Snails around France

[Amarillo]

I’ve been following a couple cycling along the border of France on a tandem. They have just finished Day 30 of a planned 73 day cycle ride, cycling between 60km and 120km per day.

They have just reached the Pyrenees, and what will probably be the toughest portion of their tour, with average gradients up to 24.5%.

What a great alternative to a tour by California.

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[Corradobrit]

Here are a couple of real ladies riding tandem along the coast

 

[RockinNRollin]

Impressive stuff. I cycle toured around France and the Pyrenees about 10 years ago; I remember chasing a "racing tandem" (no luggage, lycra-clad riders, drop bars and looked like a carbon frame) down the Tourmalet. It was an amusing experience; I was fully loaded with panniers front and back with camping kit, bottles of wine etc.. but despite this I could outcorner the tandem, but on the straights despite me touching 40mph, the tandem would come barrelling past! On the flat and downhill, tandems are a force to be reckoned with on straight(ish) sections.

 

[The Tall Luthier]

Impressive stuff. I cycle toured around France and the Pyrenees about 10 years ago; I remember chasing a "racing tandem" (no luggage, lycra-clad riders, drop bars and looked like a carbon frame) down the Tourmalet. It was an amusing experience; I was fully loaded with panniers front and back with camping kit, bottles of wine etc.. but despite this I could outcorner the tandem, but on the straights despite me touching 40mph, the tandem would come barrelling past! On the flat and downhill, tandems are a force to be reckoned with on straight(ish) sections.

It’s an interesting thought experiment. Why did they beat you downhill, what advantage did they have?

Most would answer ‘more weight’ as there were two of them. Force = Mass x Acceleration, so the forces were bigger.

In fact Mass had nothing to do with it. It was pretty much down to Lycra and Paniers

 

[RockinNRollin]

It’s an interesting thought experiment. Why did they beat you downhill, what advantage did they have?

Most would answer ‘more weight’ as there were two of them. Force = Mass x Acceleration, so the forces were bigger.

In fact Mass had nothing to do with it. It was pretty much down to Lycra and Paniers

Aerodynamics; frontal shape is roughly the same as a single cyclist, but they have more weight and more power. Downhill (and on the straights), the biggest limiting factor is aerodynamics - a tandem simply has a greater power to drag ratio.

 

[Amarillo]

It’s an interesting thought experiment. Why did they beat you downhill, what advantage did they have?

Most would answer ‘more weight’ as there were two of them. Force = Mass x Acceleration, so the forces were bigger.

In fact Mass had nothing to do with it. It was pretty much down to Lycra and Paniers

The main drag downhill is wind resistance. Two (or more) on a bike have about the same wind resistance as one, but about twice the mass.

The boys and I can get up to incredible speeds on our triplet, but we are really sluggish uphill.

 

[RockinNRollin]

Yep, biggest downfalls with tandems (and bigger!!) are handling and difficulty of "getting out of the saddle" - not impossible but requires some serious co-ordination! Not sure it would be possible on a triplet actually, on a tandem it would be in theory as you could balance each other out but there'd be some serious torque in the bike frame!

 

[The Tall Luthier]

@Amarillo @RockinNRollin
There is a video clip somewhere of a feather and a cannon ball being dropped from 30m in a vacuum. They land at exactly the same time. Why? Zero air resistance, the ONLY variable affecting speed due to gravity.

 

[RockinNRollin]

@Amarillo @RockinNRollin
There is a video clip somewhere of a feather and a cannon ball being dropped from 30m in a vacuum. They land at exactly the same time. Why? Zero air resistance, the ONLY variable affecting speed due to gravity.

.... in a freefall environment".

There are other complications on a bike even without the aerodynamics, but the latter is still the biggest influence.

Your comment reminds me of the "what's heavier, a ton of coal or a ton of feathers?". Also reminds me of the ball-bearing demonstration with a little device that fires a ball bearing horizontally outwards and releases a second one in freefall; of course they both hit the ground at the same time, but it's an entertaining way of demonstrating horizontal velocity (assuming a neutral-lift object like a non-spinning sphere) has no bearing on vertical acceleration. Sorry about the pun . . .

 

[Amarillo]

@Amarillo @RockinNRollin
There is a video clip somewhere of a feather and a cannon ball being dropped from 30m in a vacuum. They land at exactly the same time. Why? Zero air resistance, the ONLY variable affecting speed due to gravity.

On the road there will be other minor forces in play. Rolling resistance will be greater on a tandem, with the heavier weight squashing the tyres.

The timing chain between the front and rear chainrings will cause some power loss.

I don’t suppose a longer wheelbase makes any difference in a straight line, but tight turns will be slower on a tandem.

You can brake later and harder on a tandem as doing an endo is virtually impossible. As a result tandem forks are usually stronger than a solo.

 

[RockinNRollin]

On the road there will be other minor forces in play. Rolling resistance will be greater on a tandem, with the heavier weight squashing the tyres.

The timing chain between the front and rear chainrings will cause some power loss.

I don’t suppose a longer wheelbase makes any difference in a straight line, but tight turns will be slower on a tandem.

You can brake later and harder on a tandem as doing an endo is virtually impossible. As a result tandem forks are usually stronger than a solo.

2 tyres rolling resistance on a tandem vs 4 tyres (equivalent) for two solo cyclists? I suspect RR of a tandem is probably less than 50% higher than a normal single bike.

Presumably you're more likely to lock up the front wheel on a tandem given the centre of gravity is further back; in addition to "anti-endo" it probably also means less weight shift to the front (so presumably the rear tyre can withstand harder braking without letting go too?)

 

[The Tall Luthier]

On the road there will be other minor forces in play. Rolling resistance will be greater on a tandem, with the heavier weight squashing the tyres.

The timing chain between the front and rear chainrings will cause some power loss.

I don’t suppose a longer wheelbase makes any difference in a straight line, but tight turns will be slower on a tandem.

You can brake later and harder on a tandem as doing an endo is virtually impossible. As a result tandem forks are usually stronger than a solo.

Downhill, I never considered any other forces than gravity. The power train of two people and only one set of air resistance will make a tremendous difference.

In freewheeling mode, the rolling resistance would be negligible if all tyres inflated correctly.

 

[Amarillo]