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PostPosted: Thu Jan 20, 2011 11:11 pm 
retrobike rider / Gold Trader
retrobike rider / Gold Trader

Joined: Mon Oct 15, 2007 9:05 pm
Posts: 9245
GeoffApps wrote:
I'm planning to come down to Thrunton in the not too distant.
When would be a good time?
That's if we were to meet, with a few chums?


Anytime really. I look forward to it.


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PostPosted: Thu Jan 20, 2011 11:26 pm 
MacRetro rider
MacRetro rider
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Joined: Mon Nov 10, 2008 10:39 pm
Posts: 170
Location: SE Scotland
Would a weekend be better?
Has the snow gone from up there yet?


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PostPosted: Fri Jan 21, 2011 7:13 am 
retrobike rider / Gold Trader
retrobike rider / Gold Trader

Joined: Mon Oct 15, 2007 9:05 pm
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There was still hardpacked snowice in places on the fireroads last weekend but and the trail up to the cairn still had deep drifts. The cheeky stuff through the trees was fine though.
Have a look in the NE&Yorks Nightrides Section for pics. We can organise a date over there and keep this one on topic if you like.

Si


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PostPosted: Fri Jan 21, 2011 7:50 am 
MacRetro rider
MacRetro rider
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Joined: Mon Nov 10, 2008 10:39 pm
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Location: SE Scotland
Okey-dokey.

Link?


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PostPosted: Fri Jan 21, 2011 7:55 am 
retrobike rider / Gold Trader
retrobike rider / Gold Trader

Joined: Mon Oct 15, 2007 9:05 pm
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http://www.retrobike.co.uk/forum/viewtopic.php?t=89630&start=180


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PostPosted: Wed Jan 26, 2011 1:06 am 
retrobike rider
retrobike rider
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Joined: Tue Sep 30, 2008 6:25 pm
Posts: 924
Location: Near Wendover Bucks
Here are some interesting facts about how a bicycle balances.

They are based on the idea of a balanced bicycle rolling quickly down a smooth hill.
A smooth undulation free surface is important as even small surface variations can overpower any self balancing gyroscopic effects of the rotating wheels. A freely rotating headset is also essential.

1/ A riderless bicycle with its steering locked in the straight ahead position will always fall over despite the gyroscopic effects of its wheels.

2/ A riderless bicycle with with a steering geometry that allows the gyroscopic forces to "self steer" will stay upright as long its wheels weigh enough and the bike is going fast enough.

3/ The same bicycle as in example 2 will fall over if it has a weight added that represents the mass of a rider. *

*This is because the gyroscopic forces are nowhere strong enough to overcome an unbalanced high center of gravity. However a fast bike with heavier wheels will take slightly longer to fall over than a slow light wheeled bike.

The problem is that the gyroscopic forces acting on the forks can have enough force to steer the forks and so balance the bike by steering it in the direction of a fall. But they can have nowhere enough force to hold the large mass of the rider upright on their own. Especially as this mass is far away from the forks. (The bicycle frame acts as a lever with the riders mass at the wrong end so that the gyroscopic forces will be reduced and not magnified. The lever's fulcrum is where the tyres contact the ground)

The idea that a child's bicycle will be easier to ride if ridden fast is true, but this would only relate to the gyroscopic effect of the wheels if the child rode "no handed".

This is because:

1/ The small wheels of a child's bike will generate less gyroscopic leverage than large wheels of the same mass.

2/ The slightest force applied at the handlebars would easily overcome the gyroscopic forces and so stop the bike from self steering.

The real reason why a child's bicycle will be easier to ride if ridden fast is because at speed only slight and smooth handlebar movements are required to keep the bike balanced. At low speeds much larger handlebar movements are required to bring the riders mass back into a balanced position. It's like tying to balance on the rolling deck of a ship. A slight smooth roll is easy to correct for, whilst a large erratic roll can easily make you overbalance.

Much of the above can be tested with a real bike and a large sack of potatoes. However both bike and potatoes may be damaged during the experiments.

Thus is the price of knowledge and truth!


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PostPosted: Fri Nov 30, 2012 5:43 pm 
Dirt Disciple
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Joined: Thu May 26, 2011 9:26 pm
Posts: 87
Location: Halesowen, West Midlands
xeo wrote:
I wonder what Andy Thompsons doing today ?


Did a degree in Health and Social Care and about to train as a CBT therapist. A new career in completely different field.


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