Thank you very much for that info, I was thinking about using delrin but now I
might turn my own bearings on my lathe. I am aware of Lignum Vitae very hard
stuff, and it wont even float in water goes right to the bottom like a rock....
If I can remember it has natural lubricating properties and that's why it was
used in pulleys and such on the old ships. I made a smallpipe chanter from a
piece a few years ago, it has a nice green color... Cheers, Seth
Arle Lommel <[EMAIL PROTECTED]> wrote: Hi Seth,
I'm not sure why drilling out that hole would impact a wah-wah sound.
However, I don't think you need to worry about the structural integrity of the
shaft system from that hole. If you need that wood brace (which is subject to
seasonal movement) to support a *metal* shaft that is much more rigid than
anything else in the instrument, you are in trouble. It is instead drilled out
to allow the shaft to pass through it, not to support the shaft. In fact you
want to minimize contact between the shaft and anything else to reduce
friction. Therefore your ideal system would contact the body only at the head
and tail bearings.
Maybe someone else can think of a reason for the wah-wah, but my only guess
would be that the shaft wasn't *perfectly* straight and that the loading
pressure of those drones was causing an intermittent rub between the shaft and
the brace that was manifest as sound like that. But that's only a guess.
Regarding the bearings, it looks like he's used a wooden bearing for the head
(the wooden rod) and probably for the tail as well, but it's not visible. Marc
Reymen has posted details on the list in the past of how to make these (they
are fairly simple to make), but suffice it to say that a well-constructed wood
bearing from lignum vitae will probably last longer than the rest of your gurdy
and require less maintenance. Marc makes them from lignum vitae, which was used
to make industrial bearings for steamships, mills, etc. It works more like a
metal than a wood, and is almost indestructible. You might be ale to get
similar results from some other woods like cocobolo (it's often used to make
self-lubricating guides for bandsaws) or even osage orange/hedge apple, but I
haven't tried these. The really nice thing about a wood bearing is that if you
do get any grit into the wood bearing the grit gets incorporated into the
bearing rather than scouring the bearing and/or shaft,
as can happen with metal or plastic bearings.
Best,
Arle
On Mar 15, 2007, at 2:14 PM, Seth Hamon wrote:
I was looking at the building of the luteback hurdy gurdy on
http://www.edmonds.de/body6.html . What is the reasoning behind drilling the
hole in the first rib for the shaft 4mm larger than the o.d. of the shaft? I
know he said it relieved the wah wah sound problem he was having.. It just
seems as though this would take away some of the structural integrity of the
shaft system.. Is this a common practice for the construction of a hurdy gurdy.
It does appear that he didn't use any kind of bearings for the shaft. It seems
to be set directly into the wood. Cheers, Seth
