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SteveArmstrong View Drop Down
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Direct Link To This Post Posted: 05 May 2011 at 9:05pm
You could have a look at Flevobikes. They have a pivot part way along the frame, which is slightly like your drawing, though perhaps a little further back than you have it. I've never ridden one, but I imagine they would take a bit of getting used to. Here's google images of some.

http://www.google.co.uk/search?hl=en&pq=%22flevobike&xhr=t&q=flevobike&cp=1&biw=1408&bih=657&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi
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Shiner View Drop Down
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Direct Link To This Post Posted: 05 May 2011 at 9:17pm
I think it would be better to have the front wheel tilt, rather then turn like a normal bike as theres no weight over the front end!
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Direct Link To This Post Posted: 05 May 2011 at 9:33pm
Flevos angle the central pivot so that the axis hits the ground just ahead of the front tyre contact patch, providing fairly conventional trail, but, because the pivot is angled so much, the front wheel does tilt as much as it steers.

This one looks like your sketch though Shiner: http://surfin_dude.tripod.com/cycling/python/Project_Python.html . I think Paul Lowing knows about these bikes.
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Shiner View Drop Down
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Direct Link To This Post Posted: 05 May 2011 at 9:58pm
nice one geoff I think I know where to put my crank now!
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Shiner View Drop Down
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Direct Link To This Post Posted: 05 May 2011 at 10:11pm
With tilt sterring tho...
 
Is it possible to pedal and steer with your feet at the same time???
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Shiner View Drop Down
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Direct Link To This Post Posted: 05 May 2011 at 11:53pm
How about this idea??
 
and link some steering underneeth??
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Adrian Setter View Drop Down
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Direct Link To This Post Posted: 06 May 2011 at 10:28am
 
Probably best not to worry about finishing it so nicely until you've learnt to ride it without falling off Wink
Challenge Hurricane - MicWic Delta (Front half) - Burrows Ratracer
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Direct Link To This Post Posted: 06 May 2011 at 11:27am
To Adrian, just checked out the link and have upset myself, my first project seems a bit lame by comparison. New to the movement, having picked up Mike Burrows' book at the library, I decided to have a go. Pictures to follow eventually...  Well done Shiner keep up the good work.
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Adrian Setter View Drop Down
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Direct Link To This Post Posted: 06 May 2011 at 1:01pm
This piece on Python steering geometry may be useful, if you haven't found it for yourself yet: http://www.python-lowracer.de/geometry.html
Challenge Hurricane - MicWic Delta (Front half) - Burrows Ratracer
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SteveArmstrong View Drop Down
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Direct Link To This Post Posted: 06 May 2011 at 3:01pm
If I'm reading your second diagram correctly, Shiner, the green pin only allows the front forks to pivot about the horizontal, front to back axis. As a result, when you try to turn, the front and back wheel will remain facing in the same direction as each other. The bike will not be facing the same direction any more, and the contact points of the tires on the road will not be on the same line any more but they will be parallel. I think what this means in practise is that the bike will drift off to the left or right in a straight line rather than turning, and will still be facing the same original direction you started in when you straighten the front wheel again.
The maximum turn for your buck comes about when the steering angle is 90 degrees i.e. the forks are completely vertical. As this angle decreases, the amount of turn decreases until its zero when the steering angle is zero. The first diagram on the python low racer link above shows that the forks and frame meet at an angle which allows it to turn.
I've drawn a diagram of this at the link below as I couldn't for the life of me manage to upload the images onto the forum!

http://recumbentbikes.webs.com/apps/photos/photo?photoid=125052620

Anyway, the hashed and solid blue lines respectively indicate the directions the front and back wheel will be facing when trying to turn. They are parallel, so the bike will move in that direction. The pink line shows the original direction of motion and the direction the bike will travel in again when the front wheel is straightened.


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