Flywheels and cranks

[bmcecosse]

I don't get it! ALL the flywheels and cranks for the inline A series have the SAME basic bolt pitch. What you have must be non A series parts.. I'm sure you can make it fit....but why ??

[bmcecosse]

LUR - start a new thread !!

[LUR759H]

ok ta!

[andypocock]

I don't get it! ALL the flywheels and cranks for the inline A series have the SAME basic bolt pitch. What you have must be non A series parts.. I'm sure you can make it fit....but why ??

Well if I do have the only A series in the world with a different bolt pitch I shall have to make it fit because I'm not about to go out and buy another crank for it

Andy

[bmcecosse]

I've NEVER heard of it - but I suppose it's 'possible' that the 10CC engines had different bolt pitch - and used a special matching flywheel... But it's never come up before! Even the Marina 1275 fly is the same pitch as all the other engines - even though it is a larger diameter fly. I would have thought that if BMC spread the bolt pitch for the 10CC engine - they would continue that pitch to the 1275 engines.

[philthehill]

See
http://www.spriteparts.com.au/tech/flywheels.html and all will become clear.
As I said in an earlier post the 10CC and 10CG flywheels have different part numbers and from the web post just quoted I can see why. From the photo of the Mk 111 Sprite/Mk 11 Midget flywheel and comparing and measuring the 4 bolt holes with the earlier 4 bolt flywheel it can be seen that the location of bolt holes is different and by approx the amount quoted above.
Also note the comments at the bottom of the page.
So not all 'A' series flywheel bolts are at the same pitch.
So even I have learnt something from this exercise.

[andypocock]

And I've just be reading here:

http://www.spritespot.com/phpBB3/viewto ... =14&t=5948

Here is a flywheel drilled and bored just as I have to:


It's amazing how much you can learn about an obscure subject in one evening

Andy

[philthehill]

Andy
Many thanks for posting the link and the photo.
The machining work does not look to be that onerous and plenty of meat left around the new bolt holes.
Best of luck with the conversion.
Please let us know how it all worked out.
Phil

[andypocock]

Thanks Phil.

For the record, here's the offending article:



Andy

[bmcecosse]

And it's going in a tractor?? The bolt pitch is a new one on me...amazing really - especially as the 1275 didn't follow suit. Good luck with it...you may want to get the fly balanced after your work...

[andypocock]

Thanks BMC. I'll keep you posted.

Andy

[andypocock]

Here are some photos because we all like a good look:

Morris crank 1.75"


MG crank 2"


Flywheels with a couple of random bolts for comparison


Andy

[bmcecosse]

Amazing... consider fitting a new crank tail bush while you are in there....

[andypocock]

Amazing... consider fitting a new crank tail bush while you are in there....

There are a couple in the post from ESM ...

Andy

[andypocock]

I picked up the flywheel today from my local friendly machine shop

So off with the MG backplate and on with the Minor one - after a little opening out around the crank to clear the larger bearing housing



It was looking good at this stage but when I put the flywheel on it didn't feel quite right. I took it off for a look and it was a while before I realised what was wrong. The mounting face machined on the back of the Minor flywheel was almost exactly the same size as the end of the larger MG crank. It looked fine but it was sitting on the tapers at the edge of the crank not face to face as it should be.

Back to the machine shop on Monday to get him to machine the mounting face a little bigger. 100 thou will be more than enough. It doesn't need a great big flat like the MG

Andy

[bmcecosse]

That's a 948 backplate you have on there....will it give enough clutch clearance ?

[andypocock]

948 backplate, flywheel, clutch and smooth gearbox. It should work BMC.

But you never know

Andy

[bmcecosse]

It 'should' - but does that crank flange stick out the block same distance as a 948 ??

[andypocock]

It 'should' - but does that crank flange stick out the block same distance as a 948 ??

It does. I have had a good measure so fingers crossed

[andypocock]

Finally had a couple of free hours to get back on the Minor this morning.

So out with the old engine

Which some kind soul had seen fit to attach a 12G940 head to. That can go in the collection.

Then time to start moving the ancillaries across. It's starting to look like a Minor lump now


A quick measure showed the face of the flywheel in to be the same distance from the rear face of the backplate on both engines. So it should be plain sailing.

Andy