I want to find out the best way (using fans) to lift my project (quite
light, just the weight of the fans, a smallish PCB). Tiltmeters would be
added, and the PIC would provide stability (with tiltmeters?)- but my
problem at the moment is determining which fan to use - 5,12,24VDC? What
sort of CFM (cubic feet/minute) would I need (there would be say 4 fans, one
in each corner)? What would be the best battery supply, rechargable NiCd?
How could a PIC vary the supplied voltage (current?) to the fans to change
the speed? Or should I just use a relay (the fans would run off their own
power supply, I assume).
Kieren Johnstone wrote:
> I want to find out the best way (using fans) to lift my project (quite
> light, just the weight of the fans, a smallish PCB).
> Tiltmeters would be added, and the PIC would provide
> stability (with tiltmeters?)- but my problem at the moment
> is determining which fan to use - 5,12,24VDC? What
> sort of CFM (cubic feet/minute) would I need (there would be
> say 4 fans, one in each corner)? What would be the best battery
> supply, rechargable NiCd?
> How could a PIC vary the supplied voltage (current?) to the
> fans to change
> the speed? Or should I just use a relay (the fans would run
> off their own power supply, I assume).
Kieren Johnstone wrote some days earlier:
> I've already drawn up a checklist / shopping list for my
> introduction to PIC / electronics.
Kieren,
Why not moon project to start with.
Read Russell's "[OT]: How to suceed in a pioneering enterprise" for inspiration.
>
> Kieren Johnstone wrote:
> > I want to find out the best way (using fans) to lift my project (quite
> > light, just the weight of the fans, a smallish PCB).
> > Tiltmeters would be added, and the PIC would provide
> > stability (with tiltmeters?)- but my problem at the moment
> > is determining which fan to use - 5,12,24VDC? What
> > sort of CFM (cubic feet/minute) would I need (there would be
> > say 4 fans, one in each corner)? What would be the best battery
> > supply, rechargable NiCd?
> > How could a PIC vary the supplied voltage (current?) to the
> > fans to change
> > the speed? Or should I just use a relay (the fans would run
> > off their own power supply, I assume).
>
> Kieren Johnstone wrote some days earlier:
> > I've already drawn up a checklist / shopping list for my
> > introduction to PIC / electronics.
>
> Kieren,
>
> Why not moon project to start with.
> Read Russell's "[OT]: How to suceed in a pioneering
> enterprise" for inspiration.
>
> Mike.
In other words, you're in way over your head.
While you might be able to find a fan that can lift itself with it's
own output force, you'll never find one that can also directly lift the battery.
(BTW higher voltage tends to be more efficient with the control electronics).
You'll also have to deal with how you provide counter force to the torque the
lifting fan produces. IOW how to keep the platform from spinning.
You might want to look at electric powered model aircraft to get an
idea of the kind of motors and power/weight ratios you need. They
are also not cheap.
Your most workable alternative
is to use a 'lighter than air' gas as your primary lift force, and use
several fans to steer/control it. Look for 'electric blimp' for a starting
point.
Good luck with this most challenging project. Why start simple eh??
Very few off the shelf 'fans' will lift their own weight let alone their
power supply.
You need to think in terms of propellers with very powerful lightweight
motors. Your local hobby shop will have the motors and propellers you need.
You might also consider going with two or more smaller props and motors.
This has the advantage of not needing to worry too much about the motor
spinning the project instead of the propeller, and a simple moving
scheme could be putting more power to one of the motors than another.
Make a model that is wired to a handheld controller so you can get an
idea of how difficult they are to control and maneuver.
>Hi,
>
>I want to find out the best way (using fans) to lift my project (quite
>light, just the weight of the fans, a smallish PCB). Tiltmeters would be
>added, and the PIC would provide stability (with tiltmeters?)- but my
>problem at the moment is determining which fan to use - 5,12,24VDC? What
>sort of CFM (cubic feet/minute) would I need (there would be say 4 fans, one
>in each corner)? What would be the best battery supply, rechargable NiCd?
>How could a PIC vary the supplied voltage (current?) to the fans to change
>the speed? Or should I just use a relay (the fans would run off their own
>power supply, I assume).
>
>Thanks..any help apprecited
>
>-Kieren
>
>--
>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
>email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body
>
>
>
>
>
>
>
It is pressure, not CFM, that provides the energy to lift.
Look for high pressure, I know the Rotron biscuit blowers, are pretty good.
The other key is surface area. One blower with sufficient throughput to a large recess
can provide a lot of force.
A small recess, .050" , but large area, can provide a lot of upward force.
I haven't done the math to investigate how long your hovercraft will float on typical
batteries, but it can be done.
It will only be thousandths of an inch off the ground, so I hope you weren't looking for
helicopter type activity, because I have seen electric helicopters in action and it is not a
pretty site.
> Very few off the shelf 'fans' will lift their own weight let alone their
> power supply.
>
> You need to think in terms of propellers with very powerful lightweight
> motors. Your local hobby shop will have the motors and propellers you need.
>
> You might also consider going with two or more smaller props and motors.
> This has the advantage of not needing to worry too much about the motor
> spinning the project instead of the propeller, and a simple moving
> scheme could be putting more power to one of the motors than another.
> Make a model that is wired to a handheld controller so you can get an
> idea of how difficult they are to control and maneuver.
>
> Good luck!
>
> -Adam
>
> Kieren Johnstone wrote:
>
> >Hi,
> >
> >I want to find out the best way (using fans) to lift my project (quite
> >light, just the weight of the fans, a smallish PCB). Tiltmeters would be
> >added, and the PIC would provide stability (with tiltmeters?)- but my
> >problem at the moment is determining which fan to use - 5,12,24VDC? What
> >sort of CFM (cubic feet/minute) would I need (there would be say 4 fans, one
> >in each corner)? What would be the best battery supply, rechargable NiCd?
> >How could a PIC vary the supplied voltage (current?) to the fans to change
> >the speed? Or should I just use a relay (the fans would run off their own
> >power supply, I assume).
> >
> >Thanks..any help apprecited
> >
> >-Kieren
> >
> >--
> >http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> >email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body
> >
> >
> >
> >
> >
> >
> >
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
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>
>
I once put about an 8 inch hobby prop on the type of motor that is found in
cordless drills
running on 12v tetherd to a power supply it had alot of lifting power more
than enough
to lift the motor with a few pieces of coat hanger wire as legs the motor
would start
to counter spin before it even got off the ground the motor used alot of
current
so if I had found batteries light enough for it to lift (and fixed the
counter rotation problem)
the thing would not fly for long on a charge
any how. I think electric hobby helicopters only fly for a few minutes a
better power source
is a model gas engine for energy to weight. or the lighter than air idea
sounds good to I
may do more experimenting myself with that idea.
Hope this helps
JIm
>Hi,
>
>I want to find out the best way (using fans) to lift my project (quite
>light, just the weight of the fans, a smallish PCB). Tiltmeters would be
>added, and the PIC would provide stability (with tiltmeters?)- but my
>problem at the moment is determining which fan to use - 5,12,24VDC? What
>sort of CFM (cubic feet/minute) would I need (there would be say 4 fans, one
>in each corner)? What would be the best battery supply, rechargable NiCd?
>How could a PIC vary the supplied voltage (current?) to the fans to change
>the speed? Or should I just use a relay (the fans would run off their own
>power supply, I assume).
>
>Thanks..any help apprecited
>
>-Kieren
>
>--
>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
>email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body
That "gizmocopter" was *just* what I was talking about. If I didn't see that theres a team of (literally) near-rocket scientists still saying "Let us get it flying first!" (see the FAQ!), I might have been more encouraged. Well, thanks for all the responses guys, I suppose I should get the LED flashing :(. I spent £60 (~$90) on stuff to get me started on Saturday - wire tools, wire, multimeter, storage, components, breadboard. Means I can't afford a PIC programmer yet *sob*. (Note: I would build one, but I haven't found any that are quoted to work with a 16F877, what I hope to use in the long-run).
> These guys look like they have it figured out....
> http://www.gizmocopter.org/
>
> This uses embedded linux, but I bet a PIC could do it.
Interestingly, that's principally a rocketry group, also tentatively aiming
at the X Prize that I mentioned in the John Carmack "how to succeed ..."
context. John is not a member of the group per se (I think) but they are in
regular contact and he posts his status report pointers to their list.
Their main thrust (pun not intended) at this stage is Hydrogen Peroxide
(HTP) mono-propellant rockets, as is John's. At some stage both will
probably graduate to bipropellant motors with HTP as the oxidiser. It's more
or less competitive with LOX at concentrations approaching 100%. John has
some biprop motors running already but fairly small compared to his current
main engines (which are capable of lifting a person).
Is it possible to have 4 fans on the 4 corners of a platform facing down/up
and spining them in separate directions ie the fans diagonaly opposed
spining the same direction and the fans opposite spining opposite. The
direction and control could be achieved varying the speed of 2 fans.
I appreciate the difficulties in getting some control but it should be fun
trying to keep out of its way.
Justin
{Original Message removed}
> Is it possible to have 4 fans on the 4 corners of a platform facing
down/up
> and spining them in separate directions ie the fans diagonaly opposed
> spining the same direction and the fans opposite spining opposite. The
> direction and control could be achieved varying the speed of 2 fans.
>
> I appreciate the difficulties in getting some control but it should be fun
> trying to keep out of its way.
It certainly is.
But getting fans with "opposite" blades would be harder. Most fans of a
given type will have the same rotation. I have not ever thought about which
way fans turn but odds are the whole industry does it the same (Murphy
says).
Also, with 4 distributed fans I feel the affect of all one way torque may be
less (but this sounds like heresy).
Various 'copters have been built with counterrotating rotors - the 1st
really successful one was the twin rotor pre WW2 Focke Wulfe FW61 famously
flown in 1936 by female test pilot Hanna Reitsch inside the Deutschlandhalle
sports stadium in Berlin.
On Mon, 15 Jul 2002 07:00:00 +0100, Kieren Johnstone wrote:
>:(. I spent £60 (~$90) on
>stuff to get me started on Saturday - wire tools, wire, multimeter,
>storage, components, breadboard. Means I can't afford a PIC
>programmer yet *sob*. (Note: I would build one, but I haven't found
>any that are quoted to work with a 16F877, what I hope to use in the
>long-run).
Hi Kieren, the P16Pro40 with Nigel Pilsley's WinPicProg software
should program the 16F877 (according to the docs I've got for both).
You can get the P16Pro40 in the UK from http://www.quasarelectronics.com/pic_programmers.htm - the kit is
£10.95 (add £15 if you want a 40 pin zif)
>
> > Is it possible to have 4 fans on the 4 corners of a platform facing
> down/up
> > and spining them in separate directions ie the fans diagonaly opposed
> > spining the same direction and the fans opposite spining opposite. The
> > direction and control could be achieved varying the speed of 2 fans.
> >
> > I appreciate the difficulties in getting some control but it should be fun
> > trying to keep out of its way.
>
> It certainly is.
> But getting fans with "opposite" blades would be harder. Most fans of a
> given type will have the same rotation. I have not ever thought about which
> way fans turn but odds are the whole industry does it the same (Murphy
> says).
>
> Have a look at the gizmo copter to see what they do.
> Note that the motors draw 96 amps :-)
> Gizmo copter home page
> http://www.gizmocopter.org/
> Copter
> http://www.gizmocopter.org/elj-contest-200108/
> ERPS home page
> http://www.erps.org/
> Join ERPS list
> http://cube.erps.org/email/join.html
>
> Also, with 4 distributed fans I feel the affect of all one way torque may be
> less (but this sounds like heresy).
Umm, isn't the torque issue only valid upon one
axis? If you have a helicopter with 2 "fans" they
don't have to spin in opposite directions, provided
the fans are located apart from each other (like a
Chinook).
Vertical designs like the Osprey use fans that rotate
in the same direction. :o)
Contra-rotating blades are only really needed when
you have both fans on the one axle, which is perfectly
valid for some designs.
I have fiddled with some designs for a little "spy in the
sky" type unit, with two fans, one front and one back with
a small combustion engine (vert shaft) and a lightweight
toothed belt to drive both fans. Very light. Simple RC
servo operated vanes under the fans give yaw and pitch etc.
gets rid of most of the helicopter stability problems and
would even be usable in buildings etc. I wish I had more
time, sigh.
-Roman
PS. Gizmocopter appears to have standard rotating props,
ie all 4 in same direction. Most of the RC props i've seen
have been clockwise.
> -----Original Message-----
> From: pic microcontroller discussion list
> [RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Gwynne Reddick
> Sent: Monday, July 15, 2002 4:18 AM
> To: EraseMEPICLISTspamspamBeGoneMITVMA.MIT.EDU
> Subject: Re: [EE]: Fans for lifting (flying)
>
>
> On Mon, 15 Jul 2002 07:00:00 +0100, Kieren Johnstone wrote:
>
> >:(. I spent #60 (~$90) on
> >stuff to get me started on Saturday - wire tools, wire, multimeter,
> >storage, components, breadboard. Means I can't afford a PIC
> >programmer yet *sob*. (Note: I would build one, but I haven't found
> >any that are quoted to work with a 16F877, what I hope to use in the
> >long-run).
>
> Hi Kieren, the P16Pro40 with Nigel Pilsley's WinPicProg software
> should program the 16F877 (according to the docs I've got for both).
> You can get the P16Pro40 in the UK from
> http://www.quasarelectronics.com/pic_programmers.htm - the kit is
> #10.95 (add #15 if you want a 40 pin zif)
>
> Gwynne
> --
> Gwynne Reddick, RemoveMEgwynneKILLspammememachines.net on 15/07/2002
>
> --
> http://www.piclist.com hint: To leave the PICList
> piclist-unsubscribe-requestSTOPspamspam_OUTmitvma.mit.edu
>
>
> Umm, isn't the torque issue only valid upon one
> axis?
No. Torques on a rigid body are simply summed (as vectors, of course).
Therefore, all four props spinning the same direction will exert a net
torque on the frame.
> If you have a helicopter with 2 "fans" they
> don't have to spin in opposite directions, provided
> the fans are located apart from each other (like a
> Chinook).
This is complete balderdash. Go back to freshman physics and do the
analisys.
Actually I thought the Chinook did have counter rotating fans. If not, it
must have some other means to equalize the net torque on the airframe.
*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
> > If you have a helicopter with 2 "fans" they
> > don't have to spin in opposite directions, provided
> > the fans are located apart from each other (like a
> > Chinook).
>
> This is complete balderdash. Go back to freshman physics and do the
> analisys.
>
> Actually I thought the Chinook did have counter rotating
> fans. If not, it
> must have some other means to equalize the net torque on the airframe.
>
> > Umm, isn't the torque issue only valid upon one
> > axis?
>
> No. Torques on a rigid body are simply summed (as vectors, of course).
> Therefore, all four props spinning the same direction will exert a net
> torque on the frame.
>
> > If you have a helicopter with 2 "fans" they
> > don't have to spin in opposite directions, provided
> > the fans are located apart from each other (like a
> > Chinook).
>
> This is complete balderdash. Go back to freshman physics and do the
> analisys.
>
> Actually I thought the Chinook did have counter rotating fans. If not, it
> must have some other means to equalize the net torque on the airframe.
>
> *****************************************************************
> Embed Inc, embedded system specialists in Littleton Massachusetts
> (978) 742-9014, http://www.embedinc.com
>
> --
> http://www.piclist.com hint: To leave the PICList
> @spam@piclist-unsubscribe-request@spam@spam_OUTmitvma.mit.edu
Pookie being a dog, she knows this one.
Bill
******************
I had a friend that had two tails. When he wagged
them, they would both go in the same direction.
Sometimes clock wise, some times counter clock
wise (as viewed from the tail end).
When he got excited and his tails would start
wagging, he would start chassing them. The
direstion he turned to chase them would always
depend on which way his tails were wagging.
Bill would make money by betting on which way he,
my excited dog friend would torque.
Something to note: Any tait-style programmer will program an F877
(provided it has a big enough socket, of course). With that noted,
tait style programmers consist of a chip 2 transistors and a handful
of resistors. Look up
www.piclist.com/techref/microchip/devprogs.htm
and look at the David Tait section.
These are close to the simplest HVPs(high voltage programmer) around.
Byron has a simpler LVP(low voltage programmer) called TLVP, but LVP
has some disadvantages at the moment, involving the loss of io pins.
All together, the parts shouldn't cost you more than about $10 with
the price of a DB-25 connector (for the parallel port), backshell and
a short cable. (It's cheaper to wire the cable youself than to buy
one).
There are lots of tutorials and instructions for the Tait-style
programmers available on the web. For software, if you use windows,
I recomend FPP.
I have a friend who claims to have made a simple hovercraft as a stunt. It
was designed to lift the wieght of a kid. Apparently he took an industrial
strength shop vac blower, and arranged it to inflate a skirt made of plastic
and duct tape. With 200' of 120V cord backed up by a 175' rope to keep the
tension off, he would let kids ride it around his back yard. i got this
story from others who claimed to have seen it, so I tend to believe it.
Seems like this would be a fun stunt to duplicate.
On Mon, 15 Jul 2002 13:36:34 -0500, Lawrence Lile wrote:
>I have a friend who claims to have made a simple hovercraft as a
>stunt. It was designed to lift the wieght of a kid. Apparently he
>took an industrial strength shop vac blower, and arranged it to
>inflate a skirt made of plastic and duct tape. With 200' of 120V
>cord backed up by a 175' rope to keep the tension off, he would let
>kids ride it around his back yard. i got this story from others who
>claimed to have seen it, so I tend to believe it.
>Seems like this would be a fun stunt to duplicate.
I have seen one like this at the St. Louis Children's Museum years ago.
They were using theirs indoors on a tile floor.
>Hi,
>
>I want to find out the best way (using fans) to lift my project (quite
>light, just the weight of the fans, a smallish PCB). Tiltmeters would be
>added, and the PIC would provide stability (with tiltmeters?)- but my
>problem at the moment is determining which fan to use - 5,12,24VDC? What
>sort of CFM (cubic feet/minute) would I need (there would be say 4 fans, one
>in each corner)? What would be the best battery supply, rechargable NiCd?
>How could a PIC vary the supplied voltage (current?) to the fans to change
>the speed? Or should I just use a relay (the fans would run off their own
>power supply, I assume).
>Very few off the shelf 'fans' will lift their own weight let alone their
>power supply.
Unless you drop some pimento into the power supply and allow for a life
measured in hours, and flights measured in minutes.
>You need to think in terms of propellers with very powerful lightweight
>motors. Your local hobby shop will have the motors and propellers you need.
;-)
>You might also consider going with two or more smaller props and motors.
> This has the advantage of not needing to worry too much about the motor
>spinning the project instead of the propeller, and a simple moving
>scheme could be putting more power to one of the motors than another.
> Make a model that is wired to a handheld controller so you can get an
>idea of how difficult they are to control and maneuver.
>I have a friend who claims to have made a simple hovercraft as a stunt. It
>was designed to lift the wieght of a kid. Apparently he took an industrial
>strength shop vac blower, and arranged it to inflate a skirt made of plastic
>and duct tape. With 200' of 120V cord backed up by a 175' rope to keep the
>tension off, he would let kids ride it around his back yard. i got this
>story from others who claimed to have seen it, so I tend to believe it.
>Seems like this would be a fun stunt to duplicate.
If you have a strong (~2hp) leaf/snow blower you can duct it directly into
the middle a piece of 3/4" 1m x 1.5m fiberboard with a hole in the middle
and ride it on a flat surface (concrete). You need to adjust the load so
it is evenly spread. The thing works on slightly different principles than
a hovercraft but it requires less air to operate. I once saw similar
equipment used to move large items in a warehouse in a science tv program.
The 'wing loading' is about 700grams/dm^2 with 100kg of load. Note that
these strong blowers are not handheld usually, they are the wheelbarrow
type I think.
Olin said
>>This is complete balderdash. Go back to freshman physics and do the
>>analisys.
Roman had earlier posted
Try:
If (abearing1 - sbearing1) >58
Those little () let YOU tell the micro which order
to do things in. :o)
Darn, i'm sounding like Olin... ;o)
-Roman
and I remarked
... and Roman thought He was begining to sound like Olin ? ;)
Just a small attempt at humor. I will stop taking up bandwidth now.
Olin Lathrop wrote:
>
> > Umm, isn't the torque issue only valid upon one
> > axis?
>
> No. Torques on a rigid body are simply summed (as vectors, of course).
> Therefore, all four props spinning the same direction will exert a net
> torque on the frame.
>
> > If you have a helicopter with 2 "fans" they
> > don't have to spin in opposite directions, provided
> > the fans are located apart from each other (like a
> > Chinook).
>
> This is complete balderdash. Go back to freshman physics and do the
> analisys.
>
> Actually I thought the Chinook did have counter rotating fans. If not, it
> must have some other means to equalize the net torque on the airframe.
Whoops! Looks like I got it wrong (again!).
I did know the Chinook had contra fans but would
have sworn the Osprey didn't. But yes you are correct,
they both do.
Sigh, when will I ever learn? One good thing came from
this, I went to the RC aeroplane shop today, the counter
propellors are available, but not in all sizes. So I can
revise my design for 2 fans, contra rotating. The good
thing I found is that I can "figure-8" my toothed belt,
with a small slider of teflon where it crosses over.
That way I get both fans contra rotating with one
engine, and still no weight penalty as I have only the
2 pulleys and one toothed belt. I suppose discoveries
come from all stuff-ups...
-Roman (call me freshman boy)
-- http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
Kevin A. Benedict wrote:
>
> >This is complete balderdash. Go back to freshman physics and do the
> >analisys.
>
> ... and Roman thought he was begining to sound like Olin ? ;)
Actually I take that back, i'm going to have to
practice being REAL grumpy and intolerant before
I get my Olin impersonation down pat. (Joke) ;o)
-Roman
-- http://www.piclist.com hint: PICList Posts must start with ONE topic:
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>
> Note *************
>
> Pookie being a dog, she knows this one.
> Bill
> ******************
>
> I had a friend that had two tails. When he wagged
> them, they would both go in the same direction.
> Sometimes clock wise, some times counter clock
> wise (as viewed from the tail end).
>
> When he got excited and his tails would start
> wagging, he would start chassing them. The
> direstion he turned to chase them would always
> depend on which way his tails were wagging.
>
> Bill would make money by betting on which way he,
> my excited dog friend would torque.
>
> Pookie
-- http://www.piclist.com hint: PICList Posts must start with ONE topic:
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> One good thing came from
> this, I went to the RC aeroplane shop today, the counter
> propellors are available, but not in all sizes. So I can
> revise my design for 2 fans, contra rotating. The good
> thing I found is that I can "figure-8" my toothed belt,
> with a small slider of teflon where it crosses over.
> That way I get both fans contra rotating with one
> engine, and still no weight penalty as I have only the
> 2 pulleys and one toothed belt.
You could mount the motor at a right angle to both axes instead of parallel
to them. That way you would need a 90 degree twist in each belt instead of
no twist in one and 180 degrees in the other. With a 90 degree twist you
may not need the teflon spacer since the opposite sides of the belt
hopefully won't touch where they cross.
*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
-- http://www.piclist.com hint: PICList Posts must start with ONE topic:
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Roman Black wrote:
> RC aeroplane shop today, the counter
> propellors are available, but not in all sizes. So I can
> revise my design for 2 fans, contra rotating.
> That way I get both fans contra rotating with one
> engine, and still no weight penalty as I have only the
> 2 pulleys and one toothed belt.
It is only part of the problem solved. Counter rotating
will only get you in the ball park in solving torque problems
almost any flight attitude will alter the amount of torque
each fan will contribute. Ground effects and turbulence
are big issues.
w..
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What type of props will you be using? The model airplane
ones are designed for efficiency at higher speeds, and
the helicopter ones are quite large, though designed for
low (travel) speeds. So I'm curious which ones you're
looking at.
Cheers,
-Neil.
-----Original Message-----
> One good thing came from
> this, I went to the RC aeroplane shop today, the counter
> propellors are available, but not in all sizes.
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Olin Lathrop wrote:
>
> > thing I found is that I can "figure-8" my toothed belt,
> > with a small slider of teflon where it crosses over.
> > That way I get both fans contra rotating with one
> > engine, and still no weight penalty as I have only the
> > 2 pulleys and one toothed belt.
>
> You could mount the motor at a right angle to both axes instead of parallel
> to them. That way you would need a 90 degree twist in each belt instead of
> no twist in one and 180 degrees in the other. With a 90 degree twist you
> may not need the teflon spacer since the opposite sides of the belt
> hopefully won't touch where they cross.
Thanks Olin, that is a GREAT idea! Originally I
was set on having vertical mount motor and one prop
on the motor, with one belt and 2 simple pulleys to
give the 2 toal props for VTOL.
Having talked with the RC 'plane guy, it might be
better to use a gearing belt and go 2:1 to 3.5:1
so I can use larger props. Your idea to put the motor
in the middle has penalty of one more prop shaft
mount, and the 2 small pulleys on the motor, but
advantages of less belt twist and can give easy
gearing, even with changes, provided I have some
horiz adjustment in the motor mounts.
It's not a rush, this has been one of those "play
think" type ideas for months now... :o)
-Roman
Walter Banks wrote:
>
> Roman Black wrote:
> > RC aeroplane shop today, the counter
> > propellors are available, but not in all sizes.
>
> It is only part of the problem solved. Counter rotating
> will only get you in the ball park in solving torque problems
> almost any flight attitude will alter the amount of torque
> each fan will contribute. Ground effects and turbulence
> are big issues.
Thanks Walter, have you any experience in designs
of this type (ie fixed pitch 2x simple props etc)??
I was thinking of using some fast closed loop controls
and some servo operated vanes to give yaw/pitch etc.
Funny coincidence the RC 'plane guy had flown a dual
prop prototype for one of the universities here, he
was describing some of the flight problems they had
to me when I was in his shop. Nice, buy, when i'm
spending $250 bucks in there i'll try and get him
chatting for a while! ;o)
-Roman
Pic Dude wrote:
>
> What type of props will you be using? The model airplane
> ones are designed for efficiency at higher speeds, and
> the helicopter ones are quite large, though designed for
> low (travel) speeds. So I'm curious which ones you're
> looking at.
Yep, looking at about 12 inch props now, they are
available in both types. They're a bit large for
the 2.5cc motor, so looking at going to larger motor
and some simple toothed belt gearing about 3:1
probably. Should be good for 6+ pounds thrust,
allowing 40% overhead for some ducting and losses
a total model weight of 4 pounds seems quite do-able.
One problem they seem to be having with VTOL is that
the petrol engine units are harder to control than
the electric because of slower engine response. I
think it's possible to use some type of fast actuator
and simple ducting to speed things up.
-Roman
Roman Black wrote:
>
> Walter Banks wrote:
> >
> > Roman Black wrote:
> > > RC aeroplane shop today, the counter
> > > propellors are available, but not in all sizes.
> >
> > It is only part of the problem solved. Counter rotating
> > will only get you in the ball park in solving torque problems
> > almost any flight attitude will alter the amount of torque
> > each fan will contribute. Ground effects and turbulence
> > are big issues.
>
> Thanks Walter, have you any experience in designs
> of this type. I was thinking of using some fast closed
> loop controls and some servo operated vanes to give
> yaw/pitch etc.
>
I would think that you would need some flow straighteners
in the airflow from the prop's. After that you probably
can control the torque with a servo and vane in slipstream
of one of the one of the fans. Model helicopter gyro's
can likely be used to stabilize the flight platform.
A lot of years ago we built a bunch of powered free flight
helicopters of different designs looking at stability issues.
Later I built a RC helicopter. The RC helicopter was much
harder to fly than the real thing.
>Yep, looking at about 12 inch props now, they are
>available in both types. They're a bit large for
>the 2.5cc motor, so looking at going to larger motor
>and some simple toothed belt gearing about 3:1
>probably. Should be good for 6+ pounds thrust,
>allowing 40% overhead for some ducting and losses
>a total model weight of 4 pounds seems quite do-able.
A 2.5cc does not pull 4lbs. It pulls about 2x its own weight max. I'd be
interested to find out otherwise.
> Means I can't afford a PIC programmer yet *sob*. (Note: I would build
one, but I haven't found any that are quoted to work with a 16F877, what I
hope to use in the long-run).
Did you really look around? Check my http://www.voti.nl/wisp628 (~ $28 for a
kit, I will set up a 'shop' page next week, but the full design is also
available for DIY):
The following target chips are currently supported: 16c84, 16f84, 16f84a
16f627 (untested), 16f628
16f73, 16f74, 16f76, 16f77
16f870, 16f871, 16f872, 16f873, 16f874, 16f876, 16f877
(I am working on 18F's, and 16f87xA's will be added soon)
And I seriously can not imagine that this is the only one....
BTW if you want 16f877 you could buy the chip programmed with a bootloader:
no programmer needed, just a max232. See http://www.voti.nl/wloader , I sell the
programmed chip, but the full details are also avaialbel for DIY. And I am
sure I am not the only that does.
Wouter van Ooijen
--
Van Ooijen Technische Informatica: http://www.voti.nl
Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen
mitvma.mit.edu with SET PICList DIGEST in the body
