K4- Bachmann vs. Trix

[dougnelson]

The Bachmann looks pretty good awesome to me. 

The circa 1969 Trix model had its cab enlarged to fit the motor.  Bachmann smartly put the motor in the boiler and left the cab open to allow adding an engineer and fireman.  When I upgraded my Trix K4 with a Hans Starmans tender drive, one of the benefits was to be able to shave down the size of the cab and model the open cab - with a backhead from the Kato Mikado and the addition of the crew:

[mmagliaro]

The Bachmann wheels are 84 scale inches or .450 inches. That's not counting the flanges.

Shocking!  I never would have thought they were that big looking at them compared to the Kato C55 photo.
Thanks for measuring.

[eric220]

Something that didn't immediately strike me, I mentioned that I scaled those drawings off of the locomotive, cab to smoke box. The tender lines up precisely to the drawings. In other words, according to the measured drawing that was posted, the Bachmann model coupling distance is exactly to scale.

[wcfn100]

  Also, someone made a comment about the curvature of the cab roof; it seems to match quite nicely.

Yeah it does.  Maybe they used that drawing to design it.

I was comparing it to the prototype.

Jason

[eric220]

I was comparing it to the prototype.

Please do! I was amazed at how well the model matched the measured drawings when I superimposed them. As I said, it was far more accurate than I gave Bachmann credit for before I did the comparison. If you can show similar perspectives of the cab roof between prototypes and the model and measured drawings that show that they're significantly different, I for one will happily concede.

[wcfn100]

If you can show similar perspectives of the cab roof between prototypes and the model and measured drawings that show that they're significantly different, I for one will happily concede.

Sure, right after you explain how drivers that measure larger than the prototype and are spaced farther apart than the prototype, somehow line up perfectly with the drawing.   

Of course, I'm probably more shocked than Max if the Bachmann driver are really 84", they sure don't look it.


Jason

[eric220]

Sure, right after you explain how drivers that measure larger than the prototype and are spaced farther apart than the prototype, somehow line up perfectly with the drawing.   

Of course, I'm probably more shocked than Max if the Bachmann driver are really 84", they sure don't look it.

For what it's worth, my measurement of the driver tires without the flange is 11.5 mm or around 72 scale inches. Granted, the battery in my calipers was dead, so that's a visual reading of the measurement, which yields several scale inches of margin for error. Still, that would explain it.

What does that have to do with the cab roof? 

[reinhardtjh]

The Bachmann wheels are 84 scale inches or .450 inches. That's not counting the flanges.

Shocking!  I never would have thought they were that big looking at them compared to the Kato C55 photo.
Thanks for measuring.

That's a typo on the scale size.  0.450" is 72" scaled up.

Sure, right after you explain how drivers that measure larger than the prototype and are spaced farther apart than the prototype, somehow line up perfectly with the drawing.   

Of course, I'm probably more shocked than Max if the Bachmann driver are really 84", they sure don't look it.

Jason

See the previous. Josh typo'ed (or whatever) the conversion.

I have a stock Trix K4, Kato C55 and Bachmann K4s.  Here are the numbers according to my 55yr old eyes, an Optivisor and my trusty slightly better than the Harbor Frieght $10 digital micrometer:

		Proto Driver					Model Driver
Name		Dia	w/flange	Spacing	Wheelbase		Dia	w/flange	Spacing	Wheelbase
PRR Proto		80.0		83.0	166.0		0.500		0.519	1.038
Bachmann		72.6	80.6	83.2	166.4		0.454	0.504	1.040	0.520
Minitrix		75.2	87.0	90.6	181.1		0.470	0.544		1.132
Kato C55		74.9	82.9	88.1	176.2		0.468	0.518		1.101

As you can see, the Bachmann K4 drivers are undersized, although with flanges they are just a tad over.  Their spacing is also only microscopically over but far closer then either the Trix K4 or Kato C55.  Total wheelbase of the PRR K4s was 13' 10" or 166".  The Bachmann is clearly the closest in overall wheelbase while the Trix is nearly 15" too long.

It's all a game of tradeoffs.  Bachmann went undersized in the driver to make the total wheelbase come out right.  Trix made a different choice (of course, their flanges were huge). Kato doesn't really count since it wasn't meant to be a K4s model in the first place. it just works out to be close.

Y'all can argue about the body I didn't measure that. I'm happy enough.  I just have to decide if I want to risk one of those mis-wired/narrow gauged L1's at FDT or consider bashing a Bachmann K4s shell later on (I think now I'll turn my GHQ L1s kits into I1sa's since they're oversized anyway).   

[wcfn100]

Okay, thanks for the correction, that's definitely closer to what it looks like.

Jason

[Teditor]

Bachmann's biggest mistake with the K4s is producing a locomotive that so many wanted to be perfectly accurate, that would run on 9"+ radius curves and cost no more than $100.00 US with DCC and sound.

Try buying one in Australia and you will see what value for money really is, to get one here will cost around the $300 to $400 (Aus) mark.

I would love to have some of these brilliant running inaccurate models but I don't have a house or body parts to sell.

Can we please have a Spookshow comparison of a stock Minitrix and Stock Bachmann?

Ted (Teditor) Freeman
From the Land Down Under.

[robert3985]

LOL!!!  This puts to rest the subjective views of everybody (myself included)!  Yup...SPF's should be very happy indeed with the Bachmann K4!!  Multi-kudos to Bachmann for this beautiful, properly proportioned engine!!

Cheerio!
Bob Gilmore

[dougnelson]

Another nice feature of the Bachmann K4 is that the space between the frame and boiler is open as it is on the prototype.  This is a detail that Bachmann apparently took some care to achieve.

My Trix K4 can't do this:

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[chicken45]

I actually measures it with a scale ruler, too. 7 feet. I may have misrea me the calipers, but I swear, 7 feet.

[mmagliaro]

Okay, that makes a lot more sense.  The Bachmann drivers are only .012" inches smaller in diameter than
the Kato c55.  I think the reason the C55 drivers look so much bigger, and better honestly, is the thick
wheel rims on the Bachmann drivers.  Look at the comparison photo again and you'll see what I mean.

They did the same thing on the Berk.  Those heavy rims make the wheel centers too small, with spokes too short,
and the overall look of the wheel is smaller.

Hey... this is the choice they made.  I still think they did a much better job than they did on the Berk and there's no denying
that a lot of these are coming through that run and pull well.    I am not happy with some of the design choices they
made, but they did come out with a K4 that is better than any other commercial one that has ever been made.

[chicken45]

From an "armchair modeler/Monday morning QB" perspective, what would you do differently, @mmagliaro ?

I'm forced to state that this is for discovery and curiosity and not to pick apart Bachmann's decisions.