Can someone please resolve a dispute....

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Can someone please resolve a dispute....

Postby Cluey » Mon Feb 19, 2007 6:42 pm

I got two people having a little disagreement about....

1 says...

If someone slips in behind you whilst pedalling not only does the follower 'slip stream' and therefore get an easier ride, but the rider in front does it a bit harder as they are 'carrying' the second rider...

2 says...

the second person just gets the slip stream benefit, the front rider experiences no difference in speed / effort / weight or whatever.

:P
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by BNA » Mon Feb 19, 2007 6:52 pm

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Postby gururug » Mon Feb 19, 2007 6:52 pm

No disadvantage for front rider (they do it tougher because they are not behind someone else)
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Postby AUbicycles » Mon Feb 19, 2007 7:01 pm

The negative effect for the rider in front (in terms of being slowed down from a rider in the slipstream) is absolutely marginal ie. non existent. The rider in front is simply breaking the air and allowing for less wind resistance.

For larger vehicles, the effect of drag may be noticeable.
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Postby sogood » Mon Feb 19, 2007 7:50 pm

By all physical reasons, it makes zero difference to the rider in front. The only scenario where things might change is if the two riders are riding so fast around Earth that they are drafting off their own slip-stream. This scenario unfortunately has no bearing in reality as,

1) There's no single straight road that circles the planet.

2) The first rider couldn't even come close to Chris Hoy in terms of speed.

3) The first rider will burn up in a more spectacular fashion than Columbia over TX at that proposed speed.
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Postby europa » Mon Feb 19, 2007 8:38 pm

This probably comes from car and motorcycle racing where the change to the front rider's airstream (admitedly behind him) is enough to slow him down. Grand Prix bike riders have described it as being like having someone hanging onto their shoulders.

On pushbikes, it's unlikely to be an issue (due to the lower speeds) and I've never heard a pro bike rider talk about it.

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Postby mikesbytes » Mon Feb 19, 2007 9:45 pm

The only issue is that you in front have done more work than you behind. It doesn't affect the front rider having someone behind.

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Re: Can someone please resolve a dispute....

Postby tuco » Mon Feb 19, 2007 9:49 pm

Cluey wrote:I got two people having a little disagreement about....

1 says...

If someone slips in behind you whilst pedalling not only does the follower 'slip stream' and therefore get an easier ride, but the rider in front does it a bit harder as they are 'carrying' the second rider...

2 says...

the second person just gets the slip stream benefit, the front rider experiences no difference in speed / effort / weight or whatever.

:P


Actually it's number 3.
The front rider does get a slight advantage. I was only reading about it yesterday. Something to do with the difference in air pressure behind the front rider when a rider is behind them. I didn't pay too much attention to the article as it wasn't what I was looking for so I just skimmed over it.
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Postby Bnej » Mon Feb 19, 2007 10:04 pm

There's drag as you push the air out of the way.

And there's drag as the vacuum behind you tries to suck you backwards.

Having someone directly behind you, I think, means that they are pulling the vacuum, while you are pushing the air to the sides and creating it. The front person does more work, but the net aerodynamic efficiency could improve for both.
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Postby tuco » Mon Feb 19, 2007 10:07 pm

Found the page again :

In order to benefit from drafting, you've got to be in the drafting bubble behind the cyclist immediately in front of you. And in a crosswind the bubble will NOT be directly behind the rider in front but will be some angle away from them. The effectiveness of this bubble decreases with the distance, being the greatest if you draft closely and falling off until there is minimal benefit at 5 or 6 feet. The important fact is that you will get some benefit 3, or even 4 feet, back - and it’s a lot safer than being directly on the rear wheel of the rider in front of you.

The rider being drafted also gains a slight advantage. This is explained by the fact that the low pressure behind the lead rider is increased in a pace line, giving the leader a slight "nudge" due to the pressure differential between the high pressure ahead and the low pressure behind. This is why a NASCAR racing car will go 1-2 mph faster when being drafted.


http://www.cptips.com/energy.htm
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Postby pospete » Wed Feb 21, 2007 2:33 pm

[quote="Bnej"]There's drag as you push the air out of the way.

And there's drag as the vacuum behind you tries to suck you backwards.






Definatly cycling in Drag is best avoided, fishnets never look good on any bloke, and stilletoes were never designed for pedals either. I'll not even mention sucking anything whilst riding, it has just got to be dangerous :lol:
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Postby heavymetal » Wed Feb 21, 2007 4:07 pm

I went out and tested this theory and he are my findings. I couldn't find anyone to ride with me :shock: , so I hooked the BOB trailer up behind me with a load.

I found there wasn't much difference on the flat, but going up hill there was a noticable drag. Going downhill was another matter though, I could definately feel the benefit of having the BOB trailer behind me :D


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Postby tuco » Wed Feb 21, 2007 4:16 pm

More proof number 3 is right :

Drafting

Drafting is an important technique in road racing. Exploratorium Senior Scientist Paul Doherty explained, "The bicyclist, as he moves through the air, produces a turbulent wake behind himself. It makes vortices. The vortices actually make a low pressure area behind the bicyclist and an area of wind that moves along with the bicyclist. If you're a following a bicyclist and can move into the wind behind the front bicyclist, you can gain an advantage. The low pressure moves you forward and the eddies push you forward."

Suprisingly drafting not only helps the bicyclist following the leader, but the lead cyclist gains an advantage as well. Paul explained, "The interesting thing is by filling in her eddy you improve the front person's performance as well. So two people who are drafting can put out less energy than two individuals (who are not drafting) would covering the same distance in the same time." While the lead cyclist gains some advantage in this situation she still needs to expend much more energy than the cyclist who is following.

http://www.exploritorium.com/cycling/aerodynamics2.html
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Postby Mr888 » Wed Feb 21, 2007 6:03 pm

hmm, interesting comments, but what happens if there is a significant tail wind?

Do both the front and rear riders benifit from the tail wind or only the rear rider? Does it mean that the rear rider is breaking the wind push to the front rider?

If it's only benifiting the rear rider, then the front rider not only has to work twice as hard breaking the wind (excuse the pun) in front but also without the advantage of a helping tailwind that the rear rider is enjoying.

Therefore point 1 is correct...no????? :?
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Postby mikesbytes » Wed Feb 21, 2007 6:37 pm

Your assuming that the tail wind is actually stonger than the actual speed of the bikes, so if the bikes are doing 40kph, then the tail wind is stonger than 40kph. More likely the wind resistance has been reduced, A 20kph tail wind means that you are only pushing into the equivilant wind of 20kph when you are actually doing 40kph.

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Postby LuckyPierre » Wed Feb 21, 2007 7:11 pm

Mr888 wrote: Does it mean that the rear rider is breaking the wind push to the front rider?

I've heard of lots of things, but no-one's even mentioned that breaking wind will help the rider in front of me! :wink:
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Postby pospete » Wed Feb 21, 2007 8:05 pm

LuckyPierre wrote:
Mr888 wrote: Does it mean that the rear rider is breaking the wind push to the front rider?

I've heard of lots of things, but no-one's even mentioned that breaking wind will help the rider in front of me! :wink:




it would probably cause a stack up behind you tho! :lol:
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Postby Mr888 » Thu Feb 22, 2007 9:52 pm

mikesbytes wrote:Your assuming that the tail wind is actually stonger than the actual speed of the bikes, so if the bikes are doing 40kph, then the tail wind is stonger than 40kph. More likely the wind resistance has been reduced, A 20kph tail wind means that you are only pushing into the equivilant wind of 20kph when you are actually doing 40kph.


But what happens when there's someone blocking that tail wind from behind? Wouldn't the front rider more or less still be pushing 40km/h? Does this mean that the rear rider is pushing less (due to drafting) but at the same time getting an extra 20km/h from the tail wind as well?...does anyone have a degree in physics here?
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Postby Mr888 » Thu Feb 22, 2007 9:54 pm

LuckyPierre wrote:
Mr888 wrote: Does it mean that the rear rider is breaking the wind push to the front rider?

I've heard of lots of things, but no-one's even mentioned that breaking wind will help the rider in front of me! :wink:


Best way to break wind is to stock up on some baked beans! :lol: :lol: :lol:
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Postby mikesbytes » Thu Feb 22, 2007 9:59 pm

Mr888 wrote:
mikesbytes wrote:Your assuming that the tail wind is actually stonger than the actual speed of the bikes, so if the bikes are doing 40kph, then the tail wind is stonger than 40kph. More likely the wind resistance has been reduced, A 20kph tail wind means that you are only pushing into the equivilant wind of 20kph when you are actually doing 40kph.


But what happens when there's someone blocking that tail wind from behind? Wouldn't the front rider more or less still be pushing 40km/h? Does this mean that the rear rider is pushing less (due to drafting) but at the same time getting an extra 20km/h from the tail wind as well?...does anyone have a degree in physics here?


I think you missed the point. At 40kmh relative to the rider, a 15kmh tail wind is actually a 25kmh head wind, so the rider behind is not blocking that wind. The rider behind would be blocking the wind if you were riding at 10kmh with a 15kmh tail wind.

BUT consider that at 40kmh in still air, that 80% of resistance is wind, then it is pretty unlikely that you will be riding slower than the tail wind.

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Postby Mulger bill » Thu Feb 22, 2007 9:59 pm

Mr888 wrote:
mikesbytes wrote:Your assuming that the tail wind is actually stonger than the actual speed of the bikes, so if the bikes are doing 40kph, then the tail wind is stonger than 40kph. More likely the wind resistance has been reduced, A 20kph tail wind means that you are only pushing into the equivilant wind of 20kph when you are actually doing 40kph.


But what happens when there's someone blocking that tail wind from behind? Wouldn't the front rider more or less still be pushing 40km/h? Does this mean that the rear rider is pushing less (due to drafting) but at the same time getting an extra 20km/h from the tail wind as well?...does anyone have a degree in physics here?


Only HS sorry, and that was a while back.
Isn't every rider pushing a bubble of air in front of him? Would No2s bubble be pushing the leader?
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Postby pospete » Thu Feb 22, 2007 10:09 pm

[quote="Mulger bill"
Only HS sorry, and that was a while back.
Isn't every rider pushing a bubble of air in front of him? Would No2s bubble be pushing the leader?[/quote]





As we've allready discussed the theory behind breaking wind on riders behind you, I'll avoid the impracticalities of dropping a No2. :lol:
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Postby Mr888 » Thu Feb 22, 2007 10:19 pm

pospete wrote:

As we've allready discussed the theory behind breaking wind on riders behind you, I'll avoid the impracticalities of dropping a No2. :lol:


Funny...I thought NO2 made you go faster...it did in "The fast and the Furious 1,2 & 3...."
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Postby pospete » Thu Feb 22, 2007 10:32 pm

Mr888 wrote:
pospete wrote:

As we've allready discussed the theory behind breaking wind on riders behind you, I'll avoid the impracticalities of dropping a No2. :lol:


Funny...I thought NO2 made you go faster...it did in "The fast and the Furious 1,2 & 3...."



well if you guys want to go round dropping the no2s and using them to make yourselves go faster thats your own business. I have to say tho I'dd quite like to watch that bike race, if only to film it for You tube!
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Postby MJF » Fri Feb 23, 2007 8:09 am

Lol. You guys crack me up.

Besides which, No. 2's is accompanied by methane, not Nitrous Oxide :) More like to kill the rider behind you.
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Postby Mr888 » Fri Feb 23, 2007 5:25 pm

MJF wrote:Lol. You guys crack me up.

Besides which, No. 2's is accompanied by methane, not Nitrous Oxide :) More like to kill the rider behind you.


And if you're really talented you can light it and burn your opponants to a crisp :lol:
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