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'[OT]: Building a Servo'
2001\08\08@155006 by Jeff DeMaagd

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----- Original Message -----
From: John Ferrell <spam_OUTjohnferrellTakeThisOuTspamSPRINTMAIL.COM>


> A most interesting project. BTW, it is against the law in the US to use
the
> airplane frequencies for surface RC.

I've always wondered about this, can anyone give me the rationale for having
such regulation?  Are the frequencies chosen for certain propagation
properties and should be avoided for certain uses?  Or do they like to make
rules to justify their jobs?

Jeff

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2001\08\08@155809 by t F. Touchton

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Acutally... it is for safety.  Decent sized model airplanes can kill.   I
have a friend that flys 1/4 scale... 3' diameter prop and a chainsaw
engine.  It can take a few people out in a crowd.

I guess they don't care about people's feet getting run over...

Scott F. Touchton
1550 Engineering Manager
JDS Uniphase



                   Jeff DeMaagd
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2001\08\08@160456 by Don Hyde

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No.  There's logic behind it.

A crashing model aircraft is more dangerous than a crashing model car.
Model cars are sold as kid's toys.  It's better that a kid playing with a
car not be able to accidentally crash a model airplane that might be just
out of sight on the other side of the park.

Putting the two on different frequencies reduces the likelyhood of people
accidentally hurting each other.

> {Original Message removed}

2001\08\08@160816 by David VanHorn

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>
>I've always wondered about this, can anyone give me the rationale for
>having
>such regulation?  Are the frequencies chosen for certain propagation
>properties and should be avoided for certain uses?  Or do they like to make
>rules to justify their jobs?

Imagine an airfield and a car track.
Not likely to be at the same place, right?
So a guy takes off, using the same freq as you are.
Initally, when he's close in, he isn't getting your controller, even with
his off, because the model is close to the ground, and your 1W dosen't
propagate all that far at ground level.
So he climbs up, and goes twoard the car track (not knowing)
At some point, your controller overrides his, and you are now controlling
his plane, but not likely in a manner that will be good for the plane.
And you have no idea it's happening.

He'll never bother your car, though, for the same reasons that you didnt'
bother his plane on the ground.

So, separate frequencies.

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2001\08\08@161445 by Max Toole

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In a message dated 8/8/2001 3:50:58 PM Eastern Daylight Time,
jeffspamspam_OUTDEMAAGD.COM writes:

<< I've always wondered about this, can anyone give me the rationale for
having
such regulation?  Are the frequencies chosen for certain propagation
properties and should be avoided for certain uses?  Or do they like to make
rules to justify their jobs?

Jeff >>
The reason is so that someone with a model car doesn't shoot down someones
airplane.  As a radio control model airplane enthusiast for 40 years, I can
really appreciate it.

Max

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2001\08\08@163236 by John Ferrell

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The effective range of the popular equipment is considered to be short
enough that the prevailing authority in the US (Academy of Model Aviation)
approves fields as close as three miles apart. Model airplanes can be quite
expensive. The Aerobatic competitors spend an average of well over $2000 on
an airplane. That figure won't even buy a turbine for a model jet. The
surface equipment user can be totally unaware of shooting down these
airplanes. There are channels at 72 mhz for aircraft and 75 mhz for surface.
The RC channels on the Ham bands are in the six meter band and are
undesignated.

There has been at least one patent granted on the 900mhz area for spread
spectrum that would probably solve all of the interference problems. Getting
manufacturers and users will be as hard as getting the allocation.

To compound things, there are "Park Flyers" which are small electric
airplanes that are coming on the scene on the same frequencies. Yes, they
have every right to be there.

Out of control RC airplanes don't normally go far before crashing. The
biggest safety concern is interference in the pit area where a model may be
unrestrained when interference brings it to full throttle.  A popular YS1.20
four stroke engine produces around four horsepower turning a sixteen inch
propeller.

John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"



{Original Message removed}

2001\08\08@170840 by James R. Cunningham

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It's to keep the surface use from causing loss of control of an in-flight
aircraft, which could then whack someone on top of the head.  Sounds like a
reasonable prohibition to me.

Jim

Jeff DeMaagd wrote:

> -against the law in the US to use the airplane frequencies for surface RC.
>
> I've always wondered about this, can anyone give me the rationale for having
> such regulation?

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2001\08\08@171632 by Dale Botkin

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On Wed, 8 Aug 2001, John Ferrell wrote:

> Out of control RC airplanes don't normally go far before crashing. The
> biggest safety concern is interference in the pit area where a model may be
> unrestrained when interference brings it to full throttle.  A popular YS1.20
> four stroke engine produces around four horsepower turning a sixteen inch
> propeller.

I've had smaller lawnmowers.  Even a small engine and prop can be quite
exciting -- ask me about how I know that a .30 with a six-inch nylon prop
can make hamburger out of a perfectly good thumb.  I've still got the
scars, that was something like '73 or '74.  I think I've still got the
engine, too...

Dale
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On my desk I have a workstation...

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2001\08\08@204111 by Larry Williams

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Don't you imagine that if this is so, it would be to prevent a model airplane from crashing into someone.  Some kiddie (or adult idiot) playing with his toy car with enough power , and the transmitter will affect a plane at a larger distance than it will the car, could hurt someone if his controller took control of an airplane.  He could run the plane that he doesn't even see into someone or possibly even a full size aircraft, crash it into a crowd of people, the possiblities are endless.
> > A most interesting project. BTW, it is against the law in the US to use
> the
> > airplane frequencies for surface RC.
>
> I've always wondered about this, can anyone give me the rationale for having
> such regulation?  Are the frequencies chosen for certain propagation
> properties and should be avoided for certain uses?  Or do

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2001\08\09@194343 by Herbert Graf

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> As far as the spark jumping the relay gap (if for some reason you cannot
> gain access to a low voltage section of the circuit) you could
> use more than
> one contact/relay: wiring the contacts in series will quickly
> reach a "safe"
> distance...

       True, that is something to consider.

> Other thoughts;
>   * is there an air intake (or exhaust) port that could be
> blocked? doing so
> could do the job.

       Yes, this is a possibility, but I'd love to do it with as few moving parts
as possible! :)

>   * how about interrupting the mechanical coupling between the wheels and
> the engine?

       Nope, it's a direct connection (there is a cenralfugal (sp?) clutch but it
cannot be controlled)

>   * for really fast stopping of the engine you could cause the
> piston/cylinder to try to act on something less compressible -
> such as water
> by using a car windshield washer fluid pump with a small
> reservoir and hose
> directed into the intake... though this might be too drastic.

       An interesting idea, but I'd rather not pour water in unless I have to! :)

>   * you might want to reconsider changing the steering wheel
> direction as a
> fail-safe - would be messy if it intermittently activated while moving at
> speed in close quarters or near people... I'd lock the wheels
> as-is until a
> valid steering signal is received...

       Actually this is already planned, in the case of transmitter contact loss
the steering will steer all the way to one direction, haven't decided which,
flip of a coin perhaps? :) Thanks for the suggestions. TTYL

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2001\08\10@120533 by Jeff DeMaagd

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----- Original Message -----
From: Mike Mansheim <RemoveMEMichael_J_MansheimspamTakeThisOuTGRACO.COM>
>
> The air intakes on this car are apparently quite low to the ground.

A lot of new cars are "bottom breathers".  Even if it looks like they can
take air from the front grill, often the grill is fake and even the air for
the radiator is sometimes taken from the below the bumper.

Jeff

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2001\08\10@130539 by Mike Mansheim

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> A lot of new cars are "bottom breathers".  Even if it looks like they
> can take air from the front grill, often the grill is fake and even the
> air for the radiator is sometimes taken from the below the bumper.

Exactly - and because of the severe consequences of the engine ingesting
water, someone with a 'bottom breathing' car needs to avoid driving
through or into standing water.

Sorry about not changing the topic tag on previous post...

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2001\08\11@043700 by Peter L. Peres

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> A lot of new cars are "bottom breathers".  Even if it looks like they
> can take air from the front grill, often the grill is fake and even
> the air for the radiator is sometimes taken from the below the bumper.

Is this to ensure that they do not last very long by breathing all the
dirt there is, or is it an attempt to use the higher static pressure under
the car when driving faster (than allowed) to improve engine efficiency ?

Peter

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2001\08\11@050246 by James R. Cunningham

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Naw, it's an attempt to use the high temperature air near the road surface to
reduce engine efficiency. :-)

Peter L. Peres wrote:

> >, or is it an attempt to use the higher static pressure under
> the car when driving faster (than allowed) to improve engine efficiency ?

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2001\08\11@102106 by Dale Botkin

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On Sat, 11 Aug 2001, Peter L. Peres wrote:

> > A lot of new cars are "bottom breathers".  Even if it looks like they
> > can take air from the front grill, often the grill is fake and even
> > the air for the radiator is sometimes taken from the below the bumper.
>
> Is this to ensure that they do not last very long by breathing all the
> dirt there is, or is it an attempt to use the higher static pressure under
> the car when driving faster (than allowed) to improve engine efficiency ?

I suspect it's purely a matter of styling.  I'd bet it's one of those
things the designers decide and engineers grumble about.

Dale
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2001\08\11@104432 by Jim

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Even though they may appear to be 'bottom
breathers', the air-intake (for combustion air as
opposed to cooling air/radiator air) is still usually
taken from one of the upper most 'slits' via a scoop
and appropriate tubing to the air cleaner/filter with
the next stop being the airmass flow sensor/throttle
plate assembly ...

Jim


{Original Message removed}

2001\08\13@131525 by Mike Mansheim

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> Even though they may appear to be 'bottom
> breathers', the air-intake (for combustion air as
> opposed to cooling air/radiator air) is still usually
> taken from one of the upper most 'slits' via a scoop
> and appropriate tubing to the air cleaner/filter with
> the next stop being the airmass flow sensor/throttle
> plate assembly ...

I think we've come full circle.  The original point was that even though
many newer cars appear to have conventional air intakes, they are
actually 'bottom breathers', as evidenced by their ability to ingest
water, with deleterious effects on the engine.

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