Danny MacAskill: see this and smile!

Paul

nice way to start the day!

https://www.youtube.com/watch?v=Z19zFlPah-o

TinyExplosions

See here...

Paul

TinyExplosions wrote: »

See here...

oops - missed that - thanks

Esroh

I wonder how many broken bones b4 he got that good????. See a Guy out and about around galway doing some crazy stuff on what I presume his commute(he always has a big backpack) now I see where his inspiration comes from

Vélo

TinyExplosions wrote: »

See here...

It's not fair, I can't see anything:(

Gavin

What's the story with the wheel. He's pedalling backwards at some points, but freewheeling in others. How does that work ?

niceonetom

Gavin wrote: »

What's the story with the wheel. He's pedalling backwards at some points, but freewheeling in others. How does that work ?

Normal freewheel. You have to pedal backwards when rolling backwards, but you can coast forwards. If you could coast backwards how would you be able to transfer power to the back wheel? Think about it.

Gavin

niceonetom wrote: »

Normal freewheel. You have to pedal backwards when rolling backwards, but you can coast forwards. If you could coast backwards how would you be able to transfer power to the back wheel? Think about it.

*brain explodes*

Good point, he's not actually generating backwards motion with the pedaling. Ta

Rusty Cogs 08

Gavin wrote: »

*brain explodes*

Good point, he's not actually generating backwards motion with the pedaling. Ta

Still unsure here, he seems to be driving the bike when pedalling both forwards and backwards but also has a freewheel hub. Is this physically possible or is he just 'spinning' the pedals backwards when in reverse as a kind of reflex action to moving backwards.

niceonetom

He's not powering the bike backwards when pedalling backwards, he's just keeping up with the wheel. If he pedals backwards faser than the wheel demands the extra revs are taken up by the freewheel, so he can't power backwards the way a fixed drivetrain can. If he pedals backwards slower than the wheel demands he stops.

This is like one of those mechanical reasoning aptitude tests, isn't it.

Rusty Cogs 08

niceonetom wrote: »

He's not powering the bike backwards when pedalling backwards, he's just keeping up with the wheel. If he pedals backwards faser than the wheel demands the extra revs are taken up by the freewheel, so he can't power backwards the way a fixed drivetrain can. If he pedals backwards slower than the wheel demands he stops.

This is like one of those mechanical reasoning aptitude tests, isn't it.

Now I'm really lost, I thought you either had a free wheel where you power the bike forward and are free to not pedal or pedal backwards as fast as you like (with no physical effects other than spinning your legs) or fixed wheel where you either pedal forwards or backwards with each revoloution being directly transmitted into the rear wheel.

If he's not powering the bike by pedaling backwards, why does he have to keep up with the wheel ? Does the wheel in reverse demand he pedals in reverse accordingly, but pedaling in reverse doesn't drive the wheel ? What then is the point of a set up where you 'must' pedal backwards when reversing if that action transmits no power ? However, if as you say, pedalling backwards more slowly than the wheel actually slows you down then I suppose that's a function (?)

niceonetom

Dude, you're so failing this aptitude test... :P

Rusty Cogs 08 wrote: »

Now I'm really lost, I thought you either had a free wheel where you power the bike forward and are free to not pedal or pedal backwards as fast as you like (with no physical effects other than spinning your legs) or fixed wheel where you either pedal forwards or backwards with each revoloution being directly transmitted into the rear wheel.

Yep, those are the options. He is using a perfectly normal freewheel.

Rusty Cogs 08 wrote: »

If he's not powering the bike by pedaling backwards, why does he have to keep up with the wheel ? Does the wheel in reverse demand he pedals in reverse accordingly, but pedaling in reverse doesn't drive the wheel ?

Exactamundo.

Rusty Cogs 08 wrote: »

What then is the point of a set up where you 'must' pedal backwards when reversing if that action transmits no power ?

This setup (again, just an ordinary freewheel) allows forward motion of the pedals to cause forward motion of the wheel. It makes you go.

If you could coast in both directions how would you go?

Mess with you bike. Spin the rear whell back wards with your hand. Observe the pedals "keep up" with the wheel. That's all he's doing.

petethedrummer

Rusty Cogs 08 wrote: »

Now I'm really lost, I thought you either had a free wheel where you power the bike forward and are free to not pedal or pedal backwards as fast as you like (with no physical effects other than spinning your legs) or fixed wheel where you either pedal forwards or backwards with each revoloution being directly transmitted into the rear wheel.

If he's not powering the bike by pedaling backwards, why does he have to keep up with the wheel ? Does the wheel in reverse demand he pedals in reverse accordingly, but pedaling in reverse doesn't drive the wheel ? What then is the point of a set up where you 'must' pedal backwards when reversing if that action transmits no power ? However, if as you say, pedalling backwards more slowly than the wheel actually slows you down then I suppose that's a function (?)

Push your bike backwards and watch the pedals.

Rusty Cogs 08

It's fair to say I don't do a lot of cycling backwards. I wasn't aware however that should I take it up I'll have to pedal backwards as well so as not to slow my velocity. I suppose the last point someone might clear up is if not pedalling backwards when moving backwards slows you down then does not pedalling forwards when moving forwards (say on a slight decline) slow you down ? and if not, why not ?

blorg

Rusty Cogs 08 wrote: »

It's fair to say I don't do a lot of cycling backwards. I wasn't aware however that should I take it up I'll have to pedal backwards as well so as not to slow my velocity. I suppose the last point someone might clear up is if not pedalling backwards when moving backwards slows you down then does not pedalling forwards when moving forwards (say on a slight decline) slow you down ? and if not, why not ?

As Tom and Pete say, wheel your (freewheel) bike backwards while watching the cranks. Try holding them still while you wheel your bike backwards. It will quickly become obvious

As regards your question the whole point of a freewheel is that it transmits motion only in one direction, so that is why it is different forwards/backwards.

I will admit when I first watched it, I thought it did look like he was actually powering the bike backwards and was a bit confused (as he was clearly freewheeling also.)

Rusty Cogs 08

blorg wrote: »

As Tom and Pete say, wheel your (freewheel) bike backwards while watching the cranks. Try holding them still while you wheel your bike backwards. It will quickly become obvious

As regards your question the whole point of a freewheel is that it transmits motion only in one direction, so that is why it is different forwards/backwards.

I will admit when I first watched it, I thought it did look like he was actually powering the bike backwards and was a bit confused (as he was clearly freewheeling also.)

So why does a freewheel hub also cause the cassette/rear cog (and thus the chain and the cranks) to turn backwards when in motion but not forwards, or if I take my feet off the pedals when freewheeling forwards will the hub turn the cassette, chain and cranks also ?

Lumen

Rusty Cogs 08 wrote: »

So why does a freewheel hub also cause the cassette/rear cog (and thus the chain and the cranks) to turn backwards when in motion but not forwards, or if I take my feet off the pedals when freewheeling forwards will the hub turn the cassette, chain and cranks also ?

Just think of your freewheel as a unidirectional fixie, where "direction" means relative rotation clockwise or anticlockwise compared to the rim.

Cassette clockwise = fixie.
Cassette anticlockwise = free.

When you push the pedals, the cassette rotates clockwise, your hub is fixed, the wheel turns clockwise, and you move forward.

When the bike is rolling backwards, the rim is moving anticlockwise, so your cassette is moving clockwise relatively, so it's still fixed, so the pedals turn.

And vice versa.

Rusty Cogs 08

Lumen wrote: »

When the bike is rolling backwards, the rim is moving anticlockwise, so your cassette is moving clockwise relatively, so it's still fixed, so the pedals turn.

quote]

the cassette is moving clockwise in relation to the anti-clockwise movement of the rim but (due to it's free wheel mechanism) is stationary in relation to the frame/you/world and thus the chain should remain stationary and also the cranks.

When the wheel/rim and exterior hub goes backwards it seems to turn the freewheel hub inner backwards too (and thus chain/cranks). This physical motion I can understand. It's the idea that if you kept the cranks level, and stopped the inner hub from turning although the rear wheel is turning (backwards) this some how causes a mechanical problem inside the hub.

petethedrummer

Rusty Cogs 08 wrote: »

So why does a freewheel hub also cause the cassette/rear cog (and thus the chain and the cranks) to turn backwards when in motion but not forwards, or if I take my feet off the pedals when freewheeling forwards will the hub turn the cassette, chain and cranks also ?

JUST PUSH YOUR BIKE BACKWARDS AND THEN PUSH IT FORWARDS.

niceonetom

petethedrummer wrote: »

JUST PUSH YOUR BIKE BACKWARDS AND THEN PUSH IT FORWARDS.

Good god yes. +100

No need for thought experiments here. Empiricism FTW!

Rusty Cogs 08

Hey, I can look at a plane flying in the sky, doesn't help me understand what keeps it up there. Sure what's life without a little mystery.

petethedrummer

A system of levers and pulleys.

blorg

@Rusty Cogs 08- agree you just need to push your bike forwards and backwards but if you don't have one to hand this very minute...

1. The freewheel can only be free in one direction, if it was free in both directions pedalling forwards would not propel the bike. (It uses a ratchet mechanism to achieve this.)

Think of the ratchet in the freehub:

ratchet pawl --][-- hub

Push pawl and you will push the hub around. Push hub in the opposite direction and you will push pawl.

2. You know from cycling the bike that you can stop moving the cranks and the rear wheel will continue to rotate clockwise and the bike will continue to go forwards.

3. Therefore, if you reverse the direction the bike is travelling, you reverse the rotation of the freewheel. Rotating the wheel backwards will cause the hub to rotate backwards, which will pull the chain, which pulls the cranks- backwards.

4. If you resist this motion with the cranks, you will stop the wheel.

Does this make sense It will be immediately obvious when you actually try it with a bike. I hope.

Lumen

blorg wrote: »

ratchet pawl --]

Ah, now that's much clearer.

Gavin

petethedrummer wrote: »

JUST PUSH YOUR BIKE BACKWARDS AND THEN PUSH IT FORWARDS.

Yeah ! And oil your cogs !!

sy

Gavin wrote: »

Yeah ! And oil your cogs !!

lol
This thread would make a great Monty Phyton scene

DirkVoodoo

It is pretty funny alright

kenmc

Actually many trials bikes are fitted with freewheel cranks rather than freewheel cogs on the back, apparently it centres the weight on the bike a bit more, making it easier to lift the back wheel.

niceonetom

kenmc wrote: »

Actually many trials bikes are fitted with freewheel cranks...

Oh ffs ken, why did you have to go and say that? There are obviously folks around here who are struggling with this as it is. WHere the freewheel makes no difference, but you try explaining that. See how you get on.

In summary I would like to point out that the dangle of the angle is inversely proportional to the initial vector if incidence thereby counterbalancing the flux capacitance of the chain slip. Obviously this hinges on the sub-bracket, pushing the pawl onto the inferior anterior cog clockwise...

Rusty Cogs 08

(checks bike) Turns out you were right all along, whooda thunk it ?

What I couldn't figure out in my head was the hubs one way locking mechanism in action, where the pedals push the wheel going forward, conversely the wheels push the pedals in reverse.

Thanks for the patience.

SetOverSet

That video had me grinning ear to ear but the rest of the thread has me ROFLMAO :D