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Getting back into RC. Almost done with Simple Scout - need to ask questions.

hitjim

New member
#1
Tried getting into RC in high school. Built about 3x planes ~75% then had to get rid of it all during college.

Excited to get back in now that DIY is so prevalent and electronics has advanced so far. Also nice to get into a hobby that's more constructive and (sometimes) meditative. Mostly glad to be doing something very different than the software dev day job :)

Since I figured I should assume I'll crash my first plane quite a few times, the FT kits seemed like the perfect balance of "quick-start", "low risk", and where I also got to scratch the itch to build it myself. I also love the enthusiasm and penchant for rapid prototyping that FT folks/fans seem to have. Feels familiar to what I like about software dev/engineering - that is when I remember to not overthink or overplan.

I ended up getting FrSky RC tx/rx - and have a possible technical problem/question. Any suggestions on the best place to ask in here?

Thanks
 

The Hangar

Well-known member
#2
Welcome! Feel free to ask away on this thread if you’d like. I know we have a lot of FrSky users here.:) I really like the simple scout - I’m actually going to be going out and teaching someone to fly on it today! Do you have pictures of yours? Have fun!
 

FDS

Well-known member
#3
If you have an FRsky transmitter, then the learning curve for OpenTX that it runs on can be quite steep. It does a lot, but it doesn’t do anything for you, you have to set up a lot more than in a pre programmed radio.
 

hitjim

New member
#5
@The Hangar Thanks! I'll add some pictures. Didn't take many progress shots. It goes so much more quickly than the freeflight balsa build I finished before this!

@FDS That's been my experience so far. I figured it would be worth a shot, as I'm no stranger to complicated systems. I think most of my struggle comes from still being pretty light on newer RC gear terminology and "tribal knowledge" that seems commonplace after 20yrs have passed :p ... The manuals that come with the FrSky Taranis x9 Lite and R-X6R were pretty light. And so much on Youtube etc assumes you're building drones or trying to squeeze 16 channels out of 6 ports etc. It was shockingly opaque to figure out how to bind and use all 6 ports on the receiver for 4 channel on the Scout. Figured out I was needing to configure the "internal receiver" and add a mix for one of the Aileron servos. Not a complete buzzkill, but it was way more googling and trial/error than I expected.

@Merv and all, thanks - here goes.

I've been bench-testing the throws etc, and found that with:
  • Zero throttle
  • Power Pack B
    • FT Radial 2212 1050kv V1
    • FT ESC 35A - BEC 3A 5V
    • 4x FT ES08AII 9g servos
  • Tattu 3S 1300mAh 11.1V 14.4wh
  • FrSky Taranis x9 Lite, R-X6R receiver
When I quickly go from neutral to max throw on rudder, elevator, and aileron - the receiver seems to reboot/restart/powercycle and then re-connect. Motor speed doesn't seem to make it better or worse. I can go max throw on ele/ail all day without this happening, even with max throttle.

Any likely culprits? Capacitor on ESC perhaps? Mismatched gear?

IMG_20191129_180209222.jpg IMG_20200110_154620226_HDR.jpg IMG_20200112_152716080_HDR.jpg IMG_20200112_152501334_HDR.jpg IMG_20200119_142819909.jpg
 

FDS

Well-known member
#6
You are probably “browning out” your BEC (Battery Eliminator Circuit.) This happens when you try to run too many servos off a small Bec, if you have a 3A one on the ESC then it’s unlikely to be able to deal with all the servos at once, depending on their draw. When holding max throw all the servos are at peak power load. Check that your hinges are nice and free moving, if you put too much hot glue on them they get stiff, stalling the servos.
The good news is that when learning you are unlikely to be at max on every channel at once. Don’t forget to set up the dual rates, you want to start on low rates with some expo.
Also get the OpenTX Companion on your computer, it makes setting up ,ideas easier, there’s a wizard in it that pre sets some stuff for you. Agreed not much fixed wing on YT with Open TX. Painless360 is pretty good for planes usually.
 

Merv

Well-known member
#7
I would check to see if any of your servos are stalling out. That is, the servo is trying to move further but can’t, something is stopping it. If so clear the obstruction or change the end points until the servo stops growling when at full stick.

A stalled servo is drawing all the power is can. 4 - 9g servos is the maximum you should use on a 3a BEC. 9g servos draw about 3/4 amp each. I agree with @FDS, you are drawing too many amps & you voltage is dropping lower than your Rx can tolerate.
 
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hitjim

New member
#8
The rudder and elevator hinge reinforcement went pretty smoothly. The ailerons, however, I needed to go back and reheat+remove much of the glue. It was too long a stretch and I wasn't fast or precise enough yet to do it in one pass.

That said, hinges seem to be pretty free, but I'll give it another look and check for obstructions. Doesn't seem like the servos are fighting too much to keep max throw.

I'm not opposed to trying another ESC with different BEC to quickly check a hardware theory off the list. I can shop around, but happy to hear any favorites. I don't really have a bucket of backup/leftover gear built up yet. I think I'm most interested if I can err on the side of caution and find something with a higher-rated BEC, since right now I'm effectively testing on zero load, while up in the air it'll be fighting airspeed as well.

Thanks!!
 

FDS

Well-known member
#9
I would properly set the end points and throws first. Once that is done look again at the BEC performance. I use the Turnigy Plush 40A ESc with 5A bec if you want to change yours.
3A should be enough for what you have, stalling because the endpoint is greater than the actual available movement would be my culprit now you have looked at the hinges. You will need to not exceed the max movement of the control surface anyway, so as not to break the hinge, besides browning the ESC.
Use the kits deflection gauge to set up low and high rates. Endpoints are adjusted in the inputs screen.
 

Merv

Well-known member
#10
....I needed to go back and reheat+remove much of the glue. ...... Doesn't seem like the servos are fighting too much to keep max throw.....
I use a covering iron to reheat the glue. An old clothing iron would work just as well. Go to the second hand store and get an old one.

There should not be ANY “servo fighting” to hold max throw. Hold the servo in a half way position and listen. Then go to full throw. They should sound the same, if not back off the end points.
 
#11
I checked and the servos are completely silent on each channel at max throws, as they are in the middle (when I'm able to hold the stick steady enough!) - they were silent before and after the adjustments below.

I also adjusted the weight to a sliver lower than the 12deg prescribed by the throw guide, and adjusted a few offsets to ensure neutral again.

I checked to make sure I get this brown-out behavior when jumping to max throws away from the direction of the hinge cuts, in addition to when the I'm throwing in the direction that compresses the cut/joint.

I could probably set up to take a few videos if anyone thinks that would help. My impulse is that the adjustments I might make would be so slight, that if my bench tests were able to avoid brown-outs, I'd be too close to the threshold for comfort once I put the thing in the air. That is, at least based on my current understanding.

Really appreciate the feedback and ideas so far. Please let me know if it doesn't seem like I'm catching what you mean or if you have more ideas etc. I'm also 100% fine working in a stop at the local Hobbytown if testing with something like this (with an EC3 adapter) makes sense ... although I'm having trouble finding the BEC rating online for this - and it's not clear from the product listing on the Hobbytown or Flitetest stores - https://www.hobbytown.com/eflite-40a-esc-w-ec3-efla9891/p995718
 
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FDS

Well-known member
#12
I have a full size scout with 9g servos, dual rates all set up, full rates limited to the servo travel, it runs off a 3A bec. Not had brown out in flight. I have crashed it for other reasons but not that!
I would say you should never be flying at 100% throws on all the control surfaces at once, it simply doesn‘t happen. You almost always limit the throws to an extent and usually if you go all out on one you are only applying a bit on the other. There’s very few basic manoeuvres requiring all three control surfaces and none I can think of (aside form PANIC) using all three at full at once. I await someone clever to tell me this isn’t so but I haven’t needed it.
I have used 4 and 5A Becs on occasion, just because I found a cheap decent ESC with one. I haven’t noticed much difference in practice.
If none of the controls are binding up (check linkage stoppers) and the servos are not being stalled then unless you have huge current digital servos I am at a loss as to how the brown out is happening.
 

Merv

Well-known member
#13
I checked and the servos are completely silent on each channel at max throws, as they are in the middle....
Silence, that is what we are looking for.
I could not see any BEC rating on the ESC you suggested.

I generally go for a 50 amp ESC's, I will not buy one without a 5 amp BEC. I do a lot of 3D flying. With 5 amps, I've never had a brown out, even though I put the sticks in the corners a lot.
 
#16
Thanks for all the input and suggestions so far.

@Rhaps the pushrod channels on the side of the fuselage seem fine, but maybe I'll try running a hotel card or scrap pushrod through them again to make sure. I did the coffee stirrer add-on to the internal guides as well.

Since I'll be in the neighborhood for appointments tomorrow, I may pick up a spare of the 35A FT ESC I already have and another with a higher-rated BEC if they have one available. Then I'll probably try each to see if it makes a difference - first to see if the one that came with my powerpack is the culprit, then to see if higher BEC max even makes a difference.

I got my start in engineering as a QA dev, so while I acknowledge all the sage advice in here that it may be overkill, I can't help but keep testing theories if I've got the opportunity :D

 

Bricks

Well-known member
#17
Dumb question is your battery fully charged? Did you take out the bind plug after binding I know that sounds dumb but I have done that before.
 

The Hangar

Well-known member
#19
Yeah, the battery was a little over 80%. My particular FrSky receiver binds via a momentary button on the PCB you hold when powering on.

I ended up getting one of these at the local shop. Haven't done a distance test yet, but no more benchtop brownouts. https://www.hobbytown.com/hobbywing-flyfun-40a-v5-brushless-esc-hwa30214002/p697556

Thanks again for all the help. I figure now I have an ESC for a future 3ch job :)
Glad you got it all figured out! Weird thing is I built my bushwacker with flaps so a 6 servos in use while using a 3 amp BEC, and didn't experience any issues in flight. When maxing everything out several times in a row, I could get it to cut out, but that never happened in flight.