chadxp1

My Feedback: (2)

How do most setup the throttle (Nitro)? Do you setup a throttle curve to get the engie to idle while at low stick or do you adjust the servo travel end point to get the idle that you want?

Hossfly

I use whatever works depending on which Transmitter I am using. I love analog trims for throttle. Digital throttle trim is just - IMO - strict garbage. It is made to sound good because the mfgers. make it sound good but simply cuts their expense while making the rank and file think they have the latest "must have." [:@]

I want my throttle lever to come full back at a nice idle, then use the rotary trim for cut-off. For me digital is just not enough "absolute". However I am forced into several of the #@&**% things.
With analog I can work with the various servo arms and throttle arm to get what I want to perfection. With digital, it is for me to never get everything just right.
(flame suit on. )

Another point is that weather, humidity, temperature, fuel type (nitro/oil % ) can mess up an existing idle which everyone blames the engine for.

gene6029

chadxp1, I set up my throttle on all my planes so that when the stick is all the way back, im idleing. I use a momentary switch on the transmitter to pull the servo further to cut off the motor. The trim, either analog or didgital, is used for slight adjustments only....Gene

JohnBuckner

My Feedback: (1)

Setting up a curve in your throttle responce (in other words this is reducing the the servos response away from a strict proportional response) is a tool that is used by many helicopter flyers and certain types of 3D flyers but for most of us its is not normally neccessary or commonly used.

The comments above about the older manual rotary pot type of trims versus the current push button electronic type of trim is pretty much moot. This is simply because that type of trim has not been used by any manufacturer for some years now and its certainly not some sort of plot by the manufacturers.

Genes description of how he sets up his throttle and kill switch is what most of us do these days and the Kill switch setup if you select the right switch is far better than the old method of forcing the pilot to take his thumb off the throttle stick and attemting to find the throttle trim. This is fine normally but when the engine needs to be shut down quiickly (and yes this happens) especially near the pits the electroic kill button is far better.

Its for this reason I always make sure my students do properly get their throttle and kill buttons set up and are practiced at using them. By the way I beleve all modern radios do include the kill button feature except possibly some of the toy variety type transmitters.

John

chadxp1

My Feedback: (2)

Yeh, I use to fly nitro heli's so I am familiar with using a curve. I guess I should have asked the question
of which is better. I like the curve because one can set the end points and forget about them, but I dislike the curve
because the throttle may not be linear unless you setup all the curve points correctly. The advantage of using the
the servo limits is you don't need to mess with a curve and the throttle is linear. I'm still not sure what to use. I do know that a
problem with setting the lower limits of the throttle all the way to the bottom limit is the kill switch
will not work because there is no more room mechanically for the throttle arm to close. This is why I ask what is better. I'm using
a spektrum dx8 by the way.

jester_s1

The kill switch works by moving the servo a little more beyond the lower limit you have set in your EPA. My way is to get the engine at a good idle using the EPA with the trim in the middle. That way I can tweak the idle as it changes due to weather using the trim. One other thing I do that hasn't been mentioned yet is I give the servo more throw on the top half of its travel than on the bottom. If you set it up linear you won't actually get a linear throttle response RPM wise. It will be more sensitive on the bottom than on the top because throttle response is exponential, not linear. Pilots who just set it and forget it won't care, but I do work the throttle a bit during maneuvers. My 40-60 size glow engines do well with about 50% more travel at the top than the bottom, so a typical end point adjustment would be 80% on the top and 55-60% on the bottom for me. At mid stick, that puts the servo arm 10-15 degrees pointed away from the carb when a straight linear setup would have it at a perfect 90.

JohnBuckner

My Feedback: (1)

If what you mean by this is the throttle barrel does not completely close then you need to confirm that whatever your engine is, that if there is a throttle stop screw on the carburator, it is not stopping the barrel from closing completely. In other words without any pushrods connected to the carbs throttle arm that when you move the arm to closed position and look down the hole (Venturi) the barrel is completely closed. Many engines come with throttle stop screws that the fellows often ignore this.

John

AMA 74894

My Feedback: (1)

+1. you need to be able to mechanically close the venturi barrel completely.
that throttle stop screw is often overlooked.
I do fly Nitro / Gas as well as electrics (dabble in heli's too) and have never used a throttle curve on anything but heli's.
as has been mentioned:
Set the throttle servo so that you've got a good reliable idle with the stick at idle, but still have enough trim authority to shut the engine down with the trim lever /kill switch.

(I also totally agree, I WISH TX manufacturers would leave the old mechanical / analog trim lever specifically on the throttle)
if they did that though, I'd have nothing to complain about

opjose

Set up your TX to move the throttle to 100% in each direction... normally the defaults....

Now install the linkages so that with the throttle trim at CENTER, and the stick at center, the carburator opening is as close to half open as you can guesstimate.

Once done, move the stick fully up and observe the servo and linkages to assure that you have no binding, and that the servo is not trying to move the throttle beyond the full open position. If it is, re-adjust your geometry/linkages so this does NOT happen.

Do the same for full stick down but adjust the linkages so that you get CLOSE to a 1mm to 2mm opening showing... it will just be a tiny "slice" open in the carb.
Double check for binding at full throttle.

Once done bring the stick up to about the 20% position and start up your engine.

With the engine running, go into the radio settings and REDUCE your throttle end point for low stick. The engine should speed up.

Do this until the engine is running at about 30% of full power. Now drop the stick all the way down.

The engine should be idling VERY fast or beyond that... now INCREASE your throttle end point for low stick until you get the idle speed you are looking for. As you INCREASE the end point the idle will drop.

Try to set your idle so your plane only just begins to "walk" forward when it is on smooth pavement. Ideally it should not move forward at all.

Once done, keep the stick at idle and bring down your throttle trim all the way ( or on throttle cut equipped RX's hit the throttle cut button ). The engine should then stop immediately assuming no plumbing problems or leaks.

That's it.

I did this one day at the field and I was quite surprised to get a bevey of novices watching saying "so THAT's how you do it!".

rlipsett

and now for my 2 cents worth. I don't like analog trims too much because they are to easy to bump and knock off there position. digital trims can not be moved until you power up the transmitter so no accidental travelk adjustment in the car going to the field. Setting epa is the last thing to be done and should be very tiny since the best way to do it is to have the correct geometry and use the proper holes on the horns. this maintains your resolution on the servo for precise control. I do put about a 20 on the expo of the throttle to simulate a linear throttle response. ps throttle down trim full down engine stop. trim to idle. the last bits of travel on the carb in the wot position does just about nothing so just make sure the linkage does not stall up there.