GEPRC Mk4 Frame for a 6" build

[Bad Raven]

After reading a few favourable comments with regard to the GEPRC Mk4 as a PNP, I decided to buy a 6" frame (its available in 5,6,and 7") as I had bits kicking around new unused I could hang on it.

It arrived Tuesday, and I built it today and it flew hover trial in the garden a few mins ago.

People around here a long time will know I'm not easily impressed, but this frame is clearly the work (and should be pride) of a really competent engineer or two. The finish and fit is excellent, with many touches of quality of fit and finish.

It's actually 163mm fore/aft and 260mm diagonal

It just went together, no hassle, no "fitting", no cheesium screws, most flush fitting.

As an example of the fit, the quite complex cross braced cut outs in the frame top are perfectly mirrored in the punched out cutouts in the flexible battery grip plate.   

I hesitate to say any more praise as I want another and don't want them sold out!!!!

I used:-

Matek F405 Std
Matek VTX Hub
FrSky R-XSR
RunCam Nano 2  (Yes I know its a small format, but its what I had to hand and its supplied anti-vibration cage took it up in size to a fit in the supplied mount/protection)
HAKRC 35A ESC BlHeli32 DSHOT 1200
So far its on DalProp 6" twins but it'll likely go to 6" "Folds".

The motors came off my now elderly design EMax 250 frame (which cost me £12!!), and are 3B-Racing 2206 2500kV. They were a poor choice to put on that heavy (but very strong) frame, phenomenal power, revs and torque, but 3 mins max hurtling that weight around wasn't good! We'll see how they do on the much lighter new frame assembly.

Photos if it survives its maiden, hopefully tomorrow.

I have put cheapie RaceStar motors on the Emax 250, can't have it idle!!!

[ched]

I have a GEPRC GEP-PX2.5 2.5" frame and it is very nicely made but I destroyed the motors and esc by using wrong bolts!!! Stupid me, I should have checked every one not just 1 before bolting them in. So the frame is just waiting for new bits :-)

Looking forward to picys and maiden vid

[Bad Raven]

SO, its 6" props as against 5", and 200g lighter.

Will it go?    

[badger1]

look forward to seeing some pictures - GRPRC seem to make some nice stuff

[Bad Raven]

OK, video of maiden flight first, will try to take some close up static shots tomorrow.

Usual DVR loss of quality and no doubt YouTube will do its bit to de-res it

This is end to end the maiden, other than prior 30 seconds LOS to prove it flew.

Remember, its only on two blade 6040's till I get some 6" folds.

ANDDDDDDD prior to this video, when I looked at LOS shot video the camera had stopped working, initially with no OSD either, then with OSD but black screen. I had used the lead and socket that came attached to camera as I'm likely to change it, no sense in wasting a Nano where a Std would fit, but it was only a poor plug/socket connection and after a few plug in and outs it worked OK rest of day.

No RSSI yet, that is to do, as is the power config accuracy, as though I did it, it isn't right.

Anyway, the video was shot straight after that brief LOS and camera fix, nothing really film worthy, just bedding in the feel.

Its on bog std Rates and PIDS.   

I must have been enjoying it quite a bit as I only flew that quad today, and have just recharged 11 of 1500mAh 4S ready for tomorrow. I stopped with only two more left unused!

[Bad Raven]

TOOOOOOOOOOOOOOO  Hot...............     

So, yesterday I had the case that one LED in the strip of eight would not set the chosen colour.

Also the centre pair I use for armed/disarmed indication, Green being safe disarmed, strip colour (usually now Orange) for armed.  This was set in Betaflight, and the pair were Green, but would not change to Orange though arming worked and the quad flew.

OK, you have ten seconds from now to work out why.................. VVV














The Matek F405 shares the LED strip with the Barometer, so the one not being used needs disabling, and though I thought I'd done that for the Barometer in Configuration, it hadn't "taken".  Done, and works...............   

[badger1]

if you leave them both enabled do the LED colours change with altitude?   

[Bad Raven]

if you leave them both enabled do the LED colours change with altitude?   

Well, they get dimmer and dimmer........................     

[Bad Raven]

SO, back to the absence of RSSI in OSD.


RSSI on Tx OK. RSSI set to a channel and set up correctly as regards weight and offset.
RSSI variation showing on chosen channel in Betaflight, Receiver. Gets less with distance so working.
Analog RSSI NOT set in Betaflight, Configuration. (common trap, that one)
OSD set to display RSSI

And yet, no RSSI display, frozen at 0. Repeat bootings, no change.

I went through this several times, coming right out to powered down, ensured saving of each setting.

STILL no RSSI display, frozen at 0.

Decided to give up this morning, so put props back on, switched on to give it a quick hover flight check.............

AND RSSI IS WORKING.......................               

[Bad Raven]

Its still far TOOOOOOOOOO hot...............

THREE WHEELS ON MY WAGON............

Second flight today, only flying steady CCTs to show a new member, avoiding him puking. The flight video below shows to just after ground impact, and at the end an extra clip of the last few seconds slowed down to less than 25% speed.

The battery disconnected on ground impact so nothing after first impact, and the video came back online immediately I plugged the battery back in at the scene, not shown here.

On the slomo clip you'll see when I decided it wasn't coming back under control and disarmed to save the motors and ESCs by not hitting ground under power and air mode rotation. Now watch at normal speed.................    72 year old reactions not too bad then !

One prop doing a happy jig, so benched it and went on the Hawk.

Back home, I connected it to BLHeli32 and it instantly found all four ESC and reported them correctly and talking to FC board OK.   Ergo, must either be motor or connections from ESC.
 
Found motor feed wire to internal lacquer insulated motor end iffy joint. Possible it was me when test tugging for dry joints at the other end of it since to keep motor interference down I made the motor to ESC wires as short as practical with a little spare, or maybe just chance. 
 
Anyway, joint resoldered and repaired, no cost, and test hovered in back garden. Good strong frame, Eh?
 
Ready for more "cooking" tomorrow.

BTW, on the previous flight I'd managed to get 7 Mins 43 seconds from a 1500mAh inc some rolls and flips which I was very pleased with.

[ched]

That's good reactions for anyone!!!!

[Bad Raven]

Update:

Firstly, no  repeat of the death spiral, so pretty certain the wire came off the ESC to cause the spin rather than came off during.

Secondly, the DAL FOLD 6" Tri blades arrived yesterday and were fitted to replace the DAL 6" Bi's.

AND...........  I'm not sure! 

They are smoother, quieter, yet "scream" when pumped like they are under pitched, whereas the old design Bi's had a lower pitch growl, almost resonance.

This is reinforced by the current drain being significantly less for the Folds.

Too many fixed wingers up there today (making the most after the bad weather for the last near week) to allow me to experiment, and the flat grey featureless lighting didn't help FPV anyway.

It was pretty clear cut cut on both my 5"ers which were on DAL Tri's or EMax Tri's, the Folds were better, period.

The 6", less certain but I think better.

The other 6" (EMax 250) is part stripped awaiting some HAKRC 35A DShot1200 ESCs to really stretch the new motors. (or is that stress not stretch?) The quite old EMax 30A SimonK that were on it really didn't like the new motors and anyway were max 3S (Spit!!)

They are coming on one week supply from Banggood CZ. I have used that warehouse a couple of times before and its been fine (famous last words!).

[Bad Raven]

And here we are a year on. It's still in one piece, still used several times each week.

It really is an excellent frame, and I'm looking to make another one using DJI shortly.