Repowering a Doodlebug (Bachmann)

[randgust]

I got one of the first-release Bachmann doodlebugs years ago, and it's been pretty much of a shelf queen since.   According to Spookshow, mine is one of the first run with the square motor and no decoder.

It's 'close enough' for me for prototype to the PRR ones that ran in this area; my father rode on one locally on the Salamanca Branch in what I think was 1927, and it was replaced by a D16 4-4-0 the following year that hung around until the 30's.  The Bachmann Brills are definitely a later model that what PRR initially experimented with in 26-27, but still close enough for me.   But they certainly ran locally as a generic breed.  I'm not enough of an SPF to want to build the 'right' car, but I would like a model that works at slow speed and is quiet and reliable.

But the model is 'meh', front truck power, pretty noisy, fair but not good pickup.  On the 'someday I'll improve this thing' list.   

With all the work I've done with Tomytec mechanisms I noticed that the long-frame short-truck wheelbase chassis (TM20) would probably be a good adaptation if I ever got around to it, and with that I'd get 8x8 drive and pickup, and could put any motor in there I wanted.   Someday.

In cleaning out my parts inventory for Christmas sales, well yeah, I'd bought a TM20 chassis I'd forgotten about.   Why not... looks like a pretty easy job, actually.  And I'll bet I can turn around and just sell the original Bachmann chassis under that body, too.   I looked (briefly) at getting a current issue one, but apparently the PRR scheme only was on the first issue.   And Mark says they are still noisy.

Dissassembly of the body was easy, and the TM20 chassis basically needed lengthening, ran well, looks like a go.   So I'll start to document this process.  I've already gotten as far as lengthening the plastic frame to fit and it worked out rather well.   

[randgust]

Part II on the kicker was having to prove to myself, one more time, that there was not much more I could do on the original design.   I'll admit that the last time I ran the thing was a couple years ago.   It's still one of the borderline mechanisms that I have to wonder if the project is worth doing and if I'm really making something worth the effort here.    The original chassis isn't THAT bad, really...

Put it on the track.....click, click, click, click......  Uh-oh.   Is that what I think it is?    Bachmann white gear cracking?   This thing doesn't have enough run time on it and has hardly ever been out of the case..   Huh.   Well, it's a chore to tear that truck apart to even find out, but there's no visible debris in the gear and by the rhythm of the noise, it's the main worm gear in the truck buried in there that is probably cracked.   So much for my sell plan.  I'll still tear it apart to at least prove it to myself though.

I suspect that pretty much cinches it that repowering with non-Bachmann parts is the plan.  Sigh.  Well, here we go.     

[mmagliaro]

I don't think run time has much to do with those gears cracking.  They are bored too small and pressed on their shafts, and they are under continual stress that the plastic can't handle.  Running it puts very minimal additional stress on that gear compared to the pain it is bearing already.

[Doug G.]

I agree with Max. I don't think running time has much to do with cracking. The stress on the plastic is there, regardless.

That being said, my Pennsy one still runs fine. It doesn't "click", anyway.



Doug

[randgust]

Just in case anybody wonders....did you even TRY?? Yes, Bachmann has some doodlebug parts, and yes, as I suspected, the power truck is sold out.   Coincidence?   You can get an entirely new chassis though.
The exploded parts diagram online is the current build, not the one I have.  https://www.bachmanntrains.com/home-usa/dwg/dwgs/N814X__Doodlebug1.pdf

This may be the only 'white gear era' Bachmann Spectrum I've got, but at this point, I'm already launch commit to repower the thing with Tomytec parts anyway.  I'm just the kind of guy that likes doing an N scale necroscopy to prove a point though.   I have no plan to repair the gear even if I do find it.  I was rather surprised to find that all the detail on the underbody, and the steps, etc. was press-on the cast frame and came off the chassis rather nicely and can be transplanted.   It's still a pretty good model.

[peteski]

I don't think run time has much to do with those gears cracking.  They are bored too small and pressed on their shafts, and they are under continual stress that the plastic can't handle.  Running it puts very minimal additional stress on that gear compared to the pain it is bearing already.

Another vote for the stress-cracking being totally unrelated to running. They will crack even when the model sits in the warehouse.

[Tom L]

Looking forward to this as I'm currently re-working one of these into something that more resembles a MStL doodlebug towards the end of their usage. I have one of the old version and a new one. The newer mech isn't nearly as noisy as my old one but certanly isn't quiet. It seems to be more of a whine vs the grinding of the old style. Anyway, one advantage to re-power might be pulling power. MStL doodlebugs in my modeling era pulled a Express car (rebuilt troop sleeper) and sometimes a additional boxcar or two. I have seen photos of them pulling a Express car, boxcar and an old baggage car. As is, my stock unit seems to struggle with more than one boxcar up a short grade, this might improve pulling power as well.

FWIW, I got my newer unit, with a coach, for like $50. They were marked down at Kleins and then they had one of those 10% off coupon codes promomotions. The new and the old bodies are the same, but they are nicely detailed models.

Tom L.
Wellington CO

[randgust]

OK, so here's the concept.   Take a TM20 and lengthen it - quite a bit, actually - final 'plug' ended up being 10' additional.

The good news is that the TM20 is narrower than the shell, by about .040.  So the basic approach was to put on two new side sills .020 x 68' x 30" to extended the frame out, and a plug of .020 in the bottom.   I used Micro-Mark 'same stuff' cement as Testors won't touch the black styrene on the frame of Tomytec products and that stuff glues it nicely.





Now the first catch is that to keep it simple, I simply extended the stock pickup contacts by soldering on thin brass extensions, tinning both sides of everything before they got final hot assembly in the frame.   You could use wire, or about anything, to do the same thing.





The 'long end' driveshaft is cut in half and will be spliced with brass K&S tubing, held with ACC.

The TM20 truck is a 32" wheel on a 6' 6" wheelbase.  The Bachmann is a 34" wheel on a 6' 8" wheelbase.  Because somebody will care.

[randgust]

Test fitting this in the shell looks good although the height fit will have to be carefully checked, the frame bottom is higher.  The window inserts have to be cut to the bottom of the window edge to make a 'shelf' to fit the frame into the body, from the looks of things.   The original top-of-rail comes out to be 42" and the Tomytec measures out 48" frame bottom to top of rail.



All the underbody detail, steps, etc, can be robbed from the old frame.   Here's a comparison of the two chassis:



Tomytec supplies drop-equalizer truck sideframes that look so similar to the Brill design that I'll probably use them.  They just press on.

As for how much this could pull...well, with two traction tires, it's a matter of how much you want to fill in that body with lead.  I plan to use a stock Tomytec weight for the front and put some weight in the roof for the back, but if the pickup is good, that will be about it as I don't even plan on pulling a trailer.

Oh, and if I needed any more motivation to do this, when I picked the Bachmann chassis up after that photo, one of the rear idler wheels fell out.   You can see inside the truck that the white plastic center axle is cracked.  Metal wheel just fell out on its own.

[Ed Kapuscinski]

You know, if you're going through all that work already, you might as well do a new more PRR body for it too... just sayin.

[randgust]

I have less-than-average passion with this project, as the model is rarely used.   I've been thinking about putting a decoder in it so it could be run at the Altoona show on the Ttrak modules.  If I hadn't stumbled across the long-forgotten TM20 I'd have done a different project. 

If I was doing it right, there's a lot of problems.   I've got a couple firm data points, one that PRR reportedly went into the doodlebug business big-time in 1926 (reference:  Western NY & Pennsylvania RR, Pietrak, pg 12-1).   There's a shot of Brill doodlebug 4668 in the Olean yard in 1930 on the Rochester-Olean run.  My father's recollection of a doodlebug on the Oil City-Olean local, and it was replaced the following year with a steam train, jives with the 1926 date as well.   Problem is that MOST of the Brill motorcars were build after 1926, so just exactly what that car was is completely uncertain, it certainly wasn't one of the more modern Brills.   Looking at NE Railfan.net there's some really old ones that aren't even close to what I'm building here.  So with no firm idea of what the car# actually was when it was on the branch I model in modules, there's no accurate prototype to follow anyway.

But in general terms, there's sure a lot of photos and diagrams out there.   This one shows that the rail-to-side-sill clearance as 36" with 42" to the frame bottom:
http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=gew275.gif&sel=gaselectric&sz=sm&fr=

And the NE railfan net page is:  http://www.northeast.railfan.net/self_prop4.html
4668 is there but it shows a build date of 1930, so....   All in all, unless I can prove otherwise, I'm happy enough with the generic Bachmann.   PRR certainly did like big funky high arched roofs and portholes though.    What I do want to do, and is on my bucket list, is do a proper D16s, as that's what replaced the doodlebug and ran until 1937.   One confirmed D16 locomotive is 6239, another is 1046.  1046 is the one I want to do.   I'm all but certain that's the one my father rode behind.   I've read some stories that some districts of the PRR hated the motorcars with a passion, there has to be a good reason that PRR held onto a 4-4-0 on this run, that late, after a one-year experiment with a Brill.  http://www.northeast.railfan.net/images/prr1046s.jpg

[randgust]

Got the second driveshaft spliced in and working.....wow.   Does this ever run nice.  Quiet, good pickup....yeah, this was worth it.   The only real noise is the sound of the rails clicking over the joints.   

[Tom L]

Nice! Looks like a pretty straight forward procedure. Adding weight won't be a problem for me as my version will have less windows. Apparently there weren't many people traveling from the Twin Cities of Minnesota to Watertown, South Dakota on the all night train in the late 1950's, just a fair amount of mail and express, go figure  .

Thanks for documenting this, going to order a TM-20 and give it a try. This is what I'm shooting for..........

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Tom L
Wellington CO

[SandyEggoJake]

Nice!  Was wondering if an asymmetric shaft length would still work with this frame.  Randy, you answered my question!  Doesn't seem you can get much better hiding those fly wheels, but painting would go a long way to camouflage.

The TM20 truck is a 32" wheel on a 6' 6" wheelbase.  The Bachmann is a 34" wheel on a 6' 8" wheelbase.  Because somebody will care.

I care!  I care!

@mmagliaro or others?  Given Bmann is out of the gen 2 replacement drives, ever have any luck sourcing a gear (brass?) to replace the gen 1 white gears?  I've a few of three of the gen 1 versions - luckily only one has a hitch.  But if a suitable gear replacement could be found....   

kicking myself I didn't buy the gen2 drive when it was in stock. 

 

[randgust]

OK, so after I put the Tomytec sideframes on it I decided they looked horrible.   I cut the lugs off the Bachmann ones and put them back on the Tomytec drive with Goo.  That's better.

With the same truck sideframes on, and the wheels painted, you could be 6" off instead of 2" off and couldn't tell.  I also pulled the traction tire wheelsets off and replaced them with solid as pickup is way more important than traction on this one and I have a huge pile of chassis parts anyway. 

The performance on this thing is just so much better with 8x8 drive than the Bachmann 4x8 design it's like watching a Roco GP40 vs. an Atlas GP40.   Even if you could get replacement Bachmann parts I wouldn't use them now.  Just no comparison, at least with the 1.0 version I have.

I've got to get some shots of the driveshaft before I put the seats back in.  Cutting the glass down as a shelf worked well, steps and underbody detail transplanting nicely too.   Everything you can see through the windows is now painted grimy black; motor, shafts, flywheels, frame.