In last weeks RC Land Yacht Update I had been modifying the steering mechanism and had just managed to 3D print a tyre which I’d designed.
This little 3D printed land yacht looked quite functional now, although still being without a sail it’s still really a soap box racer as it needs gravity to power it.
That gave me the idea of finding a gentle hill to roll it down and see how the remote controlled steering behaved.
I’d also decided that although the low profile tyre I’d designed looked cool enough, it needed a curved contact area at the front, as the front wheel leans into the corners.
In this quick update I’ll show you what I did with the tyres and demonstrate this thing weaving down a gentle hill with a YouTube video.
New Lower Friction Tyre Design
As I mentioned above, the front tyre needed a redesign so that it had a curved contact area with the road. This would have two purposes. The first is to keep the contact area consistent as it leaned into the corners, a bit like a motorbike. The second is to reduce the overall contact area with the road so that it has a lower rolling resistance.
I plan to experiment with different tyre densities, as harder tyres generally have less rolling resistance, but the consequence is that they’ll bounce more over bumps, so a good balance is required here.
The contact area with the road is consistent as the wheel leans into a corner and the rolling resistance will be reduced too, so all in all I think it’s a good improvement to the design.
The beauty of Designing Using OpenSCAD is that the tyre is fully parametric, so at the top of the OpenSCAD source code I have added this simple line of code which allows me to render any of my three tyre designs by just changing a single number.
I have the option of the original low profile tyre (1), a new improved low profile tyre (2) and the rounded version (3) currently in use on the front wheel…
tyre(3); // 1=orig low, 2=new low, 2=round
The image above is of the new rounded tyre rendered in OpenSCAD. As it worked so well at the front during testing I think I’ll be using it on the back too as I’m sure the low profile tyres will cause too much friction.
Mr Yacht Goes Outside to Weave Downhill
This is officially the first road test of this 3D printed ‘sail-less’ land yacht prototype. When I carried it to the car before transporting it to a secret testing ground I noticed how lightweight it was. Ok, so it’s not complete yet but it’s still really light.
I remembered I still had some accurate little scales from when I researched and wrote my 3D Printing Costs blog post, so I dug them out and weighed it.
Complete with the onboard radio control gear and four relatively heavy AA batteries it still only weighs 304 grams, which I thought was quite good.
That’s one of the benefits of 3D printing, being able to use a low infill density where you need the parts to be lightweight. With a honeycomb infill of about 10% the parts are still quite strong, especially for low load applications like this land yacht.
That’s why birds use a honeycomb structure in their bones, to achieve both strength and low weight. If it’s good enough for nature it’s good enough for my land yacht.
Now it’s time for the video of my land yacht pretending to be a soap box racer. I chose a very gentle slope for this first test, so I could film it easily and so it wouldn’t go racing off and get run over by a bus. Remember it has no brakes so I had to take things slow for a start…
As it’s currently gravity powered the first road test isn’t as exciting as some of the OpenRC F1 Car Project Road Tests I did a while ago.
However, when you factor in the ease of building this, the low cost of the small 3D printed parts and the lack of LiPo battery, speed controller, motor and charger required, it’ll be very good value for money to build and run this yacht.
What Next for the Land Yacht?
I’m excited about the next stage of this project, which will be to add a sail and have this yacht be able to run without gravity. This will require me to design more parts in OpenSCAD so that I can attach the sail to the chassis and control it with another servo.
I have found someone who can print my 3D Print HQ Logo onto a sail once I’ve made it. I might save that until later in the project because for now I want to make the yacht as functional as possible before making it aesthetically pleasing.
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