- The age old question facing anyone who cycles to work
or to university, or to school,
is how best do you carry your essentials.
Now, whether that's like a laptop
or a full change of clothes, or possibly both,
it's a question that can very much weigh you down.
- And there are three main options.
There's the rucksack shouldering the weight,
or slinging the weight across the back of your bike,
Panniers, a bit old school,
or the new and trendy option of the Giant saddlebag.
Now, both of these two obviously leave you unencumbered
but they do transform your trusty steed.
- They do.
So each system is going to have its relative merits,
but what we really want to know,
and we suspect secretly you will do too,
is which of them is the fastest.
What is the most aerodynamic way of carrying your stuff?
- It's the GCN Commuteaero challenge.
- Oh that could be a hashtag right there,
Commuteaero.
(upbeat music)
To find the answer to this slightly hairbrained question,
we have enlisted the support of several engineers
who are based here at the world-famous wind tunnel
at the Politecnico Milano.
- Would this actually change
how you carry your stuff to work, Si?
- Yeah, you know what I think it would actually.
I normally use a rucksack because it's easy,
because it leaves my bike feeling light and unencumbered,
but if I could shave off some time, I definitely would.
(upbeat music)
The Politecnico Milano tunnel
is called a closed-circuit tunnel,
and it actually has two test rooms along its length.
Wind is generated by 14 fans,
each is 1.8 meters in diameter,
and requiring a total of 1.4 megawatts of power.
One room is used primarily for civil engineering testing,
so bridges, wind turbines, an the like,
and it can create turbulent wind conditions.
The other room is much smaller
and it gives very stable wind conditions,
which is perfect for testing bikes, riders, and luggage,
which, funny enough, they haven't ever had to test before.
- Our Super Commuter bike here
is rigged up in the wind tunnel.
Si will ride it for six minutes at a time,
while the total drag of him plus bike
is measured and recorded in
the data acquisition center outside the tunnel.
Now, the first two minutes of each test
will be into a straight on headwind.
And then to measure different cross-winds,
what we'll do is rotate the entire platform on a turntable,
which will put him at different angles to the wind,
called yaw angles.
(upbeat music
- This is my actual backpack.
I wanted something that was small
and also super lightweight,
it ticks both of those boxes, it's been great mostly.
What's in it will vary on a given day,
but as a minimum I will have, of course,
a pump, and also a multi-tool and a tube, my laptop,
and then I take a spare pair of socks,
a pair of boxer shorts, and also a T-shirt.
Now, everything else I will leave at work,
but to be a little bit more representative,
I'm also going to stick in a sweatshirt
and a pair of jeans as well.
Oh yeah, hair product too,
couldn't go anywhere without that.
Now you know I'm lying, I don't use hair products,
you knew that.
(upbeat music)
Now last time I was in a wind tunnel,
I did not have glasses.
No one told me how important they were,
cuz your eyes just stream,
so I brought out the trusty old Bono glasses.
Oh yeah.
- Okay so you're all good?
- Good.
- You're going to be okay?
- Hopefully.
- Right, good luck.
Don't shout if there's a problem because we can't hear you.
- Thanks.
- Oh it's a heavy door, wow.
Oh yeah.
(laughs)
(door slams)
Okay.
(upbeat music)
This test will be repeated three times,
one for each of our commuting setups.
The first one being the rucksack,
as you can see there.
You can see here that the scientists of the wind tunnel,
they're marking out Si's position on the bike,
so they can be sure that he recreates
the same body position for each of our tests,
so that it's a fair comparison of the commuting setups.
(upbeat music)
You okay?
- Yes, I'm alright actually.
I've forgotten how weird it is riding in a wind tunnel,
the fact that the wind is completely constant
so it's just this white noise really loud,
but yeah that was good,
it just felt like riding home basically,
into a dark tunnel.
- Bloody freezing too I remember.
- It was, yeah, a little bit cold, but it's alright.
It's kind of the amount of fan-age I need, actually
when I'm training inside so it should be alright.
- Fan-age.
- Fan-age, yeah.
- Good word.
(laughs)
(upbeat music)
- Run number two then, we've got a full bike packing kit.
So we've got Topeak's giant saddlebag,
a frame bag, and also a top-load there.
Roughly the same volume size as the rucksack.
The only slight thing I'm thinking of
is I'm not going to be able to get my laptop in here.
- Yeah you can, it'll fit in there, that's huge.
- Hmm.
- Yeah yeah that'll be fine.
- Are you completely sure about this, Emma?
- Yes, definitely and then just pack the jeans around.
You would take longer than the commute
just to pack the bags but, you know.
- It looks slightly weird
having your underpants in a frame bag.
I can't do it Emma, I can't have a top-tube bag.
I reckon I can squish this stuff in elsewhere.
- Yeah.
- We've got plenty of room.
- You've got loads of space.
It's all about efficient packing, Si.
- You've inspired me with my laptop mud guard.
- That does look a little bit like
a triathlete's lunch box really, doesn't it?
(upbeat music)
So the important thing here is we have Si
in the same body position,
that's why we drew lines around the-
well the scientists drew lines
around the outside of his body.
But, the only thing that's changed is the luggage position
because you can only change one variable at a time,
or we get confusing results.
So, as Stefano was saying, on this screen we can see
the top number is Si's cadence,
Then you have his speed, you have a power meter?
- No we don't have a power meter, we have a force balance.
He is below the line there so that we measure
the wind force to a force balance.
- Yeah, so this is the wind speed, the velocchita,
and then the bottom number there,
that's the drag force,
so that's literally the drag he is experiencing,
as measured by the force balance.
- Yeah.
(upbeat music)
- Okay, still alive?
- Just about, yeah.
- Good work, it doesn't look easy.
- Well the riding itself is fine,
but yeah there's not much to tell really,
the bags were just kind of out of my way.
- You had to hold that position,
it looked like it was getting a bit tiring after awhile.
- Well yeah maybe a little bit.
But yeah it's all good, I'm good,
I'm fascinated to see the results on that one.
Something very new and different.
(upbeat music)
From modern bike packing now, to old-school.
We've got a beautiful pair of hand-made Panniers.
I think we've pretty much doubled the volume of it,
don't you think?
- Yep.
- So maybe I'd better take a week's worth of stuff
actually to work this time.
- Or a big lunch.
- A three-course lunch, yeah now we're talking.
Right, let's do some packing.
Yeah you stick them in your side.
- Okay.
- I'll deal with the pants.
- Yeah.
All set up there?
- Ready.
- See you on the other side.
I won't be sorry to see the back of this door.
(door slams)
(upbeat music)
- Si is pedaling away in the wind tunnel on his third run.
This time we've got the old-school Panniers,
and he's being very tough and hanging in there
with his same body position as before.
And here we can see,
this is the screen that he can also see almost,
you can see that this number here, the drag force,
is in red because it's higher than last time,
in fact it's higher than the first time,
so I think the scientists here are going to
talk us through the results later.
But the interesting thing you can see straightaway
is that, with the Panniers,
his drag is significantly higher
than with either the rucksack or the Giant saddlebag.
(upbeat music)
So, at the moment you can see that
we're changing the yaw angle,
So we're changing Si's rotation to the wind,
which means that it's effectively like
having a cross-wind as you're riding your bike.
And the funny thing is, with the saddlebags,
the number is occasionally green
which means it's occasionally lower
than it was with the rucksack,
which means that, potentially, I'm hypothesizing
these saddlebags acting a bit like a disk wheel,
a bit like a sail effect for the crosswind.
I'm just making that up, so it's probably not true.
The scientists here will tell us later.
Momentary values don't really matter,
it's the average over two minutes that's important.
Well done, Si.
- Thank you, thank you.
- I know it was quite hard work
hanging on there in the wind tunnel.
I've got some slightly bad news for you,
in that scientists down there
say we have to do a baseline test
without any luggage at all.
So we're going to take the Panniers off again,
and you're going to have to go through it again.
- One more time.
- I'm really sorry.
- Well I mean it makes sense.
- It's good for you I mean it's a little bit of training.
- Bit of training, yeah.
Alright let's do it.
- He's tough, he's tough, it's good.
- [Simon] This baseline test will allow us to see
just how much drag I actually create,
minus any luggage at all.
As well as being a point of interest,
it also acts as a control to make sure that the data
from the other tests can be put into context.
So over to Test Engineer Stefano Giappino.
- So we're going to talk through the results
of the commuter comparison with Stefano,
the test engineer here at the wind tunnel.
And Stefano, can you explain,
you've changed that drag force you've measured
into Watts, is that correct?
- Yes, starting from the drag force we got from the balance,
we computed the power to go at 40 kilometers per hour.
So this is the power to overcome
40 kilometers per hour of wind.
- And so we've got the various different
positions of the commuter luggage there,
and these equate to the different setups that Si had.
So we have the rucksack, the Giant saddlebags,
and the Panniers.
So Stefano, what can we see from the results?
- Okay so, we started with no bag at all,
then if we added the bag on the back like this,
we're going in this position so this is slower.
- So there's more watts drag.
- More watts, more drag.
And if we put the bags on the real weight,
this position,
this is the worst position we found.
- So Panniers are the worst?
- Yeah.
- Right, interesting.
- But finally, if we put on the bike,
like the saddle, and this position.
- Giant saddlebag.
- We have almost no difference.
So you should put in this position.
- Good to know, thank you very much.
- We've had the top-line results.
Emma can you hit us with some wattages.
- Hit you with the wattage, indeed.
So the best and the worst,
there was actually 20 watts difference.
- [Simon] 20 watts?
- [Emma] This is quite a lot,
so the best was the Giant saddlebag,
which acts like a sort of bum fairing I think you could say.
- [Simon] Brilliant, we'll need one of those.
- And that was similar to the baseline of no luggage,
in fact even below your angle, so direct headwind,
that might even be slightly faster than no luggage,
in aerodynamic terms.
- Interesting stuff.
And the Panniers, so they were 20 watts slower
than our Giant saddlebag.
- Yep, and if you don't like Panniers anyway,
that's, you know, good reason
not to use them I suppose.
- Yeah, now the thing for me actually,
was the fact that the rucksack was in the middle,
and the guys downstairs were saying that
a lot depends on your actual position on the bike.
So I adopted a relatively sedate position,
and because of my helmet getting in the way,
and because the rucksack is quite narrow,
actually it didn't perhaps cause as much disturbance
as they otherwise thought it might have been,
but if my position was more aerodynamic,
then that would have been more of a hindrance,
is that right?
- Yeah, so your rucksack was essentially behind your helmet
so it acted almost like a fairing behind the helmet.
- Head fairing this time.
- A head fairing.
- Whereas if one was to get super aero,
maybe even commuting for some reason on a Time Trail bike,
the Giant saddlebag is definitely the way forward.
- Yeah, that's yeah, and I should add
that these wattage differences,
that's at 40 kilometers an hour,
and you do get a reduction in advantage as you go slower.
I'm not sure how many people commute at 40k an hour.
- I think it depends on the traffic really.
As a fellow seasoned commuter then,
now we're armed with the data,
are you going to change anything?
- Well I have to say that
I really do like my Giant saddlebag,
although I've been told by a lot of people
for sartorial reasons that it's not pretty.
I don't care, I like the fact that I have a sweat-free back.
But in terms of ease of use for me, always rucksack.
Because it's just so easy to sling it on and off,
and my saddle is so low that I run the risk
with this Giant saddlebag of it rubbing on the back wheel,
which is definitely not quicker, I can tell you that.
- Right, so for me I think, I did say at the beginning
that I would go with whatever is fastest.
I think the convenience of the rucksack
still is possibly going to win out for me.
On my longer commutes, where I want the bike
to feel nice and normal and maneuverable and trackable,
I'm still going to go with a rucksack.
But actually, I would be tempted to dabble
with a Giant saddlebag for when
I need to get from A to B as fast as possible.
That has opened my eyes, in fact, to bike luggage.
So, watch this space.
- So, if you happen to commute,
and you're interested in saving a few minutes,
why not check out GCN's early video,
"Pimp my Commute".
- That's right, save minutes,
get up later, and have more fun.
We've got to say a big "thanks" as well before we go
to Politecnico Milano for loaning us their wind tunnel,
loaning us their expertise,
it's been absolutely brilliant.
And there are more videos coming up soon.
I'd give it a big thumbs up.