ORIGINAL: speedracerntrixie
ORIGINAL: DaleD
ORIGINAL: w8ye
This image was originally posted by JediJody
I think this is one of the best piece of informtion available to someone who is new to gas engines. I have been able to set up and operate my gas engines without the need for throttle curve by using this geometry.
DaleD
Dale. I have always questioned the use of this chart. IMO when one sets up this way you will have close to full RPM by the time you hit half stick. My question for you is if you are running at full stick and back off just a tad do you see an RPM decrease? I have always set up my gassers so that the throttle servo has equal travel above and below 1/2 stick. Then I set the pushrod length so that at half stick the carb butterfly is approx 1/2 open. Any other adjustments are easily accomplished with a throttle curve on the TX. The goal is to slow the application of throttle from 1/2 to full in order to sperad out the throttle response over the whole stick movement. I think the chart defeats this. The benifit I do see with the chart is that the power comes off idle slowly and that can be of use for a newbie but it wrecks the rest of the throttle curve.
First, it needs to be noted this chart is promoted by somebody that has likely forgotten more than I'll ever know, as well as many other well seasoned expert flyers. Second, the fact our gassers are pretty much "all in"/developing 100% available power by time the butterfly is half open also need to be acknowledged. That diagram even helps illustrate that by the fact the carb arm is not moving through a full 90 degree arc? It's only moving through 65 degrees. The fact this works fine is not hard to back up. Some time spent on a test stand with a tach should verify it pretty easily. There's nothing going on through that last 1/3 or so of the throttle arms travel.
So, if the carb's arm is set up to move through a 45 degree arc on the bottom half of the sticks movement (like a nitro engine might be set up, 1/2 travel below, 1/2 travel above) you end up with better that 2/3 of the gas carbs usefull travel below half stick (45 degrees vs. the diagram's 21 degrees), thus making the throttle very (too) sensitive below half stick. Granted, that can be straightened out using your radio in many cases, but I think the point here, is that set up as that set up per the diagram, there's either no or little need to do that. It is obviously a matter of personal taste, but that chart's setup is a pretty good plan....