Throttle linkage help
 

Hi Everyone.

I need some help setting up the throttle linkage to a Homelite 30cc. I have a twister manifold so I'm able to run a straight pushrod to the carb throttle shaft. The problem is I can't get a completely linear throttle curve. I can set it up so that full throttle is at 1/2 stick or I can set it up so that idle is just less than 1/2 stick and full throttle is full stick. I just can't seem to get it so that full stick travel = full throttle travel. I'm using the middle hole on the servo arm. Any tricks or tips?
Thanks

RE: Throttle linkage help
 

You could try using the exponential feature of your radio. On my Futaba 9C I just dial in a negative amount until I get the response I need. I usually don't fool with the curve mix.

RE: Throttle linkage help
 

maybe an adapter to the carb throttle shaft. I have solder an arm onto a wheel collar and used it in place of the one crimped onto the throttle shaft. From your description an arm twice as long might give better travel limits.

RE: Throttle linkage help
 

Thanks guys.

I haven't tried much exponential, but I have played around a little with the end point adjustment and it's better. I'll see what I can do with the throttle arm next. I'm a little leary tho of soldering anything on.

RE: Throttle linkage help
 

If you have the end points set and the engine idles nice and you get maximum top end then you need to either setup a curve or use expo. Expo would be my first choice. I have this issue on a Balsa USA Eindecker. Dialed in about -45% expo on my 9C and everything worked well.

RE: Throttle linkage help
 

Tym: Try some of this to practice your soldering.
http://www.radioshack.com/product/in...&tab=techSpecs

Material is cheap and if you decided your soldering past muster with a supply of wheel collars you could be in the carb arm business!

If you try it, use a nylon clevis to attach to the copper or scrap file the copper to avoid metal to metal.

RE: Throttle linkage help
 

Not worried about my ability to solder. Been doing it since I was 12 yrs old (I'm 54 now). Even took a tech school electronics course and they taught me how to solder better. What I would be concerned about is using solder as the only mechanical link to 2 critical parts. I was always taught that solder is just a way to ensure the mechanical connection doesn't come apart.

Next time I firer 'er up I'll try dialing in some more expo. It's not too bad now, just that I'm used to glow engines that respond fairly linearly. I'm also considering drilling a new hole for the ball joint post.

thanks for all your helpful input.

RE: Throttle linkage help
 

there you go . drill a new hole in the carb arm but, match the distance from the servo arm .
if the distance from the pivot point on the servo arm to the hole you are useing is half inch then
drill a new hole half an inch from the center of the pivot point on the carb arm .viola! linear travel!
as long as they "clock" the same or close it shouldnt be a problem.

RE: Throttle linkage help
 

On my Homelite 30 I get along better if the throttle is not so sensitive down near idle, Otherwise, I'm too much or not enough throttle on final approach.

Jim

RE: Throttle linkage help
 

I like longer arms on the carb. My servos and radio will allow 120 of more degrees of rotation, most of my Walbro carb's throttle shafts rotate less than 90 degrees maybe 75 degrees. With equal length control and servo arms I can not use more than about (75/140) 53% of my radio's adjustment ability. If I use a short, say 1/2" servo arm and a 1"+ arm on the carb I seem to have much more adjustment on the radio.

Good point. I'll consider drilling a couple of holes thru arm into collar and putting a couple of pins. Vibration more than to shear loading on solder joint.

RE: Throttle linkage help
 

I like longer arms on the carb. My servos and radio will allow 120 of more degrees of rotation, most of my Walbro carb's throttle shafts rotate less than 90 degrees maybe 75 degrees. With equal length control and servo arms I can not use more than about (75/140) 53% of my radio's adjustment ability. If I use a short, say 1/2" servo arm and a 1"+ arm on the carb I seem to have much more adjustment on the radio.

Good point. I'll consider drilling a couple of holes thru arm into collar and putting a couple of pins. Vibration more than to shear loading on solder joint.