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PostPosted: Mon Nov 24, 2008 10:09 am 
MacRetro rider
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Location: SE Scotland
One-eye Jim: Hi ~
Yep, digital shifting means using your fingers.
Because I have a hub gear I can back-pedal with my left leg and nudge the chain from the larger ring to the smaller with the side of my foot. I ride in wellies (rather good, flexible and lightweight ones ~ more details if requested) so I don't mess up an expensive pair of over-priced and over-hyped cycling shoes.
That's for a down-shift; for an upshift I have to stop the bike and lean it against something (unfortunately) and, again back-pedalling with one hand, pull the chain onto the larger ring. Doesn't take long really; about a half-turn does it.
Moreover, since I can use the full range of gears in either ring, I only shift when necessary; if the going becomes decidedly moderate, or decidedly extreme.

Swizz69: Hi ~

How did you know I used to ride a Montesa Cota, or was it a guess? That was back in 1972!

EdEdwards: Hi ~

That is a MAVIC mech dating back to 1997/8. You are probably familiar with the fact that it came completely to pieces, every part beautifully manufactured from alloy and stainless.
I needed a chain-tensioner to cope with the difference between the two EggRings, but I was not quite sure where the chain-line would be, so this modified mechanism, sans bits for shifting, made an excellent adjustable tensioner; once adjusted it could be left alone.

I have been working on some illustrations for my article on steering geometry and centre of gravity articles, so sorry for the delay.


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PostPosted: Mon Nov 24, 2008 12:30 pm 
King of the Skip Monkeys
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Hi Geoff

Love the fact that you were ploughing your own field while the industry tottered off on its own but I can see that you were creating a rod for your own back.

Shifting by hand - thats instant derision time - surely if you wanted to be taken seriously, you would have adapted a front changer mechanism to suit. Shimano Biopace in its extreme ovalness had shifters at the front. You could have made a parallelogram mechansim and two plates to move a chain up and down without stopping.

Even the early Saracens and F W Evans MTBs would have had nice tidy shifting via the cockpit

Re over hyped cycling shoes - only having used 3 pairs in 16 years, the thought of a wellie filling up with water does not fill me with confidence... :wink: .

The Ging design of chain tensioner has a pivot which swivels with the chain line allowing 3 rings at the front.

Now I have visions of this lone bearded chap out on the trails, the sound of sloshing wellies and greasy hands from ring changes....
:wink:

:D :D


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PostPosted: Mon Nov 24, 2008 3:16 pm 
East Midlands AEC
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I don't know - there's something to be said for digital shifting - I use it on my dual speed Dave Yates :wink:


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PostPosted: Mon Nov 24, 2008 3:51 pm 
MacRetro rider
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Hello Big Cheese ~

Thanks for your response.

The digital shifting feature on my current Aventura was never a typical feature of the Cleland design in general. They all had conventional front mechanisms.

The digital shifting is there because I had difficulty fitting a shifting mechanism in combination with my chosen chainguard design for this bike.
My long-term plan is to incorporate a mechanism of some description. However, since this is a prototype and still being developed, and I do not find it a great inconvenience, it stays as it is for the time being. As to greasy hands, that has been sorted with a little hook that clips onto the frame.

You are so right when you point out that a whole well-thought-out design and construction can be derided for one tiny inconsequential factor.

The ovality of the Biopace system was not actually very extreme, it was almost round when you compare it with the EggRings in the photo on the previous page. Additionally, of course, the major/minor axis where 90degrees out, ie back to front.

I chose to modify the Mavic mechanism for seven reasons
- I already had it in my box of reusable items
- it is too good to waste
- it is beautifully engineered
- it did not cost me anything
- I enjoy modifying and recycling items like this
- it gave me the chance to check and adjust for the chainline
- I didn't want a swivelling guide because I have only two rings
If this bike were ever produced in numbers, a production or OTS tensioner would be utilised.

On my regular off-road circuit I have stream crossings and huge pools of water to negotiate. The depth is up to 18" with rocks under the surface. I am yet to experience water-filled boots. I am a little perplexed as to why you think they would fill up with water. My current pair are nine years old and I expect them to last at least another nine.

Lone chap out on the trails, you're right! the population is so dispersed around here that I don't know of anyone else in this area who enjoys pootling along tracks. Further west there are many more.

As to the other aspects of your visions, well, they don't tally at all.

Och, I'm awah the noo . . .


Last edited by GeoffApps on Mon Nov 24, 2008 6:57 pm, edited 3 times in total.

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PostPosted: Mon Nov 24, 2008 4:07 pm 
King of the Skip Monkeys
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Location: Moomin Valley
:lol: :lol: :lol:


I did a bit of water riding during the '98 floods in East Anglia - the water came above the handlebars... It was a bit alarming and bloody cold but fun. Got some good photos.

Happy trails.


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PostPosted: Mon Nov 24, 2008 4:47 pm 
Dirt Disciple

Joined: Mon Nov 17, 2008 5:54 pm
Posts: 19
Location: Hyde, Cheshire
Quote:
How did you know I used to ride a Montesa Cota, or was it a guess? That was back in 1972!

LOL not a bad guess eh? I remembered an old book in the school library about motorbikes - the Cota getting a good mention.

Regarding front shifting - aren't there a few options now for epicyclic gears in the cranks? Schlumf Mountain drive rings a bell & short term memory fails but am sure Shimano or Sram are offering one too, though whether they are up to trial use is another matter I suppose.

Have you seen Surly's 29er the 'Karate Monkey' as a suitable frameset?


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PostPosted: Mon Nov 24, 2008 5:04 pm 
Retro Guru
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Joined: Mon Oct 17, 2005 4:40 am
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Location: California
Regarding non-round chainrings. Early in my MTB experimentation I mounted an oval chainring from Durham as the inside of two chainrings.

The shifter moved the chain easily from round to oval, but you got used to one or the other, and switching always put you back into the funny feeling gear, whichever it was.

I never had any problem with Biopace until my RPM went up, but they didn't make them in the 52-tooth range, so anything over 20 mph required a high-speed spin. At 110 RPM your pedaling became impossible jerky.


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PostPosted: Mon Nov 24, 2008 6:49 pm 
MacRetro rider
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Joined: Mon Nov 10, 2008 10:39 pm
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Location: SE Scotland
Swizz ~

Schlumf is a fine bit of kit, but you can't run EggRings with it.

So, for me, it's one or the other.

EggRings win (hands down, actually)

Can you point me in the direction of an image of the Surly 29er you mention?

Cheers ~ Geoff


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PostPosted: Mon Nov 24, 2008 6:54 pm 
East Midlands AEC
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Location: Derby, UK
http://www.surlybikes.com/karatemonkey.html


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PostPosted: Mon Nov 24, 2008 7:10 pm 
MacRetro rider
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Joined: Mon Nov 10, 2008 10:39 pm
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Location: SE Scotland
Swizz ~

Surly Karate Monkey.
Hmmm, on a quick look it would make a very good Cleland, except, perhaps for the BB drop.
Thanks, that link is on my favourites for when the lottery comes up.

Cheers ~ Geoff


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