Suggestions on different designs for school project

[Borg]

Hey guys,

First off, I'm new here so forgive me as I get used to how this forum works.

I'm leading a group of about 6 college students where we're doing a design competition for the American Society of Mechanical Engineers.

If you'd like to read the problem statement, you can find it here: https://www.asme.org/getmedia/c9569a01-86cc-4dc7-888b-02311ed2bed4/Lighter-than-Air-UAV-FY14.aspx

I'll give a quick overview of the basics: Must fit within a 28" diameter cylinder in any orientation. Must carry as much weight as possible (included the copter itself) to maximize points. The copter will be navigating a small course (5m x 8m) and doing simple tasks, the max time for the trial is 5 minutes (but we can go for less).

For budgeting purposes we're trying to keep it below $1,000.

Now, here's some ideas we've come up with:

#1: Coaxial octocopter: Have 2 sets of 4 rotors with diameter 10" (should fit within 28" cylinder without any issue).
#2: Quadcopter/helicopter mix: Have the 4 10" rotors control the direction, then have two large counter rotating rotors directly above the center (I was thinking ~20" each).

Anyone have suggestions based on this? I think that #2 would be stronger but I'm concerned about cost and control...would we need a separate controller for the two larger rotors?

I appreciate any help! Thanks,
Borg.

 

[mbsteed]

I haven't read all the details but you have a limited budget. If there is any place to skimp on price it is the frame. I made an octocopter out of cedar straps from HomeDepot with plywood base plates and it is lighter than my carbon fibre frame I paid $1000 for. Although the carbon frame is stronger the wood frame octocopter lifts a camera gimbal and a Canon T2i. Put your money into good motors, ESCs and a flight controller. I think your idea of coaxial is a good one for a smaller diameter constraint. However, most flight controllers can do coaxial but in an X8 arrangement (option 1); those are not setup for your suggested arrangement in option 2.

Herre is a source of cheap frames and parts.

http://www.foxtechfpv.com