0.2 Introduction - crunchysteve/TriceratopsTwo GitHub Wiki

0.3 Introduction

Triceratops is a set of OpenSCAD plans for a "tadpole," recumbent, lean-steering tricycle. The plans are open source and free, and are very loosely reverse engineered from the principles of the AR-3, which is a patented design so, while these plans are open source, making this machine for commercial purposes probably breaches a slew of patent law - so, no commercialising this design, kids! Just don't. I couldn't afford a basic Trisled trike, at AU$4000, on my budget, and they're just a few hour's train ride down the tracks from me, let alone a US$4000+ machine, plus shipping, so I thought I'd figure out their geometry for a bit of fun. If we use these plans for that, that's learning.


If we quietly make the odd one in our sheds, we weren't going to buy an AR-3, so they haven't lost any income. Just don't be loud and obnoxious about it. You did it for the knowledge and skill, not to cheat a genuine manufacturer. If you can afford a commercial trike, Trisled, Greenspeed, Kaze AR-3, go for it! Please, really go that option. Building your own requires quite a lot of skill and hardware. Buy a new beast, with a warranty, and really enjoy your riding. If you can't afford that, build one for knowledge, to develop your skills, to help out a local with a disability, charitable stuff or learning stuff, never for profit. OK, that said, lets get on with the stuff you're here for...

For those who don't know, a tadpole trike has 2 wheels at the front and one at the rear. Sort of a wide head and a skinny tail, like a tadpole, right. A recumbent trike, or "sofa trike" as some like to call them, is an Ikea Poang chair on wheels. You ride it head up and feet first. The pedals are at the front. However, a lean steering trike rides more like a bicycle, you lean into a corner, rather than steer it like a car. Triceratops is all three of these in one. It works like this schematic animation...

Triceratops steering demonstration

0.4 Why This Kind of Ride?

Tadpole trikes have better cornering stability than delta trikes (2 wheels at back) than almost anything on three wheels, because the weight distribution of placing your backside just behind the steering with your legs out in front. There are also other advantages, such as lower wind resistance and apparently improved cardiovascular efficiency over a conventional upright bike or trike. Being low to the ground, regardless of "sports car" steering or lean steering, recumbent trikes have much greater stability than nearly any other vehicle. The advantage of a lean steering trike over any other bike or trike is it feels like riding a bicycle, you can steer no hands, leaning it with body weight... assuming you can ride no hands on a bicycle. I still can't, after nearly 50 years on a bike. (Hey, I'm useless at sports. Nerd cliche.) The other major advantage of a lean steering trike is no tyre scrub, which makes for better traction in corners and better tyre life. Because all three wheels lean, due to the horizontal kingpin and frame to steering arm tie rods, these things corner like they're on rails!

Trikes are, like e-bikes, also great equity access to cycling. The low seating and third wheel provide stability for those with balance problems and trikes can be electrified as easily as bicycles, rear drive or mid drive, to assist those who can't easily do nature walks because of needing mechanical mobility vehicles. Part of my reason for building this is to future proof my cycling as I age. I also plan to build one for a friend with a disability, who uses a mobility buggy in urban environments, but needs a more practical, more stable vehicle for nature walks and Melbourne's creek trails.

I feel obliged to warn you that a recumbent trike of any kind is low to the ground, therefore hard to see in motor traffic. If you're too cool to ride with a big-assed safety flag on the back, stay on the bike trails. <-- the only disadvantage. Is a "big-assed safety flag" really a disadvantage?

0.4 Will This Trike Win Races?

No. This trike is my first attempt at reverse engineering a trigonometrically complex steering geometry and, unless you figure out a way to make it in a home workshop, out of ultra-lightweight carbon-fibre tubing, plain, dirty old structural steel, in 1.6mm wall thickness, is going to be heavy. The frame, wheels, steering gear, gears, chain, brakes and seat will probably be closer to 20kg than 15.

Author's Aside: Was thinking about CF tubing as I was proofing this page the other day, and... Well, using 2 and 3mm walled tubing in various diameters and an Ender 3 3D printer (or better, but the E3 could do it), one could print lugs in PETG-CF that would mate tubes, thrust bearings, tilt brackets in 6001 or better (5m walls again) and you might be able to shave s few kilos off this beast. I doubt that'd give you a 10 year or 20 year trike, but it might win a race. If you're a gun builder and a gun rider. Or your CF may bust. But give it a go if you've got the money and the urge.

Author's second note: On a more practical point, 1.2mm might shave a kilogram off this frame, but you'll need to get your welds juuuusssst right. With 1.6mm tubing, the bare frame is approximately 6kg, using 1.2mm tubing for everything, will result in a 5kg frame. Not much saving off 20kg total machine weight? It might make the difference between completing or failing an "Everest", if you're into endurance riding, but it won't make a hill of beans on a commute, arun to the shops or a 20km "blat" about town. Compared to 15kg for an upright commuter bike with racks, the lower wind resistance of the trike is a bigger benefit than the weight saving of an upright. And I'm not even talking about adding aerodynamic fairings, yet.

0.5 What's The Catch?

Like I say at the top, you have to build this yourself. I'm not going to build it for you. Even if you live next door to me! That would be trampling on Kaze's patents. I plan to build one for me, and an electrified one for a disabled friend. If you can afford the real thing, buy it here at kazebikes. Please, buy theirs rather than build one, if you have the money. Nobody wins if they go out of business.

0.6 The Build Strategy

  • Draw basic design - done.
  • Acquire steel tubing and parts - mostly done.
  • Cut tubing to appropriate dimensions and shapes - partially done.
  • Work up the courage to start practicing my welding. This TIG tool I bought from Bunnings terrifies me and I maintain my own 3D printers!
  • Weld tubing to form spine frame.
  • Weld tubing to form crossmember.
  • Assemble crossmember, handlebars and spine frame.
  • Assemble steering arm and tie-rod assembly.
  • Build and fit wheels.
  • build and fit seat.

At this point, the beast will get "billy-kart" testing on the gentle, back street hills near my place. Old-shoe brakes. Just to check the geometries are working, get an idea of handling and how much lean gives how much steering.

  • Disassemble, weld on additional brackets and mounts, then paint.
  • Reassemble. (After the paint dries!)
  • Fit gears, brakes, seat and "upholstery" (made from play mats.)
  • Extensive testing and tuning of tie rod positions for best steering results.

0.7 Some Notes About Building a Trike Like This

Firstly, you will need a large, flat work surface. It can be a concrete slab, a steel welding bench, a thick piece of plywood (that IS actually flat) or anything similar. Most of the construction is simple, even if the cutting is complex in places. The "Jigs" folder in the repo will have OpenSCAD and/or STL files of supports, templates and marking guides. Nearly all of the assembly can take place on a truly flat surface, provided you clamp parts down and accurately pack spaces between the job and work surface. If you can do woodwork accurately and have some basic welding skills, this project will not be beyond you.

When welding parts together, file or sand ALL surfaces in and around where the weld will take place. Clean these bare metal parts with methylates spirits (denatured alcohol in the US?) and let it dry before applying flux (if brazing) or welding (if using a TIG welder.)

MEASURE TWICE AND CUT ONCE! It's the golden rule! Near enough is not good enough, especially for the steering parts. The slightest discrepancy between left side and right may result in an unridable machine to some degree, possibly even a dangerous one. Also, be sure of your welds! Be sure they've fused the welding pool and both parts of the join. If a weld fails, sharp edges and result and a sudden stop arising from a joint failure can seriously injure or kill in severe cases. If you haven't any welding experience, do a course and practice on scrap until you're confident you can do the job. "Take your time and you'll be fine," as the lead singer of Little Bo Bitch once sang.

Also, please reread the disclaimer, here, before you embark on any of this stuff, and note that, should you choose to proceed, all liability for your construction and operation of your project, falls squarely on you.