Got a used RS4 model with Nexspor servo's I'm trying to set up with Spirit and ran into an issue I haven't dealt with before - these servos have a very limited operating range (about 80 degrees total throw) and the swash linkages can't move further out on the servo arm due to lack of clearance.
When I set the recommended collective pitch range of 11° there is almost no movement left at the top/bottom. So if I increase cyclic pitch range beyond 6 degrees I don't have the full range of motion at full positive/negative collective. There is no binding, but the servos just don't move further, so if I push the cyclic stick and then go to full positive/negative collective the swashplate flattens out. Surely this is undesirable? Are these servos just trash, is RS4 geometry poorly designed or how am I supposed to deal with this?

I am not sure I understand 100% what you are observing. I would start by verifying the 6° calibration number ends up in the "90 to 150" range, as this tells you whether or not you chose the correct length cyclic servo arm holes. Then optimize the "Collective pitch" range and "Cyclic Ring (tuning)" range.

Hello,
what transmitter and receiver do you have ?
For me it seems you have maybe not full range of travel in your transmitter ?
But at first you have to set the geometry 6° tuning correctly, then the wanted pitch and the wanted cyclic ring - I hope you have set correctly the subtrim and the you should get at this position zero pitch at the blades -
Also it make no sense to have +- 11° pitch and only 6° cyclic ring - you have to set the cyclic ring also in the range of say of 9 - 11°, but this is dependend on your mechanics - you shall test this that you have no binding in any position max. positive/ zero/ max neg. pitch that you are safe to have no binding -

Regards

The 6° tuning is in the normal range and I get the full -100%/+100% on all channels in the diagnostic page.

The servos show the same behavior when hooked up to a servo tester. There is just a very low range of motion compared to the servos I'm used to work with. Due to how the RS4 is built one servo arm nearly touches the neighboring servo, so there's nothing else to be gained there.
So at full positive/negative collective (+/-11°) there is almost no room for cyclic movement because it already puts the servos at their limits.

Hello,
if the servos have such a behavior with a servotester, they are maybe not ok or the servo-tester has two different settings like normal or extended travel, this is what I do not know - what kind of servotester do you have or what settings you use -
But you can try that with an other servo if the travel is wider than with the nextspor servos then then you should use maybe some new servos like KST, GDW, MKS or Futaba - Are the Nexspor servos programmable ? I don't know them - I know only that livehobby have this servos - maybe you can ask Meik Gebauer what can be wrong ? Are you from Germany ?

If the throw is the same something other is not right, voltage is right (high enough) and the frequency is right too ? Otherwise I would have no further guess at the moment...

Regards

Thanks for the suggestions. I guess it is just an unfortunate combination of model geometry and servos that don't really work well together. If I could move, the ball link out just a few more millimeters it would likely be enough, but there is no space. If the swashplate was designed so the balls would be closer to the shaft it would work too. I can see why the previous owner dumped it.

I bought this used so these servos are new for me as well. They're 333hz 1520us, I've already tried lower frequencies just to be sure, but it doesn't make a difference. The active range is roughly 900-2000us which I guess is pretty normal? I will try to contact live-hobby to see how much travel they're supposed to have, nexspor site doesn't mention it. I don't think they're programmable.

Probably just going to throw KST servos on it, they have 100 degrees working range which will be plenty.

Anyway consider this solved because I can't fix it in the settings and it appears not a Spirit issue.

Hello,
only one question, is this the Venum-Version or the normal Version of RS4 ?
I have this Venom-Kit at home to bild and for this I have also KST-Servos choosed -
The non Venom-Version has special servos to be needed...maybe this is your problem ?

Regards

Hey, this is the Venom version.
The non-Venom servos have nonstandard mounting holes (from the side) so mounting other ones wouldn't have been possible.
If I directly compare KST servos I have on one of my other helicopters, the total operating range is about 20° larger. KST specifies +/- 50° (total 100°).
The Nexspor CLS2310S reaches about +/- 40° but I don't have the official spec. It's not something I've ever considered when choosing servos because you just expect it to be enough. I think 80° is bit lower than what you'd normally expect, but the extreme ends of the range are undesirable anyway because you start getting sideways movement. So I really blame the RS4 head design for requiring such a long throw.

Hello,
yes you are right, this are special servos which are special mounted, I forgot...
This was the reason for me to take the Venum version - that sounds of course not very well if the geometry is so bad - I will see that latest in the end of the year (time to build it) ...

Best Regards
Matthias