Hi Wozza,
Would your Braided Sleeve be suitable for making tubing to be used for a Bike Frame. The tubes I have in mind are "Box Section ish" rather than conventional Round Tube. As yet I am undecided whether to use a mandrel type construction or a Mould and Bladder process. I have Vacuum equipment also.
Certainly braided sleeve is suitable for produce tubing such as that found on a bike frame, it is fairly common to see frames, seat-posts, bars etc.
If you were producing a round section I would defiantly suggest manufacturing them using a mandrel/shrink tape method as this is by-far the simplest construction method and is likely to yield the best results, however if you are producing a angular box section the shrink tape will concentrate pressure on the corners and leave the 'flat' sides resin rich, this type of section would really require an external mould and a bladder or core to apply the pressure. There would be some tolerance on the shapes that could be mandrel formed though... Oval sections or heavily rounded box profiles may form very well without excessive pressure variation.
Any advice on Fabric Weight and number of layers would be greatly appreciated. In fact any advice even if it is to say forget the idea!!!!!I know this is not an easy one to answer with regard to structural strength etc but just some general advice would be greatly appreciated.
Well I will keep it general! on a typical road frame here are the approximate wall thicknesses used;
Head Tube - 2mm (taper to 3mm around bearing journals)
Downtube - 1mm
Top tube/Seat tube - 1.5mm
Chainstays - 1.5mm
Seat Stays - 1.75mm
Bottom Bracket - 3mm
All joints tend to taper into a thicker wall. Now obviously material selection and orientation will have a huge bearing on performance here's an example 1.5mm frame tube layup;
200g Plain weave - 0-90 orientation (inline with the tube) 0.2mm thk
200g Unidirectional - 0deg (inline with the tube) 0.2mm thk
200g Unidirectional - +30deg (30deg off from inline) 0.2mm thk
200g Unidirectional - 0deg (inline with the tube) 0.2mm thk
200g Unidirectional - -30deg (30deg the other way) 0.2mm thk
200g Unidirectional - 0deg (inline with the tube) 0.2mm thk
200g Plain weave - 0-90 orientation (inline with the tube) 0.2mm thk
Some builders will choose only to use Unidirectional throughout some only woven cloths some a hybrid (like the above example) each has minor advantages/disadvantages, the main thing to consider when attempting frame building is to expect it to take a few prototypes before you have anything with performance comparable to commercially available frames. That is by no means discouragement because it is an incredibly rewarding process, we have many customers who are producing frame of exceptional standards, each one using a slightly different method that suits them!
Paul StathamEasy Composites / Carbon Mods - Technical