I am setting up trainer with 3 rd line for throttle so I can slow down for beginners

with a 3 line setup if I set the throttle for reduced speed , can the 3rd be left in that

position and only fly on the normal 2 lines for up and down ? What I have in mind is

to make a handle, like this crude sketch, with a slider on top of the handle to the 3rd

line , telling beginner not to alter it , the handle design also allows me to give / take

bake the handle during flight, looking for new ideas please. Thanks in advance

Vincent

Not a bad idea, I have used a throttle controlled plane to teach few folks but if just teaching is what you are looking for, another option is to use a shut-off. That way if the student gets dizzy you can just end the flight. I have found that this works better for primary instruction. Brodak makes a good one that I think is on sale at S&S.  For a simple throttle handle and bellcrank, I'd just contact Joe Just for his system. It's already proven and inexpensive. 

What you propose is quite do-able.  One caution that I would add is that in the sketch you drew, note that rocking the handle forward or back changes the position of the throttle line w/respect to the elevation lines, so there MIGHT be some coupling of elevator control -> throttle.  The real effects of this would depend on the total control system geometry, of course and in most cases probably wouldn't amount to much.  You can remove this effect by figuring out some way to make the throttle line exit the handle between the elevator lines.

I take it that you consider it beneficial for YOU to be able to throttle back after take-off and then give the handle to the beginner.  If all you want is to be able to knock some RPM off the engine before take-off, then just locking down the throttle push rod would give you that ability.

Thank you friends, I have it sorted now, will proceed with this version
Pictures show throttle open and  closed, I can operate this with my
left hand and the throttle will maintain its setting as the pivot is locked
with star washers , takes more effort than the line pull to move it
My normal teaching is to take off stabilise the plane , have the student
follow my rigid arm , then take the handle , in the beginning I stay and
mirror his arm with mine until he is settled, I squat for maybe 6 laps and
then take back the handle to prevent him/her getting dizzy and repeat
that until we have had enough for that session , then I can cut the throttle
and land the plane, I get many beginners and setting up sessions is difficult
because of prolonged bad weather, I want to have an ideal setup

Vincent