GP Ultimate Throttle Linkage
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GP Ultimate Throttle Linkage
I am currently trying to finish a GP Ultimate Bipe and have hit a snag with the throttle linkage. I am using the Saito 72 for power and the engine is mounted with the cylinder head to the right side of the fuse. This puts the throttle linkage on the top and very close to the cowling. I think I am just low enough for it to clear, but I am having trouble with the alignment of the push rod from the carb to the servo.
After several attempts with the supplied metal push rod, I abandoned it and tried the Golden Rod plastic push rod system. This allowed the engine end just enough room between the throttle arm and firewall to achieve full throw. Now the push rod goes from the top of the firewall to just under the middle of the fuse to connect to the servo. The problem is there is not enough flex in the push rod to make the bends around the tank and then down to the servo and be in a straight line to the servo. This causes the servo to bind slightly and a slight buzz is heard from the servo.
Has anybody accomplished this successfuly in this combo? If you have please tell me the secret. I would like to fly this plane before I become too old to walk!
After several attempts with the supplied metal push rod, I abandoned it and tried the Golden Rod plastic push rod system. This allowed the engine end just enough room between the throttle arm and firewall to achieve full throw. Now the push rod goes from the top of the firewall to just under the middle of the fuse to connect to the servo. The problem is there is not enough flex in the push rod to make the bends around the tank and then down to the servo and be in a straight line to the servo. This causes the servo to bind slightly and a slight buzz is heard from the servo.
Has anybody accomplished this successfuly in this combo? If you have please tell me the secret. I would like to fly this plane before I become too old to walk!
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RE: GP Ultimate Throttle Linkage
A lot of people have routed the pushrod so that is moves smoothly and used a "U" bend at the throttle arm to make the connection. You run the wire link past the throttle arm and then bend it back so that it engages the throttle arm from the front. If you have room to clear the cylinder, this will work very nicely. Just make sure that the "U" bend doesn't get near the prop when the pushrod's fully forward.
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RE: GP Ultimate Throttle Linkage
Thanks Bax,
I think I know what you mean. I will look at it when I get home and see if it will work. I have very limited space between the top of the engine and the cowling. I will try and post some pics tonight.
I think I know what you mean. I will look at it when I get home and see if it will work. I have very limited space between the top of the engine and the cowling. I will try and post some pics tonight.
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RE: GP Ultimate Throttle Linkage
I am building the same plane but I chose the option for the 2 stroke throttle installation. The reason being is the OS 70 has
a reversible carb ie allowing the throttle tube to be placed under the engine instead of between the cowl and engine. I would
think the Saito has that option as well and could simply be turned to move the throttle arm to the other side of the engine.
I have a Saito 80 that allows for this and I have run it both ways with no difference detected in running or reliability. It
will involve some extra work but in the long run may be more beneficial. I agree with Bax on the throttle hook-up after it
comes out of the firewall. That method seems to be the simplest.
Another method I have used on 4 strokes is to use either some 1/16 " music or welding wire and make an "L" bend in the
appropriate location and leave the "L" part long enough to go all the way through the throttle arm on the carb. No "Z" bend
is required if it is left long enough to allow for the movement of the throttle barrel back and forth but it can be done. You
can also secure the wire with the plastic push on buttons used for quick connectors. Just be sure that the wire doesn't interfere with
the engine case anywhere and it should be fine. I personally have a preferance for the welding wire as it is much softer than the
music wire to bend and shape but still stiff enough to work a throttle reliably. I usually run it through the inner tube of a Sullivan
Gold rod for a conduit.
Hope this gives you an option.
Sam
a reversible carb ie allowing the throttle tube to be placed under the engine instead of between the cowl and engine. I would
think the Saito has that option as well and could simply be turned to move the throttle arm to the other side of the engine.
I have a Saito 80 that allows for this and I have run it both ways with no difference detected in running or reliability. It
will involve some extra work but in the long run may be more beneficial. I agree with Bax on the throttle hook-up after it
comes out of the firewall. That method seems to be the simplest.
Another method I have used on 4 strokes is to use either some 1/16 " music or welding wire and make an "L" bend in the
appropriate location and leave the "L" part long enough to go all the way through the throttle arm on the carb. No "Z" bend
is required if it is left long enough to allow for the movement of the throttle barrel back and forth but it can be done. You
can also secure the wire with the plastic push on buttons used for quick connectors. Just be sure that the wire doesn't interfere with
the engine case anywhere and it should be fine. I personally have a preferance for the welding wire as it is much softer than the
music wire to bend and shape but still stiff enough to work a throttle reliably. I usually run it through the inner tube of a Sullivan
Gold rod for a conduit.
Hope this gives you an option.
Sam
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RE: GP Ultimate Throttle Linkage
SDM,
I will look into that tonight too. I have flipped the carb before, but that puts the link in the middle of the engine mount and right into the fuel tank on the other side of the firewall. I think the idea of the large loop back into the carb will be too close to the cowling to work very well, but I will look at it again. No doubt there is a way to make this work, I just haven't found it yet. Maybe a more flexible cable is the answer.
I will post some pics tonight so you can see what I am up against.
I will look into that tonight too. I have flipped the carb before, but that puts the link in the middle of the engine mount and right into the fuel tank on the other side of the firewall. I think the idea of the large loop back into the carb will be too close to the cowling to work very well, but I will look at it again. No doubt there is a way to make this work, I just haven't found it yet. Maybe a more flexible cable is the answer.
I will post some pics tonight so you can see what I am up against.
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RE: GP Ultimate Throttle Linkage
Here are the pics of the engine and servo end of the current throttle linkage. I had to bend the end of the link at the servo to even get close to a smooth action. The cowling touches the top of the firewall and only has a slight hump in the middle which lines up with the current throttle position. Needless to say, this is not an ideal situation.
After looking at the engine again, I think I will be able to flip the carb and make the link in a more direct line to the servo. I will try that tomorrow as it looks like the weather will not be favorable for flying.
Any other ideas will be welcome.
After looking at the engine again, I think I will be able to flip the carb and make the link in a more direct line to the servo. I will try that tomorrow as it looks like the weather will not be favorable for flying.
Any other ideas will be welcome.
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RE: GP Ultimate Throttle Linkage
Hopefully the pics will come out and be self explanatory. What I am suggesting is you don't necessarily have to come in with the
throttle pushrod right behind the engine. If you move the pushrod off to the side or below the fuel tank you can come over to the
carb throttle arm with a bent wire like shown in the pic. This application is on a Lazy Ace Bipe with a OS 91 and has been
very reliable. The pushrod is a Sullivan Golden Rod with a short piece of wire threaded in and bent. It also allows for the throttle
barrel moving side to side. It may not work in every application but it is simple and has lasted a long time.
Sam
throttle pushrod right behind the engine. If you move the pushrod off to the side or below the fuel tank you can come over to the
carb throttle arm with a bent wire like shown in the pic. This application is on a Lazy Ace Bipe with a OS 91 and has been
very reliable. The pushrod is a Sullivan Golden Rod with a short piece of wire threaded in and bent. It also allows for the throttle
barrel moving side to side. It may not work in every application but it is simple and has lasted a long time.
Sam
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RE: GP Ultimate Throttle Linkage
Thanks SDM,
I think I got it worked out. I flipped the carb over and relocated the push rod tube. It is now almost a straight shot from throttle arm to servo and seems to be working now. I had to bend the ends slightly to allow for the arc in the arms.
Now if I can get the covering on the bottom wing done, it will be ready for a test run and carb adjustment then on to break-in and maybe even getting it off the ground.
This project has taken way longer than I expected due to some medical problems and such so I am very ready to get it done and get started on the next one. I already have three more bought and one ordered. Looks like it will be a working summer!
Thanks again.
I think I got it worked out. I flipped the carb over and relocated the push rod tube. It is now almost a straight shot from throttle arm to servo and seems to be working now. I had to bend the ends slightly to allow for the arc in the arms.
Now if I can get the covering on the bottom wing done, it will be ready for a test run and carb adjustment then on to break-in and maybe even getting it off the ground.
This project has taken way longer than I expected due to some medical problems and such so I am very ready to get it done and get started on the next one. I already have three more bought and one ordered. Looks like it will be a working summer!
Thanks again.