Theory

“If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.”

-- George Bernard Shaw

Here you will find a brain dump of all that I know about human powered vehicles, with a particular focus on tilting recumbent trikes. I plan to write at least one article every two weeks, covering all the research I have done in this area. The empty headings below provide clues as to what's coming.

My hope is that these articles will help new home builders avoid making those really big mistakes, the ones that only seem obvious in hindsight. Rather than be prescriptive, I want to delve into some of the detail, so that if you choose to venture off into uncharted territory, you can still adapt some of the fundamental principals to your designs.

I have found that sharing what I know with others stimulates debate and fosters learning opportunities through knowledge exchange. So please join the Jetalk Mailing List and ask the questions that haven't been asked or answered here.

Fundamentals

---

Why Ride a Trike?

You might think comfort, performance, safety, carrying capacity or low speed stability, but my reason was a common medical condition that prevented me from riding my regular mountain bike. It was either give up cycling, or find something completely different to ride.

Why Does Tilting Matter?

When you get a trike with low seat and 900mm track out on the road, you quickly realize just how much wider and lower to the ground than a bike it is. If you want a narrow track trike with a high seat, the only way to make it stable is to make it lean.

Tadpole or Delta?

The tadpole trike has the two wheels at the front, the delta trike has the two wheels at the rear. Is one configuration better than the other?

FWD or RWD?

One of the many issues to consider when designing a recumbent, is whether to make it front or rear wheel drive (FWD or RWD). The choice is not clear cut, each approach has its strengths and weeknesses, and like all good design, you have to find the best solution fit for your specific requirements.

FWS or RWS?

As a first time builder, you will no doubt be considering all possible permutations for your trikes design. This will inevitably lead to questions about rear wheel steer (RWS) -- Does it work?

What Causes Shimmy?

 

Geometry

---

How Does Jetrike Work?

The Jetrike self centering effect works because the tilt geometry ensures that the outside wheel moves down further than the inside wheel moves up. This raises the seat height as it tilts, providing a small centering force.

Ergonomic Recumbent Design

This 12 step process starts with the individual dimensions of the rider, seated comfortably in a reclined position, then the bottom bracket and handle bars are placed where they should be, from there informed choices are made about the appropriate wheelbase and head tube angle based on the desired seat height and backrest angle.

Trail

When I started this project, I made the serious mistake of using someone else's recommended pivot angle and trail settings without understanding that differences in wheel size matter. So on this page you will find my survey of trail ratios and pivot angles and a trail calculator.

Caster, Camber and Toe

Tracking

Tilting Strategies

Wheel Size Selection

Breaking Forces

Suspension Strategies

Free to Castor

 

Materials

---

Steel, Aluminum or Carbon?

Tube or Box Sections?

Welding Techniques

 

Fabrication

---

Space Frame or Mono Tube?

Gussets and Stays

Bushes or Bearings?

Chainring Adapter

I used a solid BMX chainring to construct a BCD 135 to 110 adapter.

Inside...