Mr. RC sound system timing of sound with propeller rotation?

[Bluebird]

Hi there gang. I have the Mr. RC sound system in my 1400 mm FMS Corsair It is the older version that I bought a year and a half ago. It sounds great but I'm having an issue trying to get the starter sound to kick in before the prop starts turning. I've tried adjusting the throttle trim but it doesn't seem to help as the sound becomes delayed also.
What am I missing here? Thanks!

[Bluebird]

PS I'm using a Spektrum DX9 transmitter. Cheers!

[WintrSol]

I have mine set up with a throttle cut switch, which is adjustable (Futaba). The cut switch subtracts from the throttle signal, and I set it up with just enough shift that I can plug in the flight battery, then apply the cut switch, then plug in the sound card, which uses the cut value as zero throttle. Then, I can remove the cut switch and add a click or two up trim on the throttle, starting the sound card and motor about the same time. Then, when I land, the sound will stay on until I taxi back and cut the throttle.

This only works with an ESC that remembers a fixed range for the throttle; I have Castle Creations ESCs, which normally capture the range dynamically, so applying the cut switch would move the zero throttle in them. I had to change from default to use a fixed throttle range, then adjust the limits of the transmitter to match the ESC.

[Bluebird]

Thank you WintrSol for the helpful info. and detailed answer. Interestingly, I watched a video this morning of a Corsair starting up and the sound of the starter coincides with the turning prop which makes sense with this airplane. I had been under the impression there was a delay between the two. So I have to admit the problem then is not the timing but keeping the propeller speed low enough at initial start up to look real.
I use a throttle stop switch on my Spectrum radio also. You gave me an idea that if I use one of the adjustable switches on the radio, perhaps i could affect a slower initial speed at startup.
I'm presently attempting to fit the oleo struts from the new 1400mm FMS P-40B to my Corsair. Once this is done I will have another go at the sound system. Also if this project is successful I'll write about it.
Thanks again.
Regards, Bluebird

[Pheonix]

Bluebird, I am doing the same thing. The only problem with the P40 gear replacement is the short wheel arm (axis). You will have to extend it some how are get new tires. The 2 3/4 Dave Brown Lite Flight wheels will work with some modifications.

[WintrSol]

The sound card needs a minimum shift in the pulse width to go from off to on, which is sometimes greater than what an ESC needs to start turning the motor. I set my switch to provide just enough of that shift that a couple clicks on the throttle trim started them both. I have a servo tester that also measures the pulse from the receiver, so can easily arrive at those settings.

One other thing - in my setup, the sound card needs less increase in pulse width to start than it needs to stay on, so if it takes ~20uS to start, if you drop it to that amount on landing, it will stop during landing or taxi, so using 20uS as the reference, I set the switch to about +5uS over the sound start value. These numbers are made up, 'cause I didn't write them down, so you need to find your settings by experiment; just be aware that assigning a given offset to your switch may start the sound and motor, but it may quit before you want it to, until you get it tweaked out.

[Bluebird]

Pheonix that's interesting that you are doing the same upgrade. If the axle is the only problem then I'll be fairly happy. As you say, a change of tires could solve that issue. Thanks for the tire recommendation. I ordered the P-40 set just yesterday so haven't had a chance to check them out yet. Good luck with your modification. Perhaps let me know how it goes.

WintrSol thanks for the further info. on your system. It sounds like a servo tester of better quality than what I have would be very useful. Also sounds like you have the technical side of this problem sorted out pretty well. I'll have to see what I can do with the equipment I have.
I appreciate the help!

[Pheonix]

Bluebird, I finished my modification and things work well. I happened to have same tires that I purchased from Maxx products, stock number AW275. The inserts for the axis is only 4mm on these wheels. The axis on the P 40 struts is 5mm. A little drilling will take care of the problem. I have a sound system and will u[ grade the motor with P 40 motor as well. Unfortunately, I did not have the motor mount and had to order one. I have version 1 and it really flies well. I managed to get an extra set of wing from a Vendor that was going out of business. No need to buy the new version when the old one really flies well on a 4000 battery and 110 ESC. You will need to modify the gear doors as well. Good luck.

[Bluebird]

Pheonix that will be one hot airplane when you're finished. I really like the idea of the motor upgrade and was considering the same motor for my 1400mm Folke Wolf which is a great flyer but could use a little extra power.
RE the Corsair, I have the version 3, the most recent one. It has been a disappointment up till now due to CG issues. It's finally sorted out but only after removing factory installed weights in the nose, a total screw up at the factory as far as I'm concerned, so you haven't missed anything. It sounds as though you will end up with the better plane anyway.
Thanks for your helpful info. Once these oleo's are installed and the sound system tweaked this plane will finally be a great one to own. Good luck to you as well!