LRK vs CDROM Motors

[howard]

Could someone explain the difference between these two types of motors? But, please don't refer me to a site in German or to a technical article I don't understand. I've read through a number of long threads within RCGroups, but am still confused. LRK seem to be limited to a stator of 12 poles with windings on every other pole. Then I read about a type of LRK configuration with windings on every pole :? . CDROM type windings can also contain 12 poles. Are LRK type of motors more powerful? Why aren't people building more of these types of motors? Will kits be available through GB that will allow hobbyists to build a LRK motor?
Thanks,
Howard

[Happy|Harry]

the main difference (not including wind pattern etc etc) is that lrk's provide more torque than CD motors for a given stator diameter.

the lrk's are all 12 tooth stators with either 12 or 6 teeth wound, and either a 10 or 14 pole bell, where as all CD motors have a 9 tooth stator ane either a 6 or 12 pole bell (using the standard ABCABCABC).

on providing custom parts for the 12 tooth GB stators these type of things take time to design/machine/test, then to get quotes from machine shops etc, but steve is working on it :)

also lots of LRK motors have been built but mostly by people who have acess to a lathe and/or a mill to make custom cans and mounts for them

phil

[jimbo]

Why aren't people building more of these types of motors?
Short Version:
ya need a lathe\machine shop to build them (So far... see Happy Harry's note)

[Happy|Harry]

has your hand ever unexplicably risen jimbo ;) :D

phil

[ScubaSteve]

On that note, Phil, we've started the ball rolling on GBx hardware for the 25mm 9 and 12 poles... :wink:

Also, we should be have some serious quantities of GBx stuff for the 22.7 coming in over the next week. Talkin' LOTS. After this first delivery, I don't expect to have a stock issue with them again.

Then the 25mm stuff will come, and after that, 20mm GBx stuff!

[Happy|Harry]

On that note, Phil, we've started the ball rolling on GBx hardware for the 25mm 9 and 12 poles... :wink:


sweet! :D


Also, we should be have some serious quantities of GBx stuff for the 22.7 coming in over the next week. Talkin' LOTS. After this first delivery, I don't expect to have a stock issue with them again.


that's great news as i have a couple of doubles to build!


Then the 25mm stuff will come, and after that, 20mm GBx stuff!

this should keep the uber light indoor folks happy ;)

phil

[ScubaSteve]

yeah especially if i can find that dxf so we can get rollin' on those 10mm stators:).

[JimS]

Yes please, 10 mm stators! :)

[Happy|Harry]

yeah especially if i can find that dxf so we can get rollin' on those 10mm stators:).

:o :D :wink:
phil

[howard]

Thanks Phil for the explanation. Based on this table: http://www.alexrc.com/nutpol_e.htm it suggests 8 or 10 as an optimal pole number for a 9 rotor CDROM motor. Did I misread the chart?

On that note, Phil, we've started the ball rolling on GBx hardware for the 25mm 9 and 12 poles... :wink:

Steve, so the 12 pole 25mm would be LRK wound? What would be the performance difference compared to a CDROM motor?

Also, our local electric fly club (http://www.marcee.org) just hosted a Go Brushless workshop held over two consecutive Wednesday nights. One of the members lead the build event and everyone was successful getting the motor running even those that missed the first night. I don't have the final count, but the class was pretty full.
Howard

[ScubaSteve]

Howard,

Very cool. Did you guys take any photos of the workshop? I'd be very interested in seeing them:)

Maybe i'll be able to make it to your 2005 Fly-in! Plan on 'touring the circuit' next year with Steve SR... just gotta find someone to hold down the GB fort while we're gone:?.

[howard]

Steve,
There were 32 attendees of the workshop running over two Wednesday evenings. This included 6 Father/Son teams. The instructor pre-pressed the shafts into the rotors of all 50 kits ordered. He also soldered the mounting tube and added magnet spacers to help with placements. Very helpful. Maybe something you could do for the kits (hint hint :wink: ).

If you guys could attend that would be fantastic! Your booth will probably been swarming with now highly interested and highly skilled CD-ROM builders. It's a great event and a super site. Probably the best kept secret in electric only fly-ins. Consider yourselves officially invited!

Howard

[ScubaSteve]

Hmm actually we'd probably come to the first few events as an attendee rather than a vendor... :?

[ron_van_sommeren]

The lrk/sps windingprinciple optimises for torque (which does not mean that an a lrk motor cannot rev! +35.000rpm in Christian Lucas' boats). Maximum power is mainly determined by the ability of the motor to get rid of excess heat. Different windingdiagrams teeth/magnet combinations give different motor characters.

English windingtable and windingcalculator-tool:
http://www.powerditto.de/powerditto/Kombinationstabelle2.html

The lrk 'bible'
http://www.torcman.de/peterslrk/index_eng.html

[howard]

Ron,

Thank you for the response to my question. I have reviewed your link and reviewed the winding and magnet options, but still unclear how each type/number affects performance i.e. torque, power etc. Do you know where this is explained concisely in plain english? I am a member of your group and rcgroups and still find it difficult to comprehend these basic concepts.
Thanks,
Howard

[ron_van_sommeren]

Maximum power does not so much depend on number of magnets and number of poles. It depends on the ability to get rid of excess heat, i.e. size and the amount of metal. The number of magnets, teeth, windings and type of winding diagram determine the motor character: what power/current and what rpm, point of maximum efficiency and point of maximum power.

Have a look at the table, for a certain number of teeth you can use a certain number of magnetpoles OR double that number (within the boundaries given by the colours). More magnetpoles will give more torque, fewer magnets will give more rpm.

[Q]

yeah especially if i can find that dxf so we can get rollin' on those 10mm stators:).

Hey Steve, any news on those 10mm stators? I'm sure there's a lot of people looking for them.
Or were you jsut joking? In that case I was too eager for this product to get the point. :-/