Sunday, 21 August 2011

Miniature playable drumkit from scratch

Having already got an existing drumkit (bought from eBay) working as a miniature playable digital drum machine, we decided to have a go at making a new kit from scratch.

Examining (ok, destroying) the original kit we bought, it simply looks to be made from a few different sized bits of plastic tubing, with clear acetate for drum skins. So far, so easy. We'll be using some thin HIPS (high-impact polystyrene) in white for our skins (there's no real point trying to stick with transparent skins, since it allows the underside of the piezo, that we use to detect drum hits, to show through).

So a trip to Wickes for some plastic pipe, and a quick cutting session on the laser cutter later....



The drum "skin" sits nicely on top of the drum "body" (plastic pipe). But the join is a bit obvious. We need a way to disguise the nasty join. Car automotive chrome strips work nicely...



... until you turn the drum around to reveal the super-glued join (regular glue isn't strong enough to stop the chrome band from un-coiling from around the drum body)


So we tried a different approach - laser cutting some circles to create a 2mm "rim" around the top and bottom of each drum body. The idea being that it creates a recess for the drum skin to sit inside (hiding the nasty join between skin and body) and we can then just place a band of shiny metallic vinyl sticker around each rim to give the illusion of a metal/chrome band

The rim acrylic is 3mm thick, which allows 1.5mm on the body, and 1.5mm to stand proud. The skin HIPS is 1mm thick, so after fitting, the rim should stand slightly proud of the skin

Note how after placing the rim acrylic on the body, a slight recess is created, to accept the (white) drum skin and hide any nasty joins.

We left the backing on some of the rims, just so they would be easier to identify in these photos!



The "plastic circles" approach seems to work quite well, but until we get some chrome banding on, we won't know for sure whether it's a viable option. But it's certainly quick and easy enough to do!



This is the basis for our hi-hat stand.
We've used some off-cut disks from the centre of the rim circles to prove the concept, but for the final design, we're hoping to use something that looks a little more like a real pair of hi-hat cymbals.

As before, the backing has been left on the black acrylic, just to make it easier to see the component parts

The stand is made from two "planes" which create a 3D shape using the traditional "slotted cross" arrangement.



The two "cymbals" need to be separated by some rubber, or perhaps some anti-static packing foam or similar, allowing them to be struck together, just like a real hi-hat would. In the photo below, you can see that there is a gap between the top disk (representing the top cymbal in this example) and the top of the plastic arms used to hold it in place. This gap would be taken up with the introduction of some little rubber stand-offs between the two "cymbals".



This is the layout for the drum rims from a sheet of acrylic.
We tried to reduce the total amount of waste. Cutting out circles with hollow centres is always going to create waste, so where possible we tried to fit one rim inside another. The grey areas below show the parts of the acrylic that will probably end up being wasted - so it's not quite as bad as it could have been!