magnesium welding interesting

[simpo1961]

Hi, does anyone now of a good TIg welder in the west london area?

I have a rare Kirk precision magnesium bike with a crack that needs welding and I am having trouble finding a tig welder. I know its only a small job but its a design classic and I don't want to retire it for a crack that is only 2 inches long. It is in the head tube mind you
Anyone interested in unusual bikes see http://www.kirk-bicycles.co.uk/Kirk.htm http://
//www.kirk-bicycles.co.uk/Images/Kirk/kirks_008b.jpg

 

[hotrodder]

Don't know of anyone in west London, i'm SE London/N kent but don't have any filler wire in stock (mag wire is getting on for a couple hundred a kg so i tend to just buy a pack of 12 lengths when a job comes up, doubt i've more than a couple of stubs kicking around), so as a min you'd be looking at around £50-60 in order to cover the cost of filler wire! If noone else here can help (has wire/knows of somewhere) other suspects that weld mag on a more regular basis and thus have wire in stock would be 'higher end' motorsport fabricators- probably someone (or someone that knows someone) around Brands Hatch or other circuits. Most of the other type of places i can think of re. mag welding almost certainly wouldn't be interested.

Where abouts in the head tube? Any chance of pics? Given where the crack is i'd like to know some more details regarding the alloy used and any heat treatment too before i'd consider it- from the quick scan i've had through the link i'm thinking they may have kept fairly schtum regarding these details?

 

[Shox Dr]

HR, Theses frame were cast ISTR, (can you not remember them)

 

[chunkolini]

Kirk precision bikes?
Well dodgy, I almost bought one years back, I would reckon it is knackered.
Why dodgy? they were too stiff, like riding a plank, and yet some of them were quite flexy. And cast magnesium is not the most sensible material for bike frames, I kind of like the retro futuristic styling and graphics though.
An interesting experiment.

Chunko'.

 

[hotrodder]

Yeah i remember 'em Shox, the words 'flexy' and 'dead feeling' come to mind but i don't recall ever riding one so probably someone elses thought's i'm remembering.

With a cracked headtube part of me is with Chunko' thinking it's time for a really big bonfire but i suspect there aren't many Kirks still about

 

[Shox Dr]

I rode one, back in the day scaffold pole would be a good description. Rode like an Ali frame that needed heat treating again (AKA Pace RC?? after 2/3 seasons hard racing)

I saw one in town the other day funnily enough

 

[simpo1961]

alloy

It has been suggested that they are made from
a magnesium casting alloy called AZ91D by this guy

http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=49794&hilit=kirk+precision

who looks like he has done a nice job !

 

[simpo1961]

risky

ps I've ridden this one around 400 miles and it seems quite nice smoother ride than my steel frame job but more stressfull As I have one eye on the crack

 

[simpo1961]

sticker

'course i could just buy a big sticker ........

 

[Autolupus]

Weldability
AZ91C and AZ91E can be readily welded by the gas-shielded arc process using AZ91C or AZ92A rod; stress relief required.
AZ91A, AZ91B and AZ91D not weldable.

Source: http://mg.tripod.com/asm_prop.htm