Spectrum USRA Heavy Mountain

[Dave V]

Do you realize that the Heavy and Light Mountain both have the same driver size and wheelbase? The measured driver size at the wheel is around 63" and 69" at the flange. They represent 69" drivers because the flanges would interphere with each other if they used a 69" tire size. The two models use different frames but that is only because of the change in where the DCC was to be mounted. they eliminated the pocket in the frame and changed the motor mount to accomodate the current can motor instead of the older open frame motor.

Tony,

If this is the case (and I believe you), what made the Bachmann heavy 4-8-2 such a better puller than the light 4-8-2?  I have the light version, bashed into a Pennsy M1...  I found it disappointing at pulling and infuriating due to the valve gear's propensity to explode randomly.

[Norway2112]

The Heavy mountain has the decoder in the tender, so the "decoder pocket" in the Light mountain mechanism is filled in solid with metal frame.  In addition to that the entire boiler shell is metal on the Heavy Mountain as where the Light Mountain shell is plastic.  That is the biggest difference and reason for better pulling power.  The Heavy also has a better motor in it.  See spookshow's website for photo comparison of the two mechanisms.

[SkipGear]

Tony,

If this is the case (and I believe you), what made the Bachmann heavy 4-8-2 such a better puller than the light 4-8-2?  I have the light version, bashed into a Pennsy M1...  I found it disappointing at pulling and infuriating due to the valve gear's propensity to explode randomly.

The heavy frame is different, although designed similar so I bet they got the driver bearing pockets fixxed this time around. Besides that, the Heavy Mountain has a die cast metal boiler. It is much heavier than the light mountain because of that and the fact that it doesn't have the pocket milled out of the frame for the decoder.

Mark (spookshow) and I talked back and forth a bit about the differences when they came out as he originally though they were the same frame so I have picked one over pretty good. I have also been scrounging for the C&O versions as they came with single arm crosshead which I need to build a few B&O Mountains.

[mmagliaro]

Has anyone weighed these two, to get their actual weight in grams?

[squirrelhunter]

Skipgear- No worries. The FEC didn't help any of us rail fans or modelers out by giving their 4-8-2 nice easy to remember classes, and made it even worse by having three groups, each heavier than the last, with the middle group having the biggest drivers.

One project I want to try is to get a Kato GS-4 chassis,  2 bachmann light 4-8-2 shells, and kitbash a MoPac MT 75 class. This site http://www.railroadheritage.org/index.php?P=FullRecord&ResourceId=1346 has a good roster shot and short summary of how MoPac rebuilt them from regular USRA light Mountains.