Hey everyone, I wanted to start a new build thread for this four inch frame I got.  The Twig Mutant 4 from RacerXfpv/betafpv.  

I didn't purchase the BNF/PNP version that is made in conjunction with BetaFPV - where is the fun in that?    It's a cool kit, comes with all the parts and 3d printed bling.  Including one hell of a large toothpick/whoop like canopy that just has to be seen to be believed, lol..   This build started based on the selection of the FC.  I know, silly right?  I like the all-in-one whoop/toothpick style flight controllers and pushing them to their limits.  When betafpv announced a 30A version (limited run) I jumped at the chance to get one but missed out.
Then a clone manufacturer released a 30A on banggood - https://intofpv.com/t-new-jhemcu-clone-w...20-and-30a - so I purchased a 30A one and hope to have it soon.

In the meantime I received the kit.  Everyone is of good quality.  Check out that canopy!!   The batt strap is different, never had one with a rubber side to it before.



My first question to the forum is about choice of motor.  Ideally I would like to use one of the sets of spare motors I have on hand.  

I have two types of 1408 sized motors.

• EMAX RS1408 3600kV
  
• T-Motor F20II 3750KV
  

Each of these motors have different attributes.  The EMAX is a 1.5mm shaft, the T-Motor is a 5mm shaft.   The EMAX has a stiff, notchy feel and the T-Motor is very smooth.

The main pain is the limited amount of 4 inch props on the market, especially in Australia.  Maybe in the US there are more options but I'm not a fan of ordering from the US as shipping is long and expensive.   Banggood is OK but doesn't have the biggest range.

Given the shaft sizes I have this pairing of props to motors at the moment.

EMAX would be paired with the HQ 4025 props.
T-Motor would be paired with the HQ DP4 x 4.3 x 3 V1S props.



My questions for the learned members of this forum as this.

1. The "notchy" EMAX versus the "smooth" T-Motor - what should I expect from this difference in the motors' magnetic attributes?   Will it just be more low end torque on the EMAX and better high end speed/resolution from the T-Motors?
   
2. Should I try the EMAX with bi-blades and leave the t-motors for another project?  This is a freestyle quad  - not a long range or cruiser build.
   
3. Is a 1408 motor an appropriate size for this frame?
   
4. I have some 4S BONKA 460mAh packs I plan to use for testing, I take it I'll get some low flight times with this capacity battery?
   
5. I have a single 4S BONKA 850mAh pack, I think this will be the sweet spot on weight versus discharge performance versus capacity - anyone else had this experience in this class of quad?
   
6. Where can I source more options for 4" props?   The EMAX motors with their 1.5mm shaft makes for limited options.  I will take a US based store suggestion given the brim pickings for props in this class.
   

I'm excited for this build and have some other parts still on order - especially the 30A AIO FC - bloody bangood shipping is taking ages at the moment...

Will update this post with other parts shortly...

cheers,
ph2t.

Not too experienced with my own 4inch build yet, looks like yours is going to be a tad more lightweight but here is my take on your questions.

1-3. I think 1408 is a decent size, but I'm guessing 1404 would be more effecient for your build especially with the low pitch props. Your prop selection is limited and is going to depend on the motor you choose. I would go with the emax ones, run the latest gemfan props http://www.gemfanhobby.com/list.aspx?cid they just came out with a bi and tri blade for toothpick style builds (try both?).

4-5. 460 seems a but low and the flight characteristics are going to change when you switch to 850. 650 would also work pretty well with slighty lower flight times and maybe a bit more voltage sag on punchouts. I'd test with your single 850 pack. Btw I switched from xt30 to xt60 on my build and it made a pretty big difference but again I'm running a heavier build.

6. Not familiar with the us market. The 4025 hq you have seem really nice and so do the gemfan props I mentioned. Can't really help you there. Getfpv has a pretty big selection of 4inch props but most are pretty old and are made for 5mm shafts. They do carry the hq bi 4025 though. Rdq and pyrodrone also carry some.

I think you are going to have an amazing build on your hands either way you go. Feel you on the banggood shipping atm. I'm also waiting on stuff that's been delayed forever now ?

Hope this helps a bit.

Notchier motors may make it harder to tune out jello, if that matters. I think I'd go with the T-motors if the weight penalty is not too severe...

Thanks for the information guys, appreciated!

Flickery, I didn't know that 5mm on these size motors was considered old.  Good to know that the 1.5mm shaft is newer and hopefully will have more prop options in the future.  I will order some of those new gemfan ones, thanks!   The 850mAh bonka pack comes with an xt60 but I was thinking of going the other way and converting it to xt30.  I will run it with xt60 for now given what you've said about performance.  The thought of an xt60 plug connected with a massive gauge cable to a "toothpick" AIO FC is something I'm yet to get my head around, lol...

Sloscotty, that's interesting to know.  I feel like the t-motors would have a smoother response over the full range of throttle but they would be paired with the 3 blade props, maybe that counteracts them a bit in ability to change speed quickly?

thanks guys,

ph2t.

I want to run some bling leds and got these Zeez design race leds, rgb etc..

https://www.zeezdesign.com/rgb-led-strip/

I was thinking of running the motor wires under the arm and having the leds on each arm.



I have four of these led strips.   Can I just wire up the led signal wires of each of these led strips in parallel to the led signal pad on the FC?  I know then they won't be discretely addressable and will all show the same programmed response.

cheers,

ph2t.

(10-Apr-2020, 03:49 PM)ph2t Wrote: Thanks for the information guys, appreciated!

Flickery, I didn't know that 5mm on these size motors was considered old.  Good to know that the 1.5mm shaft is newer and hopefully will have more prop options in the future.  I will order some of those new gemfan ones, thanks!   The 850mAh bonka pack comes with an xt60 but I was thinking of going the other way and converting it to xt30.  I will run it with xt60 for now given what you've said about performance.  The thought of an xt60 plug connected with a massive gauge cable to a "toothpick" AIO FC is something I'm yet to get my head around, lol...

Sloscotty, that's interesting to know.  I feel like the t-motors would have a smoother response over the full range of throttle but they would be paired with the 3 blade props, maybe that counteracts them a bit in ability to change speed quickly?

thanks guys,

ph2t.

The 5mm shaft design isn't bad or old. I meant most of the props are all old designs, there are also new 5mm hole 4 inch props coming out though. Either way for now the 4inch prop selection is not the best but getting better fortunately.

Can't help you on the led strip, never really used leds. Always kind of wanted to though haha.

i ordered some emax rs1306b 4000kv to use with 4inch. i will try to stay under 100g.

regardless of the characteristics of the motor, i beleive the more lightweight eamx will fit bettter to the settup.

i beleive battery choice will be about avarage flyspeed, as 3600kv+ can be very fast, you will need 850mah for the f20 for sure on highspeed. on less speed, the 650mah will give the most crazy accrelation.
my choice with the emax 1306 will be less than 650mah 4s for bashing and freestyle, 850mah for gates and flags, pretty sure the more weight will give a better controllability.

i used the h4025 with 2s and 3s its a fantastic prop, pretty nervous how it will handle more rpm.
i would like a triblade version... i will try the gemfan triblade.
even for the 5mm shaft, there are more props, but there is only the one and only realy nice hq4043... both mount options need better market support.
gemfan s version which should fit both mounts will be nice, if it truly work.

are you going for bf4,1? i would be intressted in your tune impressions and results.
i plan to go for bf3.5 but would be nice to get impressions..

i like your settup alot, anyway the motorchoice, thanks for share your progress

did you saw the betafpv 35a 6s aio which should come? even more than 30a
the emax 1408 as 6s with 4inch is a future -project direction for me :-)

Thanks for the clarification Flickery, I understand what you're saying about the props now.  In the end I decided on the emax because I want to try bi-blades.  I weighed the t-motor versus the emax and they're exactly the same.

Hugnosed, thanks for the suggestions with the HQ props, I'll definitely check them out.  I will let you know how I go with the tune on BF.  I will use the latest BF 4.1.2 (I think) and see how it goes.  I'll prolly start of with PID profiles just scaled up/down via the slider tabs.  PId profile 1 = 1.0, PID profile 2 = 0.9, PId profile 3 = 0.8. I find that an easy and quick way to get a ballpark tune.  Especially on these smaller quads, but hey, 4 inch ain't that small either!

6s on a four inch? lol.. that's crazy hugnosed!

So tonight I did some more work on how I was going to mount the leds onto the arms.  I thought at first of wiring the wire underneath but that would be too messy routing the cables and I thought in the end on using heatshrink to build up the cable set.

What I mean is that I started the with the motor (shown below) and first fixed up the cables, I had to solder some cable extensions on as these motors came from a previous build.  That's one layer of red heatshrink you don't see in the photo below.  


Next I placed some white heatshrink over the three motor cables, keeping them under a light tension whilst doing this so they would stay flat, three wide.



The Zeus led strip is pretty small and has 10 addressable leds.  I then fed on some clear heatshrink and place the led strip within it.  Placing everything in position I then shrunk the heatshrink and now the led strip is held in place on the motor cable with all wires nice and flat in a ribbon like format.

It's hard to see the clear heatshink in the picture below.



I rigged the led strip up to a spare mamba FC to test it.   Configured the led strip feature in betaflight and put some test colours on to check everything.   Works a treat!



Now I have to confirm if I can run the four led strips in parallel as they sink a bit of current.   On the highest current draining colour of white they sink 0.6A.  Four of them would push the BEC to 2.4A in drain.  I might have to think about this before soldering all four onto the FC.  I will have to check the FC specs to see if it can handle this much current.

Looks really pretty though..

cheers,

ph2t.

same weight at least some grams from the lighter props

i got a few bad experiences with micros and bf4.1, i probably doesnt spend enough time to eperiment and tune... but i get an acceptable tune in a few minutes on bf3.5.
i saw the tuning suggestion for the mutant 4inch https://racerxfpv.com/mutant-4-tuning what gave me another reason to try 3.5 on my „near build“
i would like to get your impressions on 4.1, but probably you should try their tune suggestion aswell

4inch 6s „its insane“ :-D

but its 4s kv.. not usable for longterm exactly this way.


one rare 4inch video shows insane performence on the emax rs1408 3600kv aswell;

I'd come here to ask what your pids are looking like since I'm having the darndest time tuning my 4 inch biblade and came across this ...

(10-Apr-2020, 11:35 AM)sloscotty Wrote: Notchier motors may make it harder to tune out jello, if that matters. I think I'd go with the T-motors if the weight penalty is not too severe...

... I'm using Xing 1403's and they are extremely notchy. If i just nudge a prop, it can actually skip a notch lol. I've owned Xing 1408's as well and they were very notchy.

Anyway, I'd be curious to check out your PIDs as I just can't seem to dial mine in.

If you haven't yet tried 48kHz PWM on your ESCs, it might be worth it to help with vibrations (jello).
https://oscarliang.com/best-blheli-32-se...-frequency
(Since you've messed with your PIDs a lot, you may have to retune.)

I will provide information on my tune once I get to that point guys.  I'm sorry but that's a while away yet...  Still waiting on the FC for this build to arrive.

BF4.1 is harder to tune a bit in smaller sized quads, but it has settled down since 4.0 flyaways and stuff.  RPM filtering helps heaps with the little guys

I've got all the led/motor harnesses done and installed.  turns out you can just parallel these leds off the same signal wire on the FC, no problems.

With a few different colour leds on the whole setup is drawing 645mA.  So if the FC has a 1.5A BEC everything should be fine.  Gotta allow several hundered milliamps for VTX and cam.  The RX doesn't need as much.



It's going to be fun programming these leds



Cool...

I UOK it's really coming together now.   I finally got the new 30A AIO FC and it's sweet as.

Motors wires mounted underneath, folding over to feed out to the arms on the quad.   The motor’s solder pads were tricky as all buggery. Tiny as with little room for error. 



Started organising the LED cable loom for combining all four RGB led strips.   Who thinks it’s OK to make all three cables the same colour? That was a pain to tag all the wires, lol


RGB LED loom all organised, combined into one set of cables. 


First mounting of it all together.  I went to town on measure twice, cut once with this build and I feel it is paying off.



The RBG LEDs are all functioning well.



I will cut and refit the LED cables as they are a little long, was part of the first test of it all together.


Cheers,

ph2t.

more progress     

I have now installed the XT60 plug, power cables and 1000uF cap.  I have also installed a crossfire nano RX with the mini immo-T antenna.  The RX is sitting on top of the FC.
The mini immo-T antenna is on the front brace.  I'm not 100% sure on this placement - I'm not expecting crazy distance out of this antenna but it should be fine for freestyle distances of a few hundred meters, testing will tell.  Looks cool where it is placed though.





This FC comes with a current sensor but there is no doco on what the mA/V values are.  I have to tune this setting so I can accurately report on current consumption on the OSD.

I use this method to calibrate an FC's current sensor.

1. Connect a multimeter in-line (series) between the battery and quad.
   
2. Set multimeter to current measurement (10A scale)
   
3. Connect power to quad
   
4. Connect FC to betaflight
   
5. Spin all motors up and aim for 1A on the meter, note the current value BF reports.
   
6. adjust current gain value in BF
   
7. repeat steps 5&6 until the value is a close as possible between BF and the multimeter
   
8. use offset value to get idle current draw correct
   
9. spin all motors up to 2A on the meter, confirm accuracy of BF value
   
10. repeat steps 6 and 9 till ok
    
11. spin all motors up to 3A on the meter, confirm accuracy of BF value
    

See the pic below for the rig I make up.   You can see when not armed and all red-LEDs the quad draws 244mA.



Finishing up the electronics with a TBS unify nano video TX, I got the TBS whoop mount adaptor to mount it in the same format as the FC board.
A Caddx Baby Ratel is getting installed as well.




Here's the finished build, quite happy with how it turned out and can't wait to rip up a few dark parking lots for some LED action.





After this last photo I took the props off.  I'm not going to make the mistake of a late night, tired test hover and puncture the plaster roof again.   I will configure the quad tomorrow, setup the finer things and get some starting PID tunes in place.   Still a bit to do.

146grams without battery.


cheers,

ph2t.

Super nice looking build, well done! Enjoying ripping up the skies.