Wednesday, March 9, 2011

Landing Gear Struts On The ParkZone T28

I recently purchased a Parkzone T28 from Horizon Hobby. All I can say is WOW! What a fun model to fly.

As seems to be typical, as soon as I bought this jewel the weather went South as we had nothing but rain and high winds for a month or so. Being as I love to tinker with stuff, I decided while I was grounded I would do some modifications to the landing gear. I started by adding plastic strut covers to the nose and both main gear. They are very easy to install and really add some scale detail to the spindly stock wire struts.

I started by ordering Robart part #106 from Tower Hobbies. These covers  required that I trim a little off the top of the main struts and only a inch or so off the nose gear one. At first I tried to use the original wheels, axles and retaining nuts, but the covers reduced the axle length and I felt there was too much binding and the retaining nuts could not be threaded on enough that I was sure the wheels would not come off in air. Because of this I chose to extend the axles by soldering on a length of 1/8" brass tubing over the stock wires. I then used two round retaining collars to secure the wheels.

To the left you can see the axle extension. I had to take a Dremel tool with a sanding drum and sand down the wire axle slightly to get the brass tube to slide over it. This resulted in a tight fit and with a bit of solder applied to finish things up, I don't have to worry about the axle coming off. Once the axle was done, I mounted the covers. It takes a little finessing to get the retaining rings and cap over the covers, but it can be done where there is very little gap between the top of the cover and the bottom of the wing.
To the Left you see one of the main struts after it has been painted. Also notice the inner retaining collar which helps keep the strut cover aligned and secured. The collar also acts to keep the wheel from binding against the strut cover. For a finishing touch, I added a small strip of chrome tape to the center section of the strut to give it the appearance of a hydraulic piston that you would see on a full scale strut.

I also changed out the stock wheels to 2-3/4" diameter Dubro lite wheels as I will be flying her off a grass runway. One final item I did on the main gear was to apply packing tape over the plastic plates that hold the wire gear to the wing. I've read that these plates are known to pull loose on a hard landing. Many suggest you pull the plates off and re-glue them to the foam using epoxy but as mine seemed pretty secure, I chose to tape them Scotch® Extreme Tape for now.

This stuff has fibers running both directions and is as tough as they come. Great tape for any RC repairs.

All in all I'm quite pleased with this modification. The struts look great and the larger wheels are excellent for use on a grass field.

Radian Pro Wing Modification

This is by far the best modification I've done to my Radian Pro. The idea came about after suffering the frustrations encountered while assembling the wings of the Pro. You have to fish servo wires through the wing openings, then take a pair of pliers and grab the wire ends and pull them up into the radio compartment. You have to do this for both the flap wires and aileron wires. Anyone who has ever done this knows how much a pain in the ass this task is.

After doing this chore a few times, I vowed to find an easier way. First I tried making a a wire lasso that I could put down through the radio compartment and out through the wing slot. I then could lasso the aileron and flap wires and pull them up for attachment to the receiver. This works better, but still not a perfect solution and had me worried I would wear out the pins on my receiver as they are not designed for this kind of abuse.

After questioning others on how they dealt with this issue, I decided the best solution would be to take two servo extensions, Plug one into the receiver for the left aileron, the other to the left flap and then remove the connectors on the other end of the extensions and incorporate both wires into one plug, a deans four pin connector.

I would also have to remove the connectors from the wing servos and shorten those wires, adding a matching four pin connector to those wires as well. Once done, I was able to slide the wings on the spar up to the point they enter the fuselage, plug in only one connector, finish sliding the wing and bolt it up. Do this for both sides and I'm done.

 Here is a photo taken during the process of soldering both servo extensions to the four pin deans. I purchased the connectors from Horizon Hobby and they come with the shrink tubing shown.

Notice how both red(positive) wires are added to one pin of the connector and both black wires are soldered together and ready to be attached to a single pin of the connector. The other two pins will have a signal(yellow or white) wire attached to them, one from the flap channel and one from the aileron channel. In order to strip the wires back for soldering I take a #11 exacto blade and just lightly nick the wire insulation about 3/16" back from the end and then take my finger nails and pull the rest of the insulation off. If you plan on doing a lot of servo work you could invest in a set of wire strippers that will do 22-30 gage wire. I believe the wires on the Radian Pro are 22 gage. For the soldering I used this 30 watt iron from from Radio Shack. I would have liked to have something with a smaller tip and a little less heat, but I was able to accomplish the job with the Radio Shack iron. If I run across any other servo wiring job in the future I will more than likely buy this soldering iron.

You will do the same thing for the the connector that you add to the servo wires in the wing. Start by peeling back the tape that covers the wing wires by a couple of inches. Then lay the connector on the wing so that the pins extend past the end of the wing. Now cut your servo wires so they are the right length for your connector in this position. Then you will need to take an exacto blade and cut out a small area of foam so that the connector lays flush with the surface of the wing. Once this is done, strip back your wires, twist both reds together, both black wires together and then tin all four wires with solder. Before you solder the wires to your connector, be sure to slide a piece of shrink tubing over the wires prior to soldering them to the pins.

While this modification involves working with and soldering small servo wires which can be a bit tricky, in the long run I found the time invested to be well worth the effort. It's much easier to assembly and disassemble my Radian at the field.

Here is a wiring diagram of the deans 4 pin connectors used in this mod. The colors reflect those found on the RP wing servo wires. The servo wires I used in the demo are Hitec extensions that are coded: Red(Positive), Black(Negative) and White(Signal)

Click Image for Larger View