Re: HO Speed

Probably about walking speed; 3-4mph.

The prototype has to move the trains from zero to first notch balancing speed at a steady rate of acceleration over a period of time whereas our models tend to leap almost instantly to set speeds. For that reason, our models need to be able to move at barely perceptable speed and to increment in inperceptable steps.

I admit to less familiarity with Diesels, but for traction and steam, the answer is almost as slow as you want. "Run" does not necessarily require the continuous application of power. I have watched steam loco engineers inching onto turntables or up to a string of passenger cars at speeds much slower than a walk. The techniques was to crack the throttle to just get the loco or cut or cars or train rolling, and immediately shut off and let the momentum move the train, cracking the throttle or touching the brakes as needed to maintain the desired crawl. It was the same with electric traction - crank the controller to the first notch, just get rolling, then shut off and coast. I believe the same must be possible with a Diesel. Gary Q

First notch does not provide a given speed. Basically, think of the stroke of your gas pedal in your car divided into eight increments.

As alluded by other poster, you notch up to get your desired speed and back off, to coast.

If pulling a load and you are drawing a lot of amps but moving slowly, this is VERY bad for the traction motors. (Actually any motor, ever bind a piece of wood bad enough in a table saw to pop the breaker?)

When you work derailments, you inch cars along 24" blocks. I would have to say any speed is possible.

-- DW

Zero miles per hour.

A *LOT* enters into this, and it varies from locomotive to locomotive.

For Diesel-Electric and pure electric locos, among the things that need to be considered are:

1) Maximum CONTINUOUS generator current.

2) Maximum CONTINUOUS traction motor current.

3) Connections of motors (series, parallel, or series-parallel, in any combination).

4) Capacity of traction motor blowers (cooling fans)

5) Gear ratio (if any, some locos were 'gearless')

6) Wheel diameter

7) Control circuitry used.

Diesel engine power is not a factor, as most any locomotive can gernerate more current than the motors can continuously absorb, and hence at the SLOWEST continuous speed the Diesel will NOT be working to it's capacity anyway.

The slowest acceptable electric MOTOR speed comes down to the maximum CONTINUOUS electrical current the motor(s) (or their controls) can absorb without overheating. At that motor speed, the gear ratio and wheel diameter then determine the train speed.

But, even then, the power could be applied intermittently as has been suggested, allowing the train's inertia to keep it moving between applications. This would result in a 'modulated' (pulsating) speed, however, and not a truly continuous one as I think the original poster was implying.

And, yes, stalling or overloading the motors for any substantial length of time is *BAD*! There are types of motors that are designed for such service, but railroad traction motors are NOT of that type.

Dan Mitchell ============

At Zero mph, it (the train, not the locomotive) is *NOT* 'running'.

Dan Mitchell ============

Yeah, right.

Tell a dispatcher that.

LMAO

-- DW

LOL

Most GM's have a lowest continuous speed of 5 miles/per/hour, GE, Alco, MLW, BLW all were lower but I am not sure of the speed. Paul

That speed rating is for max power output, not for just drifting along. Big difference! Some locos like the DD40, have a minimum speed of 22mph or so and it would be silly to have the train run at that as a minimum speed, especially with some other restrictions like pulling a steam engine which limits the max speed to something much lower as well as speed restrictions which may limit the train speed to something like 5mph.

-- Why isn't there an Ozone Hole at the NORTH Pole?

It's mostly a matter of gear ratio and cooling capacity. Within limits, a buyer can order the loco with the specifications they need. A range of gear ratios are normally available, as are high capacity cooling blowers. Extra loco ballast can also be specified, increasing weight and traction.

That said, Baldwin, GE, and early EMD 'SD' locos, often tended have better 'lugging' ability (translated: slower continuous speed) than the later EMD products (especially). Despite thair many other problems, Sharks, Centipedes, and U-25C's and the like could really get down and 'dig in'. Many SD-7/9's could perform similarly, with fewer problems. That's one reason BN and some other roads kept a bunch of the old SD's around way 'past their time'. For slow heavy service, like pushing a hump yard, or ore trains, etc., they remained competitive or better.

Dan Mitchell ============

Very true. While it hasn't been explicitly stated, the content of this ead had implied "slowest continuous speed under maximum rated load".

With lighter loads, much slower speeds are permissable, as heating is much reduced.

Dan Mitchell ============