Mixing ESCs for 3 motor control...

[Jim Duda]

CG Bob told me that conceptually this will work, so I'd like to hear some opinions from PT boat drivers as to the practicality of it...

ESC#1 (Center motor only) will plug into Throttle channel. ESC#2 (both outboard motors) will plug into Flap (or AUX) channel. With MIX switch OFF, the throttle stick will control the center motor only...FWD - STOP - REV. With MIX switch ON, ESC#2 will synch up with ESC#1 at whatever position the throttle stick is in...SLOW, CRUISE, ATTACK SPEED, STOP, REVERSE, etc. (see pic for MIX switch location on the Tx...pulling it toward you turns it on.) Regardless of the position of the left throttle stick, turning the MIX switch off puts ESC#2 (outboard motors) in the middle or OFF position.

That way I can use one stick to control one or all three motors. On a 43 inch boat, with a 6-1/4 inch beam, having independent control of either the port or starboard motors doesn't seem effective to assist in turning it.

Freq is 50.960 - Channel 08

Comments?

[Ghost 2501]

left stick with v-tail mixer for outboard motors, right stick for rudder and centre engine, thats probably the best way to do it

[Jim Duda]

I think Bob is planning on using the two stick method...but either you would have to fight the center return spring on the right stick or take the Tx apart, remove the "elevator" spring and install a ratchet...I'm lazy and took the easy way out...(wink)

[Shaun Hendricks]

Some computer radios allow you to 'tie' channels together. You could use 3 independent speed controls and 3 channels. If your radio can do this, on your port and starboard motors, use mix with the steering servo control to boost (or retard) those motors depending on the direction. That should increase your steering ability at any speed. V-tail would probably work, but might mess things up unless your radio has a lot of 'steps' it allows additional input points at.

I was thinking of building a Tri-Motor style plane that did exactly this with my Eclipse7. It looked possible with the setup, but I never did test it. It can 'boost' a given channel up above 100%.

Sometimes you can open up the radio and remove the return spring or click a switch which lets it go off centering. My Eclipse does this, but it's an aircraft radio! DOH! :D

[Kmot]

Schnell!! Schnell!! Jim you rascal!! :D

[LtDoc]

Good grief, he's one of them 6 meter guys! ... Seems like it should work. There's never just one way of doing things so whichever way is easiest for you.
- 'Doc

PS - Completely beside the point, does the 50 Mhz thingy work out well? Considering what else uses that particular range of frequencies around here, I've been reluctant to try it.
(A couple of '2879's in that transmitter ought'a really increase range! Not that I'd ever do such a thing.)

[Jim Duda]

Here is the AMA approved freq list...
Bottom line, I have never had glitches on the 50 mhz channels. I did have a few hits on 53 mhz.

For Model Aircraft and Surface Model Use
6 Meter Amateur "Ham" Band
53 MHz

53.1
53.2
53.3
53.4
53.5
53.6
53.7
53.8

50 MHz

Channel No. Frequency

00 50.80
01 50.82
02 50.84
03 50.86
04 50.88
05 50.90
06 50.92
07 50.94
08 50.96
09 50.98

Amateur Radio Operator License Required for 6 Meters
(Technician, General, Advanced, Extra class)
(Other Amateur Radio Service [ARS] frequencies may be
used, as regulated by the FCC)

[LtDoc]

I'm afraid the 'problem' is sort of in the other direction here, not with the R/C radio. One of the wireless cable companies uses a 50 Mhz freq for one of their 'closed system' down links. Say more than three words on 6 and you have the cable trucks running around like ants. Guess who'z fault it is (so ~they~ say)? You'd think if it was really a 'closed system' it wouldn't have problems - lol. Oh well. Sorry for the OT stuff.
- 'Doc

[hookpilot]

I have a 60-inch scale model of a Vosper MTB with 15 inch beam. It is powered by 3, 18v drill motors through 3 Proboat ESCs. I'm using a Hitec Laser-6,6 channel surface radio. As a licensed captain of full-sized screw vessels, I never use differential power to steer boats at high speed, and I doubt that PT boats did it. On my model, I modified the transmitter by taking the spring off the right stick, filed a detent at the center position for "STOP" on both sticks. The two outboard motors are controlled by the left and right sticks independently. the center motor is controlled by the rotary Flap control knob on the top of the transmitter. There are 11 tickmarks on the transmitter top deck under the flap switch that it can index. I index the center motor ESC by setting the flap switch to the sixth tickmark. That is the "STOP" postion for the center motor. I can then use the joysticks to cross up the motors for docking. The center motor is off for this exercise. Underway, I start off with the center motor and then advance the outboard motors for high speed running. when docking I slow all throttles, stopping the center and docking and maneuvering with the outboard throttles as needed. The only drawback is getting everything stopped in an emergency. I'm putting two little dimples of silicon sealent on either side of the rotary switch pointer to make a center detent to aid in finding OFF for the center motor without having to look down and see where the pointer is. At any speed, my 30% oversized triple rudders turn the boat very effectively. In fact, running on just one of the outboard motors does little to alter heading, so using differential throttles to steer seems unnecessary.
Mike