Hello there!
I am on a mission to build a non-competition robot that can fly.
I am wondering if anyone else has tried this?
I am going for a dual rotor design with servos to tilt them.
I am using as much aluminium as possible to make it light.
If anyone has attempted this can they please tell me if they failed or succeeded and why.
Regards
Stefan Andres Charsley
I have seen this and this is not like my design, my design uses transverse tilt rotors.
Much easier to build and control. Sort of like this but with a different fuselage.
Ok so my previous reply hasnt gone through.
Thats not what I am doing. I am doing an opsrey type design with transverse tilt rotors.
I think he was referring to the part that they realized lift with vex parts is near impossible.
But still possible, if you can build it, and program it, then it will fly!
they are talking about the lift (from gearing motors faster): weight (battery, metal, motors) ratio was near impossible
Yes but with the aluminium and with the small batteries, I have been able to program in to the cortex a battery monitor so if batteries start going low it will override into autonomous for landing. And if you use the high strengths geared for speed you might get enough lift. Its possible and I want to enter it into one of the online competitions.
just a recommendation: use lexan or aluminum sheet metal for the wings. great reshapeable rigid lifting material…
As to the possibilities, it is possible. i asked my neighbor, who has worked at NASA for upwards of 30 years, specializing in helicopters and lifting designs, and he said the power is going to be the biggest thing.
Because you don’t have to worry about immediate torque, as with a drive system, you can take two minutes to start up your motor, so lots of gearing might be a good idea…
As to the propeller, obviously you are going to want as much as possible. I’m not sure how lexan will hold up, but that would be my choice for crafting a blade… Also, you want to remember to counter-rotate them. (i.e. left one going clockwise, right one going counter-clockwise…) This will be really helpful when you are in helicopter mode, so you won’t have to worry about having a tail rotor.
Just a note: I would recommend a quad-rotor… If you do a double-wing design, (one behind the other) you can turn both of those, which makes control MUCH easier… (four rotors, instead of two = easier to balance)
and yeah… let’s just say i’ve thought about this for a while… 
Wasn’t trying to put you down man, just making sure you know what your getting into.
That being said, if you need any help, id love to.
I’m sure building the frame out of 1 by’s if your looking to build it out of vex aluminium.
Instead of aluminum, I would use foam. You know the rigid stuff for insulation a house with? Like this:
I’ve been looking into building an airplane for quite a while, and after looking over some airplane forums, TONS of people have used foam like this, apparently with great success. Balsa wood could be used, but it’s brittle, so it might break easier. Aluminum is, well, metal, so it is a bit on the heavy side unless you want to have some bigger motors. Which means bigger current draw, and less flight time. It’s a duribility vs. performance thing. For other parts, check out hobbypartz.com. It looks pretty legit, but I’ve never ordered from them, so I can’t say how good their service is. Maybe someone else can tell you.
Good luck!
Yeah, alot of RC planes are made out of styrofoam and glorified computer fans.
Yes I have thought about about quad-rotor but that would take a lot more programming and the PIC might not be able to handle it. I am using the PIC because we have a lack of funding since our school doesnt support vex robotics. Also I think there is a shortage of high strengths in the New Zealand stock so if we were able to get some funding it would take to long to get more. I have done some preliminary programming for the UAV which is included in the IT Framework download, its included but commented out so you will have go through and check out the comments. Right now time is a big issue because I want to finish it for the 12th of February so I can enter it into the FUTURE Foundation Design online competition.
Also a another issue is the construction/acquiring of the rotors. There doesnt seem to be any place that actually sells rotors locally. I might have to acquire some help from Massey University.
It is a mission but even if I can not finish it for the competition, I would still like to finish it and get it flying.
I would definitely buy the rotors instead of making them.
You can get them from hobby city:
http://www.hobbycity.co.nz/Soldat/productslist.aspx?CategoryID=117
8" rotors for 15nzd seems pretty reasonable.
UPDATE: I have had to go with quad rotor because the stripped down aircraft is still too heavy for transverse rotors. So now I have a dual v design to hold the rotors on, and I can have a maximum size of 600mm diameter rotors. Does anyone know how to calculate the speed in rpm in which the rotors need to be spinning to lift an aircraft thats around 1kg? Also note there will be four rotors and the high speeds have been geared with a x5 ratio. Im guessing that it will be idle/hovering at 500 rpm from each rotor which means the motor speed (programming) will be around about 80-90, and the motor is outputting 100 rpm. The maximum motor output is 160 rpm.
Regards
Stefan Andres Charsley
Another recent quadcopter thread from another site:
http://www.rcgroups.com/forums/showthread.php?t=1358183
Your 600mm (2foot!?) diameter rotors are much larger than theirs.
The thread mentions that gyro is critical for stability
The motors in the demo are running at ~9-10,000 RPM. So to go from 160 RPM, you need a 1:63 gear train. 500 RPM isn’t going to be fast enough. The demo is about 2.5 lbs, just over 1Kg
Yes I have figured this would be the case, iv minimized weight by using aluminium, currently waiting for the parts to arrive, iv been looking at some cheap motors with high rpm, seeing what I can rig to connect them to the Vex PIC. This isn’t the easiest project and im doubting the ability to finish is for the online competition, but I still want to finish it.
Foster, sure 160rpm to 10k rpm is 1:63.
There are vast differences in the reported rotor sizes, (and maybe pitches)
How do you account for that in the rpm? scale by rotor swept area maybe?
I was looking at the demo shown, he gives specs for the weight and it’s about 1kg, the target weight. I did the lookup on the motors and the specs for them, that’s how I got the 9-10K (unloaded they go about 12K). I think there was a prop spec on the demo, so that would give you a sample pitch/size.
I was watching a working demo and just translated it into what would be needed based on what was used. If you do a Google search on RC plane propeller sizes you will come up with hits on pages that say how to calculate the thrust (or lift in this case).
Most hobby propellers are not that big, thats why they go at a pretty good RPM. Larger (and I mean much larger) rotors can move slower. But I think the large size needed at 500 RPM will make it impractical.