It's slow going these days but still ticking.

openrc-devel
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(André Roy) #1

It’s slow going these days but still ticking. I haven’t flown RC in a while either. Just wanted to share my panelling pattern. Check the direction of the grain, especially important at the nose. These are 3"x 1/16" balsa sheets I got for cheap online.

193d3f8bae4f42dae8784de87ca62b76.jpeg

(D Myers) #2

Always nice to see your work. Looking forward to first flight of this version.

(André Roy) #3

I’m getting nervous thinking about it this time around. So invested in success.

(Michaël Memeteau) #4

Out of curiosity, did you try printing the panels (2 or 3 very thin layers. total 0.25 or something?). I never did, but it occured to me several times…

(Brook Drumm) #5

I’m building a big printer… Around 3xNx3’. Do you think the wings would work as a single walled (1-2mm thick) print. Thinking about filling it with expandable foam.

A two part mold would be interesting as well. Print the two mold firms, spray it with release stuff (don’t know what to use or call it), fill w foam, then split the mold and see if it flies.

I could easily print the mold in a few hours. If it crashes, who cares… A new plane would cost a few bucks and take very little time to make.

Motors and electronics could mount to printed parts in some sort of a quick change module.

Foam could be easily sanded and even painted for a slick surface.

The printer is a very cheap approach to do very large objects quickly at low resolutions. Considering spiral prints with no infill or at least very low infill. Holes in the top of the mold for overflow.

Thoughts?
Brook

(André Roy) #6

Hey @Brook_Drumm ,

These ideas are certainly feasible. But I’d probably create a new design around these fabrication techniques rather than modifying the OpenRC Swift. I’ve made epoxy filled 3D printed surf board fins before; similar in concept.

I also like the idea expandable foam construction, either filling a skin or mold style. Would make producing multiple copies much easier. A fellow called @Steve_Johnstone did mold making for a microscale EDF jet using an SLA printer to make molds. It’s neat project.

I’m still wanting to start up a new aircraft design after OpenRC Swift. I’m still working on my axial compressor designs (I just resolved a technical issue with printing them yesterday!). If you are wanting to experiment with these ideas I’d be happy to collaborate.

Gotta keep pushing those limits.

(Brook Drumm) #7

I think foam would be a great fit for your new power plant! Let’s collaborate. I like the mold idea for expanding foam. It could even take advantage of carbon fiber rods. If you break the plane, just cut out the rods with a hot knife.

Standardized servo pods , electronics and battery pods could allow quick swapping to a newer or different design and for quickly salvaging crashed planes.

One question to ponder: if volume comes at almost no cost, how would you change the designs to protect the props? Larger AND lighter designs for quads would be a huge payoff if they protected the props. Plus, they would float!

Maybe large airplanes and drones are a good use case to prove this huge printer design I’m working on :wink:

Brook

(Jason Kelly) #8

if you used an expandable foam would’t the wing flexing break the foam structure?

(Brook Drumm) #9

Carbon fiber inserts should supply ample rigidity

(André Roy) #10

Agreed on Carbon fiber spars.

Some study of mold-making would be in order. I know next to nothing about expandable foam. Though, I have made molds for fiberglass construction ducts before; used PVA mold release.

Eventually, we’ll have to design those standardized servo pods, electronics and battery pods. We’ll need a common platform for producing CAD drawings. We’ll have to choose a target application so we can develop a design around that; what are we designing this airframe for? A big airframe is good (landing strip needed) as I was thinking of scaling up my powerplant :|.

Perhaps the first true step for us will be to make a very simple, and probably reasonably large wing mold to establish the feasibility of the manufacturing methods before we go head long into designing an airframe. That would be an interesting first sub-project. A wing mold would likely be 2 pieces (top and bottom), likely with a few ribs inside to hold a spar accurately in position.

This is sounding pretty interesting. I’m pretty keen to explore collaborative hardware design methodologies.

(Brook Drumm) #11

Is a glider out of the question? I got to ride in/ fly a glider a couple months back and it was awesome. I haven’t seen any glider projects… I like to do different stuff. Maybe a super light weight glider with a huge wing span… Large enough to trounce anyone who thinks they have a large printer. My printer project could make actual life sized wing molds… No limit on the y axis. But a large scale model would be cool… Just scale the size to the power plant. Perhaps the goal could be long flight time for video shoots or fpv flying.just looking for a niche. Are there worlds records posted for home built rc planes? It would be fun to go for a record. Getting a little media attention would be fun. Putting a wifi network in the air would be fun… I think facebook and google are doing this type of thing. I know the yelp guys that did burrito bomber… They have a delivery app they made for fun to deliver burritos :wink: I put a Printrbot on their weather balloon and 3D printed at 110,000 feet!

Which makes me wonder about an altitude record.

The other idea would be to best the speed of the “fastest 3D printed drone” stories I saw recently. I know we would need big power, but trading flight time for speed would be fun. If we can’t push the limits, why bother. :wink:

Heavy lift could be fun. Big wings and big power. With all the buzz around drone deliveries, why not break the record for low price or quick build time from mold pouring to flight. I’m sure the military isn’t interested in long flight time surveillance drones for a few bucks… Or high altitude planes for pennies :wink:

Last idea: just set a low budget and see what we can do within that budget. Something that stands out.

Side note: I bought material to build an inflatable rc plane… Helium anyone? Google inflatable airplanes… Goodyear did a whole series for the military way back in the 40’s or 50’s I think.

Brook

(Michaël Memeteau) #12

@Andre_Roy Regarding a common platform for “distributed” designing/developing, there is a very strong contender I’m very happy with. It’s relatively new but issued from a very experienced team at the same time (they funded/created Solidworks!). Try it, it’s amazing: https://www.onshape.com/
The advantages for this particular usage would be (to make it quick):

  • It import/export all standard CAD formats;
  • It runs from the browser (no license required);
  • It’s parametric (very good for prototyping, no need to re-design things from the ground when doing changes);
  • It’s collaborative (several people can work on the same part at the same time! You can even see in real time the changes being made by a third party);
  • Branching/forking “à la” Github integrated (easy to work with variants, explore new possibilities);
  • Export directly to STL. Since it’s a solid modeller, the exported files are always “clean” (not like SketchUp sometimes);
  • It’s free if the models are public, which make it “maker” friendly;
  • Last but not least: it’s very very user-friendly (even more if you know Solidworks already, which I didn’t by the way);
    I’m not affiliated with them in any way (so far at least. If you need help in any way to bootstrap this, count me in! :slight_smile:
(Brook Drumm) #13

We use and endorse fusion 360 for collaborative design. Lots of reasons to use this. Our printers are in Spark and Print Studio already. We are integrating their cloud services too-- healing, slicing, etc. free for makers.

(Michaël Memeteau) #14

… Ok, I understand if it already a consensus, it doesn’t make sense to change. I thought that you were looking for something to serve the purpose.

(André Roy) #15

The glider idea is a good one, and poses interesting engineering challenges, but I think we’d be better off tackling a powered airframe. One of the few complications is you need a tow plane.

A heavy lifter or high speed application interests me. Tackling a general application where there’s a definite need is good for drawing interest from folks with money or time. So for me, transportation of goods is a good application, and high speed for search and rescue is another good one. A third good application is aiming at RC hobbyists by making a scale model. I remain open and we don’t have to choose an application or design before we can demonstrate the feasibility of the fabrication technique. Any examples of large FDM molds being used in the wild? I think we can work on a very simple wing mold rather quickly to demonstrate the concept.

It will need to be able to take off from a grass field and be able to qualify under hobbyist flying restrictions, so that puts limits on the size a bit. But we can still get pretty big.

I agree on creating a budget. We’ll have to keep a continually improving estimate of the costs of producing one of these. We could find that the project is too costly to develop as a handful of ragtag hobbyists. But we should start playing around with ball park numbers. I have a feeling that this project may wind up being cost prohibitive, but it’s worth going through the feasibility exercise, somewhere on the scale of large to small airframe, is a size that is suitable for a small budget.

We’ll have to stay under 25kg to qualify for model aircaft regulations. We can try to identify a suitable airframe size and estimate the size of a power plant required. I bet the motor, servos and batteries will be the costliest.

Gonna take a bit of time and start crunching a few numbers.

(André Roy) #16

I could easily get down with Fusion 360. Will see if I can find an inexpensive machine that’ll run it. Christmas is right around the corner. My only Windows machine is 32bit and won’t run it… :frowning:

(André Roy) #17

Polyurethane foam? https://www.youtube.com/watch?v=uvH11W6HozM

(André Roy) #18

@Brook_Drumm , How big are you thinking? a 1/4 scale Piper P/A 18 weighs about 8kg, has a 2.7m wingspan and a length of 1.8m. The cost of that off-the-shelf airframe alone is 700$.

The cost of the most important hardware/electronics that needs to go in it is another 900$ (servo, recvr, esc, 1batt, 8 servos, rcvr batt, BEC, misc HW).

I think the cost of us making the first airframe, producing molds, cost of foam, cost of carbon fibre etc… will likely be about 700-1000$ (all additional prototypes being much cheaper). Cost of foam is cheap, the cost of printing the molds will likely be most significant. I’m just eyeballing the cost of that conservatively since I’'m not sure how to judge the volumes of the molds.

So conservatively, I estimate the total expense of producing 1 flying prototype could be pegged around 2000$. I’m not counting the value of time, effort or costs of producing the design or the project hosting.

(Brook Drumm) #19

Something sexy would be cool. Perhaps the airframe could sell to recoup cost. I would want it to be the biggest fully 3D printed plane… Trying to decide if people will disqualify that claim if filled with foam or if it has carbon fiber spars. Anyway, crushing the current records would be fun. I’ll cover cost of molds and electronics.

Any thoughts on what plane? Are there existing models out there? Think of something desirable and good in photo shoots :wink:

Brook

(André Roy) #20

I put some thought into it a bit but I’m not sure what plane to make. It should be a consensus choice, maybe we need to brainstorm ideas.

Here’s a quick scale model idea: a C-130 Hercules with Civilian livery: https://upload.wikimedia.org/wikipedia/commons/c/cc/Lockheed_C-130_Hercules.jpg

The choice we agree to will have to be something not too complex and easy to design and build since noone is really getting paid.

To the OpenRC community: I think Brook is going to be producing the molds and the first prototype for us. I can contribute research and design time and can help organise the project. This is going to be a lot of work but it doesn’t have to be. Without your help, we’ll be forced to keep things simple to minimize the level of effort required.

None of us have ever used this building technique before, so there will be a learning process here in learning how to do it. If we do this, I’ll get a page setup on http://openrcproject.com to help us organise the work and knowledge required for this project.

Here are a few questions that we need to find answers to:

-What plane are we making?
-Are we doing negative molds [all foam, no plastic outer layer] or printing the skin and filling with a foam core? Or both?

Anyone want to learn mold making for expanding foam with us as a way of rapidly prototyping aircraft designs? Want to learn how to design aircraft?

What I’m interested in with this potential project is the experiment in collaborative design and beefing up those CAD and design skills.