Super High Speed Spur Gears

[Joe PageParticipant @joepage27051]

Hi,

I have a 4kW electric motor at 50,000 rpm but I need a final drive of 150,000rpm

Realistically what Is the possibility of using spur gears?

And if so what material would you recommend I make them from, and minimum footprint?

Do you think complete submersion in oil would cause too much friction?

The input speed will mostly hover around 20,000rpm, but in short bursts for maybe only 30 seconds it will spin up to 50,000rpm. This is all just the "idea" stage but my gut feeling is they wouldn't last two seconds.

Thanks

[Joe PageParticipant @joepage27051]

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

It is a matter of how strong the gearwheel are in large diameter, considering centrifugal forces at high speeds before the gearwheel sprouts into pieces. Think it's unrealistic.

[David George 1Participant @davidgeorge1]

You can give Ondrives of Chesterfield a call or look on their web site. They made bespoke gears for a CNC mill when I still worked.

David

[Neil WyattModerator @neilwyatt]

Look at supercharger drive gears.

Neil

Edited By Neil Wyatt on 18/10/2017 08:40:39

[Rik ShawParticipant @rikshaw]

150,000 rpm? That’s fast! Back in the 70's when I was using a Hauser jig grinder a 80,000 rpm grinding head was the fastest conventional motor that could be fitted to the grinder. If you wanted faster, Hauser offered an air turbine head that went above that – 120.000 rpm if memory serves correct. >>

However, things have moved on since then (leaving me behind) and probably your 150,000 rpm is much more easily achievable. Excuse my musings.>>

Rik>>

Edited By Rik Shaw on 18/10/2017 09:40:56

[HOWARDTParticipant @howardt]

Oil immersion would be a non starter as heat would be generated very quickly. Air oil mist would probably work with a total loss system but I think at these speeds experimentation is the key. This would also work with the bearings and help keep temperature down. Gears would need to be ground and balanced on the shafts to a high degree.

[John PParticipant @johnp77052]

Hi Joe,

The enclosed page is from a gear book and gives some advice on pitch line
speeds and types of lubrication .

Your electric motor at 4 kw approx 3 Hp the output torque is low at
0.315 lb/foot you could use some small pitch gearing somewhere
around 0.5 /0.6 module ,for example a 21 tooth gear at 0.5 mod at
5000 feet per min pitch line speed would be 46,200 rpm.
As you are only using the high speeds for short bursts you may get away with
exceeding the 5000 fpm by three + times .
It is just something that you will have to try.

John

[John PParticipant @johnp77052]

Should have seen this earlier from my previous posting.

"Your electric motor at 4 kw approx 3 Hp the output torque is low at
0.315 lb/foot ".

Should have read.

Your electric motor at 4 kw approx 5.3 Hp the output torque is low at
0..563 lb/foot .

John

[duncan webster 1Participant @duncanwebster1]

I worked on gear boxes for gas turbines, which were fast but not that fast. They had a jet of oil pointed at the mesh, can't remember whether it was in going or outgoing side. I'm assuming this is all enclosed. You might need to think about cooling as well, at 98% efficiency the oil will have to take away 80 watts

[David George 1Participant @davidgeorge1]

The spindle gearboxes I worked on used an air oil lubrication system with a nozzel for the gears and two others on the bearings. About 80 psi through a venturi and then to the nozzles to a total loss collection tank which always needed emptying, forgotten by the operator. (error lube system spindle won't run)

David

[Tim StevensParticipant @timstevens64731]

Whatever you do, please remember the rules about centrifugal force (as it used to be known). A burst gear at that rpm will have quite a lot of energy …

Tim

[Neil WyattModerator @neilwyatt]

This may give you some ideas:

http://www.sportrider.com/sportbike-news/new-kawasaki-h2-video-reveals-planetary-gearset-drive-supercharger

[Clive FosterParticipant @clivefoster55965]

Lubrication won't be trivial. Probably need to be synthetic as the shear on the oil film between meshing teeth could be ferocious at those speeds. Any interruption could be fatal to the device. If the budget can stand it one of the vacuum deposited anti wear coating might prove a prudent investment. My experience with such has been positive.

Clive

[SillyOldDufferModerator @sillyoldduffer]

Wouldn't ensuring balance also be a major problem? I suspect the forces in an unbalanced system at 150,000rpm might easily get out of control.

An intriguing project Joe – please keep us posted!

Dave

[Joe PageParticipant @joepage27051]

Thanks for all of the replies, some very useful information here.

Neil has just pointed out exactly what I'm trying to achieve, I did consider a planetary gear set at first but the ring gear was the thing bothering me with the high speeds, plus it's something I have never made before.

So my idea is to produce an electrical supercharger with a very small footprint, it's one of those proof of concept projects of whether it can be done. I'm trying to make it a compact modular system so that they can be paralleled up for more power, considering it takes about 10kW of power to boost a car from 140, to around 200bhp is probably a reason they're not produced, a project never the less.

So far I'm getting around 3 psi from a 70mm diameter impeller, it's 3D printed and spinning at 60,000rpm. I'm almost ready to test out a two stage compressor with 80mm impellers, just waiting for a power source. The whole thing is now 6" diameter which is far too big, so I want to upgrade the speed to 150,000 rpm so I can get the whole thing to around 3" diameter. I will probably knock something up of the 3D printer, if it works then I'll go to metal, of course I won't take it up to full speed in plastic. I imagine the Kawasaki super charger must have some kind of a lubrication system, this will be the difficult part.

Thanks, I will keep you updated of whether it works out, having fun with the 3D printer anyway. I'll post some pictures or a vid when I get it working properly, sounds like a jumbo jet at the moment, not sure I'm brave enough to put it in my car.

Edited By Joe Page on 18/10/2017 21:18:54

[Neil WyattModerator @neilwyatt]

If you can find out how the kwaki does it, you will be sorted. Don't forget the outer gear is the slow one and the planet gears are fixed (I think) so all the nasty loads are on the central pinion BUT the tooth loads are divided by three.

One of these eh?

[duncan webster 1Participant @duncanwebster1]

Posted by Neil Wyatt on 18/10/2017 21:38:20:

If you can find out how the kwaki does it, you will be sorted. Don't forget the outer gear is the slow one and the planet gears are fixed (I think) so all the nasty loads are on the central pinion BUT the tooth loads are divided by three.

One of these eh?

 

If going planetary you need to make something float (radially), otherwise you don't get load sharing. You can also fix the annulus and drive the planet carrier, but it might be easier to drive the annulus for 3:1, otherwise the planets could be a bit small.

If you're running a 3D printed impeller at 150,000 rpm let me know and I'll keep well away from your part of the country on that day. Make sure you spin test it surrounded by sand bags. If it breaks up it will be spectacular. Why not pinch the impeller out of a turbocharger?

Edited By duncan webster on 18/10/2017 22:14:20

[MuzzerParticipant @muzzer]

Search for "electric supercharger" and you will see what the automotive companies are doing. Driving a compressor through a gearbox will be fraught, even if you don't manage to kill yourself in the process.

Be wary of the ebay "electric superchargers" that are little more than a hairdrier and can't possibly be capable of developing any kind of boost pressure at the flow rates required. If you plan to develop such a device, you should do the sums and calculate the shaft power required to compress the mass flow rate to the pressure you expect. It will be quite large…

Murray

Sorry to sound negative. I work in turbochargers and was seeing electric superchargers in development 10 years ago. Quite simply you don't stand a hope in hell but that shouldn't stop you.

Edited By Muzzer on 18/10/2017 22:44:06

[Joe PageParticipant @joepage27051]

Just tested my 3D printed prototype, everything plastic apart from the drive shaft. Got it to around 50,000 rpm at 5psi, quite amazing when the impeller is 86mm in diameter, it is printed from polycarbonate however, just got to do a little rework on the design, then if it works I've got to completely re-print it from a higher temperature plastic (main housing is PETG) before I can give it a test in a car, hoping for around 8psi. I will scrap this design eventually and work on the gearing idea.

Posted by Joe Page on 18/10/2017 21:06:00:

I will probably knock something up of the 3D printer, if it works then I'll go to metal, of course I won't take it up to full speed in plastic.

Posted by duncan webster on 18/10/2017 22:13:53:

If you're running a 3D printed impeller at 150,000 rpm let me know and I'll keep well away from your part of the country on that day. Make sure you spin test it surrounded by sand bags. If it breaks up it will be spectacular. Why not pinch the impeller out of a turbocharger?

Hi, Duncan, I will be scavenging a compressor wheel from a turbo, spinning plastic at the speed I'm at now is scary enough, plus they're a lot less efficient compared to a turbo wheel.

Posted by Joe Page on 18/10/2017 21:06:00:

I'm trying to make it a compact modular system so that they can be paralleled up for more power, considering it takes about 10kW of power to boost a car from 140, to around 200bhp is probably a reason they're not produced, a project never the less.

So far I'm getting around 3 psi from a 70mm diameter impeller, it's 3D printed and spinning at 60,000rpm. I'm almost ready to test out a two stage compressor with 80mm impellers, just waiting for a power source.

Posted by Muzzer on 18/10/2017 22:18:48:

Search for "electric supercharger" and you will see what the automotive companies are doing. Driving a compressor through a gearbox will be fraught, even if you don't manage to kill yourself in the process.

Be wary of the ebay "electric superchargers" that are little more than a hairdrier and can't possibly be capable of developing any kind of boost pressure at the flow rates required. If you plan to develop such a device, you should do the sums and calculate the shaft power required to compress the mass flow rate to the pressure you expect. It will be quite large…

Murray

Sorry to sound negative. I work in turbochargers and was seeing electric superchargers in development 10 years ago. Quite simply you don't stand a hope in hell but that shouldn't stop you.

Edited By Muzzer on 18/10/2017 22:44:06

Hi, Murry, should have probably read my post, I'm not making a simple 20W fan motor like those on ebay, it is actually the reason I started the project, to prove much more power is required and that the ebay units are complete junk, I'm using a 4kW system for now that will be modular for multiple units, I did state it takes about 10kW of power to boost a 140bhp car to 200bhp, that's assuming 100% efficiency. I don't understand why you don't see it's possible, the supercharger that Neil showed us from the H2R is exactly what I'm building, the difference is one is mechanical power and mine electric.

What I would agree is they're not practical since the electric system on a car is not designed for 4kW of power, let alone 10kW or more.

[Danny M2ZParticipant @dannym2z]

Posted by Neil Wyatt on 18/10/2017 21:38:20:

One of these eh?

I had one of these when I was younger. XB Falcon, a great Aussie car for 1975.

When I purchased a Holley 250 twin carb for it a wise mechanic friend refused to tune it until a larger (free breathing) exhaust system was fitted. To quote "Danny, first thing to consider is how to get rid of all the extra burnt stuff"

So a custom dual exhaust, complete with extractors was fitted. Each pipe ended up with twin 'Hot Dog' mufflers so it was a quiet burble when idling/cruising but gave a throaty roar when cranking.

Next thing was that the transmission, brakes and suspension had to be upgraded to handle the extra power and stop the beast. With the cost of a new set of Pirelli's the original price was skyrocketing (fitted a racing harness seatbelt system and upgraded the sound system too).

The front end (steering) got a bit light at about 200Kph so a new air dam and revised rear spoiler were next on the list.

Fortunately, I got married and very smart wife persuaded me to sell it, mainly because it drank fuel like a 747 and when she took it shopping all the other hoons wanted to race her from the lights. Possibly why I am still around

If I were to make such a (mid-life-crisis) toy today then something like this looks interesting **LINK**

* Danny M *

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