Completely Stumped: High RPM (20,000) Drive Problem

No, not really.

Get a bigger flywheel and turn it more slowly.

Or, get some help with the simulation, which you do not identify.

Look for a tutorial.

Ramping it gradually up to speed via a VFD?

Its not so much the load of the motor end, Its most the motors I'm finding won't exceed 3600 RPM which means I need to find some way to gear up the speed and almost all components I'm finding aren't rated to perform above 7200 RPM, I haven't heard of AC or DC motors that will ramp up to 20,000 RPM

You are probably not searching for the correct type of motor being there are lots of motors around us we use all the time that run well over 20,000 - 30,000+ RPM.

The term you are looking for would be most often referred to as high speed spindle motor and I know there are units out there that can easily put out 10+ HP (7.5 KW) at 20K RPM.

Granted a brand new one might set you back several thousand dollars though.

Spindle motors are perfect, thank you so much!

To clarify, I didn't mean to imply that the motor would attain 20,000 rpm. I was still envisioning a belt speed-increasing drive. The VFD would help to take care of starting current issues.

Various posters have given some ideas, I'd just add that on domestic washing machines the motor runs at that sort of speed, drum speed can be 1650rpm (maybe higher nowadays) and ratio drum/motor pulley ~ 12.5. Not 10 - 20hp though.

THe motor on a front loader is fit with a very small pulley to drive the belt around the circumference of the drum. I am pretty sure the controller has to spin that motor at least 15k. I cannot hear it anymore after that.

What are the dimensions and composition of the flywheel..?....you realize you will be limited in dimensional and material design due to inertial forces at this speed...I would use pneumatic or hydraulic probably...

https://en.wikipedia.org/wiki/Flywheel

https://en.wikipedia.org/wiki/Flywheel_energy_storage

https://www.youtube.com/watch?v=SQFuzFzJ9wg

That is an issue we're working with. Its amazing what even the toughest metals will begin to do with that rotation.

Oh thank you, I will look into this for sure

The only thing I've had experience with at 20K rpm is a dentist drill! Air power!

Never used a vacuum cleaner or most any electric power tool like a angle grinder, drill or saw with a universal/brush type motor?

20K RPM before the gear reduction system is just getting up to speed for most to them.

Ooh, I'm just dying to get my hands onto a 20-hp angle grinder. Hooee, I could get through a lot of slag in a hurry!

This is a simulation!!!!!

OP is a student.

It seems materials may be more of a problem later.

OP what are.you really asking?

SPEAK UP, I'm in a bar right now.

I was going to put a snarky picture of an angry drunk sitting at a bar here but I knew that if I did SE would just one up me on it.

Next time I'll send you a selfie.

I was only there for two beers and it was a happy time. Nobody in the place was under 50.

They were probably all discussing how to keep kids off their lawns.

LOL!

What are you simulating the harvest of? Somethings put more of a shock load and vibration on the machinery than others.

My first thought is anything going that fast with any sort of mass is don't stand anywhere near it when doing the initial startup.

BAB

We are putting it into a storage container lined with 3 inches of High Impact Plastics, not looking to be anywhere near this when it starts up....

As it was mentioned previously, most motors at 20 HP, you're talking 3600 rpm standard. I've never seen anything above that used in industry. So, if you want to go faster rpm, you'll have to use a gear box and/or belt pulley ratio as you mentioned.

Still, I would not feel comfortable spinning a flywheel at 20,000 rpm! That's just crazy talk, IMO. Balance becomes a huge factor. Large jet turbines operate around 10,000 rpm, so keep that in mind. You could find some resources looking at turbine designs.

The 20HP seems a little low to me, off the cuff. Did you calculate the work required to rotate the mass at the required rpm, then back that into the required work of the motor (adding in the gearbox/belt losses)?

GA. I forgot about aircraft motors.

You can do it, but it weakens the motor:

http://ecatalog.weg.net/files/wegnet/WEG-application-note-cfw-09-400hz-output-frequency-an003cfw09-brochure-english.pdf

Still, good call!

Sounds like you want a centrifuge motor. Direct spindle drive and sophisticated control.

If you've ever been near a big centrifuge in operation you will appreciate the fact that whatever they are spinning is inside a sturdy container.

A gyro motor would also do it.

Sorry but my first advice is to check your calulations.

f you are having troubly simulating that speed, then it's probably not what is used in practice.

What are you "harvesting"? If this is like a conventional grain harvester, then the speeds are adjusted so that they don't damage the grain. Fastest that I'd expect to have seen on our headers/harvesters would be 1800rpm driveshaft speed through a 3x step-up belt drive in the adjustable speed drive. (Ingenious V belt system with split cones held together with tension springs so that both pulleys could be "infinitely adjusted" by changing the depth of the "V" at each end.)

You would get a 3' wide "scientific" harvester that would run on 20HP, or a rice harvester from Japan where their fields are very small.

A harvester head running at 20,000rpm would smash the grain, the straw would also be turned to dust.

I suspect also that you would have trouble turning corners at the end of the fields with that flywheel?????

If this is not for grain, then please disregard these ramblings.

It is a tree harvester. There is a ISO standard for the specs in order to test safety equipment we are using/expanding upon :)

The Alexanderson generator of high frequencies in the early 1900s was driven by an electric motor, spinning the generator at 20,000 rpm thru a flexible shaft with intermediate bearings (1/64 in clearance) to steady it thru the critical speeds at 1700 and 9000 rpm and take up excessive end thrust. The generator had 300 poles around the perimeter of a nickel-chrome steel disc, with a rim speed of 1047 fps (700 mph) and centrifugal force 68,000 times static at the rim. Safety factor >6. The rotor was driven by a 10 hp shunt wound motor running at 1250 rpm, connected by chain drive to a shaft running at 2000 rpm. The shaft was connected by De Laval gearing, ratio 10:1, to the flexible drive shaft. The system used forced lubrication. Heat! Generator output was 2000 Watts at 100,000 Hz, about 30% efficiency. Whatever design you come up with, first do all the calculations you can to reveal any possible weaknesses. Plan first! Where possible, test individual parts of the system to reveal possible problems before you put the system together. Ref W H Eccles, Wireless Telegraphy and Telephony, 2nd ed, Benn Bros London 1918

Gearbox. Sure you could find one out there that will increase your 3600 RPM motor to 20,000 RPM more or less. It's only 5.555555555 times speed increase. Just have to watch out what you need for starting current.

Compressed air.... and lots of it.

Die Grinders can hit 20,000 RPM, with them putting out 3/4 HP.

Some of you guys mentioned Spindle and Aircraft motors. I ended up looking into both of those and it looks like a spindle supplier will be able to get us what we need.

Thanks so much for the helpful comments!

(Also, in case anyone was curious I meant to say tree harvester- like the Ponsse H8 unit that runs of the chain hydraulically)