Just a quick note - been trying to remove a vibration from a 4.6ltr RV8 for about a year. Bellhousing was touching tranny tunnel at one point so that's enough to cause it (hacksaw solution there...) Main point, a brand new matched and balanced flywheel & coverplate, had in fact been balanced so badly it needed a 2oz weight near the edge to make it balance level on a spike!
I was quoted £50 to get it balanced commercially so sod that - used spike, spirit level & hand drill... turned out fairly easy!
So you can't always trust new components to be right. Cost me a small fortune that little error!
Bob

Glad it's sorted now.
Is this in your V8 MX5? She must be kicking out some serious horsepower now

got it dyno'd a while ago, 210 ggs with 220ftlbs from 1000 to 5000 revs. Should be good for about 60 more than this, but I reckon its the lousy offenhauser inlet manifold holding it back. When the locost is done with yam R1 engine the power/weight will be 50% better (probably more!) with just 1litre - should be a laff! The mazda is a hell of a laff already! It's surprisingly well behaved actually - the mx5 has an excellent chassis & the V8 significantly lowers the CofG - and weighs the same as the iron block 1.6 I took out! BTW I put the engine on my bathroom scales with flywheel but no alternator or carb - 130kgs I think the starter motor was on as well.
cheers
Bob C

Is it smooth now with your diy balancing? Static balance will be good but dynamic "may" not be. Still cheaper to try it though! I would have thought it would be ok!

Smooth as silk! OK removing the "touching" point (starter motor bump on bell housing) probably bigger effect than the balancing, but glad I did it anyway.
regarding "dynamic" balancing - you can look at this as seperately balancing each end of a long thing - the flywheel is inherently just a disc so static is all you need.
Brings up an interesting thought - back wheels on a truck axle (or dedion) only need static balancing . . . discuss...
Cheers & beers
Bob C

Bob, I'm not arguing because practice is always best, and if it works then do it etc etc (that's the way i like to do things) but when the flywheel is bolted to the crank, it becomes a "long thin thing" effectively one piece from crank pulley/damper all the way to the flywheel. This is why this lot is usually all balanced together. Likewise IN THEORY (but often not in practice due to dragging brakes etc) wheels are better balanced on the car as they are then a unit with the halfshafts etc. (downside is if you account for other imbalances with wheel weights then swap the wheels about!!)

The de-dion would certainly be no different to a front wheel as the driveshafts are flexibly coupled to the wheels.

Anyhow, might try your technique with my flywheel after I have lightened it, as you say, for a flywheel on it's own it should work fine!

Yeah, quite right, in general the "factory" RV8 crank & flywheel are balanced together. However I bought mine in bits so I relied on each bit being individually balanced. It's a lightened flywheel - 24lbs from memory (bit less now).
My theory is: front wheel dynamic imbalance is trying to shake the steering wheel so VERY noticable - I was suggesting that back wheel dynamic imbalance doesn't have direct feedback to the driver - it's just trying to twist some bearings! Static imbalance would make the back end vibrate...
I turned up a wee cap thing on me lathe so the spike sits bang in the middle of the flywheel - what a cool thing that lathe is, £300 in loot and it's got a calibration ccertificate! Never seen one of them for a lathe before!
Bob C

I'll give that a go! (Got my lathe for £100, Colchester Master 6 1/2 ", gap bed, 40" bed, converted to single phase, haven't got a cal certificate though and don't think it would get one either, it's a bit worn!!!)

Only playing!! Will try the balancing though, as you say, for a flywheel should be much better than nothing!!

Monster! i've only got 4.5" swing (missus)
Bob

Probably better with 4.5" than a worn out 6.5"!!! ooh err missus!! Better stop this before somebody gets the wrong ideas!!!

Once had a badly out of balance flywheel on an Imp engine -- original got damage ring gear mid season rebuild so another was put on one event unltil a new ring was obtained. It shook the big end bolts loose in 5 laps --- at 9,000 rpm + this was no joke.

Re static balancing of wheels if done with common sense I always found this OK except on the front of cars with strut suspension . Years back whheel balance machine wouldn't take very wide 13" dia wheels so I built a static balance out of a olds taper roller bearing stub axle and hub with all grease cleaned out the hub and lubed with WD40 to reduce drag -- quick spin and heaviest part stops at the bottom -- accurate to about 1/4 oz

[Edited on 12/5/04 by britishtrident]