not get solder to take to the Al at all, and reverted back to adhesive.
Chris

Jim Snowdon - Jan 18, 2018 at 4:24 PM
Mike,
As a possible alternative, drill a small hole in the web of the wheel, then rivet a piece of copper into it. Then connect from the copper “rivet” to the steel axle, thus avoiding trying to solder to aluminum entirely.
Jim

mike green 3125 - Jan 18, 2018 at 5:15 PM
Thanks Jim that's so obvious and I should be able to drill from the front of the wheels using a mini drill. At the moment I am trying this to replace rechargeable batteries that I think are not charging fully as they only last for about an hour after a three to four charge time, I don't know how old they are as I bought the coaches second hand a couple of years ago, the chap I got them from didn't know either. There are 12 to 16 LED's in a coach all in parallel already wired together with a reed switch to turn on and off, so as I use DCC I thought I would try pickup via alternate sides of the bogies. Thanks for the help
Mike

SimonD - Jan 18, 2018 at 6:55 PM
Mike,
If it doesn’t work satisfactorily, you can always use wipers, though of course this adds some drag to the train.

I have arranged my coach lighting to be supported by a keep-alive capacitor, this works on DCC, I’m sure it could on DC too, with a little jiggery-pokery. Story here:
http://www.rmweb.co.uk/community/index.php?/topic/79052-porth-dinllaen-in-0/?p=2056860

Best
Simon

mike green 3125 - Jan 19, 2018 at 5:13 PM
Just a quick note as to the results. When I started to drill the hole in the wheel disc I discovered that they are stainless not alloy, thought they were alloy as non magnetic, the copper installed and wound round the axle, tested and a dead short, when all four wheels complete put on the track and tested the volts from the two wires, 14v DCC on track, 5 to 9 volts as I rolled the coach so took the bogie off the base plate and 75% of the contact area had black paint on it so must have acted as some resistance, also the wheel treads were slightly dirty so a good clean and I now have 13.5v DC via a bridge rectifier, now need to know what size resistor needed to get down to 2-3volts.

Simon, as you can see I am using DCC, do you know if I can connect the new DC input to the rechargeable units already installed to give constant lights or does it need a capacitor for stay alive? if so should it go before the rectifier? I am not very electronically minded but have got my head around DCC after 25 years use!
mike

SimonD - Jan 19, 2018 at 5:35 PM
Mike,
I didn’t use batteries, but a capacitor, which should have an infinite (well, long enough not to care about it) life whereas I guess your rechargeable batteries have gone past the point of no return. I wouldn’t bother replacing them with batteries, the capacitor is cheaper too. You’ll see that in post 238 of my RMW thread, that I swapped the bridge rectifier for a single diode, as this produced a lower net voltage, thus dimmer LEDs. I can’t do a diagram for you now, but I hope this list will make sense; please note that I used a ready-made strip with LEDs and resistors pre-assembled.

First pickup is connected to the cathode of the diode, and the negative side of the lighting strip, and the negative (stripe) side of the capacitor. Anode of the diode is connected to the positive (no stripe) side of the capacitor and the first resistor.

Other end of first resistor to second resistor. Other end of second resistor to positive side of lighting strip.

All being well, the LEDs should light up when you put it on the track, and it should fade slowly when you lift it off.

If you don’t want to bother with the diode & capacitor (or batteries) you still need connect a resistor in the circuit between the LEDs and the pickups, but this is a bit risky, ideally you’d have a resistor for every LED, but given the LEDs are already wired in parallel, you probably don’t want to do that. Your resistor must limit the current to around 10mA per LED, so multiply the number of LEDs by 10mA to get a total current, and divide your voltage by that number. This will give you an ideal resistor value, probably not readily available, so choose the next higher standard value. Hope this gets you there!

Best
Simon

mike green 3125 - Jan 19, 2018 at 5:53 PM
Thanks for that Simon, I will have to have a look are the way the LED's are wired as there are two copper tapes running under the seats connected to the existing batteries, think I will take the batteries out.
mike

mike green 3125 - Feb 9, 2018 at 5:34 PM
Just an update, took the batteries out connected the wires up and installed a 400 ohm resister, voltage then measured 3.2v which ever way I connected the wiring no lights so reconnected the batteries and charged the for 4hrs, the lights work. I think the problem I thought was the batteries being expired was due to not enough charge, the recommended time was 2hrs which is the time it takes to recharge the batteries in the unit I have, but rereading the instructions, the time is per battery so with 2 in series in the coaches you have to double the charge time!

I would still like to have pickup from the track but can find no reason why the LED's would not light unless the DCC signal through the bridge rectifier does not give DC although my meter shows 14.2v AC from the track and 3.2v DC from the rectifier.
Anybody have any idea?
mike

SimonD - Feb 9, 2018 at 6:44 PM
The rectifier should give DC from the track DCC which is of course AC - I’d expect it’s output to be around 15V but this will depend on your track voltage. It won’t be, if there’s something connected across its output which is dragging the voltage down, or if one or more of the diodes in the rectifier has died.

My guess is that the 3.2V DC that you’re seeing is coming from your battery. If you can disconnect the rectifier output and measure the voltage across it when it’s on the track, you may find volts, or not!
Best
Simon

Thompson21380 - Feb 9, 2018 at 7:59 PM
As Simon says the DC voltage from the bridge rectifier should be around the same as the AC RMS voltage input from the track, unless you have a Capacitor across it's output, in which case it will be considerably more (around 1.4 times).
So, by the sound of it you have either got a short or the rectifier has failed or an open circuit and you are just reading the Battery voltage.
Best to disconnect the Battery as Simon suggests and see if you have the full voltage output from the Rectifier and go from there.
Bob

mike green 3125 - Feb 10, 2018 at 5:25 PM
Simon &Bob, the batteries had been taken out of the carriage so the volts were direct from the track. The rectifier is new so the drop in volts I think is due to resistance of the connection via the wires and wheels, I have tried connecting the rectifier directly to the track and the voltage is the same 13.4 on input and output so I have not been able to understand the 3.2v that I get from the new connection in the coach.
Mike

SimonD - Feb 10, 2018 at 5:31 PM
Mike,
Whatever the resistance is between track & rectifier, assuming there’s a circuit at all, it should be much less than the internal resistance of your multimeter, so I think you can discount that. It sounds to me that something is pulling the voltage down. Is there any other circuitry in there? Can you post a diagram or a photo, or both?
Best
Simon

mike green 3125 - Feb 10, 2018 at 5:53 PM
Simon, there's no other circuitry, just one wire from each bogie!
Mike

Mike, so your problem as you say must be with the pick-ups?
Can you not use a wiper pick-up, phosphur bronze or similar, on the backs of the Aluminium wheels?
Bob

mike green 3125 - Feb 11, 2018 at 5:19 PM
Bob, the bogies are fully compensated and there is no easy way to fit wiper pickups plus the drag makes them to heavy to pul, also the coach is very heavy. I have a set of MTH continental coaches with wiper pickups that I had to almost remove as they could not be pulled by any of my locomotives even my Deltic would not move them.
Mike

Thompson21380 - Feb 14, 2018 at 11:41 AM
Mike,

I have quite a few compensated Loco's fitted with wiper pick-ups and never had any real issues, but of course maybe your case is different.
As far as drag is concerned, there shouldn't be an issue provided of course one doesn't try to overdo the the spring pressure.
I tend to use Phosphor bronze strip 1.0 mm x 0.15 mm thick with just a gentle pressure on the back of the wheel with the other end soldered onto double sided Copper clad board. I've even used this method for coach lighting on quite lightweight coaches and never found it to cause excess drag. I would suggest you persevere because you are never going to be able to Solder Stainless or Aluminium with any measure of success.
Do let us know how you get on.
Bob

End of thread