Thoughts on slow speed performance

[dragenrider]

I've been pondering how to post my thoughts, so I guess I'll go about it like this....

I have several Athearn BB engines which I have repowered with can motors, Ernst gears, and NWSL metal wheels. Their slow speed performance is superior to my P2K units. Also, the Athearn engines will crawl at an absurdly slow speed, similar to that of the P2K switchers. I've observed that the higher RPM of the Athearn engine causes less reaction to changes in power strength in the DC powered track. On the other hand, the P2K GP-9 diesels will noticeably change speeds.

That said, am I correct in my assumption that it is the higher motor RPM that is making the smoother run at low speed?

Is slow speed movement important on your railroad? It is on mine because it’s a mountain short line with an average mainline speed of 35 mph. Plus, I like slow switching.

Do other quality manufacturers such as Atlas and Kato have this excellent low, steady speed? I know Spectrum doesn’t, thought they come close.

If not, why don’t manufacturers reduce (increase?) their gearing ratio to make for smoother running units?

I’m just curious to what you have to say about this topic and my thoughts, so post away! [:P]

[Anonymous]

Good smooth slow speed operation is a mark of quality in locomotives. You want to be able to start a train from rest slowly enough to see the slack come out of the couplers and then the entire train slowly creep forward and then smoothly gather speed. That's cool. Running the throttle up to nearly full speed and have the train jump from stopped to 60 mph with a jerk spoils the illusion and causes gnashing of teeth and pulling of hair.
Gear reduction helps, and more is better. There are some physical limitations on the common "one-gear" schemes. On a steamer your gear ratio is 1:Nteeth on driver spur gear. "1" comes from the worm gear and you can't do better than that. The number of teeth on the spur gear is limited by the diameter of the spur gear, which can't be bigger than the drivers lest it hit the rails going thru a turnout. Without going to a second gear set that is all she wrote.
I have a Mantua Pacific which had pretty good slow speed operation in stock trim, slowest running speed was about 4 scale mph. I put the can motor conversion kit 812 into it and the slowest speed went way way down to 0.1 scale mph. Since the gearing didn't change, the improvement must come from the increased torque of the can motor over the stock open frame motor.



comm

[jrbernier]

A couple of thoughts:

1> Your engine has more torque due to that motor reving up in it's power band and the Ernst gears delivering the power at a lower RPM.
2> How much 'gear noise' are you hearing. My experience with Ernst gears was too much noise, even after cleaning up the gears.
3> The 'can' motor did not lower the top speed by itself? Most of my can motor repower jobs cut the top speed in half.
4> Most 'surging' on down grades is due to too much 'slop' in the worm(thrust washers fix that issue). I have a large 'fleet' of P2K GP's and love them. They do not pull as good as my old 'BB' repower jobs, but they look so much better!
5> High ratio gear sets are going to cost the manufacturer more(precision drive train production/assembly). Guess where the cost will be passed on! I for one would like to see HO engines set for a top speed of 65-70 mph(faster for passenger engines). Right now I can do this with DCC, so it has become a 'non-issue' for me at this time.

Jim Bernier

[Anonymous]

doesn't constant slow running lead to motor overheating????? easter

[selector]

Only when you are using a DC loco on a DCC-powered track, from what I understand. It is particularly bad stopped, but running at moderate speed makes it run quieter and cooler.

[AntonioFP45]

Good Thread!

One issue that many of us that enjoy prototype style performance is the "smoothness" of taking off without "jerking" or "hesitation".

I'm repowering some of my units with Mashimas. On another thread, Don Gibson gave some good info regarding Mashimas and Helix Humpers. While the Mashimas are quieter, however, the Helix Humpers allow a higher top speed.

I've been considering using the Helix' Humpers on my Athearn Cowls as the prototypes reached 90 mph in western U.S stretches. In my case I would like my passenger and "fast freight" locomotives to be able to reach 85 m.p.h scale top speed. Freights at 65 m.p.h. At the same time, I want my units to be able to crawl at 3 scale mph after a smooth take off.

O.K! Go ahead and say it: Dude! You sure are asking a lot! Ain't ya?!

If the Mashimas can allow Athean FP45s and P2K E7s to hit 85 scale mph, then I would go with the Mashimas, hands down. I realize that the gear ratios in the trucks are the major factor. I would prefer Mashimas as the current draw is very low. According to a friend of mine, Kato and Canon also make excellent motors that allow locomotives to "creep".

10-4!

[Virginian]

Most motors list the maximum RPM and from that you can figure the top speed. With worm gears the potential is there by changing the pitch instead of just the gear sizes, but I have never looked into it. I don't know if NWSL does any of that or not. I have seen steamers with three gear trains, and it shouldn't be that much more expensive either.

[nfmisso]

QUOTE: Originally posted by dragenrider

If not, why don’t manufacturers reduce (increase?) their gearing ratio to make for smoother running units?

LL P2K SD60 was geared for about 60 mph at 12V (vs 100-120 for recent Athearn and most others), and almost everybody complained......

[Anonymous]

With DCC all you have to do is set your loco for 128 speedstep and you'l be crawling away in no time.

[tstage]

If you have a switching yard?...crawling is just the COOLEST!!!

Tom

[dragenrider]

QUOTE: Originally posted by jrbernier

A couple of thoughts:

1> Your engine has more torque due to that motor reving up in it's power band and the Ernst gears delivering the power at a lower RPM.
2> How much 'gear noise' are you hearing. My experience with Ernst gears was too much noise, even after cleaning up the gears.
3> The 'can' motor did not lower the top speed by itself? Most of my can motor repower jobs cut the top speed in half.
4> Most 'surging' on down grades is due to too much 'slop' in the worm(thrust washers fix that issue). I have a large 'fleet' of P2K GP's and love them. They do not pull as good as my old 'BB' repower jobs, but they look so much better!
5> High ratio gear sets are going to cost the manufacturer more(precision drive train production/assembly). Guess where the cost will be passed on! I for one would like to see HO engines set for a top speed of 65-70 mph(faster for passenger engines). Right now I can do this with DCC, so it has become a 'non-issue' for me at this time.

Jim Bernier

Jim, in answer to your questions:

I do have a lot of gear noise at first. I go to a lot of trouble to make the gears turn smoothly before I install the motor. That includes the thrust washers which I recently discovered courtesy of this forum. The gears quiet down after about three hours of running.

The can motor cuts the low speed in half, but the Ernst gearing cuts it in half again. So, they go really s-l-o-w....

[:D] As a matter of fact, I've gotten bored with my switch engines and had to speed them up to get all the switching done! [:D]

Nothing looks better than a small freight train crawling accross a bridge or easing up a steep mountain incline. Woo-woo!!!!!

[Jetrock]

Slow speeds are about the only way to increase the apparent size of a shelf layout--since my layout is all technically in "yard limits" I try to limit speed to 15-25 MPH at all times. It's kind of nice having a 12 foot long layout with engines traveling slow enough to take a minute or so to travel from one end to the other!

I have been considering some repowering units for my Athearn BB fleet--sounds like it will be worthwhile. My biggest challenge will be finding repowering units that will allow my single-truck Birney trolleys to travel at 15-20 MPH top speeds and still be able to make it over my Insulfrog turnouts--I'm thinking a big flywheel might be the answer.

[dragenrider]

It's well worth the trouble. The high torque and flywheels make the engines glide on over frogs and bad spots. This is even more true with the motor's higher speed and low gear ratio versus a slow speed motor which is more likely to stall out.

[Don Gibson]

It seem's there are two 'schools' of thought.

Take the Proto 2000 SD-60 with approx 50 mph top speed @ 12 V.:

One modeler (I know well) loves this engine for it's smooth / realistic start's and stops, and another (I remember well) who complained about it's speed and gutted the mechanism's on his two, to run as dummies behind something to go faster.

Does the the typical 'Defense' is "It's my RR, and I can do what I want", while it apply's, is it really justifiable? - any more than "She's my wife, and I can hit her If I want?". What is 'Good Practice'?

Wthout editorializing: one of the above get's his thrill's from running things fast, and the other thinkis running in a circle every 6 - 12 seconds (av. layout), is boring.... and, of of course

"it's THEIR layout"

[dragenrider]

It is your railroad, and each of you have your way of doing it. Nothing wrong with that. That's where you may know something I'd like to learn!

I like the comparison and contrast of ideas which spark the ol' grey matter in new directions. That's why I enjoy the give and take of the polite members of this awesome forum. I learn a lot from it...like about thrust washer several months back.

[dinwitty]

I've mentioned it before, but I am glad the model makers have listend to the demands and made quality models that perform the way it's meant to run. Not as a toy train running around the christmas tree.

I have always been the slow speed performer guy as I tired of switchers zooming 90 miles an hour.
I remotored/geared a mantua 0-6-0, its slowww, and it Pulllllls...
done this to other engines.

[ereimer]

QUOTE:
Does the the typical 'Defense' is "It's my RR, and I can do what I want", while it apply's, is it really justifiable? - any more than "She's my wife, and I can hit her If I want?". What is 'Good Practice'?

bad analogy [:(!]
doing whatever you want on your model railroad really doesn't affect anyone else . if you want to go from stopped to the speed of an F-16 on full afterburner in a heartbeat , go for it , just don't do it on my railroad . is it justified ? it's your railroad , who do you have to justify anything to ?

as for hitting your wife , well i think we all know better . pretty hard to find any way to justify hitting anyone

[samgolden]

When I install a decoder in a loco, after I check out how it runs, the next thing I do is program the Min Start Voltage. With the shell off so that I can see the driveshafts turn, I play with the programing so that on #1 on the throttle setting, the drive shafts turn so slow that you can count the reveloutions. I have done this with Athern BB, Life Like P2K, Bachman Plus, and others. My grandson has a LL train set loco, that I have programed like this, except no drive shaft to watch, and that will even crawl.
However, the newer "quiet / silent / high frequency" decoders, I have more of a problem with them because of the Kick Start feature, in order to get them moving in the first place. I havent been able to get them to start without jumping, but after they start they will still crawl.
After I get the min volts set, I then set the max volts, to limit the top speed if I think it goes too fast. Mostly on the Athern BB.

sam

[rtraincollector]

When I was younger I thought it was cool to see how fast I could get the train to go on the layout without jumping track . I would run a 2359 magatraction B&M with 6 to 8 cars behind it to the point the caboose was holding on for dear life on the O27 curves on a 5 X 10 layout it was full speed ahead. Now I like to get a train up and running and to see if I can make it look like its really pulling out of the yard or into the station. I also liked to make as long as a straight away as I could on the floor and see how many cars I could get the engine to pull think I rem 37 one time but it was spinning lol

[johncolley]

Another thing to remember is friction and inertia. different motor/gear trains need more or less voltage to overcome standing and begin moving. how warm is the grease, how broken-in are the units? I have a pair of BLI e-7's bought about a year apart, that cv's are set the same but they act differently because there are a lot of "ton-miles" difference between them. Before they are fully warmed up they surge aroundthe stall point. Once warmed up I can crawl into the engine service area or ease onto coupling to the train.

[Anonymous]

"doesn't constant slow running lead to motor overheating????? easter"

There are two things that limit the current flow through a motor. One is the impedance (resistance) in the motor windings. This is what limits the current when it's stalled out. The other is the back EMF generated by the motor when it's running. Under very slow speed operation the back EMF drops, so the current flow goes up, which in turn increases the heating of the motor. Two things you can do:

1. Run the locomotive faster.
2. Run the motor faster by gearing it down lower to get the same locomotive speed.
3. Change the otor to one designed to operate at a slower speed.

If you have problems with your motors getting hot when running them slow, then it's time to gear them down and / or replace them with a slower-running motor.

The effects of a flywheel are amplified the more you gear down the motor. The smoothest running one will be one geared WAY down, with a high-speed motor and a flywheel on it. Gears can also be noisey...... It's a trade-off.

Mark in Utah