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@simon_brooke@mastodon.scot
2025-10-15 12:03:24

I've just bought test materials to evaluate the relative strengths of a flax/balsa sandwich composite versus a carbon/Nomex (aramid) sandwich composite.
Yes, I know the carbon/Nomex will be stronger, but would the flax/balsa be strong enough for my #Tricycle project?
#BikeTooter

The Biodegradable Tricycle
One of the design goals of my tricycle is as a prototype for sustainable transport. To be sustainable, it has to be fully recyclable, and the simplest way to make anything fully recyclable is to make it biodegradable: nature will do the recycling for you.

@simon_brooke@mastodon.scot
2025-10-06 19:44:51

The first actual physical part for my #Tricycle project has arrived today. This is an axle — actually a Cannondale Lefty axle — and it's nominally the front axle, although it doesn't really matter which axle it ends up being because they will all be identical.
#BikeTooter

A long narrow truncated cone of black anodized titanium(?), with flats for bearing seats turned into it at each end, and a rough sand-cast cylindrical mounting extension sticking out of the thicker end. It is lying on a varnished wooden surface.
@simon_brooke@mastodon.scot
2025-10-04 17:17:57

If anyone's been following my progress on the #tricycle project, I'm currently drooling over the very adjustable recumbent ergonomic rig shown in this video. I'm wondering whether I can make myself something even nearly this adjustable!
#BikeTooter

@simon_brooke@mastodon.scot
2025-09-16 14:27:49

I haven't actually written a new blog post about the #Tricycle project, but I have greatly amended and extended the last one.
#BikeTooter

Learning from CAD
As I reported in my [last essay on the tricycle project(../../2025-09-03-details-details/), I now have a CAD tool which I'm learning to use. So, learning to use it, I'm beginning to be able to visualise the tricycle, if not yet concretely, at least as an assembly I can look at and study. And doing that brings up several things.

@simon_brooke@mastodon.scot
2025-09-17 10:04:09

So, at last I have a rendering of the #Tricycle which includes a (so far fairly crude) model of the hull. This makes the whole thing much easier to visualise. Progress is being made.
I'd like to get the CAD model a little more complete, but actually this is enough to move onto an ergonomic prototype.
I'm about to start buying actual parts for this damn thing. It may actually h…

A rendering of the tricycle with the subframe inside a streamlined, teardrop-shaped green hull, and the four bar linkage holding the rear wheels embracing the tail of the hull.
@simon_brooke@mastodon.scot
2025-09-24 16:02:51

I'm still learning #OpenSCAD. This part, the lower knuckle for the four-bar linkage of the #Tricycle, isn't as smooth and aerodynamic as I'd like. But it's good enough, certainly for now.
The blue colour is just to make it easier to work with; the finished part will probably be c…

A CAD drawing of the lower knuckle of the four bar linkage. The body of the knuckle is an aerofoil teardrop in plan, with a radiused top and a rounded bottom. A boss on the outer (left) side surrounds the hole for the wheel axle. On the inner (right) side is an aerofoil stub to which the aerofoil section lower bar will be bonded. In the top of the knuckle is a radiused cavity in which the pivot on the lower end of the lateral bar will rotate. The part, which is coloured blue with yellowish-gre…
A view of the same part from in front. The hole for the shaft on which the lateral bar pivot will rotate can be seen.
The same part viewed from the lower front left.
The part in context. The lateral bar, wheel, and brake disk can all be seen, as can the lower bar, although this doesn't yet correctly join to the knuckle.
@simon_brooke@mastodon.scot
2025-09-18 14:25:41

OK, a sidequest on the #tricycle project: I'm going to have to do data capture, storage and display. I need to log speed, cadence, battery voltage, and some indicator of power consumption. I need to display at least speed, cadence, and projected range. I can do speed and cadence off hall effect sensors. I want to use #Lisp