4 Cycle Throttle Setting

I have been playing around with 4 cycles for a couple of years now and have found out that you really cannot adjust the engine speed by messing with the needle valve. They want to run correctly in just one position. So I think that best way to run them is to use the provided throttle and simply dial in the proper rpm. Here are a couple of shots of how I intend to control that on my new Shoestring. I used a DuBro 1/4 scale turnbuckle and removed one end of it and replaced it with a 4-40 bolt and 4-40 clevis with a lock nut. The throttle has full range capability.
Bill
[photo not recovered: 4cyclelinkage1.jpg]
[photo not recovered: 4cyclelinkage2.jpg]

That's a nice, easily adjustable setup.

I've been using the RC carb on an LA 40 the last year for the same reason- easy adjustment of flying speed and props.

Went flying yesterday, the plane was just going too fast. There was a bit of a breeze and the downwind square corners were just not working. Turned the throttle in a couple of turns on the quick link, the speed dropped back to 5.1 sec/lap, and it flew much better.

The weather has cooled of considerably since I last flew, so the motor apparently was making more power. The easiest way to detune it is to just throttle back a bit to get the normal lap time. I guess the thicker, colder air lets the motor make a lot more power but doesn't add proportionately to the drag on the plane, so it speeds up.

>
>The weather has cooled of considerably
>since I last flew, so
>the motor apparently was making
>more power. The easiest
>way to detune it is
>to just throttle back a
>bit to get the normal
>lap time. I guess
>the thicker, colder air lets
>the motor make a lot
>more power but doesn't add
>proportionately to the drag on
>the plane, so it speeds
>up.

The thing we have been talking about all along. Since we overpower the planes to such an extent it is the prop pitch and rpm of the motor that set the lap speed much more than the drag on the airplane. Thus when it cools down the engine will want to run faster and you get faster lap speeds. We do the same thing on our engines by going to a smaller venturi in cooler weather, and a larger ventur (again) in warmer weather. You can also vary the nitro to keep you in a "range" as the weather warms up.

Leonard Neumann

Great idea! Super pictures!
Only one question......
Where does the tank go???
O.K. one more.......
How can I adapt this technique to a full body plane??
Thanks for sharing!!
Wes

Yea, and I was wondering where the tailhook goes.

>Yea, and I was wondering where
>the tailhook goes.
>
>Alan

Wrong event Alan... If I was putting a tailhook on it then I would be using a bigger 4 stroke. Probably a .60 because I can then take 60% of that. Can you imagine a .60 sized profile carrier plane, growling around the circle...
Bill

>Great idea! Super pictures!
>Only one question......
>Where does the tank go???
>O.K. one more.......
>How can I adapt this technique
>to a full body plane??
>
>Thanks for sharing!!
>Wes

The tank will fit below the linkage because the carb is offset quite a bit. As for a full body ship, I plan to build one with an upright engine. I'm not sure how I'll work it in yet, but I can usually figure something out.
Bill

If for some reason the tamk does not fit directly behind the motor and give you enough room for adjustment. You can always use one the RC Ballink or quik link setups where you have your clevis. The ball will mount right to the throttle arm and the you can put the nylon quiklink on in place of the clevis. Lots of RC flyers use this for their throttle linkage becuase the angle can be weird and still get smooth control. It will snap right into place and wok like a charm. This way you can mount your thottle linkage at most any reasonable angle and still get the tank where it needs to be. This is how I was doing it on the YS and it worked well.

DMoon

The guy to ask is Scott Urabe. He had a KA-10 at the Northwest Regionals that had a pull out choke and some sort of needle valve like crank that opened and closed the throttle. I didn't see the actual mechanism, but he said it involved a sort of worm gear. It did allow very fine adjustment to the throttle using a tach. Very nice setup. Pull the choke, start the engine, push the choke in and adjust the throttle.

What about automatic centrifugal throttle?

[photo not recovered: p83.jpg]

[photo not recovered: p84.jpg]

[photo not recovered: p86.jpg]

.... hmmm ... sorry for my dusty 20 years old model ... the cleaning is not my hobby ... as my wife says ...

Here is what the final version looks like. I added a piece of 1/32" brass to make it easier to rotate and a locking piece of music wire. Simply push the wire towards the fuselage, rotate the turnbuckle and release the wire. Should hold everything in place through the flight.
Bill
[photo not recovered: 4cyclelinkage3.jpg]