Quick and Easy Retracts

Oct 29, 2009 No Comments by

By George Jenkins

If you’ve ever struggled to install mechanical retracts, your no-nonsense solution is here—electric retracts. If you have had a hard time getting your mechanical retracts to lock up or down or if you’ve ever had a gear failure or watched your warbird swaying back and forth while just sitting on the runway, check out Lado’s all aircraft 6061 aluminum CNC 180-degree retracts.

This gear was specifically designed to replace the retracts in the Hangar 9 P-40, Corsair or Hellcat. However, at the time of this article, these three warbirds from Hangar 9 were nowhere to be found, so one of the guys in the Sarasota R/C squadron,
Wallis Hampson, had a Goodwill Hellcat he loaned me for the article. The holes in this electric gear matched the mounting holes in all three planes.

Installation

If you cut out one piece of plywood with a Zona saw and fiber-cutting wheel with a Dremel tool, you can install this .40-size electric 180-degree turning gear. Looking at the picture, it’s easy to see how really simple the installation turns out to be. After removing some balsa from the factory leg clearance slot, I placed the retracts on the flat plywood retract mount and used 4-4 x ½ inch socket head metal screws after drilling the pilot holes and running some thin CA in the holes.

Once you have the gear in place, drop the wheel that came with the kit into the dead center of the hole and then measure from the top of the gear collar to the hold in the wheel and then add 7/8 inches to that measurement. It you have some 5/32-inch wire laying around, you can bend a 90-degree angle on the gear with axle long enough to allow two 5/32 wheel collars on either side of the wheel. Make sure to file flat on the wire for the Allen screws to set on the wheel collars and make the blue lock tight again. 

            Now cycle your gear into the hole in the wing and check the clearances. Don’t install the gear too close with those tolerances here; it can cause you heartache if you happen to make a hard landing and bend the gear leg. I used a straight gear leg, but you could use one with a shock-absorbing loop in it.

Plug ’em in!

That’s it, the retracts are in! The servo connector comes out of the back of the unit and simply plugs into a Y-harness that then plugs into your retract channel on your receiver. I used a servo driver/tester from Vexa to run the gear up and down. You could however, hook it up to your receiver and also cycle it that way. Make sure that your servo travel limit is set at 100% to activate the gear.   

Scale-like speed

Retract speed is 9 seconds on 4.8 and 7 seconds on 6 volts. Yes, the gear runs off the 4.8 (0.05) or 6 volt (0.8) receiver battery just like any other servo. After all, it is just a servo-motor running a jackscrew to bring the gear up and down. This makes for a positive lock up and down. Don’t worry, it won’t run your battery down and make you crash. It pulls no more amps than any other servo. However, there is a fully stalled motor detection circuit that turns off the gear if it gets hung up, so it will not burn up the drive motor or drain your battery. I recommend you use 6 volts and a NiMH battery pack of 1600mAh or better. 

Gear legs

Once it’s in the down position, you can use the 5/32-inch wire gear that comes in the kit as the landing legs. The wire gear goes about 7/8 inches into the gear unit and is held in place by two Allen screws. It’s important that once you get the gear lined up with wing, that you file a flat on the wire for both Allen screws and use blue Loctite on the treads.  Make sure there is a little toe-in on the wheels by standing directly over the wheel and lining then about 1 degree in. This will make your warbird track true and help slow it down on touchdown.

How it works

The gear is rotated 180 degrees by a clever bevel gear that follows a gear pattern CNC machined into the 6061 aluminum gear frame and since it is an all-metal gear box. This makes for a very simple, clean and reliable system. A servo motor drives the jackscrew for power.

Already my favorite!

I used the electric retract conversion of a set Robart retracts from Lado for the T-28 in a previous issue and they have perfomed flawlessly. 

The new retracts are priced at $190 and are available via lado-tech.com or by calling (530) 553-4444.

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