Drag/Lift Force Sensors for Wind Tunnel?
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Posts: 46,084
Looking for ideas for inexpensive instrumentation (Stamp or perhaps
PIC-based) for a home-made wind tunnel. Specifically, I need to rig
up some sort of force sensor to record drag force on Cub Scout
pinewood derby cars. Goal is to compare car body designs in the wind
tunnel.
Design factors:
Cost - always important!
Sensitivity - important, since cars weigh only 5 oz, traveling at an
average of about 8 MPH over a 30-foot track. Small differences in
drag could be important.
Repeatability - would like to be able to test small design mods, and
the tests are not done head-to-head, so repeatability from test run
to test run is important.
If you're interested, the Scientific American article with the
general plan for the tunnel is at
http://www.sciam.com/1197issue/1197amsci.html
It gives some ideas for (non-electronic) drag & lift measurement.
Any suggestions appreciated!
David Carter
david@c...
PIC-based) for a home-made wind tunnel. Specifically, I need to rig
up some sort of force sensor to record drag force on Cub Scout
pinewood derby cars. Goal is to compare car body designs in the wind
tunnel.
Design factors:
Cost - always important!
Sensitivity - important, since cars weigh only 5 oz, traveling at an
average of about 8 MPH over a 30-foot track. Small differences in
drag could be important.
Repeatability - would like to be able to test small design mods, and
the tests are not done head-to-head, so repeatability from test run
to test run is important.
If you're interested, the Scientific American article with the
general plan for the tunnel is at
http://www.sciam.com/1197issue/1197amsci.html
It gives some ideas for (non-electronic) drag & lift measurement.
Any suggestions appreciated!
David Carter
david@c...
Comments
mass distribution and wheel friction and axle
misalignment. You'd be time and money ahead to
concentrate on getting as much mass as you can as far
back and as high off the track as possible - move the
rear axle back to compensate for the new center of mass
(to keep the front of the car from lifting off the
track.)
Instrumentation to measure the speed of the car would be
interesting though.
Arlen Fletcher
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety." - Benjamin Franklin
> Looking for ideas for inexpensive instrumentation (Stamp or perhaps
> PIC-based) for a home-made wind tunnel. Specifically, I need to rig
> up some sort of force sensor to record drag force on Cub Scout
> pinewood derby cars. Goal is to compare car body designs in the wind
> tunnel.
>
> Design factors:
> Cost - always important!
> Sensitivity - important, since cars weigh only 5 oz, traveling at an
> average of about 8 MPH over a 30-foot track. Small differences in
> drag could be important.
> Repeatability - would like to be able to test small design mods, and
> the tests are not done head-to-head, so repeatability from test run
> to test run is important.
>
> If you're interested, the Scientific American article with the
> general plan for the tunnel is at
> http://www.sciam.com/1197issue/1197amsci.html
> It gives some ideas for (non-electronic) drag & lift measurement.
>
> Any suggestions appreciated!
>
> David Carter
> david@c...
>
>
>
>
platform to a Pot, when the wind pushes the car aft it would move the angle
of the arm, and therby change the pots resistance. Or any variation of the idea.
- Maybe place a pin behind the car. Let the car push aft against the pin,
have the pin attached to a pot, etc.
- Dont use any stamp or computer, just let the car move a rod which is
placed over a paper with some numbers written onto it, then record the
number changes.
Dont use oil on your axle seconds before the race [noparse]:([/noparse]
We had such a brilliant idea years ago, the oil swelled the wood, and made
my car so stuck you could not push it down the tack [noparse]:([/noparse]
Of course 1 run was all that was allowed then DOH
At 10:34 PM 2/7/2001 -0000, you wrote:
>Looking for ideas for inexpensive instrumentation (Stamp or perhaps
>PIC-based) for a home-made wind tunnel. Specifically, I need to rig
>up some sort of force sensor to record drag force on Cub Scout
>pinewood derby cars. Goal is to compare car body designs in the wind
>tunnel.
>
>Design factors:
>Cost - always important!
>Sensitivity - important, since cars weigh only 5 oz, traveling at an
>average of about 8 MPH over a 30-foot track. Small differences in
>drag could be important.
>Repeatability - would like to be able to test small design mods, and
>the tests are not done head-to-head, so repeatability from test run
>to test run is important.
>
>If you're interested, the Scientific American article with the
>general plan for the tunnel is at
>http://www.sciam.com/1197issue/1197amsci.html
>It gives some ideas for (non-electronic) drag & lift measurement.
>
>Any suggestions appreciated!
>
>David Carter
>david@c...
>
>
>
>
>
Sincerely
Kerry
Admin@M...
WWW server hosting [url=Http://mntnweb.com]Http://mntnweb.com[/url]
Kerry Barlow
p.o. box 21
kirkwood ny
13795
If you configure the test model to become part of a spring-mass system, you
can calculate the force that takes to extend a particular spring -
proportional to the drag experienced by the car.
We had a project that even simulated the road, by placing a moving band of
sandpaper under the model, at a speed proportional to the wind velocity of
the tunnel. It's surprising to see the influence that this has, compared to
a smooth surface.
Another option is to use a vertical arm, from which you hang the model, and
attach an LVDT (Linear Variable Differential Transformer, if my memory
serves me right) that changes output voltage with respect to the position of
the shaft, and thus can measure linear displacement very accurately,
probably better than with a resistance pot.
Good luck,
Mike
>
Mensaje original
> De: david@c... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=JjS5nQXHeNNsmkzPrVmG3ItnK68wUipaOUV4v-rlaETo2saIdQXzrXXh4KbH86_5wdkjJsODKw]david@c...[/url
> Enviado el: miercoles, 07 de febrero de 2001 23:34
> Para: basicstamps@yahoogroups.com
> Asunto: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
>
>
> Looking for ideas for inexpensive instrumentation (Stamp or perhaps
> PIC-based) for a home-made wind tunnel. Specifically, I need to rig
> up some sort of force sensor to record drag force on Cub Scout
> pinewood derby cars. Goal is to compare car body designs in the wind
> tunnel.
>
> Design factors:
> Cost - always important!
> Sensitivity - important, since cars weigh only 5 oz, traveling at an
> average of about 8 MPH over a 30-foot track. Small differences in
> drag could be important.
> Repeatability - would like to be able to test small design mods, and
> the tests are not done head-to-head, so repeatability from test run
> to test run is important.
>
> If you're interested, the Scientific American article with the
> general plan for the tunnel is at
> http://www.sciam.com/1197issue/1197amsci.html
> It gives some ideas for (non-electronic) drag & lift measurement.
>
> Any suggestions appreciated!
>
> David Carter
> david@c...
>
>
>
>
>
To measure velocity, a Stamp/PIC based accelerometer, integrated once to
obtain velocity, would be accurate enough for short-duration runs. FWIW,
Nike just introduced a smart pedometer which includes a capsule attached to
a shoe. The capsule includes a velocity sensor and RF transmitter which
sends data to a wrist watch. I don't know the price.
Dennis
Original Message
From: arlen.fletcher@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=KFVLdLNWM4OFdDCudQ3PdJKERLB1FvrYE8CLubhsk3lfU_MvK2U0FZmjciKxM_xCAJkGeES1Z1N9dbfo0DKQ6A]arlen.fletcher@a...[/url
Sent: Wednesday, February 07, 2001 2:42 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
I can't imagine the drag being more significant than
mass distribution and wheel friction and axle
misalignment. You'd be time and money ahead to
concentrate on getting as much mass as you can as far
back and as high off the track as possible - move the
rear axle back to compensate for the new center of mass
(to keep the front of the car from lifting off the
track.)
Instrumentation to measure the speed of the car would be
interesting though.
Arlen Fletcher
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety." - Benjamin Franklin
> Looking for ideas for inexpensive instrumentation (Stamp or perhaps
> PIC-based) for a home-made wind tunnel. Specifically, I need to rig
> up some sort of force sensor to record drag force on Cub Scout
> pinewood derby cars. Goal is to compare car body designs in the wind
> tunnel.
>
> Design factors:
> Cost - always important!
> Sensitivity - important, since cars weigh only 5 oz, traveling at an
> average of about 8 MPH over a 30-foot track. Small differences in
> drag could be important.
> Repeatability - would like to be able to test small design mods, and
> the tests are not done head-to-head, so repeatability from test run
> to test run is important.
>
> If you're interested, the Scientific American article with the
> general plan for the tunnel is at
> http://www.sciam.com/1197issue/1197amsci.html
> It gives some ideas for (non-electronic) drag & lift measurement.
>
> Any suggestions appreciated!
>
> David Carter
> david@c...
>
>
>
>
>From: "Miguel Puchol" <mpuchol@w...>
>Reply-To: basicstamps@yahoogroups.com
>To: <basicstamps@yahoogroups.com>
>Subject: RE: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
>Date: Thu, 8 Feb 2001 09:31:28 +0100
>
>David,
>
>If you configure the test model to become part of a spring-mass system, you
>can calculate the force that takes to extend a particular spring -
>proportional to the drag experienced by the car.
>We had a project that even simulated the road, by placing a moving band of
>sandpaper under the model, at a speed proportional to the wind velocity of
>the tunnel. It's surprising to see the influence that this has, compared to
>a smooth surface.
>Another option is to use a vertical arm, from which you hang the model, and
>attach an LVDT (Linear Variable Differential Transformer, if my memory
>serves me right) that changes output voltage with respect to the position
>of
>the shaft, and thus can measure linear displacement very accurately,
>probably better than with a resistance pot.
>
>Good luck,
>
>Mike
>
> >
Mensaje original
> > De: david@c... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=4IH2uomMKhAmkawQ6LMVKJk4JiarzkP3EjXMc9wPuHR_lqUN6dhfroNE3ImgORbguQNgLFv2ig1E]david@c...[/url
> > Enviado el: miercoles, 07 de febrero de 2001 23:34
> > Para: basicstamps@yahoogroups.com
> > Asunto: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
> >
> >
> > Looking for ideas for inexpensive instrumentation (Stamp or perhaps
> > PIC-based) for a home-made wind tunnel. Specifically, I need to rig
> > up some sort of force sensor to record drag force on Cub Scout
> > pinewood derby cars. Goal is to compare car body designs in the wind
> > tunnel.
> >
> > Design factors:
> > Cost - always important!
> > Sensitivity - important, since cars weigh only 5 oz, traveling at an
> > average of about 8 MPH over a 30-foot track. Small differences in
> > drag could be important.
> > Repeatability - would like to be able to test small design mods, and
> > the tests are not done head-to-head, so repeatability from test run
> > to test run is important.
> >
> > If you're interested, the Scientific American article with the
> > general plan for the tunnel is at
> > http://www.sciam.com/1197issue/1197amsci.html
> > It gives some ideas for (non-electronic) drag & lift measurement.
> >
> > Any suggestions appreciated!
> >
> > David Carter
> > david@c...
> >
> >
> >
> >
> >
>
>
>
>
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im trying to send data wireless, but somehow i have 1-bs2 and 1-bs2sx but
they dont communicate??
any suggestion what is the problem???
Also one of my BS2, when i tried to to download a program is says that can
not find com1, and that it needs power supply??
But it works with others bs2??
so anybody knows what is the problem?
and if so, how can i fix it??
thank you.
>From: "Miguel Puchol" <mpuchol@w...>
>Reply-To: basicstamps@yahoogroups.com
>To: <basicstamps@yahoogroups.com>
>Subject: RE: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
>Date: Thu, 8 Feb 2001 09:31:28 +0100
>
>David,
>
>If you configure the test model to become part of a spring-mass system, you
>can calculate the force that takes to extend a particular spring -
>proportional to the drag experienced by the car.
>We had a project that even simulated the road, by placing a moving band of
>sandpaper under the model, at a speed proportional to the wind velocity of
>the tunnel. It's surprising to see the influence that this has, compared to
>a smooth surface.
>Another option is to use a vertical arm, from which you hang the model, and
>attach an LVDT (Linear Variable Differential Transformer, if my memory
>serves me right) that changes output voltage with respect to the position
>of
>the shaft, and thus can measure linear displacement very accurately,
>probably better than with a resistance pot.
>
>Good luck,
>
>Mike
>
> >
Mensaje original
> > De: david@c... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=cb2TbJsO252k2JmB39HkDlLbUf_3HoAMpPdjOP-2DLyqL8fdfLDXWW2DkKAEJRObC2-eLjsFeTNARA]david@c...[/url
> > Enviado el: miercoles, 07 de febrero de 2001 23:34
> > Para: basicstamps@yahoogroups.com
> > Asunto: [noparse][[/noparse]basicstamps] Drag/Lift Force Sensors for Wind Tunnel?
> >
> >
> > Looking for ideas for inexpensive instrumentation (Stamp or perhaps
> > PIC-based) for a home-made wind tunnel. Specifically, I need to rig
> > up some sort of force sensor to record drag force on Cub Scout
> > pinewood derby cars. Goal is to compare car body designs in the wind
> > tunnel.
> >
> > Design factors:
> > Cost - always important!
> > Sensitivity - important, since cars weigh only 5 oz, traveling at an
> > average of about 8 MPH over a 30-foot track. Small differences in
> > drag could be important.
> > Repeatability - would like to be able to test small design mods, and
> > the tests are not done head-to-head, so repeatability from test run
> > to test run is important.
> >
> > If you're interested, the Scientific American article with the
> > general plan for the tunnel is at
> > http://www.sciam.com/1197issue/1197amsci.html
> > It gives some ideas for (non-electronic) drag & lift measurement.
> >
> > Any suggestions appreciated!
> >
> > David Carter
> > david@c...
> >
> >
> >
> >
> >
>
>
>
>
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