[karla]

After using the eCalc App and experimenting with different motor sizes and speed (KVs),
prop size and angle, 3-4S LiPos, ESCs, and checking where available to buy, I came up with just
having to get new motors and props (10 x 6 inches).
My 20 ESCs seems okay within range.

I settled for 2216 size with 810KV
https://www.banggood.com/EMAX-Cooling-New-MT2216-II-810KV-Brushless-Motor-CW-CCW-with-1045-Propeller-for-RC-Multicopter-p-1004936.html?rmmds=search

Now the design looks more viable:

[kicekilla]

I think those will give you plenty of power... if you havent ordered yet I might even look for something a little higher kv and run 8 inch props...

keep in mind, these are going to burn through your 1000mah quickly... in hover mode at least.

[karla]

Thanks.
I am still in research mode.
I will dive in to it again.
With this smallest LiPo 1200mAh I can only hover some 3 min (according to that eCalc app table in last post), but I have larger LiPos and I just intend to lift off and land with hover, rest and most should be in forward flight.
So far i didn't notice to save energy by faster rpm. The recommendation seems on the contrary to go for the largest prop size you can fit on the frame (up to 1/4 of wing span) then figure out how fast you need to spin it to create enough lift. This is some kind of hybrid between copter and fixed wing so I am willing to try everything 

[karla]

Well i am going through with this selection. Lets see how it works out.
While waiting for the motors to arrive and redesigning the Rotor Houses, I am just thinking in retrospect,
so naive of me to think I could just take whatever I had at home of parts and it would really fly at first shot 

[kicekilla]

haha you wouldn't believe how many parts/equipment I have at home, yet I still find myself "having" to buy new parts because it will work better than what I have haha.

I think the combo you posted will def. lift it no problem.. I am suspect of battery size then. And I think the combo + 10 inch props might be a little bit of overkill personally, but that's just me. Are your servos going to be strong enough to rotate those motors/props well enough? just something to think about.

[karla]

Haha thanks for sharing that. In good company then 

Overkill... maybe, but have the option to prop up/down as needed, at least did some math/calculations this time.
... and yes the new load on the servos/tilt gear mechanism is a source of worry.
Not mainly because using a stronger motor (if used on current tilt design I am not so worried since its almost CG neutral and has no 'leverage' while it tilts around), but due to a new design that I think will permanently fix the CG placement shifting problem in hover respectively forward flight. A possibly negative effect of the new design is that the tilt mechanism must withstand more power than it can take.



The picture show the current design and I am just holding the new design up, its not ready.
While the current have the servo 'hanging' below the motor and the tilt point the new design have servo still below the motor but 'standing on top of' the tilt point. As an effect of this and the new 'higher' motor, the props will be spinning some 80 mm higher than currently.

Wanted, desired effects and uncertain consequences as of now:
. wanted, props spin higher above CG on y-axis to increase stability (no need move LiPo lower)
. wanted, in Hover CG should align over wing spar (center of lift, CL=Hover)
. wanted, in Hover when Pitch motor for or aft also moves CG for/aft and improves control
. wanted, in forward flight CG should move 20 mm forwards of spar to align over CL=ForwardFlight
. wanted, give room for props to spin freely without having to make 'holes' in tip of wings
. uncertain, How will this design impact where forces are applied (vectors) and what outcome?
. uncertain, Will this design increase power on servos, gears, feathering shafts (and its foundations in spar and tilt house)?

Bound to find out

[kicekilla]

looks good, excited to see more. waiting for the new parts now?

how do your gears fit to the servo splines? like just kinda mash in there or is there actually a spline printed into the part? I have tried printing some gears for my bicopter design but my printer doesn't have the resolution to print that small of a spline so I have sized the holes to just press fit, but I don't really like that as it will probably wear out.

[karla]

i didnt even try to print those small splines.
I just glued a standard servo arm to my 3d printed tilt gear



You usually get several different kinds shipped with the servos, I just thought the round ones had more area for the super glue to stick on to.

New motors should arrive next week.

[karla]

I received the new motors and props yesterday
(and new 30 amp ESCs but have them for later, hope my 20 amp will be ok as calculation suggests).

The version 1 weight was 70grams and
ver 2 weight is 128 grams,
thats including tilt house, servo, motor and prop.
basically double the weight but also increased the lift/thrust a lot.
A considerable upgrade.



Mounted on version 2 tilt design.



Will be mounted on the wing spar soon.

[karla]

uhu, when about to mount the tilt rotors on the wing spar I found out the gears are ~2.5mm too close to fit
trying to fix it by making the gear wheel with a bit reduced diameter, however don't know if it will be able to 3d print that small gears. If not then I will need to adjust the design of the tilt house and print them again. Think I will go fly some heli today instead.

[karla]

The new gears that fits on the servos with smaller diameter turned out to be okay for now, but not a permanent solution.
Did mount motors and all and now there is enough lift/thrust with good margin.

A had a puzzling result when trying to hover first time.
When starting to lift off it pitches backwards and will flip over backwards unless i reduce throttle.
It is unexpected since the lift is applied vertically on the wing spar by the two motors and CG is also aligned by the wing spar, so it should not flip backwards or forwards (unless applying pitch). When it starts to pitch backwards I try to compensate with pitch forward with the stick. However, it seems to respond far too little on the stick command. I use Attitude on the pitch. I know the servos are able to pitch much further since they do when using Manual rather than Attitude.

Maybe I should try use Rate and see what happens...
Or could the board not be centered horizontally...

[TheOtherCliff]

If it works OK in Manual, but has that issue in Attitude, it might be vibration.  Balance the props.

[karla]

ah will try.

[Mangee]

How about air flow over the wings. Your motors are at CG but the wings are behind and under the tips of the props.
Sort of like the E-flite Convergence.
I am building a RQ-7 Shadow for vtol but its CG is down the center of a straight wing with motors at the wing tips.
All of the swept wings doing vtol on other sites are either tries or quads. Shutting down the rear motors on FF flight.

[karla]

Thanks Mangee, Yes, can certainly be the air flow effect over the wings, that is bound to have some impact.
Yes, lots of swept wings are tri- or quads with or without a motor at rear.
Heard others say its difficult to get the frame balanced in hover like this.
However, I am trying to see if it can be done since I like the comparatively simple design if it can be set up.
Good luck with your RQ-7 Shadow build!