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Crank & flywheel balancing.

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Mikelead Mike Leadbeater
York, Yorks, UK   GBR
1953 MG TD
Can you give me some words of wisdom regarding crankshaft and flywheel balancing.

There is no evidence of balancing marks on the crank or flywheel, so assume factory standards were not very high.

I am rebuilding my TD engine, having had it rebored and reground, the machine shop in the UK wants £60/80 plus 20% vat to balance the crank without / with the flywheel.
Dos this seem a reasonable amount for this ?

I do not need a high revving racing engine, just for normal road use.

I have mounted the crank in my wood lathe, with and without the flywheel, between revolving centres, and note a tendency for the shaft to settle back slightly after gently revolving, suggesting that there's some degree of out of balance.

I'm inclined to have it balanced, and was wondering if the clutch cover should be added to the assembly, also I need to replace the ring gear, so will do this before balancing.

I guess it's pointless including the clutch plate as well as the rest position will always vary as the car is driven.

Your comments would be welcome, thanks

Mike

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plus4moggie Tom Lange
Bar Harbor, ME, USA   USA
Mike - is it ABSOLUTELY necessary, like new rod bolts? No. Is it advantageous, safer, better for the engine, and make for a smoother-running car - yes. You are quite correct - the factory made only rudimentary efforts towards considering balance; we are able to be much more precise today.

My machine shop does each individual part - crank with pulley bolted on, flywheel, then flywheel with clutch cover to balance and mark the cover (witness marks to show where the cover needs to go after you have taken it off). And yes, you are right to omit the disc.

A complete balance job costs me about $100, down to about a gram or two. (A spec of dust is a half-gram, so I don't worry about that.) That being said, he also also balances the 4 pistons with pins, and the rods - end for end, and total weight, which ought to be a part of the job.

I balance all my engines; it seems like inexpensive insurance, like magnafluxing the crankshaft.

Best, Tom Lange
MGT Repair

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Steve S Avatar
Abingdon West, Southern California, USA   USA
I don't like balancing as a unit with the clutch on, because if you replace the clutch then the whole unit goes out of balance. Better in my opinion to get everything balanced without it, and then have the clutch balanced to match the rest.

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plus4moggie Tom Lange
Bar Harbor, ME, USA   USA
Steve - I agree. What I wrote was crank, flywheel, THEN flywheel and clutch cover together. The flywheel is just a carrier for the clutch cover's balancing.

Tom Lange
MGT Repair.

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Steve S Avatar
Abingdon West, Southern California, USA   USA
Agreed Tom, sorry I was replying directly to Mike's post without realizing you had posted basically the same thing.

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Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
Did they also crack test the crank? When I had mine balanced, it was the crank, flywheel, clutch pressure plate, and front pulley. I also had them lighten the flywheel at the same time. Not particularly expensive, but I don't have an actual cost as several other things were done as well.
Dave H

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Mitchman2 Mitchell Andrus
Mills River, NC, USA   USA
The brand new pressure plate for my TC needed 20 grams to balance. The pressure plate for my E-Type came balanced. When spun it was good to go. So sometimes you need to and should balance, sometimes you don't need to but should anyway.

I have to laugh when someone asks about tuning a carb or adjusting timing to get rid of a shudder at 2,300 rpm. That one my friend might have been baked into the cake.



The Flat Earth Society has members from all corners of the globe.

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Mikelead Mike Leadbeater
York, Yorks, UK   GBR
1953 MG TD
Thanks to all for the advice, I think it will be £100 or so well spent to have a smoother engine, it's the soul of the car.

I did my own crack testing, with a diepen test, fortunately couldn't find any cracks.

Now need to thoroughly inspect other engine components, clean the oil ways, replace the core plugs, gap the rings, as well as polish my chrome-ware, finish rebuilding the tub, strip and sort the chassis, and so on, ......all good fun.

Been restoring old motors for nearly 50 years and still a lot to learn.

Love this forum

Mike

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binky Bill Blick (Disabled)
Disabled Account, Antarctica   ATA
You have a lathe so why not balance it yourself? Same for rods and pistons, you will just need a $30 electronic scale

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  Ctwidle thanked binky for this post
Mikelead Mike Leadbeater
York, Yorks, UK   GBR
1953 MG TD
Bill, cheers
Ordered an electronic scale, 8 quid, so will do rods and Pistons.

I could only attempt to do a static balance on the crank and flywheel, I could make some bearing blocks and have a go, got to be better than it is .

Has anyone made a dynamic balancer?

maybe a load cell and a solid state oscilloscope. I am not much af an electronic bod, any one done this?

Will search YouTube, someone has probably covered this.

Mike

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Ctwidle Chris Twidle
Reesville, Queensland, Australia   AUS
1954 MG TF
Mike, I watched part of the crank balancing for TF 2071 and would have to say that watching it rotate at speed in no way suggested that it was something I wanted to attempt without a dedicated machine!

The static balancing of the reciprocating parts was a much more sedate affair and quite satisfying although the U tube clips make it look more straightforward than I found it with home made equipment.

Chris

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Mikelead Mike Leadbeater
York, Yorks, UK   GBR
1953 MG TD
Chris,

Yes, a fast spinning crank would do a lot of damage. It shouldn't be too hard to fix some backup restrainement, I have had it revolving at 1500 or so, my wood lathe is an old Harrison and is very robust, and I double-clamped the tailstock.

When I was a trainee I balanced electric motor rotors, (nearly 50 years ago...blimey, ) and seem to remember that rotation speed wasn't that high, I guess 200 rpm or so, a sensitive load cell would pick up out of balance forces.

Piezo sensors are very small and sensitive, will see what they cost.
Anyone got any expertise in thus field?

Cheers
Mike



Edited 1 time(s). Last edit at 2019-03-07 05:29 AM by Mikelead.

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Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
No, but having just looked at YouTube following your comments above, I decided it wasn't for me. I have a metal lathe, but its certainly not big enough. Safety is certainly a major factor, but also the additional hardware and software (especially) put me off. At low speed you will certainly pick up major unbalance, but to do the job properly you need to rotate at engine speed.
Dave H

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binky Bill Blick (Disabled)
Disabled Account, Antarctica   ATA
Actually I was not thinking of spinning it in the lathe. Rather, using little magnets of known weight and "letting it fall" as described in first post. A process of elimination. Spinning it will only show visual imbalance.

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TD4834 Avatar
TD4834 Bill Chasser
Sacramento, CA, USA   USA
1950 MG TD
1951 MG TD MkII
For the nominal amount of money required to do a proper balance I’d leave it in the hands of a known shop. They have the equipment and tooling to perform the job to high standards and in a safely managed environment. A properly done balance job is especially important with regard to our engines. Although I commend the DIY spirit to take on such a project I don’t believe this an area where one should be taking financial shortcuts. It may come back to bite you should you come up wrong, your engine breaks and scatters itself on the floor. It doesn’t have to be a “race engine” to self destruct.



Bill Chasser
TD-4834
TD/c-8151
TD/c-16920
TD-19408
TD-24060

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