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Old Aug 29, 2014, 07:40 PM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
999 Posts
Help!
Servoless Retract Control

Throwing this out there to see if anyone has a suggestion or even the bits I need.

Have a second T/F AT-6 and in this plane the retracts are a bit unique in that the struts are angled 15 degrees forward from true. Fabricated a set of trunnions for the first kit built to alter the set of Eflite 60-120's you see in the pic.

Although I have several more pairs, access to the machinery to make another set of trunnions is difficult so I picked up a NIB set of Robart #618ROBO's specifically made for the T/F version for a "cannot refuse" price:

http://robart.com/products/top-fligh...s-w-robostruts

The problem is they are pneumatic and I have no support gear or other bits for that setup. Have been playing around with motorized screw jack rigs and have one working the stock Robart slider. Due to the design of the stock Robart housings there is no easy way to fit switches to set end points, so was hoping to go with what I saw in first gen servoless where there was a common module with just the motor drives in each gear. In that case the module watched for the current rise when the motors hit physical end limits and switched off until requested to change direction.

Although I have seen them come up occasionally, have been searching with no success for a set of that type gear and also no luck trying to find a purpose built module for this app.

Anyone have any ideas?
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Last edited by Cougar429; Aug 29, 2014 at 08:26 PM.
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Old Aug 29, 2014, 08:30 PM
We want... Information!
Bruce Abbott's Avatar
Hastings, New Zealand
Joined Jan 2001
5,180 Posts
Quote:
Originally Posted by Cougar429 View Post
Have been playing around with motorized screw jack rigs and have one working the stock Robart slider.
What motor and gearbox did you use? Can you post a picture of your mechanism?

Quote:
In that case the module watched for the current rise when the motors hit physical end limits
For that system to work successfully you need to know the stall current of your motors. Once this been determined, it should be relatively easy to design and build a custom circuit for it.
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Old Aug 29, 2014, 08:38 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,265 Posts
Personally I like pneumatic gear- You can get the support "gear" on this page- http://www3.towerhobbies.com/cgi-bin...SM&C=QEZ&V=ROB

All you need is a pump and the large Robart Large Deluxe Air Control Kit
Robart Large Deluxe Air Control Kit
http://www3.towerhobbies.com/cgi-bin...&I=LXET22&P=SM

Robart 100 PSI Hand Pump & Gauge
http://www3.towerhobbies.com/cgi-bin...&I=LXET26&P=SM
Less expensive than from Robart
As far as the pump goes, a lot of guys use there cordless drill attached to a pump.
Being north of the boarder, and metric savey (unlike myself) Hobby King has some cheaper air gauges, I got mine here: http://www.dreamworksrc.com/catalog/Air-Gauge-Single

I don't know if you've ever seen John Morgans build's , but all he uses are pneumatic gear-- and his planes are huge. And he likes the reliability of air.

OV-10A Bronco........... 96"ws
http://www.rcgroups.com/forums/showthread.php?t=2195377

SB2C Helldiver 100" ws from Jerry Bates plans
http://www.rcgroups.com/forums/showthread.php?t=2033789

F7F Tigercat from Palmer Plans
http://www.rcgroups.com/forums/showthread.php?t=1891222

Sorry if I didn't answer your question, but don't give up yet on the air ones!
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Old Aug 29, 2014, 08:52 PM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
999 Posts
I'm off to bed soon but will try and get a pic up.

I fried the board on one Eflite 60-120, (my own fault) and scavenged the drive motor and screw. Tapped the plastic to the metric pitch to give it a try. Have not anchored it down yet as I want to see if it is possible before investing any more effort.

As for air systems, my friend flies turbines and has lots of experience with pnuematics, so I have at least some chance of getting it right. In this case, as with the first AT-6, I wanted to use a multi servo plug to simplify getting ready to fly at the field. All my servoless are powered with LiFE packs and work fine.
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Old Aug 30, 2014, 06:58 AM
Dave the Rave
dmccormick001's Avatar
Joined Jun 2007
872 Posts
Century Jet Models in Louisville, Kentucky will take a set of air retracts (any brand) and convert them to electric retracts for a nominal price. Their kit will include a nice controller that features current-sensing for the gear motors, as well as options like a delay for the left main, landing lights, and gear door sequencing.
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Old Aug 30, 2014, 07:28 AM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
999 Posts
I was hoping to do the physical work myself. It's the control system I would want to find pre-built and ready to program. Even if I had to adapt the drives from an older system that would be an option that may be more acceptable as at this time as any more modern setup seems to have limit switches.

If correct, a system that worked like the old Krafts might function. To be honest I am unfamiliar with the electronics of this kind of setup.

I love to tinker through the winter, just with work schedule less time to do that than normal.
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Old Yesterday, 11:25 AM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
999 Posts
Sorry, got stuck fixing some stuff in the kitchen so distracted for a bit.

Here are some pics of the simple installation so far. Mounting the drive should not be a problem and in fact may not be the final iteration as I believe there are screw drives available, (if I can find them again).
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Old Yesterday, 07:33 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,323 Posts
The version of these that are Rx ready should be able to respond to a specific amount of commanded travel and stop where you want them to.

Is anything there small enough?

http://www.firgelli.com/products.php?id=41

They are not cheap.
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Old Yesterday, 09:18 PM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
999 Posts
The 30mm L12-R looks like it has the required stroke. However, physically it would be far too long to fit the wing pocket.
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