[StanleyAmes]

Over in the rolling stock forum a topic was getting buried in the K-27 thread and I thought I would move it over here as it allies to all of us in all the various scales.


Incidentally, I haven't noticed their Shays or the other geared locos running at 30 MPH


Mark a most excellent question as the Shay is a model a lot of us can relate to. Because it is such an interesting question I have started a thread devoted to this topic.

The topic is what is the top speed we desire in our models.

The topic is an outgrowth of a topic on the K27 which has a prototype speed at 14.4 volts and a much faster than prototype speed at 24 volts.

The Bachmann shay is perhaps a good place to start this discussion because so many of us have this locomotive on our layouts.

What is the top speed of a Bachmann Shay at 24 volts DC I have never run one up that fast so I have no idea. Might be worth collecting the top speed of various locomotives as a reference point to help the community decide which speeds they prefer.

Both speed and voltage needs to be a part of this as many of us also operate at lower voltages (for example 14.4 volts for several RC users) so when one talks about prototype speed one also needs to talk about at which voltage this prototype speed should be at.

Having a desired speed range and a dialogue on what we truly desire would I think help all of our manufacturers. Such a consensus would be of great benefit to the hobby.

Myself I like slow speed operation and most of the time the locomotives run slower on my layout then most other garden railroads I have visited. That said I also have a C16 that is way to slow at the voltages I prefer to operate and because of this the locomotive is not often out on the layout. So perhaps 24 volts is not the proper place to look for prototype speed.

There are a lot of pros and cons on this as different speed settings also implies more difficulty in running several locomotives together on DC layouts but I think it still is a useful discussion.

Maybe a good compromise is 18 volts DC for the prototype speed setting. That would allow those that like a faster locomotive to rev it up in voltage while those that like slower locomotives to still have a wide range of prototype speeds.

Perhaps this is also an area that Garden Railways might want to consider doing an article on.

Stan Ames
http://www.tttrains.com/largescale

 

[stanman]

If my memory is correct (ha!) I read somewhere - perhaps the booklet from Bachmann that came with the Shay - that the top speed of the prototype was 19 mph.

If that's the case, this is equivalent to a 1:20.3 locomotive traveling 83 feet per minute, or about 7 feet in 5 seconds.

I run mine much slower; think it looks better...

 

[ralphbrades]

Oh dear...

The NMRA (an AMERICAN ORGANISATION) is once again attempting to tell the world how it should run its model railways. Well if you want to know I use 16mm scale and 13.5mm scale neither of which exist in the NMRA Diktat, (thank GOD).

I run my 16mm scale locomotives at a scale 10 to 15 Kph on a scale 0.75 chain curve, and I have run my 13.5mm scale locomotives at a scale 70 Kph on a scale 3.5 chain curve respectively.

Which is how the originals operated.

regards

ralph

 

[BigDigger]

Oh man, thanks for bringin up the question. There should be no maximum speed. Doing prototype speed chugging around a layout is boooooring/DesktopModules/NTForums/themes/mls/emoticons/doze.gifzzzzzzzz. And for me the Kay has too much stuff on it, maybe something in a torpedo shape that's rubberized so when it flies of the jump at the end of the track I can go do it again real fast without have'n to fix it.

Now that would be cool!

Lookin forward to that article in Garden Railways /DesktopModules/NTForums/themes/mls/emoticons/w00t.gif

David

 

[ralphbrades]

Mr Ames.

Having sat down at my nice comfy chair, in my nice warm office, with my nice mug of coffee...

"Please Allow Me To Introduce Myself".....

I find your arguments on the subject of voltage relating to speed to be specious at best. While it true that an electric motor of the commutator type the increase in Voltage does provide an increase in revolution -this is by far and away not the whole of the story.

Consulting the catalogues for the suppliers of the motors that I use I find that the most common one that I use has a MAXIMUM voltage of 6 Volts with a draw of 29 Amperes at a rated shaft speed of 9,000 RPM. Following the manufacturers sequence I find the same motor casing and shaft size but at 12 Volts, 18 Volts, and 24 Volts.

The windings on the rotor dictate the maximum voltage of the motor just as the thermal decay point of the insulation (class "K" is typically 130C) on the windings dictates the absolute Amperage, (I squared R).

This leads to the problem of cooling the motor -I use a fan cooled system for my locos and forced liquid immersed one for my commercial designs.

While for reasons of efficiency it is better to run a motor at high speed this imposes strain on the gearing leading to a rise in wear directly proportional to the square of the angular velocity.

Thus a good designer will arrange for his Voltages to be within the limits of the insulation, the heating effect of the current to be dealt with, and the angular velocity of the gearing to be within acceptable wear parameters.

Your arguments relating to "The Correct Voltages To Be Used" as thus invalid -unless everyone is using: the same motor, with the same gearing.

My current model that I am building has motors designed to take 12 Volts at 12 Amperes. This will involve me designing a PWAM driver circuit based on 24 Volts electronics -a departure from my normal 12 Volt electronics for the board. In my 13.5 mm scale models I have taken the step of providing separate power supplies for the electronics and the motors. Sealed Lead Acid batteries provide the power for the motors and NiMH for the electronics, this helps provide a clean supply for the PWAM board -the 24 Volts line from the SLA will power both motors per axle in SERIES. The choice of these batteries was based purely on the design criteria for the locomotive.

The model is designed to reproduce a scale 130 Kph pulling 8 "Teaks" -although it will not be able to do this on my tracks.

Having enquired via e-mail several other builders, I find that while 24 Volts is common on Gauge 1, voltages vary between 3 Volts and 48 Volts -depending on the builder. All of them think the speed of their loco is "about right" and they vary from a Class 8 shunter, (on 48 Volts), to a Deltic, (which actually can reach the scale Deltic Speeds pulling 10 Mk 2's) -on 12 Volts.

Q.E.D.

Yours Respectfully

R.M.Brades B.Ed B.Sc M.Sc M.I.A.A.P. Ph.D

 

[markoles]

Ralph,

I appreciate the very technical discussion. Doesn't running a motor at less than full speed affect the power factor? I guess it just increases the amperage, right?

Stan- thanks for making this a separate discussion. I don't know why I started to read that thread, but appreciate the continuation here.

My position is that prototype speeds should be the target at the top end of the motor rating. So, to me, that means that the gear ratio needs to be such that when the highest voltage is applied to the motor, the locomotive will operate at the prototype's speed. For example, I would expect a 4-6-2 pacific with 73" drivers to have a maximum scale speed of about 80 MPH. Conversely, my LGB mikado seems to top out at about 50 MPH, which is good for a freight engine.

There was a recent discussion about the Aristo E8, and its seemingly slow top speed. I think someone posted it topped out at about 65 MPH? However, it might have been the design decision to limit the top speed to improve the low speed performance. My aristo FA-FB and RS-3 seem to have good high speeds, plus good low speed characteristics. The USA F3A and 44 tonner also have good low speed, but the 44 tonner does run a lot faster than I think a real GE switcher ever should!

On the other hand the Lionel trains I have seem to run at 200 smph, and go from 0-25 in about a one volt jump. I can live with lower top speed for improved low speed performance.

Mark

 

[ralphbrades]

Mark,

If I examine the Power / Torque / Efficiency Diagrams [PTED] then for a Johnson 15-06 (my std motor) then the base E is around 20% until after 5,000 RPM at which point it leaps to 60% and maintains this until 9,000 RPM. So, it actually more difficult to run a pump at low speeds than higher. Thus the "draw" on the current supply is far higher, I squared R goes through the roof =BANG!.

The PTED for a 15-12 is radically different, the base E is only 5% until 3,500 RPM at which point it becomes 65% and maintains this until 15,000 RPM.

This is basically the same motor but wound for different voltages, in the first it is 0-6 Volts and in the latter case 6-12 Volts. Thus the former is a std motor for a 5 Volt line and the latter for a 9 to 12 Volt line.

regards

ralph

 

[Crosshead]

Oh, Dear.

Once again, someone has bitten off more than he can chew.

Eventus stultorum magister.

Give 'em **** Ralph.

 

[Trains]

Mr Ames,

My shay is sitting in a glass in case, I will not run it, as every time I do something breaks! I replaced the trucks and the replacements I got still fell apart. I called Bachmann and they said( guy I spoke to was very rude!) it was in the heat, cold, snow, and I don't recall what else he came up with. The engine sets in a glassed in case and has about two hours run time./DesktopModules/NTForums/themes/mls/emoticons/angry.gif

 

[Curmudgeon]

Stanley.
After you were in the design loop on the last engine, and overseeing the various issues that now do not appear to be quite up-to-par, let me just publicly share that this is not the time or place to figure out what speeds the locomotives should run.
You should have been on top of that BEFORE you got involved with the last engine.
I, for one, will no longer assist you in your attempt to obtain the necessary knowledge (without the experience) you seek, so that you can spout like an expert on the subject.
The tales of your dissertation on 1:1 railroad practices at Duncan's have preceeded you.
Go.
Away.

 

[Road Foreman]

Stan,

When Model Railroad News reviews a loco, such as the Aristo-Craft C-16, on analog DC they have the start volts =3.2.. At 3.5 volts, 0.50 amps = 1.6 SMPH; 10.0 volts, 0.55 amps = 13.8 SMPH; 15.0 volts, 0.57 amps = 22.9 SMPH; 20.0 volts, 0.63 amps = 30.8 SMPH.. Is this what you were wanting??

BulletBob

 

[Dwight Ennis]

Let's at least try and keep the discussion civil Gentlemen. Discussing the issues are fine, but let's try to keep personalities out of it please.

I fully realize the history here, and I fully realize that the battle lines were drawn long ago. I also realize that these discussions are important and necessary, and go to the core of what MLS is all about. I merely ask that you keep the discussion impersonal (if possible). This isn't the place for hostility.

Thank you.

 

[Curmudgeon]

Will a pre-emptive strike be acceptable?

 

[ralphbrades]

Quite Right -let us keep it factual....

So, lets us examine a few motors, something I doubt that very few of the members here -have had to do. I have placed a PDF file here:

http://www.cabbagepatchrailway.co.uk/PDFS/mfa2a.pdf

This is a copy of a commercial download file -I doubt they will complain.... But hopefully it will illustrate what the core design parameters have to be. As a thought exercise try and select a suitable motor for your favourite loco to run at a scale 100Kph, (or 62mph!), with a mass of 10Kg (or 22lb).

If people would like to take this further could I suggest the following books, (both of which are available on line and copyright free) :

"Railway Electric Traction (1922)", by F.W.Carter.

"Illustrated Encyclopedia of World Railway Locomotives", editor, P.Ransome-Wallis.

Both of which are highly informative as the real world locomotive practice, in their respective time periods.

Could I also point the propective researcher in the direction of:

"Model Railways" by Henry Greenly -I have the 1928 edition.

"Modelling in Gauge 1: Book 1 : Electric Propulsion" by G1MRA.

regards

ralph

 

[Road Foreman]

Ralph,

Most of the power supplys on the market today use 18 volts for max voltage.. LGB loco's max voltage is 25 volts.. So I beleive the issue for the manufacturer is make the locomotive run @ max SMPH with max volts.. I no of only 1 source for this info on locomotive's, Model Railroad News.. The smaller scale manufacturers do this all ready.. We just need to get the large scale manufacturers to do the same.. It would be nice to get different freight diesels that run @ the same SMPH @ the same voltage..

BulletBob

 

[ralphbrades]

BulletBob,

No, you and the author of this thread seem to have completely missed the point.... As I wrote higher up this thread

QUOTE:

Your arguments relating to "The Correct Voltages To Be Used" as thus invalid -unless everyone is using: the same motor, with the same gearing.

UNQUOTE:

Electronicly it would be very simple to servo lock the final axle speed to the input Voltage and I have seen this done in large scale locomotives -typically 5 inch gauge....

This would give you say; 5 Volts = 25Kph, 10 Volts = 50 Kph, 15 Volts = 75 Kph, etc

Your on board circuitry would have to continuously compute the final wheel size and the gear reduction ratio to enable a, (for example), 2-C0-2 with 6 feet 6 inch driving wheels with a 12.5:1 reduction ratio to travel at the same speed as, (for example), a 2-D0-2 locomotive with 4 foot driving wheels and a 16:1 reduction ratio -for the same input Voltage. This would have to feed back to a PWM which would have to continuously alter the Mark to Step ratio -to account for the increasing supply voltage, (both to itself and the motor), and the decreasing time interval required because of this...

Thus all the models would behave as if they were the same -regardless of configuration.

It could be done very easily. And that is the true horror of it...

Would any modeller want an "Iron Duke" to behave the same way as a "Class 43"? Would you like your "Shay" or "Climax" to behave like a "TGV"?

If you WANT to lock your speeds to absolute voltages -then this is what will happen.

regards

ralph

 

[Curmudgeon]

Ralph-
I do believe we are getting close to that "pre-emptive strike".

I can't say any more, or I'd say exactly what I think, and several of our moderators would need CPR.

And that ain't "Canadian Pacific Railway".

 

[Road Foreman]

Ralph,

I gave up on motors when they thaught me the right "hand-rule" for motors..

Stan,

Your best bet for info is from Model Railroad News sense they list the voltages, currents, Scale Mile Per Hour & the pulling power of the locomotives they review..

BulletBob

 

[chuck n]

I have refrained from commenting until now, as I consider this a very individual choice. What some one wants as a top speed, may not be what I want. That is what the throttle on the power pack is for. At full power (24V) my Accucraft K-27 barely makes 20 scale MPH, in contrast my Bachmann K-27 goes twice as fast. Since I don't like high speeds I adjust the voltage down for the Bachmann. When I run my 1:29 engines, Aristo and USA, I run them faster. They are so fast that I rarely run them at more than 14v.
I gauge the voltage to the engine and scale. I know that there are people who like to break the scale sound barrier with their train, but that's their choice.
I have calculated the speed for a measured distance on my railroad (one loop). The length is 87'. I have a little table on my transformer that translates time for a loop to scale speed.
Here are some examples of scale and speed for my 87'.
scale speed mph
time 1:20.3 1:22.5 1:29
seconds
60, 20 22 29
30, 40 44 57
Scale speed does vary with the scale of train that your are running, even on a fixed layout.
If I were to build an engine for sale, I would choose top speed that is slightly higher than the prototype. This is not because I want it, but there would be someone out there who would B*t*h that it doesn't go fast enough. And then we would have another group of angry threads to read.
We used to have a Christmas train show at the U.S. Geological Survey here in Reston, VA. We has everything from G to Z running. There was a large oval of three rail O gauge that circled the G gauge trains. Some of the O gauge runners ran flat out. They lapped our G trains several times over. That's, not my style, but it's their engines and trains that they are stressing.
Chuck N
PS Sorry the table didn't come out like I typed it, there should be spaces after the 60 and 30 seconds to match up with the scales.

 

[DKRickman]

If I may interrupt the battle for a moment...

I, for one, do not care one whit what voltage a model is designed to operate at. The fact that that is even a question seems beyone insane to me, given the standardization that has happend in almost every other common scale, but I digress.

What I care about, and what I take to be the purpose of this thread, is the practical speed range of a locomotive -WITHOUT- several hundred dollars of extra electronics to make it behave.

I want a locomotive that will start, and run smoothly at a creep. One that will bunch the slack gently, allowing me to uncouple without shoving the cars a foot every time. When it's time to go, I want it to run smoothly, consistently, reliably, every time, no questions asked, at a speed that is apropriate for the prototype. Actually, I find that even a prototypically accurate speed is a bit high, since most layouts are a bit short on running room.

I've rarely wanted to operate in any scale, with any prototype, much in excess of 20-30 scale MPH. With something like a shay, I'd prefer to run much slower than that.

My reasons:
1) Running slower takes more time. Sounds pretty simple, but it's a fact that escapes a lot of beginners. If the point is to watch "toy trains" run in circles, then this doesn't matter, but if we want to pretend that we've built a miniature railroad empire, making it seem larger for free is a great thing.
2) I like steam engines. I like sound. A steam engine with sound (especially with small drivers, as is common on NG engines) will not look or sound like much when running at a mile-a-minute. When you slow down, you can see the rods and the valve gear moving, and hear the exhaust beats.
3) The faster you go, the worse the derailment is going to be. Jump the track at 5 MPH, and you just need to re-rail. Jump it at 50 MPH, and you're fixing things.
4) Slowing down gives me time to enjoy the scene. Watch the engine coming 'round the bend, up the grade, through the tunnel, over the bridge, or past whatever scene I'm enjoying at the moment. Savor the moment.

It's been my expereince that a super-fast engine is rarely a decent creeper. You can make an engine do one or the other very well, but usually not both. Yes, Stan, electronics can HELP with that, but why on earth should I buy a $700 model that I'll need to invest another $300 in, minimum, just to be able to do anything besides run around in a circle? Sure, if you already have a DCC system, then you "only" need a $100 decoder, but if you're a beginner like me, you have to buy everything.

What I'm getting at is that I want a model that comes out of the box, goes on the track, and runs slowly and smoothly. No adding decoders, tuning controllers, adding transistors, or praying to the gods of railroading. I can walk into my local hobby shop right now and buy a wide range of models in every sale and gauge combination from Z to O (many from Bachmann, oddly enough), and every one will do exactly what I described. Why is that so difficult for a large scale manufacturer to understand?