Ah, ok. So does that use the same belt drive primary the Mongoose has? I’m not sure what happened with Airstar, there was a lot of stories circulating at the time a few years ago. Then Evolution closed their doors too. The electric craze in the last few years left the market with not much selection in gas helicopters anymore. I briefly made some experiements with electrics, mostly smaller ones because the batteries get pretty ridiculous for anything much over 600-class. And 600 is also the transition to gas, as it’s about the smallest size that can handle gas engines.
At any rate that should make a pretty good UAV helicopter with a good autopilot in it. I imagine it uses the same ~9.5:1 gear ratio the Mongoose has. And with the big rotor and light disc loading probably gets down to around 20cc/min in hover with a G290. That’s one of those helicopters where you take it out and fly it for a half hour, look in the gas tank and wonder just what does that engine run on anyhow? Because it looks like it’s got the same amount of gas in it yet that you took off with
Yup, same belt drive system as the mongoose. I have an assortment of clutches and gears to play with to get the engine and rotor rpms happy with each other. I plan to get some frsky sensors too to measure engine RPM and temperatures. I’ve only flown this heli as basic as they can get (no flybarless gyro, no governor - just eyeballing headspeed and engine rpm, cheap tail gyro, small fuel tank mounted way up front to get CG, with a receiver battery plugged straight into the receiver. I’m satisfied so far which is why I started this post. I’m ready to outfit this platform the way it deserves
Hint: for engine rpm and temperature you can use the SP-RPM for FrSky and hook the two wires on the module to the ignition primary on the magneto. Set it to 2-pole, or “blades” or whatever they call it in the settings. It works. I have some Lua scripts for the Taranis that you can enter in the gear ratio. It will show headspeed, calculated from engine rpm, on your radio screeen. Just let me know if you need that and I’ll send you a Lua script for it.
That SP_RPM sensor also needs a small ferrite toroid or bead on the wires from the ignition primary to kill common mode on the wires from the magnets on the flywheel passing. Otherwise the rpm reading will not be accurate.
If you want even fancier telemetry on your Taranis you can put a C&T telemetry cable on your Pixhack V3 to the Smart Port on the receiver. I got a Lua script that will display engine temp, OAT, headspeed, heading, altitude, flight mode, ground speed, altitude (AGL), altitude (MSL), GPS number of sats, battery voltage for your servos, receiver voltage, and RSSI.
Yes, it works fine. You can also use a small RF coil out of an old radio or something and generate a sine wave with the magnets on the flywheel with it. All it looks for is a sine wave that it would otherwise get from an electric motor. I’m using it on two gas helicopters and it works great. It’s only a ~$20 item at Aloft Hobbies in CA and comes with two TEMS-01 thermistor temp sensors. I use one sensor for OAT, and glue the other one to the engine block on the crankcase side of the exhaust port.
Sorry for the late update,
Been on vacation for a week then away for a flight test for work.
I’ve been going through all the nuts and bolts on the heli making sure loctite is well applied.
I’ve also been working on wire management, utilizing my 3D printer for wire brackets, tie-downs, component mounts, etc.
CUAV Pixhack V3 has been ordered and received, along with M8N GPS
I received the Frsky telemetry for temperature and rpm, still gotta mount and wire all that
Started wiring up the on-board generator
The gear ratio is actually 10.90:1 instead of 9 something. I believe the RPM for this machine should be around 1000, so this should put the engine RPM right around where the torque is highest in its range for the G290 (with 30.5cc conversion), at least I hope so?
30.5cc is a 2mm stroker. Which stroker engine did you get?
1,000 rpm is about right on the money for your size rotor. Different folks have different ideas on this for electric (to try to get flight time at the expense of performance), but at 1,020 rpm you are 450fps blade speed which I consider ideal for UAV heli. And that’s 11,000 engine rpm, which is also ideal, but depending on the port timing of your engine. If it has had port work done to it it is going to want to run higher rpm than that.
Unfortunately I’m not too familiar with this engine (I’m more familiar with airplane style engines like DLE, DLA, etc.) I also did not directly purchase this engine since it was included in the package deal of this heli. It does however have ESP 30.5cc labels on it. After a quick search, it looks like it is indeed ported. Can’t seem to find any rpm/torque specs for it
Just try it. You can make a dyno out of an old 10SI car alternator, a half-dead battery, a POT to vary the field voltage and thereby current independent of the voltage regulator, a current meter to measure the amps, voltmeter for voltage, and a tachometer to measure the speed. There’s some losses in heat in the alternator, but that’s not an issue. What you want to determine is where the engine produces its peak power.
I’ve dyno’d these engines before - drive the alternator with a lovejoy coupler that fits the taper on the crankshaft and the 17mm shaft on the alternator. It’s a “poor man’s” electric dynamometer for small engines.
Update:
No longer going to be a 1200mm sized machine. The majority of blade sets that I have for this heli are Spinblade 1050mm (semi-symmetric). I only have 1 set of 1200 sized blades and they are unmarked and I can’t find any new ones online in case I ruin this set. Also, I think 1050mm blades have a max rated rpm of around 1300-1400 according to spinblades which should be better for my engine.
Got the Pixhack V3 mounted, as well as the GPS (had to extend the cable a bit). Both are vibration isolated. I can easily stiffen or loosen the isolation mounts depending on how the vibe data looks once I run the engine up on this thing.
All servo wires and autopilot wires have snake skin wire wrap and neatly tied up to the frame w/strain relief going to the pixhack.
Upgraded to turnbuckles on all the swash links.
Mechanically zeroed the swash and head, as well as set up min and max pitch angles.
Next to do is:
Mount and plumb fuel tanks
Mount avionics battery (2s lipo)
Mount servo BEC (steps down 2s lipo to 6v)
Mount generator setup
Mount temperature and RPM sensors (considering hooking up the frsky rpm sensor to the generator motor since it was designed and intended to be used on a brushless motor), Chris, do you have a link to the ferrite toroid you use for hooking up to the zenoah ignition wires? I’m still considering doing it this way too.
Got excited today and decided to do a little test hop with the heli even though it is not completely ready. I had originally planned to only run the engine and fine tune the idle pwm and critical rotor speed pwm while checking the vibe data. Things were looking good so I held if off the ground at around 2-3 feet to get a feel for it. I was quite surprised how well it did!
Things to note for those that will view the log:
The CG was not correct (pretty tail heavy), so you’ll see me holding an offset in pitch
I haven’t messed with hover roll trim values, so you’ll also see me holding some roll
Also, how do I load some of the 3.6 param files that Chris recommends? I just tried manually setting each value but QGC won’t let me input some of them. For example: ATC_ACCEL_P_MAX 52000 , I can’t manually input 52000, I only have the options of very slow, slow, medium, fast, unknown_110000
It should fly pretty decent with those settings. You may have to fine tune the tail, and if the ATC_RATE_x_MAX values in degrees/sec of frame rotation are slower than you like, you can speed those up. Those settings I arrived at more for scale type flight, sort of a balance between “fast enough” handling, but gentle enough to not be overly snappy. Those settings are new for Copter 3.6.
