Good News Everyone!

Well I bolted the flywheel up to the motor and spun it up. What a difference! The wobble was almost entirely gone. There is still a small vibration at around 500 rpm while the motor spins up, but when the RPM's climb just a little higher and beyond, it is as smooth as glass.

Now I just need to get the pressure plate mounted back up and start re-assembling the drive train. Mounting the pressure plate is going to be tricky as it is naturally sprung to push on the clutch disk, meaning I have to collapse it about 1/2" to get it on. When it's new it has a retaining system that holds it until you bolt it up, making it easy to get it on the flywheel. Well, that's gone so this could be tough.

A Slightly Lighter Flywheel

I got the flywheel back this afternoon and it had about 6 grams of material drilled out of the side.


The machine shop was able to get it down to only 0.2 grams out of balance. That's like a smear of grease. Anyway, no time to hook it up this evening. I'll put it on tomorrow and report back as to how stable the assembly is.

The Flywheel is at the Shop

That sounds like a pass code phrase you'd hear in a bad spy movie. Anyway, the flywheel is in the shop, and they are going to put it on the machine in the next couple days, to test it and balance it.

While I was there the machinist said something that's got me a bit worried. He looked at the flywheel and said that he'd be surprised if it was out of balance because it was a "zero balance" flywheel. He asked what it's bolted to. I explained how the taper-lock hub mounts to the motor and the flywheel to the hub. He asked if there was any chance the hub was out of balance.

The truth is I have no idea if the hub is in balance. I mentioned yesterday that the motor did vibrate a bit once I'd removed the flywheel. Could that have been caused by the hub being out of balance? I just don't know. There was definitely an improvement in balance when I removed the flywheel. That stands to reason that it was part of the problem.

Let's suppose the hub is out of balance. The question becomes would the flywheel being bolted to the assembly exacerbate the small wobble I saw once the flywheel was removed? It stands to reason that if that were the case, having the clutch plate and disk bolted to the assembly would make it even worse. That's not what I saw. There was no appreciable change in wobble between having the clutch plate mounted and not.

If they find the flywheel is balanced and the problem becomes the taper-lock hub, I'm not quite sure what I need to do to get it fixed.

UPDATE: The shop just called to tell me that the flywheel was indeed out of balance. 6 grams to be precise. I should have it back this afternoon and I can mount it up and see what we get. Stay tuned.

Motor Pull

Funny, you usually see an entry in and EV blog called "Motor Pull" as one of the first entries. Certainly not one after the proud builder has put only 901 miles on the completed car!

OK, enough grousing. Here's the, once again, empty engine bay.

My dad was kind enough to come over and help me get the motor out of the engine bay. It was quick work. I had everything disconnected by 10:30 and we had the motor out 1/2 hour later.

The first order of business was to start testing. We pulled the transmission off of the adaptor plate to expose the clutch and flywheel. I secured the motor and we spun it up. Sure enough, there was the wobble. It took a while for the 12 volt battery to spin it fast enough to see the wobble, but it got us there.

Next, we took off the pressure plate. So only the fly wheel was mounted to the hub. We spun it up again and... wobble. OK, so now we can check off the pressure plate and clutch disk as the cause. Next we removed the flywheel, leaving only the motor and the hub.


We put the battery on it again and watched carefully. There was still a bit of wobble, but it was substantially less. Perhaps 85 to 90% of the wobble was gone with the flywheel off. So, here's the culprit:


I was kind of surprised to see that there was some wobble with the flywheel off. I did what George from Netgain suggested. I spun it up and looked straight down in the hub. There was no sign of movement at all. I held a piece of aluminum right next to the side of the hub as it spun to see if it rubbed periodically or consistently. There is no variation in the spin at all. Perhaps the slight wobble that we see is from a slight imbalance in the motor. All I know is that it is very minor and there is absolutely no play in the shaft or bearings, so I'm not going to worry about it.

Next I need to get that flywheel down to a shop that can balance it.

Transmission Arrives

Well, the transmission arrived today, as I'd hoped it would. It was in good condition with one minor exception, a guide plate that's bolted to it used for two hoses was bent. A couple careful whacks with a rubber mallet and it's good as new.

In the mean time, I needed to torque down the flywheel and attach the clutch and pressure plate. Realizing I needed to lock the flywheel in place, I started looking around for some way to do it. I ended up using a leftover piece of channel iron, a long bolt and a C clamp to hold the bolt down.

I realize this means I'm dangerously close to achieving the status of "redneck", but BMW wanted crazy money for the "official" tool. Anyway, here's a good picture of the whole assembly.



Next, I have to get some replacement hardware to bolt the tranny up to the motor assembly.

Adaptor Plate Mounted

This morning I attached the adaptor plate, taper-lock hub and flywheel to the electric motor. The tricky part was making sure that the distance from the friction surface on the new flywheel to the back of the adaptor plate was exactly the same as the distance from the back of the engine and the original flywheel. I took my time, was very careful, and got it right the first time. Believe me, I wasn't looking forward to the prospect of tying to get that taper-lock hub apart if I messed up.

Here's a shot of the beautiful WarP 11 motor. With the voltage I'm putting to it, it should develop approximately 220 ft/lbs of torque at 0 RPM. I'm going to have secure this to frame very well.

Next I mounted the adaptor ring, adaptor plate, and taper-lock hub. This required the most care, but really wasn't that bad.

Last, the flywheel goes on. What a stunner. 11 lbs. of sexiness, that's what that is!

Hopefully, the transmission arrives today. I need to get the hardware to mount it up to the motor, but once I get that taken car of, then the whole assembly goes into the car.