PSN-L Email List Message
Subject: Testing setup.
From: "Fikke, Audun" Audun.Fikke@.........
Date: Sat, 29 Sep 2007 04:37:00 +0200
I'm daring my first post here...
I'm building a Lehman with pipe-frame pretty much like the drawings
found on Larrys web.
I've replaced the lower pivot point knife edge solution with a PDC-
industrial diamond cutter + steel ball bearing. The cutter was supplied
by an oilfield bit salesman for free:) I couldn't come up with an idea
for a smoother surface to fight friction. This is the support for a
steel ball on the end of the boom.
I've hooked it all up on a prototype wooden base (for now) to get the
feeling for what it's gonna look like. I might end up permanently
bolting the frame to the concrete floor in my shed.
To adjust top pivot points distance from top beam, I'm using a
'fine-tuner' from a contrabas. It's got about 5mm of travel, and seems
to do the trick. I got inspired by reading about steel guitar parts
mounted on other sensors:) =20
Now I'm beginning to look at the frequency of the boom and I'm a little
puzzled how to proceed with the tuning.=20
Should I strive to keep the boom horizontal at all times as I try to
move upper pivot point closer to vertical with the lower?
Are there rules of thumb to where the string and weight attaches too the
boom? I've got 36inches to play with here.=20
Where should the balance point of the boom be located? At the string
attachment point? Or if not -to what side?
And at last I'd like to point out that in the construction notes, it's
not stated that you should use non mag materials. I started to wonder
about this and quickly found posts about this in the mailing list. So
off I went again to the HW store to trade in my boom and shims.
Very well-- I'm leaving it running for the night, and hopefully I can
proceed tomorrow with more knowledge from this group.
Greetings from Norway
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