My G90 Gets a PROTOTYPE Battery Box!

 Executive Summary

1) I built a battery box that mounts on the G90 almost like a real manpack

2) The box is built from Kydex and aluminum angle stock.

3) The Kydex plates and the angle stock are riveted together using a cheap Harbor Freight riveting kit.

4) The box mounts to the radio using the rear handle mounting holes.

4) It works great - and looks sorta OK:)

A perspective view of the radio and battery box in operation.

A close-up of the box.

The bottom view.

And finally, a side view.

A Work In Progress

Most of my projects look a bit half fast (sp and sic), as I typically just want something that works. This works. But it could look better, and I'm sure there many clever improvements that can be made. 

I've teed this project up as a thought experiment more than anything because the G90 really needs a battery box. Once modified for generally coverage, the G90 is about the closest thing to a military HF manpack that's affordably out there. So please send along your suggestions, or better builds, so I can learn from them and share them.

Maybe we can goad/inspire someone commercial into building a small, light battery box.

In the meantime, here goes nuttin'.

The Problem

After building a manpack for the G90 and using it for a while (see earlier blog entry), I decided I wanted something lighter and less complex.

What I wanted from the beginning was an easily removeable battery case that would carry a battery, a few dongles for the accessory jacks, and that would protect the back of the radio - in other words I wanted it to work like a real manpack.

I also wanted something that could be built quickly with simple tools and little or no metal work.

And the box had to mount easily to the G90 to make conversion from portable to base operation quick and easy.

Why Kydex?

Like Clint Eastwood said, "a man's got to know his limitations."  Too many homebrew projects have made me aware of mine.

I don't have the tools, time or temperament to try to build an all-metal battery box.

I considered trying to mold one, but but after trying a few experiments decided that would not yield a quick, simple box others might be able to make.

Perhaps something like Kydex sheet might work. It's a good insulator, it's rugged, and you don't need to paint it.

Most important to me was the ease of use of Kydex. Simple scoring and breaking will quickly produce Kydex panels

Kydex also is heat formable.  I wasn't sure when I started how that might help, because the box hadn't taken shape, but indeed, though not necessary, this characteristic turned out to be helpful.  

I originally thought I might be able to heat form the battery case shell.  This showed some promise but was taking too long because I don't have adequate heat-forming ovens and vacuum fixtures as is typically used to do this.  And I wanted to keep things simple. So I'd need a way to connect rectangular Kydex panels.

Why Aluminum Angle Stock?

Well, because it's readily available at most larger hardware stores.

If I could find a way to attach the Kydex panels in an aluminum angle stock frame, I could quickly assemble a custom-sized battery box, and the aluminum frame would provide rigidity and a sturdy attachment point for the box.

While you do need to cut the angle stock, it's easily done by hand with a hacksaw, and much more easily done on a chop saw with a fine tooth blade.

So far so good.  But how to connect the frame to the panels?

Harbor Freight to the Rescue!

I experimented a bit with glue, and with screws, but was unsure how the glued assembly would hold up, and lots of screws on a portable radio case seemed like a recipe for disaster, or at least lost screws and nuts. This seemed like a bad idea for a battery box.

And then Harbor Freight yielded the answer. I had an old HF riviting kit I'd bought on sale years ago.  I experimented with how the Kydex would rivet to the aluminum channels and found it to be quick and very solid.  It's off to the races.

Making the Panels

You've got to design the box before you can make the panels.

After measuring my battery, and the G90 case, I decided that the top and bottom panels for the box should be about 5 inch squares, and the side panels for the box should be about 1.9-2 inches tall, depending on how much clearance you want. The idea is to form a structure that could overlap the back of the G90 at the rear handle mounting holes.  This way, longer M3 thumbscrews could be used in those holes to quickly attach the box to the radio.

My process follows (yours will probably be better, if so please let me know).

First, mark the Kydex to make the panels.

Use painters' tape to scribe the scoring lines on the Kydex, then score the Kydex using a heavy metal straight edge and razor blade.

YouTube told me that when scoring it's better to make multiple cuts at a relatively inclined angle.  I scored four times at about a 45 degree angle with a box cutter.

After scoring the Kydex you need to break the Kydex along the score line.  

Position the scored edge directly over a straight edge of a counter or table. 

Place the metal straight edge on top of the Kydex at the scoring line.  

Firmly press down on the Kydex where it extends over the table. It may resist a bit at first but will snap. See below :)

In this pic you can see that a 12-inch-wide panel conveniently yields the two five-inch square panels and a side panel. Take the snapped-off piece, score along the two vertical lines, break twice, and you have the top, the bottom and a side.

Rinse and repeat as they say, and you have three side panels and two top panels.

At this point, it's a good idea to fit the panels to the radio, with or without some tape, to see if things have turned out like they were intended.

If all looks good, it's time for some light metal bashing.

Cutting the Metal

I hoped to avoid metal work, but this part is really easy.

You'll need some hardware store aluminum angle stock.  I used one inch stock, 1/16 inch thick, as shown below. 

As you've guessed by now you'll need four five-inch-long pieces to connect the sides, and two three-inch pieces for the back (side) plate.

Tolerances are always a problem. I found the easiest thing to do, because I had a chop saw with a fine-toothed metal blade, was to cut all the pieces a bit long, then stack and tape them with one end aligned, then trim the stack at the other end to ensure all four pieces were the same length. Like this:

After the pieces are cut, round the corners and slightly bevel the cut edges with a file as seen below.  

This picture shows a five-inch bracket filed and marked for drilling on both sides - 1 and 1/2 inches from each end and 1/2 inch out from the inside corner.

Your finished brackets will look like this.

Building the Box

This should be the easy part, but it's all about precise alignment and careful riveting.

I won't try to lecture you on riveting.  It's a great tool for this job, it's fast, forms a great connection, but things can go wrong.

What goes wrong? Wellll, (and yes don't ask how I know) a few common problems are:

1) if the hole in your Kydex or your hole in the aluminum isn't exactly the diameter of the rivet, the parts can be riveted in a misaligned position. It's not the end of the world - you can drill out the rivet and start again - but it really slows things down.

2) or a hole can be in the wrong place. Use the metal bracket as a template for the holes in the plastic, and don't let the pieces slip apart while you are drilling.  A drill press and some clamps are really useful here.

3) your rivet can slip (in or out) while you are installing it.  The riveting process involves the rivet tool pulling a center pin up from the bottom of the rivet to expand the surface behind the panel, but it requires four or five squeezes of the rivet tool. Sometimes the rivet can slip after the first squeeze or two before things are tight. Finishing the rivet after a slip means you'll be drilling it out; or

4) you might use the wrong size rivet. The diameter usually isn't critical, but each size of rivet will pull materials together over a certain range of thickness when compressed.  You need to be sure that the thickness range of the rivet is appropriate for the thickness of your Kydex plus the thickness of your aluminum.  

For the record, I used 1/4 by 3/16 rivets which work fine for 0.08 inch thick Kydex and 1/16th inch thick aluminum.  Use what you have but remember to buy an extra bag of whatever size you decide on, because Murphy's law dictates that the kit supplied with the Harbor Freight riveter is always short by three or four rivets.

Save yourself some grief if you are unfamiliar with rivets. Watch a few YouTube videos and practice on some scrap material.  It's worth the time. I've built several projects now using rivets, like a cage (that I rarely use any more, but it's very cool......) for my IC-705.  And all manner of interesting antenna projects can be handled easily with rivets.

The following pics will show you what my finished prototype looks like post-riveting.  I'm not proud of a few of the gaps or the alignment in a place or two, but these are the learnings from Rev. 0 projects. Rev. 1 will look better, but this is working well enough for the summer portable season for me, unless I learn a few things out in the field. As I said, rivets can be drilled out......

This is the outside corner of the box.

This is a view of the inside of the box.  On the next revision I will make sure to locate that first row of rivets so that the G90 is supported by the four nubs in the box as well as secured with the four knurled knobs.

OMG, Where Is the Lid?

OK, I forgot to mention the lid. Probably because I'm not that excited about it.  You can see the top panel installed in the next pic below.

Take a careful look and you will see that I did not rivet the top on to the box but instead used a pair of knurled screws.

These are 8-32 knurled knobs I had laying around. I did this so that it's easy to get inside the box when it is attached to the radio.  Just remove one knob and swing the top around and you can get inside.  This is important if you want to get to the battery charging connector, or change whatever is plugged into the back of the radio.

You'll also notice what looks like a pair of humps sticking up from the lid.  These are dongle ports.

Remember when I said it's helpful that Kydex is heat formable?  Those two little heat-formed ridges are pass-throughs for your antenna cable, your key dongle, and whatever else needs to escape the box when the lid is attached.  

The ports are a bit ugly.  I formed them by heating the Kydex with a heat gun and bending the soft plastic to the desired shape with long nose pilers.  There are better ways. I haven't found them yet.

Of course, you can just remove the lid if that is consistent with your operating style, but it's not the way I roll. Typically my radio will be inside a radio bag when I'm in the field, so it's helpful to have these ports for the escaping wires.

I added a top pic below so you can see more clearly what's going on.  The upper and lower dongle ports work well enough, and in this pic the keyer and antenna dongles are exiting the lower dongle port.

But you can see that cutting the top, and then primitively heat-forming the ports, distorts the shape of the sides of the lid.  Work on this continues. I like the way the ports work, with flexibility for almost anything you want to run out of the box. You can bet I'll be watching some videos on YouTube for a hack about thermoforming Kydex without "the right stuff."🙈

Mounting the Box to the G90

The last little tricky bit is mounting the box to the G90.

Happily, pretty blue M3 knurled knobs are available in many lengths.  Like the rivets, you need to do a little math. Measure the screw length that normally holds the rear handle, add the thickness of the aluminum and Kydex, and order the closest screws to that size that are available.

To make the mounting holes in the battery case, decide where you want the holes to be, and carefully tape the rear handles over the box as a drilling template.  After drilling one side, repeat on the other side.  Use a square to draw a line across the top of the box so that your screws are aligned identically on each side.  And you are done.

You can see the box mounted with the screws in the last pic above.

Stuffing the Box

I'll leave it to your use case to decide what you want to locate and secure in the box. I've used Velcro to anchor the battery, and the dongles don't require anchoring.

This is my current configuration. The heavy black cable is the antenna dongle, and the thinner red and white cable is the keyer dongle I use for a straight key.

Final thoughts.

The box looks better with the aluminum painted black, so that's what you see in the first two pictures at the top of this post.

The box is useful without a battery. For example, A shorter box could be used without a battery to protect the back end of your radio and store all your dongles

You might get lucky and find a box the size you need, which will save you alot of work. 

About the only thing critical to the design is have two solid mounting surfaces to cover the rear handle mounting holes with solid metal like I've done here. You can then mount any box you can find over the holes. 

I went through all this BS to make it look like the box was sized for the radio, but if I could have found a suitable box of the right size you can bet I would not have gone the Kydex riveting route.

The Fine Print

As always, this explains my experience. These aren't recommendations, it is always up to you to decide what is prudent and safe for your equipment and operations. Have fun, but do it safely. Make certain connections inside the box are secure and can not short to each other or ground - the aluminum channels secured by the colored M3 mounting screws are likely at ground potential.

Send me improvements, please :)  . de Scotty ka9p/zf2sc