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The Velassi
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The storyThe Velassi ‘V1’ is the first version of the Velassi that I built in April 2019 after a long phase of study and preparation.
I’d never built a bike before, nor even ridden one horizontally, so it was a big gamble, which I managed without any major problems, but only after a long period of study. The choice of wood as a construction material posed particular engineering challenges, due to its great flexibility and heterogeneity. This too was a gamble. At first, I had to make a few reinforcements to improve its torsional rigidity, but the bike has never had any behavioral problems or failures. I did, however, have to redesign and rebuild the handlebar joint in early 2021, as it was beginning to show serious weaknesses. However, as with all epoxy resin work, this bike should have been given at least one more coat of epoxy and varnished to reinforce its protection against UV and humidity. Having decided to build a new one, I never took the time to dismantle it to apply another coat of epoxy and varnish, and a few traces of moisture penetration through the resin appeared in a few places, and the ‘head tube’ had problems swelling after a very wet ride, necessitating a loosening of the steering. Unsurprisingly for a first design, it does have a few flaws and I quickly decided that there would be a new version and, as I’m getting on in years, that this future version would be electric.
I hesitated for a long time to build the V2 in riveted aluminum, but I figured that changing the material would delay the construction even further, and I finally took the plunge at the end of 2021 for a new wooden construction, but in pine and fir instead of the oak of the V1 version. Images 
 
 while going through:  
 
 
 
SpecificationsBicycle specification (small size, for 73 to 80 cm inseam):
Single-plate transmission on 8-speed Nexus hub. Very short development (5m in 8th gear), so no pedaling on descents. I’ve modeled several frame types, including a single-beam, but in practice, two scissor-type trellis frames, one in wood and the other in steel, seem the most practical, while remaining relatively light. The stresses on a long-wheelbase bicycle frame are quite considerable, and I have little confidence in an amateur-made single-beam frame (aluminum bikes made by pros are heat-treated after welding, and steel ones are a bit heavy) Main problemsThe bike is heavyThis is not specifically related to the wooden construction. A recumbent bike is always heavier than an ordinary bike, because of the seat, the shape of the frame and the very long chain. What’s more, this bike is equipped with indirect steering, which means it has an additional control linkage and an extra bearing for the handlebars. It also has a very long frame. My canvas seat is also significantly heavier than the ‘shell’ seats found on performance recumbents. This resulted in a weight of around 22kg once all accessories were fitted. Pneumatic equipment with puncture-proof tires doesn’t help keep the weight down. Performance is not goodUsing a gearbox with very modest power reduces efficiency, especially as I installed a double-roller tensioner to absorb the length variation due to the suspension. This was a design error, and a single-roller tensioner with an extra roller at the bottom should improve efficiency. The handy hub dynamo also absorbs quite a lot of power (maybe 9W), as it’s not a dynamo specifically for small wheels (my front wheel is 20”) and it turns faster than the manufacturer intended. While it provides power at very low speeds, it absorbs more of the rider’s energy. These two elements, combined with a choice of tires adapted to the ride, lead to a fairly low output. The development range of the Nexus 8 gearbox (306%) is insufficient.While this range is sufficient for riding on flat terrain, as I’ve adopted a fairly low gear ratio, in off-road use, on steep climbs, I’ve clearly missed shorter gear ratios. One solution is to have a double chainring (made possible by the double-roller tensioner, whose original function is exactly this). Stability at low speed is not very goodSince I didn’t know whether I’d be satisfied with a low-handlebar steering system, and since I had the opportunity to buy a second-hand Rans Stratus fork, I adopted the same geometry as the Rans, with a very raked steering system that would also allow me, if need be, to have n high handlebars instead of the indirect low-handlebar steering system. Such a geometry poses stability problems at low speeds, but I was able to improve the situation by adding a steering spring. And with a motor?The first three shortcomings disappear if the bike is fitted with a motor. The weight only becomes a problem if you have to negotiate stairs or ramps, which is quite rare. Efficiency becomes irrelevant, and a motor greatly reduces the range of speeds required. As for the lack of stability, this has been corrected by the new geometry of the Velassi V2 and, in any case, the engine’s power means that the minimum stable speed can be reached more quickly. A gearbox for a touring bikeA gearbox is a practical and comfortable piece of equipment, even more so on a recumbent bike where it’s very difficult to restart if you’ve forgotten to downshift when you stopped, because you can’t get into a dancer’s stride to help you start.
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