Sunday, 23 May 2010

Heat of battle

Incredibly as predicted the weather man got it right this weekend and it was a scorcher (for the UK 27C = 80F). As mentioned I managed to create a backpack harness for the tank. As I was rushed, I was unable to take detailed stage photos.

Here is a picture of the tank complete with backpack and newly fitted 3/8" tubing.

I had problems working out a way to create a harness. In the end I bought a cheap backpack and cut the 'bag' part away to leave just the shoulder straps and the part of the pack that rests against your back.

I then fastened this to a 16" wide piece of 10mm plywood. I did this by cutting three 2.5"x16" strips of 15mm pine. I placed the plywood on the bench, centralised the back of the backpack on the plywood then placed the three strips of wood on top, sandwiching the backpack material in between the strips and the plywood. I then drilled 4 holes through all three layers in each strip.

I then recessed each hole in the strips using a 20mm Forstner drill bit. This allows me to ensure the nuts and washers I used to bolt the three layers together did not protrude above the surface of the strips which, when in place, rest on my back.

Here is a close up of the back of the pack. The three strips can be seen in between the two black shoulder straps. Note the recessed holes for the fastening nuts and washers.

Using a router, I put a radius on the strip edges so they would not be unconfortable when wearing the harness.

To mount the tank to the plywood sheet I fastened two 1.25" planks together along their edge, then cut two 4" holes centered at the junction of the two planks. When apart, this leaves semi-circular holes for each tube to fit in.

When clamped together with bolts, this grips the tank quite firmly. Here is a top view looking down onto the top of the tank.

This 'clamp' was then bolted to the ply.

However, when loaded with water the tank is heavy, so I solvent welded two strips of PVC onto the outside of each tube. These rest on the 'clamp' above and prevent the tank from slipping through the holes. This also shows the backpack strip radius.

To fasten the tank at the bottom, I created another piece of wood with semicircular 4" holes and fastened this to the ply. The tank tubes are held against this with a 1" strip of steel as can be seen at the bottom of the left hand tube below.

I need to re-think my nozzle desgin though, as going up to a 3/8" feed pipe seems to have reduced the range. You're still gonna get very wet though.

Here are a couple of videos of me using the gun this weekend with my son and his friends (no sound as it's from CCTV).

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