Originally Posted by pivlrs
Done. I pulled out the coiled spring that was supplied with the kit, and installed a simple torsion spring into the hinge. I used 0.015 music wire with a low-torque bend in it (it only required about 30 degrees of twist to install). The result is a nice smooth spring action with a very light restoring force - even the CS101 servos should be able to handle it.
As a plus, I looked at the carcass of the coiled spring I yanked out lying next to a couple test versions of the torsion spring - I think the torsion spring has about 80% less metal = lighter tail.
The whole thing looks a lot cleaner now, too. And we all know it's all about appearances...
I would heartily recommend that anybody building a B900 consider replacing the coiled spring with a torsion setup. Lighter, smoother, cleaner.
Since I have to replace some of the elevator pull line, I am also pre-stretching some spiderwire by hanging a 3lb weight on it. Should be able to bypass the stretching I saw last time (
Progress update: I finished hooking up the revised elevator last night (yeah, I know, but I've been busy
) The lighter and smoother action of the torsion spring seems to help with the double neutral problem. With the new setup, I really can't see any difference in center position, regardless of which direction it approaches it. I think the CS101 is just marginal for a pull-spring setup, and giving it less resistance and a smoother action may have gotten it into an operating regime where it can actually do its job. The pull-pull rudder is working fine, btw.
Of course, the real test will be how it flies. Hopefully this weekend I can get out and give it a few chucks. If it fails that test, I'll swap in new servos - even after thinking it over, I'm still leaning toward JR DS188 for elevator and Dymond D47 for rudder, if it comes to that...