rolldown tests (longish)



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Mikael Seierup

Guest
Made in Denmark. Unfortunately in danish. However its a good chance to see some danish homebuilts if
you squint at the small pictures. ;-) Torben Scheel might have the originals in a larger size.

http://www.hpv-klub.dk/Arrangementer/03-05-10_rulletest/default.asp

I will translate the comments for each of the bikes:

Odense Special:

1: loosefitting clothes.

Comments: Samme airresistance as the other highracer of the test, the Lolita. This rider is more
heavily built which indicates that the bike is a bit more aerodynamic. This is probably due to the
higher bottom bracket on the Odense Special.

Kildemoes damecykel:

2: Loosefitting clothes, box on rack, hands at the middle of the handlebars, upper body crouched
over handlebars to minimize airresistance.

Comments: The only upright was tested with the rider crouched over the handlebars which more or less
resembles the position on a roadbike. The airresistance was equal to the highracers despite the
rider being much smaller.

Leitra:

3: With full fairing and wheelfairings.
4: Without faring but with wheelfairings.
5: Without fairing and wheelfairings.

Comments: The Leitra is the bike with the worst aerodynamics when riding sans fairing. Probably due
to the very upright seatposition. The two frontwheels adds a fair bit of drag that is markedly
reduced when the wheelfairings are utilized. With its fairing on its fairly aerodynamic but is not
significantly faster on the road due to its weight.

Hjemmelavet forhjulstrukket lowracer (homemade FWD yada, yada)

6: Tailfairing, T-shirt.
7: Tailfairing with 6 kg of luggage, loosefitting clothes
8: Tailfairing, loosefitting clothes, rainjacket.
9: No fairing, loose clothes.
10: No fairing, loose clothes, rainjacket.

Comments: Attempt 2 should have yielded more airresistance than 1. That this is not the case is
probably a measurement error. On the other hand its obvious that the rainjacket add a significant
amount of drag. The tailfairing reduces the airresistance by ~25% whichs nets you 2-3 kph.

Optima Baron:

11: tightfitting clothes, wheeldisc on front wheel, aerohelmet
12: Tight clothes, 18 spoke front wheel, aerohelmet.
13: Tight clothes, wheeldisc on front, ordinary helmet
14: Tight clothes, wheeldisc on front, ordinary helmet, backpack dangling on arm

Comments: The most aerodynamic bike of this test. The first three tries have been repeated many
times to reduce statistical error, so the results are very reliable. The wheeldisc and the
aerohelmet seems to reduce drag by 5 and 6 percent respectively, which nets you 0.5-1 kph. In
attempt 4 the backpack is dangling on one arm and totally ruins the aerodynamics and dramatically
doubles the airresistance.

Homemade Zox-clone:

15: Tightfitting clothes, small seatbags.

Comments: This lowracer has lower drag than most of the other bikes. But the tires Schwalbe City
Marathon has a rather high rolling resistance, which slows it down.

Homemade FWD with tailfairing:

16: Tight clothes.

Comments:

Despite its low seatheight and a tailfairing this bike displays relatively high airresistance. Most
likely due to the upright seatingposition. The tailfairing probably doesn't help much either apart
from being handy to store stuff in as its too short for the upright seat. However the bike is still
relatively fast due to its Schwalbe Stelvio tires.

Homemade "Lolita" highracer.

17: loosefitting jacket.
18: loosefitting jacket, topbag behind seat.
19: loose jacket, topbag, arms in superman position

Comments: The Vittoria Corsa EVO CX tires makes the bike relatively fast in relation to the other
highracer of the test that has the same airresistance. The topbag does not affect anything
significantly but the position of the arms does. When the handlebars are tilted forward so the arms
are extended (superman) the airresistance is reduced by 18% which nets you 2 kph.

Evita-2:

20: Tightfitting clothes
21: Loose clothing
22: Dressed for touring with bags

Comments: This quasilow bike has relatively low airresistance. This is probably due to the narrow
handlebars that keeps the arms close to the body and partly because the seat covers the top part of
the rear wheel. Loose clothing means 6% more drag. Flapping clothes for touring and bags increases
drag significantly. In this case nearly 50 %.

Evita-1:

23: No helmet or jacket.
24: No helmet, loosefitting jacket.
25: helmet, jacket, bag, waterbottle

Comments: The old model of the Evita is a bit slower than the new. This is partly due to the larger
rider but probably also that the rearwheel is not out of the airflow behind the seat. The jacket
increases drag by 4% and all the kit increases it yet another 4%.

Regards Mikael

Note: I just translated it so I cannot argue the pros and cons of the conclusions and
assumptions. All errors and typos are mine unless I can come up with a plausible excuse or
blame someone else. ;-)
 
W

Warren Berger

Guest
Mikael,

Thank you for finding this site, and for translating.

Too bad they didn't do all the runs with the same rider.

Some take-home insights:

The rider, by far, is the largest contributor to drag. Get a slim rider in aero position, tight
cloths, and aero helmet.

Tail fairings won't offset a big rider in loose clothing.

Even a full fairing doesn't guarantee low aero drag.

A small, poorly designed tail fairing/bag won't help. It won't hurt either.

Hi racers appear about as aero as low, and semi low-racers.

Warren
 
C

Chris Crawford

Guest
Mikael - thank you for the data and translation.

Chris
 
M

Mikael Seierup

Guest
"Warren Berger" skrev...
> Thank you for finding this site, and for translating.

Our danish HPV-site so it wasn't all that hard to find. ;-)

> Hi racers appear about as aero as low, and semi low-racers.

Oh? I don't feel the data supports that. Or rather the tailfaired Baron with assorted aerogoodies
got em all beat. 7-10 kph is quite a difference in my book. You could probably reduce that gap by
tailfairing them but only by 3-4 kph.

Btw. the piece was written by Mark Olaf Slot and the webmagic was performed by Torben Scheel.

M.
 
M

Mads Hilberg

Guest
> http://www.hpv-klub.dk/Arrangementer/03-05-10_rulletest/default.asp
>

Very interesting. Do you know if there are any plans to expand this? Obvious omissions are some
retail 26/20 SWB recumbents, your Velokraft, a fully faired bike, the effect of various trailers and
some more trikes. It would also be interesting to take a bike with USS and compare it with itself
(!) in an OSS configuration.

Maybe we could translate the site to English, post the methodology and invite people to add to
the database.

Mads
 
M

Mikael Seierup

Guest
"Mads Hilberg" skrev

> Very interesting. Do you know if there are any plans to expand this? Obvious omissions are some
> retail 26/20 SWB recumbents, your Velokraft, a fully faired bike, the effect of various trailers
> and some more trikes. It would also be interesting to take a bike with USS and compare it with
> itself (!) in an OSS configuration.

Just arrange it with Mark. The hill they use is west of Odense. I just didn't have time to go there
plus Storebælt presents a challenge when it comes to bringing recumbents on the train.

Or we could try to dig up some suitable hills around the country depending on how amenable to change
his computerprogram is.

M.
 
M

Mikael Seierup

Guest
"Mikael Seierup" skrev ...
> Or we could try to dig up some suitable hills around the country depending on how amenable to
> change his computerprogram is.

Talking to myself and Mads so it will be in Danish. Sorry ;o)

Der er faktisk en god bakke lige før man kører ind i Farum, når man følger cykelstien op langs
Hillerød (Farum?) motorvejen. Den har cykelsti med god overflade og træer langs siderne, der giver
læ og vigtigst af alt ingen væsentlige sideveje eller kryds. Den går i en blid kurve mod højre, men
intet der nødvendiggør bremser. Desuden er der en bro nede for enden af den, man kan stå under, hvis
vejret driller. Jeg kommer som regel op på en 50-60 km/t uden at træde.

Det hjælper selvfølgelig ikke dig oppe i det mørke og flade Jylland. ;.)

mvh Mikael
 
M

Mads Hilberg

Guest
> Just arrange it with Mark. The hill they use is west of Odense.

Okay - once I have my StreetMachine I'll contact him. We can try it with and without panniers,
trailer, SON dynamo hub on/off, etc. If I can mount the fairing, that could be tried also, although
I wasn't able to fit it onto my friend's SMGT with the brackets you sold it to me with - the cable
guide for the front derailleur was in the way. Rather odd seeing as the fairing is made by
HPVelotechnik!! Guess I'll need a different mounting bracket.

> I just didn't have time to go there plus Storebælt presents a challenge when it comes to bringing
> recumbents on the train.

Now that's just a myth. I've taken my recumbent and Bob Yak with me loads of times all the way from
Copenhagen to Thisted with no problems (sometimes with the fairing mounted!). Sometimes I've been
given a bike reservation, other times a pram reservation. Either way the conductors have never
minded and I've never had any problems with other passengers either. Just remember to book a couple
of days in advance and don't tell the ticket staff that your bike is a recumbent and don't mention
your trailer. I think it'd be more problematic with a tandem (or a trailer so big it can't be
stacked on top of the bike) though.

Of course it's not a myth that you didn't have time :)

Mads
 
W

Warren Berger

Guest
Mikael,

> > Hi racers appear about as aero as low, and semi low-racers.
>
> Oh? I don't feel the data supports that.

I wish I had more info, in English.

But look at the 250 W speeds, which should magnify any aero differences. The Baron is using some, or
all, aero tricks known to man on its runs. The high racers are using none. No tight cloths, no aero
helmets, no wheel discs, no tail fairings. The Baron is the only low or semi-low to clearly beat the
high racers. The only other faster low or semi-low is the one with the huge tail fairing. Without
the fairing, or with loose cloths, it is slower!

> Or rather the tailfaired Baron with assorted aerogoodies got em all beat.

Again, if it didn't win using everything short of a full fairing something would be terribly wrong.

Warren
 
G

Gary Mc

Guest
"Mikael Seierup" <[email protected]> wrote in message
news:<[email protected]>...
> "Mikael Seierup" skrev ...
> > Or we could try to dig up some suitable hills around the country depending on how amenable to
> > change his computerprogram is.
>
> Talking to myself and Mads so it will be in Danish. Sorry ;o)
>
>

Being stationed in Europe a couple of times, Danish was the hardest language for me to get any
handle on. In every other language that I had to use at least "beer" sounded about the same as
English. In Danish It is spelled something like "oel" using the English aphabet: but, asking for
"oil" never got me what I wanted. Luckily, most Danes that I met are bilingual, trilingual or
whatever. They are also very patient with others who stumble badly in their language.

Gary McCarty, Greenspeed GTO, Salt Lake City
 
C

Cletus D . Lee

Guest
In article <[email protected]>, [email protected] says...
> In every other language that I had to use at least "beer" sounded about the same as English. In
> Danish It is spelled something like "oel" using the English aphabet: but, asking for "oil" never
> got me what I wanted.

Did you ever try asking for 'ale'? For that is the likely the English counterpart. Beer is bier and
then I had to ask for a 'Pivo' in Prague. I never did find out what beer was in Hungarian. But then
I don't think the Hungarians ever found out what beer/bier was to give it a Hungarian/Magyar name.

--
Cletus D. Lee Bacchetta Giro Lightning Voyager http://www.clee.org
- Bellaire, TX USA -
 
T

Torben Scheel

Guest
"Mikael Seierup" <[email protected]> wrote in message
news:[email protected]...
> Made in Denmark. Unfortunately in danish. However its a good chance to see some danish homebuilts
> if you squint at the small pictures. ;-) Torben Scheel might have the originals in a larger size.
>
> http://www.hpv-klub.dk/Arrangementer/03-05-10_rulletest/default.asp
>
> I will translate the comments for each of the bikes:

I guess I'll have to get to work now, thanks for the translation. If you fall into a timegap, feel
free to translate the rest ;-)

>
> Odense Special:
>
> 1: loosefitting clothes.
>
> Comments: Samme airresistance as the other highracer of the test, the
Lolita.
> This rider is more heavily built which indicates that the bike is a bit
more aerodynamic.
> This is probably due to the higher bottom bracket on the Odense Special.
>
> Kildemoes damecykel:
>
> 1: Loosefitting clothes, box on rack, hands at the middle of the
handlebars, upper body
> crouched over handlebars to minimize airresistance.
>
> Comments: The only upright was tested with the rider crouched over the
handlebars
> which more or less resembles the position on a roadbike. The airresistance
was equal
> to the highracers despite the rider being much smaller.
>
> Leitra:
>
> 1: With full fairing and wheelfairings.
> 2: Without faring but with wheelfairings.
> 3: Without fairing and wheelfairings.
>
> Comments: The Leitra is the bike with the worst aerodynamics when riding
sans fairing.
> Probably due to the very upright seatposition. The two frontwheels adds a
fair bit of drag
> that is markedly reduced when the wheelfairings are utilized. With its
fairing on its fairly
> aerodynamic but is not significantly faster on the road due to its weight.
>
> Hjemmelavet forhjulstrukket lowracer (homemade FWD yada, yada)
>
> 1: Tailfairing, T-shirt.
> 2: Tailfairing with 6 kg of luggage, loosefitting clothes
> 3: Tailfairing, loosefitting clothes, rainjacket.
> 4: No fairing, loose clothes.
> 5: No fairing, loose clothes, rainjacket.
>
> Comments: Attempt 2 should have yielded more airresistance than 1. That this is not
the case
> is probably a measurement error. On the other hand its obvious that the
rainjacket
> add a significant amount of drag. The tailfairing reduces the
airresistance by ~25%
> whichs nets you 2-3 kph.
>
> Optima Baron:
>
> 1: tightfitting clothes, wheeldisc on front wheel, aerohelmet
> 2: Tight clothes, 18 spoke front wheel, aerohelmet.
> 3: Tight clothes, wheeldisc on front, ordinary helmet
> 4: Tight clothes, wheeldisc on front, ordinary helmet, backpack dangling
on arm
>
> Comments: The most aerodynamic bike of this test. The first three tries have been
repeated many times
> to reduce statistical error, so the results are very reliable. The
wheeldisc and the aerohelmet
> seems to reduce drag by 5 and 6 percent respectively, which nets you 0.5-1
kph.
> In attempt 4 the backpack is dangling on one arm and totally ruins the
aerodynamics
> and dramatically doubles the airresistance.
>
> Homemade Zox-clone:
>
> 1: Tightfitting clothes, small seatbags.
>
> Comments: This lowracer has lower drag than most of the other bikes. But the tires Schwalbe City
> Marathon has a rather high rolling resistance, which slows
it down.
>
> Homemade FWD with tailfairing:
>
> 1: Tight clothes.
>
> Comments:
>
> Despite its low seatheight and a tailfairing this bike displays relatively
high airresistance.
> Most likely due to the upright seatingposition. The tailfairing probably
doesn't help much
> either apart from being handy to store stuff in as its too short for the
upright seat.
> However the bike is still relatively fast due to its Schwalbe Stelvio
tires.
>
> Homemade "Lolita" highracer.
>
> 1: loosefitting jacket.
> 2: loosefitting jacket, topbag behind seat.
> 3: loose jacket, topbag, arms in superman position
>
> Comments: The Vittoria Corsa EVO CX tires makes the bike relatively fast in relation
to
> the other highracer of the test that has the same airresistance. The topbag does not affect
> anything significantly but the position of the
arms does.
> When the handlebars are tilted forward so the arms are extended (superman) the airresistance is
> reduced by 18% which nets you 2 kph.
>
> Evita-2:
>
> 1: Tightfitting clothes
> 2: Loose clothing
> 3: Dressed for touring with bags
>
> Comments: This quasilow bike has relatively low airresistance. This is
probably due to
> the narrow handlebars that keeps the arms close to the body and partly
because the seat
> covers the top part of the rear wheel. Loose clothing means 6% more drag.
Flapping clothes
> for touring and bags increases drag significantly. In this case nearly 50
%.
>
> Evita-1:
>
> 1: No helmet or jacket.
> 2: No helmet, loosefitting jacket.
> 3: helmet, jacket, bag, waterbottle
>
> Comments: The old model of the Evita is a bit slower than the new. This is partly
due to the larger rider
> but probably also that the rearwheel is not out of the airflow behind the
seat.
> The jacket increases drag by 4% and all the kit increases it yet another
4%.
>
>
> Regards Mikael
>
> Note: I just translated it so I cannot argue the pros and cons of the
conclusions
> and assumptions. All errors and typos are mine unless I can come up with a
plausible
> excuse or blame someone else. ;-)
 
T

Torben Scheel

Guest
> Hi racers appear about as aero as low, and semi low-racers.

Yes, but in a real world comparison, the low ones will go faster, as the windspeed near the
ground is lower.

Torben
 
T

Torben Scheel

Guest
"Mikael Seierup" <[email protected]> wrote in message
news:[email protected]...

> Der er faktisk en god bakke lige før man kører ind i Farum, når man følger cykelstien op langs
> Hillerød (Farum?) motorvejen. Den har cykelsti med god overflade og træer langs siderne, der giver
> læ og vigtigst af alt ingen væsentlige sideveje eller kryds. Den går i en blid kurve mod højre,
> men intet der nødvendiggør bremser. Desuden er der en bro nede for enden af den, man kan stå
> under, hvis vejret driller. Jeg kommer som regel op på en 50-60 km/t uden at
træde.

Alternativt er der en stejl en på vejen fra Lynge til Ganløse (tæt ved ganløse). Jeg tror at den vil
være bedre, da den er en del hurtigere, og stejlere i starten.
>
> Det hjælper selvfølgelig ikke dig oppe i det mørke og flade Jylland. ;.)
>
> mvh Mikael
 
M

Mikael Seierup

Guest
"Torben Scheel"

> I guess I'll have to get to work now, thanks for the translation. If you fall into a timegap, feel
> free to translate the rest ;-)

A timegap would be neat. Then I might have time to meet my deadline.

M.
 
T

Torben Scheel

Guest
"Gary Mc" <[email protected]> wrote in message
news:[email protected]...
> Being stationed in Europe a couple of times, Danish was the hardest language for me to get any
> handle on. In every other language that I had to use at least "beer" sounded about the same as
> English. In Danish It is spelled something like "oel" using the English aphabet: but, asking for
> "oil" never got me what I wanted.

No problem these days, every other pub is Irish now. Asking for øl can be a problem sometimes :-|
 
M

Mikael Seierup

Guest
"Torben Scheel"

> Alternativt er der en stejl en på vejen fra Lynge til Ganløse (tæt ved ganløse). Jeg tror at den
> vil være bedre, da den er en del hurtigere, og stejlere i starten.

Broskov bakke? Ned mod Ganløse eller mod Bastrup Sø? Jeg må et **** forbi den en dag og se. Har den
cykelsti og læ?

mvh Mikael
 
T

Torben Scheel

Guest
"Mikael Seierup" <[email protected]> wrote in message
news:[email protected]...

> Broskov bakke? Ned mod Ganløse eller mod Bastrup Sø?
Jeps, det vidste jeg ikke at den hed. Forbi Ganløse Eged nordfra ad lyngevej efter Bastrup Sø

> Jeg må et **** forbi den en dag og se. Har den cykelsti og læ?
Kun læ, men normalt ikke så meget trafik.

vh Torben
 
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