T28 update and putting test equipment to good use

I really wanted to put my test equipment to use and I needed to check out my Airfield T28 with possible BEC/receiver/servo issues.  So I put it all together in this one big post.

This was a complicated subject with all the test equipment and airplane gear so I decided to try my hand at a video post.  So, here goes.

Thank you for watching my video post, let me know how you like this format.

Update to the video:

Further inspection showed that the faulty servo was not the steering servo but the door servo.  In the following photo you can see the bottom servo is the same servo that was over heating in the video.  You can also see that the push rod from the servo is flexed a lot.  This is obviously putting a lot of stress on the servo and is most likely the cause of the current draw.  Something will have to be done about this during the repair.

Stressed servo that failed

I have noticed that the current generation of the Airfield/FMS 1400mm Trojan T28 do not use a servo for these doors but instead uses spring linkage.  I may go this route for this repair and cut one servo from my count.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Testing to the rescue

Some times stuff happens and you don't really know why.  This is why you need test equipment.

This was the case with my Dad's new 3D plane.  This was a kit that came without any electronics but had recommendations.  Since it was from Hobby King, of course the recommendations were for their parts.  No big deal, I actually like most of their parts.  I helped my Dad figure out what he needed and what was the best fit of parts from the US warehouse.  When he got everything together he noticed that things were getting hot.  Not a good sign.

He had a good idea of how to put a heat sink on his speed controller, since this is what was getting hot, and I helped him figure out the best way to put it on.  What he did was to use some heat sink compound in the center and then some epoxy on the corners to secure it down.  This was of course after cutting away some of the heat shrink to expose the ESC aluminum heat sink.  This is what he ended up with.

Darn good job, don't you think?

This is the other side showing that it is a Hobby King brand 25A (30A burst) variety.  This should already be a pretty good ESC and with the added heat sink, even better.  The velcro in the photo was something he added to help keep the ESC tacked down in his plane (nice idea).

After some testing, it was still getting really hot, too hot to touch and would actually go into shutdown mode!  This already happened once while he was test flying it.  We initially thought he had lost control when it went behind an obstruction, but we no longer think this was the case.

So, now to the testing and test equipment.  I was able to come down with the family and my gear (yes, family comes first. Since there was still some space left in the trunk I could take my gear along!).  We hooked up my power meter in between the battery and the ESC and began testing it out.

We found that at full throttle it was only pulling 14A.  This is well below the rating of 25A, but it was roasting hot after only about 30 seconds.  It even when into shutdown mode about 20 seconds later.  Even with the added heat sink, it was too hot to touch!

We then tested the power draw on my Wild Hawk which I upgraded to a brushless motor with a Turnigy 25A ESC.  This combination drew slightly more current at about 16A, but stayed quite cool and was barely warm after a minute or so of wide open throttle. 

So, this resolved why he lost control.  This also suggests that two other possibilities.  One is that the Hobby King brand parts (or ESC in this case) are not very good, or the other possibility is that they had a batch of much lower rated ESCs go out with the wrong labels on.  We would not have known this without the tester as we would not have been able see that the current draw was well below the rating.

Well, what does he do now?  He has two options.  One is to pursue a replacement from Hobby King and the other is to just go out and buy a more reliable brand.  Since the Hobby King ESC was only about $7, I think he will just look for a better replacement.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Can't get enough test equipment

After a long hiatus, I am finally submitting a new post.

Since my last post I have learned a lot about RC equipment and testing.  This has led me to realize that I need another servo tester, or power analyzer.  This one does not control the server under test, but reports on the servo voltage and current use.  This is very important in making sure that servos are up to the task at hand and that the battery or BEC circuit is capable as well.

You may have seen one of my previous posts about my big T28 Trojan and my crash.  I suspected that this crash was due to power issues but have had no way to test this.  With this servo power analyzer I will be able to find out what is going on with the servo/receiver power system.

What is needed for this tester is a way to measure amps and voltage used by a servo, and all the way up to all servos including the receiver.

These are the parts that will be used build my servo power analyzer.

The parts consist of an amp meter, volt meter, project box, small circuit board, connector pins, and some connector lugs.  Also needed but not shown is some wire to make all of the connections.

This is a closer view of the Amp and Volt meters I used.  The Amp meter is rated at 5A max and the Volt meter has a rating of 10 volts.  Most of these testers that I have seen are setup for 500mA and 6 volts.  I chose these values so that I could monitor a larger range of current and voltage.

Another view of the inexpensive (about $6 each including shipping!) meters I bought on eBay.  These are inexpensive, but they'll do just fine.

This is a better view of how the circuit board and pins will be used.  The pins can be snapped off in the number needed.  Since these will be used for servo connections, these will be broken off in 3s.  The circuit board will be cut in half and one half used for each end.

This is how the completed tester looks with the two meters mounted on the face.  The connectors are on each end.

These are the pins for the output or servo side.  I opted to provide two connectors here so I could hook up two servos at a time.  I could also use a splitter cable as well but this was easy enough to add.

This is the input side (sorry for the blurry photo).  There is no need for more than one input here.

This shows a typical setup for testing a servo.  With this setup I can monitor any voltage and current fluctuations while the servo is put through its paces.

The way I plan on using this to test my T28 setup, is to plug the BEC into the input side and the receiver with all of the servo connections into the output side.  Then I will monitor for voltage fluctuations (anything dropping much below 6V) and maximum amp flow.  Anything above the amp rating of the BEC will be a sign that it is not up to the task or I have a problem with a servo or two.

I realize that I did not include a circuit diagram and this would be very helpful for anyone wanting to make one of these.  It's really very basic and should be easy to duplicate.  So, here it is:

The positive voltage path flows through the Amp meter.  The voltage is measured the positive and negative voltage paths.  The servo signal wire passes straight through without interruption.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Battery of Confusion

I hear a lot of people making comments about batteries that tells me they are confused over how batteries fit into their electric airplane power system.  I decided to do this blog entry to try to clear up some of this confusion without adding any more to the subject.

I hope to clear things up by relating an electrical system to an internal combustion system.

In a simplified internal combustion system the gas tank stores energy (in the form of gasoline), a carburetor controls the flow of energy to the motor, and the motor converts the energy into mechanical motion.

In our electric airplane power systems, the battery stores the energy (electricity), a speed controller feeds that energy to the electric motor, and the motor converts the energy into mechanical motion.

The battery as two parameters that it is rated by, the voltage and milliamp hours.  The milliamp hours is a rating of its capacity, just like a gas tank capacity might be rated in gallons.  A higher number of gallons does not make a car go any faster, it only allows the car to run longer.  The same is true for batteries.  A larger milliamp hour rating will not make your plane fly any faster, only run longer.  There is another little mix to this in that the milliamp rating (multiplied with the "C" rating) is related to the flow rate.  This is similar to a gas tank with either a low or high capacity fuel pump and line.  If an internal combustion engine requires more fuel than than the fuel pump and line can supply, its power and performance will suffer.  So too, if an electric motor demands more current (milliamps) than the battery can supply, the battery voltage will drop along with the electric motor power and performance.

The voltage rating is a little different and is more closely related to the octane rating of gas.  If I have a high performance car motor and run regular gas in it, I can only expect so much performance.  The fuel mixture is only capable of creating an explosion of so much to push the pistons down.  Now if I put high octane racing fuel in the tank, I can expect much more performance.  This fuel mixture is capable of a much greater explosion to push the pistons down.  A low voltage battery can only give its rated voltage to the electro-magnets that repel the permanent magnets.  A higher voltage rated battery will allow for a larger repelling force.

Now, keep in mind, just as the internal combustion race motor is built to take greater stresses, if a batteries voltage is increased, the speed controller and electric motor must be built to take on the extra stress.

I hope this analogy will help those out there that have been confused about batteries and their voltage and milliamp ratings.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Airfield T28 Trojan Maiden Flight

I have this beautiful new new Airfield T28 Trojan and I finally have a chance for it's maiden flight!

I feel that I should note here, before I go on, that I have discovered that the Airfield name is actually a re-brand by Nitro Planes of FMS products.  Not that that's a bad thing, just that FMS T28 enthusiasts are included too!

Its Easter weekend and I will be visiting my folks near that cool park and the weather is expected to be great for flying.

Look at all those wires

We start packing for our trip and I realize that this plane is huge and would not fit in the trunk of my car (Mazda 3).  It wouldn't be so bad, but this plane is not made to be taken apart like most planes.  There are four screws that bolt the wings on from underneath.  This isn't so bad except that there are a million wires that come from the wings into the fuselage!  OK, OK, there are 5 sets of wires from one wing and 6 from the other (landing gear door, landing gear, flaps, ailerons, and wing lights) and not a million.  These are routed through small openings that make dis-assembly/assembly difficult and something to be avoided at all costs!  OK, I'm being dramatic again, but this is not trivial.  As it would happen, I did end up unbolting the wings, separating them, and disconnecting all of the connections for the servos and lights to get this big plane to fit.

Wow, this really made me think that I need to take transportation into account with planes in the future, and explains why serious RC pilots have trailers.

Once we arrived (we were early for once) I unloaded the plane into my Dad's workshop and started assembly.  Of course this was not until after we greeted them, brought in our dinner contribution, gifts for recent birthdays, and visited a little.  I'm not that crazy focused on RC planes.  Now I only had to wait for the meal to be over and for all of the other guests to leave!  I have to say that I did not really want that meal to be over because my Mom made this lamb that was to die for (hm... not sure that was worded appropriately).  Any way, it was really good.

Hooking up the battery

Snapping on the cockpit

Testing the throttle

Finally everyone is gone and I still have 45 minutes before we also need to leave.  Off to the park.  We arrive at the park.  I have to thank my daughter who rode in the back seat with the airplane tail in her face (I also have to thank her for being my photographer).  There is about a 5mph breeze, but this shouldn't be an issue.  We get the plane out and I get it setup.  Wow, it sure looks good sitting out there on the dirt runway!  I tested all of the control surfaces, I tested the motor, and then I taxied the big Trojan T28 out and around the runway.  I let her sit there for a bit off to my left facing into the breeze, giving me time to collect my courage.

Ready for take off

Leaping into the sky

I gave her full throttle and hoped to keep her straight.  Half way down I could see her wanting to take flight.  I gave her a little elevator and she shot straight up into the air.  Wow, beautiful!  I struggled to level her out and bring her around as the controls are a lot touchier that I'm used to.  Watch out, this thing can really snap around!  I eased up on the throttle and  pulled in the landing gear as I made a big loop around the airfield in front of me.  I'm just now thinking that I should start working with the trim.  I go for another loop but this time decide to try turning away from myself as I'm coming across the back field.  At this point she is downwind and about 100 yards off to my right at about a 45 degrees.

It hit about 10ft back

Dad and I assessing the damage

This is where things go terribly wrong as suddenly I feel that I have no control!  I had given more power, but she is not going any faster!  I gave her up elevator, and she is not climbing!  I gave her left and right aileron and she is not banking!  The next thing I know is that my beautiful $280 Trojan T28 is headed straight for the ground!  At the last moment she started to respond the my elevator command and pulled up just enough to avoid drilling in!  Pieces flew just before that terrible WHUMP sound reached us.  Nothing left to do but start that dreaded walk over to see what was left.

Still assessing the damage

Point of impact

Small pieces everywhere but the fuselage was intact!  So, this was bad, but not as bad as I anticipated.  We collected all the parts putting them in a bag.  Took the wing apart again and loaded it up, in the trunk this time.  No need for careful placement and handling.

Next post I hope to feel well enough to review the extent of the damages and reconstruction.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Using A Servo Tester

OK, so now admit it, how many times have you installed a servo and hooked up linkage, assuming that it was centered, only to find out it was not.  Come on, admit it, all of you have done this at one time.  Why have we done this?  Because we are all too lazy to hook everything up to a receiver and battery and to power on a transmitter.  That's why you need a servo tester.

This is the Turnigy servo tester that I found and purchased.











You can connect up to 3 servos and test them all at the same time.  There are three settings that are cycled through by the press of a button.  The default when powered up is the manual dial.  Press the button and it goes to center.  Another press of the button and now it cycles from one end to the other and will continue until you change the setting or run out of battery.  To power this little guy I purchased a 4x AA battery holder from Radio Shack and added a servo connector.  I have also used this device to test speed controllers and retractable landing gear.  For testing an ESC, no battery is needed if it has an included BEC.

The only draw back is that the LED is way too bright and blinding if you're not careful.

Here is a video showing this device in action.

For about $6 you just cannot go wrong with one of these and it's a must for any toolbox.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

Turnigy Brushless ESC Programing

Hello all,
Recently I purchased a nice Turnigy TY-P1 25Amp HEXFET Brushless Speed Controller that was reported to be programmable through your transmitter throttle stick movements.  Well, it is programmable, but I could never get any correct documentation for this one.  It also listed this Turnigy TYP1 ESC programmer as an optional item.  In my infinite wisdom, I did not buy the programmer with the speed controller.  I finally gave in and purchased it and now wish I had from the beginning.  It's small, light, and really easy to use, and really inexpensive.

 Here are all the pieces that are needed to get the programming done. I have here a LyPo battery pack for power, along with the brushless speed controller and programmer.  The first thing is to hook up the brushless speed controller to the programmer.  The programmer has two connections noted as BATT for battery and BEC.  Since this brushless speed controller has a BEC it can be connected to the BEC input and no battery is needed on the battery connection.

Once the battery is connected to the speed controller, it lights up with the current program.

To change any of the settings, use the up and down scroll button to select the feature to be changed.



Now use the left and right scroll key to select the setting for the feature that is desired to be changed.

Once you have all the settings the way you want them, use the OK button to save the settings to the speed controller.  When you do this the light above the OK key will flash blue and then turn off when done.

I really like this programmer and it certainly is small enough to take anywhere.

I added this video of me programming my ESC.

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