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Install servos on gear doors??

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Install servos on gear doors??

Old 01-31-2024, 04:42 AM
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Default Install servos on gear doors??

I am building a Tamjets F-16 and would like to install servos on gear doors i have 3 Hitech 5125 which i intend to use. Are these suitable for this application? or i need servos that would turn off at the end of course (any idea which brand/type)
the idea to use the hitech 5125 relays into the fact that i can program each one independently on the programmer.

On another note, any particular thing to know/avoid while installing the servos for the doors, knowing that retracts/brakes are still air operated...


Old 01-31-2024, 07:49 AM
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You don't want servos that turn off after movement, similar to retract specific servos, because air flow or g forces could pull the doors open in flight.

For set up make sure your linkage gives you the best mechanical advantage over the door as possible. I can't count how many times I've seen people put the linkage all the way out on the servo arm and turn the travel down to 30% to get the desired throw. For doors I like to use 2-56 ball links, they give you some leeway if things don't move in perfect alignment. Make sure there's no binding when the doors are open or closed to prevent excess current drain or burning out a servo. Lastly, be careful not to bump the doors or try to move them when powered off. In order to make them as thin as possible thin wing servos like that usually have smaller than normal gears that are easier to strip.
Old 01-31-2024, 08:37 AM
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The biggest i see with people using servo’s on the gear doors is improper setup like the previous guy said. In addition, the servo and linkage should be setup so when the door is closed, the pivot location on the servo arm, servo arm screw and the linkage connection at the door should all be inline with the linkage centered over top of the servo screw. This puts the entire setup in a way thay eliminates force on the servo and reduces power consumption from the servo since it isnt constantly fighting the wind to pull the door open.
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Old 01-31-2024, 03:37 PM
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If you already have an air system installed why not use air for the gear doors?

You can restrict the stroke of air cylinders by putting pieces of plastic tube on
the shafts & a jammed/damaged door will have no electrical consequenses.
Old 02-01-2024, 12:36 AM
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Fist of all, thank you very much for your input which is very valuable. i would like to say that initially i wanted to convert the air cylinders to electric ones but the E actuators i have would require major butchering in the main wooden former which would eventually compromise the strength of the bulkhead. Anyway i still have to make some trials to see if the servos would fit and linkages would clear intake and main gear...

Lastly, how should i synchronize the e-doors with air retracts as i also intend to use the behotec air valve which also acts as break valve and can use only one channel to activate both functions. Done successfully that on that set up on 2 other jets.
Old 02-01-2024, 01:08 AM
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Most modern transmitters can put a delay on a servo moving so typically for gear down no delay on the doors but maybe a short delay on the gear and on gear up a delay sufficient to allow the gear to go away before the doors, I use this system on the doors of a p47 with a Futaba tx
Old 02-01-2024, 01:34 AM
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rfbenn,

Thank you. i am also using Futaba TX. Reason i am asking is specifically related to the Behotec valve i will be using and would not want the delay to affect the braking function,,, is there a way out of it?
Old 02-01-2024, 08:55 AM
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Originally Posted by extra 300
rfbenn,

Thank you. i am also using Futaba TX. Reason i am asking is specifically related to the Behotec valve i will be using and would not want the delay to affect the braking function,,, is there a way out of it?
In your transmitter use the AFR for the channel you wish to use go to screen 2 at the bottom of the screen there is a speed in and out you can change the numbers , higher numbers mean slower movement 0 means full speed. If you have conditions you may also be able use the delay function.
If you apply the delays to the door servos only it will have no effect on the servo used for the behotec.
This is based on 16IZ, 16 & 18SZ’s and 32MZ
Old 02-01-2024, 04:38 PM
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Originally Posted by extra 300
rfbenn,

Thank you. i am also using Futaba TX. Reason i am asking is specifically related to the Behotec valve i will be using and would not want the delay to affect the braking function,,, is there a way out of it?
If you want to use air, you need a separate valve for the doors. It can be controlled by the same servo that operates the Behotec valve.

Last edited by causeitflies; 02-01-2024 at 04:42 PM.
Old 02-01-2024, 05:34 PM
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Does your radio have a built in door sequencer? That's how I do mine with my Spektrum DX18.
Old 02-02-2024, 04:45 AM
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I have converted a few of my jets to servo or actuator operated doors along with still using air gear and brakes. If you still want to use a gear failsafe its not possible with the radio sequencer. I had to use separate gear controller sequencers along with a tams failsafe or other type to trigger the elec doors at the same time as the low air signal triggering the gear. If you dont care about the gear failsafe using the radio sequencer works fine.
Old 02-06-2024, 02:02 AM
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Originally Posted by rfbenn
In your transmitter use the AFR for the channel you wish to use go to screen 2 at the bottom of the screen there is a speed in and out you can change the numbers , higher numbers mean slower movement 0 means full speed. If you have conditions you may also be able use the delay function.
If you apply the delays to the door servos only it will have no effect on the servo used for the behotec.
This is based on 16IZ, 16 & 18SZ’s and 32MZ
rfbenn,
For retracting the gear the delay on doors is no problem. what about when extending the gear, the doors (servos) will definitely move slower than the gear, thus my question regarding delay on the gear servo/behotec valve....
Old 02-06-2024, 02:04 AM
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Originally Posted by causeitflies
If you want to use air, you need a separate valve for the doors. It can be controlled by the same servo that operates the Behotec valve.
The idea was to use servos for the doors, and avoid air system on the doors....
Old 02-06-2024, 02:06 AM
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Originally Posted by rcmigpilot
Does your radio have a built in door sequencer? That's how I do mine with my Spektrum DX18.
Believe that my Futaba 18 MZ does not support the door sequencer programming.
Old 02-06-2024, 08:04 AM
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Originally Posted by extra 300
rfbenn,
For retracting the gear the delay on doors is no problem. what about when extending the gear, the doors (servos) will definitely move slower than the gear, thus my question regarding delay on the gear servo/behotec valve....
Extending is no problem there is enough built in delay with the air valve cycling etc the doors will fire right away and be out in front.
Old 02-06-2024, 01:02 PM
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Extra 300, an MZ18 is a high end transmitter, sure there isn't a sequencer in there somewhere?
I don't own an MZ18 but have done some basic programming on one for a friend.

I use a 14 channel FG-12, no sequencer but with creative use of point mixing & timers you can
achieve the same result. I use it for both servo driven doors & air driven doors operated by a servo
operated air valves.

Last edited by Boomerang1; 02-06-2024 at 01:13 PM.
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Old 02-07-2024, 01:30 AM
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Servo operated gear doors are no problem if set up correctly. .I use JR 8711s on the main doors 8411s on nose. This Hawk and my other AW Hawk have been flying with zero problems for 14 years ! These main doors are big and remain open, gear down.
Control by Jettronics sequencer, now with Core sequencer.

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Old 02-07-2024, 01:54 AM
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Believe that my Futaba 18 MZ does not support the door sequencer programming.
It's there in the Prog Mixes - look at the alternate type of mixes available.
Just takes a little time to get it all set up correctly.

modtron
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Old 02-16-2024, 04:17 AM
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Update on the install: i was unable to achieve proper movement with the servos, Extending the arms to get more movement got in the way of wheels, space being very tight.
to make a long story short, i installed the air actuators and the Tamjets release valve to have gears and doors working on one servo. using the Behotec valve would eventually permit to have gear, doors and brake on one servo.

The new problem is that system seem to leak air. at first the door valve was not leaking air although the whole system did. now in addition, the TJ valve is also leaking air although it is well closed....

Thanks for looking and giving suggestions.


Old 02-16-2024, 02:12 PM
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Originally Posted by extra 300

The new problem is that system seem to leak air. at first the door valve was not leaking air although the whole system did. now in addition, the TJ valve is also leaking air although it is well closed....

Thanks for looking and giving suggestions.
Now it's just a matter of normal, air system fault finding. Don't be afraid to just run the doors through a seperate mini servo driven valve on another channel mixed through the radio. Don't confuse 'leaked' air with 'used' air if you are using restrictors, sometimes you can hear a hiss some time after hitting the retract switch as the air bleeds off.
Old 02-21-2024, 12:12 AM
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Second update on the setup,
i was able to test the system when gear is open by pinching the feed line thus isolating the air tank/valve and gauge from the rest and apparently the system doesn't seem to be leaking air as the actuators stayed pressurized in the open position with the little air that was trapped in the system When i released the feed line automatically the door actuators relaxed and lost pressure.
At least i am ok with gear down....
When the gear is retracted i can hear a little hiss sound coming from the door valve but haven't yet been able to determine the cause although it seemed to be working without issue a few days ago...
Any suggestions?
Old 02-21-2024, 03:41 AM
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Chasing air leaks is a pain
I converted my gear to electric , very easy process and no air leaks to worry about anymore
Old 02-21-2024, 02:50 PM
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If you are using a normal spool type main air valve you can drive them through too much travel & they will vent air.out the
end of the valve, Make sure the spool is not travelling too far.

If you are using an all singing, all dancing electronic air valve with brakes included I can't help you, I'm not familiar with
those.I have one jet with an electronic valve but it's a simple two hose on/off valve.

Remember that with each cycle the spool valve will vent some air, that's why you only get a limited amount of cycles per
refilling the system with a compressor.
Old 02-22-2024, 01:25 AM
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Originally Posted by scoeroo
Chasing air leaks is a pain
I converted my gear to electric , very easy process and no air leaks to worry about anymore
I had the option to convert to electric but the Lado actuators i have, would have required a lot of butchering in the main bulkhead which would surely compromise fuselage strength,,,, Reason why i kept the air system.
Old 02-22-2024, 01:29 AM
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Originally Posted by Boomerang1
If you are using a normal spool type main air valve you can drive them through too much travel & they will vent air.out the
end of the valve, Make sure the spool is not travelling too far.

If you are using an all singing, all dancing electronic air valve with brakes included I can't help you, I'm not familiar with
those.I have one jet with an electronic valve but it's a simple two hose on/off valve.

Remember that with each cycle the spool valve will vent some air, that's why you only get a limited amount of cycles per
refilling the system with a compressor.
What i did is isolate the valve/tank/filling valve and gauge after filling the system up with air. so the remaining air in the system was just enough to fill the tubes... in my opinion, the best way to check if your active circuit is leak free...
Still my problem relays on the TJ valve that controls the doors after retracting the legs which activates this valve for the doors.


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