[SeattleTrainGuy]

Hi, new member here. My primary interest is converting 1/4 scale park gauge miniature trains to electric power.

My first post asking for help about direct drive systems, apparently got deleted by the admins.

Wondering if new members are not allowed to participate on the forum? Is this normal behavior on this forum- deleting questions.

Thanks
Glenn B.

 

[brian_]

No, first posts are not normally deleted, but an administrator might have thought that it was spam, since it was about a train rather than a car. I think we've actually had some discussion of a small train application before, and it should be an easy conversion.

 

[Duncan]

Hi, new member here. My primary interest is converting 1/4 scale park gauge miniature trains to electric power.

My first post asking for help about direct drive systems, apparently got deleted by the admins.

Wondering if new members are not allowed to participate on the forum? Is this normal behavior on this forum- deleting questions.

Thanks
Glenn B.

Hi
I have been helping a local guy who is doing this - he has one locomotive that he has converted and is doing another
The motors he uses come complete with a reduction gear and he then uses a chain drive to the trains wheels

What do you need to know?
Let me know what you need and I will go and ask Colin
I'm helping him with the electrical stuff - but I can't remember the bits he is using

 

[SeattleTrainGuy]

Duncan, thanks very much for your reply. Basically Iam working on converting a 12” gauge, 3” scale (1/4 scale) locomotive to electric. The loco is a center cab design, with two sets of trucks (a frame holding 2 axles and drive wheels), one under each hood . I plan on mounting a 7” diameter DC series wound forklift motor and Curtis controller on each truck, and powering both the front and rear drivers. Iam told these motors typically like to run at 3000-4000 rpm, or a bit higher. However, my my max safe drive wheel speed (6.5” diameter driver) equates to 517rpm.

So trying to understand how It is feasible to do this with direct drive to the axles, via chain and sprockets. Or, if I should come up with some kind of gear reduction to power the loco and train consist, at this low slow speed, (10,000# train load, 5cars, 30 passengers, 1500# loco).

The simplest build method is direct drive. But I am skeptical about whether it is feasible to operate these motors with out some kind of gear reduction - and what gear reduction ration is best.

Thanks much for any advice you may be able to offer.

(I actually have two additional locomotives I would like to convert, if this center cab project works out properly.)

Regards,
Glenn B

 

[Duncan]

Duncan, thanks very much for your reply. Basically Iam working on converting a 12” gauge, 3” scale (1/4 scale) locomotive to electric. The loco is a center cab design, with two sets of trucks (drive wheels) one under each hood . I plan on mounting a 7” diameter DC series wound forklift motors and Curtis controllers, one on each truck, and powering both the front and rear drivers). Iam told these motors typically like to run at 3000-4000 rpm, or a bit higher. However, my ideal drive wheel speed (6.5” diameter drivers) equates to 517rpm.

So trying to understand how It is feasible to can do this with direct drive to the axles, via chain and sprockets. Or, if I should come up with some kind of gear reduction to power the loco and train consist, at this low slow speed, (10,000# train load, 5cars, 30 passengers, 1500# loco).

The simplest build method is direct drive. But I am skeptical about whether it is feasible to power the t some kind of gear reduction.

Thanks much for any advice you may be able to offer.

(I actually have two additional locomotives I would like to convert, if this center cab project works out properly.)

Regards,
Glenn B

I will have to drive over and talk to Colin
My first thoughts are that you have entirely too much motor there!
The motors Colin uses are much much smaller - with a built in reduction gear - trains take very little power to drive and with passengers you want to go slowly!
I will try and nip over today and tell you what he uses

 

[brian_]

I plan on mounting a 7” diameter DC series wound forklift motor and Curtis controller on each truck, and powering both the front and rear drivers. Iam told these motors typically like to run at 3000-4000 rpm, or a bit higher. However, my my max safe drive wheel speed (6.5” diameter driver) equates to 517rpm.

Okay, so you need a motor to wheel speed ratio of 6 or more to get the motors to the speed where they will produce maximum power, and that will also give you a six-fold increase in torque for low speeds. You can use a lower ratio if that provides adequate performance, but with all that mass you probably want the reduction.

So the top speed of the train is about 4.6 m/s (16 km/h, 10 MPH)? I guess that isn't surprising; used to drive one of these trains (similar scale, fewer passenger cars) in a summer job, but that was decades ago and I don't remember the speed with any accuracy. Ours had a small general-purpose gas engine - a single-cylinder Briggs & Stratton or similar - I think driving through a torque converter; here is a newer image:

Is this the sort of thing we're talking about?

So trying to understand how It is feasible to do this with direct drive to the axles, via chain and sprockets. Or, if I should come up with some kind of gear reduction to power the loco and train consist, at this low slow speed, (10,000# train load, 5cars, 30 passengers, 1500# loco).

The simplest build method is direct drive. But I am skeptical about whether it is feasible to operate these motors with out some kind of gear reduction - and what gear reduction ration is best.

You can have a substantial speed reduction (torque increase) without gears, just by using the chain drive. The ratio isn't extreme, so it seems to me that you should only need a single stage: the biggest sprockets you can mount on the axles without clearance issues, and the smallest sprockets that are suitable for the torque and power level on the motors. My guess is that you might want to use a separate chain to drive each axle so that the chain wraps sufficiently around each sprocket.

 

[SeattleTrainGuy]

Hi Brian, thanks very much! Good to hear. I’ll go with the 6:1 gearing. Either chain and sprocket, fab up a worm gear, or possibly use 6:1 golf cart transaxles bolted up to the motors. Just found a local source for these earlier this evening. I do intend to power one axle each truck, then connect the second axle with an additional set of sprockets and chain...

Yes indeed, the train you drove may actually be the same model, as one of the locos I plan on converting - yours looks like an Ottaway B-14 rocketliner in near new condition. Maybe even the same one pictured below. Ottaway only manufactured a handful of these 14” ga park gauge trains- maybe a dozen or less. The badging on the nose of yours looks the same as what came with my old barn find. My Rocketliner is pictured below, in black automotive primer, as it sits today. It was an on line barn find that I identified only after I had it shipped home. It’s a long ways from completion, but certainly doable, once I work out the optimal drive chain decisions - which I think you have just solved!

Much appreciate your recommendations and your advice.

Very exciting to move forward!


Glenn

 

[mscott89]

Hi Brian, thanks very much! Good to hear. I’ll go with the 6:1 gearing. Either chain and sprocket, fab up a worm gear, or possibly use 6:1 golf cart transaxles bolted up to the motors. Just found a local source for these earlier this evening. I do intend to power one axle each truck, then connect the second axle with an additional set of sprockets and chain...

Yes indeed, the train you drove may actually be the same model, as one of the locos I plan on converting - yours looks like an Ottaway B-14 rocketliner in near new condition. Maybe even the same one pictured below. Ottaway only manufactured a handful of these 14” ga park gauge trains- maybe a dozen or less. The badging on the nose of yours looks the same as what came with my old barn find. My Rocketliner is pictured below, in black automotive primer, as it sits today. It was an on line barn find that I identified only after I had it shipped home. It’s a long ways from completion, but certainly doable, once I work out the optimal drive chain decisions - which I think you have just solved!


View attachment 121319


Much appreciate your recommendations and your advice.

Very exciting to move forward!


Glenn

Looks like a really cool project Glenn, Brings back memories of being a kid playing with train-sets

Please keep updating the post with your progress, really keen on seeing the end result!

 

[brian_]

One approach that you might consider in this conversion is to go with a lower voltage than a car conversion would normally use. High voltage is used in a car mostly to allow the motor to work at higher speed, although it can also push more current at low speed; high speed isn't needed here and unusually high current can only be used briefly (for reliability).

The brushed DC motors used in EV conversions are similar to those used in forklift trucks, and many are simply salvaged from forklifts. The train is much more like a loaded forklift than it is like a car: lots of mass, moderate acceleration over a long period, and no concern with the weight of the powertrain.

As Duncan mentioned, by automotive EV conversion standards two 7" diameter motors is a lot for the power needed in this application. If you treat them like they're still in a forklift - meaning moderate voltage and moderate speeds - they should be effective and very reliable. That would suggest a more moderate reduction ratio, resulting in motor speeds more typical of forklifts than cars.

 

[brian_]

Yes indeed, the train you drove may actually be the same model, as one of the locos I plan on converting - yours looks like an Ottaway B-14 rocketliner in near new condition. Maybe even the same one pictured below. Ottaway only manufactured a handful of these 14” ga park gauge trains- maybe a dozen or less. The badging on the nose of yours looks the same as what came with my old barn find...

Perhaps I should have paid more attention to that train and appreciated it more at the time, but it wasn't the focus of that summer job. I wouldn't have guessed it was a rare machine, and it's even possible that the current train is a replacement for the one that I drove, but it's certainly the same track.... after hours of prying out spikes, pounding out old ties, driving in new ties, setting ballast, and driving spikes, the track is burned into my memory more than the train! We replaced a few sections of rail, too; it's kind of funny when two guys walk with a rail section - you can't to that with full-sized rail. I don't think any of it was in near-new condition in the 1980's. Now I wish I had my own photos from that time, but we didn't walk around with camera-equipped computers in our pockets back then.

 

[SeattleTrainGuy]

Hi Brian, thanks for following up with comments, particularly regarding gearing and lower voltage/current consumption.

Indeed, slow speed, high torque, Max draw bar capacity is sort of my main goal...

Yes, agreed two motors are more or less overkill. The main design issue i have is the frame and chassis are that that of an old home built, center cab electric. So it has two separate hood ends for propulsion equipment, and a low slung center engineer compartment. So no real room for a traditional driveline from the motor to the far set of drivers. Hence I plan to use one motor to power one truck and a second motor in the other hood, to power the second truck. - and drive it in either direction for yard switching duties.

Iam thinking, in theory, l should power all 8 drive wheels (both front and rear trucks) as the coefficient of friction on steel rail is very very small. So available tractive effort probably should be distributed to all the drivers. Hence the two (basically free) oversized motors.

(Now, the second loco, the black, primered B-14 above already has an OEM gear box with provision for front and rear drive lines. So I plan on only one motor in that chassis.)

Glenn

 

[brian_]

Hi Brian, thanks for following up with comments, particularly regarding gearing and lower voltage/current consumption.

Indeed, slow speed, high torque, Max draw bar capacity is sort of my main goal...

Yes, agreed two motors are more or less overkill.

Rather than "overkill", I think this is just a case of having suitable motors to use them as they were intended, rather than having to push them harder as is normally done in a car.

Iam thinking, in theory, l should power all 8 drive wheels (both front and rear trucks) as the coefficient of friction on steel rail is very very small. So available tractive effort probably should be distributed to all the drivers. Hence the two (basically free) oversized motors.

I agree. In an electric train designed from scratch and needing high performance (in train terms, meaning high grades and high-for-a-train acceleration) trucks supporting every car are powered. In a conventional configuration of one locomotive and unpowered cars, it certainly makes sense to use as much as possible of the locomotive's traction.

The main design issue i have is the frame and chassis are that that of an old home built, center cab electric. So it has two separate hood ends for propulsion equipment, and a low slung center engineer compartment. So no real room for a traditional driveline from the motor to the far set of drivers. Hence I plan to use one motor to power one truck and a second motor in the other hood, to power the second truck. - and drive it in either direction for yard switching duties.

I don't see separate motors for each set as a problem - rather, that's how a "real" (full-size) train would work, because it makes sense. It does mean the cost and electrical complication of two controllers, but that beats building the mechanical complexity of driving axles on two pivoting trucks from one motor (or even from separate frame-mounted motors). As long as each motor is protected from overspeeding if the wheels connected to it slip, it will all work fine.

Bi-directional operation is not an issue, as long as the chain drive works properly in both directions (i.e. it doesn't use a chain tensioner against the slack side which can't handle becoming the tight side). Controllers often assume that reverse should only be used at lower speed than forward, which doesn't generally apply to a train, but that might not be an issue.

(Now, the second loco, the black, primered B-14 above already has an OEM gear box with provision for front and rear drive lines. So I plan on only one motor in that chassis.)

Since the mechanical complication has already been dealt with in this case, one motor makes sense to me.

 

[SeattleTrainGuy]

Brian, thanks for the positive view! Iam certainly looking forward to building these out and finding how they perform. For me, part of the fascination with this scale of railroading is building these miniature trains in the same manner as their full size, main line brethren. There are may smaller, rideable 1/8th scale, 7.5” gauge electric train builds in the live steam hobby. But they are all mostly 3-4 x smaller than these and use basically hobby size, or E-bike rated, motors and equipment - 600w -1000 w motors, driving 4” wheels. So building in this scale is still a bit of an unknown. However, I am becoming more and more optimist these poor yard goats will perform much better than expected.

Glenn

 

[Duncan]

Hi Glenn
Couple of minor issues -
6:1 reduction will be hard to do in one hit because you are limited in the size of the larger wheel
A worm drive may present problems when you have to push the thing!
Colin get his bits from

Home

I think they are Australian so you should look for an American site
Rough costs
Motors - $100 each
Controller - runs two motors - $200
Control box that the driver uses - $160
There are a lot of other motors on that site - they all have an inbuilt reduction gearbox to take them to about 400 rpm
These are some pictures from Colins

Motors used

 

[brian_]

For me, part of the fascination with this scale of railroading is building these miniature trains in the same manner as their full size, main line brethren.

Excellent - an excuse to discuss diesel-electric locomotives!

For those who are not into trains, a typical diesel-electric locomotive has a diesel engine driving a generator, which connects to the drive motors; there is no battery, and the electrical system acts as a continuously variable transmission which can run with an infinite reduction ratio. Traditional diesel-electric powertrains in heavy off-highway dump trucks and boats and ships are similar. Generator and motor types and the control system between them have changed of course over the decades, because diesel-electric propulsion started long before high-power electronics.

The diesel-fired generator set and fuel tanks can be replaced with any other electrical energy source and the drive motors (and their installation) can stay the same - this makes turbine-electric, hybrid diesel-electric (with battery), hybrid diesel-electric (with third-rail or overhead wire electrification), pure battery-electric, and fuel cell hybrid locomotives easy to build... and all of them are out there on the rails.

The inherent characteristics of the direct diesel to electric system are largely easily duplicated with a battery, controller, and any motor... if the controller has a current limit (corresponding to the current limit of a diesel-electric and establishing a low-speed drive force limit) and a power limit (corresponding to the engine power limit of a diesel-electric) that applies regardless of speed. The battery voltage directly corresponds to the voltage limit of a diesel-electric system. The current limit has to be low enough to protect the battery, the controller, the motor, and the train structure (how hard can you yank on that first passenger car?); it also should be low enough to avoid spinning the drive wheels in normal conditions. The part that needs some thought is how to interpret the "throttle" control: the usual train practice is to use it as a power request, but at low speed that makes it too sensitive; the normal approach for an EV is for the "throttle" to control the current (and therefore the torque), but in the train that means that as the train speeds up it will use more power, not like the real diesel-electric locomotive. Current control is likely the reasonable way to go.

My understanding is that the motors of diesel-electric locomotives (and electrically driven cars of trains without locomotives) are typically mounted directly on the trucks (so they turn with the trucks, and are not supported by the locomotive or car structure), and there is one motor per axle. That would certainly work in scale, although with a chain drive it is reasonable to drive both axles of a two-axle truck with one motor.

A diesel-electric locomotive normally has dynamic braking, which means running the motors as generators and just discarding the generated power through huge resistor banks. In a battery-electric system the equivalent is regenerative braking: again the motors are run as generators, but the generated power recharges the battery. Series-wound brushed motors are not capable of controlled regeneration or any other form of generator operation unless the field (stator) winding is electrically separated from the armature (rotor) winding and suitably controlled. What's the plan for braking? Unlike a diesel-electric locomotive, scale gas or diesel engine-driven locomotives presumably wouldn't use braking by the drive system, and I suppose they can just use the brakes of the cars being pulled. I remember the power lever on the train that I drove, but I don't remember what it had for brakes.