Keep it Secret

My goal for a frame was to sit down and come up with the frame that I would want to fly the most. I wanted to come up with something that fixed some of the issues that I currently have with frames on the market, while at the same time adding in some features that I had pictured for a long time. I actually have no experience with 3D modeling, so I reached out to Alan Hartman, co-owner of Atmospheric Adventures and got his help in taking my vision from paper to reality. The first thing that I did was create a list of “philosophies” that went into the frame. There have been different things that I’ve been thinking about over the last few months that I like from different frames, and I wanted to incorporate a lot of them together into one. So all that to say, inspirational credit for the designs of this frame go to:

Having seen the list of frame inspirations, these are the philosophies that I had developed which I poured into this frame.

    • Durable
      • 4mm single plate. 4mm Single Plate CF cuts tend to be quite expensive, but they also tend to be much stronger. The struts both on front and back will help disperse impact that would cause breaks at the stem of the arm to send shock through both arms, helping to prevent major damage. I acknowledge and accept the fact that 6″ monoplate designs carry a higher risk of “totaling” a quad because the extra fulcrum of the motor futher out on the arm will create a larger force applied to the center of the arm, but the struts will bring the strength of the arms at least back to that of a 5″ monoplate. 
    • 6” stance
      • By having a wider area to work with, and pushing the props/motors out further, we create a more stable platform. This also gives you the option to run 6” propellers, as well (which I personally like)
      • By pushing the motors further out away from the body, they have a higher relative torque on the pitch/roll of the frame. Think about it like a lever: the longer you make your lever, the easier it is to lift something. In the same way, the motor’s torque is more effiecently applied on a 6″ stance than smaller, and as a result your effective PID tuning window because easier to find as a result of motors’ forces being applied more effectively.
    • Camera positioning
      • We’re dropping the camera down inside the bottom plate, so as to bring the pilot perspective further down in line with the COT (center of thrust), which gives the pilot a better sense of control and feel relative to where the airframe is in 3d space
      • This does mean that props are in the vision of the camera, but I personally prefer having props in the view, as it tricks my brain into having a better sense of relative size. By having some small reference point, it helps me better maintain my altitude.
      • Having the camera nearly as low (in forward flight) as possible on the frame means that you are the closest thing to the ground. As a result, vertical height acquisition becomes significantly easier.
      • With “pod quads” (Artemis, Shrike 185, Falcon 185), the lens of the camera is very high above the COT. As a result, you get a feeling as though you were driving a car from on top of the car. That’s not the case with the Kratos, as it “puts you in the driver’s” seat, by pushing the camera as low as possible.
      • Camera can be lowered or raised more or less depending on pilots’ desired camera angle
    • Smashed top plate
      • The standoffs are currently set at 25mm. We are considering dropping the total height down close to 15, but are going to leave it at 25mm for now.
    • Secure VTX and antenna Mounting
      • The VTX is mounted on it’s side inside the frame, zip-tied to  CF plate that runs between the top and bottom plates. The antenna runs out the back and is zip-tied under the back support strut, keeping the antenna out of the prop line, and putting ZERO stress on the stem, SMA, or neck of the antenna. In this way, there is zero chance of damaging your VTX — only potentially the element of the antenna, but that can be built to be very very durable. Depending on what antenna you use, and how you mount it, the goal is to never break an antenna again. 
    • Underslug Battery
      • Pretty standard these days, but it seems like “hanging” the weight of the battery underneath has been good effect on the flight characteristics. 
      • In addition, having the battery underslung will help protect the camera and antenna, which will become obvious in version .2 of the frame
    • Stretch X
      • Currently a popular frame design for racing. Corners better and feels more built for straight line speed. 
      • In forward flight, StretchX turns into an X because of the angle of attack. Thus, in fast forward flight, what you find is that each motor is operating at peak efficiency during fast forward movement.

Version .1 sketches and first cuts:

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Early versions of the frame actually had a ‘nose’, but it prevented the camera from dropping further.
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Rough drawing showing the spacing of the VTX, FC/PDB stack, and camera placement relative to each other on the nose board.
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Top down view once the nose was taken out.
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Very first cuts of the Kratos. We played around with a straight back crossbar, but it didn’t suit the design as well, so we stuck with a curvy crossbar. Later versions thinned it out, moved it towards the base of the frame, and made it a bit less curvy.

 

Issues with version .1, which was the first cut of the frame.

    • Currently a bit heavy — monoplane mm with heavy crossbars and whatnot weigh in at 85g for a single plate, but with 6” capability, maybe that’s okay?
    • “Curvy” design of back strut is probably fragile, but will have to flight test it first. It supports longer antennas better like the Spironet
    • If the camera cow catcher breaks, you have to swap the entire bottom plate. We’re considering making it replaceable
    • Total Dry Weight of the frame is 103g

Images of version .1.

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First cut looks amazing.
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Back of cut 1.
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Cut 1 showing sideplate mounting.
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First fully assembled build of version .1.
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Top down view of electronics installation.
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Top down view of final build.

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