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

[BCR 570]

Hi Randy

Re the Tomytec TM20 chassis, could it run with just one truck powered (e.g. rear truck disconnected)?  I am looking into a potential Sperry car build and would have to replace the rear truck.  I could probably do rear truck pick-up but not rear truck drive.


Thank you,

Tim

[randgust]

Hey, still here...

Yes it will work, but, you have to do the same thing Bachmann did and weight one in to the max and leave the other end alone.   And keep the other truck at least live for electrical contact for sure.

The Tomytec truck drives have two flavors, long and short wheelbase.   I used the short wheelbase for mine, which has INSIDE, not outside, end axle contacts.   They are somewhat equalized, they work better than a stiff truck frame, but not as free-rolling as end-axles.   It still really runs good, I've let it run forever at the Altoona T-trak DC loop.

If you dig out the entire thread you can see that I extended just one end of the driveshaft to get 8x8 and that driveshaft ended up so low you can't even see it in the car through the windows, that's really the better approach.

I did the very same thing to an old Bachmann metroliner for Lee Weldon.   

The only thing I don't like is that the Tomytec motors, in general, are not as durable as any given Kato or Atlas motor or have the torque.  I've driven off the Tomytec flywheels and done swaps to those motors (to keep the universals), but it's a chore.   I've never burned out an Atlas motor, I've trashed two Tomytecs.

[BCR 570]

Thank you for your reply; I have the TM20 en route to me so we will see what type it is when it arrives.  I will evaluate whether to go with the Bachmann or Tomytec drive.  The rear truck will have to be converted from a six-wheel truck with the centre axle removed so wont be able to power it, but might be able to get pick-up from it if I can retrofit BLMA or FVM wheels.

Tim

[peteski]

The rear truck will have to be converted from a six-wheel truck with the centre axle removed so wont be able to power it, but might be able to get pick-up from it if I can retrofit BLMA or FVM wheels.

Tim

The way FVM, BLMA, ESM, and even the newest MTL metal wheels are constructed, unless you use wheel-back or wheel-tread wipers, each wheel will only pick up power from one rail (through a wiper contacting the axle for the least amount of friction).

[Jim Starbuck]

The way FVM, BLMA, ESM, and even the newest MTL metal wheels are constructed, unless you use wheel-back or wheel-tread wipers, each wheel will only pick up power from one rail (through a wiper contacting the axle for the least amount of friction).

I’ve made electrically live axle point wheelsets out of ESM, FVM and Tangents by cutting the axle in two on two wheelsets creating half axles and using the non-insulated side of each separated with a styrene axle tube. Just make sure the half axles are cut short enough not to touch.

Jim

[peteski]

I’ve made electrically live axle point wheelsets out of ESM, FVM and Tangents by cutting the axle in two on two wheelsets creating half axles and using the non-insulated side of each separated with a styrene axle tube. Just make sure the half axles are cut short enough not to touch.

Jim

Sure, that makes them similar to Kato passenger car wheelsets.

[BCR 570]

Randy:

Still awaiting my Bachmann doodlebug and Tomytec TM2-0 chassis - due next week. 

The only thing I don't like is that the Tomytec motors, in general, are not as durable as any given Kato or Atlas motor or have the torque.  I've driven off the Tomytec flywheels and done swaps to those motors (to keep the universals), but it's a chore.   I've never burned out an Atlas motor, I've trashed two Tomytecs.

What did you replace the Tomytec motor with, and what is involved in the swap?  never done anything like that before.


Also, where did you get the non-traction tyre wheel sets from - another chassis?

Also, how are the Tomytec flanges - will they run on Atlas Code 55 track?


Thank you,

Tim

[randgust]

I'd ordered a five-pole Atlas diesel motor with the flywheels when I've done Tomytec swaps.   Either you graft an Atlas universal onto the Tomytec shaft, or redrill the Atlas motor to fit the Tomytec universals/flywheels.  Either approach works, depending on the shaft diameters.   I left the Tomytec motor in the doodlebug, it's run just fine.

It's a skill to drive off flywheels, and it's harder to put a new one on than take the old one off without damaging the motor.   I like to set up a center punch in a vise so you are always driving against the motor shaft, NEVER against the motor bearings.  I've only done that stunt for my powered express reefer because those are weighted up like a brick and expected to pul 20+ cars on their own; i.e. you're pushing the motor hard.

Tomytec usually has ONE traction tire per truck on a TM20 so it's not terrible if you just leave it.   I did have extra wheels.

The wheels are split axle with a plastic gear and are quite easy to remove off the axle/gear, chuck in a Dremel, and turn the flanges down with a file, checking with a micrometer, polish up with fine grit.  About half my customers want the flanges turned when I do either a Whitcomb or the powered boxcar builds for them.

[BCR 570]

Hi Randy

My Bachmann doodlebug and Tomytec chassis have arrived.  Two questions concerning the doodlebug:

How easy is it it to disassemble?  Does the underframe come out with just spreading the sides apart?  There are screws underneath but I suspect they hold the motor to the frame.

The various plastic parts appear to be glued in place.  I want to remove some (e.g. pilot, class lamps, bell).  Can you recommend a product for accomplishing this (e.g. a de-bonder)?


Thanks,

Tim

[randgust]

Others will have to chime in here about disassembling one that's newer than the original first-run one I got.  There's at least three flavors out there.

I salvaged the underbody parts just by removing the body and carefully sawing them off with a fine-tooth zona saw.   Same with the truck sideframes, then I simply goo'ed them on the Tomytec trucks (which have interchangeable sideframes).   I did the best I could to mimic the underbody component layout, you really can't tell by looking at it that it's not an original Bachmann, until it doesn't sound like a meatgrinder, or not move at all from white gear disease.

I just finished doing pretty much the same thing by removing bolsters, brake detail, and underbody components from a pair of AHM/Lima passenger cars to do my two ancient Western Railcraft passenger cars.   The magic zona saw rides again.   The cross-kitting of Lima cars with those etched brass sides makes for some nice cars.