Multicopter Megathread

[LittleCarrot]

37 minutes ago, ColinLTT said:

Sure am. All the time. Just built a new Yeetmule - its stinkin fast. 

 

 

Have you considered designing your frame and milling it out of CF using the cnc?

[Hackentosher]

39 minutes ago, ColinLTT said:

Sure am. All the time. Just built a new Yeetmule - its stinkin fast. 

Oh damn, 6s is a lot of fun, but was hard to manage. The back EMF when you cut throttle is pretty insane, hopefully more modern electronics handle that better than when I last tried 6s.

[ColinLTT]

15 minutes ago, Hackentosher said:

Oh damn, 6s is a lot of fun, but was hard to manage. The back EMF when you cut throttle is pretty insane, hopefully more modern electronics handle that better than when I last tried 6s.

I don't have any issues with back EMF just yet - going digital solves 99% of the issues I had with analogue, just cant get the same range for my longrange stuff so I have both DJI and Fatsharks. 

@LittleCarrotyup I've considered it, but we have a local manfuacturer (CNCMadness) that is so cost effective it doesnt make sense. Sourcing/stocking CF plate as well as sourcing compression cutters when I only want a frame or two doesnt make sense. I HAVE made my own frames in my shop though. 

[Hackentosher]

1 minute ago, ColinLTT said:

I don't have any issues with back EMF just yet - going digital solves 99% of the issues I had with analogue, just cant get the same range for my longrange stuff so I have both DJI and Fatsharks. 

The issue I had was huge voltage spikes (probably on the order of 50-100v transients) would fuck with the flight controller and or ESCs, not really sure. All I know is sometimes I would death spiral after punching out and cutting throttle. Just something to be ready for, but I have a feeling the tech these days has caught up. 6S was a pretty new thing in FPV at the time.

[LittleCarrot]

@ColinLTT What digital setup do you use? Do you use Connex or the DJI?

 

@Hackentosher I remember when I built my first quad with BrotherHobby T2 Tornadoes when they first came out. I could go through a battery in 1.5Min with RaceKraft 5051. The worst thing ever is to fly in sandy environments, like Tahoe. Apparently there is significant amount of iron in the sand, big rip 4 motors.

[ColinLTT]

7 minutes ago, LittleCarrot said:

@ColinLTT What digital setup do you use? Do you use Connex or the DJI?

 

@Hackentosher I remember when I built my first quad with BrotherHobby T2 Tornadoes when they first came out. I could go through a battery in 1.5Min with RaceKraft 5051. The worst thing ever is to fly in sandy environments, like Tahoe. Apparently there is significant amount of iron in the sand, big rip 4 motors.

I'm flying DJI on this new quad, analogue with RapidFire on everything else. Mostly TBS hardware where I can but also have some TankFPV and other TX in the stable as well. 

[LittleCarrot]

1 minute ago, ColinLTT said:

I'm flying DJI on this new quad, analogue with RapidFire on everything else. Mostly TBS hardware where I can but also have some TankFPV and other TX in the stable as well. 

What do you think of those DJI goggles that linus reviewed awhile ago?

[Hackentosher]

14 minutes ago, ColinLTT said:

yup I've considered it, but we have a local manfuacturer (CNCMadness) that is so cost effective it doesnt make sense. Sourcing/stocking CF plate as well as sourcing compression cutters when I only want a frame or two doesnt make sense. I HAVE made my own frames in my shop though. 

CNCMadness is great! incredibly affordable, and the quality is great. They cut my Mad Hatter, that poor frame has been through so much and I've only broken a couple of bits on it.

[LittleCarrot]

It seems like carbon fiber isn't the best material for the fpv frames since it really isn't that good for impact. I assume 7075 Aluminum or Titanium would be best.

[Hackentosher]

3 minutes ago, LittleCarrot said:

It seems like carbon fiber isn't the best material for the fpv frames since it really isn't that good for impact. I assume 7075 Aluminum or Titanium would be best.

I beg to differ for a couple reasons. CF's strength to weight ratio is insane. It's also incredibly rigid, but can distribute the stresses across the mesh of fibers. Metals can't exactly do that. They're also heavier and bend, which isn't great for multirotors. Carbon will crack, but it takes a lot more of a beating before it does.

[LittleCarrot]

Just now, Hackentosher said:

I beg to differ for a couple reasons. CF's strength to weight ratio is insane. It's also incredibly rigid, but can distribute the stresses across the mesh of fibers. Metals can't exactly do that. They're also heavier and bend, which isn't great. Carbon will crack, but it takes a lot more of a beating before it does.

For structural rigidity sure, but impact resistance I doubt it. Many a carbon mountain bike crack due to being smashed on rocks and such.

[ColinLTT]

5 minutes ago, LittleCarrot said:

For structural rigidity sure, but impact resistance I doubt it. Many a carbon mountain bike crack due to being smashed on rocks and such.

Sorry bud but CF is the way to go for a reason. The impact resistance is largely fixed by three things:

 

1.  Protecting the carbon with TPU bumpers
2. Using a frame design with replaceable arms
3. Don't crash

As far as the goggles - well, we never reviewed them, but we used them in the blind PC build challenge. Those are the same ones Im running, on indefinite loan from LMG. They're great functionally, besides the fact that the fit is pretty bad - I had to address that by modifying the foam with a razor. And I wish the battery lead was more secure, but I fixed all of that with 3D printed parts. 

[Hackentosher]

Just now, LittleCarrot said:

For structural rigidity sure, but impact resistance I doubt it. Many a carbon mountain bike crack due to being smashed on rocks and such.

Structrual rigidity is pretty important for flight dynamics iirc, but you're right that a high speed impact is likely to crack carbon. However, you can mitigate the damage done by reducing the mass. There's less energy absorbed the arm if the system weighs less, meaning less likelihood of exceeding the material's limits. Frame design has also gotten pretty good, engineering the frames in such a way to distribute an impact to an arm across more parts of the frame, reducing the strain at a point. Maybe at a different scale, different materials would make more sense. But for 5" aircraft, I believe in CF.

[Hackentosher]

1 minute ago, ColinLTT said:

3. Don't crash

LOL

 

I should have known, of course it's that easy.

[LittleCarrot]

26 minutes ago, Hackentosher said:

Structrual rigidity is pretty important for flight dynamics iirc, but you're right that a high speed impact is likely to crack carbon. However, you can mitigate the damage done by reducing the mass. There's less energy absorbed the arm if the system weighs less, meaning less likelihood of exceeding the material's limits. Frame design has also gotten pretty good, engineering the frames in such a way to distribute an impact to an arm across more parts of the frame, reducing the strain at a point. Maybe at a different scale, different materials would make more sense. But for 5" aircraft, I believe in CF.

 I mean carbon frames are pretty cheap theses days anyways. I am curious if there is a difference between a clone frame and the orignal in terms of structural integrity. Do you guys buy the OG frame or clones? I personal just buy clones, and rather than replace the frame id rather just buy a new one. Many times an arm costs arond $15-20, id rather spend $20 and get a new frame. I am curious if molded CF would be better than the common plate design. Something like this: https://shop.iflight-rc.com/index.php?route=product/product&product_id=1136. I assume plates would be the most economical. Also drone frames arent that aero, youd think at their speeds it would matter more.

[Hackentosher]

1 minute ago, LittleCarrot said:

 I mean carbon frames are pretty cheap theses days anyways. I am curious if there is a difference between a clone frame and the orignal in terms of structural integrity. Do you guys buy the OG frame or clones? I personal just buy clones, and rather than replace the frame id rather just buy a new one. Many times an arm costs arond $15-20, id rather spend $20 and get a new frame. I am curious if molded CF would be better than the common plate design. Something like this: https://shop.iflight-rc.com/index.php?route=product/product&product_id=1136. I assume plates would be the most economical. Also drone frames arent that aero, youd think at their speeds it would matter more.

woah that's interesting, but again what gives composites like carbon fiber their strength is the woven fibers that can distribute forces through the material from a point. I'm assuming that molded thing is similar to a "forged" carbon fiber, which from my understanding is chopped fibers mixed into the resin and then cast or injection molded. It retains the rigidity of normal carbon fiber because it uses the same resin, but it doesn't have the fibers so it'll be even more brittle. 

[LittleCarrot]

1 minute ago, Hackentosher said:

woah that's interesting, but again what gives composites like carbon fiber their strength is the woven fibers that can distribute forces through the material from a point. I'm assuming that molded thing is similar to a "forged" carbon fiber, which from my understanding is chopped fibers mixed into the resin and then cast or injection molded. It retains the rigidity of normal carbon fiber because it uses the same resin, but it doesn't have the fibers so it'll be even more brittle. 

Well not necessarily. Essentially you have a mold think of an inverse frame, that you have two halves of, you lay fibers on both halves of the mold, and then there is this airbag type thing that inflates on the inside. So you are essentially laying the fibers inside-out, and then joining the two halves together. Here is a video describing the process: https://www.youtube.com/watch?v=UWSePEV88tw (in a bike context). What do you mean foged carbon fiber? I have never herd of that? 

 

[Hackentosher]

1 minute ago, LittleCarrot said:

Well not necessarily. Essentially you have a mold think of an inverse frame, that you have two halves of, you lay fibers on both halves of the mold, and then there is this airbag type thing that inflates on the inside. So you are essentially laying the fibers inside-out, and then joining the two halves together. Here is a video describing the process: https://www.youtube.com/watch?v=UWSePEV88tw (in a bike context). What do you mean foged carbon fiber? I have never herd of that? 

 

Oh duh, I've made forms for carbon layups before lol. here's some example of forged carbon fiber, it's common in car interiors and I believe they usually use an injection molding process to form the carbon-resin mix into a mold.

[LittleCarrot]

3 minutes ago, Hackentosher said:

Oh duh, I've made forms for carbon layups before lol. here's some example of forged carbon fiber, it's common in car interiors and I believe they usually use an injection molding process to form the carbon-resin mix into a mold.

 

ah just for that carbon look. Any sort of structura piece is molded/

[sub68]

I have not been flying lately because IDK know where I put my charger

also one or the motors burned out