Working MU cables?

[randgust]

OK, here's something.

My much-loved but quirky 1982 Kato GP38 has always been plagued with pickup problems and it's in the design.  I thought it was purely in the connection between the trucks and the frame, but it's also in the axle/truck frame area.  I've devised pickup wipers to the trucks, but it still has moments where it stalls where nothing else will, flywheel or not.   

So I have a nice Kato pre-China GP30 that I consist it with that is 'conventional' design and is flawless in pickup (wipers and end-axle), usually it will nudge the GP38 when it stalls.

Not much of a solution but it's worked for a long time.  Once you get the Kato up to speed where those flywheels kick in you'd never know there was an issue.  But creeping through a yard?   Yeesh.

Now, has anybody come up with ways to make WORKING, detachable, jumper cables between units before I'm forced to cobble up something myself?  I actually think I've got a solution, but before I just charge ahead I'd like to see what other people have done.   This isn't just a DC thing, it's probably even worse in DCC, so figuring out a way to hotwire units together in a detachable way for better pickup should have universal appeal.

And, yes, I know the Kato 38 is an antique and designed like a Platypus.  But it pulls 3X more than an Atlas (which I also have), I'm keeping it.   The only thing against it is that spotty pickup and if I can figure out a good way to jumper it with it's partner GP30, I think it's a slam-dunk.

[garethashenden]

I haven't tried it, but here's my thought. If you drill a small hole upwards into each side of the frame you could push a bit of wire in there, then do the same thing on the other locomotive. The wire could be run through the pilot and made to look like an actual MU hose. Obviously separating the two engines would be more complicated than just uncoupling them, but if they always run together it shouldn't be an issue. I've seen this done with steam engines with the wire representing water lines, it can look quite convincing.

[Spades]

Would it be easier to just hard wire the trucks to the motor?  I would love to know how to do it properly,

[Steveruger45]

I see Gareth already said what I was thinking.  Yes you could use those mini pin/socket connectors but where to hide them?
On the other hand I have a very badly weathered Kato GP38-2 now a dummy with its motor and flywheels removed that I’m willing to part with. Not sure if the earlier GP38 used the same trucks though.

[ednadolski]

... has anybody come up with ways to make WORKING, detachable, jumper cables between units before I'm forced to cobble up something myself?

Seems to me that would have an inherent trade-off of robustness vs. scale size.   We're talking wire that's 0.010" diameter or smaller.

How would you even connect them, one wire at at time....? 

Fixing the pickup sounds orders of magnitude easier to me...

Ed

[Steveruger45]

Well, I’m just spit-balling here but I was thinking esu decoder wire (it’s about 0.020” OD).  Drill a couple of holes in the pilots.
Thread the wire through and solder onto each of the metal truck holding plates at what ever the coupled end is on the Kato unit. 
Similar on the atlas unit except solder onto the copper pickup strips near the tank so they don’t affect the springiness for truck contact.  Routing the wires out the way somehow.  Alternatively drill a small hole in each of the frame halves near the coupled end and solder split pin style connectors on the wire ends and push them into the holes in the frame you just drilled. This would be easier to disconnect.
Well maybe not easy. Or solder the two wires onto some double sided pcb and wedge that between the frame halves.

Oh yes and BTW the trucks on the original gp38 are the same as the revised gp38-2 ( the one I have) according to Kato parts website. They don’t have any though.

I must agree though that renewing or fixing the trucks is where I would start.

[randgust]

The irregularity in pickup isn't where I thought it was.   It's a rigid frame.  The split-axle wheels ride in a split-frame truck, the split frame truck fits into plates.  So there are two places of problems; one that the axles are not always in solid contact with the split frame truck frames, and second that the truck is not in solid contact with the frame.  I devised spring wipers that fit inside the truck pivot hole and contact the frame that have done a nice job, but feeling around with prods and jumpers proved that the axles floating around in the truck frames is the dead zone even though the truck wipers helped a lot.   So even if I hotwired the trucks to the frame won't fix it.   This is why floating end-axle pickups are so darn brilliant, they solve both problems.  They allow the trucks to flex and still keep everything in contact.   This failed design is why it's so important.

I've got a second GP38 unit I bought just for parts supply and expirimenting.   As I've added the solid MT pilots, I've got some mounting options.  I may just drill holes big enough to flush-mount a little piece of 1/16 brass tube on both sides right behind the steps on the end sill, and solder a little piece of .010 bent spring wire on to the end of a piece of stranded #22 to make two removable jumper wires between two units.  They will have to be inserted with tweezers, and they probably periodically break off the solder joint, but worth a shot.   On the locomotive pilot, the female tube will be jumpered to the frame.  The wires will be right where the original EMD cables mount, and are black insulated and very flexible.  If you alternate sides, this could turn into a 'standard', and they only sign you've done something would be a little hole in the end sill.

Here where I'm at the B&P has done this to a pair of units - GP40 #3120, and slug GP35 (ex-ALY 106) #120.   You realize something wierd is going on when you realize 120 has no radiator or fans on it.   They are jumpered together and work as a permanent pair.  The power cables between units are as big as brake hoses.

http://www.rrpicturearchives.net/showPicture.aspx?id=4537306

I still have this odd feeling I'm reinventing the wheel here.    I've had this problem since the day I bought it in '82 when I thought this would be my ideal yard switcher, but it's always failed the contact test in low-speed situations.   It's a honey once it gets rolling and those flywheels kick in, so it's been in MU road service ever since.   It's so darn heavy though that every once in a while it gets stuck to the point the GP30 just sits there spinning, trying to get it moving, so the annoyance factor says I want to fix this once and for all.    I even bought the Atlas GP38 to replace it until I discovered that those things barely pull enough to get out of their own way.

[Steveruger45]

Sounds like you have a plan that will work. But on the Kato unit the frame is a lump of lead and not split and as I recall it’s the truck holding plates that pick up power and are attached by long screws from the light board, and one screw on each end is Fitted with an insulating tube to prevent shorts.  So would need to connect your tube / plug receivers to those or route the wires up to the light board and solder them there in any case not the frame.  Anyhow pls forgive me if I’m stating the obvious that you already know on that point, which I’m pretty sure you do.
Good luck and maybe post some photos.  Those old Kato units sure can pull, they weigh so much.

[Ed Kapuscinski]

So, define "detachable".

Detachable regularly, or just for occasional storage?

[rodsup9000]

 Here how I have some of mine














I use tiny IC sockets and pins

[randgust]

Wow, that's the kind of idea I was looking for.   Hadn't thought of that.

[Sharky_McSharknose]

Here how I have some of mine

I use tiny IC sockets and pins

I've heard of someone doing something similar with BLI Alco PAs since BLI diesels are generally prone to pickup issues. I've toyed with the idea of MU-ing my BLI Centipede A-A pair. On the one hand, they don't have full pilots on the B end to make conspicuous changes to, but on the other, I think I would need to drill through the metal frame to route wires. Something like this (but cheaper!) would be ideal for this application, I think: https://www.amazon.com/2-Pin-Micro-Mini-Connectors-2/dp/B0006O94SO

[craigolio1]

Years (decades?) ago in MR a modeller a fellow MUd some HO diesels. Brass tube in each pilot. For the MU cable he used phosphor bronze wire bent into a horseshoe shape. The small tips fit in the tubes. They bend as the loco corners. The pressure of the horseshoe shape maintains contact. He maybe have bent the ends like a bobby pin to make more of a friction fit in the tube. I can’t recall. Simple design. Might work.

Craig.

[wm3798]

Not detachable, but that's what I did when I married the slug to my BL2 for the yard switching on my Western Maryland layout. The slug actually didn't have a motor it only provided additional pick up. I kept the Bachman wipers to the frame and then just ran jumpers from that frame to the split frame of the BL2. They always ran together so I didn't worry about them being detachable. I ended up selling them together. Something I regret to this day.

[rodsup9000]

https://www.amazon.com/2-Pin-Micro-Mini-Connectors-2/dp/B0006O94SO

I have a few of them and they don't work so well. I do have 3 sets of E units with this type of plug on them, but it's done under the shell. Bad thing is I have to pull the shell off the center unit to unplug them. Since I've found these pins and sockets, I want to do the whole fleet with them. It make the RR so much more reliable during operating sessions. I have melted a wire on set when one of the units derailed.