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1/4 Scale Balsa USA Piper Cub - Big Electric Motor Install Draw Style Unit

Posted: Sat Dec 15, 2018 1:11 pm
by Neons
Been awhile since a post. This construction article was started on October 23rd. If you research this Forum you will see that I built a Battery drawer and motor component system in the Carl Goldberg Cub and the Nieuport 28 Threads in the Electric Planes Forums in this BCRCC Threads. Here is an inherited large 1/4 scale Piper Cub believed to be built from a Balsa USA kit. The plane I calculated to be 20 to 25 years old. The wingspan rough measure was 106 inches. The fuselage is 70 inches overall. It was given to me from a large collection of model aircraft equipment to do as I see fit with it. It looked like it was in worse shape than it really was. Parts missing that I needed to finish the plane. The nose cowling was missing. I researched and talked to Balsa USA and described so measure and telltale marks on the plane with there tech builder. I ordered the plastic cowling for trials. The numbers were used on a smaller Piper Cub alongside the big Cub leaning against a covered motorcycle in the photo. I ordered the registration numbers from World Models with other Cub decals. The motor and mount is High Voltage powered. That will come up below in this thread. Electronics finish up later also.

I peeled back some covering to look at the construction. The plane was not amateur built and was very well put together with solid glue joints. The yellow color (Fabricote maybe??) was very dirty and it was all coming unbound all over the plane in large stretches. I tested ironing a section back onto the wing and it did reattach itself quite well using plenty of heat while I stretched it with spring clips and pliers. I rebound the whole plane over a couple of days. In the first pictures you may see that the fuselage has loose skin behind the cockpit to the elevator. The plane assembled together for the overall look had the wing skins taped down with yellow masking tape for the picture.

A new video is uploaded to YouTube on 9-19-2019 ...

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Re: 1/4 Scale Balsa USA Piper Cub - Big Electric Motor Install Draw Style Unit

Posted: Sat Dec 15, 2018 1:16 pm
by Neons
More views of the plane as I received it.

Re: 1/4 Scale Balsa USA Piper Cub - Big Electric Motor Install Draw Style Unit

Posted: Sat Dec 15, 2018 1:25 pm
by Neons
Nov 9,2018
Okay. The Turnigy Aerodrive SK3 - 6364-213KV came in from Hobby King.This is a 160cc gas equivalent rated motor. It will use a 20x10 wood propeller. I am going to start my flight with a 19x10 prop to feel it out. It is a low RPM motor @ 213Kv. This allows for the large props. I should mention that this will run on 5s x 2 -4000Mah Lipoly batteries connected together in parallel to produce around 45volts. I can also use 2- 4S batteries on a lower voltage around 36volts if I want too. This is all trial and error later on after a maiden flight. I will check the ratings of Amp draw and Watts produced with my What-Meter first. As you can see it is a large motor. I taped the half cowl and held the motor nearby to just get an ides how far from the firewall I would place it and then find a mount for the motor.

The first thing I want to do is cut the airplanes firewall to build an insert drawer for the electronic ESC, Bec, and the large batteries.

Re: 1/4 Scale Balsa USA Piper Cub - Cut the original Firewall

Posted: Sat Dec 15, 2018 2:37 pm
by Neons
I have no plans so I had to research where the motor centerline was going to be before making any cuts. There was a flat horizontal balsa plate near the top about 1 inch down. That was going to be the top cut. Then I took 2- 5,000Mah lipos to get a height and width to determine how wide to make the slide in drawer. The height was not as important as long as I could have plenty of useful clearances. The height also allowed me to make a horizontal and rectangle cut for bottom air to enter the battery compartment.

Made all the measures and drilled some corner holes and sabre sawed the firewall mods. Next was to cut an existing bulkhead former out to a similar hole. I used long drill bit again in the corners and an old blade hacksaw tool to tediously do more cutting for the break through. The next tool was using a Dremel with cutting burrs and drum sander to get it smoothed out some. The next step was to trace a new 1/4 inch aircraft plywood firewall to attach the motor and components. The box drawer will be attached to this with blocks, screws, and epoxy. In the meantime I found a steel adjustable motor mount for the motor

Re: 1/4 Scale Balsa USA Piper Cub - The Battery Box and Motor Mounted

Posted: Sat Dec 15, 2018 4:04 pm
by Neons
Nov. 20, 2018
After the cutout and sanding and filing the edges Built the battery tray with different pieces of plywood. It has a double bottom of 1/2 inch with drilled and sanded holes to allow air to pass from beneath and the sides to the battery to help cooling. Against the firewall and the tray after epoxy was applied I added screws inside behind the new fire wall and on the front firewall into the blocks. In the rear of the tray there is slots to accept a Velcro band to strap the batteries in place.

The motor was aligned and mounted in place with 4 blind nuts. I installed a new YEP 100 amp High Voltage Esc motor speed controller that handles up to 50volts and 12S configured Lipo batteries. Not seen at this angle other than the safety plug red wire.

Re: 1/4 Scale Balsa USA Piper Cub - Drawer Guides and Lockpin

Posted: Sat Dec 15, 2018 4:35 pm
by Neons
Nov 12, 2018
After some trial fits to make sure it slides in and out properly I had to make a bottom and side guides so the draw goes in place straight. Two wood guide o each side and a bottom plate the has holes for air aligned with the drawer tray. Now that the tray fits I determined to put the locking pin right at the same level as the motor shaft. I used a sharpened landing gear wire as the drill for the pilot holes after care was taken to get it straight though and across the drawer tray. I only drilled through 95% of the way. I then fitted a length of brass tubing in place cut in a few correct length pieces. They were CA glued in place. Insert the drawer and pass the wire in place and it is locked now.

Re: 1/4 Scale Balsa USA Piper Cub - Motor and Esc Mounted

Posted: Sat Dec 15, 2018 5:05 pm
by Neons
Nov. 20, 2018

Looking at the front you will see the HV 100Amp ESC is behind the motor and bolted to the firewall. The red wire is cut and I used a shorted Deans connector plug as a safety pull plug. That is temporarily hanging off the side.

Motor Test with 19x10 prop. 10s lipos

Re: 1/4 Scale Balsa USA Piper Cub - Cowling assembly

Posted: Sat Dec 15, 2018 10:33 pm
by Neons
Nov.23, 2018

Now I get to the cowling bonding and painting. The 2 halves were glued to get with a doubled plastic inside the cowling. The seams were filled with Spackle and smooth sanded. Careful fitting and lining the hole for the propeller shaft back plate clearing. The motor was set with a degree right and down thrust to counter act torque issues. The 4 screws secure it into a beam mounted against the outer firewall for fastening. The beam also holds the Safety pull plug in place. With the cowl all in place you see the assembly pin on the end of the Safety plug chain. Air intake and the dummy motor is all secured in place. The yellow color matching is near perfect using water base paints tinted.

Re: 1/4 Scale Balsa USA Piper Cub -The Motor, ESC, and Bec finished

Posted: Sat Dec 15, 2018 10:47 pm
by Neons
Nov. 30, 2018
This is the finished components laying on it's side. The small rectangle is a 20 amp Bec. A Bec is a battery eliminator circuit. It is a backup system that will allow me to fly the plane into a dead stick landing should the Esc or motor quit. The Esc is an electronic speed control for the operation of the motor. The beams for the cowl and the Safety pull plug is visible. The whole business end is done and ready to mount.

To zoom in any photo, use a single or double click

Re: 1/4 Scale Balsa USA Piper Cub - Wing Mounting

Posted: Sat Dec 15, 2018 11:04 pm
by Neons
Dec. 9, 2018

Evidently the wing struts were all put together to put in a large amount of dihedral. For those that do not know it is the upward angle lift of the wing. I had to cut an inch off the strut bottoms to get al but maybe one degree dihedral out of the wing plugs. The actual Piper Cubs have a flat wing. But in modeling a degree is okay. I assembled the wing halves with thumb screws to speed up assembly. So once the wing was all set I installed all the servos and the push rod ends of the ailerons with ball joints to eases assembly. installed all the servos with a servo tester that also tests the operation and can center the servo to neutral for the transmitter. I tuned it all in to my transmitter and it is working well.

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