Author Topic: Magnetic gears  (Read 12418 times)

Offline R7

  • Propulsophile
  • Senior Member
  • *****
  • Posts: 2738
    • Don't worry.. we can still be fans of OSC and SNC
  • Liked: 948
  • Likes Given: 662
Magnetic gears
« on: 04/10/2014 03:11 PM »
Durable gearing is a big challenge in rocket engines and other off-world applications. Some turbopumps need mechanical gears because impellers for different propellants (RL-10) and smaller kick stages (NK-33/AJ-26) need different rotation speeds than main turbine. Some gears were lubricated with fuel (IIRC H-1) others require separate lubricant. Rover drivetrains may have to cope with vacuum (lubrication problem), abrasive dust (sealing problem, eating teeths), wild thermal swings (affects meshing, lubricant properties).

Efficient non-contact gears would be nice, no?

http://www.magnomatics.com/technology/low-ratio-magnetic-gears.aspx

Quote
Contactless, high-efficiency, high-torque transmission with inherent overload protection

A magnetic gear uses permanent magnets to transmit torque between an input and output shaft without mechanical contact. Torque densities comparable with mechanical gears can be achieved with an efficiency >99% at full load and with much higher part load efficiencies than a mechanical gear. For higher power ratings a magnetic gear will be smaller, lighter and lower cost than a mechanical gear. Since there is no mechanical contact between the moving parts there is no wear and lubrication is not required. Magnetic gears inherently protect against overloads by harmlessly slipping if an overload torque is applied, and automatically and safely re-engaging when the fault torque is removed.
Advantages over mechanical gears

    - Reduced maintenance and improved reliability
    - Lubrication free
    - Higher efficiency than conventional gears
    - Precise peak torque transmission and inherent overload protection
    - Physical isolation between input and output shafts
    - Inherent anti-jamming transmission
    - Significantly reduces harmful drivetrain pulsations
    - Allows for misalignment/vibration of shafts
    - Very low acoustic noise and vibration

Same company also offers low speed high torque motors based on above principle

http://www.magnomatics.com/technology/pseudo-direct-drive.aspx

Quote
Electrical machine with fully integrated magnetic gear offering unrivalled torque density

The PDDŽ machine is a pioneering extension of the low ratio magnetic gear and was invented and demonstrated by Magnomatics personnel in 2005 and is widely regarded as the most significant advancement in electrical machine design for 20 years. This ground breaking technology combines the high torque density of the magnetic gear and the functionality and performance of a brushless permanent magnet machine to offer unparalleled torque output for direct drive applications.
Advantages of PDDŽ

    Significant size reduction over conventional direct drive machine
    Ultra high efficiency removes the need for ancillary cooling
    Reduced maintenance and improved reliability over mechanically geared drives
    Inherent torque overload protection
    High power factor (typically >0.9)
    Employs standard power electronic controllers
    Possibility for two output shafts with different rotational speeds

These might work well in rover wheel hubs, eletrical TVC etc.

Video explaining the principles:



Dunno what's the catch though ... there always is one? Discuss
ADˇASTRAˇASTRORVMˇGRATIA

Offline rklaehn

  • telemetry plumber
  • Full Member
  • ****
  • Posts: 1208
  • germany
    • www.heavens-above.com
  • Liked: 89
  • Likes Given: 163
Re: Magnetic gears
« Reply #1 on: 04/10/2014 03:38 PM »
Dunno what's the catch though ... there always is one? Discuss

- Uses lots of rare earth metals.

- Might require cooling for continuous operation because permanent magnets permanently lose their magnetic properties above a certain, not very high, temperature (80 to 200 degrees celsius).

Other than that it is quite a good idea.
Try the ISS 3D visualization at http://www.heavens-above.com/ISS_3D.aspx

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 700
  • Likes Given: 728
Re: Magnetic gears
« Reply #2 on: 04/10/2014 06:12 PM »
ahhh Perfect design concept to translate into a cheap 3D printed motor.   
What color would yoo like the sample print in?

wait for the videos






« Last Edit: 04/10/2014 06:17 PM by Prober »
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 9161
  • Delta-t is the salient metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 613
  • Likes Given: 318
Re: Magnetic gears
« Reply #3 on: 04/11/2014 01:58 PM »
Thanks very much for today's learn something new every day moment.  When was this device invented?
Sometimes I just flat out don't get it.

Offline Damon Hill

  • Veteran
  • Full Member
  • ****
  • Posts: 550
  • Auburn, WA
  • Liked: 72
  • Likes Given: 137
Re: Magnetic gears
« Reply #4 on: 04/12/2014 06:11 AM »
Can this concept transmit thousands of horsepower?

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3747
  • Earth
  • Liked: 147
  • Likes Given: 3057
Re: Magnetic gears
« Reply #5 on: 04/12/2014 06:55 AM »
Can this concept transmit thousands of horsepower?
There will be limits based on the strength of magnets, but you can order really long magnets.  I had some pretty large custom neodymium magnets made in China for an experiment a few years ago.  I was limited to about 2x2x12 inches because the guy's currie-cure oven wasn't big enough for larger.  But larger ovens exist and can certainly be built.  So...  Yes. 

Although I would love to play with some of these, I would guess that weight could be a prohibitive trade for rocket turbo pumps.  But haven't looked up the specs or emailed them, and don't know enough about the requirement to properly speculate.  If you do, please report back on this thread!   Like a can pump with multiple additive impellers, there might be a gradual step up/down with these too.
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline MP99

Re: Magnetic gears
« Reply #6 on: 04/12/2014 12:04 PM »
Although I would love to play with some of these, I would guess that weight could be a prohibitive trade for rocket turbo pumps.

For higher power ratings a magnetic gear will be smaller, lighter and lower cost than a mechanical gear.

cheers, Martin

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 700
  • Likes Given: 728
Re: Magnetic gears
« Reply #7 on: 04/12/2014 02:23 PM »
Can this concept transmit thousands of horsepower?
There will be limits based on the strength of magnets, but you can order really long magnets.  I had some pretty large custom neodymium magnets made in China for an experiment a few years ago.  I was limited to about 2x2x12 inches because the guy's currie-cure oven wasn't big enough for larger.  But larger ovens exist and can certainly be built.  So...  Yes. 

Throwing out suggestion:  Don't rely on China, obtain your own freedom to self manufacture and expand your research toolbox with a cheap 3D printer.   Can't even tell you about the project that's on my plate but it does involve magnets.  This project would be purely nutty a few years back, and frankly its nutty that its working.

2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3747
  • Earth
  • Liked: 147
  • Likes Given: 3057
Re: Magnetic gears
« Reply #8 on: 04/12/2014 02:35 PM »
Although I would love to play with some of these, I would guess that weight could be a prohibitive trade for rocket turbo pumps.

For higher power ratings a magnetic gear will be smaller, lighter and lower cost than a mechanical gear.

cheers, Martin
That quote from the magnomatics website might be correct. I haven't seen anything quantified, and wonder if the inner sheath would wear/crush under sufficient loads that the magnets move together.  Of course, the medicine for that might be bigger/longer magnets, and/or a multi-step-up approach, but that adds weight.  How does this compare to current differential turbo-pumps in rockets?  I don't know. 

Is a rocket turbopump likely to go above curie temperature on the way up or during re-entry? 
« Last Edit: 04/12/2014 02:39 PM by go4mars »
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8291
  • South coast of England
  • Liked: 282
  • Likes Given: 122
Re: Magnetic gears
« Reply #9 on: 04/12/2014 07:39 PM »
A second space application is to power the wheels of rovers.  Rovers have to deal with both dust and lubricants disliking vacuum.

Offline Elmar Moelzer

  • Senior Member
  • *****
  • Posts: 3062
  • Liked: 534
  • Likes Given: 778
Re: Magnetic gears
« Reply #10 on: 04/14/2014 02:16 PM »
- Uses lots of rare earth metals.
This is a problem that is usually exaggerated. Rare earth metals are not that rare, they are merely hard to extract and refine, which made it uneconomical due to the cheap competition from China. As prices have been going up, the other sources are becoming competitive again. So I am not that concerned.

Offline Asteroza

  • Full Member
  • ****
  • Posts: 547
  • Liked: 62
  • Likes Given: 2
Re: Magnetic gears
« Reply #11 on: 04/14/2014 11:09 PM »
It's not the refining per se that is uneconomical, it's the environmental protection equipment the EPA requires for US refineries that makes it uneconomical. If I remember correctly, quite of bit of thorium and other metals are "waste" from the process that must be handled per EPA rules, plus the usual air quality issues and employee safety. Part of the reason chinese rare earths are so cheap is they are skipping a lot of environmental and worker protections, at their peril. Though the increasing middle class in china will soon mean they will put stricter export limits to protect the resources for domestic use, so other countries will have no choice but to refine their own ore at additional cost. There is a major ore deposit and refinery complex in the US that is currently being warmed up from mothball status (shutdown due to chinese exports being so cheap), but completing the refinery improvements is a major capital cost so is proceeding slowly.

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 700
  • Likes Given: 728
Re: Magnetic gears
« Reply #12 on: 04/15/2014 03:19 PM »
It's not the refining per se that is uneconomical, it's the environmental protection equipment the EPA requires for US refineries that makes it uneconomical. If I remember correctly, quite of bit of thorium and other metals are "waste" from the process that must be handled per EPA rules, plus the usual air quality issues and employee safety. Part of the reason chinese rare earths are so cheap is they are skipping a lot of environmental and worker protections, at their peril. Though the increasing middle class in china will soon mean they will put stricter export limits to protect the resources for domestic use, so other countries will have no choice but to refine their own ore at additional cost. There is a major ore deposit and refinery complex in the US that is currently being warmed up from mothball status (shutdown due to chinese exports being so cheap), but completing the refinery improvements is a major capital cost so is proceeding slowly.

had my eyes on this tech and sad story for years.
 http://www.heritage.org/research/reports/2008/05/magnequench-cfius-and-chinas-thirst-for-us-defense-technology
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10408
  • Connecticut
    • Direct Launcher
  • Liked: 2356
  • Likes Given: 783
Re: Magnetic gears
« Reply #13 on: 04/15/2014 05:27 PM »
If I remember correctly, quite of bit of thorium and other metals are "waste" from the process ...

You do remember correctly, but the process would work both ways if more LFTR's were put in operation to replace the BWR's and PWR's powering the grid. In the mining and extraction of Thorium to fuel the LFTR's, part of the "waste" byproduct is the rare earth metals. So just powering our nation would result, as a byproduct, in the production of ample and economical supplies of the rare earths.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline simonbp

Re: Magnetic gears
« Reply #14 on: 04/15/2014 07:44 PM »
Dunno what's the catch though ... there always is one? Discuss

If it's using permanent rare-earth magnets, the catch is almost certainly mass. The mass of mechanical gear+lubricant is almost certainly less for a given spec than a magnetic coupling.

Offline R7

  • Propulsophile
  • Senior Member
  • *****
  • Posts: 2738
    • Don't worry.. we can still be fans of OSC and SNC
  • Liked: 948
  • Likes Given: 662
Re: Magnetic gears
« Reply #15 on: 04/15/2014 07:59 PM »
Can this concept transmit thousands of horsepower?

One of their brochures in download section discusses wind turbine application transferring >10MW. Obviously the size, torque and rpms are way different than any spaceflight application, but just an example. The paper also has image of 300kW test-setup. Compared to the motor the gear box doesn't look that big, and the rpms are still way below turbopumps.

I informed the company of this thread via their contact form asking if anyone there could answer these good questions.
ADˇASTRAˇASTRORVMˇGRATIA

Offline R7

  • Propulsophile
  • Senior Member
  • *****
  • Posts: 2738
    • Don't worry.. we can still be fans of OSC and SNC
  • Liked: 948
  • Likes Given: 662
Re: Magnetic gears
« Reply #16 on: 04/15/2014 08:03 PM »
had my eyes on this tech and sad story for years.
 http://www.heritage.org/research/reports/2008/05/magnequench-cfius-and-chinas-thirst-for-us-defense-technology

Is former Magnequench now Molycorp ?

It seems they are again mining in Mountain Pass, CA.
ADˇASTRAˇASTRORVMˇGRATIA

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6116
  • Lafayette/Broomfield, CO
  • Liked: 2154
  • Likes Given: 749
Re: Magnetic gears
« Reply #17 on: 04/15/2014 09:19 PM »
I saw these guys a few years ago. A friend's company has done some work on brushless DC motor-driven rocket centrifugal pumps (electropumps?). One of the limiters on how big of a pump you can run was the available high-RPM BLDC motors. They had some higher power motors, but typically their RPMs were too low, so I had been looking for a low-loss gearing solution that could handle stepping the RPMs up to what their pumps could use, when I found these guys.

Unfortunately I haven't yet had the time or money to try them out, but I've always wanted to for robotics applications.

~Jon

Offline Asteroza

  • Full Member
  • ****
  • Posts: 547
  • Liked: 62
  • Likes Given: 2
Re: Magnetic gears
« Reply #18 on: 04/15/2014 11:14 PM »
Launchpoint allegedly had high RPM brushless DC motors, claiming very high power density.

http://www.launchpnt.com/engineering-services/electric-motor-design/

Claim can do potentially 20K RPM  and 2000 HP (at the same time?). They have demoed UAV scale motors and have a SBIR to demo a replacement electric tailrotor for a helicopter.

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 700
  • Likes Given: 728
Re: Magnetic gears
« Reply #19 on: 04/16/2014 01:42 PM »
had my eyes on this tech and sad story for years.
 http://www.heritage.org/research/reports/2008/05/magnequench-cfius-and-chinas-thirst-for-us-defense-technology

Is former Magnequench now Molycorp ?

It seems they are again mining in Mountain Pass, CA.

Yes
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Tags: magnetic gears