Bachmann USRA heavy mountain vs J?

[daniel_leavitt2000]

Can anyone compare the driver size and wheelbase of the Bachmann heavy mountain and J? The J wheelbase and size is just about perfect for the B&M R1 mountain, but the chassis is too tall and would not be easily milled. I have a light mountain and the wheel size and wheelbase are too small.

[reinhardtjh]

Daniel,

The Light and Heavy Mountain  have the same driver size and wheelbase.  Just different sized boilers, etc.

As measured by my semi-trusty Chineses digital calipers and 56+yr old eyes:

.	Actual Inches	.	.	.	Scale Inches	.	.	.
Locomotive	Driver Size (rim)	Driver Size (flanges)	Driver Spacing	Driver Wheelbase	Driver Size (rim)	Driver Size (flanges)	Driver Spacing	Driver Wheelbase
B&M R-1 Class	.456	.456	.481	1.443	73	73	77	231
Berkshire/Kanawha	.408	.460	.480	1.440	65.3	73.6	76.8	230.4
Light/Heavy Mtn	.391	.429	.460	1.386	62.5	68.6	73.9	221.8
N&W J Class	.413	.453	.470	1.406	66	72.4	75	224.8

R-1 class specs taken from the http://www.steamlocomotive.com/mountain/?page=bm page

I scanned my loco database and the Bachmann 2-8-4 Berkshire/Kanawha is the closest to the B&M R-1 class of the models I have measured.  At least in driver size/spacing/wheelbase.  I don't know about boiler size and mechanism sizes and you would have to modify the pony and trailing trucks.

Of the two that you were asking about the J is the closest of the set in overall wheelbase, about a scale 7" short. The driver size with flanges taken into account is just about spot on.

[jbcz]

Daniel

I went back and looked at my R1A-C derived from the Bachmann J Class to check some of the dimensions.  I laid the locomotive on the R1D plans that were provided in Model Railroader some years ago.  The model shown in my photo below is off by a “foot here and a foot there” using the 4-8-4 shell as the basis.  I did some surgery with files, knives and razor saw to achieve the overall look of the R1 Boiler/Cab.  The overall length and proportions seem OK.  The drivers look a little small and it is a little tall (about 10” or so).   But as folks have said, these things are a compromise and it’s the overall impression that counts. 

I’d suggest that you stick with the 4-8-4 shell and J Class as you can keep the nice running mechanism and good electrical connectivity.  I did have to do some filing on the J mechanism to get the shell to fit but I did not need and special tools.  With the J Class you get a tender that is close in dimension to the B&M R1A-C after you do a little surgery to clean off the streamlining.  I don’t have the great skill that others have so getting a reliable locomotive that comes close to what I wanted was worth it.  There was nothing fancy here, just the J Class mechanism/tender, 4-8-4 boiler shell, and 4-8-4 pilot.

Bruce

[daniel_leavitt2000]

Bruce,
That is about what I would like to do with my engine. Can you show me where you shortened the shell? It looks like you lobbed off a few feet of the cab, but I don't know what you did with the boiler.

[jbcz]

Daniel

Here's what I did:  took 3/32 off the cab rear, 4/32 off the cab roof, 4/32 out of the center of sand dome, 6/32 out of the firebox, moved the steam dome rear-ward, filled in the forward cab windows and filed to window area to the proper look, filed the "walkway like" structures off the mechanism sides, and filed the mechanism front to fit the 4-8-4 pilot.  On the tender I took 4/32 off the top of the coal bunker, and took the streamlining off the water tank making sure to get the angle right on the tender sidewall.  I am still not totally happy with the boiler because I did this before MR released their archives on disk.  My original work was done from the B&M lines drawings available on the net.  Thus, my steam dome is too far back.  The model is slightly oversize but as you can see from the line drawings the proportions are pretty good.  I forgot to say that I used the Minitrix 4-6-2 trailer truck. 

BTW, I have done two 4-8-2s from the Bachmann 4-8-4 using similar surgery. On the 4-8-4, I shortened the rear of the mechnism by enough to fit the shortened boiler and used a Rivarossi tender.  When I took the left traction tire off and direct connected the tender to the right boiler side I ended up with a real nice running loco.  On my pike, it never stalls in the yards or across switches.  Here are photos of my two models.  Again they are compromises because heir drivers are too big. For fun, I did two paint schemes.

Bruce

[jbcz]

Photos did not post.

[jbcz]

Photos did not post.  here's the second.

[daniel_leavitt2000]

Did you angle out the ash pan? The stock one looks flat but yours is sloped. I can't tell if that is paint or surgery.

[jbcz]

I did change the angle.