Locomotive Coasting

[Roy]

I'm not sure what is the best word to convey what I'm interested in. Some call it freewheeling, others backdriving. It was the thing that drew me to three-rail O gauge. Everything else out there, in all other scales, used drives that self-locked. I understand this type of drive prevents downhill runaways, but it's not like anything in the real world. Real trains, cars, trucks and buses freely backdrive. Anyone else interested in such drives, for their model trains?

[ScaleCraft]

Several ways...Lionel earlier steam were sidewinders, no worm to lock. Well seated units will almost run away if the grade is too much.
Worms....double lead will give you most of what you want, triple lead is crazy..sometimes NO feedback.

Single lead worms is what gives you worm lock, downgrades, slowing a long train, two or more power trucks fighting each other.

Of course there is HiF drives...

[jlong]

When I first got into postwar, I thought Lionel's double worm drive meant double lead worm drive for coasting action. I discovered otherwise when I got my first Turbine. LOL. I remember when the 3 rail industry introduced flywheels. It was like the cats meow for single lead worm drives. They do help. They just don't hold a candle to double lead worm drives.

[CWBurfle]

Here is some information I found online that I thought was interesting:

Imagine the gear ratio in the previous sign drive
is 60:1 instead of 5:1. If you turn off the motor
and try to drive the sign by hand, you’ll find it’s
locked in place. It won’t rotate.
The worm and gear mesh locks when you try to
back drive it. You can only rotate the sign by
turning the worm shaft. This is called a selflocking
gear set. Self-locking is caused by
normal friction in the gear set in high ratio worm
gearing.
As a rule of thumb, worm gear ratios over about
30:1 will probably be self-locking. Spur, helical
and bevel gears are not usually self-locking.

[Roy]

Several ways...Lionel earlier steam were sidewinders, no worm to lock. Well seated units will almost run away if the grade is too much.
Worms....double lead will give you most of what you want, triple lead is crazy..sometimes NO feedback.

Single lead worms is what gives you worm lock, downgrades, slowing a long train, two or more power trucks fighting each other.

Of course there is HiF drives...

Sounds about right, Dave. My only experience with two-start worms is Flyer S gauge. If you install ball thrust bearings, they will backdrive, but just barely. Lionel worms with three-starts, like the common Berkshire, backdrive much more freely.

In fact, the greater the helix angle of the worm, the easier the backdrive.

I was given Athearn Hi-F F7s as a kid. I suppose, with strong enough drive belts, and a large enough drive shaft, they might backdrive.

[Roy]

When I first got into postwar, I thought Lionel's double worm drive meant double lead worm drive for coasting action. I discovered otherwise when I got my first Turbine. LOL. I remember when the 3 rail industry introduced flywheels. It was like the cats meow for single lead worm drives. They do help. They just don't hold a candle to double lead worm drives.

Yes, I'm pretty fond of my '46 Berk. Another problem with backdriving these days, is the universal use of permanent magnet DC motors, with their characteristic "cogging" action. If I can, I'm going to try some different type motors.

[Roy]

I'm aware of one application, where a worm gear set is used in backdrive mode. Mechanical music boxes use a small fan, as a speed regulator. If you can see the gears, you'll notice there's a multi-start worm which is mounted on the fan shaft. The worm wheel drives it, and thus, the fan. The worm wheel is often part of the barrel which contains the main drive spring.

[ScaleCraft]

I was given Athearn Hi-F F7s as a kid. I suppose, with strong enough drive belts, and a large enough drive shaft, they might backdrive.

Except the primary goad of "backdrive" on worms is cogging or wormlock, elimination thereof.
Since HiF have no worms........

[Roy]

I was given Athearn Hi-F F7s as a kid. I suppose, with strong enough drive belts, and a large enough drive shaft, they might backdrive.

Except the primary goad of "backdrive" on worms is cogging or wormlock, elimination thereof.
Since HiF have no worms........

What I've found is that the larger axle pulleys will drive the "belts"(rubber bands), but the belts will slip on the motor driven shaft. Of course, you can give the belts enough friction to drive the motor shaft, by making the shaft larger. Great way to make a model rocket!