[sdiy] Why I was asking about UNEF etc.

[Theo]

One problem with the thread in the font panel is that the rotation stop (a
little pin on the 3310 pot housing) has to be removed and therefore can't to
its job.
So this is the first difference, but it gets worse ;)

When the pot is used with a nut, the rotation stop is primarily there for
assembly purpose.
While tightening the nut something has to absorb the rotational force
applied.
You don't like the PCB pins to do this job, this is where the rotation stop
comes in.

When the nut is tightened the front is clamped between the nut and the pot
housing.
This clamping action gives enough friction between the front panel and
pothousing so that rotational force from turning the knobs is diverted to
the front panel.
Don't under estimate the clamping force, its just like a vice.
When you clamp a object in a vice you need a lot of force to remove it
(without opening the vice).
But you only need little force to open the vice itself.

When you have the thread in the front panel you don't have the clamping
force between pothousing and front panel to absorb rotation forces.
This is the big difference between the two methods.

On the bright side the rotational forces involved are quite small.
If you put a rotation stopping "star" washer between the pothousing and the
front panel you're probably ok.
The "star" washer eats itself in both the front panel and the pot housing
resulting in a form-closed assembly.

BTW.
I tried 3310 pots for some modules.
Think the 3.15mm plastic shaft is just too thin.
The pots feel wobbly if you put a knob on them, not a good feel IMO.

Actually I disliked the 3310 that much that I decided to widen the holes in
all the 20 Schaeffer front panels I  already had made to fit a different
model pot.
I now use 174 series from Vishay for my modular.
(Anyone wants to buy a pile of 3310Y 10K and 100K?)

If its is for cheap small pots I would just consider the 11mm and 14mm
snap-in pots of the RK11 and RK14 series.
These are cheaper and don't wobble like the 3310 do.

Cheers,
Theo


----- Original Message -----
From: Tim Parkhurst <tparkhurst at siliconbandwidth.com>
To: <jhaible at debitel.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, May 16, 2003 6:48 PM
Subject: RE: [sdiy] Why I was asking about UNEF etc.


> Since the pot's threads are plastic, I'd say they would be the first
things
> to strip. In this case, I'd say you're safe. AS LONG AS you don't strip
the
> threads in the panel when you're tapping it! Once you've got a good thread
> in the panel, I think it will be okay. Still, you're only going to get 3
or
> 4 threads, and that would make me a little nervous. If you really want to
go
> this route, then be very careful when tapping the holes in the panel, and
> apply a drop of Loctite to the threads once you have the pot in place.
This
> will help keep it from loosening. I think using the counter nut scheme
would
> just place more stress on the plastic threads. These are the weakest part
of
> this setup, so I'd probably avoid that.
>
> I'd still see if you could fit a panel nut on there. Maybe you could drill
> or mill out some additional room on the bottom face of the knob so that
the
> panel nut will fit up in there better? Just a thought.
>
> BTW, I like those 3310 pots too. Nice and small, reasonably priced, decent
> feel. I'm thinking of using those to retrofit all the sliders in my
Odyssey
> (FINALLY get rid of those impossible to find sliders).
>
> Tim Servo
>
>
> *************************************
> > -----Original Message-----
> > From: jhaible at debitel.net [mailto:jhaible at debitel.net]
> > Sent: Friday, May 16, 2003 9:29 AM
> > To: Tim Parkhurst
> > Cc: synth-diy at dropmix.xs4all.nl
> > Subject: RE: [sdiy] Why I was asking about UNEF etc.
> >
> > > Personally, I'd say you're asking for trouble by threading a pot
> > directly
> > > into an aluminum panel. In a relatively thin sheet of aluminum, you're
> > not
> > > going to get too many threads. For example, even if the panel were
1/4"
> > > thick (about 6.3mm), you are only going to get 8 threads. If the panel
> > is
> > > 1/8", you're only getting 4 threads. You won't be able to get enough
> > torque
> > > on the pot to hold it in place reliably and this means that it is
going
> > to
> > > be VERY easy for the threads to strip.
> >
> > The panel is 3mm - this is thicker than the nut that comes with the
> > pot, so I guess vertical forces cannot be a problem. The question
> > is whether _rotational_ forces can do more harm in this case than
> > with a nut. With a nut, the front panel is clamped between the
> > pot's body on one side and the nut on the other side. If I apply
> > rotational force on the body (via the shaft in end position),
> > the nut can get loose, too. With a thread in the front panel,
> > the front panel "is the nut". So there should be no difference:
> > this the first resistance to overcome for turning anything loose
> > would also be the clamping, or pressure - this time, between
> > the panel and the pot's body. Is there a difference?
> >
> > My gut feeling says there *must* be a difference, but
> > I'm too blind to see it.
> >
> > > Are you using panel nuts? They're special purpose nuts that
> > > are very thin. Again, they'll only have 4 or 5 threads, but because
> > they're
> > > made of steel they are much stronger and will hold just fine.
> >
> > Ahh, maybe this is the difference, steel vs. aluminium.
> > But then again the thread on the pot is made of plastic anyway.
> > So ist there a difference still ?
> >
> > JH.
> >
> >
> > -------------------------------------------------
> > debitel.net Webmail
>
>
>
>
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