« Go Back

Modification – Smith Backpack

I needed some sort of secure harness – to hold the Petrol Soundbag.

A good place to start looking >


Then click on the “Images” tab. Lots of designs to consider…

Versa-flex have a few models. Price range: $154.95 to $225.45


LocationSound have a good selection. Price range: $75.25 to $399.00


Happened to find this Smith Backpack on Amazon. Price: $31.34


Here’s the original design of their ‘backpack’ system >

Smith Performance Sprayers - Backpack.

Its intended use – is to attach a plastic tank (to hold ~4 gallons) on the backside, with the 4 sewn-in straps. You then fill the tank with chemicals (to perhaps kill weeds), put the harness on and walk around – holding a spray nozzle in one hand. It’s attached to a rubber hose – which goes to the bottom of the tank.

The other hand operates the pumping handle – which builds up pressure inside the tank. When you pull the nozzle trigger, the spray comes out…

Backpack holds a chemical tank with pump handle.

I thought this harness had great potential and the price was unbeatable…!

One just had to move the function of holding something – from the backside to the front.

Ordered it thru Amazon and got in Jan-2018…

So, it just sat there – waiting. I would occasionally put it on and try to figure out the best way to attach the soundbag. After a few tests, I concluded that the soundbag first needed to have a rigid internal frame built. See the previous Petrol Bag posting.

Finally, in early May-2019, with a vision of the new design, I purchased all the necessary hardware, from a store in Calgary >


All the original straps on this harness, were in the wrong positions – for the new design.

Used a ‘carpet-knife’ blade – to perform the delicate operation of cutting between the sewn-on strap and the vest. One starts at a corner of a strap, slowly pulling and peeling it away from the vest, as more threads are exposed and cut.

After the strap is off, a fine-tipped needle-nose pliers, is used to pull out all the remaining threads in the vest.

Carpet knife used to carefully cut thru the threading. The straps were sewn onto the vest.

Here’s a shot of all the straps – that were removed >

All the old strapping was removed from the harness/vest.

After figuring out the best place to position the waist strap, I proceeded to make holes for the rivets. This next image shows the most important tool, for this project >

A roofing nail used to hold down asphalt shingles.

A common 1.5 inch roofing nail – probably used to hold down asphalt shingles. It has the perfect working length and it needs to be tightly held and locked with vise-grips. It also has the perfect diameter for making the holes – that the rivets will fit thru.

This next step is key. The nail is placed over an open flame, until it is red-hot. With one hand firmly holding the nylon strapping in place on the vest, one quickly makes two holes – going thru all the layers at once.

You need a good aim, judgement of distance spacing and a quick delivery. It would be very easy to screw things up. A red-hot nail doesn’t care – it will do its melting job, no matter where you place it… 🙂

If you wreck the vest, you could just buy another one for $31.34… 🙂

Rivets are then inserted from the inside of the vest and then out – thru the new strapping.

With the narrow end of the rivet sticking out, one pushes a cap on, with finger pressure. Then with a heavy steel backing plate, a hammer is used to join (compress) the two pieces together.

The nail is put back into the flame, to be reheated – for making the next set of two holes. This melting action – cauterizes all the nylon, meshing and foam materials. There are no loose ends to worry about.

Just keep the door open for ventilation… 🙂

A roofing nail glowing red-hot in an open flame.

Here’s a close-up of one side, of the waist hooking assembly…

Close-up of the waist hooking system.

The D-ring attaches very quickly into the spring-hook. And it can’t come apart by ‘accident’ either. The other end of the waist strap has a clamping-buckle on it, which allows for perfect tension adjustment.

After the waist hooking system was completed, marks were made – where the other 4 straps would go – that would eventually hold the soundbag in place. Each of these straps also have a clamping-buckle for tension control.

The soundbag came with 4 D-rings sewn into the bottom corners, and 4 more are on top.

This next image – is the Beauty Shot. It shows the completed positioning of the 4 spring-hooks, that go to the bag. Each of these straps have about a 5-6 inch range of movement – depending whether one is wearing a tshirt or a heavy winter parka. The bottom waist strap also has a ‘tail’. Just pull each one – to tighten things up…

All together, I used 24 rivets for this harness and the total weight is just under 2 lbs.

The Beauty Shot. Shows the completed project.

And here is the Work Shot. Used whatever was at hand – to quickly help hold down, or push various areas of the vest/straps, into position. This combined effort helped produce the above image… 🙂

The Work Shot. All the bits and pieces used to hold the vest and straps in position.

Next to come – some action shots of the vest + soundbag + the Zoom F8 audio recorder – connected to the Rode NTG-3 shotgun mic, which is on the boom-pole…

Ordered a Triton Audio Fethead Phantom from B&H Photo. Tracking number indicates arrival on Jun-11-2019.

« Go Back

Leave a Comment

Your email address will not be published. Required fields are marked *