rbort
Elite Veteran
Location: Franklin, MA - U.S.A.
My Posts This: Topic Forum | Wow, lots of interest!I'm getting alot of PM questions so I'm going to answer them here. First off I uploaded the pictures of my setup to my gallery. You can click on that and view them, same pictures as the link, but larger.
The motor chosen for this is the AXI 2212/34 as you can see in the picture because a) its small and light, and b) its wound with specs of 740 rpms / volt which will make it produce more voltage than another motor with higher rpms. You want lower numbers to get more power out of the motor. If you look at specs, this one seems to be around the lowest around and is ideal for this.
You probably can't make an on-board starter with this motor. I start the MIT g231 motors with an electric start but they are tough to turn over unless you are using 24 volts. 12 volts doesn't cut it unless they are hot already. With a removable pull start, its not necessary to add on-board batteries to start the engine, unless you want to do it for fun of course! But in any case, I don't think the small AXI motor can even dream of turning over the Zenoah motor, its just too small.
The BEC that I use is especially designed to filter noise out (read the specs for it) and I didn't see any radio issues flying with this setup. They do make a 6 volt version as well if you need more power to the servos, but at steady 5 volts I don't see the need -- more power = faster failure rate in my opinion. I did just look at the SBEC and that seems to be limited to 2.5 amps max current load. With my gasser, I am drawing around that much on average during 3d flying so it will be marginal. The UBEC is rated a 3 amps with a 5 amp surge, so it has more margin for current draw without burning out.
This motor can generate an easy 5 amps output and will probably max out at around 10 amps. Way more than you need for general everyday flying plus some reserve to power up some other things if you like.
I can't wait to go to a fun-fly this summer with my heli, a gallon of gas, and my transmitter and NO field charger or extra battery packs. Just gas and go and gas and go and gas and go all day long!! :-)
If you want to set one of these up for you, you will need the motor and a spider coupler from Jameco. Here is a link from Jameco:
http://www.jameco.com/webapp/wcs/st...ategoryId=12332
You will need the 0.125 coupler for the motor, the 0.250 coupler for the 6mm clutch shaft though this one is a bit loose fit and I'm going to retry to setup mine with the 0.197 bore and drilling it out to 6mm for a better fit. I also drilled and tapped the couplers with a second hole so there are two set screws to hold it on instead of one. Oh yeah, throw out the flat head set screw that comes with it and replace it with an allen driven set screw.
I made the mount from a broken Xcell front tray plate. Cut it in half lenghwise, removed the broken edges, and drilled holes to bolt it using the clutch bolts -- I just replaced them with longer bolts. Using a couple of gold xcell parts connecting cubes, I was able to bolt a top platform to the side plates coming up from the clutch bolts. You center your motor on the top plate so that it is aligned with the clutch shaft and use washers where needed to adjust the fit. I ended up having to use plastic landing gear spacers and my vertical plates were too close together and I needed the room for my gv-1 disk seen in one of the pictures. If you are using a stator gator you will not need a magnetic pickup as I have done with the disk before the jameco coupler.
To build the AC to DC circuit, look at this:
http://www.itee.uq.edu.au/~sansom/l...tronics_big.pdf
Scroll down to Three Phase Full bridge rectifier. Basically you are using 6 diodes, each wire from the motor goes to two and the diode ends are all connected together with a 25v 4700mf capacitor to smoothen out the voltage before going to your BEC regulator. You need a big enough capacitor to get reliable power at idle. First I used a 1000mf capacitor and noticed that at idle with no receiver battery my servos worked, but they twitched due to uneven rpms by the gas motor. Putting a bigger cap on fills the gaps of power when the engine rpms drop, and the servos are solid and operational at idle. I always get a kick out of turning the receiver switch off (battery) and showing people at the field that the servos still work until I issue that last command to kill the engine. Of course you would never fly with the receiver battery off, but its just a good test on the ground to see that your generator is working.
If any of you guys set this up, let us know how you make out!
-=>Raja.
1005 Gasser, G29 Big Bore Hanson, 2255+ flights
Spectra-g, G26 3DMax, 920+ flights
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