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retracts

Old 07-31-2009, 03:13 PM
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weldercde
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Default retracts

I just bought my first warbird. can i use regular servos on my retracts or do i use special servos thanks
Old 07-31-2009, 03:23 PM
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F4u5
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Default RE: retracts

Typically, you will need a 180 degree retract hi torque servo. I have used 1/4 scale sevos on smaller planes, but I would go with a retract servo.

Jeff
Old 07-31-2009, 09:08 PM
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DavidAgar
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Default RE: retracts

If you are using mechanical retracts then yes you do need a retract servo. If you have air pressure retracts and are asking about operating the air valve, then you can use a standard servo. Good Luck, Dave
Old 07-31-2009, 09:49 PM
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F4u5
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Default RE: retracts

Good point Dave....I assumed mechanical.[&:]

Jeff
Old 08-01-2009, 07:33 AM
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weldercde
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Default RE: retracts

which is the best retacts for a 120 size bird
Old 08-01-2009, 07:50 AM
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Sandmann_AU
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Default RE: retracts

Assuming mechanical retracts, you can use a standard high torque servo but you shouldn't. Normal servos have slightly less than 180 degrees of rotation, retract servos have slightly more. Mechanical retracts need that extra so they get full travel and lock the gear into place without the servo trying to move past its end stops. Retract servos also only have two positions, they're not proportional so they only travel from one end stop to the other and back (which is why they're also called "bang bang servos"). This works better with a radio's retract switch, since they sometimes don't have adjustable end points on that channel. Besides all that, by the time you buy a standard servo with enough torque to guarantee that the retracts won't overload the servo you might as well buy a retract one.
Old 08-01-2009, 07:53 AM
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Craig-RCU
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Default RE: retracts

ORIGINAL: weldercde

I just bought my first warbird. can i use regular servos on my retracts or do i use special servos thanks
Assuming that you are talking about mechanical retracts, it really depends on the warbird. What warbird did you buy? In general, I'd say trust the instructions. If not, you can install standard servos to see if it works. Maybe one standard servo for each gear could work to replace a single high torque retract servo meant to operate both gear. As long as the standard servo has enough torque and travel to move the retracts to their locked position (both up and down) it should be fine.

Of my warbirds that have mechanical retracts, my Hanger9 Corsair instructions called for a single high torque retract servo and it definitely needed it especially after I added Robostruts and Robart wheels. Those rotating retracts take a lot of force to move. My World Models Zero 60 instructions called for a single standard servo to move both gear and that would have been enough to operate them because the stock gear is shorter than scale length and the the stock wheels are smaller than scale, light weight, foam. However, when I lengthened the gear to the proper scale length by adding Robostruts and adding larger wheels that were also heavier, I found that a single standard servo wouldn't retract the heavier setup. So, I used two standard servos instead (a single standard servo for each retract) and that has worked great.
Old 05-24-2011, 06:45 AM
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Default RE: retracts

hi. would a JR 791 work with the stock setup? i got the hitec hs 75-bb and it burned out before taking off... such a dillemma.
Old 05-24-2011, 07:45 AM
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Edwin
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Default RE: retracts

I use the JR791 on my H9 P-40 and Hellcat. Tried the hitec plastic gear hs75 and it just kept stripping the gears. Never new when it would work. The JR791 is metal geared and lots more torque. But I think in the future I will be using the eflight electrics. I have them on my H9 B-25 and they seem to hold up pretty good. Not been in the air yet but during ground run ups they hold up fine.
Edwin
Old 05-24-2011, 09:22 AM
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Default RE: retracts

the best retract request is a can of worms, want it simple? euorkits, never fail, cheap as chips, want the best? well, jurys out on that one, it depends on what you want to spend, if mechanicals are what you are after, then it would be favorable to fit a 2nd battery pack for the retracts servo, and modify a Y lead for them. if the legs stall going into the well, then the single battery pack will drain quicker than you can say, IVE LOST IT, there will be those that detract from this, but in 40 years experiance, i heard the detractors, and seen the same picking the bits up,
Old 05-24-2011, 10:26 AM
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vertical grimmace
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Default RE: retracts

I do not like the design of the Eflite retracts. I would only use them for electrics. The little limit switch does not like engine vibration.
Old 05-24-2011, 02:26 PM
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rc34074
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Default RE: retracts

The better retracts would be:
For air operated use either Spring Air or the Robarts that are air up/spring down, and use the version that takes 7/16 oleo struts directly into a hole in the retract body.

For electric use the magnum rc electric, which are now made in France I believe. These were originally the Lado electric retracts. If you can get oleos to fit them I would also get 7/16 Robart oleos.

But if you can get them to fit your plane the very best are made by Sierra Giant Scale in Ohio. They cost more but are very well made. Sierra retracts usally come with oleo struts included.

Good Luck

Ed
Old 05-25-2011, 01:22 AM
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Tumalik
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Default RE: retracts

Thanks guys. JR 791 should do the job for now as i am within the 60 size class. My only concern at this point is if the retracts can handle the weight of my zero? i'll be preparing her tonight for her maiden tomorrow. Thinking of shifting my battery to the firewall to level her out, rather than adding another 120 grams.... 
Wish me luck!
Taimoor
Old 05-25-2011, 04:36 AM
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aghost
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Default RE: retracts

Good luck Tumalik. Be sure to only use that servo with a 4 cell (4.8V) battery. A 6V or higher battery will burn it out.

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