The "Woody" D&H Challenger

[R.K. Maroon]

Here is a video of the D&H Challenger chassis during layout testing. I left the boiler off so I could observe operation and to make it easier to switch between series and parallel wiring:

https://youtu.be/js-Ib8PgUYw

I wanted to investigate series operation, as it seemed to provide better low-speed performance than parallel wiring during roller tests. However, the hit to top speed was not acceptable once on the layout.

Jim

[sarge]

Jim, there is another issue about series-wiring that comes into play. If the one drive goes into a free slip, the other will stop as all the current follows (literally) the path of least resistance through the free-spinning drive. The engine then stops, usually in an inconvenient spot.

As long as you don’t load the loco to its capacity and nothing slips, you get the starting performance gain with series wiring, for example taming China-drive diesels for yard or local switching use. Put it out to orbit on the mainline with a healthy sized train, this foible can be an issue.

Because of that, I have taken to putting a switch in China-drive locos I do for folks that allows you to shunt from series to parallel by slipping the cab off and flipping the switch as purpose dictates. A similar DPDT switch in a reachable place might be a fun idea to do with this engine?

[up148]

Very impressive Jim and the parallel seems to work well for the application. I'm impressed with the build and the slow speed with open frame motors that might be older than I am. Nice.

[R.K. Maroon]

Sorry for the slow reply, gents. I concur with Butch's comments: The drive really does seem to work well. One never knows when you have a novel configuration.

Brian, I agree with the tradeoff between series and parallel -- it was the promise of good starting performance that made me want to try series, but parallel seems to be fine. I think the train-stops-on-wheel-slip (with series wiring) is probably due not to all the current going into the spinning motor (as current in one always passes through the other), but because the spinning motor creates a back-emf that works to lower the effective voltage across the motors, which likewise lowers the current, which lowers torque sufficiently to stall. This is arm-chair engineering, though -- an experiment might be in order. I will volunteer, but I am out of town for a while yet, so there is plenty of time for somebody to beat me to it should they feel so inclined.

Jim

[sarge]

Jim, you probably are right as to the cause, since I never really thought it through but merely filed the effect away in the “experience file”.

I’ve had good luck taming twin-motor diesel drives with series wiring, but always made sure the environment was one not demanding maximum pulling power; switching and terminal duties were fine; mainline orbiting (especially out of reach) better done with parallel wiring. Then came the notion of a switch to change from series to parallel with twin-motor diesels.

Your case being what it is, I believe parallel wiring should be more than fine. I merely tossed out the notion of a switch in case you wanted to have the capability to show off in slow motion a bit. Grin!

[up148]

Hey Brian, congratulations and enjoyed reading about and viewing your layout in OSR. Nice.

[De Bruin]

Yes, second that; Brian's layout is really well thought out and executed for realistic operation!

[sarge]

Thanks, gents. It’s been a fun build so-far, and the first several ops sessions have been quite successful. Come join us when you are passing through!

The best part is the local O Scalers are being featured as a group, and its a privilege to be just another member of what is a very talented bunch of guys. Mine was the third in the series after Art S. and Attalee T., and wait til you see the next couple of layouts coming up from this crowd!

[R.K. Maroon]

I considered posting this to the "What's on Your Workbench" thread, but decided to continue here. After a long delay, I finally got Woody's Challenger back on the workbench. The main goal is to assemble the boiler to the chassis. If you will recall, the chassis ran very well as-is, but I noticed that front universal joint was worn:



This side of the joint has some wear but notice that the pin is at least still round and the yoke not quite at the point of failure. Compare now to the other side of the joint:



Whoa -- this locomotive has more run time than I would have suspected. I'll take the fact that it still runs so well as a good sign. But this U-joint clearly needs to be replaced.

Jim

[up148]

Yeah, I think the owners of this loco have really enjoyed it over the years. It also proves just how good the materials were at that time. My USH locos are still the most robust and best running locos I own and will stay that way long after I'm gone.

[ScaleCraft]

That trunnion joint next to the u-joint is pretty worn, too.

I know about trunnion joints! OLD cars, Willys, Chrysler products....and steering column on MK Jags!

[R.K. Maroon]

By good chance I had a brand new replacement u-joint, same make and model:





I want to say this is a Precision Scale item. Yes? No?

A little white lithium grease and the chassis should be good to go.

On to the boiler -- the next step will be to inspect the headlight installation.

Jim

[up148]

Not sure of MFG, but that sure makes a clean repair.....wow. Nice stash find Jim!

[R.K. Maroon]

I got distracted by other projects over the last two months but got back on the Challenger yesterday. The smokebox front was a slide fit to the boiler and thus easy to remove. The headlight checked out good, with the wiring just needing some minor cleanup and completion. That gave a green Iight to assembly of the boiler to the chassis. I didn't have the experience of taking it apart, but Bob provided good notes and, after a few false starts and head-scratching I was able to figure it out:



This is the first time to see it with my own eyes fully assembled (and not exploded) -- what a great model, and what great restoration work by Bob (with thanks also to Dave for his help in making it all happen). I discovered a small amount of interference -- just enough to keep the boiler from sitting down flush with the rear steam chest. So I get to take it apart again, but this time I know what I am doing so no worries (famous last words). There is also still some handrail repair to do but I hope to have a test run of engine and tender soon.

Jim

[up148]

Nice model Jim. A few decals and some weathering and it will be an outstanding model.