Flywheel splitting/big end replacement

[Paul Gasson]

I managed to get the bottom end apart today, that crank pinion nut was a real struggle, yes I know it’s left hand!

It was full of solidified oil and the outside covered in oil soaked sand.

The engine has not been run for decades and the piston was rust seized, there has been some corrosion to smaller insignificant parts but will my steel flywheels be ok? There is some material loss on the sides, outer rim and where the spacer shims run.

[will_curry]

It's a shame they're so rusted. I think steel flywheels look so much faster
than the cast ones.

Unless I had a better set waiting I'd use those. The spacers on the crank shouldn't
turn as long as everything is done up properly. Whether there's enough metal gone to
upset the balance I wouldn't like to guess.

The loss of metal is interesting. It looks as though the engine was almost at TDC with the
cases about half full with water. However there are two areas of significant loss on the
rim near to the bigend which I wouldn't have expected to see.

[Roger Gwynn]

No worries, the volume of metal lost is insignificant. 5-10 gms at most out of perhaps 4000.

[garycullen]

One of the fly wheel pic’s shows a sludge trap on each fly wheel?
What is that about. I would think one doesn’t work since internal oil ways won’t line up surely?
Interesting.
Gary
Auckland

[Paul Gasson]

You are correct to say it does not work, one hole filled to overflowing (right down to the big end) and the other is perfectly clean. Looking in the sludge tube hole I can see the tapered big end shaft at the bottom, there is no hole through it. Maybe it was more cost effective to make one flywheel and accept the extra cost of the extra screwed plug?

[garycullen]

Paul, I got two built up single flywheel sets with my pile of bits. Both had only one flywheel with a sludge trap.
I suspect that your set has been made up by a PO at a later date using sludge trap flywheels. I don’t think Ariel would have shipped as yours are. Maybe Paul J or Roger G can comment more accurately on this. Anyway I wonder what impact on balancing is, probably not much as weights will be similar. My non sludge trap wheels have more metal removed.
Cheers
Gary
Auckland

[will_curry]

I've just looked at two pairs of 500 steel flywheels, one prewar and the other post
and while both of the drive side wheels have holes drilled in them as if for sludge
traps neither of these holes is either drilled through or even tapped to take a trap.

I've often wondered why Ariel drilled into the drive side wheel - all it can possibly
do is weaken the wheel around a very critical point - where the big end fits.

[nevhunter]

It doesn't seem a good idea but where the balance holes are drilled (even originally) can have a worse effect. Anyhow I've never seen a steel wheel fail.
What I have found is they are harder to line up when they've had a hard life. Steel can distort and Iron usually doesn't. I balance each wheel individually to the same counterweight effect.
To P Gasson that rust may slightly effect the balance. Check it if you are fussy. Use 65% balance factor unless you know better. I always try to get a tapered bore gudgeon. Any weight saving in the up and down bits helps the result .Nev

[Paul Gasson]

Gary, I checked my copy of the parts list, which is a bit difficult to follow as the main one is for 1947 with supplements showing mistake corrections and actual changes each year to 1950. It shows 1066-36 (A7/546A) steel gear side and 1071-36 (A7/546) steel drive side for the NH, it also lists 2 1077-33 oil purifier plug for NH only, all other models have one. I checked the corrections lists and changes in the supplements to 1950 and cannot see any changes.

So, there does seem to be a difference because of differing part numbers. The numbers I quoted appear to be just the flywheel as “spindles” are listed separately. However, it does look, to me, that both sides should have the screwed plug.

Nev, thanks for your thoughts as well. I have seen some parallel bored pins in Triumph engines and they do weigh far more. I am lucky as I already have a suitable barrel on standard bore, although a little worn and an old stock +0.020” piston with tapered pin. I will think about balancing as it was not really in my plan. Paul

[paul.jameson]

When I ran my Red Hunter as a 350, it had steel flywheels. Each flywheel had the sludge trap in it. So the sludge trap in each flywheel does seem to have been standard at some point. It is possible that the Works used timing side flywheels as drive side ones if they were short of drive side ones for some reason.
We have the drawing for A7/546 and A7/546A is on the same drawing. Both flywheels have the sludge trap holes but the one on the drive side is not tapped and there is no drilling through to the big end.