AcrodusterComments Off on Nothing like a good plan..
After many thinking’s and deliberations, I came to the conclusion it would be better to build the bottom wings first. The mounting points are already fixed to the fuse, so their alignment is hardwired into the frame. When the bottom wings are done, I can align the top a bit easier.
I had planned on making the spars from sticks I have saved for 15 years now. They are vintage, but appear to be in good straight shape. These were once destined for a Waco project that never took off. There’s enough of them, and laminating thin strips gives a nice strong spar. Rear one is approx 26 x 7mm.
I hope that having wings will make other parts easier. (famous last words.) The wing structure is going to be per full size, the hard way. The spars are what carries everything, and fore/aft stiffness is provided by 1″ alu tubing. The stuff that would be available is actually heavier then stainless steel, so I am going to use that. Which means I also need to make brackets for those tubes. And when I am at it, do all the other bits I need as well.
Glueing strips together is not that exiting, but this is the result.
And for the rest, a bit of sanding and shaving to get to the correct size. I love the smell of pine!
Today was officially the first day we were allowed out again. Corona has not disappeared, but is becoming less of a problem. Technically, when the infection rate stays below 50/100000 people, the hospitals can cope. So it’s not over, it’s manageable.
I made 2 trips to the field so far. The only thing I need to look at is getting at least one, better 2 mirrors, to see what is going on behing my back.
I got a nice envelope of Bling last week. The process of getting from the parts I drew to something in my hands is not that complicated. Submit a dxf file, receive a quote, say yes, wait a few days, done. And the good part is, it is not breaking the bank!
The one thing that I had to learn is that a ‘part’ is a single dxf file. What you see here is a single file. Why is this important? The handling and preparation fees deal with single parts. There appears to be no limit to how complicated the parts is (apart from obviously the amount of time the laser needs to cut).
To keep it simple, stick as many individual bits together as you can, to produce as large a part as possible. That gives you the cheapest part. Unless of course you want a 1000 of each individual bit, but then we talk something else.
All I had to do is cut the bits apart, do a bit of filing and sanding an you’re done.
So next is doing some trial fitting, and start building the center section of the top wing. Once that is done, the cabane structure etc. At the moment there is a build thread on biplane forum, at just about the right stage. I’ll add some of these here for comparison
This is the first trial fit for my new bike trailer. I still need to do something on the rear so that there is less change of anything hitting the nose or prop. Wings fit too, and even I can squeeze on the bike. All in all happy with progress.
Update 30 April: There was no easy way to properly secure the connecting pin to the saddle post. (If only I could weld). Most of the bike frame is alu, and I did not want to chop up too many things. The solution is what can be seen here. I also added some bling lights to the rear of the trailer, and 2 batteries for charging plane batteries. (2 x 13Ah)
Update 1 Mai: Went for a short drive, just to test road stability and handling. If it was a plane, I would think it works as designed, don’t touch it!
With the added mudguard and wheel bearings and other small bits, the Hitec 645MG is struggling to get the gear up. There is a point halfway between up and down, where max force is needed, it’s just how the design of the gear works. In theory I could redesign everything. (Yup, maybe sometime soon). Or I could add another voltage regulator to give it it’s own supply, 6V would work (most of the glider runs on old 5V gear), or solve it for now with slightly more powerful servo.
I found a SAVÖX 1256, which has probably twice the torque of the Hitec, so will strap that in for now.
Of course with the way I wired things up, that’s easier said then done. Since I installed a 9 channel Rx in the plane, and needed an extra channel for the Flashy Lights, I came up with the cunning plan to use a single channel for multiple things.
In short, gear up or down is only 2 positions. Light on/off same thing. So why not do a bit of mixing and send the resulting servo signal to an Arduino-Pro-Mini, and let it drive the LG servo and Lights. I cooked that software a year ago, knowing it was a quick fix for a self imposed problem. (That’s what this hobby is all about, if you don’t have a problem, make one!)
Anyway, long story short, the pulse that the servo needs for up or down is hard coded in the software. No biggy, but it means it’s not very convenient when you change servo’s.
Oh, it’s sooo much fun. With the aid of my little magic ToolkitRC.com M6 I measured the output pulses to the servo. 1000-2000mSec. Perfect, but the servo only rotates 90 degrees and a bit? (By the way, there is an software update for the M6, V1.31 dated 23 March 2020)
Oh dear. Now what. Time for a rethink, and do remember in future that you really want a 180 degree servo!
After some reflection and relaxing in the sun, I remembered that I used to convert servo’s to 180 degrees by adding a few resistors to the feedback pot. That triggered of course the thought ”did I maybe modify that servo?”.
And the answer is yes, I did! Funny enough I posted that same fact on 3rd Dec 2016 on my Facebook account. Oh where would I be without my facebook memory. Scary..
Well that sure was a fun exercise for a locked-down Saturday. So next question is: Am I going to modify the Savox? The answer is below. Same trick, 2 * 1.5kOhm resisters either side of the potentiometer will do the trick. Funny this servo is rated to produce 4096 steps. It never stops to amaze me how you can get that resolution from a cheap 5k pot. But they work, so I’m not counting! by the way, there are no wires in this servo, which should make it more reliable (cheaper). But it does mean some sort of skill is required to remove the pcb!
And while at it, might as well try to sort out the wiring mess a bit. I’ve got some space at the top of the fuselage, out of sight.
By the way, that stepdown converter acts as a current limiter as well. Max current the chip will produce is 4 Amps, stall current for the servo is 5 A. Should be safe. And since it is only ever used for up and down, it is not likely to get warm. And if it does, it will disconnect, saving the battery. In theory this is what is supposed to happen. Real life might work differently.
So, that’s enough for Corona-Easter-2020. Left’s hope and pray the world will not have to repeat this ever again!
Corona, DG800Comments Off on What a difference a month makes.
To say we have never experienced anything like this lock-down is an understatement. We are lucky to live in a nice place, with lots of space, so we should be ok. Even if this madness takes a lot longer then the official guestimates that our gov’ment now spreads, I will keep myself entertained.
Saying that, I managed to mess up my back (again) which sorta restricts my movements at the moment. Hence the lack of stories.
I have finished drawing the metal parts for the SA-750, and are waiting for the nice laser people to cut them for me. Obviously my parts are low on their list of things to do, they likely have other more immediate pressures on their business. Never mind, lots to do.
Last year I hardly flew the DG800, mostly because our field was dry, so unbelievable dry, that the stake I use for the bungee did not hold. I once had that metal spike flying in my general direction, and that was once too many times. I’ll try to think of a better solution for tying down the end of the rubber. I probably need at least a double stake, and most likely longer and heavier. And that’s the pita I want to avoid, I don’t want to drag all that stuff to the field. I’ll have a think about it.
At the moment the field looks fine, I could use the single stake, but you guessed it (or not if you read this in years to come) we are closed for business due to the Corona virus. Sad as it is, we are a sport, and all outdoor and indoor sports have been banned. It does not seem logical to us, but the gov’mnt does not have the time to look at each sport in detail to see if it makes sense. So, everybody stay at home, no exceptions.
So, do some maintenance. I knew I had a flat tire. Sorted that by inserting a length of silicone tubing inside the wheel. (I know, I could have bought a new one. No Fun). Then, since I have them, added some bearings to the wheel, that never hurts. I also wanted to make a mudguard, just to see if I can.
The plan is to print the form (positive) slap on some fiberglass and see if it looks like something I want to use. Right now the vacuum pump is doing it’s best to maintain -0.6Bar. I lost the manual for the little thingy that decides when to turn on and off, but it seems to work, so will look for that later.
I would be better off giving the walls a slight angle, so that it is easier to pop of the form. With this version I had to split it to get it to loosen. But in the end, no harm was done, and it looks good enough for now. If it survives, and this lockdown continues, and if I am getting bored, I’ll do another one. This one is approx. 8 layers of 25 gram and one of 225 gram. I have miles of the thin stuff, I use it to get a nice surface. (It was nice until I had to split it in half to release form the form 😉
3D print, DLGComments Off on How the Blaster-1 became a E-Blaster
As I mentioned the other day, I decided to turn the Blaster into something Electric. Mostly because I don’t know what else to do with it..
All up weight is now 435 Grams, so that is 81 grams more then without the E. Don’t know how I got the 19 grams earlier. Still happy with it.
The spinner seems to have a slight imbalance, but with a 2S lipo and low rpm it stays together for now. Something to look into later. First we needs some test flights. I also need to think about keeping the prop tight to the fuse. The usual rubber band trick will probably be employed once it flies.
So what’s the plan for launches? Not sure yet, toss it like a normal DLG and hit the motor switch once you release? Need to remember this one has a history, so full power launches will be a bit scary. Anyway, we’ll see.
It actually looks quite nice. Sadly the stab and rudder have some damage caused by a once in a lifetime mini tornado that lifted it and tossed into the fence.
Of course I did the smoke test today. Mounted the motor, connected a 3S battery and hit the throttle.
I ran the Emax 2204 motor for 10 secs before I could fry an egg on it. Hmmm, maybe I should have looked beyond ”it fits”?
An 8*4 prop is not quite the same as a 5*4 drone bit of plastic. No problem, what else do we have in the BigBox of Stuff? Ah, look at that, sort of ancient history here. A HET-RC Typhoon Micro 6/3D. More or less the first motor I got just before the foamy craze started.
Weight : 35 grams
KV : 1460
Max Current : 12 A
Power Nominal : 90 Watts
Recommended Props: APC E 9 X 4.7
The 9*4.7 is what is relevant here. Ok, lets see what E-Calc says:
50 Watt on a 2S Lipo with almost 4.8 m/s vertical performance at 370 gr RTF, and a 5 mins motor run on a 450 mAh battery. Ok, no problem. Lets go!
Getting a bit nostalgic there while looking for the plane with that Typhoon. At the top is my Blaster in good ol’ N-Ireland. It had a variety of radio gear in it, this is I think the Spektrum-Mpx version.
Can’t resist looking back: Yellow Road. With the right northerly you could hang for an hour in the breeze, untill your fingers turned blue. Further back was a similar bowl facing south-ish. That was the better spot. My first flight with the Birdy lasted 30 mins or so.
And I found it! First ever CNC-ed plane. Not a real serious design, just made it, because I could. This was powered by that HET-RC Typhoon. Did fly well enough in the backyard!
While waiting for some parts, I decided to have a go at another project that’s been waiting to be started. I still have my original Blaster 1, RTF is approx 350 gram, and while it was fun flying it from a slope, it always a struggle to throw it higher then 35 meters on a good day. In the meantime I have something black that weighs 220 gram, and does go a lot higher!
That says much about my technique! Anyways, I’m electrifying it. There’s some quad engines lying around, some small Lipo cells that appear to be good enough for a few more flights. All that’s left to do is some radical surgery.
The first cut is the hardest, after that it’s a matter of making enough room for some servo’s and Rx, and somehow getting the CG sort at the right location. As always, I’m using the TLAR technique to get the dimensions right. There’s still a bunch of D47’s from Indoor days gone by, I’m sure I can find a receiver that will do the job, so I’m almost finished, just a matter of assembling a few parts.
I could not find the right size aluminum in my stash, which is a good excuse for doing a quick printed version of a prophub. I have a few 8*4 foldable prop blades, not really fit for this purpose, but I’m not using them for anything else. The first straight center part looks good enough, but then I wanted to have the blades tighter to the fuse. Some headscratchings later I have a fully printed foldable propeller including spinner part. Printing is is just rough and quick proof of concept, not the final one yet.
In the meantime I started preparing the fuse. Those were the days that Vladimir used kevlar for the front end. Real fun when sanding!
Will a printed part be strong enough to hold on to those blades? The answer to the question will have to wait till I assemble the battery. If not, I can always fall back on a proper 5 euro part.
That looks about right! so far 19 grams more then when I started, I need to add some glass around the front end a something to hold the servo’s. Also a small lid to stop stuff escaping. CG used to be at 78.7 mm, 3 mm to go!
Getting the cabane structure built was always going to be one of the challenging bits of the build. So, off we go. With the aid of my trusty 0.01 degree level, I’ve now lined up the fuse and a flat plate that will serve as the build-reference surface. As we speak, I just finished setting up the main center spar. Last week I bought myself a bandsaw from the interwebs. It was advertised as B-Ware, but since the price was right, I figured I probably could fix whatever minor ailment it suffered from. As it turned out, the power switch wiring had come lose inside the frame. I could fix that in about 5 mins. From the same lot I got a disc/beltsander. Also B-ware. The table in front of the disc had some boltholes drilled out of alignment. Yup, big job again. Clearing space for the toys took more time then the repair!
Which all leads up to: I need to cut some metal. I have asked for prices for laser-cutting the parts, but likely I can cut them just as well with the bandsaw. For which I of course need to locate the not so standard size saw. Luckily they can be made to order and do not cost the earth. (as in 15 Euro/pce, made in Germany.)