Misc From the Ground Up

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claytonbakerjr

Member
Ok...
I have read many forums, many articles, many things to the point to where my brain is bleeding :/
Since I work at a Composites factory I tend to run into opportunities where I can grab
nice looking carbon fiber sheets.
They range in sizes and thickness but the other day I ran across a very nice piece that was 13x18 inches
and around .100 thou thick.
We make composites for air craft engines so I know this stuff can take a licking and keep on ticking.
Then last week I ran into a site that has several Quad Copter design plans that come in DXF cad files...

(for those interested: http://untestedprototype.com/category/plans/)

Now I am very interested in messing around in the shop and I am going to make a frame out of some
of the carbon fiber I have acquired.
In short it will be a major DYI project since I will be doing most of the work by hand.
If I can talk my CNC guy into cutting the frame for me then great but at this point I will assume my own destiny.

I was a machinist for over 20 years prior to going 180 degrees and jumping into the IT field 16 years ago so I'm pretty
much covered on both aspects.

The one thing I would like to gain more knowledge on is how to configure the end result.
When it all is done and said, weight is the main key to configuring things that fly.
To my understanding once you have weight then you need to configure motors and props (thrust)
Also tossing in the battery/energy scenario...

Now my plans are to work on a 300mm frame style not so much for racing and doing flips
but more so for camera and "just to have a good time flying FPV" experience.
If I get crazy it will be with the 250 :)
I like building things, I always have.
Heck if I get some new electronic device I typically tear it apart just to see how it was built.
I tear my motorcycle apart all of the time...hummm...maybe thats why its having problems....DOH!!!! :)


So can some of you point me to some good resources so that I can do some more brain bleeding? :)
Or maybe toss out some good ideas.
 
Tony

Tony

Staff member
Maybe I missed it, but what is it that you are needing help with? and if you build a frame, you have to send me one. :biggrin1:
 
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claytonbakerjr

Member
Oh I am sorry maybe I wasn't clear...see my mind has almost bleed to death....
Help on configuring Thrust, motor size and battery size for weight.
For example it the end result weighed 500 grams what size motors, Props, ESC's and battery would be idea
for the longest possibly flight times.
Ideally I am looking at a 6 to 7 inch prop.
For the most part this build will be a learning experience for me.
Its easy to go out and buy ready made items but I like to see my own work when the day is over.
Now this is a project that will linger for months so I am in the early stages of planning and design :)
 
Tony

Tony

Staff member
In theory, if you have a 500g AUW quad, you will want motors that can handle 1.5x the weight. Meaning, you will want something that will do 125/lb/thrust*1.5. That would be 187.5/lb/thrust per motor. Now, this is going to depend on what motor you are running, what prop, wattage, kv, battery and so on. IMO, take a look at what the 300 size quads are running and start there. If that doesn't work, move up to the next size motor and try that.

I have been asked this question a lot and the real answer is just trial and error. There is no real regulation on how manufacturers come up with wattage rates so they are going to be different for each one.
 
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claytonbakerjr

Member
Yea thats kind of what I am seeing out there.
Ok so Motors and Props I can understand...what about ESC's
I see 12, 15, 20, 30 ect.
What governs the size of the ESC?
Most motors will run in a 3s or 4s config but why
so many different amps for ESC's?
More power to the motors?
 
Tony

Tony

Staff member
No, the motor will only pull as much power as it needs. The esc and battery do NOT push power. So I'm you have a motor that is pulling 20a and you put a 12a esc on it, the motor is still going to pull 20a and it's going to release the magic smoke from the esc. Your esc should always be bigger than the motor requires and your battery should have a larger C than the esc is rated for. Hope this makes sense.
 
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claytonbakerjr

Member
Thanks Tony
So as an example.
If I have a motor that states Max Continuous 17 Amps
A 20 amp ESC would work but I feeling a 25 would be better
at least for the heat side of things?
 
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Tony

Tony

Staff member
If you had a 17a motor, then I would go with the 20a just to save weight. Most of the time, you are not going to be pulling full amps out of that thing. Only in short bursts, and most ESC's can handle a burst of amps over what they are rated for about 10 seconds.
 
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claytonbakerjr

Member
Well in between the 250 build and messing with my Eye One Xtreme I had mentioned
gaining access to some carbon fiber panels.
This is the frame I am slowly making progress on. I have it rough cut currently but did not take pics yet.
Not sure why the white stripes are on this but once I get everything cut down and holes drilled
and weight reduction holes most of it will not even be noticeable.
My company makes some pretty strong stuff and this is 14 plys thick.
it is a bit heavy now but once I am done I expect to reduce the weight by at least half
of course not sacrificing strength.
I am debating on which direction to go with Arms.
I can purchase longer 250mm arms like those for our little 250's or was actually
thinking about doing round or square CF tubing.
I was looking on ThingiVerse and found several frame/tube mount designs as well as
motor mount designs.
Not confident on using 3D printed stuff for the motors but I feel the frame mounts
will be much more stable.
I can always get motor mounts online designed for the task.
Carbon 300mm.jpg

A few months ago I had also acquired another piece of carbon fiber and have this almost ready to go
for my Eye One Xtreme.
This one is about 8 to 10 plys thick but the EOX is a light design to begin with.
I measured it off to be right at 260mm tip to tip on the frame and once I get
things mounted the motors C/L will be around 230mm to 240mm.
EyeOne Frame.jpg

Carbon 300mm.jpg

EyeOne Frame.jpg
 
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claytonbakerjr

Member
Yea I run into all kinds of scrap'ish stuff.
The only reason they scrap it is one of the ply's might not be perfectly aligned
which does absolutely nothing to the strength.
Our stuff goes into Aircraft engines so they have to be perfect or they get tossed.
 
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claytonbakerjr

Member
Lol...if I had the extra cf I would. I mean it's not perfect like a cnc machine but from the view you see its very hard to tell otherwise. Once it is air worthy and pegging about 30 mph past your head then neither will anyone else lol.
I'm very pleased on how it turned out especially only using a band saw and a dremel tool. Can't wait until the holes get cut for weight reduction then I can start focusing on motors and esc's.
I'm going to put some 6 inch arms on it.
MRM sales some 12 bucks a set.
 
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claytonbakerjr

Member
Was going to but ran out of material. Had enough for 3 but not for 4. Besides the toughest part of this is going to be to align the arms at the right angles and getting mounting holes right. If I get pre made arms with holes it will make lining them up much easier as well as drilling the holes into the frame .
If I were still a machinist I would have done it on a mill and wouldn't have had to think this hard lol.
There are days I wish I didn't go into computers lol.
But I like working with my hands makes me feel like I accomplished something.
 
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