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MG MGB Technical - Balancing a flywheel???

Hello all,

This question actually pertains to my Reliant Regal, not one of my MGs, but I thought someone could help.

I recently pulled the engine and gearbox, had the flywheel resurfaced, and replaced the clutch. I should note that while doing it, that machine shop had to drill out the locating dowels (should have screwed them out). That left me with slightly oversized locating dowel holes, which I then tapped, screwed a bolt into, cut down in situ so that the bolt shank became the new locating dowel, and then enlarged the holes in the clutch cover to match.

Car runs well, but there is a significant vibration as the revs increase both while the car is stationary and moving (which rules out the driveshaft). Nothing is touching anything on the chassis (I've been under there while it was on a lift with my wife revving the car).

It seems to possibly be from the tranny area, so it implies that perhaps the flywheel had come loose or something like that.

Engine and gearbox out again, and nothing looks awry.

Several Reliant guys-and I am inclined to agree-think the flywheel might be out of balance and suggested balancing it along with the new clutch cover.

Does anyone know where to get a flywheel/clutch balanced?

I am in Tennessee, and so far every machine shop cannot do it or can only do a flywheel with a hole in the center that is at least 1-1.5" large.

As the clutch used on a Regal is the same as a AH Sprite and MG midget, it stands to reason that the flywheel is a similar size.

Hence my posting....hoping someone else had done this on their flywheel.

Thanks,

Julian
Julian Dufour

Julian,
you could also post a thread in the Midget & Sprite section as there are some USA members there, failing that you could try MGA and T Series TD-TF sections.

Or perhaps you will get the answer you need from here.
Nigel Atkins

Julian. I would think that you are correct in your belief that the clutch and flywheel are out of balance. At the very least, some part of the rotating mass is out of balance.

Since I am not familiar with the particular automobile you have, and have a rather large collection of books on various automobiles, it would be safe to assume that most machine shops will not be familiar with it either. So, my first question would be, Did you notify the machine shop resurfacing the flywheel that the locating dowels were threaded in as opposed to the more common drive fit dowels? It would seem that the root cause of your problem stems from the fact that the previous locating pins were drilled out, then you had to tap the holes, thread in new locating pins (drill rod? grade 8 bolts?) and cut them off to some length suitable for locating purposes, then, drill the locating pin holes in the clutch plate larger. So, exact placement of the newly threaded holes, exactly the same length on each of the locating pins (along with the exact same taper to make the clutch plate fit on more easily), then a perfect drilling of identical sized holes on the clutch plate to fit your new locating dowels. I would have been very surprised if the system did not need to be rebalanced.

The way my engines have been balanced in the past, is by balancing the crankshaft first. Then, the flywheel is added to the already balanced crankshaft and the system is rebalanced. The crankshaft pulley/harmonic balancer may be balanced with the original crankshaft balancing or installed and balanced after the flywheel is balanced. I have heard arguments for both methods. Lastly, the clutch place is installed on the flywheel and the entire assembly again balanced. This is time consuming (hence, expensive), but produces the best possible system balance and the one which will require the minimum rebalancing adjustments over the lifetime of the engine and components.

This may be what you will have to have done to correct the problem you perceive. As to where to have the work done if you cannot find someone in your area, that might be as simple as making one telephone call to John Twist (his phone number and best call time are on his University Motors, Ltd website). John's website has a number of referrals for various firms that do MG work. One, or more, of them should be able to recommend a good automotive machine shop, some may offer such services themselves. If you cannot find the information within John's resource list, a call to him would be in order and he should be able to advise you.

Les
Les Bengtson

Les and all,

Thanks for the insight.

I have decided to get another flywheel from the UK (since there are almost no Regals over here!).

I am fairly confident that will solve the problem so that I can move on.

Will let you all know if it works once that happens.

Cheers,
Julian
Julian Dufour

Hi Julian, over here many Reliant 3-wheelers were made but they have always been regarded as a bit of a joke. Their principal reason for existence was the strange law that allowed someone with only a motor-cycle licence to drive one, as it was classed as a tricycle, the same as a motor-cycle with sidecar. This meant the owner didn't need to bother with passing a driving test in a car. The 3-wheelers also attracted a lower vehicle licence duty that a normal car.

I bought a 1955 Regal while still at school. I passed my motor-cycle test in 1965, which was a really simple test in those days. Then I got the Regal. Mine was an aluminium body convertible with the old pre-war Austin 7 side valve engine and a no-synchromesh gearbox. That taught me to drive properly. It was simplicity to get it up on 2 wheels when cornering - exciting but not very sensible, but then who is sensible at 17?

Here's a picture of it with schoolboy me inside. A less regal vehicle would be hard to imagine!



Mike Howlett

Julian, I wouldn't have thought that the flywheel would have been rendered sufficiently out of balance by the actions of drilling out, larger holes etc. I guess you could static balance the whole assembly rigging up something similar to what they use to balance lawnmower blades, but on a larger scale.

Dynamic balancing is very specialised and tuning shops would know where to buy it in. Not many regular machine shops have that facility.

Have you ruled out a slightly bent gearbox mainshaft?

Echoing Mike's thoughts on three-wheelers, I went down a similar route, but initially with an BMW Isetta bubble car, and then a couple of Messerschmitt KR200s. I failed my initial car test and booked in for another. My contingency plan if I failed that was a Berkeley T60 which I was very much taken with (all these vehicles were cheaply available locally). As it happened, I passed and for some reason a couple of weeks after passing the test my ancient VW Beetle comprehensively failed its MOT. For some reason I bought an Mercedes Benz 180 to replace it. The opposite way around to many of my age I got my fascination for German vehicles out of the way in the early part of my motoring career.
Peter Allen

Mike,
fabulous photo and story but you make that car look big, surely rationing had finished by the mid-60s. 🙂
Nigel Atkins

To answer Nigel. Rationing had of course ended by then, but you discount the effect of mother's rationing, and the fact that we never had excess money. Sweet things were very well controlled in our household! The car seat was such that I basically sat on the floor, and secondly I was a skinny little teenager of only average height. I'm still average height and not that much broader than I was then, I'm pleased to say.
Mike Howlett

Julian
a possible fix would be to discard the mislocated dowels and accurately mark out and redrill the flywheel for new dowels in a different location around the flywheel---maybe back to the machine shop and get them to spin it up and mark an accurate circle on the face for you to divide up and mark out for the new holes
If it has a machined hole in the middle of the flywheel it could be balanced on a motorcycle wheel balancer---they're quite sensitive and accurate, I'd check the flywheel first which shouldn't be out at all much unless they've stuffed up machining it, then bolt the p/plate on and balance that
William Revit

O/T

Mike,
good to hear you are still trim (wish I was) but you must have had excess money as you had a car. My head would have been even nearer the steering wheel.

I've only just noticed the high level indicators, and overtaking mirror, fabulous. Thanks for posting the photo.
Nigel Atkins

This thread was discussed between 08/02/2022 and 12/02/2022

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