ORIGINAL: vmsguy

Date: September 27, 2008

My work started today with continuing the battery box. As I feared, I couldn't wiggle the battery box through the hatch. (Picture 1). So, I removed the top piece and cut down the sides a little on the front half, and continued to fit it into the fuselage. (Picture 3) I eventually had it positioned, and I thought it would be good to test a battery. It was a tight squeeze, but the battery fit. Too tight, in my opinion. (Picture 4) I want something where I can easily swap batteries while at the field.

To fix this, I decided to use thinner balsa on the side walls. I was using 1/8'' sheeting. I build a new box, using 1/16'' sides. This will gain me 1/8'' total width for the batteries. Once the box is properly in the fuselage, I can add extra thickness to the outside if I feel I need it. Thinking it over, I really doubt I'll need to. After all, I have the main bulkhead holding this box in place.

One thing I noticed with the first box in position, was the side of the box covered the access to the receiver. (Pictures 5 and 6) I haven't decided how I'll handle that little surprise. I might just move the receiver a little. I don't know yet.

I went back to the drawing board, or in my case, the band saw, and cut new pieces. This time, the sides are 1/16'' thick. Otherwise the box is the same as the previous verstion. It fits in the bulkhead quite well, and the batteries slid into place easily. (Pictures 7 and 8)

Now that I have a working battery box, I started to think about how to secure it. I also needed to think about what to do about the receiver battery. While some ESC have battery elimination circuits (BECs) I prefer to have a separate battery for the receiver. This allows me the safety of having radio control, even if the motor/ESC/battery fails.

After some thought and looking at the plane, I believe the best place for the receiver battery is under the battery box behind the second bulkhead. Then the idea struck me, why not make the battery box removeable. All the problems the box introduced are solved. With the box removed, I can access the receiver wires, And I can access the receiver battery. Once the battery box is in place, I can swap batteries through the hatch.

I guess I'll be reinforcing the thickness of the battery box in the front after all. I started by adding a bit of basla the bottom/rear of the battery box. Next, I figured I really didn't need the first inch or so of the box. It doesn't matter if the batteries extend a little from the front. The velcro will hold the batteries from sliding forward. So I removed that inch. (Picture 9) The box goes into the fuselage a lot more handily, but upon testfitting, I found the small tab I glued onto the bottom and made the box too tall to fit through the bulkhead.

Oh well, onto version number three. This one, I built a bit differently, I included the mounting tab into the bottom piece. I also made the bottom piece narrower, and glued the sheets to the side. The first to versions had the sides butt jointed to the top of the bottom piece. This will be a stronger joint. While the glue dried, I started work on the battery box mount. First, I cut a cross brace. In the picture, pointed to by the red arrow, you can see the cross brace sitting in place. Behind it, you can see the receiver battery sitting in place. (Picture 10)

Next, I continued on the cross brace. I doubled the thickness of the cross member, then drilled a 1/4'' hole through it. On the bottom, I glued a block of threaded wood. (Picture 11)

Finally, the glue dried and I can shoot pictures of the completed battery box. You can see the mounting tongue out the back, as well as the glued together top. (Pictures 12 and 13)

Picture 1: Battery box going in through the hatch opening.
Picture 2: First attempt of battery box. (Kinda fuzzy)
Picture 3: I lowered the front of the box so it would clear the windshield. I Still need to cut the far side.
Picture 4: The battery box in place. But battery is a tight squeeze.
Picture 5: The battery box blocks access to the receiver wires.
Picture 6: The battery box blocks access to the receiver wires.
Picture 7: The second battery box, with thinner sides, fits just as well.