Repowering a Doodlebug (Bachmann)

[randgust]

Any Tomytec frame you get will have to likely be spliced longer, so remember that there are only a handful of variations on Tomytec despite lots and lots of different part numbers:

1)  Trucks - originals have end gear towers, "R" versions have centered gear towers.
2)   Truck wheelbase - look at the dimensions on on Plaza Japan, you're looking at 12mm and 14mm truck wheelbases
3)   Pickup system - look at the trucks.   The 14mm ones 'usually' have end-axle pickups, and the 12mm ones 'usually' have inside pickups (plates riding on the split axles).   The end-axle pickups are more reliable.    But the Doodlebug has a short-wheelbase truck, the 14mm ones are more like a 7' diesel truck.
4)   Sideframes.   Seems like all of them come with an assortment of sideframes to snap on, look closely at the package, but for the Doodlebug, I just cut off the original Bachmann ones and used those anyway.   Easy to do.

The really early ones - TM01, KD25, etc. are shorties with only one-truck drive.   Useful for my Whitcomb switcher, but even that will take the two-truck powered as you can always dummy down a powered truck to fit.

They've changed the motors as well, new ones are more of a smaller coreless motor and still work fine.   If anything, the original motors (which were a dead ringer for some Bachmann ones) were subject to premature failure - only motors I've had that wore out the finger brushes.

Other than that, the chassis are all part numbered by length.   Generally, for the doodlebug and the Metroliner, longer is better, but it still works.   I'm just glad to see the shipping cost of these from Japan come back down to earth, it was pretty scary there for a while.

[Dirk Jan Blikkendaal]

Hello Randy,

Completely missed this interesting posting.....nice work allover.

Just to add my 2 cents worth on the conversion I already created years ago.....

You all know I am a Santa Fe addict and doodle bugs fit my time frame perfectly.... so the Bachmann was a nice starting point for my M-183, but too short and mine was a lousy runner also. Got a second shell cheap somewhere and spliced the 2 together, adding a little to the front roof detail to give it more of a ATSF look (see picture).
The Santa Fe used a larger wheelbase front truck and short rear and I like all wkeel drive and pickup (like Randy). Tomytec models TM-18 and TM-23 fit the bill exactly for both trucks (15,4 mm and 12 mm axle spacing and still available and not expensive). Trucksides for these longer and shorter trucks where drawn and printed in 3D (see www.atsfnscalemodels.com) and simply slide on the Tomytec trucks using the 3 holes in the truckframe sides.   
I discovered 1 major problem..... using a single motor is impossible because the gear arrangement makes both trucks run/turn in opposite directions..... So I used 2 of the pictured tiny 12V 8 x 16 mm slow running coreless motors. You might still find them on the internet and otherwise you can try me...... I still have some single and double shaft motors available (€ 15 each).

The original TM-18 and TM-23 frame ends are used and glued between styrene strips forming the sides of the chassis. A 1 mm styrene sheet is the bottom of the chassis and a steel 3 x 3 mm, 90 mm long bar is CA glued tot the underside centered between the trucks as a stiffener. Underbody detail comes from the original Bachmann and scrap passenger car detail (see prototype pictures on the internet). There is even room extra lead wheight and for a DCC decoder, speaker and capacitor. I used a simple Digitrax SDXN136PS with doodle bug sound from John MacMasters (io.groups).

All in all not a rivet counter model, but not very expensive, running great and looking good enough Santa Fe for me.
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[Sumner]

Thanks Randy (will also be ordering your 'powered reefer' kit).   

Dirk thanks also for an alternative approach.

Sumner