Try refreshing the page to ensure you are enjoying the latest version. I tend to make endless edits and corrections over time. Forgive the sometimes off-topic nature of my blog these days. Walking and enjoying the countryside are vital to my physical and psychological fitness and sense of well-being. They combine to undo the damage caused by an occasional excess of cycling. And, may even stave off another rant! Though I can't promise anything. My long-suffering wife, "The Head Gardener," refers to me as the Imelda Marcos of saddles and saddlebags. She is usually right about almost everything. So it may well be true.


8 Mar 2010

Tadpoles?

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The Viktoria. A smaller version of the Viktor, which has its own chapter because it deserves it.

A tadpole trike is one which has two wheels forwards. I suppose the idea behind the name simulates the greater width at the head and a long, narrow tail. They do have certain advantages over the more common delta. (i.e.trikes with two rear wheels) The tadpole trike is much easier to push along by hand without falling over cumbersome back wheels. The rider can easily see the full width of the front wheels and thus has a better chance of avoiding obstacles in the road. Positioning the machine on the road to avoid the gutter or to follow a white line is much simpler. The rear wheels of a delta are usually invisible to the rider and their track can only be judged by long experience. Not so with the tadpole.

Theoretically the tadpole should be more stable on corners too. The tadpole trike tends to tilt backwards across a line between any two wheels. Rather than forwards like the delta. This can usually aid recovery from "overcooking" a sharp corner. The delta trike requires greater athleticism from the rider to keep all three wheels safely on the ground. Which is why you will see racing trike riders leaning right out over the inside rear wheel when cornering fast. Often with only the crook of a knee hanging over the saddle. Or even over the top bar to maintain contact with the trike at the limit of the rider's cornering ability. Much as racing motorcycle sidecar passengers perform their gymnastics to keep their weight over the inside wheel to stop it lifting in a bend. The tadpole also removes the danger of a tyre burn to the leg. Should one hang out too far on a sharp corner then there is a real danger of contact with the rapidly rotating rear tyres. In my  own case my neighbour's dog had to be fended off (rather vigorously) to avoid it closing its jaws on my leg. I caught the rear tyre on the inside of my knee and suffered quite a burn. (the road was dry)

All upright trikes have the disadvantage of having a very high centre of gravity when the rider is aboard. Though the invalid trike tends to be rather heavy low down to give some extra stability. The trike rider must adjust their own weight to keep the centre of gravity suitably placed relative to the machine. It is probably this which makes the trike so much fun to ride along twisting country lanes. A trike feels much faster at speed than a bike.

Here's a well designed, minimalist, invalid, tadpole trike with inclined kingpins, Ackerman steering and hub brakes. The T-bike. Low step through and clean design. I wonder how it handles on the corners at high speeds? It might be fun to find out. Though I'd worry a little about the lack of triangulation in the simple frame.

Here's the tadpole version of a Monarch pictured outside a superstore. I cannot explain the stump of plastic, drainage pipe, including the heavy joint. This addition must add dramatically to the weight and seems like total overkill. Particularly when a smaller and much lighter pipe would do just as well for holding a stick, crutches or umbrella. Note the capacious basket set low down to keep the machine's centre of gravity even lower when loaded. The twin front forks allow ordinary bike wheels to be utilised in this design. It should be remembered that bicycle wheels are not really designed for the sometimes-heavy, sideways loading of a trike. Yet they seem to survive well enough. The most obvious disadvantage of a tadpole is the greater weight at the front end. Making it much more difficult to bounce the machine up over a kerb when dismounted. Still quite a neat design with conventional small wheel bicycle rear end.

Here's a far more sophisticated tadpole carrier trike from Nihola. With Ackerman steering, front hub brakes and a very large front carrier box. It might be used for goods delivery or even carrying a small child.

A closer view of the complex steering gear. Probably not very lightweight but long lived and safe for being overbuilt. I have seen disk braked models like this and with alternative carrier boxes. I must see if I have an image stored somewhere.

This is a "Sutton Triped". A clever frame builder has turned a Dursley Pedersen replica into a totally unique, upright, tadpole trike. Ackerman steering and hub brakes.

Image borrowed from the Dursley Pedersen website "Sutton" replica chapter (with permission)

http://www.dursley-pedersen.net/replicas/sutton_triped.html

As mentioned earlier I once owned an original Dursley Pedersen and used it for commuting more than 30 miles each day. The "Triped" must be a lot of fun given the relative lack of freedom for the rider to shift his weight about on this rather tall machine. Nevertheless, the whole machine is beautifully conceived and manufactured. Well in keeping with the original Pedersen concept.

And now perhaps the ultimate in tadpole trikes. We caught up with this streamliner on a main road between two Danish cities. The owner was lying back in perfect comfort, pedalling effortlessly at a steady 30mph. (50kph) A glance across as we passed as slowly as we dared showed the machine had a rear electric hub. The number plate suggests that the machine is registered as an electrically driven motorcycle. Un-plated mopeds in Denmark are limited to 35kph. (22mph) Though there is a market for tuning parts which can lift speeds to 50mph (80kph) or more. My attempts to capture front and side views of this faired trike were thwarted by the "weeks long" shutter delay of my Canon Ixus camera!

And now a view of the car-less (careless?) society. We saw this streamliner going the other way in the centre of Odense near the hospital. A quick U-turn at the lights and we chased after him. Despite getting stuck at three more lots of traffic lights we finally caught up with him. He was being impeded by other cyclists who seemed totally unaware of his existence on the cycle path.That is the one serious disadvantage of a trike on the often-limited cycle path width designed for solo bikes.

The picture is taken at a very large junction with up to 6 traffic lanes, in each direction, crossing at right angles. The illusion of the lack of cars in this image is sheer luck. There were probably at least 50 cars waiting to get away. The small green traffic light is for cyclists (and pedestrians) only. They get a short period to cross before the motorised traffic is unleashed. The pedestrians at many junctions have right of way in Denmark and saunter across as if they had all the time in the world. I believe this is a case of conditioning as very small children. Where they must hold fast to their professional minder's pushchairs on their daily walks. If the Danes were to move en-masse to the UK it would be genocide. They wouldn't survive their first day crossing the road! Nor would Danish cyclists last five minutes taking their legal right of way at many junctions! 

BTW: My wife reported that the occupant of the streamliner was grinning from ear to ear. He made a sharp right turn onto a cycle path into the hospital grounds so may have been employed there. We cruised the vast hospital complex hoping for more photographs but by then he had vanished. My wife christened the machine "the banana" and made derogatory comments about the occupant probably being from the psychiatric department! This may have had something to do with the broad grin and the sight of rapidly reciprocating heels beneath the brightly coloured fairing. It may be that Danish law requires the occupant of this sophisticated machine to stick to the bicycle lane (when provided) regardless of his potential cruising speed. While the black machine above is registered as a road-going vehicle and thus has the relative freedom of the roads but may not even use the bicycle paths!

These faired trikes all remind me, all too much, of my attempts to build a downhill streamlined skatecar in my youth. I came up with a "brilliant" design for a rolled aluminium shell consisting of a sandwich of two thin skins of recycled, aluminium, printing sheets with glued wooden stringers. It was my pride and joy until I discovered I could not move my centre of gravity enough in the cramped cockpit to steer the damned thing! It even had rubber ball (in compression) suspension (a là Moulton) very wide trucks and 4" pink polyurethane wheels. I still have the bits in a box somewhere in the bike shed. The streamliner shell slowly disintegrated in the garden as overnight interest in the American skateboard craze waned just as rapidly. I was even making my own laminated, cutaway, birch ply, skateboard decks for a while but was in completely the wrong generation to succeed.

Let us hope that these pedal streamliners are just the beginning of something really exciting. Rather than a short-lived craze.

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