Mould Making

The mould is just chipboard but it’s important to get the headtube accurately aligned.

IMG_20150917_170743306IMG_20150917_170241810

I lined up the centre drill to my mark, indicating the internal headtube centre line.

IMG_20150917_170402541

And then drilled.

IMG_20150917_170533599_HDR

I drilled both ends: for the second end, the centre line has to coincide with the drill axis, so I lined up the first end with the lathe tailstock.

IMG_20150917_170758914

Composite Manufacture

I’ve settled on a new design, after much toing and froing. I’m trying to get the advantage of bigger wheels, a lower seat and bottom bracket, as well as lighter weight, squeezed into the new prototype. To fit a low seat and rider around the larger wheels requires curvaceous framework which itself justifies the efforts of using composite construction, over my usual ali tubes, which are difficult to bend. Two further advantages are that once the moulds are made, this is a more readily repeatable process than ali tube fabrication and it should be considerably more structurally  efficient, i.e. lighter.

 

I’m currently making the soft tooling ie. moulds out of chipboard filler. The first pressings will be in S ‘glass with some carbon reinforcement. Ultimately though unidirectional carbon will be used. The pictures show the paper templates stuck on the main moulds part and outlined with a Stanley knife. That’s the start of a three day mould-making process.

 

IMG_20150915_093154556_HDRIMG_20150915_095235416_HDR

New Start

The carbon prototype and a rethink of the Switch function has meant the prototype is going to be quite different. I’ve also moved to a new workshop.

foto 1 foto 2

Article for BHPC Magazine

I’m writing a lengthy article for the BHPC magazine, Issue 120. (http://www.bhpc.org.uk/magazine.aspx) about the long road to a viable Switchblade. To be published in July or August.

New Ideas

I’ve a new design proposed for the row power (arm propulsion)  system. I think I can essentially package most of it below the top of the headtube. That would make things look a bit sleeker.  But it is not straightforward to do and will take  a bit of development. In the meantime, here ae some pics of an earlier prototype – perhaps the nicest looking one I made but it had a few major flaws –  looks aren’t everything.

Box 1 Box 5

Carbon

Extensive discussions with various experts have made me rethink where I am with fabrication techniques. It looks like the new frame is going to be a mixture of ali and carbon. I’m trying to get there quickly but still have something that looks presentable.  I can certainly save weight with carbon but making it strong enough is something I’ve previously paid inadequate attention to.  Here’s a bit of frame in my jig.

dropouts

Back to Aluminium

I’m reverting back to aluminium after experimenting with carbon;  my workshop carbon fabrications were structurally adequate but didn’t look very neat.  I see carbon as a great option for a lighter frame but I still have some basics to sort out and machining aluminium will help to address  these more straightforwardly and give a production ready finish which the carbon can only deliver with more work  and investment.

 

I’ve sorted out all the major design issues with the last prototypes (actually, the last eight or nine prototypes). What I mean is I’ve got the functionality of the Switchblade to work with a viable frame geometry for both manoeuvrability and speed (seat  height in the  low position is about 12”).  From now on,  its nearly all detail design. But that’s still a lot of work. I’ve been designing a new compact front fork, as there is quite a lot to squeeze in at the front end. The back end is now reverting to a standard dropout arrangement so at least I don’t have to modify my own hubs.  I’m planning on a completely symmetric frame design with a single central tube for  the lower g frame and smaller tubes on both sides for the seat frame.