S4 and RS1 trucks

Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.

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S4 and RS1 trucks

Post by scottychaos »

Do the Alco S3/S4 and the RS1 ride on the same size/design of trucks?
or are the RS1 trucks larger?


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Post by txbritt »

I think the S3/S4 locomotives ride on the AAR type "A" switcher truck, and the RS-1's ride on the AAR type "B" road truck.


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Spotting differences

Post by jr »

There is a fairly easy spotting difference between the yard-switcher and road-switcher trucks. The yard-switcher has single coil spring pockets on either side of the bolster, and the road-swither has them in pairs.

Also somewhat more subtle, is that the switcher truck has a shorter wheel base, by something like a foot.


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Post by Allen Hazen »

Truck used on Alco S3/S4/S5/S6/T6 switchers (and most switchers from EMD, Baldwin, FM as well) has an 8 foot (96") wheelbase.
Truck used on RS-1, like truck used on FA, RS-2/RS-3 and later BB Alco roadswitchers, and on GE units from U25B through some Dash-7, has 9 foot 4 inch (112") wheelbase.
RS-1, like the Alco switchers, used the GE-731 traction motor: I don't know if it has the same dimensions as the GE-752 used on Alco (and GE) road power, so i don't know whether the actual trucks are interchangeable: they LOOK the same from the outside.

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Post by scottychaos »

thanks guys..
I was hoping they would be the same size! oh well...

USA trains is coming out with a 1/29 scale ("G scale") model of the S4 soon..


I was thinking of stretching the frame, scratchbuilding a new short hood, and making a RS1..
If the trucks were the same, it would be a fairly straightforward kitbashing job..but with the trucks that different, it wont work.. :(
oh well..

(although..I could maybe put aristocraft RS3 trucks on it!


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Post by ELSDP45 »

While the trucks on the RS-1 look like later AAR B trucks, from what I understand they are not interchangeable with anything but another RS-1.

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Post by EDM5970 »

I looked at drawings for 731s and 752s a few years ago, just to see if 752s would go under an RS-1 in it's existing trucks. Afraid not, the 752 is perhaps two inches longer betwen the axle centerline and support lugs, up against the bolster. (Which has made me wonder how people get 752s into Blombergs, but that is another story-).

The RS-1 actually used two different trucks, very similar looking, but the parts are not interchangable. The change occured around 1950, and seems to have coincided with the change of switcher trucks, from the Blunts (S-1, S-2) with 7x14 bearings to the equalizer truck (S-3, S-4) with 6 1/2 by 12 bearings.

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