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The "Bullterrier" bike

 
 

It all started when...

The Bullterrier bike is my biggest and most ambitious private project to date. In 2008 i decided to build my own bike.

The main reason for this project was to show off my skills in design, hand modelling and carbon fiber crafting.

I had no experience in motorcycle building prior to this bike. In fact, i didn't even have a motorcycle drivers licence.

But i had been working on cars and other vehicles before, so (a bit naively) I thought that building a bike should be much easier than building a car. Little did i know.....

 
 

The start - a Fireblade

I decided to build my bike based on the mechanics of a modern Honda Fireblade. As I wasn't familiar with how the dynamics of a motorcycle work I decided to keep the geometry of the perfectly working Honda design intact.

I started working on my concept by making a series of drawings, but this proved a bit difficult for me. I simply lacked the experience of bike design. How should this look? Where can i place this? Why is this shaped like that?

In the end, I just kept an overall idea of how i want my bike to look, and in stead i concentrated on the first hands-on step of the project: making a chassis.

 
 

Carbon frame with integrated fuel tank and seat.

A frame mockup in the making. Notice the integrated fuel tank.

The chassis

I knew that the original geometry of the bike couldn't be improved by an amateur like me, so all the mounting points on the chassis were kept intact.

I decided to incorporate the fuel tank, the seat and eventually even the rear of the body into the chassis. I was warned by others that it would make the bike much harder to service and repair, but on the other hand, the load bearing surfaces would be much bigger and the loads would spread out more evenly. This would make the carbon fiber layup easier and less risky.

 

All the modifications were made by using the original chassis, tank and other bits. And a lot of putty...

Before I started cutting and modifying the chassis, a jig to fix the position of all the important mounting points was made

 

When the design war ready, the next step was to make molds for all the surfaces. I knew that i would have to make the chassis in separate bits and then bond them together. All in all, i had to hand laminate more than 20 separate mold parts for the chassis alone.

 

Doing this and then molding the parts took the bigger part of my Sundays for more than a year.

 

Inner part of the chassis being bonded to the aluminium fixing points.

Inner part of the chassis being bonded to the aluminium fixing points.

Here, only the inside of the swing core has been clad with carbon, but its already strong enough to hold the bike up.

Here, only the inside of the swing core has been clad with carbon, but its already strong enough to hold the bike up.


The body

This is really where the fun began, for me.

While working on the chassis, a more clear picture of how the rest of the bike should look got painted in my head. Rather than looking at the designs of other bikes, I wanted the bike to resemble an animal. More precisely a Bullterrier. Hence the name.

The breed is a front-heavy, muscular dog, with a tight waist and a lifted "bum", ready to charge. And of course the most characteristic part of a Bullterrier is the head and the nose. Very different from all other breeds. I wanted to translate all of this into a bike. I have always been interested in designs that challenge the eye of the observer, and i was aware that this design would be a love or hate situation for the viewer.

 

The entire body was shaped in professional modelling clay. Most of the edges seen on the body were fist cut in thin MDF plates and glued to the chassis, to define the shape and secure a sufficient symmetry.

Thereafter gigantic chunks of clay where placed and shaped. This process took me of course a very, very long time to complete, since i didn't have any exact drawings, and no deadline. This meant an almost infinite amount of small and large changes to the design, before i was satisfied. And naturally, it's hard to ever be satisfied with a design.

 

As you maybe have noticed already, the head of a Bullterrier is also visible in my logo at the top of the page.

 

The photos to the right show a different design of the side air outlets, that I eventually opted for, a re-shaping of the tank, and the final tank cover being fitted to the other parts.

 

 

 

Clay model of the body, modelled directly on the chassis.

At first, I wanted to make a cover for the original Honda swing, but decided to make a new swing instead.

Preassembly and fitting of the many body panels into two big ones.


The inside of the airbox..

The finished bike without the body panels, with me standing behind it. The short exhaust is visible here.

The carbon footrests, with fresh clearcoat, ready to be mounted.

The long walk towards the finish line.

I have to admit that when the body parts were molded, I felt like the bike was almost finished. But boy, was I wrong!

First of all, the rear swing didn't look good with the new, curvy body. It looked ancient. I tried to design a cover (as seen on the photo beside), but any design made the swing and the rest of the bike look extremely heavy. And i wanted to make the rear look light! The only solution was to scrap the original swing and make a new one. Naturally, this would change the behavior of the bike, as the original design is very complex and well thought through.

 

But i had to make this sacrifice. Today, I would definitively make a computer model of the swing and test it in a Finite Element Analysis program, but back then I just didn't have that possibility. This resulted in a carbon fiber rear swing that is actually about 800g heavier than the original, but the lesson learned and the design advantage weighs much more to me.

 

I am well acquainted with working in composite materials, so that was the most natural thing for me to use for all the remaining parts missing for the bike, like the footrests, airbox, headlight mounting, expansion chamber for the cooler liquid, and so on.

 

Finally, I also had to make a new exhaust that would fit under the bike and a new electrical wiring, that would move all the electronic boxes to a common place underneath the seat.

All this was new to me.

The single muffler underneath the bike was first build in thin DMF plates by me and then welded in stainless steel by an external company.

 

After all the bits and pieces were built and sourced, I wanted to paint the bike. By myself. Did I learn something from it? Yes, to let someone else do it next time. I'm happy with the result, but the amout of time it took me to achieve the result was crazy.

All the big parts of the body are painted in a turquoise-green-blue candy hue, that i blended after having seen this color on a painting.

All the other parts are just clear coated or polished. But all in all, all the carbon parts are visible, to prove their authenticity.

I actually consider painting parts of the bike in a solid color eventually.

Rear view of the carbon bike.

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