Smallest Diesel in General Service Today

I can't say they're the smallest out there but a lot of the older diesels are still out there. GP7s, RS3s, etc. These models are available for a decent price and able to navigate tighter curves.

What's your minimum radius?

Atlas SW(9) models.   With Lionel (TMCC) they can be used as multiple units.

@texgeekboy:

I have a long oval, independent loop on my medium-sized layout with one siding and all 036 curves for my freight operation. So I have to use short diesels to run an 8 or 9-car freight train.

My trains are 1950s to 60s era. So I have a GP7, a GP9, and a GP30. They are all Lionel Legacy, 4-axle road switchers and work perfectly for me.

But if you’re modeling present day, there are a number of GP20s, GP30s, and GP35s still in use today.

Start following this thread. Plenty of great suggestions from that bunch.......

For that type of distance you are probably not going to see small units being used.  500 miles will be part of a larger train so that's main line locomotives with 4000+ hp and big fuel tanks.  You might see an SD-60 out there hauling at this range, but I think that's about the smallest in modern day service.  If you want small machines for local or regional service, the sky is the limit.  I would start here.

I still see old GP38-2's as a trailing unit in use on the Moffat subdivision of the UP. That's the smallest unit that still runs mainline 500+ miles.

@texgeekboy posted:

I'm wondering what model of diesel, that's not very long, gets used frequently (not necessarily the most) to move consists a fair distance, say 500 miles or more in the present day.  I want to buy some model diesels that are similar to the real ones.  My layout will be small, and I'm looking for small, but realistic, trains.

Yeah, I know that multiple diesels get hooked together, but I'm ignoring that for my RR for now.

If your layout will be small, why the “500 miles or more”parameter? 🤔

@Yellowstone Special and the rest,

Yeah, my question wasn't stated as well as I wanted, but I couldn't figure out a better way.  My future layout won't be huge (I'll be lucky to get a 12x15 with an access area in the middle).  While I won't be modelling a long haul line, it's nice to imagine it is.  While I would like O31 curves, I know I'll need to get O36.  I started looking at the various GP models, and there's a Lionel GP-20 coming later this year that will satisfy my needs.  It appears that all of the smaller GPs are around 14 inches.

@BillYo414,

I actually acquired 2 RS-3s at a recent auction but haven't received them yet.  Were they used for freight trains?  They kinda looked like big, glorified switchers to me, but I know nothing.

44-tonners all the way, though they would never make it 500 without huge fuel tanks.

@texgeekboy posted:

I actually acquired 2 RS-3s at a recent auction but haven't received them yet.  Were they used for freight trains?  They kinda looked like big, glorified switchers to me, but I know nothing.

The RS-3 was sold as a "Jack of all Trades" kind of locomotive.  They were used in switching service, freight service, and passenger service if equipped properly.  Most spent their days in freight service.  One of my favorite photos of the RS-3 is during the Penn Central era where a GG1 is leading three RS-3s on a long freight train.  Just an interesting mix of power.

As to smaller diesels in general service today, the RS-3 is not very common.  Most saw their last miles in the 1970's.  Alco power in general just isn't that common on today's railroads.  A few still operate for short-lines and tourist service.

Most diesel locomotives in service today for freight service would be EMD or GE power.  What constitutes a switcher anymore is anyone's guess.  One can find EMD SD40-2s doing yard duty while MP15 (the modern equivalent of an SW unit) can be found pulling mainline trains.  The good news for us as modelers is that it really doesn't matter what we use for mainline operations as long as we enjoy it.

Like others have said, GP units would be a great start if you are looking for prototypical realism.  GP38's and GP40's are still very common in service after a few rebuilds.  They have a fairly short wheelbase.  More modern wide cab GP60s are also a possibility.

Once you get to the short-line roads though nearly anything goes including former passenger locomotives from the F7 to the F40PH.  Maybe not 500-mile-long roads, but certainly interesting operations.

@texgeekboy for what it's worth, consider a divider on the layout. It depends a lot on the shape of your benchwork but dividers can really make a layout seem bigger by hiding the train for a minute.

Best of luck!