Designing/making a VTOL (aka V-280 Valor, Bell XV-15, or the V-22 Osprey)
- Thread starter JasonK
- Start date
JasonK
Participation Award Recipient
I am finally getting back to this and am throwing away the sub-250g plans for now and going to work on getting something working first, then see about redesigning down to sub-250g, if I enjoy flying it. perhaps a quad or fixed wing might just be a better flying experience long term.
I am going to use 2 of my A packs for the motors, on 3S with 6x3 props, they put out about 400g of static thrust each, so I still need to target 400g or less.
My current design is roughly this:
leaving 48g for props, 3D printed parts, misc wires, push-rods, FPV camera (5g), any other remaining bits. So I suspect I am going to be a bit under 2:1 thrust to weight ratio for the initial build. The ESCs definitely are on the heavy side (don't need the BECs and could do without the connectors, etc and I believe they are a bit over speced for the motors). This is rather unfortunate as there isn't a whole lot of weight to be saved on the electronics as it stands and that is where the majority of the weight is currently coming from.
It might be worth checking the weight of a box tail boom made of foam-board as that might be able to save some mass over using the wood rod, but wouldn't be as strong. (I think this could save 10g over the wood rod).
The wing is the majority of foam in question, which will be about 35g if I did my math correctly, the tail will be ~10g of foam, 5g for the FPV camera... which leaves 0g for the power pods, push-rods/etc. With some creative work, I might still be able to pull off close to the 400g goal.
I am going to use 2 of my A packs for the motors, on 3S with 6x3 props, they put out about 400g of static thrust each, so I still need to target 400g or less.
My current design is roughly this:
Part | Weight |
WingSpar - 18" wood rod | 30g |
Tail boom - 12" wood rod | 20g |
4x 5g Servos (flaperons & Vtail) | 20g |
2x 14g Servos (Motor Pod Tilt) | 28g |
2x FT 1806 2280kV Motors | 36g |
2x FT 20A ESC w/XT-30 | 56g |
1300mAh 3S w/ XT-60 | 122g |
F405 Wing Flight Controller | 30g |
2x Servo Extensions | 10g |
It might be worth checking the weight of a box tail boom made of foam-board as that might be able to save some mass over using the wood rod, but wouldn't be as strong. (I think this could save 10g over the wood rod).
The wing is the majority of foam in question, which will be about 35g if I did my math correctly, the tail will be ~10g of foam, 5g for the FPV camera... which leaves 0g for the power pods, push-rods/etc. With some creative work, I might still be able to pull off close to the 400g goal.
JasonK
Participation Award Recipient
my goal is specially to _not_ have separate hover and flight motors, to use only 2 motors, and not have a tail sitter.
JasonK
Participation Award Recipient
looks like the CG calculator likes a slightly shorter tail boom (-1 in) then what I had guess in my drawing, this puts the suggest GC right at 2" from the leading edge, which puts it right in the middle of the expected spar (which is where it needs to be for hover). and the CG should move slightly forward (or not at all) when the motors tilt forward.
https://www.ecalc.ch/cgcalc.php?dee....90;3;2;0;0;0;0;1;0;0;0;0;4;0;0;0;0;10;25;10;
https://www.ecalc.ch/cgcalc.php?dee....90;3;2;0;0;0;0;1;0;0;0;0;4;0;0;0;0;10;25;10;
JasonK
Participation Award Recipient
I got v0.5 of the tilt mechanism working in my hands. Still needs a few bits fine tuning of how stuff fits/etc. to get it all to be stable on its own (first print, some of the parts didn't fit.. made them slightly bigger and they got sloppy... have to find that happy middle..
L Edge
Master member
That is why Tom went to the later model he developed.
JasonK
Participation Award Recipient
most of my printing problems is that my printer tends to the dimentions of things off ever so slightly... so for example a part that should have a 10mm hole in it, I have to make the hole 10.25mm so it prints at 10mm. This is rather random to some extent and not just a general scaling issue. Perhapse slowing down the printer and spending a good chuck of time tuning it, _might_ get me more dimentionally accurate prints... but when we are talking errors this small, I don't know that spending that time will actually gain me anything.
JasonK
Participation Award Recipient
more progress!
I have the wing mostly build (still need to put in the servos for the flaperons) and a temporary attached tail boom and mock tail, just to get some visual reference to what it is so far (The tail is currently planned to be a Vtail).
I need to put in a few screws, just to keep things from coming apart in flight (the gears on the servos can currently pop-off and the shaft through the bearings isn't attached to anything in the spar, so could come loose in flight.
I have the wing mostly build (still need to put in the servos for the flaperons) and a temporary attached tail boom and mock tail, just to get some visual reference to what it is so far (The tail is currently planned to be a Vtail).
I need to put in a few screws, just to keep things from coming apart in flight (the gears on the servos can currently pop-off and the shaft through the bearings isn't attached to anything in the spar, so could come loose in flight.
CampRobber
Active member
https://www.racedayquads.com/collec...oducts/spedix-20a-esc-lite-dshot-600-blheli_s
4 grams. In addition to being heavy and having dumb 7805 BECs, I'm not sure if the FT ESC supports anything besides standard 50hz pwm. That isn't ideal from a fc/stability control point of view. Any kwad pilot will say Oneshot125 is like BARE minimum but dshot is easier especially if you have several.
Or a carbon fiber arrow shaft or tube. Every mad scratch builder should have a go-to light strong composite hollow rod.
I've been building some boats recently. Just ladling on epoxy with no regard to weight. It's awesome. But I have two of those FT1806s on the way and this thread is interesting to me.
JasonK
Participation Award Recipient
thanks, if I get this airborn and want to keep working on it (getting it down to 'exacting' measurements), that will be helpful.
I looked up some carbon fiber stuff and was having trouble finding the size/strength/weight ratios I needed... and the wood rods were handy.
absolutely.... I am interested in what happens with remote ID... because it might make or break this project long term (250g seems to be a challenging mass point for something like this, given that many things don't scale linearly with size.)
CampRobber
Active member
Yeah, definitely harder than just a vanilla airplane. I'm thinking I might build one with ducts and stubby wings, sort of avatar gunship style. It'll be an interesting project and can be tested indoors. Besides the FAA I'm also dealing with winter here.
JasonK
Participation Award Recipient
yah, if wanted to just do the avatar gunship thing, it would just be the 2 motors and 2 servos, wouldn't need the wing surfaces. Maybe a 3rd servo for an elevator on the tail, to allow more forward speed without nosing down as much.
JasonK
Participation Award Recipient
got it mostly built. Just need to finish the one power pod, and wire them up all the way and I could test hovering.
Still need to install some servos for forward flight.
Getting the CG right is fairly tight, still have to figure out how I am going to mount the battery in a way that can't slide around.
Still need to install some servos for forward flight.
Getting the CG right is fairly tight, still have to figure out how I am going to mount the battery in a way that can't slide around.
CampRobber
Active member
My plan is to get it flying indoors but design it in such a way that wings could be inserted later. Yes, an elevator would be required for that, though I'm not sure whether I'll bother with other control surfaces.
What is the vertical offset between the battery and the spar/tilt axis? In that photo it looks kinda close.
What is the vertical offset between the battery and the spar/tilt axis? In that photo it looks kinda close.
JasonK
Participation Award Recipient
looks like ~33mm from the top of the spar to the top of the battery.
battery is about 125g and my AUW is looking to be about 420g (I am trying to reach 400g or less, to get a 2:1 thrust: weight, but this is the first pass and doesn't look promising to reach that).
battery is about 125g and my AUW is looking to be about 420g (I am trying to reach 400g or less, to get a 2:1 thrust: weight, but this is the first pass and doesn't look promising to reach that).
CampRobber
Active member
My understanding of bicopter physics is that pitch authority is proportional to cg-hinge vertical distance. I think the reason Stanton used the droopy fuselage pod was to hold the battery lower. It looked closer than 33mm, but I'm not actually sure what distance is required.
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