View single post by Huw Griffiths
 Posted: Tue Jan 26th, 2010 11:47 am
PMQuoteReplyFull Topic
Huw Griffiths



Joined: Wed Oct 21st, 2009
Location: Cwmbran, Wales, United Kingdom
Posts: 262
Status: 
Offline
W C Greene wrote: Find some carbon fiber sheets of the proper thickness, it ain't cheap but it will be as rigid as any brass frame. You can use CA or epoxy to glue the parts together and as tough as the cf is, you shouldn't ever need any bearings, etc. because the material wears like steel!A plate frame can be made rather easily and even details could be made with careful work. The only problem I see is that when you file or motor tool the cf, the dust is VERY VERY BAD! Do not breathe it or get it into your eyes!

In my last job, I frequently worked with carbon fibre sheet, amongst other things. Based on this experience, I would definitely echo Woodie's warnings about working with the stuff. In fact, I'd go further.

I was a "labrat", doing instrumentation in a university civil engineering department. A lot of my job was about installing strain gauges on test specimens - and teaching students how to do this work for themselves. A number of students and postgrads were doing experiments, to see if carbon fibre sheet could be used to reinforce damaged bridges - so I found myself fitting a lot of gauges to the stuff.

I agree the stuff is very strong and rigid - and probably self lubricating - it's also very cold to the touch, just like a lot of metals - but there the similarities end.

When you install strain gauges, you have to ensure that the gauge can't detatch itself from the specimen surface - with carbon fibre, this means abrading a shiny surface which is brittle, yet as hard as many of the abrasives you're trying to use. In desperation, one student just tried throwing superglue at the surface - this usually worked.

Abrading this stuff was one thing - cutting it was quite another. Carbon fibres are a bit like glass - very hard, very strong, but brittle - this is why I normally encountered it in sheets, about 2 millimetres thick. I wouldn't be surprised if the fibres were actually used as a matrix, embedded in epoxy resin and rolled flat under pressure before the resin cured - but I never saw how it was produced. All I do know is that it could only be cut cleanly using an industrial guillotine.

Perhaps I should qualify the words "cut cleanly" - I'd often find dust and splinters along the edges of the strips (or rolls) as supplied by the manufacturers - I quickly learnt to avoid these edges.

You know what often happens when you use a fibreglass pencil - dust gets everywhere (especially your hands and face, leaving them sore and itchy for days after) - fibres spear into your fingers (and you can't get the stuff out).

Wait till you try carbon fibres - then you'll know what real splinters are like. An unforgettable experience - that is a promise.

The really frustrating thing about both glass and carbon fibres is that they seem to find their way through a lot of personal protective equipment - carbon fibres also seem to be very efficient glove shredders (they work great on the plastic gloves labrats use when working on specimens).

Anyway, you now know why I hate carbon fibre with a vengeance. It's strong stuff - and it looks really nice - but it's evil to work with (and I'm not sure how well it would take paint).

That's my opinion on the stuff. If you choose to use the stuff, then good luck - just take care, that's all!

Regards,

Huw.

Close Window