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 Post subject: Re: Wandering star
PostPosted: Wed Nov 26, 2008 5:10 pm 
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mrkawasaki wrote:
CK,

How was that route devised originally - or did you just make it up for the first one? Looks to be a tough one - how long does it take?

Mr K


It was a good long route that made a complete loop (20 miles, 3500 feet of climbing), which we discovered about the same time we started dragging one-speed bikes out there. (Now people are BACK to dragging one-speed bikes around it, but that's a different story.)

After the first ride, the route was chiseled in stone.

I believe the record for the loop is under two hours, by Joe Murray in a race, but I have been averaging four hours, because the nature of the ride is that you encounter all your cycling friends, and there are a number of traditional gathering spots.


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PostPosted: Wed Nov 26, 2008 8:49 pm 
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What surprises me is that - on the face of it - the geometry isn't so very far from my '92 Stumpjumper in many ways. The frame angles, wheelbase, and chainstay length are almost identical. The bottom bracket is higher, but the big difference is in the handlebar position. The Cleland's fork is longer, and the head tube is nearly twice as long. It's the handlebar position that's chiefly responsible for the weight shift up and back, not the frame angles.


It's important to remember that this bike has 650B wheels and 2inch tyres giving an overall wheel diameter of about 27.5 inches. For this wheel size, the wheelbase is short. You are correct in saying that the high handlebars are the key factor in moving the weight backwards. They are also the key factor in allowing BMX style, rapid shifts in body weight. Another key difference is the large wheel/frame clearances and lack of rim-brakes, which allow the bike to cope in the worst of muddy conditions.

For those not used to riding a Cleland, the high bottom-bracket and resulting inability to touch the ground whilst in the saddle, can be scary. However, the extra height is one of the delights of Cleland riding. You soon learn new ways to adapt and to dismount safely in an emergency. Cleland riders tend to be good at track stands, moving slowly over obstacles, and prefer to jump off, than fall off.

Hi Old Ned.The tubes came from David Wrath-Sharman's furtive imagination & garden shed. The choice of tubes is down to an analysis of the forces each should withstand. The forks, for instance, are intended to bend without damaging the frame. The Allen key removable freewheel is from the same source and is very straightforward. The treaded portion of the hub can simply be detached from the rest of the hub by undoing three Allen key bolts located on the inside of the hub flange. This is best done with a ratcheted Allen key.

The bottom bracket axle is also Allen key removable and adjustable and the cranks have self-extracting Allen key bolts. I believe that this was the last Cleland that David Wrath-Sharman ever made and its design is the culmination of 20 years of evolution from both Geoff Apps and David Wrath-Sharman. Of course, both were helped by all those who tested earlier bikes and components, to destruction in many cases.

The list of Geoff and David's innovations found on this bike is long. Many have since been taken up by the mainstream. Others have not. Some still remain unique and novel, 20 years after the bike was made.


Last edited by GrahamJohnWallace on Wed Nov 26, 2008 10:08 pm, edited 1 time in total.

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PostPosted: Wed Nov 26, 2008 9:50 pm 
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GrahamJohnWallace wrote:
It's important to remember that this bike has 650B wheels and 2inch tyres giving an overall wheel diameter of about 27.5 inches. For this wheel size, the wheelbase is short.

I do appreciate that the 650B rim is larger than the common 26" (559mm) mtb rim, but 559s are often used with tyres in the 2.3 to 2.5" range these days, giving a comparable overall diameter to a 650x50B. Even the 29"-wheeled Surly Karate Monkey has 17" chainstays and a 42.4" wheelbase in the 20" frame size.

In the historical context, the wheelbase was undoubtedly short. I'm just surprised to find that, contrary to first impressions, the Cleland's geometry has much in common with the more modern bikes with which I'm more familiar.


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PostPosted: Wed Nov 26, 2008 10:27 pm 
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one-eyed_jim wrote:
Quote:
Even the 29"-wheeled Surly Karate Monkey has 17" chainstays and a 42.4" wheelbase in the 20" frame size.


Eye Eye Jim.

Two things concern me regarding the "Surley":

1. the large leverage that high handebars could place on the stem and frame.

2. the frame clearances,"extendable up to 14mm". The Cleland has a minimum 38mm clearance between its mudguards and tyres. And a minimum of 13mm between tyre chainstays/forks and tyres.


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 Post subject:
PostPosted: Wed Nov 26, 2008 11:12 pm 
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Hello all ~ especially Ned & Graham ~

It is true that the Cleland is not remarkably dissimilar to present-day mountain bike frame designs. However, it was thought rediculous back in 1979 - 1985. The general trend in mountain bike frame design has been toward the Cleland and away from the Ritchy.

The characteristics of the Cleland design can be refined by some quite subtle distinctions in frame geometry, but these are not critical to the concept.

The Clelandale, for example, utilised a stock Beast of the East Frame with Project 2 forks. To gain tyre clearance (and to find out how they would perform) it was fitted with 37-590 Hakkapeliitta tyres on 18mm Sun Metal rims. I played around with mudguard fitting, and had a pair of those special 'limited edition' Sturmey Archer hubbies. The machine worked fine, considering the design compromises made.
It was definitely a Cleland design.

The Aventura II is a utilitarian beast, built as cheaply as possible from stock bought-in components, with a fair amount of work in PhotoShop with carefully taken photos of the various components, bringing them together in a multi-layered full-scale tif, and then checking dimensions, angles and fitting.
This is because another ethos of the design is that Cleland is not exotica; it's a down-to-earth practical and pragmatic design.

In my many years of research into bicycle design I have discovered one very important factor, which must be born in mind when designing a bicycle.
It is this: The human ability to ride a bicycle is very adaptable. This means that, within a certain range, there remains a high level of variability in the design of what can be ridden successfully. Well prepared and in the hands of a skilled rider, a bicycle of modest quality and conventional design can perform reasonably well. The ability to ride a particular design of bike successfully can also be determined by the amount of money parted with at point of purchase, and the extent to which the owner has extolled it virtues to his mates.

But that a bicycle performs well is as much to do with the rider as the bicycle itself. However, we must take into account the efficiency of the rider and bicycle relationship, and in this area, quite subtle differences can begin to pay dividends over an extended period of riding.

For example: Cable operated rim brakes require hand pressure to make them operate; the harder one pulls on the lever, the greater the braking effect.
Therefore, hand fatigue will be a factor after a ride of several hours. Hydraulically operated disc brake systems do not require hand pressure to make them work, they simply require the brake lever to be moved to a certain degree to achieved the required braking effect.
After one or two hours of riding, there will probably be no noticable difference between the two. But after three or four hours, and the cable-operated rim brake rider will be beginning to feel the effects on wrists and fingers. Five or six hours, and the difference will be significant.

Is this important? Does anyone care? Well probably not much. People spend their hard-earned money on the bike they choose, and ride it. It rode fine on the test ride, so there you are. How do we, as individuals, know how much pain and fatigue other riders are suffering? One rider may be very happy indeed to end a ride feeling like he or she has done several rounds with a boxing champion; another may find this detracts from the pleasure of riding.

These considerations of efficiency ~ how tired and/or damaged one feels at the end of a ride ~ are prerequisite factors I incorporate into any Cleland design. They are not at all obvious when looking at a photograph or drawing. In fact you can only become aware of them after several hours in the saddle; and only then if you know what it's like to ride another design of bicycle over an equivalent distance.

So, I'm getting tired now, and so may you, too; it's time to wind this little ramble up with a neat conclusion: The Cleland design is more a principle than a set of strict criteria ~ don't get too enmeshed in the minutia of angles and dimensions; provided the machine functions efficiently, or at least, more efficiently than anything else ~ and, by the way, if you haven't got it yet, the efficiency is not mechanical efficiency so much as rider efficiency ~ then it achieves its aim.

Coo, I still haven't done steering geometry and centre of gravity yet.
Hmmm, what have I got myself into?...


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 Post subject:
PostPosted: Wed Nov 26, 2008 11:21 pm 
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A quick one re Karate Monkey:

I was also a bit concerned about tweaking the geometry to avoid foot and front wheel contact and the fitting of suspension-corrected forks.
This does not sound like a well thought-out design, it sounds like they're just jigging about with a fairly successful frame design.

Refer to my last posting. Think about the variables ~ it's probably not a bad thing to jig about with a successful design.

Just don't be absolutely convinced they know what they're doing.
I'm not convinced.

That is not to say it isn't a good frame, and it may be so more by luck than judgement.


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PostPosted: Wed Nov 26, 2008 11:54 pm 
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GrahamJohnWallace wrote:
Two things concern me regarding the "Surley":

1. the large leverage that high handebars could place on the stem and frame.

2. the frame clearances,"extendable up to 14mm". The Cleland has a minimum 38mm clearance between its mudguards and tyres. And a minimum of 13mm between tyre chainstays/forks and tyres.

I'm not advocating the Surly frame as a basis for a Cleland-style bike - just using it as an example of a large-wheeled bike with a short rear end. The effective chainstay length can be increased by 14mm if tyre/derailleur clearance is a problem. I don't know what combinations of tyres and derailleurs cause problems, but digital shifting would be another solution...


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 Post subject:
PostPosted: Thu Nov 27, 2008 12:32 am 
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GeoffApps wrote:
The general trend in mountain bike frame design has been toward the Cleland and away from the Ritchey.

With respect, I think that's a considerable simplification. During the period that most of the readers of this forum seem to view as the heyday of mountain biking in Britain, there had been a shift from the clunker-derived bikes of the eighties with their slack angles and long wheelbases towards the lightweight race-derived machines of the early nineties. While the frame angles became more Cleland-like, the rider position and ethos shifted away from the rambler and toward the racer. Off-road cycling was marketed more as an adrenalin sport than a means of getting back to nature, and as suspension travel increased, more emphasis was placed on getting down hills as quickly as possible, rather than riding up or across them.

Downhill racing requires long-travel suspension, an upright riding position, slack angles and effective brakes, and weight isn't of great importance. It's only after having been refined in downhill sports that the more upright position, wide bar, high bottom bracket (to allow for suspension travel), and hub-mounted brakes have made their way, via "Freeride" bikes, and "All-Mountain" bikes, and what "serious" riders disparagingly call "play bikes" back to bikes that are used for riding out into the hills, up them and across them as well as down.

Quote:
The Cleland design is more a principle than a set of strict criteria ~ don't get too enmeshed in the minutia of angles and dimensions;

Understood, but it's always interesting to put numbers to things. When people with different backgrounds are trying to communicate it can promote understanding. I also ride Moultons, and a lot of my road-bike riding friends have been surprised to discover that what Dr M calls "narrow, high-pressure tyres" are (in some cases) 37mm wide and run at 60psi.

Quote:
Coo, I still haven't done steering geometry and centre of gravity yet.

And don't forget - how you came to source French-threaded hubs, and how this led to the demise of Cleland...


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 Post subject: I also ride Moultons
PostPosted: Thu Nov 27, 2008 1:47 am 
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Quote:
I also ride Moultons


:!: Snap :!: I've got a 1986 AM7, and a 1992 Pashley built APB. :roll: But don't get me started on suspension design. :roll:

With 38mm mudguard clearance, could I fit 29er wheels to my Highpath?

Not that I would want to lose all that dependable clearance.


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PostPosted: Thu Nov 27, 2008 7:22 am 
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Hello One-eye Jim ~

You're right on the mark; it is a considerable simplification, that's why I italicised the word general. I was actually referring only to frame angles, and no other aspect of the bicycle design, which I hoped I had clarified in the remainder of my posting.

Putting numbers to things is, as you say, a very useful tool for communication, and it is to be hoped that there always remains a balance between broader principles and intricate details.

We also have to keep in view the idea that much of what is said about bicycle design (including tyres, their width, diameter, pressure, materials and construction) is imperical ~ the stuff of myth and legend, perhaps. Very few people indeed, it seems, can untangle the the veneer of totems to find out what's really going on.

Even top scientists are still somewhat baffled by bicycle steering geometry, before introducing the variability brought about by suspension. I'm sure I know, but I don't have lots of letters after my name, so what is the use of knowing? Apart from designing, building and enjoying my own bikes, that is.

In short, my dear Jim, your perceptive postings are much appreciated.


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