View Full Version : OT - What can you do with this Motor?

06-30-2009, 11:48 AM
That weird Dyson guy, has invented a new Motor for his Vacuum Cleaners.

Tops out at 104,000 RPM.


Using a 1/16" Dia. Mill, the FPM is only about 1700 feet per minute.

Tom M.

Michael Edwards
06-30-2009, 11:58 AM
That's really movin. Hate to see what happens when she gits out of balance. :eek:


Liger Zero
06-30-2009, 12:32 PM
That's really movin. Hate to see what happens when she gits out of balance. :eek:


You buy another vac, that's what. :D

06-30-2009, 05:36 PM

I wonder if that has any interest for us... Grinders

06-30-2009, 06:06 PM
I'd be afraid of burnng anything I tried to grind or polish with something going that fast.


06-30-2009, 10:47 PM
Does it include a Kevlar jacket to contain the shrapnel when the impeller decides to spit the bit?:D

J Tiers
07-01-2009, 12:40 AM
Interesting... But the hype is a little overblown...... it ain't that new.

There is a "switched reluctance motor" in every Maytag Neptune washer...... Emerson made it originally, and it has been in that product since day one, 10+ years ago....... They pushed the type for a while, but it went out of style for various good reasons.

Evidently it has been "rediscovered".

They do have some advantages for high speed, no rotor windings, for one thing, but have a downside as well, since tehy are less efficient, usually, and

John Stevenson
07-01-2009, 05:19 AM
They do have some advantages for high speed, no rotor windings, for one thing, but have a downside as well, since tehy are less efficient, usually, and

Dammit has JT been abducted by the Dyson development staff for blowing the gaff ?

Read here later to get the latest update in the missing JT saga.


07-01-2009, 06:30 AM
100k rpm isn't that high. Plenty of small DC motors will do that easily.

A related motor is the variable reluctance stepper which can turn at very high step rates. It has no magnets and the rotor is simply a piece of iron with slots in it. The vanes are attracted by a multiphase rotating field in the stator coils. They are at least three phase but can be more. They have a very high step angle resulting in a very low number of steps per rev. I built a flat bed plotter with some back in the '80s that used 12 step per rev VR steppers and it would do over 3 inches per second with a minimum step size of .001 inch. That's over 180 inches per minute over 20 years ago. It's also 3000 steps per second that I generated from hand coded machine language driver software.

That's 15000 rpm and while it could do that I had to slow it way down to actually plot anything. Plotting characters at that rate it would try to shake itself to pieces faster than a helicopter.

J Tiers
07-01-2009, 09:43 AM
The "switched" vs "variable" reluctance motors are quite similar, and only a motor geek really cares about the difference.

The good thing is that with no windings, there is nothing to fly off, or "birdcage" on the rotor.

A great many integral motor internal grinding spindles have been made over the years wich turn at well over 100k rpm.

It's hardly a stretch to turn 10x the rpm of a large turbojet, when the device is apparently about 1/30th the diameter, or less. But marketing departments must earn their keep.

Dyson has a rep to keep up, and "breakthrough tech" is apparently their "marketing hook line", used at all opportunities. Floor cleaners are not exactly the place to search for cutting edge technology, usually, although Dyson seems to apply known technology effectively ;)

07-01-2009, 10:53 AM
A commercial airliner engine turning only 10,000 RPM. or is that just the Turbo-fan on the front?

07-01-2009, 11:58 AM
Actually I think the various stages of a jet acft engine turn at multiple speeds. So it's not really too meaningful to speak of a jet engine rpm.

I may be wrong. Maybe someone else can correct me or elaborate further.

07-01-2009, 01:02 PM
Most are two stage, a high rpm high pressure gas generator stage and a low pressure low rpm propulsion stage that turns the fan. The shafts run inside of each other and in the hot end is the low rpm turbine that turns the bypass fan at the front. Modern turbojets aren't really jets, they are ducted fan engines with a turbine power plant. The great majority of the thrust comes from the fan which is really just a propeller with a lot of blades in a shroud.

Rolls Royce has some three stage turbines I think but turbine designers hate gears since they always wear out faster than any other part.

Pure jets haven't been used on commercial aircraft for decades as they are extremely loud and inefficient. One of my favorite pure jet aircraft is the Vulcan Bomber, also known as The aluminium Overcast. Note the very small size of the engine exhausts. A pure jet has no bypass fan and relies only on the heating and acceleration of the gasses passing through the engine itself.


07-01-2009, 02:41 PM
Only two or three stages huh? I thought they had more than that, like maybe 5 or 6.

To me one of the biggest (and best appreciated) advancements in aviation is how they've quieted down aircraft engines over the years. In 1966 I was attending school at San Jose State, and lived pretty close to the traffic pattern there, which was very busy. You almost couldn't carry on a conversation outdoors much of the time. Now I live about 7 or 8 miles from the airport, but right under the approach path to the prevailing runway, and rarely notice anything other than the heavy military or the occasional fighter/trainers overhead.

07-01-2009, 03:36 PM
When I say stages I'm not talking about the number of wheels but the two main sections of the engine. The fan drive has only two wheels, the power wheel in the hot section and the bypass fan up front.

To me one of the biggest (and best appreciated) advancements in aviation is how they've quieted down aircraft engines over the years.

That is entirely due to the use of high bypass engines. It's a very important byproduct of the fact that the hot, turbulent exhaust is encased in cool laminar airflow. The mass of the bypass air and the velocity difference prevents efficient transfer of sound laterally. It's basically a transparent muffler. Engines are rated by the horsepower and the bypass ratio. The bypass ratio is calculated based on the weight of the air in lbs. A high bypass engine may propel as much as 6 to 8 times (I could be out of date on that number) as much air via the fan as from the exhaust of the turbine so it really is a fan jet engine. They are using this type of engine in military engines now also although much more compact of course. They get far better gas mileage than a pure jet.

07-01-2009, 03:52 PM
So Evan... Would a Pure Jet be similar to a Ram Jet?

Tom M.

07-01-2009, 06:22 PM
No, with one major exception. A "pure" ramjet has no moving parts except the engine itself. It relies on the supersonic shock wave at the inlet to both slow down and compress the air to subsonic velocity within the engine where compression heating provides sufficient temperature for ignition as fuel is sprayed in. The combustion gasses expand out the back and thrust is produced.

The exception is the J58 turbo-ramjet used in the SR71. It is a hybrid engine and switches to ramjet mode at supersonic speeds. It's easy to tell there is something different about it when you look at the exhaust.


Those are called thrust diamonds and you only see them in a supersonic exhaust plume. The test stand for the engine supplies it with supersonic intake air. That is done by pumping up a "tank farm" of air receivers to high pressure and then blowing them down all at once to feed the engine intake.

07-01-2009, 07:05 PM
You don't need supersonic inlet conditions to get shock diamonds in the exhaust. I've seen seen them multiple times in low level afterburner passes by F-15's, F-16's and F-18's at airshows. The only times I've ever seen supersonic passes at airshows were at Edwards for the 50th anniversary of Yeager's flight where they did it on purpose, and once at Point Mugu, where an incoming cold front shifted the local mach number below the speed of an F-14 who was supposed to perform a low level fly-by at .95 mach. Or at least that's how they explained it away afterwards while everyones ears were still ringing and all the car alarms were going off.
Jet engine designers may hate gears, but they must hate turbine blades and stators more. GE and Pratt & Whitney are both developing Geared Turbo Fans for the next generation of transport engines. Pratt engineers say that they will save ~1400 pieces (!) from the hot section assembly by driving the fan off of the high pressure turbine. Those hot section parts are where most of the manufacturing and maintenance costs are.

07-01-2009, 09:17 PM
You don't need supersonic inlet conditions to get shock diamonds in the exhaust

No, you don't, but you only see them in a supersonic exhaust plume. Most jet turbine exhausts are subsonic and even if they start out supersonic they immediately drop to subsonic. Shock diamonds are a string of solitons in the gas flow with a soliton being a self reinforcing solitary wave pattern. It takes a very high velocity exhaust to produce them.

I have heard many a sonic boom from when I was a child. We lived directly under the test flight path of the XB70. It made a very distinctive double boom. It is also possible for a sonic boom to be generated by an aircraft treling below mach 1. If the conditions are just right or the aircraft hits some clear air turbulence portions of the airframe can generate shock waves momentarily.

07-01-2009, 09:26 PM
BTW, the plans for a nuclear ramjet are on the shelf sitting there. The engine design is fully ground qualified for flight test. It was built and tested in Nevada back in the 60s but was canceled for political reasons. It required no fuel other than the uranium fuel rods as it relies on simply heating the air as it passes through the reactor. The design is dead simple and generates only trace amounts of free isotopes in the exhaust due to slight erosion of the ceramic core cladding as it operates. An aircraft so powered could in theory stay aloft for months.

07-03-2009, 10:58 AM
Didn't a German? company recently anounce a 1 million rpm motor that would be the bleeding edge of technology. This would be nothing but a marketing hook, as stated above. psssht!

This dyson guy is a marketing specialist, and he has managed to turn a vacuum cleaner into the next high tech must have gadget for guys. The dyson vacuum isn't revolutionary for technology its the styling that sells and has 24 year old guys bragging to each other about their new vacuum cleaner.

What would a vacuum cleaner need a 100k rpm motor for anyways? I would think that a good cleaner motor should have lots of volume, good efficiency when restricted and have such a service factor rating that it would never overheat when subjected to ignorant users of consumer equipment that will stall it out or run it restricted.

07-03-2009, 11:05 AM
How's it going Tryp? I don't know if you caught the thread but I now have an original Whipp shaper vise for the shaper you gave me. Dennis (DP) gave it to me in exchange for some jewellery I made. Long story, in the archives.

Have you had a chance to visit Standard Modern yet?

07-03-2009, 11:34 AM
So this motor is basically a stepper with an electronic control to 'step' it at whatever speed needed?

At first I thought it was one of those that uses hal effect sensors to simulate a commutator.

I have a direct drive CD player spindle motor in pieces right now, I wonder if that is an example of the motor type referred to in the original post? It has 9 windings, no visible feed back mechanism and a permanent magnet in the spindle/hub.


07-03-2009, 11:39 AM
HEPA??!, hell we used to call em a cyclone.

BTW Evan, how did they run the control rods in them there nuclear jets?

07-03-2009, 11:50 AM
I don't recall for sure. I seem to remember they were run from the intake side. There are descriptions online somewhere. Considering the materials we have now they could probably build one with ten times the efficiency and probably unmeasurable contamination. Imagine how that would affect the long distance travel business.

07-03-2009, 11:52 AM
Now ya gone and dun it Evan!

An all them oil companies know where you live :eek:

07-03-2009, 12:18 PM
It has 9 windings, no visible feed back mechanism and a permanent magnet in the spindle/hub.

It's done by sensing back emf. The magnets generate a signal in the drive coils as they turn and that is sensed to provide phase information.

07-03-2009, 12:21 PM
So is that anything like a resolver?

07-03-2009, 12:35 PM
By resolver I presume you mean the remote indicators used on devices such as a wind cock so the reading can be seen on a dial elsewhere.

The answer is that it somewhat of similar. The drive amplfiers are looking for a consistent rev to rev signal that they produce. It doesn't really directly read the rotor position. The back EMF changes the pulse shape that the amplifier produces and by sensing that via a sense resistor and integrating that over a portion of each rev the phase information is derived and the timing changed accordingly.

What looks like a single disk or ring magnet in that sort of motor is really the equivalent of a series of independent magnets. They are magnetized in a multipole pattern. You can determine that by passing a small magnet over the disk. Or, you can sprinkle some cast iron swarf on the motor magnet if you don't mind contaminating it.

07-03-2009, 12:40 PM
OK Evan, catch your drift.

BTW, I still have several resolvers from that Russian radar.
I'd be happy to send you a couple or 3 to play with if you have a use for them.

Only one I've used so far, I took out the rotor and stator and used the SS housing for an outdoor surveillance camera :D