ok, I know this can be done. I bet you guy if we knock our heads together we could develope a good set of indoor retracts for small, four oz models. IT would use a hs sixty or 55. It would go on a small warbird to make it look really scale.

any Ideas?????

How about this:

1. Mount your servo so that the plane of rotation is perpendicular to the ground.
2. Mount a piece of brass tubing to the control arm.
3. Bend a piece of music wire (that will slide through the tubing) to an "L" shape.
4. Solder a washer to the music wire allowing enough room for a small spring (like the ones in ink pens but stiffer)to compress between the washer and the tubing.
5. Slide this through the tubing and cap it with a wheel collar or another washer.

The servo may not last long and you might have to control the amount of throw (easy to do with a programmable radio).

Bob Fox

is that proven??

You didn't ask for proven, you asked for ideas. That was the first thing that popped into my head.

HS-55 servos are rated at 15.27 oz. in. of torque. Torque = Radius X Force. In theory, a 4 oz. plane could gently land on 1 wheel if the ground surface of the wheel was no more than 3.8175 in. from the axis of the servo. For a 2 point landing, your plane could weigh 8 oz., 3 point landing 12 oz., or you could vary landing gear length, etc. To be accurate you would want to account for all the forces that are occuring (gravity, momentum, etc.). Hopefully the spring would absorb some of the shock of the landing.

I would bet that a servo is going to fail at some point (most likely during a hard landing).

I hope that helps.

Bob Fox

Such retracts do exist. The german Company K&K sells them. They have a mass of 3 g and they're compatible with the small Herr warbirds. Don't have have a clue woh's the manufacturer, but I thought they were US made.

Achim

Achim,

Do you know if K&K have a address,phone or web site and what they might be?

Hello Paul. My landing gear retracts with almost alarming regularity upon landing Best Regards

[This message has been edited by Bleriot (edited 07-27-2001).]

A spring loaded one-way landing gear should be light and easy to fabricate: latched up, released by a stab of down elevator or an extra servo, a spring could extend the gear at landing. 1/16" or smaller wire strut with a 90° bend at the top, rotating in a brass tube hinge, internal spring pulling a cf thread, struts would benefit from a locking latch. Got me mind-sketching now...

Not exactly scale operating, but you could fly clean after a hand launch and land on the wheels (protecting the prop as well!)

Originally posted by Bleriot:
My landing gear retracts with almost alarming regularity upon landing Best Regards

Mine does not retract they sort of eject......LOL that is what we all need ejectable landing gear

Lynn

There will be an article in an upcoming issue of Model Airplane News on an indoor Hawker Hurricane with home made carbon fibre retracts. It will operate on an HS-50 servo but its still a few months away.

down- http://www.freepicturehosting.com/g/90055_1.jpg


up-

http://www.freepicturehosting.com/g/90055_2.jpg



[This message has been edited by Buddly6 (edited 07-27-2001).]

That will work, but you will need to make your linkage from the servo to the landing gear very stiff. The longer the linkage is, the more easily it will flex under a load. Maybe, if the linkage traveled in a guide that was fastened to the wing, it would be rigid enough.

Bob Fox

I think were getting somewhere. I agree, along the line there has to be some tube or something to hold it down. and realize, these ARE very basic Paint plans. ANyone else want to post an idea, created in Paint (tm). I would use carbon fibre in that setup. carbon fiber landing gear, and pushrods. the setup is the same on both sides.

Laser cutting the mounts and swing arms would be easy enough. The extra weight concerns me though. The spars would have to be beefed up, maybe a fore and aft laser cut plywood trunion plates could serve as a piviot point and a spar stiffener. Then you could use a short C.F. tube as the piviot. Lace a C.F. gear leg to that and use laser horns and collars to hold it all together. As far as push rods go the lightest would be a pull-pull system with kevlar thread.

Just some thoughts...
Chris @ Anything R/C

Chris,

K&K does have a website, but it's almost useless, at least you will get the contact information:
http://home.t-online.de/home/kk-modellbau/

There was an article about a plane with these retracts in some german mag. I could scan it and send it to you. If I'm able to locate the magazine

Achim