rolldown tests (longish)

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

Mikael - thank you for the data and translation.

Chris

"Warren Berger" skrev...

Quoted message said:

Thank you for finding this site, and for translating.

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

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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.

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hpv-klub.dkdefault.aspOpen ↗

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

"Mads Hilberg" skrev

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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.

"Mikael Seierup" skrev ...

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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

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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.

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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

Mikael,

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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!

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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

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

Quoted message said:

"Mikael Seierup" skrev ...

Quoted message said:

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

In article <[email hidden]>, [email hidden] says...

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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 clee.orgclee.orgOpen ↗
- Bellaire, TX USA -

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

Quoted message said:

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.

hpv-klub.dkdefault.aspOpen ↗

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 ;-)

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Odense Special:

1: loosefitting clothes.

Comments: Samme airresistance as the other highracer of the test, the

Lolita.

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This rider is more heavily built which indicates that the bike is a bit

more aerodynamic.

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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

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crouched over handlebars to minimize airresistance.

Comments: The only upright was tested with the rider crouched over the

handlebars

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which more or less resembles the position on a roadbike. The airresistance

was equal

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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.

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Probably due to the very upright seatposition. The two frontwheels adds a

fair bit of drag

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that is markedly reduced when the wheelfairings are utilized. With its

fairing on its fairly

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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

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is probably a measurement error. On the other hand its obvious that the

rainjacket

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add a significant amount of drag. The tailfairing reduces the

airresistance by ~25%

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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

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Comments: The most aerodynamic bike of this test. The first three tries have been

repeated many times

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to reduce statistical error, so the results are very reliable. The

wheeldisc and the aerohelmet

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seems to reduce drag by 5 and 6 percent respectively, which nets you 0.5-1

kph.

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In attempt 4 the backpack is dangling on one arm and totally ruins the

aerodynamics

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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.

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Homemade FWD with tailfairing:

1: Tight clothes.

Comments:

Despite its low seatheight and a tailfairing this bike displays relatively

high airresistance.

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Most likely due to the upright seatingposition. The tailfairing probably

doesn't help much

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either apart from being handy to store stuff in as its too short for the

upright seat.

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However the bike is still relatively fast due to its Schwalbe Stelvio

tires.

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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

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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.

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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

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the narrow handlebars that keeps the arms close to the body and partly

because the seat

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covers the top part of the rear wheel. Loose clothing means 6% more drag.

Flapping clothes

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for touring and bags increases drag significantly. In this case nearly 50

%.

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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

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but probably also that the rearwheel is not out of the airflow behind the

seat.

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The jacket increases drag by 4% and all the kit increases it yet another

4%.

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Regards Mikael

Note: I just translated it so I cannot argue the pros and cons of the

conclusions

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and assumptions. All errors and typos are mine unless I can come up with a

plausible

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excuse or blame someone else. ;-)

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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

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

Quoted message said:

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.

Quoted message said:

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

mvh Mikael

"Torben Scheel"

Quoted message said:

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.

"Gary Mc" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

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 :-|

"Torben Scheel"

Quoted message said:

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 [censored] forbi den en dag og se. Har den
cykelsti og læ?

mvh Mikael

hpv-klub.dkdefault en.aspOpen ↗

Thanks to Mikael.

Regards, Torben

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

Quoted message said:

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

Quoted message said:

Jeg må et [censored] forbi den en dag og se. Har den cykelsti og læ?

Kun læ, men normalt ikke så meget trafik.

vh Torben