UP 4-12-2 shell

[mike_lawyer]

Curious how you spliced two Mikado frames together ... I would like to try that someday.  Do you have any pictures on how you did it?

[rodsup9000]

Curious how you spliced two Mikado frames together ... I would like to try that someday.  Do you have any pictures on how you did it?

 Mike,

  I don't have any pictures, but I'll try to recreate on how I did it later this week for you.

[draskouasshat]

Well, as much as I love the UP 9000’s, the problem is our oversized flanges, especially on five and six-coupled locomotives. The more drivers, the bigger the dimensional bust.  Attempting to keep the driver size somewhat accurate just stretches the wheelbase and overall proportions of the boiler. The Con-cor 2-10-2 has an about 25’ driver wheelbase (3’ too long for a Santa Fe 2-10-2). The UP 4-12-2 driver wheelbase, with an extra driver, is 25’-8”, only 8” longer than the Con-cor 2-10-2. So adding a driver the the Con-cor loco yields a wheelbase of 31’-3”, even without adding the additional spacing between the first and second drivers like the prototype. This just forces the proportions of the loco to be way way off, imho.

I had made a feeble effort to build a 9000 4-12-2 four decades ago, and got the proportions right I think, see below,  but it forced me to use way undersized drivers off the MRC mallet. I had abandoned that project since I felt I couldn’t make the 67” drivered loco look “right” with 57” drivers.

In my opinion, the best approach to the “flange bust” is to make steam power drivers *slightly* undersize and the body *slightly* stretched, splitting the difference. This may work well for Pacifics and Hudsons, not as well for Mountains and Northerns, and even less well for 2-10-2’s and 4-12-2’s.
YMMV,
Otto K.

Although your math might be correct,  my model has a driver wheelbase of 2.279"=364.64"  that equates to a 30.38' driver wheelbase. Proto is 30'6" so mine is damned near spot and short for that matter which means theres room to slide the front driver forward and be extremely close.
The concor is the proper starting point for a 9000 class.

Drasko

[mmagliaro]

Drasko, I suspect yours worked out because the 2-10-2 has 63" drivers and the 9000 class has 67".  The slightly undersized drivers (for a 9000) help keep the wheelbase compressed.  I measure the Con-Cor at .393" (63" scale) on the tread (scale) and .443" (70.8" scale) across the flanges.    So the visual illusion is pretty darn good for a 67" driver.

Measuring the stock 5-driver Con-Cor engine, I get a wheel base
of  1.82".   4 gaps between drivers means we have  4 x (.443 + n) = 1.82   n is the gap they left between the flanges so the wheels don't hit each other.  That works out to only .012" !!
THAT's a big deal.  They pushed the drivers as close together as they dared to keep the wheelbase under control. 
That makes it all work out great for your 6-drivered version.

[Cajonpassfan]

Although your math might be correct,  my model has a driver wheelbase of 2.279"=364.64"  that equates to a 30.38' driver wheelbase. Proto is 30'6" so mine is damned near spot and short for that matter which means theres room to slide the front driver forward and be extremely close.
The concor is the proper starting point for a 9000 class.

Drasko

Actually, no, Drasko, my math was not correct, a major faux pas on my part (That’s an ef’up for you Texans).
The 9000 class driver wheelbase is 30’-8, so you’re pretty much right on. See plan from Linn Westcott MR Cyclopedia, below.
Max’s comments are pretty much right on as well. I’ll be looking forward to see your build.
With apologies,
Otto

[draskouasshat]

Actually, no, Drasko, my math was not correct, a major faux pas on my part (That’s an ef’up for you Texans).
The 9000 class driver wheelbase is 30’-8, so you’re pretty much right on. See plan from Linn Westcott MR Cyclopedia, below.
Max’s comments are pretty much right on as well. I’ll be looking forward to see your build.
With apologies,
Otto

No worries otto. I was certain i measured everything on the mech when i started it(still haven't finished it) last year. I couldn't believe i would have screwed the pooch and not measured like i usually do!
Hopefully I'll get the modeling bug to bite and get back to it soon.

Drasko

[mike_lawyer]

Mike,

  I don't have any pictures, but I'll try to recreate on how I did it later this week for you.

Thanks a bunch, that would be really helpful!