Magnesium

[JohnnyO]

Exactly Col, that's what I was referring to in my previous post.

[pancho]

Mag wheels made for racing cars had an EXPIRY DATE stamp. Thats enough for me! If they don't have a date stamp that' s a bit suss either they are not Mag or the manufacturer is negligent.

[Nathan S]

Why does magnesium die?
My memory of high-school chemistry lessons is poor, but I thought the main problem is that the material ages, AND it has a poor fatigue life.
Most car/bike forums seem to point the finger at corrosion, which seems unlikely.

What I'm getting at, is whether x-raying and/or magna fluxing are useful procedures?

[FourstrokeForever]

I don't see a problem with having replica parts made. Replica parts keep old bikes running SAFELY. Magnesium in particular fatigues because of light weight and poor metallurgy from the factory of the time. Add in water onto any non painted part (inside of brake plate and hub) and corrosion starts very quickly.

Just like wide foot pegs are considered to be a safety improvement, so should certain magnesium part replacement.

[KTM47]

Historic Road Racing and Historic Car Racing already recognise problems with old parts and to my knowledge both permit replica parts.  There are so many parts that I think you can build a brand new Manx Norton from new parts.  You can also get a brand new 67 Mustang and 68/69 Camaro unibody for each and all the other body panels.

So we just need the correct rules to permit it.

Also why does anyone think wide pegs are permitted.  There is nothing in the rules that say they are.  It is just another one of those unwritten rules.

[sleepy]

Historic Road Racing and Historic Car Racing already recognise problems with old parts and to my knowledge both permit replica parts.  There are so many parts that I think you can build a brand new Manx Norton from new parts.  You can also get a brand new 67 Mustang and 68/69 Camaro unibody for each and all the other body panels.

So we just need the correct rules to permit it.

Also why does anyone think wide pegs are permitted.  There is nothing in the rules that say they are.  It is just another one of those unwritten rules.

The replica Manx Nortons still look like a Manx not like those awefull looking CNC backing plates. Someone should give an original Maico plate to that guy who was doing the Aluminium clutch covers and get them cast, same with mag hubs. A good casting shop can use the original as a patern in most cases and it would be way cheaper than the CNC crap.

[Digga]

Nathan
If you want to know why Mg corrodes so quickly, then check out the link below but in short it is a very sacrificial & reactive metal so when placed in an environment with disimilar 'other' metals, it will sacrificially dissovle/corrode to protect the other metals higher than itself on the galvanic table. There are several new technologies in the marketplace now that enhance the corrosion protection & peformance on Mg but not viable &/or cost effective outside of aviation/aerospace etc. It has also been overtaken by the use of carbon fibre in other peripheral applaictions.

http://en.wikipedia.org/wiki/Galvanic_series

[pokey]

Im grateful for finding  parts in good condition where ever and if I can find them and I don't have particularly rare machines. this being the case some parts are getting almost impossible to locate.
its even harder if you have  something exotic

if someone can manufacture a replica that operates the same and looks the same as OEM then I would and do use them.
if a product is better than OEM quality for safety reasons I would use it as safety is paramount. if it also has a performance benefit as in limit flex in the CNC backing plate situation this should also be considered admissible  as no one wants an avoidable injury to deal with. So what if it looks different . An EH holden looks bloody stupid with seat belts and they didn't come with steel belt radials but they are safety modifications and they work and keep people alive.

 Safety first guys, none of us are getting any younger and I would like to see more of us enjoying the sport for quite a few years  to come.

[JohnnyO]

How safe would it be to use a pair of 1977 magnesium Marzocchi forks that have some corrosion pitting in the legs?

[Nathan S]

Nathan
If you want to know why Mg corrodes so quickly, then check out the link below but in short it is a very sacrificial & reactive metal so when placed in an environment with disimilar 'other' metals, it will sacrificially dissovle/corrode to protect the other metals higher than itself on the galvanic table. There are several new technologies in the marketplace now that enhance the corrosion protection & peformance on Mg but not viable &/or cost effective outside of aviation/aerospace etc. It has also been overtaken by the use of carbon fibre in other peripheral applaictions.

http://en.wikipedia.org/wiki/Galvanic_series

Yeah, I'm down with the reactivity of metals stuff.
I just have this recollection (which may be wrong!) about Mg alloys having issues with precipitation hardening all by themselves, over time. So even a brand new magnesium part that is sitting on a nice dry shelf somewhere is deteriorating, and closer to failure than it was when it was made.

I'm my memory is wrong, then I don't really understand what the issue is: If you want to avoid the risk then you manage the risk by replacing the parts or having them crack tested.

[SON]

How safe would it be to use a pair of 1977 magnesium Marzocchi forks that have some corrosion pitting in the legs?

I have no idea on the metallurgy
I just wouldn't do it

[kdx 175]

theres not much i cant cast in alumium backing plates for brakes ezey but will it be strong with out heat treating i dont know

[GMC]

What's happened with the rule book?
This is from my 09 book, it seems to have been removed from the current version
Why was this changed? Are my replica frames now not accepted with the current rules? WTF



Just spied a picture of a billet Maico backing plate, looked like a reasonably faithful replica to me (from what I could see of it)

I can see no reason why the replica rule would have been taken out of the book

[sleepy]

theres not much i cant cast in alumium backing plates for brakes ezey but will it be strong with out heat treating i dont know

The early Maico backing plate are aluminium and I doubt they were heat treated. The alum one are a bit thinker than the mag one. Think I've got one of each around here somewhere if you want to have a look at one. What sort of cost un-machined do you think they would be?

[Lozza]

What's happened with the rule book?
This is from my 09 book, it seems to have been removed from the current version
Why was this changed? Are my replica frames now not accepted with the current rules? WTF



Just spied a picture of a billet Maico backing plate, looked like a reasonably faithful replica to me (from what I could see of it)

I can see no reason why the replica rule would have been taken out of the book

Its a bit legalistic but you don't make a 'replica' anymore, you make a 'representation' of what appeared in the era. Replica has the meaning that it is exactly the same , representation is sorta kinda like if you squint