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Sep 08, 2001, 12:29 AM
homo ludens modellisticus
Ron van Sommeren's Avatar

English lrk-torquemax diy brushless outrunner site & mailing list

Peter Rother is working on an English version of his lrk-torquemax diy brushless outrunner site. Now it includes translations, drawings, pictures and diagrams of the original Elektro Modell 2000/4 and 2001/1 articles: part I part II
His own very interesting lrk-torquemax design is not in English (yet):

LRK-torquemax mailing list:

Regards, Ron van Sommeren
Last edited by Ron van Sommeren; Oct 13, 2001 at 07:04 AM.
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Sep 09, 2001, 04:30 PM
Registered User
Hi Ron,

Keep posting, I know I'm not the only one taking notice.

Best regards, John
Sep 09, 2001, 06:32 PM
broom driver
I like the site

I am curious about the materials used for the stator plates.

I have looked but find it very hard to get a good idea for the best material

I understand that low cost industry uses a cheap metal called transel or lowstel in the uk which I understand is an "electrical metal" used in transformers as well.

I have looked at nickel alloys and also the cobalt alloys but I understand they have to be annealed at 1693 C in a dry hydrogen enviroment and deviancy from this causes the metal to become scrap.

I would be curious to know which LRK motors have preformed the best depentant upon where the stator material was gathered from.

I understand some HD use cobalt alloys but industrial motors use the cheapest they can get

Has anyone made a comparison ???

Sep 10, 2001, 04:13 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
From the lrk-torquemax mailinglist:

christian.johansson@... asked:
> What material is a good one for the sheet material used in the stator?
> I got access to laser cutting equipment so to produce my own parts is not a problem.
The thinner the better, less eddy-current losses, 0,5mm, 0,3 mm.. That is, if you use the same quality.

> I found a company in India that got some information about standards and suppliers

> If I will make my own parts, what shape should the stator have?
Shape picture::
Translated from (German):
There is poor quality 0,35mm sheet metal(e.g.V650-35A, 6,5W/kg at 1,5Tesla and
50Hz) and also good quality 0,5mm (e.g.V270-50A, 2,7W/kg at 1,5Tesla and 50Hz).
You can hardly get your hands on really good quality metal sheet, the industry
goes for cheap instead of performance/eta, usually V800-50A is used (three times
higher iron losses than V250-35A)!

Tip: Disassemble your old brushed engines, power drill, wife's blow dryer (or your own ), computer fan, hard-disk, CD-ROM, DVD, or pump for stator material.

Go to a E-motor 'coiler/refurbisher' and check his bin for scrapped motors.
Met vriendelijke groet, Ron van Sommeren
lrk-torquemax mailinglist monitor

[This message has been edited by Ron van Sommeren (edited 09-10-2001).]
Sep 11, 2001, 03:04 AM
broom driver
I have been looking at these sites and found the following imformation software for designing motors

for site showing a few different lamination materials.
Sep 11, 2001, 04:02 AM
broom driver
maybe this web page may help other LRK motor builders
Sep 11, 2001, 01:02 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Thanks Dan,

I took the liberty of posting your links in the lrk-torquemax mailing list.

Met vriendelijke groet, Ron van Sommeren
Last edited by Ron van Sommeren; Sep 11, 2001 at 01:08 PM.
Sep 29, 2001, 05:06 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Peter Rother has updated his English lrk-torquemax site:
His German version (still) has more pics:

A design and some pictures: (requires Acrobat reader, free download from Adobe's site)
Stator material from Robbe pump:

micro lrk:

lrk-torquemax mailing-list:

New source for magnets, stator metal sheet stampings and a kit:

An outrunner in action, not an lrk-torquemax, though they look pretty much the same:

Met vriendelijke groet , Ron
Last edited by Ron van Sommeren; Sep 29, 2001 at 05:46 PM.
Oct 01, 2001, 02:03 AM
Flying Free
erashby's Avatar

What is the point of DIY? Is this motor better than factory motors?

It seems like a lot of trouble to go to-building your own-just to get a brushless motor? Is this motor better than those you can buy? More power? More efficient? Or is it the thrill of building/DIY?
Oct 11, 2001, 08:05 AM
homo ludens modellisticus
Ron van Sommeren's Avatar

The lrk-torquemax principle features a high torque at lower rpm, compared to a conventional brushless layout. There's no need for a gearbox, which means LESS WEIGHT, LESS LOSSES, LOWER COSTS and NO GEAR NOISE. The motor can swing a BIGGER PROP which results in an even HIGHER EFFICIENCY. It can be tailored to the plane's needs.

The LRK-torquemax is an inside-out motor, the coils are stationary, housing and magnets rotate. This has the additional benefit of good magnet cooling and the coils are not stressed by centrifugal forces. The motors built to date by e-modellers, range from slow-flight to 3kilowatts!!! and even direct drive versions for helicopters.

Met vriendelijke groet, Ron van Sommeren
lrk-torquemax mailing list monitor
Oct 11, 2001, 08:13 AM
homo ludens modellisticus
Ron van Sommeren's Avatar

construction articles

Here are the direct links to the construction articles: part I part II (top-level link)
Last edited by Ron van Sommeren; Oct 13, 2001 at 07:05 AM.
Oct 12, 2001, 09:34 PM
Flying Free
erashby's Avatar

Brushless motor DIY

Thanks for the info. Now I understand why it is worth DIY. If I only had the time. Does anyone make a kit? Or better yet does anyone want to make me one for $$$? How much? How long does it take to make these motors? What planes are people putting them in?

Just one more project for my list. Thanks.
Last edited by erashby; Oct 13, 2001 at 12:46 AM.
Oct 13, 2001, 07:00 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
They range from slow flight to 3kilowatts and helicopters. Have a look here: under 'motoren' 'einbauvariante' and 'andere'.
Don't let the German deter you , it's mostly pictures, tables and diagrams. You can use, or for translation.

Kits, magnets, stator material, shafts: 'news' 'drehteilesatz'
Peter Rother of is also thinking of making a batch.
Magnets, stator material.

The first one will take the most time, I heard 10-20 hours , the others will probably take a lot less time.

There is a commercial outrunner manufacturer, although these actro motors don't use the lrk-torquemax principle (every other tooth empty):, click 'English' in left frame. Have a look at the prices one Euro is 0.9-1.0 USD. One USD? ROFL, that's what we here on the old continent would like to see ;-)
Oct 14, 2001, 07:02 PM
Flying Free
erashby's Avatar
Thanks for the web-links. They were helpful. German doesn't bother me, just slows me down. Ich kann ein bischen deutsch.
Has anyone in the USA built one of these. I would like to talk/e-mail with him.
Oct 15, 2001, 05:03 AM
homo ludens modellisticus
Ron van Sommeren's Avatar

mailing-list members


There is a number of Americans & Canadians on the list/ . I can't tell how many because of some hotmail/yahoo addresses. I did send you the heavily mutilated member-list in two private messages, too big to put it here. This will give you an impression.
Last edited by Ron van Sommeren; Oct 15, 2001 at 05:07 AM.