63 replies to this topic

[MikeH]

I crashed my FPV quad some time ago and rather than rebuild I decided to just make anew one. I built a new CNC a few months ago and I'll take any excuse to put some miles on it. I'm just waiting on some 4mm rod to replace my motor shafts. I want to thread them and mount the prop directly to the shaft rather than use prop adapters. This quad is of course powered by OPCC.

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Edited by MikeH, 12 July 2012 - 07:41 AM.

[Terrier]

Mighty fine work...

Couple o' questions:

- What's the arm size?

- What's it weigh?

- Which ESCs are those? HK 30's?

- What motors/Props/Battery are you going to sling on there?


Okay... that was a "few", not a couple. Nice CNC work!

[snafu]

don't suppose you would mind sharing the DXF file wouldn't mind cutting one of those out on my cnc ..
Much appeciated if possible if you choose to share it email it to me at snafu@snafu.net.au

Thanks mate

Trev

[Golden]

That.. is a super sweet looking cut! Hard for me to tell from the images, but is the frame symetrical for motor placement and CG? That is a really nice looking frame, and I love the detail that went into the battery mount and camera mounts! Woudnt happen to have a couple spare of those camera protector peices lying around by chance?

[johnnycat500]

Beautiful work. Cant wait to see some flight video. I am sold on g10 frame and wood booms.

[MikeH]

Mighty fine work...

Couple o' questions:

- What's the arm size?

- What's it weigh?

- Which ESCs are those? HK 30's?

- What motors/Props/Battery are you going to sling on there?


Okay... that was a "few", not a couple. Nice CNC work!

It is a symmetric 550 size quad.

The FC is dead center between all the motors.

I've got a lot of DT750s so I'll be using those with 10x4.5 props. I'm just waiting on some 4mm rod so I can replace the shafts, thread it and mount the props directly. I cut the original shafts to short to mount the props I'll use.

Battery will be a 2200mah 3s but I've got some 3000 and 4400 that is why I did the battery plate on a boom that way I can just move it up for larger batteries and still keep my CofG in the center. The ESCs are Dynum Detrum (plush clones with atmega) 18A, I flashed them with simonk FW which is a first for me.

All together she'll weigh just over 1200 grams without a battery, about 1400 with a 2200mah 3s.

Edited by MikeH, 12 July 2012 - 04:49 PM.

[MikeH]

don't suppose you would mind sharing the DXF file wouldn't mind cutting one of those out on my cnc ..
Much appeciated if possible if you choose to share it email it to me at snafu@snafu.net.au

Thanks mate

Trev

The DXFs are on their way to you. I cut it in two 12x12" sheets, I have a lot of them left over and didn't want to use a full 24x24".

[MikeH]

That.. is a super sweet looking cut! Hard for me to tell from the images, but is the frame symetrical for motor placement and CG? That is a really nice looking frame, and I love the detail that went into the battery mount and camera mounts! Woudnt happen to have a couple spare of those camera protector peices lying around by chance?

Yep it is a symmetrical 550. Send me a PM, I don't have any spares but I can always make them.

[MikeH]

Beautiful work. Cant wait to see some flight video. I am sold on g10 frame and wood booms.

Thanks, I really do like the combination of wood and G10 still very stiff, cheap to repair, lightweight and it doesn't transmit vibrations like other materials.

[Terrier]

Mike,

On the booms, what is the dimensions of the wood? Are those 10mm, 12mm, 1/2", 3/4? I can't quite tell, but they look kinda beefy.


Jack

[eFinger]

REALLY like this design Mike. Some great ideas here and I can't wait for some flight footage. A few Questions/points:

Whats it called? Come on, gotta give it some cool spider name

I'm tipping 10" blades will be seen by the GoPro but probably not 8" blades?

Curious about the distance between the battery and those back blades. I guess we can wait until you fit it out before we know that. Also does the battery go longways or across that back plate?

Like I say, great design. I'm getting into wooden arms recently. Well done!

[MikeH]

Mike,

On the booms, what is the dimensions of the wood? Are those 10mm, 12mm, 1/2", 3/4? I can't quite tell, but they look kinda beefy.


Jack

The booms are 1/2"(12.7mm) poplar. 1.29$ a yard at your local hardware store. Just make sure you look down the length to get the straight ones.

[MikeH]

REALLY like this design Mike. Some great ideas here and I can't wait for some flight footage. A few Questions/points:

Whats it called? Come on, gotta give it some cool spider name

I'm tipping 10" blades will be seen by the GoPro but probably not 8" blades?

Curious about the distance between the battery and those back blades. I guess we can wait until you fit it out before we know that. Also does the battery go longways or across that back plate?

Like I say, great design. I'm getting into wooden arms recently. Well done!

First of all I'm not good at naming things but I'll think about it.

Yes with 10" props you'll likely be able to see the props in the top of the frame and since the GoPro has a 170 degree viewing angle at 720p it is difficult to get them out of view without oversized frame plates. I'll have to check about 8s it might be pretty close. It is always a trade off.

Yes the battery goes long ways on the battery plate (perpendicular to the boom). With 10" props and a 2200mah battery the props don't blow on top of the battery but it is close.

And Yes I love wooden arms. It is an under rated material for multirotors.

[Petronio]

I love it Mike! I would like to have a copy of the dxf files as well if possible, I have been drawing my second homemade design as well but haven't finished yet. Your frame would be a great start point to adapt it to my uses if you do not mind of course! If so here's my email: petronioaznar@hotmail.com

Thanks and let us know how your maiden went

[MikeH]

I love it Mike! I would like to have a copy of the dxf files as well if possible, I have been drawing my second homemade design as well but haven't finished yet. Your frame would be a great start point to adapt it to my uses if you do not mind of course! If so here's my email: petronioaznar@hotmail.com

Thanks and let us know how your maiden went

No problem the DXFs are on their way, alter to your hearts content. As soon as I get my shafts in I'll get her up in the air and report back.

[MikeH]

Some of you builders and designers may find this info interesting:

During the initial development of this frame I did a bit of FEA (finite element analysis). In this set I've subjected the frame to a 10g acceleration straight up. This would be the equivalent of each motor producing 2000 grams of thrust from a standstill for instance in a super fast takeoff. I doubt anyone would actually put motors capable of 2000grams of thrust on a 550 sized frame like this but I just wanted to simulate an extreme flight induced load.

The frame plates are 1/16" G10 and the arms are 1/2" square poplar. The front is loaded with a gopro and the rear has a 180 gram battery.

Keep in mind the color scale when looking at these photos. Red is not necessarily a bad thing, it is simply the point of highest stress or displacement. For instance a red spot in one of the stress plots indicates stress of 14 MPa where the yield strength of the material is about 300Mpa so it is actually well within the mechanical limits of the material.

In the displacement photos the top left corner shows a deformation scale. This allows you to exaggerate the deformation in order to better see the deflection of the frame.

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[MikeH]

I also did a frequency analysis on the frame to find resonant frequencies. The resonant frequencies of the frame are 6.7293, 10.703, 12.182, 16.878, 44.346 Hz . Since the motors spin in the thousands of RPMs I don't foresee any problems with runaway vibrations. I think that since all of the motors would be spinning at slightly different RPMs anyways and that they would likely be out of phase with each other that resonance would not be a problem because of all the interference.

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Edited by MikeH, 15 August 2012 - 12:54 AM.

[MikeH]

And finally, in the RCG forum someone raised the concern of torque on the battery boom.

The test shows the torque on the battery and the boom if the multirotor were doing barrel roles at 1080 degrees/s/s. Meaning after 1 second it would be doing 3 rotations/second, after 2 seconds it would be doing 6 rotations/second and so on.

Again keep in mind the scale of the deformation. What is shown is almost 1000x greater deflection than the actual. One side of the battery would only rise by 0.05mm. Plus the max stress is less than 0.3% of the yield strength

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[K Wells]

Nice Work, Mike. Well thought out, qualitative analytics and I like your Desktop CNC Router

[Petronio]

Agree with that, I have seen little people carrying out such in depth analysis in relation to material strength and its limits. They may do but most are more worried about releasing it as soon as possible and making profit (again, one of the opposites of what OP is about so your project certainly fits well within this community ). Thanks for the files Mike, will check it out at home but judging from your pics and modelled screenshots it looks simply great.