General Discussion (Model Railroader)

I finally finished repowering my old Bachmann DD40 with a better mechanism. Now that it's done and working, I thought I'd post a "how to" topic on how I repowered it.

The original 4-wheel-drive mechanism was a poor runner, no matter how much I did to make it better (it does run a little better than before, but still not great). I decided to repower mine with Athearn trucks and a pair of good quality (yet inexpensive ) Mabuchi motors with flywheels.

I had to completely cut out the sections of the frame where the old trucks were mounted, and make separate frames for each truck, kind of like an old Mantua diesel. The motors are mounted on each end of the fuel tank, using flipped over A Line stick on weights, which are glued to the frame. The tape on the bottom of the weights is the same as what A Line sells for motor mounting, so you don't have to worry about the motors coming loose.

I used parts cut off from the Bachmann sideframes and some extra brake cylinders to detail the Athearn trucks. It still doesn't look quite like the DDA40X trucks, but it's close enough to look good. You can also see what the home-made front truck mount looks like in the picture. All the Athearn wheels were replaced with NWSL 40" wheels, which roll quieter, look better, conduct electricity better, and grip the track more.

I had to move some of the parts on the PC board around just enough to clear the flywheel. Some were as easy as bending them out of the way, but the large black cylinder-shaped part had to be partially unsoldered and moved closer to the PC board.

To support the front truck, I had to put whatever I could in the bottom of the cab. The stick-on lead worked well for the large open area, and then I filled the steps with whatever I could find, which was some extra plastic from a model truck.

To make the DD40 look a little more realistic, I made the walkway in the middle of the hood out of some copper sheet and glued it in place, making sure it was properly lined up with the doorways in the shell. It really does make the engine look a lot better.

All assembled! Everything is held together by super glue, so it should hold together fine as long as I'm careful. I filled the front pilot, but the rear pilot was left open so it wouldn't drag cars off the track on curves. Some of the rear coupler box had to be cut off to clear the shell.

Since I used Athearn trucks, it's not a real quiet runner, but that should hopefully improve with some run time. Other than the noise, it's now an excellent runner. The speed control is excellent, it runs smooth at all speeds, it draws less than 0.2 amps running free (which surprised me), and with a weight of, I'm guessing, over 2lb. and 16 wheel drive, it should be one of my strongest pullers. I probably spent between $70 and $80 on everything, and the engine originally cost me only $5 at a train show. Even so, I'm happy with how it turned out.

good job!

all my old pancake versions were retired long ago, replaced by the spectrum version, but if I run across any more, I'll know how to update them.

Great artical!  You made the owner of the peel-and-stick weights factory very happy!

David B

Thanks everyone for your kind comments.

One thing I forgot to mention earlier is that the DD40 can only make it around a minimum 22" radius, instead of the 16"? radius the old drive could go around. Of course, most of you would want to run an engine this size on larger curves anyway, so I guess it doesn't matter too much.

BRAKIE wrote:

Darth,Good job!  Its nice to hear there are those that still like to tinker around improving drives and re-powering less then stellar performers.

Working on things so they'll run better is one of the things I like doing in this hobby. Tonight, I just finished making my new AHM Big Boy run fairly smoothly. The boiler mounts had a LOT of slop in them, and it could hardly do anything without wobbling all over the place.

From one tinkerer to another; really kewl Darth! Where did you finally locate those worm housings? Did you order them from my LHS?

One thing I would caution about is using the stick-on weights to support the shell. I've had that tape let go over time, in spite of degreasing the mounting surfaces beforehand. If you want to stick with tape (), Scotch makes a heavy duty indoor/outdoor mounting tape that's more like the super strong servo tape I put in my RC car, but this can be found at Home Depot. I use it for motor mounting applications.

I second the motion for a video.

SteamFreak wrote:

From one tinkerer to another; really kewl Darth! Where did you finally locate those worm housings? Did you order them from my LHS? One thing I would caution about is using the stick-on weights to support the shell. I've had that tape let go over time, in spite of degreasing the mounting surfaces beforehand. If you want to stick with tape (), Scotch makes a heavy duty indoor/outdoor mounting tape that's more like the super strong servo tape I put in my RC car, but this can be found at Home Depot. I use it for motor mounting applications. I second the motion for a video.

Thanks.

I got the worm housings from a brand-new condition (but pretty old) Athearn F7A I picked up at a train show for $12 last week. Everything in that F7 was in completely un-used condition when I got it, so I'd say I got a pretty good deal on that one. The worms weren't even rounded off like in most of my other Athearns!

I'll be sure to keep an eye on the lead tape. I've found that if it let's go, super glue does an excellent job of re-sticking it. So far, the only time it's ever lost its stick is when I peeled it off of whatever it was stuck to (not an easy task!!).

I'll see if I can figure out how to use the new digital video camera this afternoon. If I do, I'll try posting a video for you all.

csmith9474 wrote:

That looks great!! I seem to remember that somebody was making an upgrade/repowering kit for the Bachmann "Centennials". Was that A-Line/PPW? I remember it being a heck of an upgrade kit, with the price to go along with it.

I haven't heard of a DD40 repower kit, but I do know that sometime last year I think? A Line got Bachmann to make a run of undecorated Spectrum DD40s for them. I don't know if they have any left at this point.

Darth Santa Fe wrote:

csmith9474 wrote: That looks great!! I seem to remember that somebody was making an upgrade/repowering kit for the Bachmann "Centennials". Was that A-Line/PPW? I remember it being a heck of an upgrade kit, with the price to go along with it. I haven't heard of a DD40 repower kit, but I do know that sometime last year I think? A Line got Bachmann to make a run of undecorated Spectrum DD40s for them. I don't know if they have any left at this point.

That is it then. It was an entire kit you could buy, and I think that it was well over $100.

Darth Santa Fe wrote:

I'll be sure to keep an eye on the lead tape. I've found that if it let's go, super glue does an excellent job of re-sticking it.

Yes, CA does a great job of gluing the weights (and various body parts ) to the frame or shell.

So what are you planning to do with all of this Union Pacific mega-power, Darth?