Retracts

[Tim Wescott]

Lifted from "Active Engine Shutoff (IC)", http://stunthanger.com/smf/index.php?topic=19025.0 -- I didn't want to divert the whole discussion...

While talking to Joe Dill this weekend about his winter SnowBird flight to join the rest of our NW Birdeezzzz' in the wintertime sunny Tucson south lands...

our conversation turned to CLPA fuel shut off concepts...and ended up talking about the retracts that he has planned on his new Harold Price Crusader that he has almost ready for final finishing and paint.

NOT TO KIDDYKNAPPY this post...our conversation then turned to his own retract system.

Seems he is researching a  retract system...that utilized the stunt engine's "noise factor" that once is tripped...allows for about 10 sec. or so to allow for take off before the signal is sent to retract the gear for flight.
Then after the engine quits...the sudden lack of engine noise...then sends a signal that extends the gears for landings?

(This sound like a fairly good and SOUND idea?)
 Does anyone have information on just who, what n' when this system might have  been used in the past?

I remember reading about such a system in Flying Models many moons ago -- I think as an aside in one of the Stunt columns.

Like active engine cutoff, or active engine control, if it was really going to make you a dominant force it'd probably already be in use.

Like active engine cutoff it sounds perfectly technically feasible, although I think a 10 second delay is a bit short.

[Jim Thomerson]

I think such a system was used by the Chinese. As said, an offhand comment somewhere. I wonder if you could hook the retracts to something like a tachometer.  When RPM went to 0, the retracts would work.  Other thing would be a pressure switch actuated by loss of crankcase pressure.  There have been various successful retract systems on stunt airplanes. 

[Steve_Pollock]

Dick Mathis penned an article on retracts in the August '78 Model Aviation.  It's shown in a Chizler, I think.

Steve Pollock

[Tim Wescott]

It does seem to be a bit of a gimmick; at the speeds that a control line PA aircraft flies I don't see the gear making much difference in performance, but you pay a weight and complexity penalty, and I doubt you're going to increase your flying score much just because the wheels are up.

That having been said, it'd be fun.

[Chris McMillin]

Bob Whitely's done it, used on a Rabe Mustang.  He wrote an article about it in Flying Models. Small batt, mechanical retracts with one servo and the little active mic/timer unit made about a 4 oz addition. I can paint that much of a difference. Pretty cool idea, I have a unit that a memeber here gave me, I think I'll use it in my Derringer for N30.
Chris... 

[Wynn Robins]

with electric planes you can now add the digital servoless retracts - easy install - nothing tricky - just plug them into your timer and off you go

[Tim Wescott]

Bob Whitely's done it, used on a Rabe Mustang.  He wrote an article about it in Flying Models. Small batt, mechanical retracts with one servo and the little active mic/timer unit made about a 4 oz addition. I can paint that much of a difference. Pretty cool idea, I have a unit that a memeber here gave me, I think I'll use it in my Derringer for N30.

Any clue of what issue?  I've got a lot of Frying Models mags here...

[Shultzie]

 My old scans from Harold's Crusader article on retracts for old time sake

[M Spencer]

The Drag and weight are most Relephant .
A Typhoon or Spitfire with wheels going AFT retracting
pulls the C.G. aft .
Same with  ' mass concentration ' , Wheels stowed
inboard being preferable . ( like P-51 etc .)

A few pins or over centre catches , with Hairpin Springs
or elastic bands for motion is a light weigt method .

Leg bent so grove in mount is hinge line . Correct location
can take a bit of figureing the angle . the poms called the
hinge , the ' Pintal '. and the gear ' the Chassis ' .

Best to work backwards , Wheel positioned Correct retracted
to define pintal angle/s.

A catch  tripped on half down elevator , and micro switch from
muffler  pressure take of , would be sufficent.

[Jim Thomerson]

The late John Davis had a design called the 'Arrowplane'.  He had one with retracts and one without.  I really liked the way the one with retracts looked in flight.  I think the use of retracts would be great on the scale type airplanes which had them in the 1:1 models. 

[Robertc]

The system that used the sound was by Jomar.  I built three planes using that system and it was bullet proof.
Don't know if they're still in business.  They called it the Ukie Retract Controller if I remember correctly.

[Neville Legg]

Wouldn't a commercial pneumatic system, with a sprung sliding bellcrank to trip the air valve, be the simplest solution? The bellcrank wouldn't have to move to far to operate the valve, maybe a 1/4"! Adjusting the spring tension may take a few flights? Many years ago I made my own pneumatic system using plastic syringes operating a cheap lightweight mechanical set of retracts, it worked well, but that was in an R/C model.

Cheers    Neville

[Mark Scarborough]

e-flighjt now makes electric retracts that are self contained, IOW they are actuated externally by the reciever just like a servo. No pneumatics involved. They look very similar in design to the old Robart retracts.

[Chris McMillin]

The new electric E-Flite retracts are not light. However they are very easy to install and operate.
Chris...

[Paul Walker]

My old scans from Harold's Crusader article on retracts for old time sake

Yes, that's the plane Joe is building. I was in his shop last week and saw those plans, and the plane underconstruction. He had the basic wing done and was getting the structure in place for the retracts. He said he planned on a system to operate it similar to the one RJ used on his Mustang. It senses the sound of the motor.

P Walker

[Robertc]

Found a web site for the retract controller:

http://emsjomar.com/SearchResult.aspx?CategoryID=6

[Shultzie]

e-flighjt now makes electric retracts that are self contained, IOW they are actuated externally by the reciever just like a servo. No pneumatics involved. They look very similar in design to the old Robart retracts.

Always wanted to find a system that was compatible to run my Perry Pumper.
here are photos from one of my earlier posts...(the  AJ roberts system)