Saturday, October 6, 2007

Thoughts at the End of the Day

Well, the car is all back together again. I really can't say it's any better than before; however, I've learned a tremendous amount in the process. After balancing the flywheel twice, adding rubber grommets, replacing the transmission mounts and putting in a new pilot bearing in, I still can't get the vibrations to go away or diminish much.

Given that the second transmission didn't vibrate much at all, even over 7000 RPM, I'm really suspecting the existing transmission has a bent shaft in it or something. There's definitely 10 mils of runout on the input shaft, but I didn't think that would be a big deal. If I look back over my transmission rebuild at the link here, I remember that the bearings in the transmission were shattered. I never really understood why and just replaced the bearings. Perhaps one or both of the shafts were bent already and caused the bearings to break. I'm also guessing that running the transmission through its natural resonant frequency several times over the past week wasn't good for it either. I might be able to salvage a straighter shaft from the second transmission, but I don't know if they are different between the side-shifter and the tail shifter version. The next step is to drive around a bit more and see what happens. Perhaps the transmission will fail, but who knows.

Since the RPM gauge and indicator lights are working, I'm thinking about driving the fuel gauge with an opto-isolated circuit from the 144V pack. It needs opto-isolation so that there are no connections between the 144V system and the 12V system. I'll post that circuit if and when I get it working. Best wishes to all the other EV folks working hard out there to get their cars running.


Roger Daisley said...

Tim: I know you don't want to hear this, but I really think you should take your tranny to a good VW/Porsche garage and have it totally rebuilt. (You can use the donated tranny as parts.)

It seems obvious to me (I'm a mechanic, not an electronics tech) that ypu have some bad bearing in your tranny. Replacing the pilot bearing (if it's anything like a normal transmission pilot bearing) will probably not fix much. It's basically non-functional except when the clutch is activated. All the rest of the time it's simply not being used. I don't think a worn pilot bearing is the source of your problem.

Probably someplace in the innerds of your tranny there is/are several bad bearings. If the main shaft bearings are bad, you will get vibrations which would otherwise be masked by the ICE engine. The proof seem obvious: The borrowed/gifted tranny did not vibrate. Viola: Old tranny BAD - New Tranny GOOD.

You've got a lot of cash tied up in your conversion ... don't cripple it by limiting your RPM's so as to prevent vibrations.

Just my humble opinion.


TimK said...

Hi Roger,

deep down, I know you're absolutely right about this. I replaced the tranny bearings already, but they might be shattered again due to bent shafts, etc... Also, after all my experiments, the transmission is making much more noise, possibly due to me taking it through resonance several times. I've heard there's a transmission place in Bend, Oregon, but they charge $800 just to crack the case. Argh. I guess there's only a fine line between a hobby and insanity. Thanks for the reality check.


Unknown said...

Transmissions on eBay.