Sean Plummer

For quite some time I have been planning on converting a Large scale aerobat for IMAC type of flying. I chose the http://www.composite-arf.com 2.3m EXTRA 330L. The Model was ordered with custom paint applied in the mold. This model is all composite construction and beautifully painted. I will do my best to detail the conversion online, as time permits.

I plan on using 2ea Hacker C50 Direct Drive motors and the Inner Demon Gear reduction for power.

90" Wing Span
20-22 LBS AUW with 50cc gas

-Sean

rm

My Feedback: (27)

Can these gear drives handle the heavy practice sessions put in by guys competing in IMAC? 3-4 flights/day 4-5 days/week, some a lot more. What size packs do you think you'll be using? What's your total watts goal? I've considered doing something like this but leary if the drive could hold up.

Sean Plummer

Hello rm,

You ask a very good question, I will be using the newest Inner demon drive, that is larger and features a Teflon Coating on the ring gear and pinions. I hope this model will be capable of many flights, before gear drive parts need to be changed.

Total watts target is 4200 input. I will use 2 sets of 10s3p Thunder Power.

-Sean

Sean Plummer

I started with the motor mounting as this will need to be in place prior to the battery tray installation. I usually do this so a C/G location can be defined early in the conversion allowing all components to be located correctly.This model has a molded motor dome type of firewall, that has the proper thrust angles built in. Using the mold marks as a reference the thrust centerline can be determined as shown in mm. Next a piece of 5/8" thick Aircraft Plywood is used to form the Gearbox mount. Please note the holes drilled into the gearbox mount and motor dome must be square using a tilting table drill press and level. I also used a small 3mm allen screw as a center reference before the Gearbox mount holes are drilled. The Gearbox mounting holes and motor wire slots are now added.

Sean Plummer

Next the 10/32 Blind Nuts are installed (Supplied with the Inner Demon Gearbox- http://www.innerdemon.com/). Using the Gearbox mounting feet/tubes from the Inner Demon Gear box, Spacers are fabricated to provide the proper Prop Hub spacing for the spinner/prop and cowling clearance.
10/32 Allen cap screws and Nylock nuts are used to mount the Gearbox Plate to the Motor Dome

Sean Plummer

Next the pinions must be installed onto the motor shafts. Following the the Inner demon -32 instructions, the Pinions are pressed into position using a drill press. Please note the 3mm allen cap screw is used to press the back of the shaft of the motors (Note: the label on the Hacker motors must be cut/removed to directly access the shaft as shown). Be sure to use the supplied "Green" loctite to help secure the pinions to the motor shaft.

Sean Plummer

The Gearbox mounting plate is now secured to the Motor dome using the spacers and 10/32 allen caps. The Hacker C50 16XL motors are now mounted to the Gearbox/mounting plate. Double check the spacing to the front of the cowling to ensure proper clearance for the spinner/prop.

Shown is the New Inner Demon 32-TEF Gear drive, This has been developed for these large high power applications (4000 watts!) Available at http://www.innerdemon.com/

This mounting method is very strong, and will allow the model to be flown in freestyle/3d fashion. One of the most common mistakes in large aerbatic electric conversions is improper motor/gearbox mounting. The g-forces during spins and tumbles are huge. Saving an ounce here or there is just not worth it on these large models.

Henke Torphammar

Looks really nice! will be fun to se how the weight compares to Rob´s 2.6meter plane. how long lifte time do you expect on this gearbox?

Aren´t there any larger planetarys, thinking two motors inline on a common shaft, maybe there is a market for a double XL motor with two C50 winds in a row

ROMANBM

I like to install electric in my von extra 260 35% wich is realy light it weight 22 lb with DA 100

Sean Plummer

Hi Roman,

Thanks for the reply. The 35% 260 should be an excellent choice for this power system.

Hi Henke,

As mentioned before, I hope this system is capable of many flights.

-Sean

Sean Plummer

The cowling is mounted next as per the instructions. I am using the Tru-Turn Light spinners http://www.tru-turn.com/. I used 3.75 inch "P-51" spinner for lower weight, although the instructions recommend 4" diameter.

I have also installed the 26x15 APC-E prop http://www.apcprop.com/. These props are relatively new and provide huge amounts of thrust for electric applications.

Sean Plummer

Next move to the landing gear as these will have substantial affect on the C/G. The landing gear are Carbon Fiber. Install into the model, as per the instructions. I used the DuBro 4" "Treaded Lite" wheels. Please note the hole that is drilled into the outside of the wheel pants to aid in tightening the allen cap axle/bolt.

Sean Plummer

All hinging for the Rudder is pre-installed, simply follow the instructions.The hinges use a steel wire that is removable! and allows the rudder to be removed for transport.

The supplied rudder servo tray is designed for 2ea standard servos, I have decided to Use a single New Futaba Digital S9152 servo http://www.futaba-rc.com/servos/futm0211.html. This servo weighs 2.6oz. and has 277oz torque.

I modified the servo tray as shown, using the parts as supplied in the kit.
Be sure to use slow epoxy, and clean all surfaces with alcohol prior to gluing

Also note Large Stock Futaba servo horn. I used the Pull-Pull system as supplied in the kit. The supplied Rudder horn is glued into position as per instructions.

Sean Plummer

Install a steerable tailwheel, assembly. A tailwheel is not supplied with the kit. I chose a Graphtech http://www.graphtechrc.com/ all carbon assembly, it is very light weight. The fuselage already has the plywood mount installed. Simply drill through the skin into the plywood and use the supplied wood screws to secure the assembly. Connect the steering springs to the Pull-Pull rudder horn.

Sean Plummer

The stabs are next. This model uses plug in elevators with dual servos, the tube and anti-rotation pin is already installed. Check alignment as per the instructions. The Elevator servos are designed to be installed inside each stab half. The installed servo mounts are designed for standard servos, I have decided to use the New Futaba Digital S9451 servo http://www.futaba-rc.com/servos/futm0211.html. This servo weighs 1.98oz. and has 120oz torque.

The openings in the stab root rib need to be opened up a little to install the servos. I used a file wrapped with adhesive backed sand paper to accomplish this. Check the fit of the servo into the servo mount, adjust as necessary.

Sean Plummer

Remove the servo and drill a hole into the "Servo Rib" so the servo lead can exit. Using string and a wheel collar thread the string through the rib and back out.

Sean Plummer

Tie the string to the servo connector and pull through the rib.
Mount the servo into the servo mount using servo screws. I used DuBro heavy duty servo arms for the elevators. Note: Turn the servo arm sideways as shown while installing the servo.

Sean Plummer

The supplied elevator control horns are now glued into position as per the instructions. Alignment jigs are fabricated from scrap plywood and insure precise and equal control horn placement. This step is critical to produce a perfect tracking model. Secure jig/horn into position with masking tape while the epoxy cures
Note: Use slow cure epoxy, and clean all parts with alcohol prior to gluing.

Sean Plummer

The elevators are pre-hinged and simply need to installed using the steel wire as per the instructions. Install 4-40 pushrod/clevis hardware and check that elevators operate properly with NO Binding through the entire throw range. Note: Binding can cause very large current from the Receiver battery resulting in a crash due to a dead receiver battery.

The removable elevator halves are connected to the model using allen cap screws, drill through the stab into the aluminum joiner and use a Tap to thread the tube as per the instructions. repeated on the other elevator half.

schroedm

My Feedback: (1)

Sean,

Is the InnerDemon 32 on their website the same one you used? It states it is for 2 x B50 motors - are the B50s the same size as the C50 and can the Inner32 take the extra grunt of the C50s over the B50s reliably?

Thanks,
Mark

Darrell B.

Wow Sean,

What a sweet conversion. With this drive I realize that you are gearing it for thrust. If I were to go with higher turn C50s say 10 or 11XLs, and a 21x14 prop, and lets say 5s or 6s lipos, what do you think that the pitch speed would be?

This conversion is taking shape fast. I looked on the inner demon site, but they don't list the new drive, only the old 32. I guess that I need to place a phone call to ask them about the new one.

This looks like the answer to my power needs in the Top Flite P-51. I am almost ready to order a drive for it, and this is the way I am leaning.

How much maintenance do you think this drive is going to take?

How is your Hanger 9 P-51 holding up?

Thanks,
Darrell

Henke Torphammar

21" would be too tiny for this power your P51 should use atleast 24" if going for twin motors.

If I remember right it goes like 125mph on 2.5kw 21", thinking you would waste lots of power if spinning the 21" faster... would give way too high pitchspeed I think.

Sean Plummer

Hi Mark,

The Inner Demon 32 -TEF, is the part I am using it is very new and available from Inner demon direct. This geardive has been developed using the C-50 motors and should work well.


Hi Darrell,

Stick with a single Hacker C50-14XL+6.7 Acro motor. Use 10S4P Thundr Power and the master 90-O-Acro controller with an 21x14 APC-E Prop this will fly your P-51 with authority( Better than Saito 180), only limit is you must fly with mixed part and full throttle, as the system will pull 65 amps WOT.

Best Regards,
Sean Plummer
http://www.hackerbrushless.com/

Sean Plummer

Next the Aileron servos, The wings use a removable "hatch" for the aileron servos. The model can use 1 or 2 servos per aileron, the kit includes servo mounts for standard size servos.

I have decided to use a single New Futaba Digital S9152 servo http://www.futaba-rc.com/servos/futm0211.html for each Aileron. This servo weighs 2.6oz. and has 277oz torque. Using this single High Power servo will reduce weight and provide ample power for the ailerons.

The aileron servo horn is mounted like the elevators, and an alignment jig is fabricated to ensure equal aileron throw. I fabricated the servo mount using hardwood and plywood, use Slow Cure epoxy to glue the parts together. The large futaba servo arm provided with the servo, is perfect for this application. Screw the servo plate to the wing as per the instructions.

Sean Plummer

With all basic components completed it is now time to fit the motor battery tray. Assemble the model and mark the C/G position on the wing. Place the motor battery into the model and move until the proper C/G is achieved. Try to position the battery as close to the centerine of the model as possible to reduce potential coupling issues. In the case of the 2.3m Extra, the batteries ended up protrudng in to the Motor dome and across the Wing tube. In this case the battery tray is positioned so the batteries cross the centerline of the model from front to back.

Fabricate a strong battery tray from, 1/4" "lite ply". This is a really important step as the batteries will represent about 20% of the models weight. A very strong battery tray will ensure the batteries will not shift during flight and also "Protect" them in the event of a crash.

I have seen batteries ejected and destroyed from crash impact. If the batteries are properly mounted they often sustain no damage, as the airframe absorbs the impact in the event of a crash.

Here are the first pics: