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Linking power between power units

Posted: Sun Jan 07, 2018 10:32 am
by dkightley
I'm not sure if anyone has posted having fitted power wires between two power cars so that all of the 8 axles share the load of powering both motors. I know its been done...but can't remember exactly who has done it. SO I thought I'd give it a go....seeing as I'm intending to share a DCC decoder between two power units anyway!

I've sourced some 29awg (0.28mm) 7 Core Copper Teflon Insulated Connecting Wire ....and I've bought some in six different insulation colours. Nice and flexible! I've simply soldered the wires between the busbar strips of one power unit and the strips in the other unit.

To facilitate the wires, I've made small slots in the ends of the body shells, and essentially draped the wires along the top of the power chassis, and down the end, forming a "u" shape into the slot in the other shell, etc. Here's a couple of photos of the installation in my Scotrail 158 DMU:
IMG_3344_red.JPG (52.9 KiB) Viewed 4399 times
Can't see the join!!!!
IMG_3350_red.JPG (52.86 KiB) Viewed 4399 times
Apologies for this shot being brurry. I had to use my phone as I've temporarily mislaid my camera. :(

I've also superglued the couplings together so the two-car set is now handled as one unit. I've removed the tiny springs on the couplings so that everything waggles about nice and freely.

I've done the same with my 3-car Scotrail 170 DMU....and the wires run through the centre carriage quite nicely. Their performance at the Chiltern Show next weekend will be the big test as to whether the exercise has been worth it.....hopefully they should run smoother, which they seem to do on my test track!

Re: Linking power between power units

Posted: Mon Jan 08, 2018 1:38 am
by martink
I did that with mine right from the beginning. It makes a big difference, particularly late in an exhibition day when performance is falling off. The only problems I have had are if the wires aren't flexible enough - the train can derail on some curves. Some fiddling and adjustment may be required.

Re: Linking power between power units

Posted: Mon Jan 08, 2018 7:19 pm
by gbtrains
Hi all
could I suggest some very small magnets, one for positive and one for the return feed as it could be the answer if you can source the smallest magnets out as then the current could ride from the engine through the magnet couplings and then to the secondary unit.

Iknow this works in N Gauge but not seen magnets small enough to do our scale.

well done of what you both have done as I know how time consuming this can be and they fiddly. :)


Re: Linking power between power units

Posted: Mon Jan 08, 2018 9:33 pm
by dkightley
I thought it may have been you that had done this....but I wasn't sure. I'm fairly confident I'll not have issues with the wire stiffness causing derailments on curves. The wire I've used is very flexible and is almost impossible to kink! And with the wire being so small...and fairly large slots in the ends of the bodies....I'm sure they'll be okay. The biggest problem is going from a tight left hand curve into a tight right hand curve ...or vice versa...where the end of one body is off to one side and the end of the other body is way off in the opposite direction. And my test track has such a torture on it....and both DMUs run through this trap with no issue.

I see where you're coming from.....but I don't think I'll try it. The smallest magnets I'm aware of are 1mm x 1mm x 1mm....and my plans are to fit a single DCC chip in a two-car DMU set, which means four connections between units.....and this would be too much for any form of magnetic conducting coupling. And if you're wondering why 4 wires....2 to connect LH & RH supply power, and 2 to connect remote motor to the chip. A few inches of wire is a darn site cheaper than a second DCC chip!! And I'll need to use 4 wires if using DCC with a short chassis power unit where the chip will need to be in a carriage, etc.

Re: Linking power between power units

Posted: Sat Jan 13, 2018 9:13 pm
by dkightley
After one day at the Chiltern show, I have to say I'm impressed with the improvement in running performance. I ran the Class 170 all day and had what I originally thought was running problems with the linking of power....but traced the issue, which was derailing of the centre carriage on the Class 170, to a dip in the track caused by an out of alignment track joint. Once resolved, the unit performed flawlessly....and with improved slow running.