News and Events

Keep up to date with the latest news and events of Modular Bikes.

Sunday, February 26, 2012

Starting the Monsterbike Open Source Hpv Project

Monsterbike near Melbourne's Yarra River


This posting introduces the open source bike plans for my long wheelbase bike.  Without further adue, the plans are available in pdf form for free here. And here is the free dxf file of the plans.  Blog posts which could lead you horribly astray but containing a ramshackle description of my bike building process start here

Note that I have appied for some patents relating to this bike design.  At the moment I have no plans for commercialisation.

The plans which are now free were previously available as an online extra content when you bought my book.

I propose calling the bike Monsterbike.  Coincidentally, this gizmag report links to a video called "Monsterbike" and the machine is described as "Monsterbike, the modern day Penny Farthing".  My bike could be just that!  (See footnote.)

For about 6 years I've built and ridden bikes of this style around Melbourne.  The bikes have good load capacity and handling, are aerodynamic and quite fast.  Some videos showing the bikes in action are here, here, and here.

My own versions of the bike have included bikes with cloth fairings, wooden bikes, bikes with aluminium castings, and separable bikes.  But up to now my best success has been with a fairly simple chromoly steel construction.  I also have some aluminium beam frames on order!  While I firmly believe that the bikes are good, I don't have the time and resources and will to develop (say) versions of the bike in carbon fibre and aluminium lug construction, which could be slightly lighter than my current bike builds and really go much faster than the Sunday roady crew on Beach Road Melbourne.  But I'd love to see someone else build it!

I plan to expand the range of my plans available as open source and welcome your input on what would be a good forum for discussions on the topic of these bikes.

If you're keen and live near Melbourne you can borrow one of my bikes and learn how to ride it.

These are the general design principles for a Monsterbike. Not rules just guidlelines. 

* Front wheel drive, fixed botton bracket, recumbent bike with 700c, 26" or  24" front wheel and 20"rear wheel.  With a 700c wheel, the chainstays are parallel to the main frame as shown in the photo above, with a 26"  or 24" wheel, the chainstays are parallel to the ground as shown in the plan.  (This leads to a)
* Sloping main frame tube at about 20 degrees to the ground.  This geometry means that a hole for the steerer tube drilled at a simple right angle through the frame will provide the right geometry for bike stability using standard geometry bike forks. I can ride my bikes no hands but not while pedalling.
* The small back wheel allows a simple tailbox to be built onto the bike. (The rear wheel does not bisect the tailbox.) This tailbox adds visibility, storage capacity and aerodynamics to the bike.
* The seat height is about 600mm allowing for good visibility in traffic and easy stops and starts. 
* Direct front wheel drive, 8 speed derailleur gears with no pulleys guiding the chain

* The general ride quality relies on rear suspension.  Having a large front wheel with good inate suspension characteristics a long way from the rider means front suspension is not required.
* On some of the bikes like the one shown above I use an inertia braking system, turning the brake handles toward the rider, and allowing the natural forward motion of the rider during decelleration to help activate the brakes.  Also on the bike shown above there are 2 brakes on the front wheel - this simplifies the bike and also makes it easy to put a home made or other wheels disk on the back wheel.  No rim braking required on the back so the rims can be covered by a wheel disk without fuss.
*  These bikes work just like any fwd fixed bottom bracket design, that is, the chain comes from somewhere near the steering axis before it goes to the front wheel.  So when the steering twists, the chain twists too, but doesn't actually displace much.  Standard rear derailleurs mash up the chain in a horrible way during gearshifts, so this drive compromise doesn't worry the bike much. You can either have the chain quite close to the steering axis like some front wheel drive bikes with pulleys, or this bevo bike,8669 or limit the steering during pedalling in some way.  I have trouser guards or outside catcher rings on the chainring and limit the steering during pedalling by having my knees inside the steering bars and it all works.

Developements I'd like to see are versions
* with a main tube made from commercial carbon fibre tube stock and
* with standard 24 speed gears (I haven't developed front / top derailleur gear arrangements for the bike to date.

Thanks, Regards

Stephen Nurse

Footnote: My bike is rather big, so the name Monsterbike suits but equally important, the name begins with "MO".  It might be dumb pointing this out but the first two letters of my website name "Modularbikes" are Mo. Recently I came home with some stickers from a vintage bike market which were "Monarch". I promptly used them on my bike. Monarch is a rather stately and old world name for a bike but it did get me thinking that I could name all my bikes "something beginning with Mo".

No comments:

Post a Comment