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In Reply to: wow posted by Charlie G on May 22, 2002 at 13:05:23:
>Did you use a press to glue the layers of MDF together?I cut square pieces MDF with a size of approx. 175mm. I drilled a 20mm hole in the middle of each and stacked them on a tube of same diameter. Clamped with eight screw clamps I glued them together with white (?yellow) glue. I pre-cut a cylinder of 165mm dia. out of the block since this is the max. diameter my lathe can handle. I used a piece of tube welded to a piece of sheet metal (5mm thick) as a flange where I simply screwed the MDF cylinder with 4 wood screws (take a close look to the pics on my HP). So I'm able to clamp this into the lining of my lathe.
The flare guide was made from 2mm sheet metal (printed the tractrix flare on paper and transfered/cut them on/out of the sheet metal).
With this guide it's nearely inpossible to turn a 'wrong' flare since it will keep you from cutting too 'deep' into the MDF.
In regards to the roughness of your horns: May be solid wood will behave different (i.e. giving more rough surface) - I don't know - could imagine it depends on the direction of the wood's grain.
I also don't know wether or not MDF has got some drawbacks compared to solid wood like maple or brich. Any thaughts on this?>If you do another one, could you take some pics of like... the
>initial mockup of the MDF and how you started the cut and so forth?For now I'vot two of them finised, with one having the driver attached. So it may take a while. There is a chance that a friend of mine will buy a big lathe being able to turn 350Hz horns. In this case I'll report on my attemps to turn larger horns from MDF.
Thanks for the interest.
Erik
(Volvotreter)
Follow Ups:
Thanks for the info. If I can find someone with a lathe that'll do it, I might give some a shot.I know Bruce uses a hardwood for his horns, but why he does exactly, I don't know. Did you put a finish or anything on the MDF?
As for my horns, they were just cut poorly. The throat is out of round. How one accomplishes that on a lathe... I'm not exactly sure. Victor said that the place that finishes & sands it was responsible for that. But that doesn't account for the difference at the mouth, and the funny 'bump' in the middle of the horn (again, unless it was not meant to be a true tractrix horn). Based on your tractrix calculator, for a 1" driver, and 500hz horn, the mouth should be 21.6cm across... well, on mine, one is 30.3cm and the other is about 31cm across. So whatever it is, it's not a tractrix.Charlie
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