27 Jul
2015
27 Jul
'15
11:58 a.m.
Saw this auction for a pair of H960 blank front panel clips:
http://www.ebay.com/itm/391207099375
and though I'd pick them up... until they went for $30 (including shipping),at
which point I decided I'd go back to my previous plan to fabricate some out of
some scrap wood, and a pair of screws.
Time to find someone who can do injection molding... (I don't think these
could be 3D printed, the necks of the bulb-heads are under a lot of stress
when removing panels, they often snap off; will 3D printed parts be that
strong?)
Noel
27 Jul
27 Jul
12:14 p.m.
On 2015-07-27 17:58, jnc at mercury.lcs.mit.edu wrote:
Saw this auction for a pair of H960 blank front panel
clips:
http://www.ebay.com/itm/391207099375
and though I'd pick them up... until they went for $30 (including
shipping),at
which point I decided I'd go back to my previous plan to fabricate some
out of
some scrap wood, and a pair of screws.
Time to find someone who can do injection molding... (I don't think
these
could be 3D printed, the necks of the bulb-heads are under a lot of
stress
when removing panels, they often snap off; will 3D printed parts be
that
strong?)
Noel
Well, I guess you are not the only person in need for some spare ones.
I do have a few undamaged ones, but could use some additional spare
ones.
Maybe a future possibility to have a (maybe Chinese) manufacturer make
a batch of 1000, 2000 or maybe 10000 clips with a type of plastic which
is slightly more flexible so that they do not break off to quickly?
I have no idea what current prices would be for this field of
manufacturing
but would an item price of $0.50 - $1.00 be something sensible? In that
case,
I would gladly take 100 panel clips.
Ed
--
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12:24 p.m.
--------
Maybe a future possibility to have a (maybe Chinese) manufacturer make a
batch of 1000, 2000 or maybe 10000 clips with a type of plastic which is
slightly more flexible so that they do not break off to quickly?
I have no idea what current prices would be for this field of manufacturing
but would an item price of $0.50 - $1.00 be something sensible? In that
case, I would gladly take 100 panel clips.
----------
Ditto at 40
1:45 p.m.
On 7/27/15 9:14 AM, quapla wrote:
Maybe a future possibility to have a (maybe Chinese)
manufacturer make
a batch of 1000, 2000 or maybe 10000 clips with a type of plastic which
is slightly more flexible so that they do not break off to quickly?
The current design is flawed. It should be fixed. Having a ball on a shaft is stupid.
12:51 p.m.
From: Noel Chiappa: Monday, July 27, 2015 8:58 AM
Time to find someone who can do injection molding...
(I don't think these
could be 3D printed, the necks of the bulb-heads are under a lot of stress
when removing panels, they often snap off; will 3D printed parts be that
strong?)
They are actually pretty straight-forward to cast, especially if you don't
need the metal nut in the middle. I've made molds with RTV, then cast
parts out of 2 part resin. The molds do wear out, where you pull the
bulb-heads through.
I've also had them 3D printed successfully, and if you're careful about
the print direction, the bulb-heads are sufficiently strong in ABS. (I
haven't tried it in PLA. Sintered nylon would also probably work, but
would be expensive.)
From: quapla: Monday, July 27, 2015 9:14 AM
Maybe a future possibility to have a (maybe Chinese)
manufacturer make
a batch of 1000, 2000 or maybe 10000 clips with a type of plastic which
is slightly more flexible so that they do not break off to quickly?
I like that they almost always break before the panel itself does, so
don't make them too strong. I actually damaged a panel once by
replacing the bulb-head with a screw (head). (Maybe should have
used a nylon screw.)
Also, there are several flavors. You can see a few toward the bottom of:
http://www.so-much-stuff.com/pdp8/cad/3d.php
though I don't have that exact flavor with the nut in the center. That makes
ordering 10000 a challenge, since what's actually needed is probably a
mix of the various flavors.
Vince
28 Jul
28 Jul
5:22 a.m.
On 2015-07-27 18:51, Vincent Slyngstad wrote:
From: Noel Chiappa: Monday, July 27, 2015 8:58 AM
Hmm, I have 3 versions, the ones with the nut, the ones without the nut
and the one with the clamps which goes into the cabinet holes.
I guess the ones without the nut and without the rack clamps may be the
preferred ones, as there are always ways to bolt the panel clips to the
rack posts.
@Al Kossow
Yes, straight pins would be better so less break off chances.
@John Wilson
Yes, local production is always better, but to keep it affordable
for a group of private individuals, costs is usually more important.
Regarding the base material, would ABS plastic the best solution?
(Like the Lego bricks)?
I did find a place in Belgium, who has their production facility in
China. They offer up to 70% price reduction so it sounds interesting.
(http://www.kunststof-spuitgieten.be, alas only in Dutch).
@Vince
Can you make a '.stp' or '.igs' file of the bracket as shown
in the image 'bracket-screws.jpg' but with straight poles rather
than the 'ball on a stick' version?
I need one of these formats to ask them for a price offer based on the
1000 / 2000 / 10000 batch size.
Ed
--
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Zeg NEE tegen de 'slimme' meter.
Time to find someone who can do injection
molding... (I don't think
these
could be 3D printed, the necks of the bulb-heads are under a lot of
stress
when removing panels, they often snap off; will 3D printed parts be
that
strong?)
They are actually pretty straight-forward to cast, especially if you
don't need the metal nut in the middle. I've made molds with RTV,
then cast parts out of 2 part resin. The molds do wear out, where you
pull the bulb-heads through.
I've also had them 3D printed successfully, and if you're careful
about the print direction, the bulb-heads are sufficiently strong in
ABS. (I haven't tried it in PLA. Sintered nylon would also probably
work, but would be expensive.)
From: quapla: Monday, July 27, 2015 9:14 AM
Maybe a future possibility to have a (maybe
Chinese) manufacturer make
a batch of 1000, 2000 or maybe 10000 clips with a type of plastic
which
is slightly more flexible so that they do not break off to quickly?
I like that they almost always break before the panel itself does, so
don't make them too strong. I actually damaged a panel once by
replacing the bulb-head with a screw (head). (Maybe should have used
a nylon screw.)
Also, there are several flavors. You can see a few toward the bottom
of:
http://www.so-much-stuff.com/pdp8/cad/3d.php
though I don't have that exact flavor with the nut in the center.
That makes ordering 10000 a challenge, since what's actually needed is
probably a mix of the various flavors.
Vince
12:34 p.m.
From: quapla: Tuesday, July 28, 2015 2:22 AM
@Vince
Can you make a '.stp' or '.igs' file of the bracket as shown
in the image 'bracket-screws.jpg' but with straight poles rather
than the 'ball on a stick' version?
I could widen the post to 1/4", so the result would be a post
with a hemispherical top. I can't warrant that it won't be strong
enough to crack the tapered tubes in the panels, though. Those
are also aging, brittle plastic, but not nearly as easy to replace!
However, I don't have the tooling to export in either '.stp' or
'.igs', and it looks like the export plug-ins for that cost money.
Maybe someone else has tools that can do that?
Vince
27 Jul
27 Jul
12:59 p.m.
On Mon, Jul 27, 2015 at 11:58:36AM -0400, Noel Chiappa wrote:
Saw this auction for a pair of H960 blank front panel
clips:
http://www.ebay.com/itm/391207099375
and though I'd pick them up... until they went for $30 (including shipping),at
which point I decided I'd go back to my previous plan to fabricate some out of
some scrap wood, and a pair of screws.
Time to find someone who can do injection molding... (I don't think these
could be 3D printed, the necks of the bulb-heads are under a lot of stress
when removing panels, they often snap off; will 3D printed parts be that
strong?)
This is a great idea! I feel bad for never getting around to investigating
injection molding, since it seems to be one of the few surviving industries
(that and making wire) here in Western Mass., and I'd love to be able to
fix (or build from scratch?) lights-'n-switches front panels. I only got
far enough to find that there are eBay vendors who will make molds for you.
The only thing here is, it's a *terrible* design. Those damn nubs snap
off so easily (I'm sure decades of outgassing haven't helped), even when
you're expecting it and being super careful. Making more of the same seems
like just more heartbreak. So I'd be inclined to do a better design where
the posts are made of metal (or at least have a screw or stud through them
for extra strength).
Anyway I too would be willing to buy $100 or so worth, as long as that
translates to a semi-useful qty of them (yeah, more than six), to help make
up a bulk order. I suppose China's the way to go, although I'd really
prefer to support the guys who haven't been outsourced yet (and my fantasy
is that the EPA or European equiv keeps domestic companies on a short leash
so they're greener, but I'm probably kidding myself).
John Wilson
D Bit
6:13 p.m.
On Mon, 27 Jul 2015, John Wilson wrote:
On Mon, Jul 27, 2015 at 11:58:36AM -0400, Noel Chiappa
wrote:
Are the original parts made of nylon? If so, that might explain the
tendency for them to break. Nylon 6/6 is hygroscopic, and over a long
period of time, it could very well be swelling up just enough so the bulb
portions are more likely to break off.
Saw this auction for a pair of H960 blank front
panel clips:
http://www.ebay.com/itm/391207099375
and though I'd pick them up... until they went for $30 (including
shipping),at which point I decided I'd go back to my previous plan to
fabricate some out of some scrap wood, and a pair of screws.
Time to find someone who can do injection molding... (I don't think
these could be 3D printed, the necks of the bulb-heads are under a lot
of stress when removing panels, they often snap off; will 3D printed
parts be that strong?)
This is a great idea! I feel bad for never getting around to
investigating injection molding, since it seems to be one of the few
surviving industries (that and making wire) here in Western Mass., and
I'd love to be able to fix (or build from scratch?) lights-'n-switches
front panels. I only got far enough to find that there are eBay vendors
who will make molds for you.
The only thing here is, it's a *terrible* design. Those damn nubs snap
off so easily (I'm sure decades of outgassing haven't helped), even when
you're expecting it and being super careful. Making more of the same
seems like just more heartbreak. So I'd be inclined to do a better
design where the posts are made of metal (or at least have a screw or
stud through them for extra strength). 
28 Jul
28 Jul
11:29 a.m.
On 27/07/2015 23:13, Tothwolf wrote:
On Mon, 27 Jul 2015, John Wilson wrote:
> The only thing here is, it's a *terrible* design. Those damn nubs
> snap off so easily (I'm sure decades of outgassing haven't helped),
> even when you're expecting it and being super careful.
Yes, even in the late 70s i recall them being considered fragile.
Are the original parts made of nylon? If so, that
might explain the
tendency for them to break. Nylon 6/6 is hygroscopic, and over a long
period of time, it could very well be swelling up just enough so the
bulb portions are more likely to break off.
No, they're ABS - at least mine are, I just tested a few. I don't know
what grade, though, and perhaps something more flexible and forgiving -
a different grade of ABS, semi-rigid PVC, or nylon would be better.
My suggestion, however, would be to incorporate a vertical slit in the
ball and a couple of millimeters of the stem, so they're a less tight
and less critical fit. Might help, especially with a less brittle plastic.
--
Pete
Pete Turnbull
12:03 p.m.
On Tue, Jul 28, 2015 at 11:29 AM, Pete Turnbull
<pete at dunnington.plus.com> wrote:
No, they're ABS - at least mine are, I just tested a few. I don't know what
grade, though, and perhaps something more flexible and forgiving - a
different grade of ABS, semi-rigid PVC, or nylon would be better.
My suggestion, however, would be to incorporate a vertical slit in the ball
and a couple of millimeters of the stem, so they're a less tight and less
critical fit. Might help, especially with a less brittle plastic.
I tend to think the design is actually pretty good IF the posts were
more flexible and tougher. If the post flexes, it can accomodate
slight misalignment without undo stress on the panel.The friction fit
of the ball in the socket doesn't change with misalignment either. The
method also doesn't require any clearance between adjacent panels
since it comes straight off the pins.
If the posts and balls are metal, the panel sockets are going to crack
because there will not be any give in the shaft. If the ball and shaft
is replaced with a solid pin, the panel sockets will get damaged
because the socket will have to flex to conform to the pin.
I like the idea of an X cut in the ball.
1:22 p.m.
From: Charles Dickman: Tuesday, July 28, 2015 9:03 AM
If the posts and balls are metal, the panel sockets
are going to crack
because there will not be any give in the shaft. If the ball and shaft
is replaced with a solid pin, the panel sockets will get damaged
because the socket will have to flex to conform to the pin.
What he said :-).
I like the idea of an X cut in the ball.
What do folks think of the idea of thickening the shaft,
terminating it in a hemisphere, but then cutting half-way
down the result with a Y or X shaped cut? The cut would
hopefully allow the result to flex and taper into the socket,
providing plenty of grip without actually tearing anything
up.
Vince
1:58 p.m.
On 28/07/2015 18:22, Vincent Slyngstad wrote:
What do folks think of the idea of thickening the
shaft, terminating it
in a hemisphere, but then cutting half-way down the result with a Y or X
shaped cut? The cut would hopefully allow the result to flex and taper
into the socket,
providing plenty of grip without actually tearing anything up.
Just a slit would do, and be much easier to incorporate in a moulded or
machined item.
--
Pete
Pete Turnbull
29 Jul
29 Jul
2:24 a.m.
From: Pete Turnbull: Tuesday, July 28, 2015 10:58 AM
On 28/07/2015 18:22, Vincent Slyngstad wrote:
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.jpg
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.stl
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.skp
The .stl file is in inches, so remember to scale it if you are planning to 3D
print it!
For those just following along, the .jpg will be the most useful.
The SketchUp file is also provided, but unless you're a SketchUp
user like me, that's actually of little use. (Do not attempt to cut
into the spherical sections unless you've done that sort of thing
in SketchUp before -- it's very hard to get it right.)
I don't know if the design will work -- will the slit will provide enough
flexibility, will the post crack, etc.
Vince
What do folks think of the idea of thickening the
shaft, terminating it
in a hemisphere, but then cutting half-way down the result with a Y or X
shaped cut? The cut would hopefully allow the result to flex and taper
into the socket,
providing plenty of grip without actually tearing anything up.
Just a slit would do, and be much easier to incorporate in a moulded or
machined item. 
5:29 a.m.
On 2015-07-29 08:24, Vincent Slyngstad wrote:
From: Pete Turnbull: Tuesday, July 28, 2015 10:58 AM
The new design looks OK to me.
As soon as I have an '.stp' type of file I could forward it to
the Belgian company for an estimate.
Ed
--
Dit is een HTML vrije email / This is an HTML free email.
Zeg NEE tegen de 'slimme' meter.
On 28/07/2015 18:22, Vincent Slyngstad wrote:
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.jpg
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.stl
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.skp
The .stl file is in inches, so remember to scale it if you are
planning to 3D print it!
For those just following along, the .jpg will be the most useful.
The SketchUp file is also provided, but unless you're a SketchUp user
like me, that's actually of little use. (Do not attempt to cut into
the spherical sections unless you've done that sort of thing in
SketchUp before -- it's very hard to get it right.)
I don't know if the design will work -- will the slit will provide
enough flexibility, will the post crack, etc.
Vince What do folks think of the idea of thickening the
shaft, terminating
it
in a hemisphere, but then cutting half-way down the result with a Y
or X
shaped cut? The cut would hopefully allow the result to flex and
taper
into the socket,
providing plenty of grip without actually tearing anything up.
Just a slit would do, and be much easier to incorporate in a moulded
or machined item. 
5:41 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of quapla
Sent: 29 July 2015 10:29
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: H960 blank panel clips
On 2015-07-29 08:24, Vincent Slyngstad wrote:
Once you have a 3D file there are many places that can print these in ABS
which should be strong enough. Search here:-
https://www.3dhubs.com/
Dave
G4UGM
From: Pete Turnbull: Tuesday, July 28, 2015 10:58
AM
new.jpg
On 28/07/2015 18:22, Vincent Slyngstad wrote:
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket- What do folks think of the idea of thickening the
shaft, terminating
it in a hemisphere, but then cutting half-way down the result with a
Y or X shaped cut? The cut would hopefully allow the result to flex
and taper into the socket, providing plenty of grip without actually
tearing anything up.
Just a slit would do, and be much easier to incorporate in a moulded
or machined item.
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.stl
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-
new.skp
The .stl file is in inches, so remember to scale it if you are
planning to 3D print it!
For those just following along, the .jpg will be the most useful.
The SketchUp file is also provided, but unless you're a SketchUp user
like me, that's actually of little use. (Do not attempt to cut into
the spherical sections unless you've done that sort of thing in
SketchUp before -- it's very hard to get it right.)
I don't know if the design will work -- will the slit will provide
enough flexibility, will the post crack, etc.
Vince
The new design looks OK to me.
As soon as I have an '.stp' type of file I could forward it to the Belgian
company for an estimate.
Ed
--
Dit is een HTML vrije email / This is an HTML free email.
Zeg NEE tegen de 'slimme' meter.
5:57 a.m.
On 29/07/2015 07:24, Vincent Slyngstad wrote:
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.jpg
I don't know if the design will work -- will the
slit will provide
enough flexibility, will the post crack, etc.
That looks pretty good to me, and the only refinements I'd suggest are
these:
Firstly, to add a small fillet to the junction of post and flat surface,
so that there's a small radius, perhaps 0.5mm - 1.0mm, at the
transition. The sharp transition will concentrate any stress, and a
radius will reduce that. I'm not sure how much difference it makes for
a 3D-printed object but it would be significant for injection moulding.
The lack of any radii is actually part of the problem with the
original, and the breaks always occur right either at the sharp
transition between post and flat surface, or more often between post and
ball.
Secondly, and maybe less importantly, to make the lower part (maybe half
the length) of the post a slightly smaller diameter - but not to the
extent of reproducing the ball-on-a-thin-post of the original. This
eases alignment, because as Al pointed out, the panel always tilts or
twists as it's removed and that puts a bending strain on the joint - in
this case, now at the post base than than just below the ball.
Maybe that post should be a short spring ;-)
--
Pete
Pete Turnbull
9:11 a.m.
From: Pete Turnbull: Wednesday, July 29, 2015 2:57 AM
On 29/07/2015 07:24, Vincent Slyngstad wrote:
Are you referring to the junction of the post and the block? That would
be easy enough to do (though tedious in SketchUp).
Or are you referring to the bottom edges of the slots? (That one is
easy.)
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.jpg
That looks pretty good to me, and the only refinements I'd suggest are
these:
Firstly, to add a small fillet to the junction of post and flat surface,
so that there's a small radius, perhaps 0.5mm - 1.0mm, at the
transition. The sharp transition will concentrate any stress, and a
radius will reduce that. I'm not sure how much difference it makes for
a 3D-printed object but it would be significant for injection moulding. Secondly, and maybe less importantly, to make the
lower part (maybe half
the length) of the post a slightly smaller diameter - but not to the
extent of reproducing the ball-on-a-thin-post of the original. This
eases alignment, because as Al pointed out, the panel always tilts or
twists as it's removed and that puts a bending strain on the joint - in
this case, now at the post base than than just below the ball.
It troubles me that the whole design is based on the flexibility of the
particular plastic it is made out of, but I'm not sure what to do about
it.
One concern that I had was that the new design might end up trying
to ovalize the (brittle) socket in the mating panel, since the new posts
are only really compressible in one axis.
It would be next week at least before I could print and try any of these,
and then not in ABS. If someone wants to print a couple and see how
they do, that seems to me a logical next step. (Certainly before I'd even
consider ordering 10,000 of the things.)
The posts can not be vertical in the print (for strength in the correct
direction), so a small amount of support will likely need to be printed too.
(And don't forget to convert the inches!)
Vince
10:05 a.m.
On 29/07/2015 14:11, Vincent Slyngstad wrote:
From: Pete Turnbull: Wednesday, July 29, 2015 2:57 AM
> Firstly, to add a small fillet to the junction of post and flat
Are you referring to the junction of the post and the
block? That would
be easy enough to do (though tedious in SketchUp).
Yes, that's where I meant.
Or are you referring to the bottom edges of the slots?
No, that shouldn't matter since it's in slight compression.
One concern that I had was that the new design might
end up trying to
ovalize the (brittle) socket in the mating panel, since the new posts
are only really compressible in one axis.
I doubt that matters much either, because it's the posts that break, not
the sockets.
--
Pete
Pete Turnbull
12:55 p.m.
From: Pete Turnbull: Wednesday, July 29, 2015 7:05 AM
Oh, I've had the sockets split before, too.
Vince
One concern
that I had was that the new design might end up trying to
ovalize the (brittle) socket in the mating panel, since the new posts
are only really compressible in one axis.
I doubt that matters much either, because it's the posts that break, not
the sockets. 
10:16 a.m.
On Wed, 29 Jul 2015, Vincent Slyngstad wrote:
From: Pete Turnbull: Wednesday, July 29, 2015 2:57 AM
...which is why SketchUp shouldn't be used for CAD work. If you're using
Windows, I strongly suggest you get DesignSpark Mechanical - it's free to
use and has a work flow very similar to SketchUp. If you're not using
Windows, give the current release of FreeCAD a shot.
When it comes to CAD work, SketchUp is THE worst choice possible.
You should also do your design work in metric if you expect to be having
parts printed. Scaling isn't a practical solution because it can
introduce problems depending on the slicer used.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
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A Multi-Value database for the masses, not the classes.
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On 29/07/2015 07:24, Vincent Slyngstad wrote:
Are you referring to the junction of the post and the block? That would be
easy enough to do (though tedious in SketchUp).
I've placed a new design at:
http://svn.so-much-stuff.com/svn/trunk/3D/rack-bracket/bracket-new.jpg
That looks pretty good to me, and the only refinements I'd suggest are
these:
Firstly, to add a small fillet to the junction of post and flat surface, so
that there's a small radius, perhaps 0.5mm - 1.0mm, at the transition. The
sharp transition will concentrate any stress, and a radius will reduce
that. I'm not sure how much difference it makes for a 3D-printed object
but it would be significant for injection moulding.
1:04 p.m.
From: geneb: Wednesday, July 29, 2015 7:16 AM
On Wed, 29 Jul 2015, Vincent Slyngstad wrote:
I have a crufty old version of DesignSpark PCB. I'll have a look at
Mechanical.
Are you referring to the junction of the post and
the block? That would be
easy enough to do (though tedious in SketchUp).
...which is why SketchUp shouldn't be used for CAD work. If you're using
Windows, I strongly suggest you get DesignSpark Mechanical - it's free to
use and has a work flow very similar to SketchUp. If you're not using
Windows, give the current release of FreeCAD a shot. When it comes to CAD work, SketchUp is THE worst
choice possible.
I have a friend who does this sort of thing with BobCad, and I find
that for the simple stuff, I finish faster in SketchUp. The problem
is that Sketchup simply doesn't have "advanced features".
You should also do your design work in metric if you
expect to be having
parts printed. Scaling isn't a practical solution because it can
introduce problems depending on the slicer used.
I can export in metric, but the DEC designs generally don't make much
sense unless you're doing them in power of 2 fractions of inches.
Everything is 1/8", 1/4", etc.
Vince
1:20 p.m.
I have a crufty old version of DesignSpark PCB.
I'll have a look at
Mechanical.
It's basically SpaceClaim that's been tweaked to only output it's
native
file format and STL files.
You should
also do your design work in metric if you expect to be having
parts printed. Scaling isn't a practical solution because it can introduce
problems depending on the slicer used.
I can export in metric, but the DEC designs generally don't make much sense
unless you're doing them in power of 2 fractions of inches.
Everything is 1/8", 1/4", etc.
28 Jul
28 Jul
2:55 p.m.
On 7/28/15 10:22 AM, Vincent Slyngstad wrote:
What do folks think of the idea of thickening the
shaft, terminating it in a hemisphere, but then cutting half-way down the result with a Y
or X shaped cut? The cut would hopefully allow the result
to flex and taper into the socket,
providing plenty of grip without actually tearing anything up.
Yes, the problem is there is no give in the plastic, along with the material itself being
too inflexible even when it was new so the shaft should have been split.
Whoever came up with it never thought about taking a panel off.
There is no practical way to do that without bending the shafts.
3:04 p.m.
Does anyone have a photo or mechanical drawing of one of these things?
You've got me curious now.
--Chuck
12:52 p.m.
On Tue, 28 Jul 2015, Pete Turnbull wrote:
On 27/07/2015 23:13, Tothwolf wrote:
If they are made of ABS and the ball isn't critical, why not mill or drill
out a small bit of the broken stem and solvent weld in some round ABS
stock to make a new stem? Methylene chloride (dichloromethane) works
extremely well for ABS (methyl ethyl ketone in my experience does not work
very well with ABS). I've been using Plast-I-Weld (Flex-I-File) but in the
past I've also used Tenax 7R and Proweld (Ambroid), however Tenax 7R and
Proweld have both since been discontinued.
Another option worth considering is polyacetal / polyoxymethylene
(Delrin). It is tough, stable and inexpensive (but not as inexpensive as
ABS). PVC cold flows under pressure and Nylon absorbs moisture and expands
over time, so neither of those are all that great for this sort of
application.
On Mon, 27 Jul 2015, John Wilson wrote:
> The only thing here is, it's a *terrible* design. Those damn nubs
> snap off so easily (I'm sure decades of outgassing haven't helped),
> even when you're expecting it and being super careful.
Yes, even in the late 70s i recall them being considered fragile.
Are the original parts made of nylon? If so, that
might explain the
tendency for them to break. Nylon 6/6 is hygroscopic, and over a long
period of time, it could very well be swelling up just enough so the
bulb portions are more likely to break off.
No, they're ABS - at least mine are, I just tested a few. I don't know
what grade, though, and perhaps something more flexible and forgiving -
a different grade of ABS, semi-rigid PVC, or nylon would be better.
My suggestion, however, would be to incorporate a vertical slit in the
ball and a couple of millimeters of the stem, so they're a less tight
and less critical fit. Might help, especially with a less brittle
plastic.
1:22 p.m.
On 28/07/2015 17:52, Tothwolf wrote:
If they are made of ABS and the ball isn't
critical, why not mill or
drill out a small bit of the broken stem and solvent weld in some round
ABS stock to make a new stem? Methylene chloride (dichloromethane) works
extremely well for ABS (methyl ethyl ketone in my experience does not
work very well with ABS).
I think the ball size is fairly critical but the exact length of the
shaft is less so. The problem is that the ball normally breaks off just
where it joins the stem, and ends up stuck in the panel, so it has to be
extracted first (I use a small drill followed by an easy-out).
MEK is very commonly used for ABS here (industrially) and works fine for
me. It's even pretty good at welding (gluing, in this case, really) ABS
and PVC together (you need THF for PVC alone). And getting thin round
ABS isn't always easy, though some model shops do carry it. I'd insert
a bit of aluminium rod, myself, which makes it less likely to happen again.
--
Pete
Pete Turnbull
3357
days inactive
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26 comments
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participants (12)
-
aek＠bitsavers.org -
cclist＠sydex.com -
chd＠chdickman.com -
dave.g4ugm＠gmail.com -
geneb＠deltasoft.com -
jnc＠mercury.lcs.mit.edu -
jwest＠classiccmp.org -
pete＠dunnington.plus.com -
quapla＠xs4all.nl -
tothwolf＠concentric.net -
v.slyngstad＠frontier.com -
wilson＠dbit.com