|
|
|
A Step-by-Step Guide for Converting the Free Flight "Lightning" to R/C using the RFFS100 Module (by Greg Covey)
This step-by-step set of instructions includes many pictures that will help you to convert your own electric free-flight Lightning, also known as a Graupner Micro Taxi (shown above) to R/C using the combo package (LTRFFSKPLP) from Dynamic Web Enterprises. You can click on any picture for a larger view.
The LTRFFSKPLP Combo package includes:
With slight modifications the Lightning makes a great flying 1.3oz ARF for the RFFS-100. All you need is a transmitter. Let's get started! Step 1: Charging Station Removal and Cell Replacement
Remove the charging station from the bottom of the plane. Replace the single 270mAh NiMH cell with the new 140mAh LiPoly cell and hold in place with foam. I used a piece cut from a GWS R4-P Receiver case.
Replace the thicker wires used on the stock charging station with thinner (lighter) wires. Spare wire from the RFFS100 module kit works great! Step 2: Motor Removal and Replacement
Remove the stock (current sucking) motor from the plastic housing. This motor draws too much current for R/C use and can be discarded. I used a pair of pliers to twist and pull on the shaft and bushing sleeve while holding onto the nose of the plane. The motor should break free from the glue holding it to the plastic housing with a little tugging. Cut a small piece of servo tape and use it to hold the KP-00 motor to the side wall of the plastic housing. The motor wires can feed through the existing holes in the rear of the plastic housing. They will be connected to the RFFS100 module later. The module will reside in the center of the fuselage. A slight downthrust can be used but a neutral thrust line also works. Step 3: Rudder Installation
Cut the rudder from the vertical stabilizer as shown. Install the coil actuator using a small amount of 5 minute epoxy so that only 1/2 of the coil resides in the vertical stabilizer. Install the rubber hinges into small pre-drilled holes in the vertical stabilizer and glue with epoxy. Position the rudder for proper placement of the holes for the rubber hinges and to cut the 1/2 circle opening for swinging around the coil. Glue the rudder using 5 minute epoxy and leave a 1/8" gap between the surfaces. Hold or tape in place until dry. Finally, mount the magnet to the rudder by sticking the wire through the foam surface and loop it back into the opposite side of the rudder so that the magnet cannot rotate even before gluing. Glue in place on both sides with a tiny amount of epoxy. If the end result seems a bit stiff when swinging the rudder back and forth, you can gently tug on the rudder a bit straight back to slightly stretch the rubber band hinges. This frees the grip of the epoxy from the rubber hinges near the foam surface. A few gentle tugs usually makes the rudder swing freely. Step 4: Elevator Assembly
Cut the elevator from the horizontal stabilizer as shown. Reinforce the small gap in the middle of the elevator with a little epoxy brushed along the bottom white foam. Only a small amount is needed, if any, since the forces on the elevator are very small. Reinforce the narrow channel of the
single piece elevator with a tiny bit of epoxy for some added strength. Then
widen the "U" channel in the stock elevator a bit and slice out a section of the
rear fuselage and a thin wedge of the tail dragger. If you angle the cut as
shown above, it is a few simple slices. The tail dragger stays plenty strong and
the elevator is allowed to move upward and downward when in position. Step 5: Hiding the Actuator Wires
By cutting small holes into the fuselage (as shown), both sets of wires can be cleanly routed into the fuselage for connection to the RFFS100 module. The small pieces of foam can then be glued back into place with epoxy of aliphatic resin or white glue. Step 6: Mounting the Wing and CG
The wing is easily mounted using the stock sticky back tape provided. First peal all the papers off of the wing and fuselage before mounting and then position the wing perfectly using the guidelines provided in the mold. Finally, stick the wing struts in place and note that the CG resides just behind each strut. Step 7: Installing the Charging Station
By cutting out a portion of the foam bottom, as shown above, the charging station will fit in between the landing gear plastic block and the motor housing. Install wires from the switch and minus terminal that are long enough to plug into the RFFS100 module in the middle of the fuselage.
Placing the charging station up front provides a proper CG and allows for convenient access for recharging. The landing gear can be pressed into place at this time or as the last step if you prefer. Step 8: Wiring the RFFS100 Module
Connect the 2 motor wires, 2 charging station wires, antenna, and magnetic actuators. If the control surface is reversed, you can either swap the 2 wires at the module or reverse the channel setting on your transmitter. If the elevator and rudder use the wrong stick movement, then swap the two sets of wires at the module. I used another piece of GWS R4-P receiver case foam to hold my RFFS100 module in place. Servo tape will also work but use a small piece. This completes the model assembly. Step 9: Charging the LiPoly Cell
To charge the Lithium Polymer 140mAh cell, you need a limited current of about 100mA and a way to detect a shutoff at 4.2 volts. While this can be done manually, it is much easier to purchase a charger that will do the job automatically. I have used two different chargers that work very well to charge this LiPoly cell.
Step 10: Pre-flight Check
Always turn on the transmitter first and make sure that the antenna wire is connected to the RFFS100 module. The magnetic actuator coils will play a brief tune on power-up and then be ready for control. Typically, the KP-00 motor will initially turn on during powerup for a brief moment. Sometimes a second short burst of motor on is also noticed. This is normal. Check that the control surface turns properly with the stick changes or reverse the settings. When the magnetic actuator is properly centered, it will produce less noise than when it is offset. You can often determine proper transmitter centering by listening to the drop in noise level. Then you can bend the magnet or wire holding the magnet so that the control surface is properly centered. Sometimes you may have to offset your transmitter trim setting to obtain a good trimmed surface. Check the throttle control for proper operation and that the prop is spinning in the correct direction. The prop should spin counter-clockwise when looking at the plane from the front. The airflow will also be blowing toward the back of the plane. Ready-To-Fly (RTF):
Have fun with your new micro model and don't be afraid to experiment with it. I replaced the stock wheels with "lite" wheels from Todd's Models (EPW25). These wheels spin better and have a little bounce in them for shock absorption. The model is only 1.3oz when RTF so it can take a good hit from the ground and stay uninjured. Sometimes, the spur gear dislodges from the pinion gear upon impact and it will simply snap back into place. Often, the fragile wires holding the magnet will get mangled upon impact and need to be bent back into position. I typically use my fingers while the unit is still powered to realign the magnet.
You don't need full power to fly this model so remember that you can slow it down a bit by reducing the throttle. If you decide to eliminate all the plastics during construction including the charging center, your model will weigh even less and exhibit more power. Have fun with your new micro-flight design! It will be a rewarding and learning experience that you can use to enhance your R/C skills to a new level. |
