Bicycle VS Moped - Bang Goes The Theory

[Edwards]

Is this program really entertainment using claimed science to get peoples attention and talking about it?
If so it has worked and got people thinking and talking, so did what the producers wanted.

[fatboy]

I actually quite like Bang goes the Theory and my daughter loves it. Necessarily they keep in simple which does lead to over simplification (and he used a hubgear ). The result was clear which was good; I have heard someone argue that the car was more efficient than cycling so cycling to town was bad for the environment! I take the points about sustainability but if they were to do that they'd need the whole programme so the "experiment" would never have been shown which would be a shame.

The biggest cause for "error" is the different speeds and hence wind resistance. It would be interesting to see the difference if the speed was the same. However one could argue that they travelled at the "normal" speed for the vehicle. Jan is obviously a hardcore cyclist and Jem Stansfield also goes around on his bike a lot which is good to show cycling as a normal activity.

[Ayesha]

Energy consumption of a rolling vehicle is a function of how fast it rolls down a known slope.

Why is the idiot at a drag strip ( looks like Shakespeare County Raceway ).


Energy consumption of a human being gets complicated because it tries to maintain a constant temperature of its outer surface. Mopeds don't. If the cyclist was in swimming trunks on a crisp January morning, the 1000 kCals wouldn't have got him to Stratford Garden Centre cafe in Clifford Chambers. On a warm summers day, he'd have got to Cadbury World in Bournville.

Efficiency is measured in g/km, ( or kCals/km ) ie per distance, so a difference in speed doesn't matter.

[Mick F]

Energy consumption of a rolling vehicle is a function of how fast it rolls down a known slope.

Surely there's more to it than that?

If I sat in our Clio at the top of Gunnislake Hill with the the car out of gear and let off the brake, I'd be hitting 60 or 70mph by the time I reached the village.

Do the same with my bike, and I'd be lucky to hit 40mph.

[Ayesha]

Does your Clio weigh the same as you on your bike?

14% gradient x 2000 lb weight x ( 60 mph / 375 constant ) = 44.8 horsepower at 60 mph

14% gradient x 200 lb weight x ( 40 mph / 375 constant ) = 3 horsepower at 40 mph ( 2.25 kW )

Your bike is half as aerodynamic as my racebike !

[meic]

Energy consumption of a rolling vehicle is a function of how fast it rolls down a known slope.

Why is the idiot at a drag strip ( looks like Shakespeare County Raceway ).


Energy consumption of a human being gets complicated because it tries to maintain a constant temperature of its outer surface. Mopeds don't. If the cyclist was in swimming trunks on a crisp January morning, the 1000 kCals wouldn't have got him to Stratford Garden Centre cafe in Clifford Chambers. On a warm summers day, he'd have got to Cadbury World in Bournville.

Efficiency is measured in g/km, ( or kCals/km ) ie per distance, so a difference in speed doesn't matter.

Is this just all an attempt to blind people with irrelevant specialist technological terminology?

Regardless of the arbitrary units you assign to efficiency it* varies with the speed of the vehicle so it does matter.

*fuel efficiency

[Mick F]

Energy consumption of a rolling vehicle is a function of how fast it rolls down a known slope.

Surely there's more to it than that?
If I sat in our Clio at the top of Gunnislake Hill with the the car out of gear and let off the brake, I'd be hitting 60 or 70mph by the time I reached the village.
Do the same with my bike, and I'd be lucky to hit 40mph.

Does your Clio weigh the same as you on your bike?

Of course not! My point entirely.
I said that there must be more to it.
Seems like you agree!

[snibgo]

Did anyone spot that his front panniers had red triangular reflectors that showed to the front of the bike? Tut tut.

Interesting that he "levelled the playing field" by loading up the bike and trailer so the combination weighed 100 kg. So he was carting around 60 kg of rocks.

It's often said that one US gallon (3.785 litres) of petrol contains 31,000 kcal, so 1000 kcal would be 0.122 litres. The programme said the moped "was running at 140 miles per (imperial) gallon", so 3.7 km should have used (3.7/1.6)/140 = 0.0165 gallons = 0.075 litres.

This is a science programme for kiddies, presenting material in a visual, "gee-whiz" manner. It presented the basic physics of the two machines. It demonstrated the obvious (to us cyclists) fact that even an efficient moped is less efficient than a cyclist loaded with 60 kg of rocks and an extra pair of wheels.

[[XAP]Bob]

But presenting an uloaded cycle alongside would have been even more interesting.

[Ayesha]

Energy consumption of a rolling vehicle is a function of how fast it rolls down a known slope.

Why is the idiot at a drag strip ( looks like Shakespeare County Raceway ).


Energy consumption of a human being gets complicated because it tries to maintain a constant temperature of its outer surface. Mopeds don't. If the cyclist was in swimming trunks on a crisp January morning, the 1000 kCals wouldn't have got him to Stratford Garden Centre cafe in Clifford Chambers. On a warm summers day, he'd have got to Cadbury World in Bournville.

Efficiency is measured in g/km, ( or kCals/km ) ie per distance, so a difference in speed doesn't matter.

Is this just all an attempt to blind people with irrelevant specialist technological terminology?

Regardless of the arbitrary units you assign to efficiency it* varies with the speed of the vehicle so it does matter.

*fuel efficiency

To some cyclists, "Bournville" is 'specialist technological terminology'....

[meic]

But presenting an uloaded cycle alongside would have been even more interesting.

I think he was being a bit sly in making it look as if the cyclist had a harder job than he actually did.

Pulling that weight with a trailer can be a very hard task, if you have hills or a headwind.

I bet he picked a still day in addition to a flat test track and kept his speed in the efficient band under 15mph were the wind drag kicks in with a trailer.

A heavily loaded trailer can easily fly along with a tailwind and a flat road but in real life that is a rarity.

If he had had a cyclist doing the same speed as the moped I bet his "mpg" would not have been so good.

[Edwards]

I actually quite like Bang goes the Theory and my daughter loves it. Necessarily they keep in simple which does lead to over simplification (and he used a hubgear ). The result was clear which was good;

Good old family viewing and educational. So far this series seems to be themed about human powered things compared to internal combustion power.
From a teaching point of view it has worked in that you demonstrate something the get the students to evaluate the outcome and even try their own experiments.
The method is not the important part but the outcome, the students wanting to know more.

So if this program inspires your daughter into science or engineering it has worked.

[Ayesha]

Once a vehicle is up to speed, its momentum ( inertia ) keeps it rolling, therefore 'steady state' consumptions are less than a light vehicle. FOR THE SAME FRONTAL AREA. Remember how the heavy cars on your Hot Wheels track kept rolling further
Putting rocks in the bike's panniers would increase its inertia for the same X section frontal area, and be easier to maintain a steady speed.
Only the accellerating phase of the test would be more energy demanding.
A car with a load of luggage will roll for longer along a flat than an empty car.

The wind should have been less than 1 m/s for it to be a worthwhile test.
For a bicycle, the test should have been done inside Ford's Parts Warehouse in Daventry with the doors shut. The floor there follows the curvature of the Earth !

[Mick F]

I'm a master of the sweeping statement, but you beat me hands down!

All floors follow the curvature of the Earth because they are level.

A car lightly loaded can run further than a car fully loaded - this may happen because the tyres need extra air because of the weight.

[NUKe]

[quote="EdwardsGood old family viewing and educational. So far this series seems to be themed about human powered things compared to internal combustion power.
From a teaching point of view it has worked in that you demonstrate something the get the students to evaluate the outcome and even try their own experiments.
The method is not the important part but the outcome, the students wanting to know more.

So if this program inspires your daughter into science or engineering it has worked.[/quote]

Well said Keith.

I vaguely remember it was the bangs Pops, farts and Space which got me interested in Science.