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Old 04-09-2007, 08:35 AM   #1
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Flywheels (what is the biggest automotive / truck / lorry one you know of?)

I'm just doing a few calculations, involving flywheels, and I'm trying to find out what kind of flywheels are available. I'm just considering the feasibility of a flywheel energy storage system for use in a car (electrical energy storage).

Flywheel explosions can be devastating, which is why I'm interested in automotive ones - they are tried and tested, and good for 4000-9000rpm depending on which type you use .

The best I've found so far is:

S13 Nissan 200SX ----- 13kg flywheel ----- 30cm diameter (15cm radius) = 12"/6" ----- rated to 7200rpm (8500rpm appears no problem with engine mods).

What I'm really interested in, is whether you can get flywheels with a larger diameter, and what speed the engine they came from is rated at?. The mass of the flywheel isn't particularly important, what is more important is that there is a lot of mass on the outer edge of the flywheel .

So, does anyone here know of the specs for flywheels for large engines e.g. gas-powered truck engines?. I would be grateful for any details to see if my ideas can be made to work
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Old 04-09-2007, 08:59 AM   #2
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Quote:
Originally Posted by landspeed View Post
...they are tried and tested, and good for 4000-9000rpm depending on which type you use...
Keep in mind that they are tested for their specific application. Vibration failure will be a result of any more things other than the flywheel itself (interactions between the FW - crank - even crank pulley etc.). This is especially true when you have a high MoI (Moment of Inertia) from most of your mass on your outside edge. I'm not trying to scare you -- just making sure you're aware
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Old 04-09-2007, 09:55 AM   #3
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I hadn't thought of that in particular - but I'm still confident, mainly because, the setting I would be using it in will be less harsh than the original setting - originally, they go up to very high rpm e.g. 8500, have a (imperfectly balanced) clutch pressing against them, and have coriolis type effects when the car is cornering. In my idea, they would be in a clean, self-contained vessel, again rotating at their rated speeds, but without the clutch being there.

Containment would of course be an issue - the containing vessel would be strong enough to contain any failure, and will be particularly reinforced so that no shrapnel could enter the cabin. There have been prototypes for automotive flywheels rotating at 100,000 rpm, which (in combinations of 16 flywheels) could give a 300 mile range (in an EV1), and which could be charged up again in a few minutes if there was a suitable filling station.

As I don't have access to flywheels operating at these speeds (and the 1.5 million-G forces at the outer edge), I think that a very useful increase in MPGs could be achieved by using a flywheel with a lot less energy contained in it.

the ideal flywheel, as far as I am concerned, would be 20-40cm radius (40-80cm diameter), weight 15-50kg, and would be rated to at least 4000rpm, and would be from an engine of some sort. Does anyone know of anything suitable?
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Old 04-09-2007, 11:20 AM   #4
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So you have done the calculations and think that a flywheel that size and weight would store enough energy to be worth the hassle?

What I keep thinking is that larger flywheels typically are associated with lower rpm engines. Maybe some large road-going diesels have the combination of rpm and revs you are looking for...
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Old 04-09-2007, 11:35 AM   #5
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I was doing google searches but couldn't find the specs for any of the engines I was looking for. I was thinking of gas-powered trucks, because gas engines run faster than diesel engines.

I'm thinking that a flywheel could be a brilliant tool for prolonging engine-off-coasting, and when in town, having made a spreadsheet to
calculate the energy stored in the flywheel based on rotational speed, mass, radius.

The main reason why, being that flywheels can be charged and discharged at will. Meaning you could stop at lights using regen braking, then accelerate using the energy stored (or, use the engine to get up to speed, and use the energy in the flywheel to coast for ages with the engine off).

Or... when driving in the countryside, if you come across a hill where the car goes above 35/40mph, you could store the extra energy into the flywheel (rather than going to 60mph and wasting loads of energy to wind resistance). Once the flywheel is full you could then let the car speed up, but then use the stored energy to go back up the other side at a constant 30mph. Thereby avoiding a lot of wind-resistance related energy loss.

Another use would be to accelerate from 20-50mph at 0.5-0.75 throttle, while charging the flywheel (using the engine in the most efficient way), then coast for a lot longer using the energy in the flywheel!.

This would all be noting that energy efficiency can be 91% in electric motor/generators.
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Old 04-11-2007, 05:14 PM   #6
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did you think about the whole housing? there isnt much clearance in car engine housings. then you got the whole starter issue. if it will even be able to turn such a thing fast enough for the engine to kick over, without getting burnned out every couple of months. kinda defeats the whole savings idea.
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Old 04-11-2007, 06:05 PM   #7
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Prehaps something from a V10 truck or diesel?
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Old 04-11-2007, 06:12 PM   #8
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landspeed -

Here is some related stuff that you may have already found :

?Extreme? Plug-In Flywheel Hybrid Promises a Possible 250 MPG
23 February 2005
http://www.greencarcongress.com/2005...xtremerdq.html
Attachment 368
Quote:
AFS Trinity?s approach is to use a flywheel within a flywheel. Its ARC (Active Rotating Containment) flywheel?for which it received a patent in 2002?uses a slower, heavier rotating outer flywheel to contain a much faster, lighter inner flywheel.

Now, here is AFS Trinity :
http://www.afstrinity.com/
Attachment 366

The car design that you see above is maybe 20 years old. I saw this car in the 1980's at the LA car show in the alternative car section. I know it is the same because I remember the "old fashioned" Pre-Infiniti G20 design of the butt :

Attachment 367
I think it has aged well!

Their old flywheel design, which didn't pan out, was to have maybe 20 "1 Gallon" Paint Can sized flywheels in the trunk, continuously spinning (this was the pre-hybrid drivetrain era, so the flywheels were being used as batteries for a zero-emission vehicle). They solved the flywheel explosion issue by switching from metal flywheels to some kind of heavy fiberglass-polycarbonate design. When the flywheel "broke", instead of exploding, it would destroy itself within the container by turning itself into "cotton candy" (that's how they described it). When I talked to them way back then, the problem was that the flywheel design wasn't storing enough energy. They said each flywheel had enough power to run a (bread) Toaster, which I just found to be 1100 Watts, or 1.1 KW. Sooooo, it had about 21 KW to work with. From what I can tell in my Japanese magazines, a Japanese Honda Fit with a 1.5S engine generates 81 KW @ 5800 RPM, so the old design would have needed to have 80+ flywheels to match the power of a 1.5 liter Honda Fit .

Here is some more stuff :

Flywheel Hybrid Flywheel? - Can you say CVT?
http://www.halfbakery.com/idea/Flywheel_20Hybrid

Analysis and Control of a Flywheel Hybrid Vehicular Powertrain, by S.Shen, F.E. Veldpaus,
http://www.wtb.tue.nl/yp/default.htm...p/4187~wtbmain

CarloSW2
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Old 04-12-2007, 04:19 AM   #9
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I've found the bottom two - but the top one is interesting I wouldn't mind a couple of those flywheels (the 1.1kw ones). Ten of those would let me maintain about 50mph on the highway!.

I like the idea of a flywheel within a flywheel - so a reasonable amount of energy is stored in the outer one, which rotates slowly enough so that it won't fail, and contains the inner flywheel if it fails.

So far, I've only worked out how to 'safely' store enough energy for my 1300kg car moving at 31mph. Not good for long-range driving, but could be extremely useful in town, e.g.:

- Stop at traffic lights, energy goes into flywheel (about 80% of it)
- Restart engine, use it at 40% efficiency to get to 30mph again
- then drive for around 1 minute, maintaining a speed of 30mph, simply on
the energy in the flywheel .

I do want to create this project, as part of my long-term 'hybrid' conversion plans for my car. I guess I will also have fun doing (underground) destruction testing of a few flywheels too! (Get an oil drum, bury it deep in the ground, , have the flywheel inside this, and drive the flywheel via a long shaft attached to a 10kw motor, and monitor the resonance, rate of energy loss, and so on!. Then speed it up, measuring the RPM, until it fails!. Then see how much damage it did to the containment system!
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Old 04-12-2007, 04:37 AM   #10
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Quote:
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did you think about the whole housing? there isnt much clearance in car engine housings. then you got the whole starter issue. if it will even be able to turn such a thing fast enough for the engine to kick over, without getting burnned out every couple of months. kinda defeats the whole savings idea.
I wouldn't attach it to the engine - the idea is that the flywheel would be powered by a motor-generator, as a temporary energy-storage device. Another motor-generator would then be used to power the car from the energy in the flywheel (or do proper 'regen' braking, as you can charge a flywheel as fast as you like, unlike most batteries).
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