Electric motor torque figures

The main Swiss makers (Minimotor (aka Faulhaber) and Maxxon) usually publish data on their websites, I think you'll find torque data there. The problems with the smaller coreless units are a mixture of:

a) need the right power supply - too much current on a stall and you have a dead motor. A Pentroller helps in giving some overload protection. b) decreasing torque with size. The 0816 is about 1/4 of the torque of a

1016. c) wierd materials; some of the smaller ones have ceramic shafts, no idea how fragile those are in practise - I've avoided anythign smaller than 0816 Minimotor with metal shaft (there is a 0816 from Maxxon which has ceramic shafts). d) many of the very tiny motors only really run at silly high RPM's with absolutely nothing at lower speeds, so you end up trying to build a complex gearbox to get the speed back down again.

My experience (2mm scale) is that you sit and work out how to squeeze the largest motor you can into the space - use the motor casing as the boiler wall, etc.. The hardest part is arranging the gearbox and drive to give minimal friction. I've managed to get the current down to 5mA on my latest loco powered by an 0816.

Some of my Fremo colleagues (1:160 scale models) have gone to truely silly motors:

Tom Knapp has built a "Galloping Goose" in Nn3 with a silly small pager motor (published in the 2mm Scale Association magazine, but not sure if its anywhere else).

I think Stephen Harris' 2mm scale DS40 shunter appeared in MRJ some years ago. That one is a useable loco, capable of slow speed shunting and moving a few wagons around (the others I've not had the chance of driving, so can't really comment).

Quite what is so small that needs a 4mm or 6mm dia motor in 4mm/ft scale ? A 6mm*12mm motor sounds suitable for an axle hung traction motor :-)

- Nigel

The Mashima website gives current and rpm but not torque. The only other source I know is the EMGS data sheets. You have to join or befriend a member. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Does the EMGS data go as small as even 8mm dia motors ? The stuff I've seen is for larger ones (more suited to normal 4mm locos).

- Nigel

Bill asked for the data on conventional model motors, he already has data on the mini coreless motors. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

The message from "Bill Davies" contains these words:

Of course, most, if not all such locos had tenders - being fairly boxy why not look at tender drive?

Faulhaber put full specs in their catalogue and I think I once found it on-line somewhere. Factors that make the exercise less than precise:

- torque goes down in relation to armature diameter like a jet fighter in a power dive! (buy the largest diameter that can be fitted)

- gear friction is just about the biggest factor in torque at the driving wheels. (consider multi-stage gears rather than single high reduction worm and pinion) Consider using screw threads for the worm because the worm diameter is proportional to the friction caused.

- bearing friction on driven axles and connecting/coupling rods becomes a significant factor.

- consider a larger diameter motor in the tender driving through universals and cardan shaft if possible.

All good advice and aspects which I have already considered. To answer another poster, the project I am working on is the 4' gauge locomotive "Fire Queen" as preserved at Penrhyn Castle, the only Crampton locomotive surviving in the UK. I have asked a few questions here in the past, this project has been on paer for well over a year now. For those who aren't familiar with this locomotive, there are a few images here:

an open cabless locomotive, a tender mounted motor with cardan shaft drive would be rather obtrusive. I can accomodate a 6mm x 12mm in the firebox mounted vertically, depending on whether I can obtain appropriate gears. Of course I could build a tender drive unit, but it's not an arrangement I've ever liked, hence the research into pager motors. I am also considering fitting a dcc decoder in the tender, but dcc is a new world to me and I've yet to establish how helpful this would be in controlling a miniature motor, Cheers, Bill.

Perhaps placing the motor in the tender with step-down gears to bring the cardan shaft under the footplate might work?

A decoder delivering above audio frequency PWM _and_ EMF feedback control might be an improvement, but that can all be delivered through the rails. Weight, adequate pickups and a decent flywheel will all do more for performance when you're playing at the bottom end of the scale!

I haven't built anything that would count as an equivalent, but I have an ex-Roco HOe Diesel with a Sagami 12x20 motor and 17x3mm(!) flywheel that runs nearly a meter from 12 volts when traction current is removed. :-) My Prussian P3 (2-4-0) with tender motor and flywheel driving the loco drivers and the weight of the tender on the rear beam of the loco and pickup throughout performs like a much larger loco

Regards, Greg.P.

Looking at the pics my fist thought would be a horizontal motor in the firebox/boiler, should take a 10mm diameter, and drive on the front axle since it looks like a gearbox on the rear axle will foul the cab floor. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

The valve gear is driven off the front axle, being highly visible I will at least need to make some representation of it. To date I've been unable to track down any images of the cab floor, but my current thinking is to use a gear train of small 9/12 tooth nylon gears to bring drive from the main gears and motor in the firebox. Possibly not obvious in the images linked to, Fire Queen lacks conventional frames, the boiler acts as the main structural member. This means I can't split construction between frames and superstructure, I am keen to make the drive mechanism accessible through the firebox - the proposed miniature motor and gear train arrangement should drop in and out vertically together with the rear axle. Cheers, Bill..

Bill Davies wrote:

I assume you've read Mike Sharman's book on Crampton's, it has a few hints and tips on modelling them.

I favour fitting a larger motor than those you have proposed.

I don't have the figures, but I guess the boiler is about 3ft3 to 3ft9 dia to fit between the 4ft gauge wheels. Thus a 12mm dia motor could go along the boiler. A 10mm would be no problem.

The difficulties then become how to make the model possible to dismantle. I suggest two options (there will be many others): a) Use a motor with a screwed nose (eg. Faulhaber 1016/1216). Fit the screwed bush (Branchlines part) to the front face of the gearbox (which lies just behind the front wall of the firebox). Arrange method to either open smokebox door, or remove smokebox, to gain access to unscrew the motor from the mount, and then be able to drop the gearbox. Motor can directly drive a worm if the loadings are gentle (work fine directly driving worms in 2mm scale). b) Fit a fairly coarse spur gear to the motor shaft (say 64dp), and have that mesh with another spur in the gearbox which is fitted to base of firebox. The accuracy of mounting the gearbox against the top of the firebox determines the mesh. There should be space for some brass blocks fitted to the firebox and gearbox to ensure a reliable and repeatable mesh. Subsequent disassembly (eg. splitting boiler from firebox) allows removal of motor. Example of similar construction in the pictures of my 2mm scale Midland 1F (0816 motor, boiler held by sliding fit under tank edges and a clip under the smokebox) at:

For the second design, if you seek out the double ended Faulhabers (they exist, but not as readily available as the single ended types), then it should be possible to fit a flywheel in the firebox area. I'd probably support the flywheel on a ball race salvaged from a computer disc drive.

I'd look for 50:1 or higher reduction. Easy with 2mm Scale Association gearsets in a 4mm scale loco - standard 2mm gears are bored 1/8th inch. Alternatively, one of the 4mm multi-stage gearboxes might fit, such as those by Branchlines, Exactoscale or High Level.

- Nigel

Yes - an excellent book.

So would I normally.....

It's actually 3ft diameter according to the figures I have, with wooden lagging over that adding another few inches, so a little over 12mm externally. A 10mm motor would be the maximum without having the boiler built permanently around it.

I'm afraid the link doesn't work for me.

Are the 2mm Scale Association products available to non-members? Having cut my teeth on S4 in the 1980s, this is the closest I've got to anything finescale in nearly 20 years, so I'm not really aware of what is currently available, Cheers, Bill.

Or a 12mm motor with a thin walled tube of a boiler around it for the wooden lagging (guess lagging is at least 1.2in thick, which equates to 15thou wall thickness), thus removing the need to make anything to locate the motor within the boiler. However, I think a 10mm would be adequately powerful for the loco and should be easy to mount.

[ snip, refer to old posting for text ]

Sorry, MS-Windows cut and paste; that format works in some news readers. Try this, written out longhand (scroll to bottom of page for loco pictures, 0816 motor):

Also, example mechanism using the screw mounted nose and 1016 I mentioned before at:

And another using just a strap to mount the motor (0816), with a small (glued) wedge under the rear to set the mesh height.

No. But you might find a member prepared to order them for you if you asked nicely. Much of the gear range is offered by Ultrascale (if they are still selling gears, we've recently had to find a new source), the only special exclusive

2mm ones are those with small teeth counts (eg. 12T in 100dp, 13T and 14T in 64dp). I'm not sure if the skew cut worm wheels which the 2mm S.A. supply are available elsewhere.

I think the gearboxes from HighLevel et.al would be where I'd start for getting the gear train down the firebox and onto the axle. You may have to compromise a bit, because (as you know!) the point of the Crampton design was to put the axle behind the firebox and just under the footplate floor. You'll have to raise the floor a bit (at least in one place) to clear a gearwheel . It might be possible to hide a small raised bit behind the fireman having a rest on his shovel, or similar.

- Nigel