Thoughts on Flywheels

Back in the 70's we had a subscription to Popular Science magazine and there was a lot of interest in alternative energy. I remember reading articles on cars powered by flywheels - you'd plug them in or use a gas motor to spin it up to some outrageous RPM and then drive around until the flywheel stopped spinning. I guess the idea was you'd go to a service station when your tach showed low RPM for a quick respin and then you'd be on your way again...

So what does this have to do with my car? Well, there are two camps on flywheels on electric cars - one camp says they are good and another says they are additional unnecessary weight. I belonged to the second camp but wanted a clutch so was stuck with the flywheel. You might have read some of the early posts where I tried (in vain) to get my flywheel lightened.

Since I've been driving the car regularly, I've changed my mind. In my experience, the flywheel stores your kinetic energy (just as Popular Science described) and helps keep the car stay in motion - reducing the amps needed to maintain a given speed.

The downside is that the flywheel slows your acceleration from a standing start (since it takes a lot of energy to spin up that big heavy disk) and it slows your braking (when in gear, your brakes are not only slowing down the car but the flywheel too).

The plus side is you get to retain your clutch which makes shifting gears easier and you can always use the clutch (or neutral) when braking hard.

Weekend update

Did a couple of little things over the weekend:

1. Busted the ring gear off of the flywheel. It's not needed since there is no starter, and removing it will save a little weight (surprising little, but better than nothing). People say the teeth of the ring gear creates turbulence as it spins, slowing the flywheel down, so, even if it doesn't save a lot of weight, removing it may help a little.
2. Pulled the motor out. I stuck my head out of the garage and spotted an unsuspecting neighbor who was easily talked into risking flattening some of his body parts by helping me lift the motor out by hand (no winch, no cheery picker, just a nylon strap and two he-men).
3. Did some adjusting and fitting of the engine mount. Cut the hole for the bolt head on the top of the ring clamp, added the rubber backing to the ring clamp and tried to assemble it with out much luck. The bolts are too short to bring the two halves of the clamp together and one of the bolt holes does not align. I still need to do a little cutting and welding for my "torque bolt" idea and now I have to "adjust" the bolt hole in the lower clamp and pick up some new longer bolts.

Mystery of the flywheel solved!

There is little that I can do at this point without the connecting up the motor - which requires a flywheel.
I haven't been posting my ongoing attempts to find out the status of my flywheel. Let's just say I have been calling the shop weekly always getting an answering machine regardless of when I call. The machine tells me to expect a return call which never comes. I think the last time I actually heard from the shop owner was back in January...

So today, I finally made it out to the shop to confront the owner and get my flywheel back - even if it hadn't been lightened. After an hour drive I find the shop is closed. The gates were locked, the vehicles in the yard were gone as were the collection of rusty crank shafts.
Looks to me like they went out of business - which would explain the un-returned calls...
So, not only do I not have a lightened flywheel, I don't have ANY flywheel.

I got home and checked craigslist, and, like a gift from the gods of electric cars, there was a flywheel listed for sale.
Sunday, I will be $50 poorer, but will be able to move the project forward.

Drop flywheel off for lightening

The stock Miata flywheel in 19 pounds. An ICE engine needs the flywheel to keep it revolving between power strokes. An electric motor doesn’t need one. So why keep the flywheel? It’s how the clutch is connected – and I want a clutch (some conversions don’t use clutches, but they are difficult to shift). The lighter the flywheel the better the acceleration – racers know this and use expensive ($500 and up) aluminum flywheels. My plan is to have the flywheel lightened. I called a local machine shop and they told me that only one shop in the Bay Area does this stuff. I gave him a call and he quoted me $160 to lighten it. The shop isn’t open on weekends so I arranged to drop it off on my lunch hour.