As I get more time on the Align BlackShark there’s more tweaking and adjustment going on. Here is the latest round of modifications I’ve made to my machine to suit my tastes, and the reasoning behind them..
1) Gear Ratio
Out the box the Trex 700F3C runs a 9.33:1 gear ratio with the 470KV motor. This setup leaves very little headroom at the top end for the ESC governor to work with anything but perfect fresh batteries. This is with a Max head speed of only 1950rpm programmed into the ESC too. There are a number of options available to sort this, a change of motor or a gear ratio change. With the latter being the more cost effective that is what I went for. I changed to a 110T main gear and a 13T pinion to give myself a ratio of 8.46:1. With this ratio the ESC is happy from my hover head speed of 1570rpm right through to an aero head speed of 2050rpm with room to spare for the governor to work at its best.
2) Tail Gear Ratio
Again as standard the tail ratio is a little on the low side, just like the main gear ratio. At 1:4.33 I wanted to increase this to something in the higher 4′s. Swapping out the tail counter gear assembly and main tail drive gear allows a number of options. I went for the 21 tooth counter gear arrangement which gives me a new ratio of 1:4.95. The other option is to go for 22 tooth and have 1:4.72.
3) Flybar Ratio
Yet again, another ratio..and too low. In my previous post I talked about swapping out the ball on the swashplate side of the mixer arm to increase the ratio. With some newer more accurate measuring instruments I’ve got an accurate reading of 25 degrees of flybar tilt to 15.5 degrees of blade tilt. This gives a ratio of 0.62:1, better than standard but still far below what I would like. Fitting a set of Trex600 Pro mixer arms with a combination of Linkage Ball B and Linkage Ball A (Complete set: HN7065). I also used Linkage Ball B in the flybar carrier (in fact this is where I got my Linkage Ball A from!), however you will need to file down the threads slightly to stop them interfering with the flybar. Using this arrangement gave me no change in overall pitch range but resulted in 19 degrees of blade movement for 25 degrees of flybar movement giving me a much better ratio of 0.76:1. I did need to add a small washer (tail rotor blade spacer) behind the mixer arm to stop the ball links from fouling on the mixer arm itself. Also this arrangement needs your servo throws set perfectly as it is on the mechanical limit of what can be achieved on the rotor head and it’s easy to get binding if things aren’t perfect.