[MJ Monterey]

Not sure of your base vehicle, are lightened flywheels available for your clutch?

That's kinda middle ground. Less weight still "normal" shifting?

Is automatic an option for you?

MJ

 

[Overlander23]

I'm skeptical of this. Race cars use lightened fly-wheels because it reduces shift times, etc. The weight of the clutch can affect how quickly an amount of power is delivered to a drivetrain (ie. acceleration), but I'm pretty sure your 42 lb flywheel weighs 42 lbs in the end.

You could ask it this way. At what rotational speed does the flywheel weigh seven times more than when its not rotating?

Overall vehicle weight and frictional losses are what accounts for energy consumption or range, not acceleration. You will consume more energy accelerating faster than slower, but you will also attain your target speed faster, so will have accelerated for less overall time.

If you were so inclined to remove the clutch and flywheel you'd save the energy required to move the static weight of the clutch and flywheel. Depending on how heavy your vehicle is, the 50 pounds, or so, in the clutch and flywheel may not affect range by a whole lot. You have to determine whether it's a good tradeoff.

Personally, I like the clutch for all the reasons you do, including safety. If you're OK with the acceleration, I see no reason to get rid of it.

Both my Ev';s have the clutch installed. Was talking to Bryan at evamerica?, and he says I'd get more range by removing the extra weight of having a flywheel and clutch assembly.

 

[Stunt Driver]

I am planning to pull mine out, since I don't use it anyway.

If you were so inclined to remove the clutch and flywheel you'd save the energy required to move the static weight of the clutch and flywheel.

Sorry, you are wrong.


Next time when you'll be on service with your car up on the lift - try to spin your tire wtih your hands as fast as you can (hardly 1000 rpm). Then ask someone to stop it by brakes. Then spin it up a few times again.

While static weight doesn't move anywhere - do you feel exausted?


Energy of rorating body is proportional to square of angular velocity. http://en.wikipedia.org/wiki/Kinetic_energy

 

[Overlander23]

I'm unsure what this proves? I'm not claiming that weight doesn't affect acceleration. I'm claiming that weight is weight. Equal amounts of weight require the same amount of energy to move a given distance. Just because some of that weight is spinning doesn't mean anything for overall consumption.

In the case of the flywheel... it acts like a battery, storing energy within its mass. As the flywheel spins down it releases that energy. In most driving cases, the flywheel will spin down as the car comes to a stop adding to momentum gained by the car moving. The net loss is zero (barring frictional losses, etc.)

If you were to accelerate the flywheel up to speed and then depress the clutch... allowing the clutch to slow on its own, then yes, you'd leach energy away uselessly (from the friction slowing the flywheel). But that's not how one typically drives.

With your example, let's assume a zero friction scenario (impossible, but let's get irrelevant variables out of the way.) Spin the wheel with no flywheel connected and bring it up to a constant speed. Now do the same with the flywheel connected. At the same constant speed, the wheel will require the same amount of force to move it (actually in a zero friction situation this would be zero force to maintain rotation at a constant speed.)

The amount of energy required to spin each setup to speed will be different, more being required for the flywheel system. But the flywheel system will also return that energy when it stops.

Take the clutch/flywheel to an extreme. Say you have a 1000lb flywheel on your car. It will take a huge amount of energy to accelerate the flywheel (and thus the car), but when you stop accelerating, the car will coast forever. Not just because it's a 1000lb flywheel, but because of the stored energy within the flywheel. Same thing works for a light flywheel but high rpm. A light flywheel spinning a million RPM will store quite a bit of potential energy.

Next time when you'll be on service with your car up on the lift - try to spin your tire wtih your hands as fast as you can (hardly 1000 rpm). Then ask someone to stop it by brakes. Then spin it up a few times again.

 

[DONEAL]

F16bmathis
Not sure what you mean?
>I don't have to wait for the motor to spin down to match my next gear.<
For a ICE, yes, you have to time your shifts, but on my EV, there is no motor spin down, I just shift( I don’t have a clutch) and there is no grinding, no nothing. It goes in gear with ease.
About >So would I get so much more range< I’ve read several post about rotational weight and I would be inclined to think that it would.

 

[Guest]

I doubt you'd have any noticeable difference in range without the clutch vs with the clutch. If you were racing I'd still say keep it because you may just need to get that one extra gear and you'd want that clutch for that. Only if you don't have a transmission would you go clutchless. Keep the clutch. It can't hurt and you already have it in. Go clutchless and you must do some changing on how you connect your motor. Just leave well enough alone. You made a fine choice to keep the clutch.

Pete

 

[automd]

F16bmathis
Not sure what you mean?
>I don't have to wait for the motor to spin down to match my next gear.<
For a ICE, yes, you have to time your shifts, but on my EV, there is no motor spin down, I just shift( I don’t have a clutch) and there is no grinding, no nothing. It goes in gear with ease.
About >So would I get so much more range< I’ve read several post about rotational weight and I would be inclined to think that it would.

Hmm.. Based from my friend's experience & based on what you have right now, I guess that you won't have any noticeable difference too.

 

[frk2]

I can confirm there is no noticeable difference with or without the clutch in terms of acceleration or range in my 72v setup though i did heavily shave off my flywheel even with the clutch. However I have been driving clutchless for 2 months and am definitely going to get the clutch put back in since its really bothers me having to wait that 2 or 3 second between shifts. I live in a crowded city and people behind me get really pissed when i start slowing down to make shifts. Also shifting down is a Big issue and i almost always grind gears doing that.

I would also recommend keeping the clutch!

 

[O'Zeeke]

This is from a previous thread where I did the math. There is a gain in range but depends on the weight/rotational mass of your clutch setup, mine was very heavy compared to most. No stats but acceleration "feels" better and as far as increased range, the math tells the story. The 525Wh/mile is actually a little less as no accounting for the charge inefficiency was incorporated
Quote:
Originally Posted by O'Zeeke
I recently removed the clutch/flywheel setup from my 0.0 mustang and went direct for several reasons, not the least of which eliminating 65 pounds of rotating mass (78 lbs with t.o.b., fork) which has made a noticeable difference in acceleration (no stats yet) and I expect some increase in range as well. Not concerned about synchro wear as it will drop right in with a little practice and a lot of the time i just leave it in 3rd anyway. Also someone here has a thread on thrust/lateral load exerted on the rear motor bearing while depressing the clutch and that got me thinking. Just my 0.02$

I'm no mathematician but I did some calculations of the rotational energy used to get the 33kg, .35m dia. flywheel/clutch assembly spinning to 4000 rpm. [wiki=673]Formulas[/wiki] from Wikipedia http://en.wikipedia.org/wiki/Rotational_energy

K(rotational) = 1/2 x (k) x mass(kg) x radius2 x angular velocity(rad/sec)

K = 46274 Joules

My 20 mile commute involves an average of 22 stop lights requiring 22 x 46274 = 1,018,028 Joules or 0.283 KWh.

Charging uses 10.5 KWh (525Wh/mile) so about 2.7 percent of the total charge was used just to get the mass of the flywheel/clutch spinning so for my Mustang this translates into about 0.6 miles for a 20 mile trip (maybe a little more because of the 78 less pounds to haul around). Not a huge increase but in a heavy car I'll take all I can get and its free.

Also interesting is doubling the speed increases the energy requirement by a factor of 4. No guarantee on the math, just my $0.02
__________________
Zero point Zero
http://www.diyelectriccar.com/garage/cars/47

 

[Overlander23]

OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?

I'm no mathematician but I did some calculations of the rotational energy used to get the 33kg, .35m dia. flywheel/clutch assembly spinning to 4000 rpm. [wiki=673]Formulas[/wiki] from Wikipedia http://en.wikipedia.org/wiki/Rotational_energy

K(rotational) = 1/2 x (k) x mass(kg) x radius2 x angular velocity(rad/sec)

K = 46274 Joules

 

[KiwiEV]

The energy savings in clutch vs clutchless are minimal. Any tiny savings would be lost as soon as someone pulls out in front of you and you have to hit the brakes.
I fear the only noticable gain would be from a clutchless EV having reduced weight - to which there are lightened flywheels available anyway, so I admit it's not much of an argument!

Ultimately for most converters the clutch vs clutchless argument comes down to conversion simplicity. Simplicity means saving time, but more importantly saving money on engineering or fabrication.

 

[F16bmathis]

As far as a lightened clutch goes, I could pull it, grind it down, but from all I've read here, and testing driving it without the clutch, there's no way I'm getting rid of the clutch. I had the same effect as the other poster who said it takes too long to shift. I'm running around with huge "ELECTRIC VEHICLE" stickers on the sides and rear to promote EV's, and so getting up and going is a big concern, can't do it fast enough without the clutch. Every day I have someone pull up behind me, obviously read the EV sign, and try to go around as we leave the intersection, and every time, I keep up with the guy in front of me, shifting as fast as I can! Most of my driving is a constant highway speed, so accelerating isn't such a big problem. I suppose if I drove in stop and go traffic, I might consider clutchless.

I'd love to go automatic if I could figure it out. Every application is different, and the wiring diagrams I get from Chevy doesn't help figure out shifting gears. I suppose I can simulate everything, engine rpm's, speed, temperature to the ECM, but I'm pretty darn stupid! But I am watching that thread!

 

[F16bmathis]

I'm going to have to agree with you. Getting a few lbs of metal to rotate doesnt seem like much when compared to getting all the metal you can't get rid of to rotate, plus pushing ALL the weight of the entire vehicle, makes the clutch weight minimal. And if I have a manual tranny, I have to have the speed of shifting with a clutch.

 

[F16bmathis]

OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?

If this is all correct, I used an online calculator and came up with 771 watts, which I can produce on my bike generator in a minute or two, so not really much of a drag on my truck?

I can spin the clutch, motor, all that in nuetral with minimal pedal travel / amps / time, so I'm just guessing it isn't much power used to do it once. Stop and go traffic may be different in doing it multiple times can add up.

 

[green caveman]

Anyone have any advice on machining down the flywheel? I'm about at that stage with the Sidekick and it seems that you can loose a bunch of weight, rotating or otherwise.

Maybe that advice is "just don't bother", but decreasing the rotating mass would seem to be good for a number of reasons, not least that any imbalance should be minimized.

Seems that the advantage would be to take it of the outside - that is, the part furthest from the center. The current flywheel is about 1.25" thick. Since the clutch doesn't get as much of a workout, it would seem that you could easily be able to cut that down, but where's the limit? Would 1/2" be too thin? The center has to stay at about the current thickness to accommodate the pilot bearing so it could be thinned gradually as it goes outwards. I'm thinking it would be good to leave a "rim" on the outside to stiffen the whole plate, but maybe that isn't necessary.

 

[F16bmathis]

I am planning to pull mine out, since I don't use it anyway.





Sorry, you are wrong.


Next time when you'll be on service with your car up on the lift - try to spin your tire wtih your hands as fast as you can (hardly 1000 rpm). Then ask someone to stop it by brakes. Then spin it up a few times again.

While static weight doesn't move anywhere - do you feel exausted?


Energy of rorating body is proportional to square of angular velocity. http://en.wikipedia.org/wiki/Kinetic_energy

Yeah, but I feel exhausted pedalling a bike generator that I can produce a measly 75 watts on (for a short time). I understand what you're saying and found some calulations for it, but some say 10:1, others got as low as 2:1, and when it comes out in the long run, isn't the rotating weight keeping the truck going at that same weight calculation as you slow down?

I wish I had two vehicles I could test side by side!

 

[Overlander23]

Yes!! This is my point. Any energy used to spin the flywheel will be returned to the drivetrain for a net zero energy loss.

Everyone is worried about how much energy it takes to spin the flywheel, but no one is considering that the energy has to go somewhere. It goes back into moving the vehicle.

The "ratios" people are quoting for lightened flywheels refer to the amount of energy needed to spin the flywheel through a transmission, usually through first gear. In this case, 10 lbs off the flywheel is torque multiplied by the first gear ratio. The ratios are always quoted differently because not all transmissions have the same first gear ratio.

The amount of energy needed to spin a flywheel to, say, 4000 rpm changes depending on the mass of the flywheel and its diameter. That's the angular momentum calculations. And due to the laws of conservation of energy, any energy used to spin the flywheel remains in the flywheel. Angular momentum calculations can be used to determine the amount of energy stored in a rotational mass. As the flywheel slows, it gives its stored potential energy up to the drivetrain. The car will "coast" longer.

If people have found that their range is reduced after installing a flywheel and clutch to a formerly direct coupled transmission, it's because full advantage of the flywheel's storage capabilities isn't being taken advantage of. In other words, a longer coast time is being overridden by the frictional application of brakes more than necessary.

The only situations the energy used to spin the flywheel would be wasted would be during the application of friction to convert the flywheel energy to useless heat (braking), or the slowing of the flywheel while it was disengaged from the drivetrain.

For those that think that rotational mass somehow is heavier than static mass, think of it this way. Take a 50 lb flywheel... measure the weight of the car when the flywheel is stationary. Now spin the flywheel to a million rpm. The weight of the car doesn't change! If the weight of the car doesn't change then rotational mass is no different from static mass and range isn't affected. Think of rotational mass as "energy storage" mass.

Yeah, but I feel exhausted pedalling a bike generator that I can produce a measly 75 watts on (for a short time). I understand what you're saying and found some calulations for it, but some say 10:1, others got as low as 2:1, and when it comes out in the long run, isn't the rotating weight keeping the truck going at that same weight calculation as you slow down?

I wish I had two vehicles I could test side by side!

 

[EV-propulsion.com]

Green, I would be careful as to what you are taking off the flywheel-remember thats spinning upwards of 5000 rpm, very ugly if it comes apart.
Also, overlander is correct in that when driving an EV we should be using the long coasting ability to your advantage-I think that's the best way to increase range. Anticipating stops ahead of time (stop signs and such) can save alot of energy. Kind of a learning curve involved in EV driving.......
Mike
EV-propulsion llc

 

[green caveman]

Green, I would be careful as to what you are taking off the flywheel-remember thats spinning upwards of 5000 rpm, very ugly if it comes apart.

Yep, that's why I ask. Nonetheless, there is undoubtedly a bunch of weight there that the ICE needs and the EV doesn't. For example, it seems to me that you could remove the starter motor gear ring without any disadvantage at all.

Also, overlander is correct in that when driving an EV we should be using the long coasting ability to your advantage-I think that's the best way to increase range. Anticipating stops ahead of time (stop signs and such) can save alot of energy. Kind of a learning curve involved in EV driving.......
Mike
EV-propulsion llc

Craig Vinton with his Chevy Tracker claims that machining 12lbs off the flywheel improved his range. If the stored energy is really 700+W, then that's more than a mile of range every time you stop that without recoverying the energy. For a 3000lb car moving at 30mph that's about 25% of the kinetic energy of the car stored in the flywheel - a significant chunk, but as you say, that only comes into play when you stop it with the brakes.

Since we have a Sepex/Regen system, it should be possible to recover energy from the 5000 RPM hunk of very heavy steel even on a quick stop - so long as you remember to push out the clutch.

I still tend to think that some amount of material can reasonably, and cost effectively, be removed from the flywheel without any danger to the structure and that it would be an advantage to do that.