Flashback to the 1950's Model

Flashback to the 1950's Model Railroader, YIKES!!!

Magnetic drives!!!!

Harold

Is this the same as a

Is this the same as a "magnetic coupling"?  I had a pool pump / electric motor that used the same type of thing.  There wasn't a direct mechanical coupling between the two.  As a matter of fact, there wasn't even a shaft protruding from the water pump which meant no leaking.  The only problem was if the pump impeller became jammed and couldn't turn (stalled) it would heat up enough to boil the water in the pump and ruin the unit.

Design considerations

I like it, Bernd!  Two things come to mind:

First, would aluminum be a better material than brass or copper, since it has at least some magnetic properties as well?  I believe that old speedometers were driven by a rotating magnet and an aluminum disk inside the speedo head.

Second, would it be beneficial to machine slots into the copper disk, much like the way a squirrel cage induction motor is made?  Induction motors do not use solid rotors, but rather segmented rotors which react better to the eddy currents, so presumably the same would be true for your design, right?

Finally, a question.  What is the practical application or utility of such a drive in a model locomotive?  What can it do, or what designs would it allow, that a mechanical coupling will not?

rtw3rd: I think those are

rtw3rd: I think those are synchronous motors -- the rotor is a permanent magnet; the stator is just a coil running the 60Hz AC to produce an alternating magnetic field (I've had fish tanks and ponds for years, so I've had a few pumps apart from time to time). This looks more like an induction motor type of device: the relative motion of the magnetic field with the conducting disk induces currents (the eddy currents) in the latter, which in turn creates its own magnetic field, which interacts with the applied field to create a rotational force.

Disclaimer: I haven't watched the video. The above is my two cents based on basic motor theory I learned ~35 years ago .

Q: What's the application for this? Locomotive drives?

Overcoming (mechanical) resistance

It'll be interesting to see how much magnetic force will be required to overcome the mechanical resistance of the gears and weight of cars being pulled - the flywheel is a nice bit of stationary inertia to overcome, but I suspect it pales in comparison to an Athearn gear tower and a dozen freight cars.

It does seem to lend itself to smooth starts and stops, although I suspect you'll also want some form of mechanical braking as well.

Some questions answered

First Harold.

I don't recall magnetic drives from the 50's. I remember a clutch type like that used on weed whackers and chain saws. There was also an attempt at using a fluid drive. That didn't work either.

Rick asked.

Not quite the same. Yours is a magnetic break away clutch. The coupling has all the poles in the same direction (north) on the motor side and the opposite pole (south) on the impeller side. These attract. It did exactly as it was intended to do. To break loose so the motor would not burn up. The overheating came from the eddy current effect of the stalled impeller, that creates heat. The type of drive I have here has a slipping effect than can also create heat, but needs to be way bigger for that.

Ken,

Aluminum would work, but you want mass for this to be more effective. Also I believe aluminum ranks 3rd in electrical conduction, I may be wrong though.

From what I can tell from all the info gathering I did, I found no mention of using slots. May try that to see if it has an effect. Also the difference might be so minute that it's not even visible to the naked eye.

Your question of what can it do will be self evident once I explain. What this drive does is separate the mechanical link from motor to wheels. This drive will emulate the drive of the locomotive you run on your job. Imagine your locomotive having a drive like the models do. Motor, drive shaft, gearing, all connected in one long drive train. How would your locomotives MU with other locomotives of different characteristics? No very well I would assume.Where is the mechanical disconnect on your locomotive? It's between the gen/altenator and the traction motors, right? There's wires that go from the gen/alternator to the traction motors. This drive emulates what those wires. Now a guy running plain DC can MU different engines together since there is no mechanical link between the motor and trucks. Think about this for a minuet. Another way to look at this is this sort of emulates the converter in an automatic transmission in your car. The engine runs at a higher rpm while the speed of the vehicle increases to catch up with the engine and it's associated gearing.

Steve, your second sentence is correct as to what you assume.

Jeff, One of the biggest things with models is friction. And I'm sure there is a lot in the model drive train. I'm looking at alternatives such as ball bearings and magnetic gearing. This drive concept was found on a British forum were members had drives installed from Model Torque on Atheran engines. The comments were quit interesting as to the feel of the drives on models. One comment was that it actually felt like the real thing. The motor would rev up and the locomotive speed would gradually increase. You would then back off on the throttle to maintain a constant speed. If your train load was to heavy you would need to add extra power, just like on the real thing.

Mechanical braking can be done by reversing the motor. Remember there is no connection to the gearing except the eddy currents. The engine would stop in a shorter distance.

To prove this concept I will need to build a test bed with wheels to prove this was done at one time by Model Torque. For those that are interested in some of the material I found on this I can post it. A majority of it comes from the Model Torque web site which seems to be defunct since the founders death last year on December of 2012. If it's all right with the management at MRH I could post this info for those who are interested enough to see how this works.

Bernd

1950's Magnetic Drive

No one made one, the idea was floated in one of the suggestion columns about 1952 I believe. I know the issue was the blue with a black and white photo so it was before 1953.

Ah yes, bad motors and clutches, the good old days.

Harold

50's Drive

If they would have had the neodymium magnets back then I'm sure we'd have a drive like that on the market today.

Bernd

Could you use one large magnet

in place of several small ones?

Stalling an ATC loco....

Dear Bernd,

I just reconfirmed with my friend who gave ATC drives a go a few years ago, it is entirely possible to "stall" an ATC-equipped loco if the load is heavy enough and the grade is steep enough.

NB that "stall" in this instance is "loco not moving relative to ground, with motor still spinning-free"
(due to the lack of solid physical connection thru the ATC coupling),

not "stall" as in "full mech lockup" (and associated massive current draw condition)
as is possible with a traditional Ath-type loco mech.

Arguably, such an (ATC equipped) loco does not need any significant "momentum" added at the control stage via a decoder (the loco "accellerates up" and "drifts to a stop" mechanically instead of electrically), and can entirely-prototypically "stall on a grade", requiring helpers to get moving again. This also, funnily enough, would allow "adding of helpers to a stalled-on-grade train on Analog Control, without need for additional block switching or a 2nd throttle...

I will have to see if I can get my friend to dig up his testbed ATC locos, and shoot some video...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS I seem to recall an article in a decade+ old Continential Modeller RE ATC-style drives, installing them in O scale Euro electric-outline locos. Might be useful for your growing "ATC research/history" collection

"and associated massive current draw condition"

 If a loco is weighted correctly it will slip it's wheels before it draws too much current or damages it's drive components. The wheels will slip just like the real one's do instead of the transmission slipping like a '53 powerglide :> ) ......DaveB

One Large Magnet

I can't answer that truthfully. I would have to experiment with it. I do know that if the poles of the magnet are all one pole, in other words, all south poles facing the other disk, it will not work. The poles need to alternate north-south all the way around. If I find out different I'll post it.

My next experiment will be using bigger magnets with more "pull".

Bernd

ATC Drive

Glad to see you weigh in on the subject Prof. Always appreciate your words of wisdom.

After reading about this I thought this would be the best "mechanical" way to simulate how the prototype engine works without all the electronics need to do the same. I'm going to assume that it would be possible to use engines from different manufacturers, that don't like to play nice together, to run in MU.

As to your reference to "current draw" are you talking about the full mechanical link from motor to wheels or what the motor draws on an ATC at stall?

This is only the start. I'm also looking at making my own drive system (chassis) using belt drives with ball bearings on all associated shafts. I'm also going to see if it's possible to use miniature magnetic gearing. I've seen videos of real applications. Supposedly no gear friction and very smooth operation. Can it be miniaturized? I guess I'll find out.

Bernd

Current draw

Dave,

I believe the the Prof. is referencing the Athearn engine with out the ATC. Since you mentioned the current draw at the slippage point I'm going to have to see if there is a higher draw. Will post the results when I get them.

Bernd

Resistance and Coupling Effect

Berndt,

Silver and copper followed by aluminium have the lowest electrical conductivities allowing the highest induced

currents in the material also the thicker the material the lower the resistance.

This would suggest that making a flywheel out of copper instead of using a separate induction rotor and flywheel

may be an efficient use of space and mass in your model locomotive also using fewer but stronger magnets may

be a way forward to a more powerful drive system.

I look forward to seeing the results, my models are n scale and don't it will fit but may try fitting out an E9.

Thanks for the inspiration.

Mike

Liverpool and Manchester Railroad [where it all began]

Materials used

Mike,

Machining copper is not fun. Do to the gummy nature of copper turning on a lathe is difficult, but not impossible. Brass will have to do. It's seems to work pretty good. I quickly made a very crude flywheel set up last night and tried it out. Hot glued some wood shims on to the second chassis of a critter build I'm working on. Then had to remake part of the flywheel. It ran but was a bit jerky, unfortunately this chassis has the "split gear syndrome". I did manage to push 6 On30 side dump cars with it.

I had the flywheel you see in the picture above from previous experiments to try and duplicate the eddy current drive but succeeded only in making a magnetic break away clutch. I reoriented the magnets on this one to North - South and so forth all the way around the flywheel. This flywheel is approximately .625" and has 16 magnets. So it's smaller and the magnetic force is less too since I only have 16 magnets instead of the 32 that is in the larger one.

As I've said, this is a very crude setup and just proves that it will work. I've already been looking at larger size magnets. I also need to determine how large a disk or flywheel I will be using. There will be probably several different sizes since I'd like to redo some of my engines. They range from the large body road engines such as F units to the small switchers Alco produced.

I have all intentions of continuing to post my progress on this. There may be long spells in between postings do to other projects that are being worked on, but rest assured I will work on this till I either finish the project or give up trying to make it work properly.

Bernd

CM Magazine

Prof,

Did a quick Google on CM. Very interesting. Will have to keep looking to see if I can find that info. Thanks.

Bernd

Current Draw

Just finished doing some preliminary current test with the crude test rig in the previous picture. At 12 volts with the motor running freely, in other words no load, just the motor, it draws .050 amps or 50 milliamps. Powering just the chassis down the tracks I get a meter reading between 50 milliamps to 60 milliamps. Stalling the chassis with the motor running at 12 volts I get a draw of 150 milliamps. If I totally stall the motor, holding the shaft from turning, I get a 250 miiliamps draw.

So the conclusion that can be drawn from this is, yes current increases in the stalled state but not moving along on the rails. At one point the wheels even started spinning. So I can draw the conclusion that this emulates the protoype engine pretty darn close with this type of mechanical drive system.

Bernd

Dear Bernd, Some more info,

Dear Bernd,

Some more info, the article I remember from CM was RE a 7mm (43.5/1 "O scale") Euro electric loco with "Dyna Drive", which appears to be a similar form of eddy-current transmission from the UK. Still no joy on tracking down the specific issue # though, and I know I threw out a load of CMs over the past few years,...
(they went to the local Model RR club "Youth Dept")

A search brought up these thread postings on RMweb
(Brian Harrap is a well-known UK modeller who is a maniac, in a good way, for tweaking loco mechs mechanically for oily smooth performance, before looking at throwing electronics at the "problem" ).

http://www.rmweb.co.uk/community/index.php?/topic/38591-quai87/page-7

http://www.rmweb.co.uk/community/index.php?/topic/71041-alternative-drive-systems/

and a search of the Model Railway Journal index reveals Issues 18 (review), 28+29 (4mm scale article!), 41, 84, 86, and 130 all had Dyna-Drive content.

Hope this helps...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Flywheel location

Looking at the critter drive photo, I would think that the drive would be more effective if the flywheel were coupled directly to the gears, rather than to the motor.  That way the motor could quickly spin up (like revving the engine) or stop completely, while still allowing the flywheel-powered mechanism to move.

Also, would mounting magnets on both halves of the drive still allow it to function as a limited slip coupling?

Compare DC motor and ATC drive to Available brushless motors?

High performance hobby motors are trending toward brushless motors which are like the AC motors used in some new diesel locomotives.  AC drive is useful in locomotives that are worked at slow speeds with heavy torque, without overheating the motors.  The AC motor system is more expensive, but this would be balanced against the cost of the ATC drive.  

For larger than HO scales, AC motor systems are available off the hobby shop shelves... but such systems are designed to work with battery power DC and R/C signals, another feature of large scale locomotive.  DCC would probably require a special decoder to run a brushless motor.  However, Marklin does appear to have experimented with AC motors for DCC.

Dear Prof. It all

started with those two links you supplied. They are the ones that sent me on this quest to find out how those ATC drives worked. So I think we have come full circle. Again thanks for you comments and suggestions. I'll check out that other info on the Dyna-Drive.

Bernd

..

The best magnetic substance is, well, another magnet, so if you were to make two disks, one on the motor and one on the drive, with counter spaced magnets, you'll have the maximum drive attraction...

Drive coupling

Ken,

As I mentioned this was a crude set-up just to test and see if I could build one and have it function. Attaching the flywheel to the gear on this Athearn DD40 gear tower is impossible since the worm gear wobbles around. Also think of how the Athearn drives are built. Their flywheels are all attached to the motor so the drive shaft universals can turn with the gear tower. The other thing is that flywheel is actually two separate pieces.

I finally located the PDF files showing how the Model Torque drive is designed. I've posted the links:

http://www.intercitymodels.com/ATC.pdf

http://www.intercitymodels.com/ATC01.html

http://www.intercitymodels.com/ATC01.pdf

http://www.intercitymodels.com/gib1.pdf

http://www.intercitymodels.com/gib2.pdf

And here's a U-tube video of magnetic gearing.

Mounting magnets on both halves of the flywheel/clutch gives you a magnetic coupling instead of a slip type drive.

This drive is hard to comprehend if you haven't seen it in real life and it is harder to explain how it actually works. I hope people look at the links I've posted as it helps in understanding how something like this can work.