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Patrick

Thu Nov 22 2012, 05:52AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Chris Cristini wrote ...

Thanks Steve for answering my Thrust question. I guess it is back to the drawing board.

this is a matter of mass fraction for vehicles.

Your purpose is FPV, right?
how much will your heaviest transmitter and camera wheigh?

Traditional Astro and Aero space design starts with the payload, and then uses math to back out into the final solution.
(like the American Saturn 5, and Russian N-1 rockets)

Chris Cristini

Thu Nov 22 2012, 06:13AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Well I could fiddle around with a Variable System like this

Patrick You have a great Point I just want very long flight time and a good size frame for other capabilities and experiments with things beyond the Normal FPV Quad-copter I don't want to use it for the 50 Caliber turret but anything I can come up with Maybe a RPG launcher?

Oh I could always make one big enough to strap my self to it like this one

Only I could not trust electric Unless I am piloting a Glider so if something goes wrong I could just glide.

Pinky's Brain

Thu Nov 22 2012, 02:45PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Another problem with IC is the noise ...

Chris Cristini

Thu Nov 22 2012, 05:14PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Well for a prototype I could build a single motor Quadrotor with Trex 450 Parts it would cost pennies compared to what I want to do in order to scale it up I could use light weight Differential parts from big rc cars or what not the Trex tail Assembly is belt driven but they also have Bevel Gear assemblies with torque tubes AKA Drive shafts like this

But replace the little Blades with bigger ones. And yes I.C Is very loud but there is ways to make them much less noisy.

Patrick

Fri Nov 23 2012, 03:51AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

the real soluotin is to have one piston engine driving a generator, which has an onboard SMPS which divides the power to the 4 electric rotors...

electric motors are more reliable then piston or turbines (for a given high power desnity), that why there used on diesel-electric-trains....

the reason why electric cars suck balls isnt the motor, its the batteries, dont confuse the two.

PS, you need rocket launchers to keep the squirrels in check...

Chris Cristini

Fri Nov 23 2012, 04:07AM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Sounds Interesting Patrick I will look it to micro generators and maybe a cheap 1cc ICE from ebay and make a small Prototype This thread is kooking up some good Ideas from everyone and I am learning tons Thanks Guys.
Haha Use CGI Effects to make a quad rotor with twin rocket launchers and blow up a squirrel.

Pinky's Brain

Fri Nov 23 2012, 10:44AM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

wrote ...

the real soluotin is to have one piston engine driving a generator, which has an onboard SMPS which divides the power to the 4 electric rotors...

I'm not so sure ... the RC helicopter tailboom solution with a single central motor is pretty elegant as well. If you want to have electrical power for backup you could use a clutch on the IC engine and have a brushless generator/motor on the drive axle. I doubt the mechanical losses will be as severe as going through a generator, two DC/DC converters and a motor. I thought you were all about having the minimum number of motors? :)

Hanzie

Fri Nov 23 2012, 11:41AM

Registered Member #6534 Joined: Sat Sept 08 2012, 12:22PM
Location: The Netherlands
Posts: 32

Well, the reason electric motors are mainly used on quads and octos etc. is because they react immediately on a throttle input. Piston engines generally take longer to react, which can cause problems at this size.
Also, LiPo batteries aren't really that expensive if you know where to get them. I usually get my cheaper stuff like motors, batteries and servos from hobbyking. (I don't trust their radios though, I'm just sticking with my DX-7) So I think it's easier to just carry some more batteries than to bring an entire generator including fuel.
Would be interesting to see though! xD

Pinky's Brain

Fri Nov 23 2012, 11:55AM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

They react fast, but not as fast as rotor pitch control.

Steve Conner

Fri Nov 23 2012, 01:21PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Years ago I experimented with a weed-whacker engine running a car alternator, for a hybrid Robot Wars bot. The efficiency and power output was pretty dismal, even with a big helping of nitro added to the fuel.

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