Pecos River Brass 4-6-2

[ATSF_Ron]

Last month I scored a PRB 4-6-2 off eBay for a great price.  It was sold "as is" but the seller said it bench tested fine.  That is true.  I put it on the track.  Nothing but a hum.  Put it in a foam cradle and hooked it up to power leads.  The motor ran fine at all speeds.  Hmmm...Then when I went to put it back on the track again, I noticed the trucks had the insulated wheels on the opposite side of the loco's insulated wheels.  AHA!  So I flipped the trucks 180 degrees and problem solved.. Sort of.  It ran but very herky-jerky.  Off I went to Spookshow's web site to investigate.  Looked at both the 4-6-2 and the 4-6-4 pics.  My loco wiring looks identical to the 4-6-4 wiring, so I disassembled the loco.  I noticed a pretty crappy looking solder joint on the fitting at the end of the motor power lead.  The one that connects to the tender drawbar.  I fixed that & put everything back together.  A bit better but still poor performance.

Back to the foam cradle.  Peteski mentioned in my other thread (SP C-9) that if it runs fine on power leads then the problem is most likely that dang drawbar connection.  I pulled all of that apart.  Everything looked ok except for the drawbar bends.  There should be a double 90 degree bend, but one of the 90s looks more like 85 or so, and it slopes upward as it goes toward the tender.  I also noticed that in the double 90 bend that clearances between the drawbar, loco frame, and connecting screw looked microscopically small.  Also, when testing on power leads, if I moved the drawbar from side to side, there were small blueish sparks that seemed to indicate temporary shorting to the loco frame.  This only happened when the drawbar was positioned parallel with the track.  Never when off center.  That makes me suspect that the "off 90 degree bends" of that drawbar might be a problem.

In addition to all of that, during one of my disassemblies of the drawbar parts, a VERY tiny washer went airborne, never to be seen again. The loco shorts out completely without that washer.  I took Peteski's advice and fashioned a new one out of .010 styrene.  As near as I can tell it seems to work.  Lastly, as long as I have the loco shell off, everything runs at about 85% of how I feel it should be running.  Once the shell goes back on, there's only a hum and no forward or reverse motion.  Yet back in the cradle on power leads, everything is fine.  I'm stumped!  Anyone have any other thoughts on this or see something I'm missing?

[ATSF_Ron]

One other thought I had was completely bypassing the stinking drawbar business.  Would it be possible to take the motor lead wire and run it along the tender drawbar to the tender post power connection and just solder it there?  Then I could just bypass all the finicky washer/screw/spring monkey business!  That seems like the simplest thing to do.  If that's possible then I wonder why the manufacturers didn't just do that back in the day when these things were made?

[nkalanaga]

That would work fine, as long as you don't want to separate the loco and tender.  If you do want to be able to, a small plug/socket will solve that problem.  Or, attach the wire to the tender end with a small screw, so it can be loosened.

That's also why most manufacturers didn't do it - they wanted to leave the loco and tender separate, for various reason.  But if you don't plan to separate them, soldering isn't a problem, and will certainly eliminate drawbar electrical issues..

[mmagliaro]

Since it hums on the track, but doesn't run, that implies a mechanical jam, not a short. 
Can you put an ammeter inline with the power to the track, only turn the throttle up about halfway,
and see if it's drawing a LOT of current when it hums?
(like  1 amp, or more?)  If you aren't drawing a lot of current, it is not a short.  It is a mechanical jam.

[randgust]

If you think the PRB 4-6-2 has issues, try the Jamco 3400.

The pickup on that was probably way worse.   But I beat it by junking the entire tender and replacing it with ATSFmodels (Dirks) ATSF oil tender, because not only does it look way better but he's come up with 6-wheel, end-axle pickup trucks on it.    Now, I also hard-wired the tender to the locomotive (screws under the tender to allow disconnect) to ditch the drawbar.  Get rid of the drawbar and come up with end-axle pickups on the tender and you will forever banish those issues.   That was so significant on the Jamco that I didn't mess with the motor when I thought I'd have to go to a flywheel.

https://atsfnscalemodels.com/projects/Tender%2520trucks%252C%25204-wheel%2520archbar%252C%25206-wheel%252012K%2520and%252015K%252C%25206-wheel%252020K.html

I've become so passionate about tender trucks and end-axle pickups and hard-wiring it's baked in now.   

You'll see what I'm up to on the Decapod thread, same principles, and I'm using a disconnect plug on that one.

[ATSF_Ron]

Randgust, interestingly I just found that ATSF web site last night in my search for the drawbar solution.  At the moment that looks like my best option.  I also don't have any issue keeping loco and tender attached.  I have several BLI steamers and those are basically permanently coupled.  No big deal to me.

Max, I'm not sure I understand how it is a mechanical bind.  With the loco fully reassembled, it runs fine in a foam cradle with alligator clips.  It's when I have back on the track WITH tender attached that there is an issue.  I recently moved and am still going through my hobby boxes, so there's no ammeter test until I find that.  --___--

Thanks for the feedback, guys!

[mmagliaro]

I think it's more likely to be a mechanical bind, because if it were a short circuit, the motor would probably get near zero
volts and would not hum. 
Putting it on the track puts weight on the drivers, and things can change.  It will not be the first time I've had an engine
that runs on its back but won't run when it's flipped over.

To make any sensible progress here, you really need to start eliminating things.  Finding out for sure if you
have a short is critical.

Things to try:

What is the current draw when you put it on the track?   
Does it trip your throttle or power pack overload?
Can you gently nudge the engine back and forth and see the drivers roll, or are they locked and sliding
along the rails?
If you put another engine on the track at the same time, at half throttle, does it run while the Pecos River just
sits there and hums, or does it stop dead when you put the Pecos River on there?
If it is humming and you lift the engine gently up just a hair to take weight off it, does it start running?

-- These things will tell us for sure if there's a short circuit going on.
Once we know that, you can start hunting for the problem properly.

[ATSF_Ron]

Max, thanks for those tips.  I'll be on the hunt for that meter tomorrow morning.  Thank God for retirement! (First month!)

[mmagliaro]

Max, thanks for those tips.  I'll be on the hunt for that meter tomorrow morning.  Thank God for retirement! (First month!)

Any small multimeter with a DC current range that can go up to 5A (10A would be better) will do the trick.  You don't have to spend a fortune on this if you don't have one.  There are decent meters that can do this for under $50 or even less.
I did a 5 minute poke around the internet.  Something like this would do the trick:
https://www.amazon.com/AstroAI-Multimeter-Resistance-Transistors-Temperature/dp/B071JL6LLL?tag=toolnerds-20&geniuslink=true&th=1
(and no, I'm not a shill for Amazon, nor do I get a kickback from them.. LOL!)

[nkalanaga]

Put a small 12 volt bulb across the track.  With normal current draw, the bulb will stay lit.  If the loco has a short, the bulb should go out, and if not, will be very dim.  If it DOESN'T go out, but just dims, check your circuit breaker!

I know, a multimeter is a lot better, but for a quick check, the light bulb beats a midnight trip to the hardware store.

[ATSF_Ron]

Kalanaga, I have not tried the light bulb method yet.  However, I did put the steamer on the track and tried lifting it slightly and giving a slight push.  One of Max's suggestions.  I did this the other day and got nothing.
 Today?  Bingo.  It would move, but not far.  When it DID run it was super smooth.  Any variation in curvature and it would stall.  I also put an Atlas GP9 on the track that I had handy and tried to run them together.  When the stalls happened, the GP would still move but slowed to a crawl.  Without a meter or lightbulb, I can only guess this is a short.  Hopefully I find my meter by tomorrow.  I still have several boxes to go through.

As far as bypassing the drawbar, is it simply a matter of disconnecting the motor lead from the drawbar attachment point and soldering it directly to the tender post?  Will I need to do any further insulating of the screw at the loco end from the drawbar attachment point?  I'm not all that "electronics intelligent," if you get my meaning.  If it's that simple then I'm going for it and seeing what happens.  The tender post looks to be nickel silver or something similar.

[nkalanaga]

If the GP slows way down, but keeps going, you definitely have a large current draw.  If it doesn't blow the breaker, it probably isn't a direct short, or you have so much voltage loss in your track that the short can't draw enough current to trip the breaker.  It sounds like Max is probably right, and you have a mechanical bind somewhere.

If it's the latter, you need bigger feeders!  I had that problem in one part of my layout.  Trains ran nice and slow, but I could short the track and the breaker wouldn't blow, on DC.  I finally put in larger bus wires, simply so that I could FIND shorts!

Having absolutely no experience with brass steam locos, if the drawbar is directly connected to the tender, then yes, you should be able to connect the motor lead to the tender.

In fact, if you want to, solder a new wire to the motor lead/drawbar attachment point, and the other end of it to the tender.  That will give you two connections, and more importantly, you won't have undo anything.  If it works, leave it that way.  If it doesn't help, you can remove the new wire, and everything is as it was.

[mmagliaro]

If the GP slows way down when your 4-6-2 stops, and the breaker doesn't pop, it could be a a short, but not a totally
dead short, or, as nkalanga points out, the breaker could be bad.

WHAT KIND OF THROTTLE are you testing this with, by the way?


The fact that you can rock the engine side to side and get it to run for
a few seconds really sounds like a short.

Things to test:

1. Put a screwdriver across the rails, turn the power up halfway, and see if the breaker trips immediately.  If it doesn't,
the breaker isn't working and your 4-6-2 most like does indeed have a short.

2 Can you take the pilot and trailing trucks off and run it?  See if it runs on the track without them.  They are notorious for
shorting to the sideframes or underside of the chassis on brass engines.  Even if both wheels on each axle in those
trucks are insulated from the axle, the wheel itself can still touch the truck frame or chassis and the rail and short the whole
thing out.

[ATSF_Ron]

I have a (late 1980s era?) MRC Tech 2 Railmaster 2400 for my DC locos.  I tried the screwdriver on the rails.  No breaker activity.  Took off front AND rear trucks and tested.  No change with either or both removed.  Strangely, I happened to be lightly pressing down on the loco and it ran fine, as long as I kept gentle pressure on it.  It also runs better in reverse than forward.  I still notice tiny sparking at the drawbar, right under the cab where that pesky screw/drawbar connection is.  Still haven't found the meter.  It'll turn up soon.  I'm just about through all my boxes.

I may try what nkalanaga suggested and run an extension wire from the motor lead directly to the tender and bypass the drawbar/screw electrical connection altogether to see if that helps.  No biggie if it doesn't, and I can just remove the new wire.  It seems like a fairly easy mod to try.

Thanks again!

[mmagliaro]

Well, not to bash MRC too hard, but the old thermal glass device used in the 2400 wasn't the most reliable thing around.
Actually, it was pretty awful.

You've got a short.  It isn't tripping the breaker because the breaker isn't working.
So that mystery is solved.

I didn't realize you were still getting sparking at the drawbar.   Try removing the whole thing: pin, insulator, soldered wire --- all of it.
Then just put the engine with no tender on the track and touch a clip lead between the now-dangling motor wire and the tender-side rail.
I bet it works.  And if it does, clip the lead you were touching to the track to the tender draw pin instead.  If that runs, you've eliminated everything and it's the drawbar for sure.