One forward- two back :-(

If you drill and pin it it won't be very strong. Has it been in contact with sea water because that can affect cast iron. Knowing your workshop its not beyond your abilities to manufacture one out of say EN 24 a tough steel.
Martin P

I think salt water may well have played a part and just pray the crankcase is not as badly affected. Doubtless I will find out when I get a welding torch near it! Anyone care to comment on the choice of steel and machining sequence? The present feet have holes for pins in the (7/16 BSW) bolt heads. I fancy a shoulder and D head bolts would be better in steel? ttfn Roland

Roland, If you are going to make anything like a con rod you need to machine a small amount of material from one side and then turn over and machine a little and then turn over again because if you machine one side complete when you release the clamps it will resemble a banana. Stress relieving by heat would be helpful also. you are looking for a tough material in steel what you don't want is something that will work harden as this will affect its strength. Ill look in my books for a material for you. Mark out and machine the big and little end first that way you have a datum to relate too also if you are splitting the big end machine to a size then split and then finish the bore otherwise it will end up egg shaped.
Martin P
photos with it. The plaudits should come thick and fast.

Looks like a classic crystalline fracture, but it's a bit out of focus and my eyes ain't up to that much these days... :-((
Make the whole thing out of steel is my thought, easier to do, the engine is not exactly a high-revving screamer so forces on the rod and bearings are fairly low, plus it's a two-stroke so one power pulse per rev is nice and smooth.
Fabrication is another option but welding and big ends don't sit well together IMO.
I'd be inclined to have a look at a decent bit of flat bar 4" X 1" or 4" X 1.5" and turn it between centres. You'd get a good continuous grain for the rod along the length, and although the turning would be tedious around the thinnest parts, especially with the interrupted cut, you have the time!! :-))
Kind regards,
Peter
Peter Forbes Prepair Ltd Luton, UK email: snipped-for-privacy@easynet.co.uk home: snipped-for-privacy@easynet.co.uk

Thanks to all for their on and off group responses. There has been a great variety including: cast in steel, mill from solid (either mild or various better grades) or weld up. I'll leave the final decision until I have the crank/flywheel separate and the crankcase welded up. The BTW is in near perfect focus its the horrible grain of the CI that makes it look otherwise :-) ttfn

Further "progress" today which I think takes me two forward and three back! Pics at Roland