Killbot Mk I

By ACROBORG on Jan 29, 2020

34  1,168  21

Still very much a work in progress. But it really seemed like it needed to happen. Put 4" toothpick-class hardware on a sturdy, minimalist freestyle body. Is this the future of FPV freestyle? How will you make every 249g count? Initially testing with a 3000mah 2s 18650 pack, what's lost in raw speed is regained in ENDURANCE. There's a reason the Mavic Mini uses the same configuration. Testing on 3" and now this 4" quad, flight times of 15-20 minutes are normal. ~235g as pictured with 18650 pack.

Photos

Discussion

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Samiel2d   8 days ago  
2

how are those 1404 motors working for ya? looks good with the matching braided motor wire cover.

ACROBORG   5 days ago 

Thanks! I'd say these 1404 7000kv are likely the perfect motor spc for this quad, or at least getting really close. I'm finally getting nice smooth prop control through most flight situations. I haven't flown it in intense wind yet though. Peak thrust is limited more by battery then the motor, so I can't imagine larger motors would be of much benefit. I still have some question as to the best KV... if 5000-6000kv would be sufficent, or if there would be any benefit from something 8000-9000kv.

Samiel2d   5 days ago 

i know that the 7500kv motors ive run didn't like anything more than 2s voltage on a 2.5" prop. i would assume that with the voltages you're using that the higher kv would be better performance than a 5000kv motor. im trying to decide if im going to get a whoop next (spring is coming and the rain here will be constant for the next month or so. or to build a mutant 4 with a set of 1204 5000kv motors

dejavu   9 days ago  
1

Can you please talk more about the batt, like diagram? Can you share the Battery cover stl please?

ACROBORG   5 days ago 

Yeah! I'm working up a guide to how to build them, along with the STL files. I'll update here when they're available, as well as post in the brushless micros facebook group.

Samiel2d   12 days ago  

the 1108s don't have a problem swinging the 4" prop? what is the voltage of that 2s 18650 pack?

ACROBORG   11 days ago 

Funny you ask about the 1108 motors... They're actually doing suprisingly well, performance is totally adequate, temps are fine, and overall flying nicely. But I'm having trouble getting that last bit of smoothness I need in the footage. So I have some xing 1404 7000kv showing up tomorrow that are getting swapped on, I'll see how they work out. The 18650 pack is 8.4v fully charged, and I aim to have it back on the ground around 5.8v.

Samiel2d   10 days ago 

thanks for the insight. i saw your build the other day and i instantly thought about getting a racer x mutant 4 with these motors. probably will keep with lipo batteries as im not as concerned about endurance. just good to know those motors can handle the 4"

IceC0ld   11 days ago  
1

Is the frame available to purchase?

IceC0ld   11 days ago 

It would be a great platform for a cinewhooop build, with a naked gopro on it.

ACROBORG   11 days ago 

I haven't decided if I'm just open-sourcing the plans, or free plans and also offering frames for sale, or what exactly. Either way, I'm just flying (and testing) it as much as life/weather allows. And I've already started playing around with a pod design for a nano-cam + naked H6 :)

IceC0ld   11 days ago 

That would be great. I also want to develop it, design a tpu prop guard for it. Much like the Cinerat frames tpu prop guard.

Want to move into Li-Ion cause Lipo batterys here cost so much.

Looking forward to your cinewhoop build in that frame

zsoltm   13 days ago  
1

Impressive! I was thinking about the same, 2S LiIon on 3-4" or maybe 3S on 5" with DJI FPV, so it's very nice to see it's working in practice. Also the cam mount design looks very solid, well done.

Jodie Froster   19 days ago  
1

This is SO good.
Love the cam mount, love the layout, love the weight!
Hit us with some footy!

ACROBORG   17 days ago 

It's coming along! The weather hasn't been so cooperative, but today's flight will get posted.

IVRZ   18 days ago  

15-20min?? thats pretty crazy! Does the battery just have lower discharge rate so theres less punch? I think this type of battery is good for cinebees and smooth flights. Nice Job!

ACROBORG   17 days ago 
1

Lithium Ion cells come in a wide variety of chemestries, so I'm only really talking about the ones best suited to our needs (most the rest just suck). LiIon (Lithium Ion) packs more energy into less space then Lithium Polimer (LiPo), but also has higher internal resistance. Basically it's a lower C rating. So to make it work, the quad just has to be designed around sucking fewer amps, and keeping up prop RPM at low voltages. Essentially, the same stuff that lets modern Toothpick-type racers have stupid-fast acceleration for a couple minutes, means that even at half the thrust-to-weight this thing still rips around plenty quick for a long time shooting 4k footage :-)

kfncolo   18 days ago  

Does that FC/Esc work in the 6-7 volt range, which would allow you to use more of the li-ion battery capacity?

ACROBORG   17 days ago 

Yup. I'm using a tiny LC filter supplying vbat to the camera. It will run 5-20v. The VTX and RX use 5v, and it all appears pretty tollerent of low voltage. I haven't actually found which component glitches first, I've had it in the air below 5.4v specificly testing to see what happens. I'm sure something was struggling, but nothing failed. With this quad, and other's I've flown with 18650, I aim to be back on the ground by 2.9v. At that voltage, everything seems to hum along fine.

miromir237   18 days ago  
1

Yep, this is probably the future. Nice design. It would be nice to get it working with DJI FPV.

ACROBORG   18 days ago 
1

Eventually I'm sure this size of quad will feature digital FPV. But right now, the Air Unit would dwarf this quad. It would have to be so much larger to fit it, it wouldn't be the same quad. However the Caddx Vista should fit ok directly over a Zeus AIO. When the frame goes open-source, if I don't design a camera pod for the Vista I hope/expet someone else will :)

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