17-Sep-2020, 03:32 AM
OK, so lockdown ain't allowing for much full size rippage so I have been working on some micro builds. I've always liked the frames by GnarlyFPV as the canopy design into the frame is pretty unique and of a high quality. The small builds can be tricky to tune but now I'm using 4.2.x with no issues. A lot of micro builds would still favor BF 3.5.7 due to its flight performance for this size class. BF 4.0 was a nightmare to tune on micros but now it's a lot better.
Here's the end result before I get into the build... It's a sweet, tight build...
Starting the the parts list...
I wire the motor cables facing inwards and them loop them back out. I force the bend in the wire manually with pressure so the solder joints aren't pulled on when doing this. The length of the motor wires is checked beforehand. In this case the motors were coming from another micro build that had seen better days and one of the cable sets was too short. You can see the extension of wires in the pic below.
Now the next part comes together with a few other items at the same time. The filtering cap is placed on the FC board direct to the power solder pads. I've done this for two reasons. 1) I don't want the cap on the end of the xt30 connector, at such a small size of a quad I reckon that the cap on the xt30 would influence the quads flying characteristics as it is a rather large in comparison to the small quad. 2) there is talk around the net that on high-S builds for toothpick style quads the cap has a greater effect when placed directly at the power solder pads.
Fitting the FC to the frame is easy with two m2 screws and some whoop gummies. At the same time the motor wires are twisted to make them neat and take up any extra slack in the length. The battery strap is inserted too as this time as it can't be moved once the FC has been secured to the frame.
Starting to look the part....
At this point it is time to plug power in and test the motors in BF. Flash BF to 4.2.2 and flash the BL_HELI_S esc to 16.73 of the JM firmware for RPM filtering. DSHOT set to 300 and magnet pole set to 12 (smaller motors are usually 12 magnets). Tested motors for RPM errors and all good. I like to run props-out so I setup BF with prop direction reversed and review the motor direction in BLHELI configurator to ensure they are all spinning in the correct direction.
The battery cable is secured to the rear left arm and power cap. Just to make sure! There is very little clearance between the top of the battery cable and propeller.
Next is the receiver and VTX. The R-XSR has the JST connector removed for space and heatshrinked for electrical isolation. I cut out some heatshrink for the bind button. The R-XSR is from another build and missing an antenna. No biggie, this quad ain't even a park flyer so range is not really an issue. The Unify nano vtx is also heatshrinked for safety with the U.FL connector exposed to allow a connection to the vtx antenna once the canopy goes on.
In micros like these, hot glue is your friend. It provides a solid yet non-permanent fastening to the FC. It also holds things in place, raised above the electronics to help from accidental shorts. I've stopped using double sided tape in these builds. The glue also withstands bumps and crashes pretty well, keep things in place!
Here you can see the layout of the vtx and receiver. The goal is to fit them in the diamond profile of the FC. Keeping them to the centre line for canopy protection yet low enough that the camera can have a good range of angle movement. Note the location of the U.FL connector for the vtx antenna.
At this point I would connect the camera and spare vtx antenna to configure BF and test that everything is working OK. Don't forget your vtx tables!
Now onto the vtx antenna. Using a lighter to heat up the coax I can bend it to shape to a) fit the canopy profile b) have the U.FL connector rest in place as to where it will connect to the unify nano vtx. This minimizes any stresses on the cable pushing/pulling against the U.FL connection.
Here' is a pic showing the path the vtx antenna coax takes to sit where the U.FL connection is located.
Now the canopy is installed. The antenna cable is fed through the access hole in the canopy and antenna tube placed over it. I've installed both antenna tubes for looks. : CADDX Ant camera is also connected.
Comes in at a dry weight of 59grams, not too bad.
I'll post some video of ripping around the house soon!
Cheers,
ph2t.
Here's the end result before I get into the build... It's a sweet, tight build...
Starting the the parts list...
- JHEMCU F4 FC - JHEMCU SH50A F4 OSD 2-3S AIO FC - This is a new version of the old school purple whoop FC they make. Unlike the beefy whoop/toothpick FCs this one is light.
- RCINPOWER - 1204 5000kV motors
- TBS Unify32 Nano VTX
- R-XSR receiver.
- CADDX ANT FPV camera, 16:9 PAL version.
- No-name micro AXII vtx antenna
- Gnarly FPV PRIMO frame - https://gnarlyfpv.com/collections/best-s...ucts/primo
- 65mm HPPROPS t-mount
I wire the motor cables facing inwards and them loop them back out. I force the bend in the wire manually with pressure so the solder joints aren't pulled on when doing this. The length of the motor wires is checked beforehand. In this case the motors were coming from another micro build that had seen better days and one of the cable sets was too short. You can see the extension of wires in the pic below.
Now the next part comes together with a few other items at the same time. The filtering cap is placed on the FC board direct to the power solder pads. I've done this for two reasons. 1) I don't want the cap on the end of the xt30 connector, at such a small size of a quad I reckon that the cap on the xt30 would influence the quads flying characteristics as it is a rather large in comparison to the small quad. 2) there is talk around the net that on high-S builds for toothpick style quads the cap has a greater effect when placed directly at the power solder pads.
Fitting the FC to the frame is easy with two m2 screws and some whoop gummies. At the same time the motor wires are twisted to make them neat and take up any extra slack in the length. The battery strap is inserted too as this time as it can't be moved once the FC has been secured to the frame.
Starting to look the part....
At this point it is time to plug power in and test the motors in BF. Flash BF to 4.2.2 and flash the BL_HELI_S esc to 16.73 of the JM firmware for RPM filtering. DSHOT set to 300 and magnet pole set to 12 (smaller motors are usually 12 magnets). Tested motors for RPM errors and all good. I like to run props-out so I setup BF with prop direction reversed and review the motor direction in BLHELI configurator to ensure they are all spinning in the correct direction.
The battery cable is secured to the rear left arm and power cap. Just to make sure! There is very little clearance between the top of the battery cable and propeller.
Next is the receiver and VTX. The R-XSR has the JST connector removed for space and heatshrinked for electrical isolation. I cut out some heatshrink for the bind button. The R-XSR is from another build and missing an antenna. No biggie, this quad ain't even a park flyer so range is not really an issue. The Unify nano vtx is also heatshrinked for safety with the U.FL connector exposed to allow a connection to the vtx antenna once the canopy goes on.
In micros like these, hot glue is your friend. It provides a solid yet non-permanent fastening to the FC. It also holds things in place, raised above the electronics to help from accidental shorts. I've stopped using double sided tape in these builds. The glue also withstands bumps and crashes pretty well, keep things in place!
Here you can see the layout of the vtx and receiver. The goal is to fit them in the diamond profile of the FC. Keeping them to the centre line for canopy protection yet low enough that the camera can have a good range of angle movement. Note the location of the U.FL connector for the vtx antenna.
At this point I would connect the camera and spare vtx antenna to configure BF and test that everything is working OK. Don't forget your vtx tables!
Now onto the vtx antenna. Using a lighter to heat up the coax I can bend it to shape to a) fit the canopy profile b) have the U.FL connector rest in place as to where it will connect to the unify nano vtx. This minimizes any stresses on the cable pushing/pulling against the U.FL connection.
Here' is a pic showing the path the vtx antenna coax takes to sit where the U.FL connection is located.
Now the canopy is installed. The antenna cable is fed through the access hole in the canopy and antenna tube placed over it. I've installed both antenna tubes for looks. : CADDX Ant camera is also connected.
Comes in at a dry weight of 59grams, not too bad.
I'll post some video of ripping around the house soon!
Cheers,
ph2t.