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HelicopterBeginners Corner › Mechanically setup and ATV setup pitch/throttle
03-30-2005 04:09 AM  13 years agoPost 1
Valveman

rrNovice

Marshalltown, Iowa

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Hello all,

This is my first post and this website has been very helpful. A lot of reading and researching does help to answer most of my questions, however, you just have to ask sometimes.

The heli I have is a old Concept 30 SRT. Bought it from a pawn shop including a JR XF622 radio and the whole nine yards about two years ago. I basically stole it from them for under $200.00. Now I have been flying the heli for awhile off and on and can hover and even do a little bit of forward flight (nervously). After reading most of the posts on RunRyder and getting to know my helicopter better I am serious getting into the understanding of the radio and all of its functions.

So here is the questions.
1) When setting up the helicopter there are many ways to approach it. First off, you must define what you will be starting with. Assuming that a) all sub-trims are zero, b) both the pitch and throttle curves are set to 0% 50% 100%, c) the ATV is set to +/-100%, and d) the Dual Rate is set to 100% you should try to mechanically set up the pitch for an even minimum and maximum pitch. If this is not possible due to binding linkages or shortness of travel then you should adjust your ATV such that this cannot happen. The goal is to maintain an equal travel on both ends because this will provide the most linear curve mechanically. Once this is done the pitch curve can be alter as needed.
2) Same as 1 except you do the same with the throttle correct. Once the throttle is mechanically setup you alter the throttle curve as needed.

I have read on this site that ATV should be set to +/-100% while others say +/-80%. Yes one could set it up as +/-80% but then you must compensate by adjusting the physically linkage by moving the ball on the servo horn in or out from center as needed. Or does it really matter.

Appreciate the help.

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03-30-2005 11:01 AM  13 years agoPost 2
Rawlie

rrApprentice

JHB

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I agree with your above analysis

I keep my ATV's at 100% or as close as possible.

If you have built and setup your heli perfectly according to the manual, you may still find slight binding at the extremities of servo movement. In order to avoid the servo's buzzing, I would then set ATV to say 90% to stop them from buzzing.

I cannot really comment on the Concept, but on my Raptor all my ATV's are 100% except throlttle is 90% because it was binding slightly. Definitely agree with Dual Rate at 100% unless you are learning to hover.

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03-30-2005 12:16 PM  13 years agoPost 3
dgshaffer

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New Jersey

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When I set up my Caliber 30 the first time, I set it up with mechanical CCPM vs eCCPM. I had to cut down on all of the three servo movements to keep the swash plate from contacting the mast in extreme cyclic positions. Some as low as 74%. I feel as though there is no magic percentage for setting servo limits. I have found that you have to program your radio to ensure that the servos can do their job without stressing them at their endpoints. Take a look at the underside of the swash plate and see if it contacts the mast while you move the cyclic around. I’m just a new guy here but I can’t imagine that contact between the swash and mast could be a good thing. Just moving the cyclic foreword, backwards, left and right wont show it either, I found contact in the corners. My servo travel is adjusted so that there is almost no gap but they travel as far as possible.

Someone please correct me if I’m dishing out misinformation.

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03-30-2005 12:22 PM  13 years agoPost 4
BarracudaHockey

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Jacksonville FL

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Adjusting your linkages by moving the ball location in and out until you get as close to 100 percent of your ATV gives you the best of both worlds of torque and speed.

As you move the ball in on the servo you increase the torque available but decrease the speed. The opposite occurs as you move the ball out, you quicken the control surface reaction but you decrease the torque on it.

Also by running your atv's at or near 100 percent you get better resolution on the servo.

For your throttle, where torque isn't as important as speed its best to set your atv's around 70 or 80 percent so that your throttle response is a little faster than your collective response.

Andy
AMA 77227
http://www.jaxrc.com

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03-30-2005 02:22 PM  13 years agoPost 5
Leif

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USA

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Valveman

It doesn't really matter. Many of the "rules" for setup are rather nitpicking, and only come into play when you're pushing the limits of the machine. I don't mean that good setup isn't important, but you'll find that many of the recommendations (posed as critical issues) are an attempt to get that 0.2% improvement in some linearity curve or extra millisecond of speed. Of course a well set up heli will behave better, but the extent of perfection required rarely reaches the levels that people here will insist is needed.

That said, the general idea with a good setup for any servo link is to get the full travel of the servo to match the full travel of the control, with the 50% point set so that the control horns are 90 degrees to the rod, and with the rod length matching the center-to-center distance from the servo screw to the control horn screw.

For most controls, you want the ATVs to be as close to 100% as possible so that you get the full resolution and torque from your servo.

The recommendation to use 80% ATVs on throttle is a "trick" to make a slower servo go faster. However, in this case you would set your ATVs to 80% FIRST, then adjust your control horns so that you still get full throttle throws (as opposed to setting the physical controls first and then adjusting endpoints with the ATV). I'm not sure I agree with using this trick, but I suppose it's a viable workaround to having a fast throttle servo. The proper recommendation is to have a faster servo on throttle than you do on collective. For basic hovering and forward flight, it really won't matter much, but for advanced aerobatics this becomes more important, as you will want the engine power to advance before the load increases during hard maneuvers.

The ATV adjustments are there to fine-tune any slight variations you might have in the physical linkages. The main reason to use them is to prevent binding of the controls against the physical enpoints. Binding can cause damage to your servo, as well as extremely rapid drain on your RX battery pack.

Leif

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03-30-2005 02:24 PM  13 years agoPost 6
Leif

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USA

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As you move the ball in on the servo you decrease the torque available but increase the speed. The opposite occurs as you move the ball out, you slow the control surface reaction but you increase the torque on it.
Actually, the opposite happens. You get more torque with the ball closer to the center, and more speed with the ball further out.

Leif

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03-30-2005 04:23 PM  13 years agoPost 7
Zephan

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Lompoc, CA

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Raptor Technique has some good explinations about this. In general you do want as close to possible 100% ATV, but as someone pointed out, if you put your throttle under 100% (say 80% or 90%), then the throttle will be a bit faster than the pitch servo (provided they are the same servos). This can help the throttle to lead the pitch changes a little bit and help keep the engine from loading down. I also had to adjust my cyclic ATV's down to 75% to keep the swash plate from binding with full cyclics. I could move the ball links in a bit on the servo instead, but the ATV adjustment seems to work fine and I get about 6.5 degrees of cyclic.

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03-30-2005 08:23 PM  13 years agoPost 8
BarracudaHockey

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Jacksonville FL

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Wow I knew that. I wrote that before I woke up. I went in and corrected it and tried to get away with an inocent look but you quoted me.

Sorry, no posting before morning coffee for me any more.

Andy
AMA 77227
http://www.jaxrc.com

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03-31-2005 02:36 AM  13 years agoPost 9
Valveman

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Marshalltown, Iowa

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First off, my appreciation for all of those posting a response. This is a great website to share and gain information (taken with a bit of salt of course).

From what I've gathered thus far it is best to "box-up" (or square up or even a parallelogram) the linkages that go from the servo to the desired control element (aileron, rudder, throttle, elevator, pitch). What is meant by this is that the distance between the servo's center and its corresponding servo horn should match that of the desired control elements center and its corresponding operating arm. Also the distance between the servo's center and the desired control elements center should match that of the servo horn and the operating arm of the control element (this is where the physical linkage goes and connects the servo to the control element). And like everyone said when the servo is set to its middle (or centering) position which is done by putting the stick in the middle you strive to have equal amounts movement from that center point.

On my old Concept 30 the pitch is controlled by having the servo moving one side of an L-shaped part which is then connected to the pitch slider. The bend in the L-shaped part is where it pivots and it is not possible to change where this mounts. Also the length of the L-shaped part cannot be changed either. In order to set up this linkage correctly it is probably best to follow the instruction manual however it makes no mention about how far the linkage is to be from the center of the servo to the spot on the servo horn. Too far out on the servo horn and linkages bind up. Too far in on the servo horn and you don't get maximum travel of the pitch mechanism.

I guess what I really wanted to know is at what ATV percentage do you start out with when doing the mechanical setup. It appears that 100% is best unless there is some limitation due to the control linkage being to short or too long (which does have adjustment limitations eventually such as the ball link screwed in to tightly or not tight enough on the rod). Once you are setup mechanically as best you can without binding or shortness of travel you then adjust your pitch and throttle curves next.

And it makes sense that if you want to have the throttle advance before the pitch then setting your ATV's to 80% during the mechanical setup will do that. That may mean that the control linkage coming from the servo horn might have to be moved out or in to achieve this.

I appreciate the help and especially those that posed a response (Rawlie, dgshaffer, barracudahockey, Girard Ibanez, Leif, and Zephan).

Thanks,
Valveman

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04-01-2005 03:02 AM  13 years agoPost 10
MJWS

rrKey Veteran

Airdrie, AB - Canada

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You got some good answers here. It really isn't important what the atv value is set to (except for with a gov like the TJ).

When your ATV is at 100/100 it is behaving to spec. You have the manufacturers torque and speed available to you. You also have the standard resolution available. You will always be fine close to these values.

After that it all becomes a balancing act. We can trade torque for speed mechanically with a longer arm. We can go even further by lowering ATV. The only downside to lowering your ATV way down is you lose resolution. With good servos you may not feel it real easily, but if you push it to the extreme you will see that you lose the very fine control. It works exactly the opposite when you increase ATV and shorten the arm.

Assuming similar servos on pitch and throttle. We use this to our advantage. We stick a long arm on the throttle because it doesn't need the torque, and we want it faster than pitch. We reduce the ATV's to suck our transit time even lower by using less throw.

So there really isn't a 'RIGHT' value. You actually have a reasonably large performace envelope with each servo. You can make it faster, slower or stronger as desired... but it is always a compromise.

Just two more bits,

Mike

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HelicopterBeginners Corner › Mechanically setup and ATV setup pitch/throttle
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