crazyjoseph

My Feedback: (3)

Yah what you said
My bad

MIXMASTER

My Feedback: (15)

Definately not knowing is a problem, what do you do with the flight gear? I know some who either throw away or sell all the stuff at a huge loss. I would rather attempt to find out what it was,it may mean taking eveything completely out & apart to inspect. A PITA but what else can you do? In this case posted here, you can assume no damage as a result of the "hard landing", only bent gear & a scrape or two. The largest plane I fly is 30%, no redundancy anywhere, never had a switch,receiver fail in 20 years. Only 1 battery failure, Nicd memory was the reason. I've been lucky, never had a momentary problem & not knowing what was the cause.

crazyjoseph

My Feedback: (3)

I have a 35% 260 and when i power it up there is a considerable lag time before elevator servos fire up. All the other surfaces fire immediately. I'm running 2 2400 lions into fut pcm no power box. I'm thinking there may have been some power fade maybe from regulator and elevator being on longer leads suffered the most. I noticed on someones post that was testing batteries and ran them down he said the elevator was th first surface to quit.

crazyjoseph

My Feedback: (3)

If it where me I would cycle the bat. and loose the regulator. My feeling is its a power issue not a 2.4 issue.

Jake Ruddy

My Feedback: (40)

Alright guys.. the weekend is almost here.. I will be setting up all the servos on a fish scale to test the torque of them with no force and pre-loaded with some force.

I plan to get to the bottom of it this weekend so I can clear off my work bench and get back to work.

3DAP

Sorry to hear the news Jake. R.I.P


3DAP

bodywerks

My Feedback: (4)

Are you letting the batteries peak using it in li-ion mode? If so, that could present a problem! Charging to anything over about 7.5 volts will weaken an A123 pack in short order. If you are letting them charge to 8.4 volts (which is the Triton's li-ion cutoff for a 2S pack), then you are right on the cusp of them venting out and $#itting themselves.

Jake Ruddy

My Feedback: (40)

No.. I was just using that to test discharge them after this happened.. I have a 4S I used to charge

bodywerks

My Feedback: (4)

One does not have to read every post to have an opinion about the title of the thread, which is why I expressed my concern about it before reading every single post. The title would have been less intrusive had it been something like "Lost my plane today - what went wrong???" Instead, it comes right out and says "What failed - Spektrum or A123". Such a title makes it hard to not judge a book by its cover, sorry...

Jake Ruddy

My Feedback: (40)

Actually it was 2.4 problems or A123 or ? leaving the door wide open for possibilities.....


Not that I need to defend my choice of title... but I particularly wanted those with 2.4 and A123 technology involved in the thread since I haven't been running it that long and I wanted useful input from those with more experience using these technologies than me.

bodywerks

My Feedback: (4)

I know what the title says, but it is easy to read it differently.
Bottom line, I know it wasn't your intent and you have an open mind about the whole deal. I do hope you get it figured out.

Jake Ruddy

My Feedback: (40)

Thanks.


A little update.. I picked up a new volt meter over the weekend.. this is a multifunction unit and the voltage reads more inline with everyone else.

I also picked up a digital 50lb fish scale. Even with 2 servos pulling on it and locked, and me pulling hard force on another servo I cant make the pack drop below 6.39. When hammering all the sticks the voltage doesn't vary near as much as the other unit I was using.

I also did an ohm check on the elevator extensions and everything seems to be fine.

Back to the fish scale, I did hook up my servos to it to see how many pounds I could pull. I tried to keep the arms centered at 90 degrees to teh table and keep the line tight between servos. They seem to vary... but it's hard to get them all setup the same.

My question would be.. how many pounds should a 5955 pull in a setup like this? I am unsure how to calculate it and never tried a test of this nature.

nonstoprc

My Feedback: (90)

The force can be estimated using the calculator (http://www.csd.net/~cgadd/eflight/calcs_servo.htm). I plugged in the following

max air speed: 60mph
control surface width: 3.5 inch
control surface length: 20 inch
max deflection angle for control surface and servo: 45 degrees

The torque it gives: 86.7 oz-inch. 86.7 oz-inch / 16oz is about 5.4 lb-inch. So if the weight is hung at the tip of the control arm and the tip is 1 inch from the center of the servo arm, the weight should be 5.4 lb. If the tip is 1.5 inch from the center, the weight should be 5.4 / 1.5 = 3.6 lb.

With this amount of (constant) weight applied (e.g., using cans of coke), turn on the receiver, and measure the current and/or voltage.

You may need to figure out the params based on the airplane in question.

Jake Ruddy

My Feedback: (40)

That doesnt really help since I am not trying to calculate how much is needed for a given speed. I dont know how fast it was going. I appreciate the help though.

I am trying to figure out if anyone has hooked up a 5955 to a fish scale and what it could pull... I am curious.

rctom

330 oz./inch would be a pull of about 20 lbs. on a 1 inch arm. A longer arm will result in lower readings, if you have a 1.25" arm then divide 20 lbs by 1.25 and that should be the approximate pull.

However, I have seen some testing reported here on FG that showed the 5955 doesn't actually have that much torque, I think it was actually something like 220 oz./inch. Whatever you get in pounds, multiply by 16 to get ounces and then multiply by the length of the arm to get oz./inches.

if you get a 15 lb pull with a .75" long arm, then 15x16x.75=180 oz. inch.

TF

Jake Ruddy

My Feedback: (40)

Thanks Tom,

Well on the aileron servo that I could push back I get like 5-6 pounds cold. This wing is 98% fine.. just one part of the leading edge is crushed, so I dont think its a result of teh crash.

On the other servos I get 9-10 pounds cold and then down to 7-8 pounds after I beat them up for abit. This is all with 1.5" So that is saying 240oz (high end) cold and 192oz (on high side) and 168oz (low side) after I beat it up for awhile.

I will have to set this rig up a bit better and use 1" arms to make it easy. I am going to pull some other 5955s and compare them as well. All of this has me curious now....

Mitsu1

My Feedback: (13)

All these calculations are fine, but it seems were drifting away from what may have caused the crash. You got no pitch change at all when you pulled back on the stick. An old Futaba S148 standard analog with 41 oz. torque would have given you at least some pitch alteration. My point is ... highly unlikely both of your 333 oz. 5955 digitals crashed you for being too weak on torque to even slightly "affect" ... your pitch attitude.

Mitsu1

My Feedback: (13)

Since you yourself have ruled out the batteries as the culprit, and weak .. , too weak to even slightly rotate the plane 5955 digitals (two of 'em!) .. aren't likely to be the problem .... then it seems its either the elevator channel on the TX is screwy, ... or both RX channels that you were plugged into were screwy, ..... or what I've always believed .... The Power Expander was not properly sending the signal to the servos. I hang my hat on the last one.

quist

My Feedback: (198)

If both servos were plugged into the same channel, I would agree it could be the expander. But the servos were split, one was on the left side of the board and the second was on the right side. That would be one amazing coincedence that only the two elevator servos would be affected. You obviously have a agenda.

nonstoprc

My Feedback: (90)

Well, the key here is to simulate the actual load on ALL servos. With the method you describe (with one fishing scale), you can only observe the current/voltage when one servo is under the load.


If you were doing IMAC at the time of crash, the speed can be set at 80mph (quite high). For 3D, it may be even less. From the speed and size of the elevator etc control surfaces of the plane, you can get a quite accurate torque number. From the torque, get the lb. number. Use the fishing scale to figure out weight of that mount, for each control surface. Assume the weight number for elevator is 5lb, for aileron is 4 lb. Then hang 5lb of weight each at the two elevator servos, and 4lb of weight each at the two aileron servos. The weight will acts as the load each control surface experiences during the flight. When you move the control sticks, you are faithfully simulating the situation before the crash, and hopefully see the two elevator servos will NOT be able to move the weight at certain deflection angles.

I measured the current draw for two 5945 and one 5955 servos yesterday (without a load) together. The draw is about 1.5A for a snap.

Hope this helps.

Jake Ruddy

My Feedback: (40)

You aren't reading / following the thread in detail, clearly... and obviously have the PE stuck on the brain.

The reason I started looking at the servos has been stated in this thread serveral times. When I put the elevators on the table and pressed on them I could hold them at neutral pretty easily. They seemed to have good power at full deflection but not at neutral.

Do you know many SF PE's are out there and how many have actually failed??? Where are not talking about MPI regs here. Robert doesnt post much outside of the SF form because people like you bash his product with a closed mind and don't even give him a chance.

The PE and receiver have been sent in review / repair.

Lastly.. the elevators didn't just stop working... from inverted I pushed over the top and they lost torque / power through that maneuver.. I pushed right to a 45 down.. was at idle and had no elevators after that. The whole point of testing them on the scale was to get them heated up and see if I could make them fail after extended use.

The elevators were on opposite sides of the PE using different channels.

Jake Ruddy

My Feedback: (40)

nonstop: Thanks for the ideas... I will continue to play.

As this gets dragged out I am becoming less sure I can find a true reason for the crash.. the longer I play with the servos here the longer it will be before I get them back from Hitec.

Will see what happens over the next few days.

Hammbone

My Feedback: (309)

You didn't have any elevator control from 2 different servos on 2 different channels. This makes me think that the problem wasn't the servos. Even with weak servos it seems you would have gotten some deflection.
I would think it was a loss of current flow, or loss of signal. I don't think you've said if you had any failsafes set up?

Jim

quist

My Feedback: (198)

On current draw with servos, most of the current demand comes at the start of movement. If you watch on an amp meter, move the stick to full deflection. Amp draw ramps up and then settles down as you hold the endpoint, if the servos don't bind at the end of course.

craigteffe

My Feedback: (24)

Can someone here explain what happens if you have one servo that may have a short internally, not all the time just once or intermitantly. Could it reset the reciever? Or would it just suck all the amperage not allowing the rest of the servos to work?