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Old Feb 17, 2012, 04:54 AM
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Australia, NSW, Sydney
Joined Jul 2011
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So... What do you think?

Well... I think this may be my final blueprint.

This.. thing.. is a sort of wind powered car (for the moment...)

Do you think it will work?

Do you think there will be enough power? ( 3x 2200kv Motors, 7x4 props )

Do you think the rudders will work?

What sort of wheel configuration should I have? (
Quote:
Originally Posted by Lnagel View Post
Besides the rudders you will also need a pivot point for the undercarriage. The farther the pivot point is from the propellers, the more effective the rudders will be. I would suggest a tricycle arrangement with a single fixed front wheel (acts as the pivot point) and two castoring rear wheels.

Larry
All my ideas from RC Groups...

Thanks
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Old Feb 17, 2012, 11:10 PM
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Wintr's Avatar
USA, MO, Florissant
Joined Nov 2010
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For the castoring wheels, you might look into those used as the tail wheel for a tail-dragger aircraft. You could even couple them to your rudders, for enhanced control at low speeds.
You may have to experiment with down thrust, for stability at higher speeds, perhaps by adding adjustable 'elevators' behind the two outboard fans.
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Old Feb 18, 2012, 04:31 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,651 Posts
Quote:
"All my ideas from RC Groups..."
Hey now, don't go blaming us

I was thinking of asking 'why ?', but to be honest I don't really want to know.

If you like experimenting, experiment, and find out what happens. You will learn more than just relying on others for the answers. (That's meant in the nicest way).

But it does seem to be a awful waste of three motors, to power a cardboard box.
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Old Feb 18, 2012, 05:59 AM
A man with too many toys
United States
Joined Feb 2001
17,945 Posts
With three motors I think that I will spin out of control because of the torque. 4 counter rotating motors would work.
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Old Feb 18, 2012, 04:12 PM
Wake up, feel pulse, be happy!
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United States, AK, Fairbanks
Joined Aug 2009
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I made an EDF powered car once. It was crazy fast but extremely difficult to control. Since the wheels were all free-spinning, there was no way to slow it down once it got up to speed. A reversing ESC would have solved that, but I didn't have one at the time. I was limited to straight runs with the motor running for about a third of the distance, then a long "brake run" to get it down to a speed safe enough to turn around.

Also, the impeller blades ate a ton of sand and gravel and I essentially destroyed a perfectly good EDF unit as a result. I'd imagine that your props might share its fate to some degree... Since it sounds like you're using outrunners, make sure you also keep them from ingesting small bits of matter. A grain of sand can be enough to shred a magnet if it gets caught the right way.

For the wheel configuration and such, I'd advise you to think very carefully about preventing it from tipping over. A normal car can be made with a very low center of gravity since the engine, fuel tank, and chassis are close to ther ground and all are quite heavy. With a prop-powered car the motor has to be somewhat high above the ground, which will create a surprising lever moment when you go to make a turn. You'll definitely want the battery to be placed as low as possible...

There's nothing wrong with doing some experiments, of course. Let us know what you come up with
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Old Feb 18, 2012, 10:45 PM
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Hmm... interesting for sure. There is nothing wrong with screwing around, right?

It might sort of work. If (when) it spins around or flips over, think about adding some stabilizers. Think about the feathers on an arrow. I know you don't want it to fly, but it still might need some aerodynamic stability if it goes fast enough. And I'm thinking it will go fast enough. You could make a "rudder" about as tall as a prop diameter, and an "elevator" about the same width. Why not make them both pivot too? It would be funny as to see a car fly up into the air for a while.
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Old Feb 19, 2012, 12:05 AM
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Australia, NSW, Sydney
Joined Jul 2011
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Quote:
Originally Posted by 01011010 View Post
Hmm... interesting for sure. There is nothing wrong with screwing around, right?

It might sort of work. If (when) it spins around or flips over, think about adding some stabilizers. Think about the feathers on an arrow. I know you don't want it to fly, but it still might need some aerodynamic stability if it goes fast enough. And I'm thinking it will go fast enough. You could make a "rudder" about as tall as a prop diameter, and an "elevator" about the same width. Why not make them both pivot too? It would be funny as to see a car fly up into the air for a while.
I actually think it may fly...
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Old Feb 19, 2012, 04:40 PM
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Quote:
I actually think it may fly...
Well, the only thing left then is to try it. My guess is stability/cg issues. But there's lots of tape and cardboard for that.

+1
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