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Old Nov 11, 2007, 06:56 PM
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lupy's Avatar
Renton WA
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Help with thrust steering mixer

I have a Duseldorf fireboat that has an old 7ch futaba with a 12ch keycoder to control all the functions. I want to add thrust steering so that I can control the direction without moving forward, esp when using the high powered monitors which push the boat around a bit.

I got a cheap mixer board, connected to my two matching esc's but when I wired it in, the steering servo dosn't work anymore. If I unplug the mixer, the servo is fine. The mixer is damping out the signal somehow. I tried adding resistors in the signal line to the mixer, but it stops the mixer from working before the servo starts working again.

Is my mixer board just a poor one? or are all of them going to do it?

Is there a simple solution to this?

Thanks
Ken
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Old Nov 11, 2007, 09:26 PM
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Quote:
Originally Posted by lupy
I have a Duseldorf fireboat that has an old 7ch futaba with a 12ch keycoder to control all the functions. I want to add thrust steering so that I can control the direction without moving forward, esp when using the high powered monitors which push the boat around a bit.
Hi Ken
Before you go delving in to mixers and extra functions on your radio, i think you will find with plain rudders and props, the Duseldorf fireboat wont go sideways to counteract the monitors.
Unless you have Kort nozzles, Z Drives and a bow thruster she wont be able to do the manouvers you describe.

I think at best.. with slow throttle and a little hint of rudder you may be able to counteract the monitors, but only in the opposite direction to the monitors.
"For every action, there is an opposite, but equal reaction"
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Old Nov 12, 2007, 12:51 AM
Taking care of the pond.
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Joined Apr 2004
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"For every action, there is an opposite, but equal reaction"

Speaking of Newton, and I have more than 1 Newtonian telescope.
Has anyone seen Comet Holmes?
Don M.

http://www.skyandtelescope.com/obser.../10862521.html

Sorry I got off topic.
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Old Nov 12, 2007, 10:56 AM
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victoria, bc
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Curious as to what you have powering/feeding the monitors? Any photos?
Thanks, mike
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Old Nov 12, 2007, 01:49 PM
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Renton WA
Joined Oct 2001
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here are some pics, it's all torn up right now. The pump started out as a Jag windshield pump, but the bearings melted out. so I used a fairly low KV speed 500 sized johnson motor. I had to drill out the monitor jets to keep it from blowing out the fittings and hose. It will go around 25-30ft. There are three monitors, the front is controlled with the left stick, and the rears move together with the sliders. Motion limits are about 220 deg of rotation and about 45 deg of elevation. The rears rotate more than the fronts.

My quest to add diff thrust started when my son made some paper boats for me to light and then try to put out with the monitors. It's surprisingly hard to do as the boat keeps twisting around due to the thrust of the jets. There is no way to twist back without moving forwards or back, which even at slow speed quickly moves me out of range or into a position where I need to switch from the front single to the rear twin monitors. I don't really need to move truly sideways, but the ability to twist in place would really help.

After a little more research, servo city has a line signal booster which should do the trick. otherwise, there is a servo synchronizer that will deff do it.
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Old Nov 12, 2007, 02:51 PM
Veni, Vidi, Feci
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Whose mixer is it, so we know what to watch out for?

PM
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Old Nov 12, 2007, 03:05 PM
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Renton WA
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good point, here it is:

http://www.bidproduct.com/part/Produ...SERVOS_20.html

Wasted a whole $3 plus shipping!

If anyone has another mixer, It would be interesting to see if it too does it. I am also going to try it with a modern rx, it could be that the old rx dosn't output as strong a sig. I am sort of stuck with this one though, as it's on ground ch's and has the keycoder.
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Old Nov 12, 2007, 03:13 PM
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OK, if you plug the two ESCs into this on the right side, where do you plug in the rudder servo? Is it Y'd into the Rx with one of the mixer's left hand leads?

Pat
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Old Nov 12, 2007, 03:36 PM
excuse my poor english...
Jettaheizer's Avatar
Germany, RP, Asbach
Joined Dec 2003
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Hi Ken,

so you got a mixer for aircraft with delta wings or V tail. Should be no problem. Just plug in the elevator channel into the thrust channel of your receiver. Then plug in the escīs to the mixer (if they run to the wrong side, just change them at the mixer). The rudder/aileron channel of the mixer has to be plugged into a Y cable and then into the rudder channel of the receiver. The rudder servo has to be plugged in the other connector of the Y cable.

Greetings,
Franz
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Old Nov 12, 2007, 11:39 PM
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Waukesha, WI
Joined Dec 2006
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Hi Ken
I have the same Dusseldorf. I use a vantec mixer ESC running two geared Astro 40's.
I use one stick of transmitter with speed on vertical axis and direction on horizontal.
Using standard 4 rudders and 2 props my boat rotates on its own axis. Both motors powered w single 12 v 3400 mAh battery and runs a good 1 1/2 hrs. With enough ballast in boat the mass keeps boat from moving from force of fire nozzles.
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Old Nov 14, 2007, 10:05 AM
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Renton WA
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Yes, it's a Y connector on the rudder, so the rudder feeds one servo and one side of the mixer, the throttle being the other input for the mixer. Rudder works fine without the mixer connected, so the wiring is right, with the mixer plugged in, the motors work fine, mixing properly, but no rudder servo.
I think there is something in the mixer damping the signal to too low a level for the rudder servo to pick it up.

JShander:
Sounds like your is set up the same as I am trying to do. I am using two mtronics marine 20s. My main question is wether my cheap mixer is the problem, or is my old RX putting out too low a signal. Either way, I am probably going to just buy a Futaba servo synchronizer, it has one in and four outs, independantly adjustable, which should do the trick.

My monitors are fed by a high power pump with drilled out nozles, so the thrust is a lot greater than a stock pump would provide. The total weight puts it at the correct waterline. I am running the stock Robbe 6v drives, but on a 7.5v Lithium battery I built. ~22,000 mah, It will tow me around in a Kayak at a resonable speed. It used to heat up the motors, but I added cooling coils and a separate water pump which runs all the time at low speed. Now everything is nice and cool. I also have a 2000mah 12v battery to run the pumps and sound
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Old Nov 16, 2007, 04:28 AM
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Waukesha, WI
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Ken,
I doubt the receiver signal is weakened with your setup. If you can borrow or have access to 2 servo drivers(one for rudder one for speed ctrl) you can test your setup w/o the radio.
I originally used an ASTEC equivalent mixer from Captain AJ in Texas with 2 ASTRO 205 reversing ESC's.

The system fried because I forgot that each ESC had a separate 5V BEC from the red wire on the ESC. Within a minute I smelled the telltale whiff of melted epoxy on the mixer. Fortunately the ESC's are rock solid and still work.
Mixers do not like dual BEC's
Also I am not familiar with the voltage parameters on your ESC. Does yours have a BEC and if so is the voltage you are using allow it to function properly?
Jim
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Old Nov 16, 2007, 04:33 AM
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Waukesha, WI
Joined Dec 2006
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Ken,
One other suggestion. I use a separate forward only ESC to operate my water pumps.
The pump starts out with slower force and I can adjust distance of spray.

I find this puts less stress on the plumbing and keeps the silicone tubes and the
nylon ties from pulling off my quick connector fittings.
Jim
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Old Nov 16, 2007, 04:51 AM
excuse my poor english...
Jettaheizer's Avatar
Germany, RP, Asbach
Joined Dec 2003
122 Posts
Is it possible your BEC current is too low? With your setup there are two escīs and one servo that burden the BEC at the same time. Maybe thatīs too much.
I would try your setup with cut off BEC and a seperate receiver battery.

Greetings,
Franz
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Old Nov 18, 2007, 10:54 AM
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Renton WA
Joined Oct 2001
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Jim, thanks for the idea of esc's for the pumps, I will probably do that if I build another boat. This one runs the pumps off of the keycoder switches. The six other ch's are used in aiming the front and rear monitors, throttle and steering. I supose that would allow the removal of the elevation control, which would make installation much easier.

I tried a separate battery, same results. I am using only one of the BEC's.

I broke down and got the futaba synchronizer from tower ($10 off code) I didn't use the power jumper, as the mixer puts power to both of the lines, even though only one is fed.

End result is that it works fine now. I left the old Y I was trying to run the steering servo with origionally, and now it works fine too, so I think the mixer, (now buffered by the synchronizer ) was the problem. One advantage is that now I can adjust the throw of the steering servo independant of the mixer and ESC.

Thanks for all the ideas
Ken
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