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MG MG Y Type - Flywheel - chunk missing.

"WELL", as they say - I was just starting to button up my flywheel and clutch assembly when I noticed this bite-sized chunk missing from the edge of the flywheel. 30mm by 5mm. How significant would this missing bit be in terms of balance and operation of the flywheel (and the clutch?)? The metal in the "bite" looks porous, though I'm no metallurgist - I'll try to append a closeup.
Also, might it be feasible to get an engineering workshop to fill the gap and balance?
Thanks for any thoughts.
John.


J P Hall

Fill with epoxy, someone suggested?
J.

J P Hall

I would take a guess that the chunk was broken when the ring gear was last removed and replaced? Ideally the flywheel should be balanced as part (and in sequence) with the crankshaft, front pulley, flywheel and clutch pressure plate installed. If not, then it really is a bit hit and miss on filling the missing chunk. I doubt that epoxy will make much difference in restoring the rotating mass of the missing bit.

This is obviously not an easy exercise if the crank is already installed in the engine - as it will need to come out again! However, a fully balanced crank assembly is a great improvement for the smoothness and longevity of the engine in service.

Regards, Ewan
E.J. Ward

I think my mate was being facetious about the epoxy; but if as I suspect, the flywheel is cast iron, it ought to be possible to mig a repair. The crankshaft is all reassembled and installed; the engine always ran sweet as a nut (don't know what variety of nut), without any special balancing of the components you mention, so I think we just try and repair the flywheel bite - unless Willy or anyone has other advice. Interesting, innit!
John.
J P Hall

When you look at a well worn ring gear on a flywheel it is always in one spot but this is not noticed in the running of the engine, The amount of metal missing from your flywheel would not be more than a worn ring gear ??????
Bob Wood

"Well" John--So how many mirrors did you break--you're not having the best run of luck there. It is enough to put the balance out, if it was a big revver you'd feel it vibrating up in the revs for sure--not sure if you'd feel it at that primary 2800-3000rpm spot but it would be out of balance and needs fixing. It's the sort of thing that breaks crankshafts long term.
Where to start-
Bob, 4cyl engines stop in two positions between compressions meaning that ring gear wear is usually in two spots opposite each other on the ring gear which cancel each other out to a degree balance wise.

Epoxy is out--the last thing you need is a chunk of epoxy, especially if it's a metal based one, flying around loose in the b/housing.

Welding it up would be best, but cast iron needs care welding and with a 55% Nickel based rod or wire -There's a couple of different methods and if you go that way we'll run you through the process if you want.
Have you done much welding------? What welding gear do you have.

The other option, which because that flange is only there to locate the ring gear , could be to have a real decent look at that area to check there's no further cracking----If it's ok, then you could tidy it up ,then carefully measure up and mark out an identical section dead opposite on the other side of the flywheel and cut it out to even up the balance. As long as you got it to be as similar as possible the balance would be ok-(near enough)---It's an option, welding it up would be best probably but it needs to be welded properly and then machined/ground/filed back,--cutting out would be fine and easier
AND
Them flywheel dowels need knocking back flush to the flywheel--Then when you refit the flywheel to the crank, the best method is to bolt the flywheel on hand tight , then drive the dowels home, then tension up . The flywheel only fits one spot, the bolt holes are offset-
Yell out if you decide to weld it up
Willy
William Revit

Thanks as ever, Willy.
1. I ran over a gentleman of eastern origin, broke several mirrors and threw salt over the wrong shoulder.
2. Learning basic (mig?) welding is something I want to do now being safely retired. Fortunately, I have a mate who welds for a living, so I'll be farming this job out to him.
3. OR, if he prefers, we'll go your second option, and lighten the opposite side to suit. I had considered that initially, but deep down I always like to try to "fix the cause", rather than work around it, where possible. Sometimes that approach is neither sensible nor cost effective, and I relent.
4. The dowels - yep, I'll have a look at that this morning. I thought they were proud in order to help offer up the flywheel to the crank flange. And as you say, it's clever how the holes are offset to help fitment.
Off topic, but the core plug arrived yesterday and was fitted - hence the intention to fit the flywheel and "crack on"!
John.
J P Hall

Yeah, if you haven't done much welding it'd pay to farm it out, cast iron is a bit weird to weld and care must be taken not to create cracks--unlike steel it doesn't expand and shrink with heat-
If you were doing it yourself you'd have to get a roll of nickel wire which you'd probably never use again--

Your welder man will know all about it-
Best practice would be to remove the ring gear and preheat the flywheel, weld it, let it cool slowly then machine it up and fit a new ring gear-

My advice would be to do it cold,it'll save having to get another ring gear--run this past your welder mate-
Just press the ringgear back a bit in that area far enough to be able to get a hacksaw blade in the gap.
Place a piece of copper sheet, hacksaw blade thickness in the gap---Warm the flywheel up just enough so that you can hold your hand on it comfortably-then with a 55% nickel rod (or 55% nickel mig wire) start one end and weld a piece about the size of a pea then
quickly' with a small pein hammer lightly pein the weld while/until it cools enough to be able to hold your hand on the weld, then next weld, pein, cool,weld,pein----till you get to the end----take time to make sure you keep peining till it's cooled off between welds--
Then grind/dress it up and get a hacksaw and cut the piece of copper sheet out and press the ringgear back into place

If you decide to do the opposite side cutaway, there's nothing wrong with doing that, there's plenty of lightened flywheels running around with giant pieces cut out of them

willy

#4 Dowels---It's important the dowels are well and truely driven into the crank, If they're left like as in your flywheel you have no way of knowing that they're secure in the crank when fitted up, best to knock them back a bit -hand tighten the flywheel ,drive the dowels in hard then tension up the flywheel
Then you know the dowels are fully located and doing their job of taking any sideways load off the flywheel bolts
William Revit

Fantastic detail, thanks Willy - and after all that, I've gone down the track of drilling out plugs on the opposite side; the level of difficulty in trying a weld repair was echoed by both local professional engineers I spoke to up here today. Like you, they both supported the lightening approach, and one of them did it for me on the spot.
With the dowels, I did exactly as you described - and then saw your post! Gotta be lucky sometimes.
Back to the reassembly tomorrow - I hope this discussion is as helpful to others as it has been to me.
John.
J P Hall

John,

Glad your flywheel was repairable.

Used flywheels for 8 1/2" clutches are readily available here for about $100US. I recently had a new ring gear installed for one $20. Of course shipping a flywheel to Oz would run up the tab! Hope your repairs were less expensive.

Rocky
Rodney C "Rocky" von Dullen

No cost at all, Rocky - that's the beauty of being a certain age and keeping your friends close - not like those "friend" things the youngsters claim to have heaps of on the interweb.
Also, living where I do in northern Queensland, one becomes inventive in working on one's own - same as many of us with this hobby I suspect.
That's interesting about flywheels in the states - mine is a 49er, so 7 1/4 inch, but still probably hard to find over here. If I had needed a replacement, I would have gone to Tony Slattery first.
Bob and Ewan - thanks also for your input on this and other matters. Remind me where you are in Qld Bob? - I know you told me, but I lost the piece of paper!
Cheers all.
John.
J P Hall

Hi John My YT is living on the sunshine coast with my other MG M type but I live in Herston Brisbane.It is good to here that your Y type is going back together.
Bob Wood

I remember now! Sounds like a good setup. Off topic for a mo, I wonder if there's an informal setup with (say) the Qld Y or T Type owners/enthusiasts? - it would be great to be able to round-robin information, swap notes like we do on this forum, advise or even help with jobs, parts, and so on. Even offer hospitality if anyone is travelling around. We would certainly be keen to offer anyone a stopover up here. Anyway Bob, just my musings. John.
J P Hall

Hi John.If you need a replacement 7 1/4" flywheel, I have one here in Melbourne.Cheers.
R E J Stewart

REJ, you're a gentleman. I'm ok for now, but have a son and other family in Melbourne and Geelong, so visit twice a year. Could be a cuppa and a yarn on the cards? Certainly if I'm in trouble with the flywheel I'll let you know.
John.
J P Hall

This thread was discussed between 09/08/2022 and 12/08/2022

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