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Old May 31, 2012, 05:24 AM
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Servoless retracts

Hi all,
I'm confused about how retracts work, whats the difference between servoless and electric retracts?
They both have motors and with both require a pulse to send them up and down - right?
I'm looking into making a sequencer but need to bottom this out first.
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Old May 31, 2012, 09:00 AM
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Instead of physically connecting linkages from external servo(s) to the retract mechanism servoless retracts include everything integrally, (we'll ignore air operated for now).

Along with a much simpler and more compact setup there are other advantages. The first is that with each unit built up ahead of time there would be no adjustments required for up and down to ensure the gear locked either way. The internal board has all the switches, motor drive electronics and also most likely current sensing circuitry to shut down the drive if there is a bind or interference with retract action. This is particularly important if there is only one battery source as a stalled electric motor can draw a lot of current and interfere with the rest of the radio and flight system.
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Old May 31, 2012, 09:13 AM
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For some reason I can't edit the previous post.

That internal board also interprets the signal from the Rx same as a standard retract servo. That means it will only travel the full amount each way depending on where related to center position the signal is for that channel.

Remember that all the receiver channels have signal outputs just like there was a servo connected. If you had a servo plugged into the gear channel you would only see it sweep one side of center to the other when the switch is flipped with the amount of sweep adjusted in the "Travel" or "AI" parameters page. There is no stick motion to follow.

A gear servo or integral servoless retract reads the output of the channel and if even slightly off center it will run the system all the way to the end in that direction. If you have a sequencer it should work fine, just remember the following.

The other advantages of servoless retracts over other types, particularly air is that the sequence is mechanical and should always require the same time to accomplish. This makes sequencing much easier and more reliable. If I have any complaint about servoless retracts it is that sometimes the gear transit is not scale and it is not adjustable.

Due to the above advantages I am swapping all my installations over to servoless.
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Old May 31, 2012, 09:43 AM
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Brilliant, thanks Cougar!!
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Old May 31, 2012, 10:42 AM
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The big advantage of the electric retracts is that they use a much smaller motor with less current draw than a retract servo. They can do this, due to a much higher gear ratio with the motor coupled to the gear train by a worm gear. Most electric retracts also run at a realistic scale speed, another big plus, since trying to slow down a proportional used on retracts is asking for problems.
Pete
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Old Jun 02, 2012, 09:51 PM
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Quote:
Originally Posted by Cougar429 View Post
For some reason I can't edit the previous post.

That internal board also interprets the signal from the Rx same as a standard retract servo. That means it will only travel the full amount each way depending on where related to center position the signal is for that channel.

Remember that all the receiver channels have signal outputs just like there was a servo connected. If you had a servo plugged into the gear channel you would only see it sweep one side of center to the other when the switch is flipped with the amount of sweep adjusted in the "Travel" or "AI" parameters page. There is no stick motion to follow.

A gear servo or integral servoless retract reads the output of the channel and if even slightly off center it will run the system all the way to the end in that direction. If you have a sequencer it should work fine, just remember the following.

The other advantages of servoless retracts over other types, particularly air is that the sequence is mechanical and should always require the same time to accomplish. This makes sequencing much easier and more reliable. If I have any complaint about servoless retracts it is that sometimes the gear transit is not scale and it is not adjustable.

Due to the above advantages I am swapping all my installations over to servoless.
cougar - I saw on a YouTube video that a guy was demonstrating a speed device put in series before the Y adapter to the two servo-less retracts, that allows you to slow down the retracts (it's adjustable too). But the guy never said who makes it or where to buy it. I agree with you, servo-less retracts are way too fast to be scale, but this would be a solution. Have you ever seen this device? It's about the size of a micro 72mhz RX (paper /plastic wrapped).

The demonstrator did comment that this device adds virtually no additional current draw too!

Anyone know of these and who's got em???
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Old Jun 02, 2012, 10:00 PM
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I may be completely wrong, but doubt it would work since the motor drive circuitry is part of the board and last in the chain. The signal decoding and current detect would have priority and hence simply try to run to each end depending on which side of center the signal is detected. You should be able to select anywhere from 10-100% either way and the retract should still function normally.

It may be possible to alter the current to the power input, but that would likely bugger the sensing system that is there to detect binding.

Be interesting to see. Do you think you can find it and provide the link. Like to have a boo.
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Old Jun 02, 2012, 10:09 PM
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Again I am not able to edit posts.

Anyway, forgot to mention a speed control system such as available from HK would work for delaying the retract cycle start by slowing when the signal reaches the center trip point, but the cycle speed would remain as normal. This perhaps could be integrated into a system used with gear doors as they would be the first to move either direction. That would work when the gear extends, but having them close ahead of the gear leg would be bad, MMMKAY!
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Old Jun 03, 2012, 07:41 AM
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HELP! Who makes sequencer for retracts

I saw a retract sequencer for sale on Ebay. Now I need 2 and can't find it again. What I mean is the doors open then retracts lower and the oposite. Does any one know where I may purchase these things? Please help.

Thanks
Rick Martin
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Old Jun 03, 2012, 08:56 AM
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HK have this model available at approx $13 each:

http://www.hobbyking.com/hobbyking/s...w_Display.html

I included the manual. From reports some of the settings may be different so you would have to experiment. Option L2 has the doors open, then close after gear transits either way.
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Old Jun 03, 2012, 09:25 AM
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Cougar

Thanks I just ordered 3.

Rick
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Old Jun 03, 2012, 05:16 PM
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Just love the brand name

The Chinese with Company or Product names, oh brother. In all deference to my wife, who's born in Taiwan (US Citizen for 20 years), the Chinese have an inept quality with picking "Proper Names" .... like this Sequencer, made by: AssAn. (Their Capitalization)

I ran into a one product by a Chinese company, where everywhere on the packaging they couldn't even spell Asian correctly .... "Asain" and "Asien". We both LMAO with that one.

BTW - That YouTube video I saw, and I hope I can find it again, showed a device that actually SLOWED the eRetracts at your selectable rate, it was NOT a sequencer. The guy doing the video says in the video that this was just for everyone's objection to the too fast operation of the Servo-less "e" Retracts.

If I can find the vid, I'll post it here. - fingers crossed.

THAT WAS FAST!! -- This is not the original YouTube Vid is saw, but it demos the same thing. And here's also a link to make you're own module, though the original video showed a module that someone is making to sell retail (still looking for that). So it IS possible, Cougar.

E-Flite Seafury Retracts with home-made servo slow (0 min 59 sec)

Make your own - http://www.rc-cam.com/ldtastic.htm
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Last edited by makeitworst; Jun 03, 2012 at 05:26 PM. Reason: Links to Servo Slow-down module
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Old Jun 03, 2012, 05:27 PM
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I'd love to see that video too. I'm more than a bit skeptical, since the ones I've seen do not operate proportionally.
Pete
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Old Jun 03, 2012, 09:32 PM
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makeitworst, I went to view the link and the date is from 04 and shows the function being used on a standard retract servo, (with programmable outputs for lights). I have done the same thing by modifying the Hitec HS-77 servo to run 180 degrees and controlled the speed with an adjustable module.

NOTE: The HS-75 retract servo and -77 run identical geartrains with a different control board and pot, (limiting it to 45 degrees from center). By modifying the -77 servo for 180 degree sweep I basically made it into a standard retract servo with the same gear reduction and torque, the ability to set end points and slow the transit for a more scale like action.

The difference with servoless retracts is the motor drive circuitry is all internal and therefore not likely to be affected by external devices.
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Old Jun 04, 2012, 01:27 AM
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Quote:
Originally Posted by pilotpete2 View Post
I'd love to see that video too. I'm more than a bit skeptical, since the ones I've seen do not operate proportionally.
Pete
Video is posted above and there are others on eBay the more I looked. Sure looks pretty darn proportional to me - a constant rate of retract on all I've seen now. If you're meaning a classic definition - "A proportional control system: is a type of linear feedback control system." (Wikipedia / Websters)
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