Tonkputer by Nev@Lehmä

Author: Lassi Niemistö
Published: 25th August 2005

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Curving the perspex

Window-modding a normal computer case is easy enough - lots of straight lines. Window-modding a milk churn is an entirely different challenge - the lack of straight lines to use as a reference makes life fun. The first step was to go shopping: a sheet of 3mm perspex from my local hardware store, and a hot air gun.

Tonkputer by Nev@Lehmä Perspex Window

This bad-boy is more than your standard hair dryer: the air produced is 300 - 500C. I used some masking tape lined up with the window hole I cut as a guide, and cut the perspex to the correct size.

Tonkputer by Nev@Lehmä Perspex Window

I used the back side of the barrel as a mold and started to heat the perspex. The process is quite difficult: if you do not get an even curve, the top and bottom edges will not be parallel. I started to succeed when I heated big areas as equally as possible. After some sweat and cusswords I managed to get the perspex curved evenly. I used some belts to hold the plexi curved while it was cooling down.

Tonkputer by Nev@Lehmä Perspex Window

The final result was good enough - it had some little imperfect spots, but they are really only noticable to me because I know where to look. I test-fitted my new, curved window to the hole, and it looked great.

The window frame

A fine window needs a fine frame, so I went to the aluminium store. I bought 1mm, 2mm and 3mm aluminium plates and made a 2,5cm frame for the window from 2mm plate. I find a common circular saw the best power tool for aluminium, though the hole in the frame was made with a combination of angle grinder, iron saw, Dremel and file. The frame is not only decoration, it also attaches the perspex to the barrel.

I borrowed my friend's drilling machine and drilled over 100 holes in the frame. It wasn't too easy, because the drill tried to bend the frame if I pushed it too hard. I sanded the frame and polished it with AutoSol paste.

Tonkputer by Nev@Lehmä Perspex Window

I curved the frame to make it fit to the window and drilled mounting holes to the perspex. The holes had to be drilled very carefully to avoid chipping the perspex. I used 54 M3 bolts to mount the perspex to the frame. I was a little afraid that the bolt ends inside the barrel would look ugly but luckily they weren't a problem as you can see in the second picture. My eyes settled on the finished window.