TARPN Mod Box

This box is custom made for expandable TARPN Nodes. It is called the “Mod” box because you can start with just two and add as many more as you need. Also, the Base box (containing the power supply, Raspberry-Pi, fuse box, ground block, and PowerMan board) and the radio box (containing radio and TNC-Pi) are only different in small ways. This design is currently the 7th box design and the 4th I’ve designed. It is the result of many steps of trial and error, so deviate at your own peril. Note that in these instructions, all directions are from the perspective of looking at the box from the front.

Materials List
4′ x 8′ sheet of 1/2″ sanded plywood primed on one side. I use Lowes Top Choice Blondewood 1/2-in Whitewood Plywood ($37). HERE is a link. I get Lowes to cut it in half for easier 4′ x 4′ transport dimensions.
4′ x ‘4 (maybe less) of 3/16″ (5 mm) sanded plywood primed on one side ($15). I buy a full sheet and it lasts many boxes. HERE is a link.
3′ stick of 3/8″ pine dowel
Good wood glue
3/4″ 23 gauge pin nails (if using pin nailer)
1/2″ 23 gauge pin nails (if using pin nailer)
For a 2-port node:
16 3/8″ 4-40 standoffs
16 1/2″ 4-40 screws
16 4-40 nuts

Tools Needed
Table Saw
Drill press with 3/8″ bit
Scroll saw or Band Saw or Coping Saw
Handheld trim router with 1/4″ rounding overbit OR sand as desired
Palm sander OR hand sand like crazy
Handheld drill with 1/8″ bit
23 gauge pin nailer with 3/4″ and 1/2″ pin nails OR use clamps after gluing
Needle nose pliers to pull out pins
Putty knife for prying apart blocks
Hand scraper for scraping glue out of corners
Fine-tip pencil for marking
Tape measure
120 or 150 grit sandpaper

Hand tools

Cut Diagrams
4′ x 8′ sheet of 1/2″ plywood

15″ x 48″ piece of 1/2″ plywood
Note: Picture shows major cuts only

Jigs
1/2″ plywood
A. Front Edge: 13-3/4″ x 1-3/4″
B. Back Edge: 13-3/4″ x 1-3/4″
Edge scrap: Two 5″ x 3/4″ (not shown in picture)
3/16″ plywood
C. Drill Template: 5-1/4″ x 3″
D. Front Corner: 1-1/2″ x 3″
E. Front Slot: 2″ x 1-3/4″
F. Back Corner: 1-1/2″ x 2″
G. Back Slot: 1-1/2″ x 1″
H. Top Panel: 10-3/4″ x 7-3/4 with a 1-5/16″ square removed from each corner. Mark the exact center along the front and side edges of the panel.
I. Top Panel sizers: Two 2″ x 13″
J. Board panel sizer: 6″ x 7/8″
K. Circuit board holes: 5-1/4″ x 2-1/2″
L. O-scope panel holes: 5-1/4″ x 4″

Instructions for building the TARPN Mod box

Part 1: Making the wood cuts
1. Starting with a 4′ x 8′ of 1/2″ Birch plywood, cut the long dimension into 15″ sections. Each of the 6 pieces will be 48″ x 15″ and each of these should make one box.
2. From one of these pieces, make the following cuts:
a. Long-ways, make a cut at 11-3/4″ to make a piece 11-3/4″ x 15″
b. Long-ways, make a cut at 11-3/4″ to make another piece 11-3/4″ x 15″
c. Long-ways, make a cut at 5-1/4″ to make a piece 5-1/4″ x 15″
d. Long-ways, make a cut at 5-1/4″ to make another piece 5-1/4″ x 15″
e. Turn the remaining piece 90 degrees and make a 5-1/4″ cut to make a piece 5-1/4″ x 13-1/2″
3. Make the following cuts to create the designated parts common to both types of boxes:
a. Cut the 15″ length from step a above to 14-3/4″ to make the box top
b. Cut the 15″ length from step b above to 14-3/4″ to make the box bottom
c. Cut the 15″ length from step c above to 11-3/4″ to make a box side
d. Cut the 15″ length from step d above to 11-3/4″ to make a box side
e. Cut the 13-1/2″ length from step e above to 6-3/4″ to make the box center support of 6-3/4″ x 5-1/4″. Also cut a 3/4″ piece from what is left over to create the front right edge vertical support of 5-1/4″ x 3/4″
4. If working on the base box, cut the remaining parts to make the following:
a. 9″ x 8-1/2″ base sled
b. 5-1/4″ x 4″ oscilloscope panel
c. 5-1/4″ x 3/4″ o-scope panel brace
5. If working on a radio box, cut the remaining parts to make the following:
a. Two 5-1/4″ x 3″ parts to make the radio block
6. From what is left over, cut the two 4-3/4″ x 3″ floor and ceiling supports
7. From a 3/16″ sheet if plywood, cut the following parts:
a. 10-3/4″ x 7-3/4″ top panel
b. 5-1/4″ x 2-1/2″ circuit board panel
c. Four 1-1/4″ x 1-1/4″ feet

Part 2: Drawing the slots
1. Place the Front Corner Jig on the right front corner of the box top. Make sure it aligns to the front and side edges. Place the Front Slot Jig just to the left of the corner jig and make sure it is aligned to the front edge. Press down on the slot jig so it doesn’t move, remove the corner jig, and draw a line around the 3 edges of the slot jig.
2. Perform the same procedure to the right front of the box bottom.
3. Perform the same process with the back left corner of both box top and bottom using the two jigs designated for the back corner and slot.

Part 3: Cut the slots
1. Cut the front and back slots from top and bottom. I use a scroll saw, but a band saw or hand-held coping saw would work too.

Part 4 (Base Box Only): Marking and drilling the 3/8″ peg holes for the BASE BOX ONLY
1. Place the Front Edge Jig on the front edge of the box bottom
2. Place edge scrap jigs along the left edge of the box bottom.
3. Place the base sled (8-1/2″ across the box by 9″ long) in the front left corner against the jigs.
4. Make sure the jigs align with the box bottom front and side and the base sled is in the resulting corner.
5. Using 3/4″ pins, pin the sled in place with two pins, one in either corner.
New Pic->
6. Place the 2″ Front Slot Jig on top of the base sled in the front left corner inside the 2 other jigs.
7. Place the Drill Template Jig next to the Front Slot Jig.
8. Draw circles in the holes of the Drill Template Jig.
9. Take the box bottom and sled to the drill press and drill four 3/8″ holes where the circles are.
10. Using a putty knife, pry off the sled.
11. Using needle nose pliers, pull out the two pins.

Part 4 (Radio Box Only): Marking and drilling the 3/8″ peg holes for the RADIO BOX ONLY
1. Place the Front Edge Jig on the front edge of the box bottom
2. Place edge scrap jigs along the left edge of the box bottom.
3. Place the 2″ Front Slot Jig on top of the box bottom in the front left corner inside the 2 other jigs.
4. Place one radio block piece (5-1/4″ x 3″) next to the Front Slot jig
5. Make sure the edge jigs align with the box bottom front and side and the radio box is in the resulting corner.
6. Using 3/4″ pins, pin the radio block in place with two pins, one in either corner.

7. Place the Drill Template Jig on top of the radio block so it is flush on all edges.
8. Draw circles in the holes of the Drill Template Jig.
9. Take the box bottom and radio block to the drill press and drill four 3/8″ holes where the circles are.
10. Using a putty knife, pry off the radio block.
11. Using needle nose pliers, pull out the two pins.
12. Glue the 2nd radio block on top of the one with holes in it. Be careful not to put glue where the holes are. Pin in place with 3/4″ pins.

Part 5: Install the dowel pegs
1. Cut four 7/8″ pegs out of the 3/8″ dowel
2. Glue them into the bottom of the base sled or radio block
3. Clean off any excess glue with a rag
4. Allow to dry

Part 6: Main Box assembly (all pins are 23 gauge 3/4″)
Prep: Dry fit all the pieces together to make sure all fits correctly.
Prep: Make sure the Front Edge Jig is flush with the front edge of the bottom and the right side is flush with the right edge of the bottom.
1. Glue and pin the floor brace to the bottom.
2. Glue and pin the front right panel brace into the inside right side.
3. Glue and pin the center support (5-1/4″ x 6-3/4″) on the left side.
4. Glue and pin the box right side bottom edge.
5. Glue and pin the ceiling brace on both left and right.
6. Pin the box right side in from the bottom.
7. Glue and pin the box left side bottom edge.
8. Glue the top on and pin it on both top edges.
9. Press down on the center support and pin above the ceiling support.
10. Measure 5-1/2″ from the right side on both top and bottom of the box. This marks the location of the center support. Pin into the center support.
    

    

  

Part 7: Measuring for the top panel and feet
1. Measure the box top left to right and mark the center at 7-3/8″. Measure the other direction to confirm.
2. Measure the box top front to back and mark the center at 5-7/8″. Measure the other direction to confirm.
3. Perform steps 1 and 2 for the box bottom.

Part 8: Round the outer edges
1. Use the handheld router with 1/4″ rounding overbit to round all outer edges
2. Exclude the inside of the slots
3. I use bench biscuits to keep the box from sliding

Part 9: Attaching the top panel and feet (Using 1/2″ pin nails)
1. Put the Top Panel Jig on top of the top panel.
2. Trace the jig cutouts onto the top panel.
3. Cut out the top panel cutouts by cutting inside the pencil marks.
4. Place the top panel on top of the Top Panel Jig and transfer the front and side center edge marks.

5. Place the top panel on the box top and align the center marks on both panel and top.
6. Use the 2″ Top Panel Sizer Jigs to make sure the top panel is centered.
7. Pin the top panel to the top (without glue)
8. Turn the box over
9. Place the Top Panel Jig on the bottom and align with the centering marks on front and sides
10. Use the 2″ Top Panel Sizer Jigs to make sure the Top Panel Jig is centered.
11. Place each 1-1/4″ square foot about 1/16″ away from the inside cutouts of the jig. Pin in place with no glue.

12. Trim the 4 feet-sized pieces cut out in step 3 above so each is 1-1/4″ square or less.
13. Pin these 4 feet near the box bottom corners. No glue needed.

Step 10: Attach the board panel (R-Pi or TNC-Pi) (Using 1/2″ pin nails)
1. Turn the box on it’s back
2. Place the board Panel Sizer jig (7/8″ tall) on the top edge of the panel area.
3. Place the circuit board panel below the jig.
4. Pin the panel in place
5. Place the Board Panel Hole jig over the board. Drill the holes through the template into the panel.

Step 11 (Base box only) Attach the O-scope panel (Using 3/4″ pin nails)
1. Place the o-scope panel hole jig on top of the o-scope panel
2. Drill throught the template holes into the panel.
3. Align the oscilloscope panel along the front edge of the base box sled.
4. Place the o-scope panel support (5-1/4″ x 3/4″) behind the panel.
5. Glue and pin the panel support
6. Glue and pin the o-scope panel from front and bottom

Step 12: Sanding
1. Use a palm sander on all edges.
2. Hand-sand to smooth any rough or sharp edges.

Final result (prototype)