Intermountain F3A - Will The Shell Fit on a Different Chassis?

Model Railroader General Discussion (Model Railroader)
1

I have complained about this before. The Intermountain F3A runs way too slow. I have four of these locos. I don’t know for sure what the problem is, whether it is the gearing or, perhaps, the decoder. But, I suspect the gearing because I use different decoders in these locos, some factory installed and others after-market.

So, my question is, will the Intermountain shell fit another brand of chassis?

Rich

2

It should fit on the stewart chassis…

3

What he said. Intermountain manufactured their F unit shells to fit the Stewart/KATO F chassis. You see, the IMR F shells were out on the market well before they had a chassis/motor unit available for them, but still wanted to offer them for sale. So for that interim, they recommended hobbyists obtain a Stewart chassis and mount their IMR shell on it. Eventually they developed their own chassis, which by all reports has been a very good one. Rich’s comments are one of the very few I’ve seen that stated unhappiness with the IMR chassis.

4

Excellent. Thanks, guys, I will try the Stewart/Kato F chassis.

Rich

5

Sounds like a decoder issue, because my moderately sizeable fleet of Intermountain F units all run just fine - on DC.

And as others have said, the shell works fine on the Stewart drive.

Sheldon

6

What sort of test equipment would I need to determine the scale speed of one of these Intermountain F3 locos? My four IM locos run a heckuva lot slower than any other of my many passenger diesel locos.

Rich

7

Rich … Your problem perplexes me. … I have two Intermountain F-units which I regularly run with other makes of F-units. I don’t have your situation with mine. … Perhaps you should contact Intermountain with your question.

I did install an Intermountain F7 B-unit shell on an Athearn non-powered F7 chassis. It required some cutting and filing inside the shell.

8

I have lived with this problem for quite some time. At one time awhile back, I did call Intermountain and they claimed that the slower speed was normal as the gear ratios were set to simulate slower speed F3 locos. Dunno, they just seem too slow for me.

What test equipment would I need to conduct a scale speed test?

Rich

9

Gidday Rich, A watch with a second hand and a tape measure.
Here’s a link to some tables that I find of use including Table 2 Scale Speeds.
http://www.awrr.com/scalecharts.html

EDIT: After a very quick look I see that EMD offered the F3 with different gear ratios, the variation in top speed from 55 to 102 mph.

Cheers, the Bear.[:)]

10

I suppose I could be content with the slower speed. OK, I will run some speed tests tomorrow.

Rich

11

You might want to look into replacement gearsets to get the speed you want.

12

I ran some speed tests and started a new thread with the results.

Rich

13

This would depend on the age of the engine of course, but have you cleaned out and reapplied all lube to the engine?

If this is a newer engine with few hours on it, I’d contact Intermountain for help if I were you.