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 Post subject: 1979 and all that
PostPosted: Wed Nov 19, 2008 9:36 am 
MacRetro rider
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Let's get one thing out of the way; aerodynamics.

The problems associated with cutting through air only begin to come into play at above 12mph.
Above that speed and the effect is relatively small, but it increses exponentially. I thought about for how much of any one ride would I be travelling in excess of 12mph.
Even if I were out for an adrenalin hit, those periods didn't amount to much in time, mostly because I was travelling fast, it would be all over quite soon.
Then would come the decidedly below 12mph (vis climbing the next hill) period, which would take a long time. I also found that I would regret the speed that a downhill (especially a nadgery one) would pass, and I began to relish them more by travelling relatively slowly.
Therefore, aerodynamics play no part whatsoever in my design concepts, and I never waste any time at all worrying about it.

You are very perceptive to make reference to the standing position of trials riders, this is indeed a prerequiste of my designs. Just think about Graeme Obree's bike for a moment. He was quite able to get a racing tuck with his high handlebar up against his chest.
I realised early on that when riding off-road, one needs to be able to throw your body weight way forward, and way back, as well as from side to side.
If you're all stretched-out, there's no further to go, whereas if you're riding position is quite short, you have plenty of flexibility to manoeuvre.
A phrase kicked about a lot in the early days, and it is not without substance, is the concept of man and machine working as one entity. This is exemplified in the extreme in track racing, road racing etcetera, where the rider does not move very much in relation to their bicycle.
It could be considered a fundemental in traditional bicycle design and, in general, that concept runs through practically every bicycle produced, to some degree or another.
It is a concept I reject completely ~ the focus of my designs is to minimise this idea of rider and bike working together; as far as possible, the frame design and layout should allow both entities to work quite separately (but not completely, although that does happen from time to time), more like a co-operative relationship, if you take my meaning.

Now we come to your mention of the S word.
Stability.
This is influenced by three factors: Centre of mass and steering geometry, followed by weight bias for off-road bicycles.


And I've said enough for the time being, so I'm going to sign off.
I'll continue with the next exciting instalment of this thrilling tale discussing the part those three factors play in my designs.










Are you asleep yet?


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 Post subject: .
PostPosted: Wed Nov 19, 2008 10:06 am 
North Wales Deputy AEC
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I hadn't thought the point through that a stretched position gives the rider lesser ability to move around - it's funny then, that contemporary state-of-the-art cross country race machines have been in the roadie-like stretched position since the turn of the 1990s - it's only the advent of longer travelled full suspension and 'jump' bikes that have the riders in a sit-up-and-beg position (but significantly they're expecting to walk or be driven up the mountain). Perhaps that's the dominance of the road heritage or maybe marketing?? Perhaps it's time for those 'racing angles' to be challenged, as you say a la Obree?!

It occurs to my mind that the start of mountain biking as we know it, in my definition at least, is when the Klunkers of Marin (and others) turned their attentions to going across and up as well as coming down the Repack. So anyone looking to design and build such a capable machine wherever they were in the world was really pioneering the tools that we can trace the lineage to today - fascinating stuff!

Mr K


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 Post subject:
PostPosted: Wed Nov 19, 2008 11:31 am 
MacRetro rider
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The stretched position came about when Tom Ritchy built MTB's. Up until then Charlie and Gary had favoured high handlebars and a more upright riding position.
Then Tom Ritchy comes into the scene, and he is, of course, a roadie, hence the mountain bike got its stretched position.
I know I came under enormous pressure to make my designs more conventional i.e. rider and bike as one philosophy, which goes hand in hand with the stretched position.
I ploughed my own furrow.
I was tempted, but my twenty-odd-year journey told me not to. Maybe I would have got the help I was promised had I compromised.
It would be interesting to hear from CK as to the influences on them at the time the mountainbike went to the stretched-out position.
So ... the stretched position dates right back to 1979.

Then you bring in the topic of suspension ...
The stretched position philosphy is based on the notion that the weight bias should be neutral (this is closely linked to, but not to be confused with, centre of gravity and/or centre of mass), that is to say: equally between front and rear wheels.
Why? No-one actually seems to know, they say that it is 'conventional wisdom' ... that's how it's always been done, if it ain't broke, don't fix it, etc, etc, blah, blah, blah.
When CK, GF et al put high-rise bars on their clunkers, they were effectively moving the weight bias towards the rear wheel, by a certain amount ~ whether by accident, design or intuition, perhaps only one of them can tell us.
Anyway, my weight bias went right back.
Why? Well I suppose the first reason was that I noticed that I was often halted by even a small step on a slope, and I wasn't always in a position to haul the front-end up, so I wanted what I term a 'skippy front end'.
Horror amongst my cycling friends! You won't be able to steer, they said, the front wheel will keep jumping up, they said.
And they were right.
I'm a moderate fan of speedway. I've always been impressed by photos of the racers cornering, at speeds of about 30/40mph, with the front wheel clearly off the ground. My chum (the late) Simon Wigg used to say of his front wheel "it's just for parking and starting". This exaggerates the phenomenon; in reality the front wheel is playing a part in steering, but only a part.
Now, think of a Cleland bike more like a unicycle with incidental front wheel attached. Weight is all over the rear wheel, and as much of the steering is done with the rear wheel as with the front.
We tend to think that steering a bike is like steering a car.
Steering a bike is more to do with preventing your bicycle from falling over, more than anything else.
Think about taking a tight turn; you literally fall into the turn, and the role of the front wheel is to prevent you falling over completely.
The effect is that you take the turn, but you haven't steered round it; you've tried to fall over and then moderated the fall by turning the front wheel into the fall.
The front wheel does not need to stay in contact with the ground throughout the turn. If its light, you can skip it about a bit, dodge that rock, hop up a wee step, you know the sort of thing. If the bicycle is designed to accomplish this as a first principle of the design, then it does it a whole lot easier, and you are a whole lot less tired at the end of a day's riding.
If you move the weight bias from the front wheel to the rear wheel, the front wheel in less heavy and doesn't slam into (things) anywhere near so much. And thus you do not need suspension.
I think the primary reason and need for suspension is to do with the weight bias being placed neutrally.
It is ironic that the introduction of suspesion has brought about a rising of the front end and the consequent movement of the weight bias towards the rear. I notice that now, riders are replacing sus forks with rigids of the same length. Could this be because they are discovering what I've just described (at length)?
I remember, back in 1985 at the Small Dole event, thinking to myself:
"...I've been developing my designs for about twenty years now, but to all these people here, it is brand new; I can't expect them to understand. It'll take twenty years of their lives to get to where I am now..."
I had the advantage of having no influences, around me was a blank canvas, there were no off-road bike philosophies to confuse me. Nowadays, anyone trying to think clearly about these matters, is deluged with all kinds of dross, which has to be sifted through to find the gold; if there's any gold there, of course.






Sorry about that. Little questions often lead to big answers.
And I've tried to be brief!


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 Post subject:
PostPosted: Wed Nov 19, 2008 11:58 am 
South East AEC
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grat thread, sorry not to have anything to add. But I would like to get hold of a Evans MTB.


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 Post subject:
PostPosted: Wed Nov 19, 2008 2:25 pm 
retrobike rider
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Location: rutland
great read , keep it up :D

". It’s about time that someone started making them again, there must be a market for people who want to ride off-road in comfort, with a straight back and an unrestricted view of the countryside around them"

that sounds like pretty much everyone i pass while out for a ride :lol:

i come from a mid 90s bmx background where the bars were tall and wide and top tubes still relatively short so when i took up mountain biking it was still before people started jumping them and the stretched out cross country position so prevalent on this site was about all there was available but i never understood why the xc riders would sacrifice the ability to hop the bike well for a negligable aero advantage .

for what they gain on the singletrack they lose on the decents where they are hard on the brakes trying not to fall over the front :roll:

its funny how so much empathis was put on fitness but soo little on technical ability , they seemed to forget they had to actually ride the bikes over rough ground

my mtb has a chainstay of 16.75 and the bars are 39.5 from the ground , perfect


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 Post subject:
PostPosted: Wed Nov 19, 2008 3:55 pm 
King of the Skip Monkeys
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this isnt finished yet but I am going to use this to frighten Pickle & co on 30 November.

Drop bars obligatory BTW.

Lazy angles, highish front end - completely inspired by this thread and my own perverse drop bar fascination.


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 Post subject:
PostPosted: Wed Nov 19, 2008 4:36 pm 
Pumpy's Bear
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This makes really interesting reading Geoff and certainly makes me stop and think again on all those things I know to be true (in fact it looks like many of them are not based on sound principles at all).

Looking eagerly forward to the next installment.


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PostPosted: Wed Nov 19, 2008 8:49 pm 
retrobike rider
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First try the American way...

My first Mountain bike an FW Evans ATB ( i.e. Ritchey copy, with drops).

Photo taken Summer 1984 (near Southport).

Faster than a Cleland on-road but not off-road.


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Last edited by GrahamJohnWallace on Wed Nov 19, 2008 9:08 pm, edited 1 time in total.
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 Post subject:
PostPosted: Wed Nov 19, 2008 8:52 pm 
King of the Skip Monkeys
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:shock:

Good gravy - I've just built....


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PostPosted: Wed Nov 19, 2008 9:06 pm 
retrobike rider
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....Then the English way.

My Second Mountain Bike. (I kept this one)

1983 Cleland Aventura (Taken 8 June 1986 near Guildford).

Note the standing upright technique, ready to lift the front wheel over obstacles or holes. One flick of the pedals will create enough torque reaction to unweight or even lift the front wheel.

My favorite Cleland riding Technique is to ride standing upright on the pedals over large, low frequency, bumps. The riders body stays still due to its own inertia and the bike rotates around its bottom bracket, whilst the arms undertake a movement very similar to rowing.

Who needs suspension anyway?

BMX riders will know what I mean.


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