Retracts.
 

I am planning on Buying a set of Great Planes retracts<.40 sized> for a plane i am scratch building.
http://www2.towerhobbies.com/cgi-bin...?&I=LXUY32&P=0

It says basically the only thing i need to buy is a retract servo. How does this work? Shouldnt i have to buy 2 mof them? Or does the one mount in the center of the fuse and control both? Any info appreciated. Also I am running a 6 channel futaba radio system<6EXA> so which INEXPENSIVE servo will be best for my system. ALso how hard is the installlation of these?
Thanks

RE: Retracts.
 

You use one servo in the center of the wing with control rods running to the retracts. You have to use a retract servo because they have more throw, or travel than a standard servo. There are a number of brands available; try "Servo City". Retract servos are on the expensive side at around $40 is the cheapest I've seen. (But I haven't been looking.)

The hardest part of setting them up is usually getting the geometry of the cntrol rods right, so that the retracts travel to both full down and full up, without the servo binding.
Dennis-

RE: Retracts.
 

Tgis wing is a dual aleron servo wing and the wires conect right in the middle. So what your sayin is i'd have to costom fit a place for a retract servo to?

RE: Retracts.
 

Yes, the retract servo would go in the center of the wing forward of the spar. And you can expect to pay about $60 for any retract servo.

Here's how they work, and how the pushrods are set up:

http://204.96.183.34/RCU/grafx/Retract.gif

RE: Retracts.
 

awesome pics Minn. How do you do it all the time? you must be a web guru.

RE: Retracts.
 

Yea!!! How did you do it?:D

GIF animator??? How did you tween the images? With flash?

Aww mann... Can't GWS give us some cheap retract servos?

OK. Two good Mechanical retracts cost like $40, Retract servo $60, taht's 100.

OK. Two good Robart Pneumatic gears cost like i dunno, Robart Pneumatic kit costs $30.

RE: Retracts.
 

No such thing as cheap retract servos. They have to be very strong to lift that wheel up, there isn't much leverage there, and they move slower that a regular servo to give them even more torque, plus it makes the gear look more realistic.

I used to work as a machinist. Back then I designed my own retracts that incorporated an over-center spring. When properly adjusted, there was hardly any strength required to raise or lower them, and they work easily with a standard servo. Alas, I no longer have access to my CNC machine, and I only have two sets left (they were so popluar I sold them faster than I could make them), and I won't part with either one! :D

PS As far as the graphics go... Yea, I'm a guru :)

RE: Retracts.
 

MinnFlyer,

Is there a way to "tighten" up the slop in mechanical retracts? Installing my first retracts, a set of Hobbico main gear and have major play in the down and locked postion. Seems to be way more than would be prudent.

Followed most fo the posts and my throws seem to be right on. Teh servo is full locked with no binding but man do they wiggle.

Any advice would be appreciated.

GrumpE

RE: Retracts.
 

Unfortnately... the Hobbico retracts "aren't the best on the market." They don't have the adjustments to get all of the slop out.

For a few $$ more... (about $65 instead of $40) you can get the Dave Brown retracts, which are stronger and are easier to adjust. (and just a tiny bit lighter...)

There are better than the Dave Brown retracts... noteably the Robarts which are more expensive... heavier too.

Best "bang for the buck" seems to be the Dave Brown for .40 to light .60 size models. (up to 15 pounds by the instructions... more like up to 12 lbs for the average pilot if you don't want a minor bounce to mean a lot of retract readjusting.)

I have an ancient set of Carl Goldberg retracts meant for up to 7 lb (right... put more than 5 on and you were in trouble...) models. They use the over-center spring and can be operated (all 3 retracts at once) by one HS-81 servo.

RE: Retracts.
 

I guess you get what you pay for?![:o]

BUT, I only paid $18;)

I think I may have come up with a solution last night. With a shim made out of the included plastic for covering the wheel wells I seem to have it licked. I would estimate the shim is about 1/64 or less but makes the whole gear lock tight with very little play. I also doubt it will affect the servo at all as it does not touch until well past the servo arm throw. Hope to hook up the whole thing this evening and try it out. Keeping my fingers crossed.

GrumpE

RE: Retracts.
 

I'm not familliar with that brand, the only ones I use are my own design that I machined myself.

But if that idea doesn't hold up, you could drill and tap the casing to accept a set screw which you could use to adjust the play.

RE: Retracts.
 

Thought of that too. If the shim and set screw do not fix it I can take the set apart and replace the end block piece with another of my own twisted ideas. :)

For the price still not a bad deal. Can easily tap in the set screw to try it.

Thanks!

GrumpE

RE: Retracts.
 

OK, got a break from work and went up to check them again.

Feeling VERY silly.:eek:

Sure enough, there is a set screw.

Thanks for suffering the nube.:)

GrumpE

RE: Retracts.
 

What about the B&D Pneumatic Retracts Tricycle at Tower for $75?
I would buy this one for the Tucano I just bought, but nobody ever suggest this kit. Is this a bad quality one?

Nilo

RE: Retracts.
 

By the way, this is included for this kit.
Two Pressure lines (53"ea)
One Air Tank (5"x1-1/2")
Mounting Screws (16)
One Flow control valve
One Air tank fill valve
Three Tee fittings
Three 9" Struts
Two Main Retract Units
Two Disconnect Couplers
One Nosegear Retract
One Instruction Sheet


Nilo