3d Cad Image of a Big at the Front (Click to see bigger Image) Pilot’s view on French Island The bike made with rapid prototype castings

Big at the Front!

For video of some of these bikes, click here. Thanks to Dave & Billy for doing the filming!

If you are new to recumbent bikes, you may wish to read Wikepedia’s reference on the subject before launching in to the rest of this page.

If a recumbent bike has two different wheel sizes, the big one will be at the back, right? Well, no ……. Starting with the Zeica a few years ago, I have been building front wheel drive bikes that have the big wheel (24, 26 or 27”) at the front and a 20” at the back. All have twisting-chain front wheel drive but the bikes developed over the last year dispense with the intermediate pulley (found on Zox bikes) and keep the standard-bike fork rake of about 70 degrees. This is in contrast to other new bikes such as the Minq which have direct front wheel drive but reverse trail. The layout ends up something like the long wheelbase Rans X-Stream but dispenses with the long chain, all the chain guides and the long control cables. The wheelbase is long and so are the bikes, and the new drive mechanism has some costs in terms of handling such as a reduced turning circle.

The first, experimental direct drive bike was built in late 2006 and started life as a six-speed, supermarket suspension bike and the frame ended up looking like this. Since then I have built several bikes layed out in the same way.

The first good bike of this type is now for sale. It has a cro-moly steel main boom and rotary–laser–cut end pieces which are the same front and back. They support the bottom bracket and steerer (front) and the rear suspension pivot and seat (back). This bike has completed 50-70k per day, twice weekly commutes, 100k training rides, this tour of French Island and the 210k “2007 Round the Bay in A Day”, all without fuss or serious mechanical problems.

While building this all-steel bike, I started to think about alternative ways of making it. First, a wooden one was made using laser-cut flats to secure parts to the frame. Later, I put a lot of work (actually I enjoy it!) into designing a casting that could do the same job as the rotary-laser-cut end pieces.

At work I deal with aluminium castings and am familiar with the rapid prototyping used to make samples of parts. After getting a quote for two-bikes worth of parts, I approached the diecasting firm Sankey Australia for sponsorship and soon after received funds that let me procede with the quote. Thanks to Andrew Mitchell and Sankey!

And now we have the result of the work with the castings. You can compare this with a 3d design drawing. The new bike takes some design cues from the wooden bike and has a 24” front wheel, a 20” rear wheel, 2 V-brakes on the front and no brake on the back. The lower part of the rear triangle is horizontal and “out of the wind”. All the control cables run through the steerer tube. The front and the back of the bike can be separated for transport. The suspended rear triangle folds under the bike and this is the simplest way to reduce the size of the bike.The bike is designed to have the identical frame castings used 4 times and to eliminate all other complex arrangements in the frame.

If the bike were produced in volume, the end result would be a fast, inexpensive recumbent cycle. The aim would be for a moderate price tag which would allow for good components and still make the bike less expensive than most other recumbent cycles.

I am interested in hearing from manufacturers interested in producing these bike designs and have taken provisional patent protection on the intellectual property. Within a few months I plan to publish details of some of the designs. Meanwhile I can supply individual requests for plans and parts at a price to be negotiated.

Note: The bikes were built with inspiration from the “Bevo” bike, but recently I discovered a “long lost relative” of this type of bike which is a bit more sporty than the Bevo. The bike is a custom built Rotator and it appears in the book “The recumbent bicycle” by Gunnar Fehlau. It was ridden by Matt Weaver to win a road race for unfaired bikes at Battle Mountain in America and can be seen online here in a photo by Arne Hodalic.

Regards

Stephen Nurse

steve(the at symbol)modularbikes.com.au

Phone Australia (03) 94818290 Fax (03) 9489 6669

10 Abbott Grove, Clifton Hill, Vic 3068, Australia