fabien
 lvl.2
France
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Hi,
this is a small build log with tips for S900 when dedicated to intensive use. I hope it can be useful to anyone.
The first step will be to protect the retract servos cables with black nylon braid. Reason is, the multirotors used for intensive work are often left directly in the sunlight and UV's will, with time, damage the housing of the wires. It will also ensure a small protection against vibrations and eventual rubbing against mechanical components. For all servo wires, 6mm braid will do the trick. You will need to fit some heatschrink on both ends of the nylon braid, and secure it with a drop of epoxy ( or CA eventualy) so the heatschrink does not slip away from the nylon braid.
Heat up the heatschrink on the servos outputs once the cables are connected, so the heat will also bend the heatschrink so it can follow the curve / bending in a decent way.
Once done, it's time to move to other connectors like the ESC connectors which run from the MCU to the Frames. Use 9mm braid on this one and make sure to keep the braid a bit short so cable will not be too rigid after for the final connexion. Here, i used a to long braid, i changed it to shorter so the cable does not create too much rigidity. You cna see in later pictures how it looks like with the correct lenght of braid applied. I sued the S1000 nice heatschrink that is provided for the coaxial power connectors.
Important thing is, the A2 MCU has small edges to allow right side insertion of the connectors for Futaba connectors / standard ESc connectors. These edges are also present deeper in the A2, and it is not rare that some people do not press further enough the connectors. Make sure they are totally and firmly pressed ! Once done, secure the whole thing with " Plastidip" or rubber compound : it will be easier to remove it in case of need, but it will offer a great protection against vibrations and accidental unplugging during flight.....
Add a bit of 3mm braid on the antennas if you are using the intergrated receiver. Here, it is important to leave 3 mm or so between the heatschrinks and the MCU base so there no tension creatd by the braid extension. This could result in early breaking of the antenna wires ( baaad...  ).
Let's move to the power connectors of ESC's. The cables are just crimped in the gold plated connectors. For intensive use and traveling, this wil result in often "pulling" on the cables when unfolding arms. As the connectors are not visible when the plastic cover is installed, it will nto allow to see if a wire is slipping out of the connector. I decided to secure the crimping with soldering (removing the heatschrink around the crimped connector and soldering). As i had aready installed the arms ( no picture needed i guess..) i made it on the fly. If you do so, make sure to protect the frames with some tissues or carton or anything, and then cleanup the solderings with Flux cleaner.
As this machine is built to perform aerial view in wet environment, i also decided, but it's optional, to apply soldering once the connetors are installed and tightened. Pro is that there will not be any bad contact risk, cons is that for maintenance, you will need an iron solder
After that, Plastidip (the black complound you ca see) is applied to protect the connections against oxyation and humidity.
Time now for installing the cover and process electronics installation.
There are many ways to install the electronics on the S900, here is mine, like tastes and colours, everybody has his favourite so let's say it suits me as it is. IOSD Mark II will be installed and will need to be connected also to the Zenmuse Z15 GH4. There will not be any datalink so only 2 canbus ports are needed on the IOSD Mark II on this build. A " blank" mount testing is always a good thing as sometimes little suprises can occure when you make your final connections. For example i had to relocate slightly the IOSD Mark II to allow the video input connector to run without binding on the XT60 plugs..
I choosed to route the IMU cable with small adhesive tabs in a round pattern so it does not "fly" anywhere in the build.
When you perform your installation, make sure that you do not over twist or pull power cable of PMU or X1 cable, same for the IMU Extra CAN connector. They are fragile connections inside the casings and if you give one turn too much, you just wrapp of the thin wires inside or break the PMU power pads.. I will not make a drawing of what can happen in that case... Worse, if you damage the PMU Canbus cable it will make the LED canbus connector worthless and you will encounter severe troubles when plugging the USD cable or using the bluetooth with abnormal behaviour in the software ( for example crazy numbers and so on). All these devices are delicat and wires must be routed with clean installation and no over constraining... Twisting hard these CAN bus or PMU power or X1 cable will lead in later crash for sure... This is also valid for GPS / compass and other connectors.
Now that all wiring seems to have decent locations, it's possible to move to the next step... Flipping the machine upside down will allow to install the landing gears. Make sure to use thread lock on all screws, and check for threadlock on servo aluminum horn system also. Distance between the rubbers of the legs and the central alu T mount is approx 18,5 cm or so to get it centered from memory. Once all is secured, you can add a small drop of CA on the aluminum tube mounts with a sharp knife edge so it will run by capilarity between the aluminum support and the boom and will bring a small extra safety just in case.. Make sure to degrease the aluminum parts and the carbon tubes before proceding, idealy just give a very light sanding with 240 grade sandpaper ( gluing will be much better) in both alu parts and carbon booms where they match together...
Time comes for the Zenmuse to be installed. I use 9mm nylon braid and also 6mm. If you sue some, make SURE that you leave some uncovered wiring especially for the connectors going on the GCU of the gimbal, so they can be twisted and bent for their insallation without pulling on the connectors hardly. I also remove 3 screws from the GCU to install it on thee support ,as there are 3 holes that match the screws holes. I then apply thread lock and fit the GCU in place by using the screws trhough the alu support.
Then, install the gimbal, plug the wires ( you can protect some canbus wires with nylon bread, optional...) , plug the X1 connector from the PMU and check all connections + correct sequence between CAN 1 and CAN 2 ( or the IOSD or the Zenmuse will not work correctly..).
Next is the video transmitter AVL58 to be wired. Being a bit maniac i wanted a nice routing. Easy to achieve with a bit of heatschrink and patience. Heatschrink is anyway recommended if you run the flat wire from IOD to video TX through the frame holes so it does not get damaged by fiberglass edges.
For the compass, the mast and adapter shall be installed using slow cure epoxy, not CA ( Ca will not resist and will elad to GPS / compass unespected rotation in the best case, falling in the worst one..
Also, slow cure epoxy will allow you to place the mast and the GPS top support perfectly aligned by using simply adhesive tape exactly like if you were adjusting a boat mast by applying tension with tape to the frames on 3 or 4 spots.
A bit of finishing for the other cabls ( video and accessories and you are all done ).
Make sure to use thread lock on the top carbon plate ( the one with the GPS / Compass). Also, it might be better to flip the GPS foldable support 180° so that when you fold the GPS shaft, it will fold forward and will avoid the cable output to face up ( can be damaged by pressure in the transporting case).
Hope this little build log helps ..
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