VTail frame

[barneyg]

I';ve been hankering after a Hunter V-Tail or the Armattan V-Tails for some time but I also felt like building something from scratch so I';ve been plotting and planning for a while and my first prototype is finally complete

[attach=1]

Center plates and motor mounts are 3d printed ( the motor mounts are modified versions of the ones from the SS Teslaquad - Thanks Chris ), arms are 10mm pultruded carbon fibre square tube from Hobbyking and the whole thing is held together with 3mm nylon bolts.

Something that I';ve found though is that the nylon bolts I';ve got are slightly less than 3mm so while when I put it together with stainless screws the square tube is held tightly with no movement possible there is some slack with the nylon bolts and the arms can rotate a bit.  Everything is fairly solid once tightend up though.

The holes for the FC are at 30.5 so perfect for the Naze32';s    All comes in at 156 grams so over 130 grams lighter than the listed weight of my RCTimer 450 clone and should still just accommodate 10 inch props.

Bah just realised I';ve got those rear motor mounts on upside down 

[Hands0n]

Thats looking really good Barney 

[kilby]

Oh dear now you have gone and done it.

Have been trying to decide what to do after my short lived Teslaquad, whether to go for a H quad or a VTail as my 450 is a bit lardy and breakable for how I want to try to fly.

[guest325]

Bah just realised I';ve got those rear motor mounts on upside down 

Not really, both ways works OK, I did a lot of research before I built my prototype and found that there was no real disadvantage in having them that way up. The only thing different you have done to most I have seen is to have the air column pointing outwards and not inwards; I would have thought it doesn';t matter but.
With the air column pointing inwards it is easier to run bigger props on the rear - mine had the same size as on the front!

[barneyg]

Yeah, exactly, the way round they are in the picture limits the rear prop size quite a lot.

[barneyg]

Flipped the rear mounts.

Received the D4R-ii RX module in the post yesterday, bound it to my TX, updated the firmware to the 27ms CPPM version and configured my mixes to work with the Naze32 that is destined for this quad.

Up to 422g on the scales with Naze32+case, uBEC, and RX.

After some chatting with DarrelW yesterday in the shoutbox I';m going to order some SunnySky X2212 1400kv motors to drive this thing.

Now to select the ESC';s.

[Hands0n]

Afro 12A ESCs sir?

[barneyg]

Afro 12A ESCs sir?

Not with those motors  ... max draw is 23A ... I was thinking of going for the Afro 20A Slim';s which have the same nfets as the 30A ones but a different layout and thinner wires.   Obviously I';d replace the wires with the appropriate thickness ones.  With them being about 12 mm wide they will fit fairly well on the arms rather than having to be on the body where there is precious little space.

[guest325]

It will go like a bl@@dy rocket with that setup, hope you';ve got fast reactions ::)
Matt Hall off Simple  copter uses those motors a lot and well....you';ve just got to see him fly ::)

[barneyg]

Well motors arrived ... not even ordered the ESC';s yet.

did a quick dry fit and its almost ok ... BUT my OCD is kicking in ... I got 1 design from Chris for the motor mounts and I modelled mine off this.  Of course I printed 4 of them but they all have the same motor screw hole pattern so for 2 of the motors the wires are almost perfectly placed but for the other 2 they are about 180 degrees out.  Now obviously I could just turn the plates upside down but then the rougher "top" of the print will be facing out on those 2.  Time to do some model editing - and while I';m doing that I';ll just rotate them a little bit so the wire placement is even better 

[Hands0n]

I would suggest brushing the rough side with some Acetone ... but when OCD strikes ... well .. i know that simply won';t do 

[teslahed]

Of course I printed 4 of them but they all have the same motor screw hole pattern so for 2 of the motors the wires are almost perfectly placed but for the other 2 they are about 180 degrees out.

Most simple CAD packages have a mirror flip button. Use that on half your motor mounts and they should all line up properly.

[barneyg]

Most simple CAD packages have a mirror flip button. Use that on half your motor mounts and they should all line up properly.

Yep that was my plan.

[barneyg]

Still waiting on the ESC';s but I';ve fitted the motors, some 9 inch props and made some landing gear.

[attach=1]

[Hands0n]

Liking the look of that ... quite menacing 

[barneyg]

Yay ... got my Afro 20A Slims in the mail yesterday.  Now to strip them down and attach thicker wires to make them 30A capable :)  These things are sooo tiny but much longer than I expected ... the arms are only just long enough to fit them ... The way the Cap is fitted it protrudes on both side of the board so it isn';t going to sit flush ... I may have to see if I can modify their placement as well as putting on the thicker wires.

[nub]

i take it they'; are actually 30A ESC';s but labelled as 20A then or something?

[barneyg]

yeah ... they use the same N-FET';s as the 30A ones but in a narrow but long PCB and they use 20AWG wires (which are sooooo skinny)

[nub]

ah right that';s pretty cool, think i have seen them before but never knew that.

[barneyg]

Of course there is a risk that some other part is not up to carrying 30 amps ... but these motors "should" only pull 23 A ...hopefully I';ll be OK

[barneyg]

... and rewired with 16 AWG for the power lines and 18 AWG for the motors ( this is the same gauge as the wire on the motors even though technically it is only supposed to be good for 22 Amps )

Found a really good way of melting lead free solder that my Maplin 60w iron was having trouble melting.  Add some 60/40 solder to the tip of the iron and the lead free stuff will melt in seconds :)

[barneyg]

Almost there.

Refined the frame and reprinted the motor and main plates.
fitted the ESC';s and FC.
Got 2 motors fitted and confirmed motor mix, correct motor channel and rotation.
Fitted a 3rd motor .....
...
...
...
"Honey time for bed"

[barneyg]

Got it all wired up and tested ... prop rotation sorted and took it out for a test flight.

Its at this point I';d failed to notice that the last firmware update I did had reset the MinThrottle on my Naze32 to 1150 rather than the 1064 it was set to previously, even though it hadn';t reset some of the other parameters (or perhaps I';d just reconfigured the other ones and forgot to do the MinThrottle).

What I discovered at the point I armed the motors was that with a quad that has an AUW of 615g at this MinThrottle, 9 inch props on 1400kv motors it only just stays on the floor.  So a tiny touch of throttle and she went skywards with lots of wobbling, cutting the throttle to minimum at this point didn';t really help just reduced it to a really unstable hover at head height.  So I cut the motors completely and crash ... the 2 front legs are toast and one of the little lugs I';d put on the top plate to locate the front arms got sheered off.

So I';ve modified the designs for the front legs and the top plate lugs to try and make it a little stronger.  The legs are reprinted, will do the top plate tomorrow, I';ve ordered some 8 inch props (Had to get the 3d ones as he was out of one rotation for the regular ones) and a BT module from Phil so it isn';t quite so powerful and so I can configure the PIDs without connecting to the laptop all the time.

[barneyg]

this is not going well

9inch props and I can';t get it to stay on the ground ... 8 inch props and it needs 75% throttle to take off ... yaw is awful - caused a crash and finally it has started dipping an arm and that arm started flashing red and green lights at me and beeping
but the awful Yaw caused it to crash and break off its legs again but it was after that that the dipping started which could have been the cause of the crash.

Interestingly the arm that is dipping is the arm that took the brunt of the impact last time and the capacitor had been a bit bent - I wonder if there was some more serious damage to it ?

I guess I';m just not a good designer of quads

[kilby]

I would assume that vtails are more evil than regular quads to get operational.

Maybe building it as an regular X and getting it flying then after getting things like props sorted it should be converted to its final configuration.

You can guess that I want a VTail can';t you

I';ve been trying to would out how to build a pvc pipe vtail (want the raised rear props not the simple copter style)

[barneyg]

The theory is sound ... it lifts relatively evenly (not tail or nose first) when it did go up tonight, and it certainly went ok the other night on 9 inch props.

I wonder if the lack of thrust on the 8';s was because there are the HQ 3d ones as Phil had sold out of one direction of the regular 8';s.

I';m going to go back to the 9';s but with the reduced Min Throttle and PID';s which I can now tune easily with my phone thanks to a BT module from Phil.  But I think I';m going to either need a new ESC or see if I can';t find the fault with this front left one ... it runs fine for about 10-15 seconds and then the arm that it is on just dips and the thing just crashes to the floor. On writing this I wonder if the damage was done on the maiden crash then I suppose it is possible that there has been something off about it all night and the lack of thrust is due to the FC reducing power on the other 3 motors to compensate ?

I';m thinking of getting 4 of the esc32 clones now.  I thought the Afro 20A slim format would be better because the width of them is only a little bit more than the 10mm square tube of the arms but the increased length meant they only just fitted on the arms as I';d designed them ... I guess I could cut some longer arms to make them fit better.

[kilby]

Well its more than possible that a duff esc can cause havoc with a quads behaviour

[Ground Engineer]

... and rewired with 16 AWG for the power lines and 18 AWG for the motors ( this is the same gauge as the wire on the motors even though technically it is only supposed to be good for 22 Amps )

Found a really good way of melting lead free solder that my Maplin 60w iron was having trouble melting.  Add some 60/40 solder to the tip of the iron and the lead free stuff will melt in seconds :)

Ive noticed this phenomenon before and a couple of other member s have mentioned it, but Im interested in why it works. Is it a chemical reaction, or are you just creating a larger surface area with the solder on the tip.  I would be interested to find out.

[barneyg]

ok getting better ...
Replaced the cap on the dodgy esc and no cutting out so far ... put the 9 inch props back on and again back to seriously powerful.
Still can';t get the PID';s right but I did remember that initial PID tuning needs to be in Acro mode NOT angle.  Made some progress but ran out of time and broke yet another leg ... version 3 doesn';t cut it not sure how to make it stronger without making it thicker which means these esc';s wont fit without longer arms ... hmmm

[Ground Engineer]

I wonder how the Vtail would fly with the motors angle 15 degree foward