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Nov 10, 2012, 06:26 PM
Stop me before I build again!
Discussion

"crab" style quad


I am on my 7th frame design and each time I have been adding and taking away bits. This time I have been inspired by a number of posts to create a simple and versatile frame that works as well for acrobatics as it could for FPV without any unnecessary bits. A few things in particular inspired this design, one is that props can overlap, as long as it's not too much and CW and CCW balanced it should not affect flight and someone building a FPV quad by taking a + hex and removing the front and rear arms.

To that end I created an adjustable birch 1/8 inch ply FC mounting plate and use 2x alu c-channel arms that end up at different heights. The whole thing is held together by 5 bolts and a lot of zip ties.

Just tried "crab mode" this evening and it flew very well, probably could use some tuning, but it's ready to accept the video equipment.

Passing along the pictures as an inspiration to others.
Last edited by brontide; Nov 12, 2012 at 08:09 PM. Reason: Shoot typist
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Nov 12, 2012, 07:04 PM
Stop me before I build again!
Update: video pod created, tested, and reworked. Still got some vibes, but can't rule out my mangy props until a fresh shipment comes in. Still need to give the video plate a coat of paint. Switching between angles is about a 20 minute ordeal, will probably get it down to 15 with some practice.
Nov 12, 2012, 07:37 PM
Registered User
Matt Chester's Avatar
Can you get some video of it from LOS and Onboard to share? I'd like to see that for sure. I like your ideas here and the simplicity of construction.
Nov 12, 2012, 07:43 PM
Registered User
When you use the wire ties to mount the props to the motor bells is that to allow the ties to breakaway on ground impact and save the props from damage?
If so does it work?
Wonder if maybe they are causing your vibrations?
Nov 12, 2012, 08:03 PM
Stop me before I build again!
Once it's tuned up some on board video should not be a problem, from the ground will be a little more difficult since ill have to find a willing helper sucker.

The zip ties do work well presume they are put on correctly ( tied on the trailing edge ) and they will sometimes break on crash rather than the props. I have not noticed any issue with balance because of the ties. I also have to be careful that they are good quality, had a few crashes before I recognized that one batch of ties from HD was crap and stopped using them for structural items,

Here is the maiden, untuned, uncut video from the pod.

Practice (2 min 33 sec)


Tomorrow looks like a washout, but maybe later in the week I can get some real flights in.
Nov 13, 2012, 08:24 AM
Stop me before I build again!
Picture showing blade separation from the side. When its in traditional X configuration there is no overlap in the blades. I will confirm when the weather breaks that I can do full yaw sticks without blade strike.
Nov 13, 2012, 11:03 AM
Stop me before I build again!
Sorry for the short video, but I had been through 4, or so, iterations before hitting on this alteration. Even with my crappy props I get vibe free video downloads! Basically going soft was the wrong way, i tightened up everything on the pod and then loosened the pod from the FC plate in order to isolate the video and battery. Photos to follow.

Mount tweaking (1 min 5 sec)
Nov 13, 2012, 11:33 AM
Stop me before I build again!
Updated shots of the mount. Can only post 1 pic per post on the iPad.
Nov 13, 2012, 11:34 AM
Stop me before I build again!
Even with props that look like this!!
Nov 13, 2012, 02:22 PM
Stop me before I build again!
Longer video, still need to play with my motor mixing. Turning down the pitch made it less twitchy, but the wind nearly took me into some lines. Need some more height dampening as well.

Tooling around (11 min 15 sec)
Nov 15, 2012, 02:35 PM
Stop me before I build again!
Had so much fun with it in traditional X mode I switched back for a few days. Here is a short video LOS in my very small front yard.

Crab Los (1 min 32 sec)


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