broken barrel fins

[EDDIE SIMPSON]

hello,
i wondered if anyone here has weld repaired broken barrel fins and what or where did you find replacement cast iron from?
eddie

[V500]

The best source is another old knackered barrel!

[iansoady]

Yes, I had one knocking about the shed for years till I finally got fed up of tripping over it!

I had success with JB Weld on my Norton. Invisible and was in use for 3 years.

[Greenfield]

I've had a few fins repaired over the years. The last time the welder used 3mm sheet steel to fabricate the missing piece of fin and I think the key is to use a high chrome welding rod. By welding it, the fin will then act as a cooling surface as originally designed. Its obviously a lot easier if the broken fin is at the end of the row.

[chaz]

I know its hard to find one at the moment but try to find a foundry. ready for melting down again.
we used to raid our foundry slag piles where flash was cut off of castings.

lower melting/welding temp needed .

[tdc]

jB Weld is ok on a small piece of missing fin . A few years ago I did manage to get a replacement A10 re sleeved barrel cannot remember from whom, with std pistons also if you get the right rods you can weld cast with an Ark welder . Good luck .

[Mike Farmer]

 
Hi
I have done this myself and did a complete M20 head repair. It took forever but was quite satisfactory. I used old piston rings because thats about the best cast that I can get hold of. I used Oxy/acet.I put picks on here at the time. I'll try to find them now and repost

[Mike Farmer]

 

PS I dont have the gas kit now.

Mike

[EDDIE SIMPSON]

thanks for all the replies
i will try steel plate if i can find any the right width and maybee try arc welding in small single puddles to avoid overheating. i think jb weld would look messy on cast iron barrels but if i had oxy acet bottles that sounds the best way with the correct rods for cast iron.

[cornishbob]

there is some goo goo (technical term) that is used in the aerospace industry thay will stick like the proverbial to a blanketb ( something to do with crystal structure and chain reactions but its all gone in the mists of time to me now).

trouble is i cant remember what it was called and dont even know if its available on the open market.

probably wouldnt work anyway but just saying

i'll get me coat

[ferretjuggler]

I weld for a living,  but my experience with cast iron is very limited.
I can remember welding a cast iron  bracket from a tractor at Handsworth Skillcentre in 1984.
We did what the instructor told us to, but the damn thing shattered.
Obviously that instructor wasn't as clever as he thought.
Afterwards we learned that we should have pre-heated the pieces of casting as hot as we could reasonably get them before welding,  and then buried it in dry sand immediately after welding to slow down the cooling process.

[EDDIE SIMPSON]

i ve come across a few repaired fin barrels so i know it can be done but its cleaning and shaping the spare fins that is holding me back. still looking around for metal plate.

[ferretjuggler]

Sad to say but there are quite a few BSA barrels out there with massive damage to the bottom part of the bores, like big chunks of cast iron missing.
Theoretically repairable,  but otherwise a cheap source of spare fins to repair other barrels or cast iron heads.
Or failing that,  possibly the fins from a lawnmower engine or even an industrial air compressor.
Something tells me that welding mild steel fins onto an iron casting isn't a good idea.
Different heat expansion rates I would think

[V500]

And given the sand cast finish of the original head or barrel, a piece of M/S is going to look noticeably different even when painted, as I found out on a repaired barrel some years back.

[Mike Farmer]

 

Picking up on the point of welding mild steel to cast. I had a conrod end come through the side of a vintage tarctor engine and I gas welded a mild steel patch on. As far as I know its still going strong. But you have to use cast filler rods as I said for a good job I use old piston rings.

Mike