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Old Dec 19, 2012, 09:33 PM
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I went ahead and bought one tonight. I went with sport version instead of the slowfly this time. Motor went from 890kv to 1100kv. Supposed to be the same thrust but I'm assuming a higher pitch speed. Hopefully it will be a tad faster
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Old Dec 19, 2012, 10:19 PM
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Look the motor up on Heads Up Rc and you can get the specs and recommended prop.
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Old Dec 20, 2012, 04:55 AM
mg3
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New Zealand
Joined Dec 2011
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Hi everyone,

Yesterday i was flying my slow stick(specs below) and the motor cut out for about a second approx 5 mins into the flight and then again about 3 mins later, i believe the servos werent responding aswell, anyhow i thought nothing of it and continued flying. Todays flight didnt end so well, again the motor and servos cut out for a second and i continued flying, then a few minutes later i lost full control of the plane, no servo response and no motor response it came down nose first into the ground(Lesson Learn't ).

I believe that with the new steerable tail wheel mod i have added has caused the servos to draw too many amps with the added resistance, therfore exceeding the 2A BEC resulting in the controls to be shut down, would you agree?

If this is the problem what would be my best solution, smaller servos, a new esc with higher BEC or what? recomendations?

Any help/info will be greatly appreciated
Thanks in advance, Mark

specs...

Motor: Brushless Turnigy 28-30 1100kv with 1047 Slowfly prop
Battery: Turnigy 1500mah 3s 11.1v Li-po
ESC: Brushless Turnigy Plush-18A, BEC-2A/5v, DC-5.6v-16.8v
Servos: HXT900 x 2
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Old Dec 20, 2012, 09:18 AM
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Quote:
Originally Posted by mg3 View Post
Hi everyone,

Yesterday i was flying my slow stick(specs below) and the motor cut out for about a second approx 5 mins into the flight and then again about 3 mins later, i believe the servos werent responding aswell, anyhow i thought nothing of it and continued flying. Todays flight didnt end so well, again the motor and servos cut out for a second and i continued flying, then a few minutes later i lost full control of the plane, no servo response and no motor response it came down nose first into the ground(Lesson Learn't ).

I believe that with the new steerable tail wheel mod i have added has caused the servos to draw too many amps with the added resistance, therfore exceeding the 2A BEC resulting in the controls to be shut down, would you agree?

If this is the problem what would be my best solution, smaller servos, a new esc with higher BEC or what? recomendations?

Any help/info will be greatly appreciated
Thanks in advance, Mark

specs...

Motor: Brushless Turnigy 28-30 1100kv with 1047 Slowfly prop
Battery: Turnigy 1500mah 3s 11.1v Li-po
ESC: Brushless Turnigy Plush-18A, BEC-2A/5v, DC-5.6v-16.8v
Servos: HXT900 x 2

I'm assuming that the BEC you have listed above is the BEC that was included with your ESC (meaning internal BEC)?

Also, did you make sure that the tail wheel assembly would turn freely before you hooked up the servo linkages? I noticed on mine that if I drilled the hole out in the fuselage the exact with of the tail wheel wire that is supplied with the kit that there was too much drag when I turned the tail wheel by hand. So i used a "one size up" drill bit and it made the tail wheel move very smooth. Meaning, without any servo rod connections I could turn the plane on it side and the tail wheel would turn under its own weight. If the tail wheel is causing extra stress to the servo its very possible it over loading the internal BEC as you mentioned in your post.

If I were you, I would make sure the tail wheel moves freely without anything connected to it. Then, I would invest $10 in an external BEC. Here is one I am using on my slow stick. I also use this one on my 450 helicopters and I abuse it pretty good, never had an issue and the BEC is never warm (and on a 450 heli its powering 3 9gr servos, 1 mini servo and a gyro so I know it will handle anything your SS can throw at it):
http://www.ebay.com/itm/US-Ship-Hobb...item231ef7250a
I've purchased from this seller a few times and its always extremely fast shipping and well packaged.

If you need help hooking up an external BEC just let us know. With an external BEC hooked up, you could burn out your motor and ESC and still control all servos as long as your battery is not completely out. It's extra insurance for getting your plane down safely and I run them on all my setups even my small planes like the SS. For 9grams of extra weight and $10 I feel its definitely worth it.
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Old Dec 20, 2012, 04:03 PM
Right Rudder
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USA, FL, Orlando
Joined Nov 2010
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Hi Guys!

Just having fun with my new 808 Key Chain Camera looking AFT on top of my GWS SLOW Stick. It is powered by the BP Hobbies A2217/9 Brushless motor, a staple selection and setups to many of my Park Flyer size RC Airplane Models.

E-Flite 30-AMP Switch Mode ESC
Thunder Power Pro-Lites 3-Cell, 1350mAH, Li-POLYs
Castle Creation BERG DSP 72-Mhz (FM) Receiver
GWS Stardard Narrow Servos

Recorded on location, Moon Port Modelers RC Club in Titusville, Florida and early in the morning, Thursday, December 20, 2012.

Enjoy!
GWS Slow Stick RC Electric Airplane model with 808 Key Chain Camera looking AFT 12-20-2012 (5 min 41 sec)
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Old Dec 20, 2012, 04:10 PM
mg3
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New Zealand
Joined Dec 2011
17 Posts
hi,

Yes it was the internal BEC. When i assembled the tailwheel it felt pretty smooth but would surley have some added resistance and i have heard that the HXT900 servos do tend to suck alot more amps than other servos. Is a 9gr servo rated at 1.6kg a bit of an overkill for the slow stick? would i be better off with HXT500 5gr servos rated at 0.8kg? Either way i do like the idea of an external BEC is there one suitable from here: http://www.hobbyking.com/hobbyking/s...R-VR_UBEC.html

thanks, Mark
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Old Dec 20, 2012, 07:27 PM
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United States, SC, Greer
Joined Nov 2012
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The Turnigy 5A (2nd from the top is good). I also have that one and it has not had any problems

I'm currently using 4x HXT-900 9gr servos on my setup (I've added ailerons) without any problems with my external BEC.
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Old Dec 20, 2012, 11:38 PM
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Mark, I fly two Sticks with exactly the same power configuration as yours, both with steerable tail wheels and one with ailerons (4 HXT900 servos). Neither has exhibited that problem, so I do not believe that the tail wheel is the cause. The easiest way to narrow down the possible causes would be to install an external 5 amp BEC.
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Old Dec 21, 2012, 01:39 PM
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United States, OH, Eaton
Joined May 2006
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Quote:
Originally Posted by kaptondave View Post
Mark, I fly two Sticks with exactly the same power configuration as yours, both with steerable tail wheels and one with ailerons (4 HXT900 servos). Neither has exhibited that problem, so I do not believe that the tail wheel is the cause. The easiest way to narrow down the possible causes would be to install an external 5 amp BEC.
I was thinking the same thing. I have even used 4 of these servos on a 450 heli with no external BEC. I would check the battery connector very carefully by twisting and pulling on it. Does your Rx blink if power has been lost during flight? I also would not rule out a bad servo. The HXT900's have been known to have problems exactly as you describe.

Chris
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Old Dec 21, 2012, 02:04 PM
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I'd check a few other things before simply buying a new BEC, because this doesn't sound exactly like a BEC issue.

Are you running a 2.4GHz radio? If so, you wouldn't be able to just momentarily lose power to the receiver and then get control back an instant later. They usually take a few moments to initialize. If you're on 72MHz, the receiver reset time is much shorter and you can get away with brief power losses.

Sometimes you can temporarily lose the connection between the transmitter and receiver, resulting in this type of momentary loss of control. This usually happens when the plane flies through the "cone of silence" which projects straight off the end of your transmitter antenna. You can solve that by simply... Never letting the antenna point straight at the model.

If any single HXT900 was consistently drawing enough current to cause that kind of problem, I don't think the servo would last very long. Do you have a wattmeter to check the current your servos are drawing? If you give one servo a full input in some direction but hold the shaft still (BRIEFLY), the current it draws is the most it'll ever pull under any circumstances and it's certainly more than it'll draw in flight for any reason. In any case, a 2A BEC should be PLENTY for running two HXT900s on a Stick, so going to a bigger one is just putting a band-aid on whatever the real problem is.

Try to reproduce the problem on the bench (take the prop off the motor). See if you can get the BEC output to drop to ~0V by cycling the sticks while loading the servos with your fingers. I have an ESC with a built-in BEC that cuts out if there's a sharp change in motor RPMs. No one has a clue why, but it does. They can do weird things like this occasionally... But like I said, this just doesn't sound BEC-related.
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Old Dec 21, 2012, 03:28 PM
mg3
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New Zealand
Joined Dec 2011
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Quote:
Originally Posted by chris1379 View Post
I was thinking the same thing. I have even used 4 of these servos on a 450 heli with no external BEC. I would check the battery connector very carefully by twisting and pulling on it. Does your Rx blink if power has been lost during flight? I also would not rule out a bad servo. The HXT900's have been known to have problems exactly as you describe.

Chris
Thanks for the reply, i might try it with a 2s 1550mah rhino battery and also do a range check and see if the problem persists. Not sure if the rx blinked or not. Maybe new servos might be a good idea. thanks, Mark
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Old Dec 21, 2012, 04:03 PM
mg3
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Joined Dec 2011
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Quote:
Originally Posted by C₄H₁₀ View Post
I'd check a few other things before simply buying a new BEC, because this doesn't sound exactly like a BEC issue.

Are you running a 2.4GHz radio? If so, you wouldn't be able to just momentarily lose power to the receiver and then get control back an instant later. They usually take a few moments to initialize. If you're on 72MHz, the receiver reset time is much shorter and you can get away with brief power losses.

Sometimes you can temporarily lose the connection between the transmitter and receiver, resulting in this type of momentary loss of control. This usually happens when the plane flies through the "cone of silence" which projects straight off the end of your transmitter antenna. You can solve that by simply... Never letting the antenna point straight at the model.

If any single HXT900 was consistently drawing enough current to cause that kind of problem, I don't think the servo would last very long. Do you have a wattmeter to check the current your servos are drawing? If you give one servo a full input in some direction but hold the shaft still (BRIEFLY), the current it draws is the most it'll ever pull under any circumstances and it's certainly more than it'll draw in flight for any reason. In any case, a 2A BEC should be PLENTY for running two HXT900s on a Stick, so going to a bigger one is just putting a band-aid on whatever the real problem is.

Try to reproduce the problem on the bench (take the prop off the motor). See if you can get the BEC output to drop to ~0V by cycling the sticks while loading the servos with your fingers. I have an ESC with a built-in BEC that cuts out if there's a sharp change in motor RPMs. No one has a clue why, but it does. They can do weird things like this occasionally... But like I said, this just doesn't sound BEC-related.
hi, thanks for such an in depth reply.

first off, yes i am running 2.4ghz but i only lost power for 2 seconds max the first few times and then the last time i lost power was when i crashed, i was at a low alttitude so it took maybe 3 or 4secs and then it was in the ground (hopefully you get what i mean)

I plan on doing a full range test so will see what effect pointing the antenna to the model has.

I will deffinatley test the current draw with a wattmeter and see if that displays anything odd and replace the servos if need be, I am also leaning toward getting a new ESC with a higher bec for added saftey because my "bulletproof" turnigy 18a-plush is getting very old and worn. Im thinking of getting this: http://www.hobbyking.com/hobbyking/s...ontroller.html
Do those specs sound about right? if not any other suggestions?(from hobbyking because they ship to new zealand)

Once again thanks to everyone for the advice, Mark

EDIT: Did a bench test without the motor hooked up and i was working the servos back and forth (via the controller) for about 3 mins and the ESC/BEC was DEFINITELY hot, but not so hot that i couldnt leave my hand on it. This to me seems that both or one servos is drawing an excessive amount of current causing the ESC/BEC to over heat and automatically shut down resulting in a loss of control. Somewhere i read that if there is enough cool air it can actually cool the ESC/BEC and it will automaticaly start up again which may explain why i only lost control for a couple of seconds. Anyway i think i will get a new ESC/BEC(see link above) and a couple of new HXT900 servos.
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Old Dec 21, 2012, 08:56 PM
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United States, AZ, Chandler
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When I buy servos, especially inexpensive ones, I try to buy a couple extra. That way, you can pick the best of the bunch for your plane.

If a servo is totally DOA, your build doesn't get held up. If a servo just doesn't quite make muster, it can be re-purposed. For me, funky servos get put on stuff that I don't care if it crashes; a giant chuck glider with a blue wonder, a homemade everglades-style airboat, foamy combat PBFs and the like are the perfect place for a wonky servo.
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Old Dec 22, 2012, 09:31 AM
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Originally Posted by carlsoti View Post
When I buy servos, especially inexpensive ones, I try to buy a couple extra. That way, you can pick the best of the bunch for your plane.

If a servo is totally DOA, your build doesn't get held up. If a servo just doesn't quite make muster, it can be re-purposed. For me, funky servos get put on stuff that I don't care if it crashes....
When I buy cheap servos I expect them to work. I have purchased 25 to 30 HTX900s from HobbyKing. None were DOA or "wonky" on arrival but if I got a bad one it would go in the trash. I would not risk even a second or third tier model with a bad part that can be replaced for $3.
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Old Dec 22, 2012, 03:22 PM
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United States, AK, Fairbanks
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It's normal for a linear BEC to heat up substantially when it's sitting there powering the servos on the bench just because of how it works. If it's not getting too hot to touch within the space of a few moments, it sounds like the servos aren't stressing it any more than normal.

I just did a quick test with a Turnigy TG9e, which is extremely similar to an HXT900. The most current I could get it to draw while cycling back and forth was 0.15A, and in a forced stall condition it drew ~0.6A. There was a substantial bit of wire between the servo and power source so "real" numbers may be very slightly higher, but I'd say that servo would never draw more than ~0.75A at most.
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