Energy efficiency of a peloton

[jnb]

Amongst other things I tutor physics and talking to a student recently the question arose ...

When a cyclist follows another cyclist they enjoy an energy saving by doing so. Does the lead cyclist do more work in that scenario than a cyclist who does not have a second cyclist behind them?

I have been given on some physics forums arguments both for why there would be an increase in work and why there would not. So, without offering their arguments which might bias the discussion ... does the lead cyclist in a peloton do more work than a cyclist with nobody following them?

 

[Drago]

Following them how closely exactly? Velocity? Temperature? Humidity? Altitude? Are we assuming completely flat terrain with no wind?

 

[Specialeyes]

In short, no. The lead rider also benefits from a 'push' from the aerodynamic tail of a peloton.

 

[gavroche]

Following them how closely exactly? Velocity? Temperature? Humidity? Altitude? Are we assuming completely flat terrain with no wind?

I think you are missing the point. He is not referring to the second cyclist following but to the one leading, whether:
- on his own.
- leading a group.

 

[Ming the Merciless]

Yes because they are riding harder to get away from the cyclists behind them. If no one is there they relax and expend less energy moving forward.

 

[figbat]

My basic understanding of slipstreaming is that all involved get a benefit. The lead person’s benefit comes from a cleaner detachment of the air behind them as it moves around the following object, rather than eddying behind them.

 

[Edwardoka]

Amongst other things I tutor physics and talking to a student recently the question arose ...

When a cyclist follows another cyclist they enjoy an energy saving by doing so. Does the lead cyclist do more work in that scenario than a cyclist who does not have a second cyclist behind them?

I have been given on some physics forums arguments both for why there would be an increase in work and why there would not. So, without offering their arguments which might bias the discussion ... does the lead cyclist in a peloton do more work than a cyclist with nobody following them?

As for wind resistance, my extremely limited understanding is that there is actually a miniscule decrease in drag for the leading rider due to less turbulence in their immediate wake.

For a solo rider, air rushes into the negative pressure space behind the cyclist causing turbulence, whereas if there is a rider directly behind them there is less negative pressure volume for the air to rush into, turning the two riders into a single system.

 

[Edwardoka]

My basic understanding of slipstreaming is that all involved get a benefit. The lead person’s benefit comes from a cleaner detachment of the air behind them as it moves around the following object, rather than eddying behind them.

Snap!

 

[Tenkaykev]

In short, no. The lead rider also benefits from a 'push' from the aerodynamic tail of a peloton.

^^^^This^^^^
Can't remember exactly where I read it but they did some tests in a big wind tunnel and although the leader is shielding the follower he also gets a (very small) push from them.

 

[Ming the Merciless]

I think leader uses 5% less power at 26 mph or some such whilst the following rider may save as much 40% power for same speed. So stick your big riders on the front in a strong headwind and the lighter riders can easily keep up despite putting out less power.

Of course you can also get fully faired two wheel recumbents aka stream liners. They are capable of cruising at 30 mph (for a typical club rider) on the flat due to far superior aerodynamics on their own. The race steam liners you’d never use on normal roads can hit 90 mph on the flat human power only.

 

[fossyant]

Also with a peloton, the the lead rider won't be at the front for that long.

As far as I'm aware there is a tiny benefit like others have said, but pelotons move much faster as the riders output more power for shorter lengths of time per rider.

 

[Ming the Merciless]

Also with a peloton, the the lead rider won't be at the front for that long.

As far as I'm aware there is a tiny benefit like others have said, but pelotons move much faster as the riders output more power for shorter lengths of time per rider.

Indeed plus you also have echelons in side winds to be more efficient. It’s why geese fly in the formations they do. Energy efficiency. If roads were much wider you might see formations like geese do, more regularly.

 

[ozboz]

Ask Hambini ,

 

[Twilkes]

I think leader uses 5% less power at 26 mph or some such whilst the following rider may save as much 40% power for same speed. So stick your big riders on the front in a strong headwind and the lighter riders can easily keep up despite putting out less power.

It's very chivalrous to offer up us bigger riders to a headwind. I'm assuming that once the peloton reaches the hills the smaller riders will then be helping to push us up so we get the chance to ease off by 40% as well?

 

[ColinJ]

It's very chivalrous to offer up us bigger riders to a headwind. I'm assuming that once the peloton reaches the hills the smaller riders will then be helping to push us up so we get the chance to ease off by 40% as well?

I did one forum ride on which we were joined by a very skinny teenager (so slim that he used armwarmers as legwarmers - seriously!). We came to one steepish climb and he blasted away up it at more than double the speed that I could manage. When I eventually managed to crest the summit onto the moor above I spotted him a couple of hundred metres ahead of me, absolutely grovelling into a strong headwind. I got down on the drops, rode up to him and sprinted by so fast that he didn't even have the chance to speak to me. I slowed down a bit further on to let him catch up and he expressed shock at how fast I rode into the wind compared to him. I explained that being double his weight is a BIG handicap for me going uphill where power-to-weight ratio is what counts, but being light and skinny is a BIG handicap into a headwind where absolute power is more important.