Is this a gamechanger?

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Nov 052019
 

There are many CAD programs, almost all of them require a large investment in time and ofter money.

I just discovered shapr3d. It looks awsome. I don’t say this lightly. But it looks to me like this is going to be a gamechanger.

I managed to create this cowling as a test-object.

Is there a downside: yup, it needs an ipad. So far I’m lucky enough to be able to use the one provided by my boss.

 Posted by at 8:11 pm

Elevator servo stuff

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Nov 052019
 

Servo needs to be hidden under the seat, so I built some bits to do just that. I also used some metal u-channel to mount the servo. All overkill of course. I also remade the pivot of the control stick. The washers I has used had an internal diameter of 3.2mm. The bolt was 3mm. Very sloppy! Same with the link at the bottom. It took some time, but now it is all slop free!

 Posted by at 2:20 pm

Elevator control chain.

 Acroduster  Comments Off on Elevator control chain.
Nov 032019
 

Need to get from the (future) servo under the seat to the back-end in an orderly fashion. I’m using the full size method as guide. Main part is the reversing bar behind the seat. It has to be zero play. No play, whatsoever. After the usual fiddling around for a while, I got it sorted. It’s a once you install it, you can never change it construction. Failure here is no option. The bolt at the bottom prevents the assembly sliding out of the bushings. It does not support anything. The 2 little square supports were reamed out to provide a zero play bushing.

Next will have to be the construction of the stick assy, and the mechanical interface to the servo. Lot’s of fun ahead!

pushrod is for illustration only.
and something for the pilot to hang on to.

I am only installing the main stick, front seat is ”occupied”. Not sure yet if I am going to use a separate servo(s) to drive it. Separate seems safer, since there is a reasonable mass in this contraption. Might build a pilot with power arms 😉

full down..
full up, looks like it’s enough..

The stick has to be fixed with AN4-22 bolt, 4 washers, AN310-4 nut and a AN380 1-2 cotter pin. Yup, M3 bolt and nut will do fine! (for the curious: AN4 is 1/4 ” = 6 mm. So 2 mm would be scale. Since those 2 mm bolts are usally quite soft, I won’t waste my time installing one, they will rattle loose in no time at all. The nut is a castle nut so you can put a cotter pin through the bolts hole to stop it going awol. I know you wanted to know all this.

..more tail-bits..

 Acroduster  Comments Off on ..more tail-bits..
Oct 282019
 

..many times you have to make parts before the other parts that need to go on before the parts that you need to fit to get the job done. This was one of them. Needed to make more hinges. Not difficult, just fiddly, and a bit dodgy, since I try to cut them on the lathe, with a dodgy china cutting wheel going full speed. However, hats of to the china-folk, I have not had a single one fail on me. So far I have used approx 20 odd discs on this project.

cutting some hinge-parts.

After checking the tail, I noticed the main spar was bend. This appears to be almost inevitable when you heat bits. I decided to simply cut the middle, and add a sleeve. Problem sorted. My metal working skills don’t go so far that I can predict how much distortion I will get. Of course I could make very expensive, very heavy jigs. yup, I could..

fudge, I had to cut the front, because the rear was not straight after brazing..

A bit of a showoff.. Starting to look like it wants to fly!

1569 gram, still smiling

Just one more weighing session. 1569 grams as seen here. Good stuff!

enough done for today!

And I am calling it a day. All in all it does not seem much, but I am happy with it! The section above weighs 300 gram. As a comparison: the ”light” elevator from my 2.5 meter Extra weighs also 600 grams. Ok, there’s 2 servo’s included in that figure, but still..

Finished the rest of the elevators today, another milestone reached! Also bolted the motor back on to get a feel for the CG. At the moment I am still slightly nose-heavy, so things are good! I don’t expect to have to add any of the grey gravity stuff.

yes, that’s 288 grams!
That’s the elevator horn-thingy sticking out there. Added a bit of wrap around as well.

The rear stabilizer mount consists of a single bolt, as per original, the front is made up of a few gussets. I probably simplify that part. Not sure how, but simpler as original. (too many small bits that fall apart when you heat things up, is the main reason)

Lets make some tail bits.

 Acroduster  Comments Off on Lets make some tail bits.
Oct 262019
 

The plans call for square tube at a few locations. I don’t think it will be a problem to use round tubing. As usual, use what you got! I also don’t think I have enough space for the 2 central bearings, another fudge expected there.

remember: full size!
..bend some tubes..

My template has a more rounded outline at the outer elevator. Might have to redo it, since the big one has a smaller radius.

test fit, looking good.
..and preparing for the next fun parts

More FreeCAD exercises.

 Acroduster  Comments Off on More FreeCAD exercises.
Oct 122019
 

I’m trying to get the steps needed to get this fuselage shape drawn documented. This will be the part that the undercarriage has to connect to.

Insert the image
Scale it to the correct dimensions
Shift it to the 0,0 origin (just for easiness)
Draw a B-Spline curve
Do another and shift it backwards 190mm
Select curved shapes, identify the 2 lines, and voila!

The back curve should have a sharper corner, I’ll work on that. Next step is adding the leg and try the fillet parts…

And we have a leg. Next the hardest part yet, a smooth transition between leg and fuselage.

It ain’t working the way I want it to..

 3D print  Comments Off on It ain’t working the way I want it to..
Oct 082019
 

I’ve come to a grinding halt with OpenSCAD. Pity, but so is life. I learned a lot, and maybe, just maybe there are tricks to do what I want, but since my maths-magic is not that strong, I have decided to stop using it for this project. For quick jobs it certainly does work great. But as soon as you want complicated surfaces, it no longer has the ability (I don’t have the ability) to make it work for me.

But there is an alternative. For too long I have put off using Freecad. Mostly because it takes a lot of learning. So as always, jump in and stick with it. I generally know what I wanted to do. Trace an image (scale it of course) and create a form that can be manipulated. Some tracing something usually involves lots of not so straight lines and curves, the magic words are B-Splines. But between ” it can do that’‘ and something that can be used by me, takes a few hours of hard labor.

Anyway, before I loose it, here is the first ”thing” I made, basically the front part of the fuse, extended backwards. Next I need to copy that to a similar shape, but with slightly different bottom section. It sounds easy. Yes, in a few years I will say that.

The shape I created peeking through the image I used as template.

..and in between I had a pc that blew up, not sure if it is hardware or software, time will tell!

 Posted by at 6:45 pm  Tagged with:

This part time retirement is fun!

 3D print  Comments Off on This part time retirement is fun!
Oct 012019
 

Another day of shed-time, life is good! Continued cleaning up, while the print-slave does it’s printing. (don’t want to leave him alone, in case the dreaded grey electronic smoke escapes. As is well known: All electronic equipment works by the grace of the grey electronic smoke contained therein. As soon as it escapes, your system stops working!)

Anyway, as I said yesterday, I’m not having much luck with Simplify3D, maybe it always was like this, maybe I just forgot. Whatever, Cura in it’s present incarnation does the job very well indeed. Never a bad thing to have another slicer to fall back on. So today was undercarriage day. Got one legwarmer printed properly, weight is 30 grams. 2 walls, and 8% infill. The 1st one had 4 walls with weight to match (60 odd gram)

The next step is designing the cuffs between legs and fuselage. It looks complicated (it is) but if you start with simple forms, and add on from that, it should all be ok in the end. It’s just a matter of stacking the right size of cylinders, cubes and various other bits of magic together. (Hey, I have to convince me-self that it is simple.)

The end result is sitting in front of the screen, but this black PLA is impossible to photograph, so take my word for it, it’s nice 😉

multitasking!
Cura sliced the Openscad design on the right, finished object in the front.

..and no, I have not stopped working on the SA750, this is all part of the fun. I need to make that turtledeck, and the nose-cowl, and various other bits. So, it’s all part of the same game! (oh, and who knows, a driver?

 Posted by at 6:16 pm  Tagged with:

A few 3d print notes

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Sep 302019
 

As always I manage to find the bugs.. Just do quick test for the PT-17 legwarmers.

The design was easy, so what can go wrong. I have been using Simplify3D for a long time, always did what I asked it to do. Until now. I asked it to print this very simple structure, but for reasons only known to it’s inner self, it prints the outline and infill and ignores the internal tube. Ok, well if you don’t want to play, there’s always Cura. And lo and behold, Cura plays nice. Ah well, so I let Cura do the slicing and upload the result directly to the Octopi, and all is well. Pity this is, because I really like(d) Simplify for other reasons. I guess I’ll have to dive into the interwebs to find out the why..

Meanwhile, my Printslave is doing it’s bestest.

important bits of code are there, so that I don’t loose them!
..always fun to let others see glimpses of the workshop 😉

yeah, I need to add some lights at the back of the camera, now where did I put those leds again?

oh, yes the link to the original code: https://github.com/ErroneousBosch/OpenSCAD_airfoil

Openscad again.

 3D print, Acroduster  Comments Off on Openscad again.
Sep 232019
 

3 reasons, Ed asked my if I could do something for his latest project, and I really fancy those 1970’s looking flared undercarriage pants as well. So, bite the bullet, and do some thinkings. I found what appears to be a good starting point on github, so let’s see if we can do this. The greatest hurdle for me is the design phase, once I have the .stl file it’s simple.

The 3rd reason is that I am knackered from working in the garden today, SWMBO decided that the path that runs around the garden needs moving.

The program as is does allow multiple profiles sections, but it does divide then equally along the span. Not what I need. So we have two options, fix the code, or make the pants into multiple sections. The first method will require brain-cell activity, we go with that!

28 sept: It’s a bit of a slow week with other jobs taking priority, but things are progressing. Taking the road less traveled is definitely keeping the braincell entertained. I learned a lot the past few days. I managed to get the turtledeck drawn, and I thought it was then only a matter of printing. Oh the folly of innocence..

it really looks great, measurements are correct, just print it..
of course it does not fit in my printer, but I knew that.

..so what is the challenge? When I import the .stl the ‘skin’ is either to thin, so that the printer does not see it. (less then the 0.4 mm orifice of the printhead.), or if I make the part thicker is starts to complain in a language I do not want to repeat..

/*
Construction of the turtledeck for the SA750.
Date: 28 sept, 2019
Inspiration: https://openhome.cc/eGossip/OpenSCAD/lib-bezier_surface.html
OpenSCAD 2019.08.04
All rights as usual, do as you please, it's open source. 
*/

include <bezier_curve.scad>;
include <bezier_surface.scad>; 
include <function_grapher.scad>;

t_step = 0.01; // smoothness, might be too much for real life printing.
thickness = 0.1;
width = 0.1;
inch=25.4; // is an inch
scale=0.33; // my scale

// refer to fuse stations on full size. 
sta75= 0; 
sta100=25*inch*scale; 
sta120=45*inch*scale;
sta125=50*inch*scale;
sta129=54*inch*scale;
/*
Draw the approx formers on a piece of grid paper, and take the coordinates from there. 
*/

formers = [
//former at sta75
    [[-109,0,sta75],[-100,36,sta75],[-80,82,sta75],[-60,105,sta75],[-40,124,sta75],[-20,136,sta75],
    [0,140,sta75],
    [20,136,sta75],[40,124,sta75],[60,105,sta75],[80,82,sta75],[100,36,sta75],[109,0,sta75]],
 
//former at sta100
    [[-75,0, sta100],[-60,55,sta100],[-40,92,sta100],[-20,105,sta100],[-10,120,sta100],
    [0,150,sta100],
    [10,120, sta100],[20,105,sta100],[40,92,sta100],[60,55,sta100],[75,0,sta100]],

//former at sta120
    [[-55,0,sta120],[-30,30,sta120],[-20,43,sta120],[-10,46,sta120],
    [0,50,sta120],
    [10,46,sta120],[20,43,sta120],[30,30,sta120],[55,0,sta120]],

//former at sta125
    [[-44,0,sta125],[-30,30,sta125],[-20,43,sta125],[-10,46,sta125],
    [0,50,sta125],
    [10,46,sta125],[20,43,sta125],[30,30,sta125],[44,0,sta125]],
 
// and a fake one to get the rudder blended in.
  
    [[-44,0,sta125],[-30,20,sta125+6],[-20,30,sta125+12],[-10,40,sta129-14],[-5,65,sta129-6],
    [0,250,sta129+inch],
    [5,65,sta129-6],[10,40,sta129-14],[20,30,sta125+12],[30,20,sta125+6],[44,0,sta125]],
];

//here the magic happens.
            
    function_grapher(bezier_surface(t_step,formers),thickness); 
    
// that's all there is to it. (if only!) If only I had the knowledge I will have in 5 years today, this would be easy.

After a lot of pulling the hairs, I got the code down to the above, it works beautiful and it ‘should’ be simple to build other variants, if, but only if I can get the code to play happy with the printer. I normally slice with Simplify3D. Since I have Octopi (cura slicer) running on the printer, I want to try if that will eat it.

The other slight issue is of course that I will have to chop up the part in 2 or 3 sections, but that should not be a problem. In the end it will be covered with a layer(s) of light glass to keep it from falling apart. The whole idea is of coarse, that modelling in software is ”easier” then producing lots of dust.

That’s the theory..

29 sept: after a good nights sleep I woke up to realize I have a lot of the good stuff from Stefano. Why oh why did I not think about that? The other option is to try with Freecad, import the .stl, make it a solid and take it from there. Options, options. Then there is Solvespace, and of course all the paid for stuff that I can’t afford.

30 sept: ok, this is the reason why this does not slice well: the code likes the shape to bend in certain direction. At the tail end I try to be smart and diverge, creating a bend in the other direction. And that is what is causing the problems for the slicers.