Two questions, retracts and bellcranks

[Matt Brown]

Apparently I had a bit rougher landing than I realized last weekend. On my next flight the gear on my SV11 stayed on the ground on takeoff. I went ahead and flew out the pattern. While flying I found that I really liked the look of the plane without the gear. So, I’ve been considering my next build with retracts. Pros and cons? I know easy with electric power but could be a real headache with glow power.

Second question, more curiosity than anything. What are the benefits of suspended bellcranks versus mounted on a platform? Foam wings it’s kinda obvious but on a built up wing I’m not seeing any real reasons. I have noticed virtually all designs in the last 20+ years use them.

Thanks, Matt

[Robertc]

I built three nitro planes with retracts using the Jomar retract controller.  Senses the noise of the engine.  No noise, gear comes down.  Don't know if still available.  Cons - more work, adds a little bit of weight, but never was an issue.  Plus - looks cool.

[Ken Culbertson]

For what it is worth, over the 60+ years I have been doing this I have had several conventional mounts fail under extreme conditions.  I have never had a floating BC fail under any conditions and I have been using them since they were introduced to me in the late 60's when I build a lot of I-Beams.

Never used retracts, but I like the idea.

ken

[Avaiojet]

Never tried retracts, but I do only suspended bell cranks.  One caution, do not cut the  rod too close at the top. I did two like that before I realized what I had done. In both cases the rod pulled down and out of the upper ply mount causing both models to self destruct violently. Lesson learned. A small amount sticking above and below the ply mounts, capped with a small square of ply. The wing does flex during maneuvers and can cause the rod to pull out if cut too short. FWIW.

Solder a washer top and bottom.

[Mike Griffin]

Hi Matt,

I am including a link to the You Tube video I did a few years ago showing the suspended bellcrank system that Eric Rule developed when he still owned RSM Distribution.  I used this system in a lot of my models after he came up with it and it works very well.  The only time I ever used a platform mounted bellcrank was on a plane that had a narrow airfoil such as the Ringmaster or Navion.  However I have used suspended bellcranks in Ringmasters.  The benefits of the suspended system are much superior to the platform mounted system.

Here is the link: 

RSM still offers this on their website.

Look under Building Supplies Bellcranks and Hinges.  It is the first item on the menu.

Mike

[Ken Culbertson]

Solder a washer top and bottom.

No solder, just something to keep it from moving.  I put mine through 1/8 plywood on the top and bottom then put a 1/16" cap over it.  I also use a brass tube for the mounting so that I can slip the rod out should I ever need to replace the bellcrank.  Handy during construction.

Ken

[Fred Cronenwett]

The stunt rules allow for 2.4 Ghz to be used in CL stunt for retracts and engine kill (but not throttle). electric retracts plugged into a reciever will operate the retracts on command, with engine kill on on a toggle switch you could toggle the gear down, and then kill engine.

Fred



This shows how 2.4 Ghz is being used in CL Scale, the same transmitter can be used for CL stunt it's just that you can't operate the throttle like CL scale does on a regular basis.