wiping contact on aluminum

[malua mada!]

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

 

[Jeroen Belleman]

On 27/02/18 22:25, malua mada! wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

Sliding contacts on aluminium will always fail. Sliding *anything*
on aluminium is bound to fail. Either attach a pad of CuBe or
some other Cu alloy to one side and have your moving contact slide
on that, or perhaps attach a piece of thin piano wire between the
moving parts in such a way that it never exceeds its elastic limit.

Jeroen Belleman

 

[default]

On Tue, 27 Feb 2018 13:25:08 -0800 (PST), "malua mada!"
<fritzo2ster@gmail.com> wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

A phosphor-bronze spring leaf in tension against a copper or stainless
steel (resistance is not a concern) rail might work. Self-cleaning
only works if the wear (cleaning) is able to keep up with the growth
of oxides, so environment and how often the places are wiped count
too.

For short distances something like a spring loaded cable in constant
contact might work. (think: tape measure)

Conductive plastic strips...

 

[George Herold]

On Tuesday, February 27, 2018 at 4:25:16 PM UTC-5, malua mada! wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

An iridite or alodine coating on Al leaves it conducting, but I don't know
how long it would stand up to rubbing/ switching.

George H.

 

[Helmut Wabnig]

On Tue, 27 Feb 2018 13:25:08 -0800 (PST), "malua mada!"
<fritzo2ster@gmail.com> wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

Never slide two ident materials on another.
One side must be harder, one side softer.


w.

 

[whit3rd]

On Tuesday, February 27, 2018 at 1:25:16 PM UTC-8, malua mada! wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails.

Aluminum oxide is hard, and makes a good abrasive. That's not good for sliding
aluminum-on-aluminum. Copper is troublesome, because it enhances aluminum corrosion.
You can clean and abrade, then apply aluminum solder (a zinc alloy) which in
turn will solder-join to many alloys. Rivets also might work (but interfere
with the structure). If it's only for static, you might get away with a galvanized
chain (also amenable to the same zinc-alloy solder).

Or, you could weld a boss onto the structure, with
a tapped hole, and (using suitable paste) make a bolt-on electrical joint

 

[default]

On Tue, 27 Feb 2018 13:25:08 -0800 (PST), "malua mada!"
<fritzo2ster@gmail.com> wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

Way back in the ancient past almost all cars had grounding straps. The
tires were insulators, and the friction of autos moving through air
would cause static charges to build on the surface of the auto. (at
least that was the theory) The first passenger to step out of the
vehicle would be the one to discharge the static, and get shocked.

I seem to remember that you could get a pretty painful shock just
touching cars that were parked occasionally.

I seldom see a grounding strap so I assume they put some compound in
the rubber of the tire to bleed off static? I notice on my wife's old
Toyota I'd get shocked (only on dry days) when I touched the outside
of the car, but that may have been from sliding on the seat when
getting out.

 

[o pere o]

On 01/03/18 14:50, default wrote:

On Tue, 27 Feb 2018 13:25:08 -0800 (PST), "malua mada!"
fritzo2ster@gmail.com> wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

Way back in the ancient past almost all cars had grounding straps. The
tires were insulators, and the friction of autos moving through air
would cause static charges to build on the surface of the auto. (at
least that was the theory) The first passenger to step out of the
vehicle would be the one to discharge the static, and get shocked.

I seem to remember that you could get a pretty painful shock just
touching cars that were parked occasionally.

I seldom see a grounding strap so I assume they put some compound in
the rubber of the tire to bleed off static? I notice on my wife's old
Toyota I'd get shocked (only on dry days) when I touched the outside
of the car, but that may have been from sliding on the seat when
getting out.

I *always* go out of my car with my hand touching the metal first and
then putting foot on the ground.

Pere

 

[John Larkin]

On Tue, 27 Feb 2018 13:25:08 -0800 (PST), "malua mada!"
<fritzo2ster@gmail.com> wrote:

I need to bleed static out of a moving aluminum structure. I have a springy aluminum tongue (flashing) wiping on an aluminum arm (flat stock 1").
Continuity is good to start with but after a year or so fails. Wiping pressure is still fine, and continuity between any two points on either tongue *or* arm is fine but not between the two pieces.
I thought this was an improvement on a copper wire connection that would fatigue and break.
I also thought it would be self cleaning.
Thanks for any insights

It won't take much voltage to punch through the natural aluminum oxide
layer, or even deliberate anodize. Discharging static doesn't need a
connection that measures low resistance on an ohmmeter.

You could press a grounded sealed stainless-steel ball bearing against
the moving structure; that would last for many years.

There are also conductive brushes, like the ones used in copy
machines.

https://precisionbrush.com/custom-brushes-antistatic-brushes


--

John Larkin Highland Technology, Inc

lunatic fringe electronics