Steam in reverse

Plus in those days, 20 m.p.h was considered high (and perhaps, reckless) speed.

Rusty

Can't speak for the larger scales, but they have been done in HO a couple of times, including a fairly recent model by Broadway Limited in the brass-hybrid system.

Kevin

You know what they say... desperate times call for desperate measures... 

Different types of steam locomotives will have different tracking characteristics when running in reverse.  4-4-0's can be quirky in reverse, but at least they don't have a trailing truck to derail.  A 4-4-0 running light in reverse isn't any more prone to derail than an 0-4-0 switcher running forward or backward.  Of course, a small switch engine won't usually be operated at high speeds due to the lack of a lead truck, not to mention the tendency to have smaller diameter drivers than road engines.  What upsets a 4-4-0 is running in reverse while trying to pull a train of substantial tonnage that is coupled to the front of the locomotive on a curve.  Since the pilot truck is set up to lead the locomotive around a curve in the forward direction, it has lateral movement to allow the front of the locomotive to move toward the outside of the curve, while at the same time applying pressure on the frame (in the direction of the inside of the curve) to keep the flange on the lead driver (on the outside rail) from digging into and climbing over the railhead.  This also keeps both sets of drive wheels in the best possible alignment with the curve.  However, when running in reverse, pulling a train coupled to the front of the locomotive, the train tends to pull the pilot of the locomotive toward the inside of the curve, which then forces the flange of the loco's rear driver that is on the outside of the curve into the head of the rail.  The flange tends to bite into and climb over the head of the rail, causing a derailment.

Now, I know someone will come up with a picture showing a 4-4-0 running in reverse with a substantial train coupled to the pilot beam.  I'm not saying that railroads never did it - especially logging railroads that were using whatever secondhand motive power they could buy cheap - I'm just saying that when doing so a 4-4-0 locomotive would have a greater tendency to derail, and heavier trains as well as higher speeds would magnify the effect.  The 4-4-0 3-point suspension combined with a swing-link or rocker style suspension in the lead truck makes the American a stable locomotive with great tracking characteristics when running forward, which is why they were so popular in the early days of railroading over less than perfect track.  But the same geometry that works to well running forward works against the locomotive when it pulls a train in reverse.

So, running a 4-4-0 light in reverse at high speeds while trying to catch opposing forces during wartime?  Yep, it works OK, they didn't derail.  The 4-4-0 in reverse will be more stable than an 0-4-0, since the pilot truck will tend to damp out the normal yawing forces whether running forward or reverse.  But, try that with a train that approaches the tonnage rating of the locomotive, coupled to the pilot beam, running in reverse around a curve... well, the story might end differently.

Steam locomotive suspension is a fun subject...

That is a fair point, Kelly.  If a 4-4-0 has a kingpin in the lead truck as opposed to swing links, it should work better pulling a train in reverse than one with swing links in the front truck.  My understanding about Forneys - and I'll be happy to be corrected if I am wrong - is that they had a kingpin in the truck as opposed to links, for that very reason.

I have read (and I apologize for not being able to cite the reference) that Matthias Forney originally intended his locomotive to run with the truck in front, so it would track like a normal 4-4-0... an early cab-forward if you will.  However, for whatever reason, nobody seemed to want to run them that way.  Of course, without evidence to refer to, that may well be an apocryphal tale.

Time to do some research on Forneys... 

Ya know, basically a SP cab forward IS an engine running in reverse.  The firebox is at the front, the smoke box is at the rear and the engines, themselves are "pushing", that is, the cylinders are behind the drivers.

Seems to me that any steam engine, particularly if it has a trailing truck, can "steer" itself in reverse as well as it can operating in a normal, or forward operation.  I can understand that an engine like a 2-8-0 or a 4-6-0 would not be comfortable running at speed without some sort of guide wheels or truck, but not so for more modern engines with trailing trucks for normal forward operations.

Paul Fischer

If you have ever attempted to drive a car REALLY fast backwards, you will find it nearly impossible not to crash or spin out.  The reason?  All of the steering geometry is set for the car to work properly going FORWARD, and counteracts itself while going backwards.  I don't know diddly about steam engine trucks, but I suspect in many respects it's the same basic principle. many items work better being pulled rather than pushed and vice versa depending on how they are designed.

I have yet to see a steam locomotive with a steering wheel.  They tend to follow the tracks left behind by the previous train.

Rusty

Hot Water:  What you say makes a lot of sense.  Never gave that much thought but I'm sure you're correct in that design of the suspension certainly affects riding/tracking qualities, and I suspect that they are concerned with operations in one primary direction.

Thanx for your expertise.

Paul Fischer

For more information on the problems with SP's Cab Forward problems trying to turn a trailing truck into a lead truck (especially on the MC-2 & MM-2), I suggest reading, "Those Amazing Cab Forwards" by George H. Harlan.  The MM-2 was delivered with a two wheel Hodges truck (normally used as a trailing truck), which had so many derailment problems that SP went back to Baldwin for a redesign.  Baldwin then built a four-wheel truck that was an actual pilot truck, as well as a new front frame section to accommodate the changes.  The parts were shipped to SP, who made the changes in their shops.

Very interesting book; I highly recommend it.