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.

Airplane Hang Ups

I have this really cool Airfield T28 that I munched (on its maiden) and just recently put all back together.  Its been sitting around just waiting for hanger rash.  To resolve this, I decided to build something to hang it from the ceiling of my garage.

I didn't want to string it up with any sort of cord or wire and risk dents in the foam so I decided to come up with some sort of PVC rack.  I have seen various renditions of this on the Internet and decided to assemble one of my own.  Incidentally, I put this all together from spare parts I had in my garage (that cheep Dutchman coming out in me again).

To put this together, I started with a rough plan and measurements.  I estimated how far apart the support sections needed to be to come within the landing gear and still outside the fuselage.  Then I also made allowances for the wing width for the length of the supports.  For the drop sections, I figured that I would need enough length so that neither the canopy or the rudder would hit the ceiling.  I put this all down on paper (a bill envelope, I'm sure we all have those easily on hand) and mulled over what fittings I would need.

With the length of 3/4 inch pipe I had on hand and the fittings, this is what I came up with.

I didn't have enough elbows so I used T fittings instead for the top cantilever piece and to connect the support arms to the drop sections.










You can get a better idea of how the T fittings were used as elbows from this angle.  Also, since I had two 22 1/2 degree elbows, I decided to use them for end caps.  It's not like the plane would slide off without these, but I just thought it looked better.

Here's what it looks like setting near my plane.  These two pictures were taken before I cut down the width of the top.  You can see that the down sections are squeezed together at the bottom to fit in between the landing gear.  I cut out a half inch from each of the short sections at the top to resolve this miscalculation.

From this side view you can see that it should support the wings just fine and give enough clearance for the rudder (once lifted up).

Here's what it looks like mounted to the ceiling in my garage.  I used plumbers tape and molly screws to secure everything.

At this point everything is still dry fit together.  I figured that if I can't pull it apart to glue it, it ain't comin' apart!

Now it's all safe and sound out of the way of everyone and there should be no problems with hanger rash.  That is as long as I don't need my ladder out of the garage again.

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.

Wild Hawk Flying Fun

This post will be a double post as this post will serve both my Wild Hawk blog and RC Flying Fun blog.  How you ask?  Well, I found a new place to fly and I flew my Wild Hawk for my first outing at this location.  This is also the first time flying for me in several months.  Wow, a person can sure get rusty!  This new location is on a road stub near an abandoned mall construction site.  This road stub is off of the main road and across from the abandoned mall.  It is also surrounded by farm land used for growing hay.  There is a small group of flyers that get together each Sunday at this location.  One of the best features of this location is that it is only about ten minutes from my house.
why did I pick a place like this instead of a formal club with a real runway and amenities.  Well, I already joined the AMA (I recommend this membership for everyone in this hobby) and money is really tight right now (you folks with kids in college know what I'm talking about).  So funding my hobby and paying club dues and AMA dues is out of the question.  This site fits my budget and still gives me a good group to associate with.
Any way, here are some photos of this location including pictures of my Wild Hawk airplane getting ready to fly.

I did have an accident and crashed hard after failing on an outside loop.

It looked bad but I was up and flying again after some minor repairs and a battery swap.

I flew all three of my batteries this day.  The only unfortunate thing was that on this day there were no other flyers that showed up.  I had a good time anyway and could fly and land anywhere I pleased.

Before publishing this post I got a chance to fly again and made a video from one of my flights.  Enjoy this areal look around.

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.

Trojan T28 Canopy Repair

Initial damage

 There is one final issue that I have not resolved yet in the reconstruction of my Airfield Trojan T28, and that is the canopy damage.  When my plane crashed, the canopy was ejected into the propeller (just before it completely shattered).  One of the propeller blades ripped through the front shattering it.  Fortunately it was still in one piece.

OK, it's in one piece, but how do I fix it?

Some Google searching came up with a solution that I decided to try. This solution involved using tape to hold things together while thin CA glue is used to repair the cracks.

Another view of the tape

Taped up

So, here I go.  These two photos show the clear tape that I used to cover and hold together the cracks.  The tape also allows you to see better the extent of the damage.

CA applied

Finished product

It's maybe a little hard to see in the photo on the left, but all of the cracks have been run over with regular thin CA glue.

The photo on the right shows the finished product after the tape has been removed.  Yes, it does look like it has been welded together, but it's together!  There is also some clouding of the plastic near the glue (you can see a little of it covering the pilot), but I should be able to buff some of it out.

While this appears to have worked very well there is one thing that I would do different.  If I have to do this again (and I'm sure that I will), I would tape it on the outside and glue it from the inside.  Why?  Well, the taped side left a nice smooth surface (surprisingly, the glue did not stick to the tape) while the glued side, well, feels like a raised weld seam.

Any way, I'm still very satisfied with the results.  Especially since it saved me from buying a whole new cockpit (plastic, foam, and pilot).

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.