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Is your WH Edge "snap-prone" ??

Old 07-06-2004, 11:44 PM
  #26  
David_Moen
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Default RE: Is your WH Edge "snap-prone" ??

Swapping the elevator servos should be straight forward. If one of them is the culprit, your unexpected snap should be in the opposite direction.
Old 07-07-2004, 02:05 AM
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Default RE: Is your WH Edge "snap-prone" ??

Hitec.

I promise, I promise, I promise.

I won't go there.

Hitec.[:@]
Old 07-07-2004, 07:05 AM
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NE0
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Default RE: Is your WH Edge "snap-prone" ??

I did some checking on the servos last night before bed and think my problem lies somewhere there. I didn't have time to swap yet, but this is what I found...

BOTH servos are not performing properly in my opinion. They "feel" rather weak when you apply any pressure against the ELE's with your hand and run the sticks. If you put either ELE to full down, place your hand on it and pull full up, it doesn't move... until you take your hand off, then it snaps up to full up.

The servos are both acting like they only have about 40oz of torque or so. Either I have two bad servos, or two bad sets of leads, or two bad connectors, or a bad battery, or a bad voltage regulator. The turd hunt begins.

Tom
Old 07-07-2004, 07:08 AM
  #29  
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Default RE: Is your WH Edge "snap-prone" ??

One other thing. The extensions are both 24" extensions, plus another 6" pigtail on the RX. Add the 10" servo pigtail and that's 40" of lead. Is it possible my voltage is dropping by the time it gets to the servo? I don't know any way around this, as I need that much to reach back there, and I'm sure other 28% and larger planes have to do the same? Why wouldn't they have the same problem?

Tom
Old 07-07-2004, 08:48 AM
  #30  
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Default RE: Is your WH Edge "snap-prone" ??

As I noted earlier --the servos must work together.

Looks like you have built in a problem.
For that model you don't need a lot of elevator throw - for sport flying.
The losses in pigtails can be huge.
also the type of "servo matching device"can be a real problem.
I simply hate dual elevator servo setup but I do use em .
But typically I use two, JR8411 servos on 6 volts - thru HD pigtails -thru two channels which were setup and matched before installing servo in the model.

Also setup the servos side by side and match the entire throw range - servo to servo --THEN install this setup into the model . The linkage should then be geometrically adjusted to give proper throw - leave the servo controls alone once they are matched.
Any difference in throw --under air loads --reads the same as applying rudder.
Old 07-07-2004, 09:27 AM
  #31  
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Default RE: Is your WH Edge "snap-prone" ??

ORIGINAL: NE0

I did some checking on the servos last night before bed and think my problem lies somewhere there. I didn't have time to swap yet, but this is what I found...

BOTH servos are not performing properly in my opinion. They "feel" rather weak when you apply any pressure against the ELE's with your hand and run the sticks. If you put either ELE to full down, place your hand on it and pull full up, it doesn't move... until you take your hand off, then it snaps up to full up.

The servos are both acting like they only have about 40oz of torque or so. Either I have two bad servos, or two bad sets of leads, or two bad connectors, or a bad battery, or a bad voltage regulator. The turd hunt begins.

Tom


If you are truely running 6 volt try taking out voltage regulator.
Old 07-07-2004, 12:38 PM
  #32  
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Default RE: Is your WH Edge "snap-prone" ??

Neo,

I'm curious about the length of the servo extensions. Where do you have your receiver located?

On both my Edge and Extra, with the receiver mounted on the tray provided in the rear "bay" under the hatch and behind the fuel tank bulkhead, I need only 18" of extension to get to the back of the plane. That's 18" additional to the actual servo lead, of course. 12 inch extensions are used on the ailerons with the receiver located as mentioned. Another 18 inch extension is used on the throttle servo if the servo is mounted on the motor box, less extension would be needed if it was mounted farther aft inside the fuselage.

Next part of the question, why are pigtails needed for the elevator servos? You should be able to directly plug the individual servo leads into the receiver. Or into a Matchbox if you are using one. The Matchbox uses (1) 3 inch pigtail for connection to the receiver.

Are you using Hitec extension leads? If so, that could well be your line losses if you are having them. I promised I wasn't going to go here, but everytime I had a wiring problem in the past it was caused by a poor connector on a Hitec extension. I have found that the Cermark extensions have been reliable in manufacture, and offer little line loss.

Would it be possible to re-locate your receiver in a manner that would reduce the amount of extension wiring you are using? It is possible that you are experiencing a line loss, but I don't believe that's the entire problem.

Applying pressure to the elevators as you described and not getting fought by the servos when you change stick position does indeed indicate that the problem is either at the servos or with their power supply. I am running a 6v regulator with my flight servos (8611s') without any problems whatsoever, so I don't think that part of it would be an issue if you are also using one.

It's easy to check regulator output, a simple voltmeter will do that fine. You could also check the voltage at each individual servo by temporarily installing a "Y" at the servo lead and extension, and plugging in a voltmeter at the open leg of the "Y". Those that are better versed in electrical measurement than myself could tell you how to measure amperage.

In any case, it's good to see that you have been able to narrow the playing field a little in locating the problem. It can be exasperating at times when a problem such as yours occurs. Don't give up, it's a really great flying plane when it all gets sorted out. We're all hoping you can get the plane flying in the manner it normally does, most pleasureably.
Old 07-07-2004, 11:38 PM
  #33  
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Default RE: Is your WH Edge "snap-prone" ??

OK....not sure if this is the right place to jump in, but I am going to try anyway. Because of the usual brand-bashing, I almost hesitate to post this, but since we are sharing problems and ideas and potential solutions....hey...what can it hurt...right?
Here's my story.....I have a WH Edge 540 that is just about ready for its maiden. The elevator and aileron servos are Hitec 5645s and the single rudder pull-pull set up is on a JR 8611. Throttle and choke are some old spare Airtronics Z 102 standards. Rudder servo choice was simple....I wanted that much torque and durable construction and price was fair. Choice for elevator and aileron servos was cause the torque, digital centering, and price were all within requirements and I have always had good luck with Hitec 605 and 645, as well as with JR 537s and Airtronic 102s. Have not had good luck with new JR 811 digitals or Hitec 425s.....but they do make good dog chew toys (when 811s aren't busy quivering).
Since I have had very good luck with Hitec non-digital, I decided to try their digitals...but stayed away from 5945s since there has been so much bad press on RCU......so decided to try digital version of 645..hence the choice of 5645.
So you are wondering why I am telling you all of this?........Although I am not having the problem originally described at the beginning of this thread, when I read all of it I decided to perform a "resistance" test on MY elevators. Much to my surprise, here's what happened.....As I move the elevator stick up and down I get wonderfully crisp movement and quick and accurate centering. However, when I use my hand and put pressure (up or down) on the elevator surface it will give (a lot) with whatever pressure I apply!!!!!! I was astounded....I thought ALL of these digital servos were supposed to provide rock-solid resistance to forcible movement when compared to analog counter-parts. The only location where the surface would NOT yield to my pressure was when it was at full-up or full-down....and I believe this is because the geometry of the control arm and push-rod was pushing almost directly in-line against the servo arm because of the servo reaching its max travel.
Now I have been doing this RC thing for quite some time....and like each of you I have my favorite brands. I have good and bad to say about JR and good and bad to say about Hitec......not really much of anything to say bad about Airtronics....but they are not the culprit in this story.
I guess after all is said and done, I don't know if I am expecting more "stoutness" and "resistance" than should be expected of 5645s.....or if I should expect them to not move at all from any position I move them to with the stick. Like the fellow above I also have 24" extensions on elevator servos plus pigtails for a total of about 30-36 inches from servo to JR receiver. I use two batteries (1650 mah) and two switches (MPI) and to balance the plane I moved the batteries just behind the firewall on the inside of fuse just above the aluminum landing gear plates. The switches are in the aft positions supplied with the plane (just behind and below the rear of the hatch). So the first thing you might say is why so much wiring from batteries to switch to receiver (just behind wing tube) and from servos to receiver? Since that is a very good question, I tried simply connecting the elevator servo leads to the receiver and connected a battery to a JR charge switch and straight from the switch to the receiver.....thus eliminating long wiring runs from anything to anything else........but still had the same lack of resistance when pressing on the elevator. So I thought "hummm.....maybe a bad servo".......so I tried three more but still had the same results. These servos are supposed to have approx 143 oz of torque at 4.8 v. I know I can increase their torque by going to 6v.....but I guess I expected them to be "less moveable" even at 143 oz and 4.8v. Am I being unrealistic? Would other 143 oz servos from another manufacturer be "equally moveable" as these Hitec 5645s?
One possibility I have considered is the fact that my servo-to-pushrod-to-control-arm geometry is oriented to give the servo the upper-hand on mechanical advantage. Is it possible that when I use my hand to move the elevator against the resistance provided by the servo, I am acutally applying enough pressure that is then "amplified" in the reverse direction towards the servo and winds up being equal to or greater than the 143 oz the servo is putting out? If so, I guess this could explain why the servo is yielding to my pressure.....but I really am not pressing very much on the elevator and the servo easily yields and feels "mushy"...when I expected it to feel "locked" in position.
So.....what's the likely cause of my problem? I am expecting too much in the way of "rock-solid resistance" from these servos? Is it a problem with the Hitec brand or would similar torque servos from another manufacturer behave the same? What should I do to fix it?

Thanks for your assistance and feedback in advance.
OB1
Old 07-08-2004, 12:47 AM
  #34  
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Default RE: Is your WH Edge "snap-prone" ??

ob1,

You have brought up some excellent observations and comparisons here. Leaving "brand bashing" out of the picture, I cannot imagine why any digital servo with a 140oz plus rating would yield to light pressure. You may have found the root of Neos' problem.

It would be of interest to anyone using this particular servo to see if this weakness would be consideded "normal" by the manufacturer. It would be better if someone who is using them were to contact Hitec. I know if I was experiencing this with an 8611 I would be on the phone to Horizon first thing in the morning!

I enjoyed you description of uses for the 425s' and 811s'. It was not only descriptive, but accurate.

Thanks for you post and observations!
Old 07-08-2004, 05:17 AM
  #35  
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Default RE: Is your WH Edge "snap-prone" ??

I have 5625 all around on my edge. 2 ganged together for pull pull and they work absolutly wonderfull on my edge even at full throttle passes. With the 2-5625 ganged together for a total 260oz of power I can deflect rudder at any given time and plane will respond quickly. Knife edge loop is no problem as well.

I wrote this to say mine also feels week on the ground when holding force against the elevators or ailerons but you can't go by that. Just fly the plane and see how she responds in the air.

Most flyers I know and I Know quite a few being that I fly at 4 different fields, will never fly there planes at its full potential were they would even tell the difference between better and the best servos on a given plane.

If changing out your servos helps your snapping delema then great but for others putting all this expensive stuff in your planes might be a big waste of money if your not a Chip Hyde or Quequi type of flyer.

I once used a Kangke fun 50 with all standard servos and an os 46 to beat out 35 and 40% fliers in a freesyle (anything goes) contest.
Needles to say none of these guys had to much to say to me after the contest, But it sure got a lot of the 40 class fliers to start trying some new moves.
Old 07-08-2004, 10:41 AM
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Default RE: Is your WH Edge "snap-prone" ??

I have a plane on my bench right now that has Hitec 5645 servos on it.
There is no way I can push that servo back by pushing on the surface without the risk of breaking the elevator. I just tried it.

The extensions are 24" 22ga, plus the pigtail on the servo, 4.8v 1650 NIMH
Old 07-08-2004, 11:22 AM
  #37  
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Default RE: Is your WH Edge "snap-prone" ??

You shouldn't be able to do it with an analog servo, either. If the servo is permitting you to easily over ride it, it will permit air loads to do the same.
Old 07-08-2004, 04:07 PM
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Default RE: Is your WH Edge "snap-prone" ??

Pat,
I know you shouldn't be able to do this, that was my point.
I was referring to the quoted statement from above.



I decided to perform a "resistance" test on MY elevators. Much to my surprise, here's what happened.....As I move the elevator stick up and down I get wonderfully crisp movement and quick and accurate centering. However, when I use my hand and put pressure (up or down) on the elevator surface it will give (a lot) with whatever pressure I apply!!!!!! I was
Old 07-08-2004, 06:27 PM
  #39  
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Default RE: Is your WH Edge "snap-prone" ??

Thanks, Jemo.

What some of these people are experiencing is a classic case of "servo blowback". The early 40 and 42 oz.in. standard servos were notorious for this. The problem was not limited to any one manufacturer, either.

Any servo of any type and by any manufacturer that can be easily overridden with mild pressure is inadaquate for the intended purpose in this case. Either the servos are defective in some manner, or they have misrepresented as far as their capability is concerned. I would first suspect some form of amplifier problem.

A servo that is too weak to hold the intended surface in position will most certainly soon be the cause of a crash! If they were mine, I would not hesitate to contact the manufacturer to clarify the weakness issue. I absolutely would not fly the plane until it has been resolved. I know that we are right smack in the middle of the flying season, but that's no reason to sacrifice a very good aircraft to a less than adaquate control component.

I wish you all the best of luck in this, because I know the problem is not with the plane.
Old 07-09-2004, 07:41 AM
  #40  
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Default RE: Is your WH Edge "snap-prone" ??

OK guys, great discussion. Further investigation has shown virtually exactly what "ob1" described above...

I changed battery, extensions, servos... bypassed the switch and regulator... nothing changed. (by the way, I just have 24" extensions, no pigtails... my mistake). So, looking at the plane again, it appears I may have made a rookie mistake. In setting up the pushrod linkage to the elevators, I gave the elevators way too much leverage against the servo. In other words, linkage was mounted at the lowest point on the Ele control horn, and the highest hole on the servo arm. Then, this gave me so much throw, I had to back my rates down to 30% on my transmitter.

So, I went back and redid the linkage to give the servos max leverage/advantage. Lowered the linkage on the control horn to the longest distance on the post possible, and moved the other end down one hole on the servo arm (closer to the axis). I now have my throws set at 70% and 100% which gives me 13 and 22 degree throws.

What I then found is that the elevators were WAY stronger. At full deflection, I can press so hard as to flip the plane off the table or break the elevator without the Ele giving at all. But, if I go to full "negative deflection" and try to return to positive deflection, I can hold it back with my hand "to some degree." Before making this change, the same test would show the Elevator to not fight my hand at all in trying to return to nuetral or positive deflection. I can still stop it from coming back to nuetral now, but I have to really fight it. When it's at any positive deflection, I can't push it back to negative at all anymore.

Anyhow, my best friend got out a couple of his planes that have dual 5945's in the tail for elevator and we checked his. These planes are known good flyers, and one even does a wall at virtually any speed with no snap. The results were the same as with my plane. At positive deflection, you couldn't push the Ele back. At negative deflection you could stop them from returning to positive (with your hand) if you really fought it hard, but it did fight (like mine) hard trying to push back to nuetral/positive.

So, I think the combination of my poor linkage geometry along with my stab incidences being off by as much as 1 degree may be my problem. With all this fixed now, the only way to tell is to take it back up and see how it perfoms now. With rain in the forecast for the next 5-7 days, it may be a while though [&o]

Thanks for your help, I'll let you know how it goes as soon as I get the chance to try it out.

Tom
Old 07-09-2004, 07:44 AM
  #41  
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Default RE: Is your WH Edge "snap-prone" ??

Oh yeah, on a side not. I have the JR8611 pull-pull on my rudder, and it performs pretty much the same. At positive deflection, I can't push it back... but at negative deflection, or even nuetral, I can stop it from going positive. It's hard, and stresses the rudder, but I can stop it. I don't think this is a "brand" issue... just the nature of geometry.

Tom
Old 07-09-2004, 10:04 AM
  #42  
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Default RE: Is your WH Edge "snap-prone" ??

Good of you to admit a set-up error!
Old 07-09-2004, 12:30 PM
  #43  
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Default RE: Is your WH Edge "snap-prone" ??

Glad you found the problem!! I think everyone was going crazy trying to figure it out. Even better, I'm pleased to see it wasn't a weak servo issue.

Regarding the manual restraint of the servos, if you divide the torque rating of he servos by 16 you come up with the approximate number if pounds that the servo should be able to handle. It also gives you an idea of how much physical force you could place against it to restrain it. It's a plus or minus thing, and I wouldnIt do that very often. It is possible to damage the flight surface, or the servo amplifier, or both.

Good flying.
Old 07-25-2004, 12:46 AM
  #44  
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Default RE: Is your WH Edge "snap-prone" ??

Ok guys this is all great info but it had me wondering....

Just how do you have your Edges set up? Basically what I mean is are you running 3 or 4!QUOT! arms on your rudder servo(s)? What size arms on the elevator servos are you using and how far out from the surface are your push rods attached to the horns? Are you running 1!QUOT! or 1.25!QUOT! arms on the elevator servos and which way are you installing them up or down?

How about throws, is everyone getting adequate throw without 1.25!QUOT! arms and ball links and STILL is able to have enough available torque to get the job done? I personally have been flying mine with less throw than I would like because I will need longer arms and ball links to get my throws maxed out. I'm not even sure that it will be necessary to max out for throws since I am still getting used to my Edge and breaking in my DA.

I'm specifically asking in regard to 3D set up with max throws. Setting up for sport and precision requires a lot less throw to get the job done so it's much easier to set up from the beginning if that is all you will be using the plane for.
Old 07-25-2004, 02:18 AM
  #45  
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Default RE: Is your WH Edge "snap-prone" ??

Shogun,

I've set up both an Edge and an Extra so far. Both with excellent results. As far as servo arms are concerned, I am using 1-1/2' aluminum arms from SWB. The ball link to center of output shaft distance is 1-1/4". That's on all of my flight surfaces. My rudder servo is mounted in the tail for a direct hook up. For the pull/pull arrangement, you will need a 1-1/2" "double" arm.

The distance betwen the servo output shaft and the ball link or clevis on the servo arm. should be equal to, or less than, the distance from the control surface hinge line and the linkage mounting point on the flight surface. This maintains a 'mechanical advantage" to the servo. Note that the measurement is fron the center of the flight surface hinge line. Not from the surface of the aileron, rudder, or elevator.

For general all around sport flying and mild 3D, there is no need for the longer servo arms. Both planes are excellent flyers at low to medium rate settings if that's what you desire. As a matter of fact, hovering only requires low rates anyway.

Enjoy the plane. I know I am!
Old 07-26-2004, 12:20 AM
  #46  
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Default RE: Is your WH Edge "snap-prone" ??

My setup:
DA-50 w/Slimline Pitts
5945's on ailerons and elevator halves
8611 on rudder w/pull pull
5425 digital on throttle
ball bearing standard airtronics on choke
2 2150 NiMh's @ 6v on rx
1 2150 NiMh @ 6v on ignition
weight approx 18lbs
CG 5 1/4 inches
ailerons 45deg up and down
elevator 50deg up and 55deg down (has room to go to 55 up and 60 down with linkage as pictured)
rudder 45deg (horns hitting fuse sides)

This plane flys like a dream, floats on landings and has no snap tendancies. Fly along at 1/2 throttle and pull full up and just slides into a wall, rock and snap free. Winds up so tight in knife edge spin that its a blur, I have 4 gallons through it so far and love it more every time I fly it.

Brian
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