Thursday, 24 September 2009

Beams -mold making

Basic mold is made from 2 sheets of approx 4' x 9' sheet materials 18mm thick. The critical thing with constructing this mold is getting the pivot pin alignment holes in the right place, and perpendicular to the sides of the mold and parallel to each other. The shape and curve of the mold are defined by a template made from the Full Size Patterns (FSP)

 I bolted the 2 sheets together before drilling the holes in an attempt to prevent any misalignment. Even so, it is tricky. Plans suggest using a drill press, but in reality humping 2 heavy sheets 4 x 9' around is really not possible. In the end I brought the drill press to the sheets, and then had to try and get it all level and wobble free etc. Infact unless you have a drill press with a deep throat, you cannot actually get near the second hole.
The white tubes are where the pivot pins will go in the final beam. Have to make sure the sides themselves are dead upright and parallel to each other first. otherwise you cannot get the tubes perpendicular and exactly level across the required. I  struggled for several days before I was happy that all was OK.

The template is made from the FSP and is to check the relationship between the pivot pins and the top of the recess mold, which is important for correct beam/float alignment. Also a good check that the pivot pins are in the right place, and that the reccess mold is the correct shape. (Has sloping front and sides, and was a bit  tricky to make). Sliding the template across the mold from side to side does at least check that the pins are parallel to each other

Close up shows things look OK

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