Meesh

My Feedback: (135)

Here is my problem. Throttle linkage goes thru the firewall and is encased in a tube. You have to drill a hole to glue the tube in the firewall. I'm installing a 4-stroke which puts the carb very near the firewall. When the carb opens or closes the throttle arm swings an arc which causes the linkage to raise up and down as the arm swings thru the arc. Because the carb is so close to the firwall there isn't much room to let the linkage bend (flex) so binding occurs and puts extra strain on the servo.

I'm currently installing a Saito 150 in a Sig Rascal 110.

How do you guys get around this problem???

Thanks All!

Edwin

My Feedback: (2)

Very good combo. I used a saito 120 inverted in mine. When the thickness of the firewall mount was included in the distance, I didnt have any problems. The throttle cable was 1/32 piano wire with a Z bend at the carb end. Gave it enough flexibility to bend as needed. I set the output of the cable to be at the midpoint of the carb lever and used about a 1/8" dia tube to let it flex. On my latest plane I used standed metal cable. Seems to be working good so far. No binding to speak of.

FYI- a guy in one of my clubs has this combo and it would hover for a few seconds. Didnt look right, but was neat to watch. Mine wouldnt hover but had plenty of power. Knife edge is just plain beautiful.
Edwin

waagbuck

My Feedback: (1)

I think this must be a common problem with four-strokes. I ran into this installing an os 120 on a goldberg ultimate bipe. Dubro makes a little pivot arm device that may solve the problem. On the ultimate, I sent the pushrod out past the throttle linkage to a 180 degree turn, then back to connect. It works fine. If you search around, you might find some photographs or drawings that might help you visualize the solution.

Meesh

My Feedback: (135)

Thanks Edwin!

Waagbuck,
Sig recommends doing that on the Rascal .40. I thought maybe there was a better way.

Bob

BigBird1

My Feedback: (4)

Slot the firewall for the up and down motion of the push rod sleeve, drop back about an inch or so on the inside of the fuse behind the firewall..install a balsa piece from the fuse side to the push rod sleeve and glue the sleeve to it...should take care of it..
That short of a distance with just the rod sticking out of the sleeve to the carb, their will be no undue flexing..
I had to do that on all my 4strokes...when I had some..

yak_54

replace your push rod with a longer one, run it out a couple inches past your throttle arm and put a 180 degree bend in it back to the throttle arm from the front. the extra length will give you enough flex in the wire to prevent it from binding.

Sprink

I either do the 180 degree bend method as mentioned above,

or i use a direct push rod from the servo to the throttle arm without any sleving, and a bigger hole in the firewall to allow for the movement.

or I mount the throttle servo on the firewall.

Richard L.

My Feedback: (24)

Here is the Dubro 4-stroke throttle linkage:



It works pretty good. I tried the 180 degree bend trick, but the push rod had too much flex in it. Plus, the throttle arm didn't move smoothly because the distance between the hole on the arm and the pushrod changed as the arm moved from half throttle to full throttle or half throttle to idle.

4*60

My Feedback: (41)

Dubro

http://www.whitetyphoon.com/rc/kyosho_corsair/pic04.jpg