Design


Acknowledgement


As mentioned earlier the first people to attempt a world speed record on a totally wooden bike were the people involved in splinterbike.co.uk, and it is only right to wholeheartedly acknowledge their imagination. Their site gives a lot of detail on the construction of their bike and, while Narnia is built to a totally different design concept, some aspects have been copied from their design, notably in relation to the use of specific glues in lieu of tyres.


The Concept


Building structures from wood has been carried out since time immemorial, but making something that can not only move but can move quickly and safely is a different matter. The Wednesday meetings in the pub gradually became more focussed in relation to how components should or could be made, to such an extent that other regulars dubbed the trio Scrapheap Challenge!

After a study of the rules governing construction and use of the wooden bike, certain basic decisions were made. 

Firstly, and unlike Splinterbike, the frame would be made of box sections skinned with thin plywood, (plywood being acceptable under the rules). Secondly the wheels would not try and emulate a normal bike by having spokes but would rather be made of two cone sections joined at the rim and spaced out at the centre with a hub, rather like two cymbals. Finally and perhaps most controversially  chain drive would be used to transmit the power.  This latter decision was only made after a very rough mock-up had been made and "tensile tested". The test actually failed but the sample material sections were quite small and the load at which failure occurred indicated that the design could be made to work.

The strap line on Splinterbike is  “No bolts or screws – just wood and glues!“ and the strength of modern adhesives never ceases to amaze.  For the vast majority of the construction ordinary waterproof white PVA adhesive as sold at all hardware shops was judged adequate, as in most cases the bond strength was greater than the parent wood. The most significant areas where other adhesives were used were in the fixing of the ply cones to the hubs and rims, where an Evo-Stik   product called Gripfill was used as this had good gap and bead filling properties; and as mentioned earlier for the "tyres" an adhesive called illbruck SP050 and illbruck SP060 made by Tremco illbruck is layered on the rims. In this aspect we have simply followed Splinterbike's lead.