Let's talk about servos - Whatever is on your mind

[kyleservicetech]

Originally Posted by AEAJR

UBEC, to the best of my understanding, is a brand name.

Interesting!

I just googled uBEC and found a number of hits. One of the hits is a company with the UBEC initials that manufactures Radio equipment.
http://www.ubec.com.tw/en_about.php?...&company_id=28

Most of the hits were by several different suppliers of switching power supply type BEC's such as this one: It has UBEC right on the uBEC.
http://www.hobbyking.com/hobbyking/s...Reduction.html

Looks like the company ubec, and the familiar hobby uBEC are completely different products.

Learn something new every day!

[hoghead5150]

UBEC was a brand name, well the company that released a switching bec called it the UBEC and the name kinda became a catch all for other companies to use for their switching bec's.

either way tho, the best bec to use is a switching style, and in all honesty its best to use an external bec. while the bec inside most esc's will be adequate they do build heat, and the more heat you can keep away from your esc the better you are.

[kyleservicetech]

Originally Posted by hoghead5150

UBEC was a brand name, well the company that released a switching bec called it the UBEC and the name kinda became a catch all for other companies to use for their switching bec's.

either way tho, the best bec to use is a switching style, and in all honesty its best to use an external bec. while the bec inside most esc's will be adequate they do build heat, and the more heat you can keep away from your esc the better you are.

Yup, kind of like Kleenex!

[AEAJR]

UBEC came from the product called the ultimate BEC
http://www.aeromicro.com/Catalog/koo...5v_3982367.htm

I normally use the BEC in the ESC. Never had a problem.

[dahawk]

Guys,

Putting together an ARF I won at a fundraiser/fly-in raffle. It's a YAK-54 Groupe Tranchant from HK . Fiberglass fuse, balsa 1385mm WS. Flying weight will be ~ 5.5 -6.0 lbs. I won't be doing true 3D flying, at least not initially. Mainly sport aerobatics.

Already have a 500KV 1300Watt EMP 4620 motor and a 80 amp ESC. Now for the servos. Need something in the 38g range. The Hitec 225 (Deuce and quarter) are very nice but dang, very pricey. Can anyone recommend a good alternative based on experience? I'm looking at Turnigy, Emax, Corona metal gear, etc.

Cheers,

-Hawk

[kyleservicetech]

Originally Posted by dahawk

Guys,

Putting together an ARF I won at a fundraiser/fly-in raffle. It's a YAK-54 Groupe Tranchant from HK . Fiberglass fuse, balsa 1385mm WS. Flying weight will be ~ 5.5 -6.0 lbs. I won't be doing true 3D flying, at least not initially. Mainly sport aerobatics.

Already have a 500KV 1300Watt EMP 4620 motor and a 80 amp ESC. Now for the servos. Need something in the 38g range. The Hitec 225 (Deuce and quarter) are very nice but dang, very pricey. Can anyone recommend a good alternative based on experience? I'm looking at Turnigy, Emax, Corona metal gear, etc.

Cheers,

-Hawk

Do you need the smaller sized servos? If standard servos will fit, check these out.
http://www.amainhobbies.com/product_...2-Deluxe-Servo

I don't know the size of the control surfaces, or how much throw you are putting on them. With a 1300 watt power system, you don't want under powered servos.

[AEAJR]

I added a servo calculator to the first post, for anyone who is interested.

[DanWard]

Originally Posted by AEAJR

I added a servo calculator to the first post, for anyone who is interested.

Thank you!

[AEAJR]

While this is an electric forum, I would be interested if any of you have experience with servos used in glow planes.

Glow planes produce a LOT of vibration where electric planes produce almost none. How does all that vibration impact the servos?

Do they wear out faster?
Do you have to pad them in some way?

Inquiring minds want to know.

[Turner]

No personal glow experience yet but a lot of standard size servos come with rubber mounts.

[kyleservicetech]

Originally Posted by Turner

No personal glow experience yet but a lot of standard size servos come with rubber mounts.

Yeah
I checked vibration levels on that guys model with the twin cylinder gasser, wasn't much difference between the servo and its rubber grommet mounts, and the mount itself.

Take a look:
http://www.wattflyer.com/forums/showthread.php?t=66525

Back in the mid 1960's I ran glow engines with the servos of that time that used "Stand Up Components". Vibration on those components resulted in them breaking off during flight. About every 20-30 flights.

The modern radio systems with surface mounted components got rid of a lot of those types of issues.

[Voltron]

I've been flying glow planes for over 20 years and have never really had any vibration related servo problems. When I first started flying, I did have a vibration issue that affected my receiver. I used a metal rod with a z bend to connect to the throttle lever on my carb. At one point the rod was close enought to contact the engine case. At a certain RPM, the metal rod vibrating against the engine would create a radio freuency in the spectrum that affected my receiver. The servos would go crazy jumping back and forth and the plane became uncontrollable. Fortunately the throttle would still react to my transmitter and when I cut the throttle the servos would work fine. At that time I was so inexperienced, I had no idea what was causing the problem. A more experienced flyer in our club found the problem. I thought he was crazy at first, but we adjusted the rod away from the engine case and it never happened again.

[kyleservicetech]

Originally Posted by Voltron

I've been flying glow planes for over 20 years and have never really had any vibration related servo problems. When I first started flying, I did have a vibration issue that affected my receiver. I used a metal rod with a z bend to connect to the throttle lever on my carb. At one point the rod was close enought to contact the engine case. At a certain RPM, the metal rod vibrating against the engine would create a radio freuency in the spectrum that affected my receiver. The servos would go crazy jumping back and forth and the plane became uncontrollable. Fortunately the throttle would still react to my transmitter and when I cut the throttle the servos would work fine. At that time I was so inexperienced, I had no idea what was causing the problem. A more experienced flyer in our club found the problem. I thought he was crazy at first, but we adjusted the rod away from the engine case and it never happened again.

Nice thing about that 2.4 Ghz radio frequency. It's very difficult to accidentally generate 2.4 Ghz, and mechanical vibration of things like servo linkages is not one that will.

[flypaper 2]

The 72 radios were more susceptible to noise. We used nyrods from the servo to the motor as the metal pushrod acted like an ant. and could cause interference. Also, if you had a metal arm on the carb, you had to use a plastic connector on the pushrod. The metal to metal from carb arm to metal connector could also cause interference. 2.4 radios are not so prone to this kind of interference, although ign. noise can still cause problems.

Gord.

[Stevephoon]

Wow... A month or so ago I had a servo fail while flying my SA Daddy-O. Luckily, it was one of the two aileron servos and it failed in a neutral position. I landed the plane fine after noticing that the ailerons were not as effective and needed some odd trim.... This was after flying for 3 minutes or so. These servos have been in this plane since day one. At least 20 months. I've been flying this plane a lot over the last two summers. Most likely hundreds of flights.

Anyway... After I landed I saw that one aileron no longer worked. I pulled out the servo at the field to check the extensions. They looked OK. The servo itself had a large buldge in the middle. I had another servo at home, so I went home and put in a new servo of the same type and went back to flying. Everything has worked great for a month or more with the replaced servo, same extension wires, same RX, same ESC/BEC....

Now I have finally opened up the dead servo and.... the entire circuit board is burned to a crisp. After being in use for two flying seasons in the plane I fly the most.

Makes me say.... hmmmmmmmmm replace all of them ???

Steve

[kyleservicetech]

Originally Posted by Stevephoon

Wow... A month or so ago I had a servo fail while flying my SA Daddy-O. Luckily, it was one of the two aileron servos and it failed in a neutral position. I landed the plane fine after noticing that the ailerons were not as effective and needed some odd trim.... This was after flying for 3 minutes or so. These servos have been in this plane since day one. At least 20 months. I've been flying this plane a lot over the last two summers. Most likely hundreds of flights.

Anyway... After I landed I saw that one aileron no longer worked. I pulled out the servo at the field to check the extensions. They looked OK. The servo itself had a large buldge in the middle. I had another servo at home, so I went home and put in a new servo of the same type and went back to flying. Everything has worked great for a month or more with the replaced servo, same extension wires, same RX, same ESC/BEC....

Now I have finally opened up the dead servo and.... the entire circuit board is burned to a crisp. After being in use for two flying seasons in the plane I fly the most.

Makes me say.... hmmmmmmmmm replace all of them ???

Steve

Yeah
I've got video of a giant scale gasser model going in at a local fun fly last summer. IMHO, the servo in the aileron got overworked, and smoked. Unfortunately the servo electronics shorted out, burned up all the wires between the servo and the A123 receiver battery pack.

Your failure could have been a lot worse!

[AEAJR]

Here is an idea.

Go to the servo calcualtor I posted earlier in the thread. Put in your surface dimmensions and your aircraft's pitch speed. Now run the calculator and see what torque is recommended. Add 30% to allow for inflated specs and for things like dives. Are your servos up to that?

The other thing to look at is your wire. If these are big servos and/or digitals, they may be trying to pull more than the wire can supply meaning a voltage drop. Could result in servo problems.

Look at the gears in the bad servo. Do they look worn or cracked? If they are they could have been binding. A bound/stalled servo is going to pull a ton of power which can burn up the servo.

Things to check.

[nidly]

Thanks for doing this thread. I am interested in the calc because I'd like to learn how to select servos. I'm satisfied with allowing the calc do it for me , but I get some surprising results. At least I am surprised. This is not unlike an online calc I tried and get the same thing.

Let's do my GP e-stik since it is the one I want to work on and it seems the factory put in a much bigger elevator servo than I come up with.

I'm putting in 66 mph and elevator at 4x50x10 deg from center
For rudder I put in 8x17x50 deg from center

The rudder needs 37 in-oz and the elevator needs 1 in-oz. I can go along with this since it is pretty easy to visualise when looking at the plane (especially when the surfaces are worked)

aileron needs 8 oz-in according to the calc , but I'm not interested in downsizing that one even though it appears to be oversized too.


One doesn't have to be an engineer to be able to say "Yea, that rudder is going to need a lot more torque than the elevator" I guess the question then becomes why did the factory overspec the elevator servo so much? Can I get away with a very small weak one? The factory has used identical servos in all three controls ES-80 http://www.electrifly.com/miscproducts/gpmm1210.html

[AEAJR]

Because if you only need 10 oz and they HS-55 is 16 oz, well that works.

Most of our servos are over capacity and that is not a bad thing.

your typical home PC runs at less than 20% utilization. You know anyone going out looking for slower PCs?

[nidly]

I suppose since the price difference is minimal then they just picked the largest requirement and used it for all three positions in the same plane. Easier for parts,manuals,pics,ect.

I think that since the rudder needs 37 and the es-80 has 32 I will leave it , the ailerons don't work real smooth and bind toward the ends of their travel that I will leave the servo there as well. It needs 8 and I can easily see that the ailerons could use double or triple that figure because of the way they are designed. The elevator however moves nicely and smoothly with zero binding and even if I double the manual's recommended throw up to 20 degrees I can still get away with 4 oz-in. I'm sure I could use a 8 oz-in servo for elevator , right?

[AEAJR]

The ailerons bind, or does the servo bind, or does or the control rod bind? Binding is not good. Binding leads to breaking or overload or overheated BEC or other nasty things.

What is binding?

[nidly]

It's just the way the factory made the aileron controls. It comes covered so I'm not even sure what's inside the wing , but two rods stick straight down and hook to only one servo. I'm not worried about it, I have two other wings that are the same way. Maybe they are just at the end of their travel hitting something inside. I don't quite use all that travel anyways and I'm happy with the single aileron servo and roll performance. They just seem to take a lot of effort to move them. It's probably a rather poor design , I've just never been inside the wing before.

[nidly]

It is pg 7 of this manual , but I'm not changing anything on the ailerons or going to double servos at this time. http://manuals.hobbico.com/gpm/gpma7500-manual.pdf The most I might do is to cut some of the covering and trim some wood around those two rods for more travel. I may also adjust the length of the rods that stick out of the bottom.

[AEAJR]

Looks like they are operated by torque rods. Looks fine in the photo.

[flypaper 2]

Your on the right track. Unhook the pushrod connector from the ail vertical wires where they come out of the wing and make sure the slots are long enough when you give full ail control with the trans. You can feel any stress when you move the ail wirs by hand.

Gord