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Old Nov 24, 2012, 10:51 PM
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Retractable landing gear for a Bellanca Cruisair


Folks, I'm intending to build up this Guillow r/c model kit I've had for many years. I hope to install retractable landing gear, and this model Bellanca retracts its wheels by swinging them straight back.

I'm looking for suggestions from the group as to how this might be accomplished while not using model landing gear retracts turned 90 degrees and relying on the downlocks to keep the landing gear legs in place. I suspect that any substantial rearward force would break the downlocks. I don't think any of them were meant to take landing loads from that direction, it's like a very heavy side load if the retracts were used conventionally, swinging inwards. If someone knew of how I might modify some retracts for a Corsair or a P-40 so as to defeat the twist, that might be a solution, but again I don't want to overload a downlock.

Thanks very much.
Last edited by PeterH; Nov 24, 2012 at 11:16 PM. Reason: correct spelling
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Old Nov 24, 2012, 11:32 PM
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Übung macht den Meister..
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Maybe use two nose gears and lock the steering?

James
Old Nov 25, 2012, 12:36 PM
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If you have converted any small Guillows kit to electric power successfully you know how important it is to keep the all-up weight down so that model can fly in a scale-like manner without being continuously on the verge of a stall. Consider leaving the gear off, hand launching, and belly landing on grass.
Old Nov 25, 2012, 01:38 PM
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I had to look that one up to see what happens. It seem to be basically like this animation -
Old Nov 25, 2012, 03:40 PM
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Guillow Bellanca Cruisair


This is not a converted freeflight model. Guillow sold a C-170 and the Bellanca as 1/2A scale r/c models, the Bellanca has a 42-inch wingspan. My conversion work is to build it with an electric motor, not a TeeDee.

And that's one nifty animation, too!

Thanks, folks.
Old Nov 25, 2012, 05:04 PM
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I am working in plans for a 1/8 scale Bellanca Cruisemaster and I plan in using E-Flite 15-25 90 degree retracts. I believe they lock pretty good and could replace the trunions with Aluminum ones if needed.
Old Nov 25, 2012, 05:14 PM
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A simple torque tube to each leg and a single servo in the wing root should suffice,
especially if you do an over-center setup for down and locked.

I like this bird - among my favorites!

Geoff
Old Nov 25, 2012, 11:58 PM
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Torque tube


Geoff, let me see if I'm following what you've suggested - - - landing gear strut is attached to a torque tube which has an arm driven by a servo. Down locking is achieved by the geometry of the servo output arm. If it's in line with the drive rod coming from the landing gear control arm, any landing gear rotation loads are passed through the servo to the servo mounts and don't have much effect on the servo gears, the servo case takes the load.

Please speak up if I'm missing the point. Thanks for the suggestion.
Old Nov 26, 2012, 12:07 AM
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While I might be a bit presumptuous to speak for Geoff, I would tend to agree with your thinking. However, may I suggest the servo drive a "tiller" arm that would take any loads transferred by the gear, instead of the servo taking the loads?

It might even be easier to find a more suitable place for the retract servo, as the tiller is not as bulky...

Just thinking out loud!

James
Old Nov 26, 2012, 12:27 PM
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Quote:
Originally Posted by PeterH View Post
This is not a converted freeflight model. Guillow sold a C-170 and the Bellanca as 1/2A scale r/c models, the Bellanca has a 42-inch wingspan. My conversion work is to build it with an electric motor, not a TeeDee.

And that's one nifty animation, too!

Thanks, folks.
Forgot about the Guillows' 1/2A scalers, sorry! The Cruisair is a favorite of mine too.
Last edited by E-Challenged; Nov 27, 2012 at 12:03 PM.
Old Nov 27, 2012, 10:06 AM
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James's suggestion makes sense - for a heavier bird. I think even a mini (not micro) 90° retract servo such as the Waypoint W150MGR will take the load with ease. It weighs under 16 grams, has 52 oz/in torque and will fit in the battery tray shown on the wing center section of your plan. Set it up so it goes 180° while the arm on the torque tube goes 90° (servo arm 1/2 length of torque tube arm) and it'll hold the undercarriage down and up very well! I'd rubber mount it so it has some spring - just in case!

Geoff
Old Nov 27, 2012, 02:04 PM
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More info: I've attached a photo of the undercarriage showing that Eflightray's animation is spot-on. I found my factory drawings (obtained from the Smithsonian Institution) and found the center-to-center of wheels measurement of the full scale bird is 8' 10 5/8". They cant inwards, so the upper dimension would be about 2" less. Since the wheels are on the outside, you'll need to run the torque tube (if you choose to do it that way) through the plywood G 4 rib
Old Nov 27, 2012, 02:17 PM
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For a model this size, the simplest ( and probably close to the lightest) solution would be electric retracts. http://www.pw-rc.com/product_info.ph...oducts_id/2386 They are designed to be used in models like the P40, so the strut can be set to rotate the wheel as the gear retracts. In other words, they were designed to retract straight aft, so the downlocks are engineered for your application. They are 19 gm each, so a pair will cost you about an ounce and a half, which should be more than tolerable, i would think.

Regards,
Jeff
Old Nov 27, 2012, 06:13 PM
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Jeff, the wheels don't rotate on the Bellanca - they hang out in the breeze about halfway, so rotating retracts would have to be modified.

Geoff - spelled the old-fashioned way
Old Nov 27, 2012, 07:47 PM
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Quote:
Originally Posted by jhspring View Post
For a model this size, the simplest ( and probably close to the lightest) solution would be electric retracts. http://www.pw-rc.com/product_info.ph...oducts_id/2386 They are designed to be used in models like the P40, so the strut can be set to rotate the wheel as the gear retracts. In other words, they were designed to retract straight aft, so the downlocks are engineered for your application. They are 19 gm each, so a pair will cost you about an ounce and a half, which should be more than tolerable, i would think.

Regards,
Jeff

I agree but use normal non rotating 90 degree units. The Cruiseair and Cruisemaster have the gear retracting back with about 1/2 the wheel showing....

Denny


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