First Prototype of RC Land Yacht with Steering

by Jason King on April 3, 2016

3D Printed Land Yacht PrototypeIn my last 3D Printed RC Land Yacht Blog Post I had only just began doing some research and designing a few parts.

My goal since last week has been to have a basic rolling chassis up and running, hopefully with working steering.

After staying up until 3am a few times with OpenSCAD I have just about managed it.

In the next few paragraphs I’ll describe what I’ve done so far, mention a little battle I had with trigonometry (I can barely even spell that word) and show you a video demonstration of my yacht so far, with some commentary from myself.

Remember it’s just a prototype at the moment, as this stage of development is all about testing, tweaking, re-designing, re-printing and repeating.

As I’ve never designed my own RC vehicle before your input into this project is very useful to me, so feel free to comment with suggestions, tips or criticisms. It helps keep me moving forward in the right direction.

3D Printing Meets Trigonometry

Since designing a wheel, rear axle mount and wheel nut last week (I never know what to call some of these parts when I design them) I’ve been working on the chassis and steering mechanism.

As you can see from the pictures and video, the chassis is made of 8mm x 8mm cross section wooden dowel, with 3D printed joints. I’d like to 3D print the entire chassis at some point, but whether this is feasible and sensible is another issue.

Due to the triangular shape of the chassis I had to step back to my school days and tackle some trigonometry, largely to work out the angles of the holes in the joints I made for the corners of the dowel triangle.

Here’s some of the maths involved, but don’t be scared away it’s actually quite simple and in a way unnecessary, but I’ll explain what I mean next…

 chassHypLen = 600;
 chassBasLen = 100;
 chassHeiLen = sqrt((chassHypLen*chassHypLen)-(chassBasLen*chassBasLen)/4);
 chassBasAng = atan(2*chassHeiLen/chassBasLen);
 chassVerAng = 180-chassBasAng*2;

These calculations use the Hypotenuse and Base lengths to calculate all three internal angles of the triangle. With an isosceles triangle two of the angles are always the same.

I won’t bore you with the details but I used an online calculator to find the actual values, then found the calculation and added them to OpenSCAD, using the known correct values to test my code. This is so that if I change any dimensions in the chassis the joint angles will recalculate automatically and the new joints will be re-rendered with a single click of the mouse.

That’s what I love about OpenSCAD, that little extra work up front means that if you want to change the design in the future it almost redesigns itself, given a few parameter changes.

So, the chassis joints are all designed, 3D printed and fit quite well. Now it’s time to design and add some more parts to this basic chassis.

Land Yacht Parts Designed So Far

Here’s a quick list of the parts I’ve created so far, all in OpenSCAD as you can see…

  • rear_axle_joint.scad
  • rear_wheel_axle.scad
  • steering_arm.scad
  • steering_bar.scad
  • steering_joint.scad
  • wheel.scad
  • wheel_nut.scad
  • global.scad
  • yacht.scad

Most of these files represent separate parts, except for global.scad, which contains global parameters used by multiple parts and yacht.scad, which I use to import and render different parts in one file to see how they fit together.

Land Yacht SteeringThe most significant developments so this week have been the steering mechanism, which looks a little chunky and clunky in this first prototype, but you’ll see from the video it basically works.

What’s good about this design is that if you’ve built the OpenRC Formula 1 Car then you can re-use the radio gear in this model.

I purchased a couple of extra servos (same as in the F1 car) and a battery box from HobbyKing. These only cost a few pounds but it means that I won’t have to take the F1 car apart to build the Land Yacht. I also use the same bearings in the wheels. I had some spare, but I did steal two ‘temporarily’ from the F1 car so will have to buy more.

The only place I’ve used screws so far in this prototype are to hold the wheels on and to attach the steering servo to the chassis. I’ll be designing proper servo mounts in the near future. I’ll also need some screws in the steering mechanism because at present it only holds together due to friction.

When it’s all complete I’ll publish a full parts list with details of where I purchased them from too, which should make sourcing these as easy as possible. All the 3D printable parts will of course be on Thingiverse when release v1 is ready.

RC Land Yacht Video

As they say ‘a picture speaks a thousand words’ and I’m sure a video speaks more so it’s time for a quick demonstration of what this thing looks like up to now…

Besides my ‘not so great’ commentary I think this video helps to explain what progress I’ve made. I’ll be needing to design some NinjaFlex tyres soon and make the steering mechanism more solid and a little less chunky.

After this I guess I’ll be moving on to the sail and how we controll that using the other servo I bought. I can already visualise this in my mind and how it will work, but I just need to use OpenSCAD and my MakerBot to make these ideas tangible.

I hope you’ve gained some knowledge, inspiration and maybe even some entertainment from reading this. If so feel free to Like and Share it, then follow my progress on my dedicated Land Yacht Web Page and in my 3D Printing Group on Facebook.

Thanks for reading and thanks for taking an interest in my newest 3D printing project.

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