The symptoms of a 3 bearing crank failure?

[fatcatvera]

Managed to get the inspection plate off the flywheel last night to give the flywheel a wiggle. It definable moves around in a way it was never intended to! It's doesn't feel like it's loose on the crank, so I'm still working the theory that the crank is indeed broken. Engine should be out tomorrow so I can understand the failure properly.

@Chris KC - useful to know new 3brg cranks are available - any idea who I may be able to source one from?

Thanks

Ray

[Charles P]

Phoenix crankshafts
It won't be cheap

https://www.phoenixcrankshafts.co.uk/austin-7

[Ruairidh Dunford]

New three bearing crankshafts are available from Austin Seven Club Victoria (see: http://www.austin7club.org/) you must be a member to purchase from their spares department. Tony Press posted a link to the email of the Coordinator recently, I cannot find that post just now however.

If you remove the oil filler tube and shine a torch down inside you will see the webs of the centre main journal, getting a friend to rotate the engine may well allow you to see if the crank is indeed broken.

In my experience most three bearing cranks seem to fail across one of the webs, rather than the journal (will post a photo later), but that is not definative.

   

[Chris KC]

New three bearing crankshafts are available from Austin Seven Club Victoria (see: http://www.austin7club.org/) you must be a member to purchase from their spares department. Tony Press posted a link to the email of the Coordinator recently, I cannot find that post just now however.

If you remove the oil filler tube and shine a torch down inside you will see the webs of the centre main journal, getting a friend to rotate the engine may well allow you to see if the crank is indeed broken.

In my experience most three bearing cranks seem to fail across one of the webs, rather than the journal (will post a photo later), but that is not definative.

Yes from Australia. I have contact details and price Ray and will provide when I get home this evening.

[Chris KC]

Funny thing happened this afternoon Ray - a friend showed up at my desk and told me his brother's Ruby had broken its crank...

[Colin Morgan]

Looking at Ruairidh's photo above, that crank had a crack nearly all the way through before it failed - just the last bit on the right and the bit at the bottom was holding it at the end?  

When I stripped a spare engine and had the 3-bearing crank tested, turned out there was a crack starting in that region.  It was immediately promoted to doorstop, and could not of course be sensibly built into an engine, but it may have run a fair while longer before breaking, I imagine?  (I have no idea of the history or condition of the current crank in my car - though the journals are at -40 thou.  After 20 years, still drive with crossed fingers.)

Colin

[Mike Costigan]

... In my experience most three bearing cranks seem to fail across one of the webs, rather than the journal (will post a photo later), but that is not definitive.

Yes,Ruairidh, I think you're right; I'm pretty sure that's how my crank looked, so change my reply to read web not journal 

[Ruairidh Dunford]

I am sure that someone will have broken one across the centre journal.

I personally have found that:

-most three bearing break like the one in my photo, i.e the web.

-most 1 1/8" break through journal 3 or 4.

- most 1 5/16" at the rearmost part of journal 4.

There will always be exceptions for sure however.

[Chris KC]

I don't doubt Ruairidh's seen a few more of them than I have, here's what happened to mine though:

   
   

[Bob Culver]

Straying a little from the topic, and not based on a vast sample, but from 1 5/16 2 brg cranks I have tested, normally the largest crack is as per Ruairidh. But if the rear bearing seat has been welded, brazed the biggest crack is there. So when testing start at the back and work forward! Especially in the past many reconditoners ground radii tight and ruined cranks on many sensitive makes.