1st post , about to make a carbon tandem frame In Australia

[latman]

I have made carbon Epoxy paddles for years (I was a serious Kayak paddler) and have always enjoyed cycling so I have decided to make a tandem frame for the Wife and myself , so I made a jig with engineered alloy extrusions and Have purchased round tubing from a local company In Melbourne Australia , I have made a few test joints with UD and woven carbons under sacrificial tow , and all with wet epoxy resins , the friend who gave me all the alloy also was able to turn up some 44mm rod for making 1 1/8 head tubes (with internal PF30 style cups) and 46mm rod for making PF30 BB shells , I have made test pieces of those already with 4 layers of 200gsm woven carbon . cheers Ian

[e-RICHIE]

Welcome, Ian.
Please add a first and last name to all posts here on Frame Forum, preferably your own!
http://www.velocipedesalon.com/forum...rum-36866.html

[latman]

no problems , My name really is Ian ha ha , a few more photos are attached , including the stays of a Broken BMC frame that are being re-cycled . cheers Ian Rowling

[dgaddis]

Cool project. Any worries that the stays were never designed for a two-person bike?

[Mark Kelly]

I take it the 4 layer pieces for the headtube or the BB shell are just for mockups and not what you are considering using for the real thing? 4 layers of 200 gsm should come to about 0.8mm if you've squeezed out enough resin, that's not really sufficient unless you have designed the joint wraps so as to make up the deficit and it doesn't look that way from your pics.

[Mark Kelly]

Sorry if the above sounds like criticism, it's meant to be constructive. Here's some more:

If the tubes shown are the 1mm wt roll wrap tubes obtainable from a couple of local suppliers, they are unsuitable for the purpose to which you are putting them. They are exactly as advertised: 5 layers of woven standard modulus carbon roll wrapped over a mandrel. I wouldn't use this in a road bike, let alone a tandem. There's not enough material there and all the fibres are at 0 or 90 degrees (0 being the axis of the tube). For your downtube, your top tubes and your boom tube you want at least half your fibres in an orientation that gives you torsional resistance, 45 / 45 is usually best.

One simple solution would be to grind the surface of the tubes you've got and lay up a few extra layers to give the fibre orientation you want. If you are using SM carbon I'd be thinking about five extra layers at 45 / 45, if you use an IM carbon you could think about four.

An additional note re the head tube: if you make the first layer in glass, basalt or similar and go for about 43.7mm ID, it makes reaming for the headset easier and the contact for the headset cups is non-conductive. I have the tooling for 44mm headsets, you are welcome to use it.

[latman]

I take it the 4 layer pieces for the headtube or the BB shell are just for mockups and not what you are considering using for the real thing? 4 layers of 200 gsm should come to about 0.8mm if you've squeezed out enough resin, that's not really sufficient unless you have designed the joint wraps so as to make up the deficit and it doesn't look that way from your pics.

I have a tapered Deda HT for the tandem and a commercial 56 ID tube for the eccentric BB , the self made tubes would not be good enough to use without additional reinforcement but I do intend to use them all.


Ian Rowling

[latman]

Cool project. Any worries that the stays were never designed for a two-person bike?

I hope they are strong enough , they are full UD and much fatter than anything else I have ever seen .


Ian Rowling