The acronym HPV is applied to several things from the intriguing Hepatic Portal Vein to the unpleasant Human Papillomavirus, but here we are talking about Human Powered Vehicles.
HPVs are in the broad sense everything from ice-skates to a pedal powered airship but the term generally refers to pedal powered wheeled vehicles. It gets a little confusing here because the most common human powered vehicle, the bicycle, tends not to be classed as an HPV! This is mainly because of history, more of which later, and because there are hundreds of organisations of various forms devoted to the bicycle in the UK alone.
So the HPV is in general tends to be some form of recumbent, though beyond there generic descriptions don’t really work since unlike the bicycle there are almost as many variants as there are riders.
So where did this all come from?
Way back when in the latter part of the 19th century there were a huge range of bike designs with every man and his dog seemingly making something completely different to everyone else. This led to the Ordinary or Penny Farthing as the preferred mode of transportation at speed on the poorly surfaced roads of the time. The improvement in road surface along with the invention of the pneumatic tyre and the tendency of a crash on an Ordinary to result in the rider landing head first on the road led in 1885 to the Starley Safety bicycle, something that is pretty much identical to the modern bicycle.
OK, so the bicycle is an old design, what about HPVs?
As time went on, people started trying different ways to go faster and as they became aware of the advantages of streamlining this started to be incorporated
In 1912 Etienne Bunau-Varilla in France patented a streamlined enclosure for a bicycle and its rider and descendants of this bicycle set speed records in Europe from then until 1933. On 18th November 1933 in France, Marcel Berthet covered 31.06 miles (50 Km) in one hour - over 3 mph faster than anyone had travelled over this distance on a standard bicycle.
Earlier in 1933 Charles Mochet had built a supine recumbent (i.e. lying on his back) bicycle, with a streamlined body. François Faure used this to set a number of speed records between 1933 and 1938. They were never ratified by the world governing body of cycling, the Union Cycliste Internationale (UCI), which decided on 1 April 1934 to ban all bicycles except the diamond frame.
This refusal of the cycling authorities to accept superior technology, something that continues to this day, led to the HPV being ignored as something commercially viable and relegated it to the workshops of free thinkers.
You don’t really like the officialdom of cycling do you?
No, we have enough trouble with the laws of physics without making it harder for ourselves!
So what happened to make the HPV live again?
In the 1970s, a group of people in the US started playing with streamlined vehicles with a view to see how fast you can go by human power.
In 1974 Ronald Skarin, riding a streamlined bicycle designed by Chester Kyle, set 5 speed records in the USA. These were of course unofficial, but the US duo of Kyle and Jack Lambie decided to organise a race for unrestricted human powered vehicles, which took place on 5th April 1975. The winner achieved 44.5 mph. The HPV movement was born.
Since the 1970s the speed records have gone up drastically; the main two, the flying 200m and 1hour have both reached new heights in 2008 with Sam Whittingham riding the Varna Diablo 2 increasing his own flying 200m record to the incredible 82.33mph and Damjan Zabovnik riding Eivie II to set the hour record to the equally incredible 54.136 miles. When you compare Damjan’s distance with the current 30.882 miles as set on a conventional bike by Ondřej Sosenka or Chris Boardman’s ‘Ultimate’ record of 35.03 miles.
How on Earth do you do that?
This is where aerodynamics come in. As a simple guide, for the same drag, an aerodynamic section (roughly 4 times as long as it is wide) can have 10 times the frontal area as a cylindrical section, or in bike terms, a proper aero section fork blade would have the same drag as a single spoke. Alternatively an aerodynamic section big enough for a fairing, say 500mm wide, would have the same drag as a tube of 50mm diameter!
This isn’t the whole picture as well, the frontal area also has a direct effect on the drag. Because a recumbent typically has a lower frontal area than a conventional bike, it already has less drag before any kind of fairing has been added, with the added advantage of being a lot more comfortable than being in a full aero tuck on a conventional bike.
This is highly simplified, things are a lot more complex but it does show how yours truly can ride a faired recumbent for over an hour at 40mph when only three weeks previously I had struggled to ride my road bike at 22mph for 9 miles.
Never mind your 11 speed Campagnolo equipped road bike, HPVs have the real technical advances in bikes!