Article on coastdown tests



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Hej Torben

Jeg tester lige, om overskriften har indflydelse på responsen. ;-)

M.
 
Ian <[email protected]> wrote in message news:<BB6AB4C9.D92E%[email protected]>...
> Jerry Rhodes must be edykated coz e writed:
>
> > Do you mean the 2m tall, well built, artic blonde?
> No that's a polar bear!

Ohhh!!!! Mercy sakes I think that I have been on my GRR too long......

Jerry
 
"Jerry Rhodes" skrev...

> > Jerry Rhodes must be edykated coz e writed:
> >
> > > Do you mean the 2m tall, well built, artic blonde?
> > No that's a polar bear!
>
>
> Ohhh!!!! Mercy sakes I think that I have been on my GRR too long......

Sorry. I was just trying to test if a more catchy subject line would generate more replies. It did
but only of the silly sort alas. ;-) One of you even mailed me because he couldn't spot her.

So for the record: Theres no nekkid lady on any of the photos. If you see any I recommend a good
shrink. ;-)

M.
 
"Mikael Seierup" <[email protected]> kirjoitti viestissä
news:[email protected]...
>
> So for the record: Theres no nekkid lady on any of the photos. If you see any I recommend a good
> shrink. ;-)
>
> M.

Let us assume:

I see naked ladies in those pictures.

I do as you recommend, search a good shrink.

Then I assumably do not see any naked ladies there.

Should I be happier now?

-----

More seriously, I see the method of being able to measure air drag easily an important step in
developing better recumbents.

Imagine an analogy: we would not be able to measure the weigth of the bike. There would be differing
feelings, writing here how we feel about the weight.

'My bike weighs a lot'

' I think that A weighs more than B today.'

' Last week C and D were about equally heavy.'

'What would you think about the weight of bike X? I feel it is a bit heavy. '

' I do not know if part A in my bike weighs more than part B. I do not know how to find out that'.

' I removed a part from my bike and now the bike seems to be a lot heavier than earlier How come?'

etc.

Instead of weight we could imagine life without a speedometer and clock/distance measurement. How
fast is the bike? We could compare two riders and bike on the same location and time, but that would
be all. The life would be quite different compared to the current situation.

Our situation with air drag coefficient, (air resistance, air resistance force etc) has been like
above: we have not in practise been able to measure the air drag coefficient of our bike and rider
We have not been able to study how different solutions change the air drag. Not even knowing,
whether they increase or decrease the drag.

What a wonderful future we would have when talking next year like this

'I had Cd*A of 2.2 square ft in my previous homebuilt (and I as driver with standard clothing and
position) , but this new one has only 2.0 sq.ft'.

' I calculated that I could increase my top speed 5 % by improving the Cd*A with some simple tricks.
I made the changes and tested then on the road. True!'
 
"optimistx" skrev

> I do as you recommend, search a good shrink.
>
> Then I assumably do not see any naked ladies there.
>
> Should I be happier now?

Errr. Good point actually. :)

> Instead of weight we could imagine life without a speedometer and clock/distance measurement. How
> fast is the bike? We could compare two riders and bike on the same location and time, but that
> would be all. The life would be quite different compared to the current situation.

I'm riding without one atm. Speedsensor was on the blink so I only have cadence. Works okay really.
You can get a fair idea of how fast you're going from a gearcalculator. So when I'm in 4th and doing
100 rpms I'm going 18-19 mph indicated etc.

> Our situation with air drag coefficient, (air resistance, air resistance force etc) has been like
> above: we have not in practise been able to measure the air drag coefficient of our bike and rider
> We have not been able to study how different solutions change the air drag. Not even knowing,
> whether they increase or decrease the drag.
>
> What a wonderful future we would have when talking next year like this
>
> 'I had Cd*A of 2.2 square ft in my previous homebuilt (and I as driver with standard clothing and
> position) , but this new one has only 2.0 sq.ft'.
>
> ' I calculated that I could increase my top speed 5 % by improving the Cd*A with some simple
> tricks. I made the changes and tested then on the road. True!'

The idea was that you could play around with stuff to improve your speed or just for the fun of it.
So instead of using obscure numbers we could go: "Oh, that splitter fin actually did work. I tested
it on that hill." Mark Olaf Slot designs windmills for Vestas AFAIK, so he probably knows what hes
talking about and this method is cheaper than a windtunnel.

Cheers Mikael
 
"Mikael Seierup" <[email protected]> wrote in message
news:<[email protected]>...
> Mark translated his article on their tests. You can also obtain a copy of the computerprogram
> used. http://www.hpv-klub.dk/artikler/coastdowntest/default.asp
>
> Mikael

That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis? Why
is the Baron so fast?
 
Mikael Seierup wrote:
> Mark translated his article on their tests. You can also obtain a copy of the computerprogram
> used. http://www.hpv-klub.dk/artikler/coastdowntest/default.asp

I found the article very interesting. Mark Olaf Slot seems to have taken coast down testing to a
new level.

I particularly enjoyed studying the data to compare highracers to lowracers without fairings. The
data seems to indicate that the two compare quite close in performance. The lowracers might have an
edge at higher powers and speed, while the highracers might have an edge at more typical cruising
powers. I'm assuming this is most likely due to the lower rolling resistance of the highracers.

Unfortunately, the report only states that "the rolling resistance coefficient can be looked up in a
table". It would be very interesting to see the data that was used for the rolling resistance of the
bikes that were tested.

It's also unfortunate that there were no highracers with fairing that were tested. There's a lot of
information in the data published, I just wish he would of included more data about each of the
bikes studied, as well as the equations he used for the simulation.

But for me personally, it was nice to see data that seemed to backup my feelings that highracer
designs make a lot of sense for a bike that spends most of it's time cruising at relatively low
power levels.

Rick Moll
 
"Rick Moll" skrev...
> Unfortunately, the report only states that "the rolling resistance coefficient can be looked up in
> a table". It would be very interesting to see the data that was used for the rolling resistance of
> the bikes that were tested.

You could write him and ask. I think his e-mail addy was in there somewhere.

> It's also unfortunate that there were no highracers with fairing that were tested. There's a lot
> of information in the data published, I just wish he would of included more data about each of the
> bikes studied, as well as the equations he used for the simulation.

The beauty is that you can get that data if someone drags their sorry butts up on the hill. :)
Both highracers were homebuilts however, so I guess they hadn't gotten around to a tailbox yet. Or
don't want one.

One suggestion from BROL was to spin the pedals going down to better simulate real riding
conditions. (Spin backwards maybe to avoid adding speed). Thats one thing I'd like to see.

Mikael
 
"TwoYearDouble" <[email protected]> kirjoitti viestissä
news:[email protected]...
> "Mikael Seierup" <[email protected]> wrote in message
news:<[email protected]>...
> > Mark translated his article on their tests. You can also obtain a copy of the computerprogram
> > used. http://www.hpv-klub.dk/artikler/coastdowntest/default.asp
> >
> > Mikael
>
> That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
> faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis?
> Why is the Baron so fast?

Mikael and others may answer about the direct physical reasons for the speed of Optima Baron.

As the developer of the computer program and the whole measurement system Mark Olaf Slot (the rider
of Optima Baron) may have learnt many small useful tricks to increase the speed of the bike.

E.g. in numerous trials one may find out, how the exact position of the whole body (especially legs,
hands) should be to maximize speed. The clothing, shoes.

The combination of things which affect air drag and thus speed in the bike and rider is for most
people (incl. me) seemingly very mysterious and astonishing, and only systematic measurable
experimenting can lead to good results soon.

E.h. to my astonishment I read about formula F1 racing cars: the car BEHIND may decrease the air
drag in FRONT of it even 30 % by positioning itself suitably! (there was an image with detailed
curve as a function of distance made by measuring the drag so the results sounded trustworthy).

In the bike there may be such 'formula phenomenons' , which are not common sense. The parts within
the bike may interact very differently depending on the mutual distance,direction etc.

With Mark's method one might find such. He might have already found some of those. These things are
usually trade secrets or other secrets , found out expensively in wind tunnels or with extensive
trial and error. And if a successful competitor finds out 'air drag secrets', how eager is he to
tell to fellow competitors?

I am very grateful for Mark publishing his results and even offering the computer program to be
used. His work has inspired me a lot to investigate the topic.
 
TwoYearDouble wrote:
>
> That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
> faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis?
> Why is the Baron so fast?

It would be nice to hear from Mark Olaf Slot himself; but there are several things which kind of
leap out from the pictures of him on his Baron, which may be part of the reason he can achieve such
a low CdA:

1) His torso is quite horizontal (I measure about 36 degs).

2) While some of the other bikes also have very laid back riders (although none of them are any
more laid back), Mark's shoulders are also laid back with his head bent forward more at the
neck, rather than at the shoulders like the other bike's riders. I would think that this
would not only lower the frontal area (A), but also help to reduce the Cd.

3) Last but perhaps most significant, the fairing appears to be very closely matched to the
outline of his torso; and the fairing also appears to be much longer in relation to it's
frontal area, than on any other bike.

Rick Moll
 
"Rick Moll" skrev...
> TwoYearDouble wrote:
> >
> > That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
> > faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis?
> > Why is the Baron so fast?

There was a picture of the Zox-clone and Baron side by side (seen from behind) with the riders on.
Easy to see that the Baron had the smallest profile by far.

> It would be nice to hear from Mark Olaf Slot himself; but there are several things which kind of
> leap out from the pictures of him on his Baron, which may be part of the reason he can achieve
> such a low CdA:

He doesn't post here I think but you can email him. You did check out the results for the different
bikes and comments? The link is at the bottom of the page.

Mark uses every advantage. Laidback position. Very narrow handlebars which ought to please the Great
Hramstergod Basil. An effective and light tailfairing. Aerohelmet, tight clothes, wheelcover,
aerorims etc. He even aligns his QR so the handle has minimal resistance. :) Plus hes skinny and
yes the fairing is adapted perfectly to him.

Mikael
 
So if I read this correctly, it is possible to enhance the performance of a BiGHA by having a
speedier, lighter, svelte bike following in behind it :)

William Higley, Sr. Vision R-50 RANS Rocket "optimistx" <[email protected]> wrote in message
news:[email protected]...
>
> "TwoYearDouble" <[email protected]> kirjoitti viestissä
> news:[email protected]...
> > "Mikael Seierup" <[email protected]> wrote in message
> news:<[email protected]>...
> > > Mark translated his article on their tests. You can also obtain a copy of the computerprogram
> > > used. http://www.hpv-klub.dk/artikler/coastdowntest/default.asp
> > >
> > > Mikael
> >
> > That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
> > faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis?
> > Why is the Baron so fast?
>
> Mikael and others may answer about the direct physical reasons for the speed of Optima Baron.
>
>
> As the developer of the computer program and the whole measurement system Mark Olaf Slot (the
> rider of Optima Baron) may have learnt many small
useful
> tricks to increase the speed of the bike.
>
> E.g. in numerous trials one may find out, how the exact position of the whole body (especially
> legs, hands) should be to maximize speed. The clothing, shoes.
>
> The combination of things which affect air drag and thus speed in the bike and rider is for most
> people (incl. me) seemingly very mysterious and astonishing, and only systematic measurable
> experimenting can lead to good results soon.
>
> E.g. to my astonishment I read about formula F1 racing cars: the car
BEHIND
> may decrease the air drag in FRONT of it even 30 % by positioning itself suitably! (there was an
> image with detailed curve as a function of
distance
> made by measuring the drag so the results sounded trustworthy).
>
> In the bike there may be such 'formula phenomenons' , which are not common sense. The parts within
> the bike may interact very differently depending
on
> the mutual distance,direction etc.
>
> With Mark's method one might find such. He might have already found some
of
> those. These things are usually trade secrets or other secrets , found out expensively in wind
> tunnels or with extensive trial and error. And if a successful competitor finds out 'air drag
> secrets', how eager is he to
tell
> to fellow competitors?
>
> I am very grateful for Mark publishing his results and even offering the computer program to be
> used. His work has inspired me a lot to investigate the topic.
 
William Higley, Sr. wrote:
> So if I read this correctly, it is possible to enhance the performance of a BiGHA by having a
> speedier, lighter, svelte bike following in behind it :)
>

If you can afford a Bigha, you can probably afford to hire someone to follow you around on a sprint
bike. And maybe a nice big truck to drive in front of you. That's one way to make it faster.

Lorenzo L. Love http://home.thegrid.net/~lllove

Talk is cheap because supply exceeds demand
 
"TwoYearDouble" <[email protected]> wrote in message
news:[email protected]...
> "Mikael Seierup" <[email protected]> wrote in message
news:<[email protected]>...
> > Mark translated his article on their tests. You can also obtain a copy of the computerprogram
> > used. http://www.hpv-klub.dk/artikler/coastdowntest/default.asp
> >
> > Mikael
>
> That is an impressive effort. But it is not obvious to me as to why the Optima Baron is so much
> faster/more efficient than all of the other similarly profiled low-racers. What is the anlysis?
> Why is the Baron so fast?

I upgraded to a Baron from a Vision R-50 2 months ago. So far I'm at least 5 to 6 mph faster average
and maybe 5 mph higher top speed. Now some could say its improved aerodynamics and a lighter bike,
better tires and maybe a more efficent riding position and maybe its because I'm in better shape but
NO its because the thing is EVIL!

It tempts me to go faster, I can almost hear it

"Take this corner a little harder"

"You can keep up with those DF's....try it"

"You can easily pass those DF's....try it"

"Is that the best you can do?"

See a Lamborgini can do 55 mph but the car just doesn't like doing it, the Baron is the same way.
Damn the experts and call me crazy but this bike is evil!
 
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