Designing my Own 450 Folding Frame

[NorcoT]

Hi all, by day I am a Mechanical Engineer having had much experience in the past designing aircraft components. Having looked for a 450 folding frame online and only finding £90+ solutions I have decided i';m going to design my own.

My requirements:
> 450 Size
> Quadcopter
> Foldable for easy transport (hiking!)
> 10" / 11" Prop Capability
> Space for GoPro (with no props in vision)
> Target frame only weight ~300g
> Space for 4000mAH 3S battery

Nice to haves:
> Landing Gear
> Gimbal attachment point

Currently I have a folding mechanism in mind like the LS-450 Butterfly Alien frame: http://www.goodluckbuy.com/ls-480-450mm-butterfly-alien-carbon-fiber-quadcopter-frame-rack-for-fpv.html

I will have the Carbon plates CNC';d to my design by a company and the other components I plan to purchase off the shelf, apart from the arms which I will make from Aluminium Square Section or Carbon Tubes.

I am currently performing a planform study. i';ve sketched up in plan view a 450 motor to motor distance with 10" props and currently manipulating the positioning of the frame relative to the motors to see how the arms line up. It';s rather challenging getting the frame plate as far forward as possible whilst not to make it too long so that a battery can be placed aft to balance the quad.

This is where I need some input:

Planform - I have run a F450 and a Tarot 650 frame in the past, both have the motors in a ';square'; layout so the distance between the front two motors is equal to the distance between the front and back. Now I know this works flawlessly with my current flight control / motor setup etc, but i';ve noticed some frames dont follow this - so the distance between left and right motors is larger than the distance between front and back. Does anyone have any input or experience as to how this affects a Naza FC? Any info is useful thanks.

Parts - I plan to purchase off the shelf motor mounts, i';ve found some spares out there but not always cheap. Can anyone point me in the right direction for a good place to purchase spare motor mounts for Square arms and for Tubes?

Any other input is welcome too! I plan to share the design when im going / once im done, and if its a hit I would be happy to build some for people. But thats a long way off yet!

[flybywire]

Nice idea NorcoT.  I fly a xugong10 foldable quad, and it is superb, and everything goes in a small backpack.  It';s great to design your own tho.  Reason I mention this, if you take a look at said xugong, the controller itself does not sit centrally in the frame, but rather toward the front, but I have found that as long as it (the FC that is) knows whereabouts it is relative to the CofG, it';s fine.  This can be adjusted on mine by sliding the lipo forward/aft, although in practice, although I use two sizes of lipo, I have never needed to do this.
If you are a designer, probably best to get a pile of wood and screw your prototype together on the bench, then test fly it first (test bed).  If she flies well in wood, then G10/carbon should be perfick!


Good luck with the design, show us some pics when you get the chance!

Andy

[NorcoT]

.. but I have found that as long as it (the FC that is) knows whereabouts it is relative to the CofG, it';s fine.  This can be adjusted on mine by sliding the lipo forward/aft, although in practice, although I use two sizes of lipo, I have never needed to do this.

If you are a designer, probably best to get a pile of wood and screw your prototype together on the bench, then test fly it first (test bed).  If she flies well in wood, then G10/carbon should be perfick!

Thanks Andy! I did consider the Xugong 10, seems quite difficult to get hold of one, most of the frames i';ve come across are either very expensive or come as a complete quad. Nonetheless they seem highly regarded.

Building a test bed is a great idea thanks, will be sure to give this a go prior to getting the Carbon cut.

Its not much yet but heres a screenshot of a couple of lunchtimes worth of playing about with geometry. still needs further tweaking to find a good layout. The ';v'; at the front of the model is a marking of 170deg which is the FOV angle for the GoPro, considering the camera is below the props it shouldn';t catch much (if any) view of the props.

And the plate needs to be shrunk down a little!

[attachimg=1]

[flybywire]

Looks cool!  Foldable quads are the best!

I do have access to a laser cutter at my ';place of grind'; so if you do need your prototype cutting accurately from wood or perspex, just PM me.   

[flybywire]

I suppose the make or break of a good foldable (flight characteristics not withstanding) is how quick and easy it is to unfold!  I guess the reason I like the Xugong so much, is the fact that there are no fiddly nuts and bolts to assemble (or leave behind) at the field (usually with cold numb fingers ;-().  What kind of mechanism do you plan on using here NorcoT, or are you applying for patent first?!   

There must be a simple but reliable locking device to be made, but most if not all the homebrewed ones I';ve seen (and a few commercial) use nuts and bolts which you assemble prior to flight.

[richardg6paj]

I thought of trying a pantograph type of mechanism. But was only off the top of my skull. Not thought that much about it to be honest.
It';s really all down to weight I suppose. 

Richard

[flybywire]

Immersion';s design is nice and simply, but does rely on well manufactured parts.  I guess if you had a 3D printer etc, it should be possible to get something spring loaded with well locking parts designed?

[flybywire]

The arms are easy to pivot, if you have a carbon or aluminium spindle, but it';s getting the mechanism to lock simply that stumped me. 

Agh, what the heck, might have another go at it!

[NorcoT]

Looks cool!  Foldable quads are the best!

I do have access to a laser cutter at my ';place of grind'; so if you do need your prototype cutting accurately from wood or perspex, just PM me.   

Thanks for the offer! I';ll be in touch when I get somewhere further with the project, obviously willing to pay for material and postage etc.

What kind of mechanism do you plan on using here NorcoT, or are you applying for patent first?!   

Haha, no patent planned, tbh I havent thought through the locking mechanism in detail yet, will depend on my selection of the arms. I can go with carbon tubes and use the same plastic clip that the Tarot';s use (just buy off the shelf). I will go through a concept generation phase for that mechanism once I get the plans set out a little more. Watch this space!

[flybywire]

Certainly, we have plenty of wood here!  Ah, plastic clips?  I haven';t seen them. 

[NorcoT]

Certainly, we have plenty of wood here!  Ah, plastic clips?  I haven';t seen them.

These things:
https://www.hobbyking.com/hobbyking/store/__61360__Tarot_FY650_FY680_16mm_Folding_Arm_Clamp_Black_.html

[flybywire]

Good old HK!  No sense reinventing the wheel eh?

[NorcoT]

The latest, been updating the sizes and getting the frame about reasonable.. Work In Progress.

[attachimg=2]

[davejavu123]

Thanks Andy! I did consider the Xugong 10, seems quite difficult to get hold of one, most of the frames i';ve come across are either very expensive or come as a complete quad. Nonetheless they seem highly regarded.

Building a test bed is a great idea thanks, will be sure to give this a go prior to getting the Carbon cut.

Its not much yet but heres a screenshot of a couple of lunchtimes worth of playing about with geometry. still needs further tweaking to find a good layout. The ';v'; at the front of the model is a marking of 170deg which is the FOV angle for the GoPro, considering the camera is below the props it shouldn';t catch much (if any) view of the props.

And the plate needs to be shrunk down a little!

[attachimg=1]

solidworks?

[al-xg]

I';ve been building something pretty similar but a bit larger with 15/16" props.
Snazzy Solidworks shot:

I did start off designing some clips to lock the arms into position but ended up reverting to just having a good friction fit between the plates.
The main issue was I ran out of room on the carbon plates I have (300x100x1.6mm), not that I';d want to make the frame much larger.

I use glue-lined heatshrink around the carbon booms to make sure they don';t slip even with more acrobatic flying(whether intentional or not  ).

Where are you planning to put the ESCs?

[NorcoT]

Yup solidworks, I use it for work so in my spare time I do some modeling for the quad. Nice mode and render!

I';ve still to model the esc and find somewhere to put them, in my current quads I just wire tie to the arms, not pretty but it works. Maybe i';ll hide them under the plate..

How did you do you';re motor mounts? Did you make or buy them? I';m thinking carbon tubes for arms if I can find or make decent mounts and devise a clip system.

I';m a long way off yet though, still trying to get the layout right before sticking in all the detail.

[al-xg]

The motor mounts I currently have are FDM 3D printed but I';m planning to get a few sets in SLS once I';m happy with the design.
My ESCs are currently between the frame plates and the wires to the motors run through the booms (~10mm ID), I';ll do some tests flights and see if cooling needs to be improved.
I want to keep the booms free from external wires and feel they';re just too long to have the ESCs by the motors as that would mean long battery wires and the need for external capacitors.

Have you considered using folding props? I was initially making my own but you can now get some ready made ones that are pretty decent and cheap.

[NorcoT]

We have a 3D Printer at work but its only PLA so quality isnt so good and it isnt too strong, I may be able to use it to print prototypes for fit then outsource a better print. Do you use a company for your 3D printing or are you lucky and have access to one?

I';ve found various places online however i';ve no idea who to use..

In my Tarot Ironman 650 I fed the wires down through the arms from the ESC, ended up with long wires but it worked ok without any further mods, But when I found out that I had 70g of cable extensions I went back to 450 as that setup wasnt big enough for the 650.

[al-xg]

I printed the FDM abs motor mounts at the Cambridge Makespace. I use a polyjet printer at work but for the SLS, I';m thinking of trying out www.3dprint-uk.co.uk. I';ll fit a few sets in to make up the minimum order quantity. I don';t think the SLS parts will be that resilient either but hopefully the various nylon fasteners I am using in key places will help avoid too much damage in crashes.

I';m using 12A KISS ESCs  which I am so far quite impressed with so I feel I should try and keep to the spec if possible. (external cap required if battery wires go over 200mm)
I';m also planning to add a few cells to my NCR18650B Li-Ion pack and flying with that so I need to be a bit careful if I want to keep all the components alive and healthy.

[NorcoT]

That company looks good, I may do some Finite Element Analysis on the structural components in my spare time at work to check if they';re strong enough from SLS printing, would definitely be one option.