Ian Humphries (May 1999)
(Article first appeared in the Audax Australia, magazine Checkpoint ~ July 1999)
(Article is slightly updated as it appears here – updated November 1999)
A bit of history first:
My adult cycling really started in November 1990, after buying an MTB and touring down the west coast of the US.
That trip was fantastic and I was hooked. I bought a road bike a few months later.
I heard about the 1200km randonneur Paris-Brest-Paris in about 1993 or 4.
As an event, PBP sounded great, and I’ve been hoping to get there ever since…..
But, I’d heard about recumbents and before I’d even ridden one, it seemed sensible enough that I might actually enjoy riding 1200km just that little bit more if bits of me were just a bit more comfortable…..
I began investigating the world of recumbents first by talking to a well known frame builder, Wayne Kotzur, in Canberra.
I then found out about the Human Powered Vehicle Challenge held in Canberra every November and finally visited it.
I had a fantastic time trying out 30 or so different HPVs (they were all fairly easy to ride) and so I ordered one from Wayne a few months later.
It was a difficult wait for it and there was an amount of uncertainty about how it would turn out, with most of Wayne’s HPVs at that time being “one-offs”.
Of course I had my own design ideas which I had asked Wayne to incorporate, and that surely added to the uncertainty!
I rode and toured that recumbent for about 2 years, making a few modifications to it along the way, until it had evolved into a fine, very stable commuter and tourer, very suitable for long-distance cruising.
I was also interested in the design of other recumbents too, and was accumulating a file of many photos and sketches of different types of recumbents.
I ordered a CD-ROM which contained thousands of photos from European and US races and events
The urge to build a machine of my own design eventually overcoming my apprehension to do so, I borrowed a friend’s Oxy-acetylene brazing gear and after some practice, took 4 days off work and built a simple long wheel base (LWB) machine.
Over the next two months I completed my second recumbent, based only on two small photos I’d seen of two European racing HPVs.
I enjoyed immensely riding my “home brewed” bikes and raced the new machine at the HPV Challenge in Canberra in 1997.
It was definitely the fastest bike I’d ever ridden and the fastest bike there.
This led naturally into a personal quest (ha!) to design the perfect recumbent for Audax events and PBP!
So….. next I cut up the LWB, converting it to the short wheel base (SWB) bike I used in last years ‘Round the Bay and Alpine Classic rides (see photo).
It too was faster than my original commuter SWB and so the original was eventually offered for sale to fund further development!
The pictured bike is still is one of the most nicely balanced and handling recumbents I’ve ridden.
A few more ideas were tested out on the next SWB design, which was an old MTB “re-engineered”!
I built it as my commuting bike, so it could use big wide grippy tyres.
It is robust and indestructible.
It is as heavy as the original MTB was, but I used it in my 300, 400 and 600km qualifiers anyway, confident that it would survive if I did as it was way over-built!
(note here it was me who nearly didn’t survive the 600km – I used new shoes on that ride and one achilles tendon protested sufficiently to the point where I was almost pedalling with one leg).
I think my commuter is still as fast as a much lighter road bike however, making up for any distance lost uphill with superior flat-land and downhill speed.
It was very comfortable.
My commute times on it are faster than they ever were and I was and still am convinced that pedalling a recumbent rather than an upright is also significantly less fatiguing – only the legs need do any work – most of the body is relaxed!
I also find the view from a recumbent better too, with the neck relaxed the head is free to look around, and your focus is not limited to the few metres of bitumen in front of your front wheel!
As far as performance goes, after a few weeks of retraining, a rider of a recumbent should climb as fast as the equivalent weight road bike or MTB on very steep or long hills, and superior aerodynamics may even allow you to out-climb the upright bikes when the up slope is gentle.
(Not all recumbents are the same aerodynamically of course).
If the hill is short it is possible to power over it on a recumbent at speeds unachievable on an upright – pushing back on the seat-back allows lots more power to be delivered to the pedals than even an out-of-the-saddle-climber-on-an-upright can manage.
On downhills my recumbents can out-coast tandems.
Did I mention that recumbent riding is also FUN ? J
Anyway… the purpose of this article is to try to relate what I think is the perfect design of an Audax machine:
I think I have finalised the design of my perfect PBP two-wheeler now and bought some tubing a while ago (that I am still to put together).
It substitutes thin-walled cromoly for the mild steel I’d previously used and this should allow a weight only about one kilogram heavier than a comparably equipped road bike.
That should mean I should be quite a bit faster up hills than I have been and yet I’ll still have the aero-efficiency advantage elsewhere……
Here’s some clues to the design of my optimum PBP 2 wheeler:
- A wheelbase of approx 1135mm gives a good comfortable and predictable ride,
- a seat back angled at 25-35 degrees from the horizontal spreads the body weight out evenly and gives excellent aerodynamics and comfort
(my racer has a 20 degree seat and is more aero), - the crank axle is about 170mm above the seat base to minimise frontal area,
- the weight distribution when reclined on the bike should be 45% front / 55% rear,
- handlebars swept back from in front of and above the knees are comfortable to hold and the most aerodynamic, hands away from the steering plane,
- mesh seats are cooler and offer in-built suspension.
One of the most important aspects is the steering geometry and I have tested 55, 70 and 85mm of “trail”.
I have found a preference for lots of “trail” in the steering ie approx 85 (eighty-five) mm, either achieved through using a shallow head angle of 65 (sixty-five) degrees with 25mm of fork offset, or a 70 degree head angle and no fork offset.
The trail figures are for a front 37-406mm tyre-wheel, commonly known as a 20×1.5 inch (bmx).
Lots of trail means that it will ride in a straight line with little attention and also be more stable in gravel and sandy sections of road.
BTW fast, narrow, slick tread tyres are now available with ratings of up to 120psi in the 406mm size!
The only bug in my building schedule prior to PBP was that I developed an affection for trikes, after reviewing several, and will ride a new special lightweight Audax model Greenspeed in the next few weeks.
The trike format perhaps providing the safest and most stable ride in those hours when the eyes are bleary and exhaustion is overwhelming?
A lightweight recumbent trike maybe the ultimate PBP HPV, making sleep possible wherever you stop!
The trike’s only disadvantage may be its additional kilogram or so.
My final comments must be that I still wonder why more recumbents aren’t used in Audax events.
I’ve seen very expensive machines on rides I’ve done – bikes that easily exceed the cost of a (probably faster) lightweight, custom built recumbent…..
I guess I’ll give up reasoning why though and just ask my crotch, wrist, hands, neck and back if being a bit different is worth it!