pull pull on throttle
 

http://members.cox.net/bdfelice/Pull-pull/pull-pull.htm

Almost at the end of this page there is a setup for a throttle pull pull using a spring. What are the advantages of this setup? I have never seen this before. It seems like it might be good if you had a less than direct path to the carb, you could turn a corn pretty easy.

RE: pull pull on throttle
 

I took a look at the setup and I believe that with the spring setup if you should ever loose connection between the servo and throttle, the spring will probably return the throttle to idle or close completely.

RE: pull pull on throttle
 

Hmmm...good point....

wonder if the AMA would consider that an approved fail safe?

RE: pull pull on throttle
 

I saw that setup too, and I can't help thinking, "Why would you want to put a constant stress/Battery drain on your throttle servo?"

RE: pull pull on throttle
 

Ditto!

RE: pull pull on throttle
 

That's why I Like you Mike, you always think in the real world.

RE: pull pull on throttle
 

Well...darn...I didn't think of that!

RE: pull pull on throttle
 

Then why is my sky Paisley????

RE: pull pull on throttle
 

Why? isn't it?

RE: pull pull on throttle
 

Ok, guys, what about the pull-pull on the ailerons? With all the advantages of the pull pull listed in the article (ease of install, light, more flutter resistant, etc) why isnt the pull pull system used more?

I have one installed in the rudder of a 40sized 3D plane, but thats about the only time I have seen them used in a 40-90 sized plane.

Also, what about the extreme angles he has setup on the elevator install? It seems that a pull pull with a 45 degree angle in the cable would cause some unwanted friction.

RE: pull pull on throttle
 

Minn Flyer wrote: I have used a similar system with great success for several years. The trick is to choose the spring carefully. It should be weak enough not to cause the servo motor to operate and strong enough to close the throttle if the pulling wire is released.

/Red B.

RE: pull pull on throttle
 

I have seen this done as a mechanical failsafe on the throttle for PPM receivers.
THe trick is to have a low mass servo (coreless) and no binding so that a low tention spring can be used.
Putting a 8 oz load on a 42 oz servo is a low current drain solution.

RE: pull pull on throttle
 

To answer several questions...

First, I really don't see how anyone can say that a pull pull system is easier.

Lighter? Maybe, but by how much? I think the difference is negligible.

More flutter resistant? Possibly.

Failsafe on throttle? Yes, but with considerable more trouble than a pushrod (Finding the right spring - using a much more expensive throttle servo - needing to find an anchor point for the spring, etc.)

The biggest advantage I see is that a pushrod (When it's pushing) can bend. A pull pull system completely eliminates that.

So while each of these items has some merit, I think it is up to the individual to determine how much time and money he wants to spend tinkering.

Personally, I'd rather fly - But that's just me.