A 15cc sidevalve opposed twin

[Ken I]

Peter,
Looking great thus far - learning curves are a sod.

Re previous comments on thief rings etc.
You want to have a uniform current (amperes per square inch) all over by provision of anodes and "thief" cathodes. Alas practice is invariably a compromise on theory (AKA just not possible.).

If you have areas that exceed the maximum rate, you may just produce mud, get too low and you may just produce nodules - or vice versa - confounding variables.

Moving the parts about in solution (as done for through hole PCB plating) or rotation (with obvious commutating problems - solved by just rotating backwards and forwards) or simply moving the solution about via a pump or impellor. Relative motion also helps increase deposition rates by clearing the diffusion layer away from the cathode. (A'la YRPS - Yamaha Rapid Plating System which typically deposits Nickle and Chrome at very high rates.)

Regards, Ken

 

[Peter Twissell]

Thanks Ken,
I had considered using a fish tank pump to circulate the electrolyte, but I was concerned about introducing bubbles. I have a small pump, but even that generates a storm in my 1 litre bath! Also, I am a little worried about the effect of the electrolyte on the internals of the pump.
Ideally, I would use a magnetic stirrer.

So far, excess build up at edges appears to be trivial. In any case, I will be silver soldering flanges to the ends of the tubes, so a bit of extra wall thickness there may even be desirable.

 

[methuselah1]

Have you considered using an old saucepan and using the whole tank as the anode, Peter? You've got stainless steel, aluminium and copper to choose from.

Another thought is to use an automotive washer pump- 12 volts, gear type with plastic workings and low out put. Ditto for using a wiper motor to impart reciprocating motion.

 

[Peter Twissell]

A copper tank would do the job, but it would require care to ensure that it didn't erode away through the bottom.
My anode is a piece of domestic plumbing pipe and about half of it is gone already!
Other metals in the electrolyte are a no-no.

 

[Ken I]

Peter,
Laboratories use a magnet in a ceramic case - driven remotely by a further motorized magnet under the beaker - maybe a lash-up ?

Correct - you don't want to entrain bubbles.

The anode is obviously sacrificial but you can use heavy gauge copper wire quite liberally - I don't recommend ever using the tank as an anode - in my experience even accidentally making the tank the anode results in disaster - besides anything other than copper is going to ruin your electrolyte.

Regards, Ken

 

[methuselah1]

Peter,
Laboratories use a magnet in a ceramic case - driven remotely by a further motorized magnet under the beaker - maybe a lash-up ?

Correct - you don't want to entrain bubbles.

The anode is obviously sacrificial but you can use heavy gauge copper wire quite liberally - I don't recommend ever using the tank as an anode - in my experience even accidentally making the tank the anode results in disaster - besides anything other than copper is going to ruin your electrolyte.

Regards, Ken

Magnetic stirrers (pills or fleas in lab tech slang) are cheap enough to buy- but the hotplates with the motorised magnet generally aren't. I was looking at them the other day for some reason. However, when I was a lab tech, I scrapped dozens of dud hotplates, (ammonium chloride kills them) but saved a fair few of the magnets, and if you want to try that method, I can get one in the post for you.

I like your end of mail quip, Ken- but its funnier if you write "I'd rather have a full bottle in front of me, instead of a full frontal lobotomy"! And try saying that after a few drams!

 

[Peter Twissell]

Thanks for your kind offer.
I am now planning a more "professional" setup, with integrated heating and electrolyte circulation, multiple anodes and filtering to prevent debris from anodes from arriving at the cathodes.
I have in mind a peristaltic pump.

 

[Ken I]

Peter, Amongst other research while you are looking - look up "Hull Cell"

This is a small glass plating bath with the anode and cathode at an angle to each other - giving a variable current density across its face.
It is used to determine the optimum value for your solution - or to determine on a small scale what any changes or remedial actions will have on your solution.
When you have a tank with 20000l of chromic acid (as I did) you don't make changes or additions without first testing it on a small scale.
You can obviously lash this up and use it to determine optimum current density.

I only ever pumped chromic acid with peristaltics or magnetically coupled pumps - each have their own quirks - the wierdest was the magnetically coupled did not like running without back pressure - would cavitate and fail to deliver - even with flooded suction ? I suspect that the driver and driven bar magnets accidentally worked like an induction motor with the driver bar inducing a current in the driven bar - thus repelling it into the arms of the next pole - a vicious circle resulting in a low torque speed multiplier - it simply ran away at speed if not presented with resistance creating an impenetrable cavity that not even flooded suction could penetrate ? One of the wierdest phenomena I have seen. It may have just been a quirk of the particular brand of pump - but wierd nonetheless.

Regards, Ken

 

[Peter Twissell]

Success!
The pair of exhaust pipes came out of the bath after 33 hours looking like this.

 

[awake]

33 hours - sounds exhausting!

 

[Peter Twissell]

A little cleaning up with a fine file soon got the bobbly surface back to amorphous copper.

Both ends cleaned up to the desired 1mm wall thickness.
Some areas are only 0.4mm thick, which is a little thinner than I'd like, so they will go back into the bath with the anode closer to the thin areas.

 

[Peter Twissell]

Fortunately, the process can be left to run unattended, so 33 hours is not so much of a task.

 

[awake]

That was supposed to be a pun. Exhausting ... exhaust pipes ... yes, pretty feeble, but I do what I can.

 

[Peter Twissell]

The pun didn't escape me.
I just decided not to pipe up about it.

I'll get my coat....

 

[awake]

Oh ho! You do know that punsters cannot stand to be ignored. A groan is taken as a compliment. Silence ... just hurts.

So in that vein ...

I just decided not to pipe up about it.

Groan!

 

[Steamchick]

Pipe down and get back to topic....
The plating thickness is not based on proximity of anode, but electric field strength - which in turn is based on shape! Which is why the inside ( where there is almost no electric field ) will be unplated. The Rough surface bobbling you experienced is also a field-strength issue. As soon as the deposit of new copper starts to get even microns uneven, the election field strengthens locally where there are peaks, so builds more rapidly there than in the troughs. The way to build any coating thickness electolytically, is to stop every hour or so and polish the surface level again. (Use very fine wet n dry paper?). Just like paint film building.
Enjoy - and we'll done so far.
Just an odd question... why copper plate the exhausts? Will you nickel plate, then chrome on top? If so, why do you need such a thick plating? If you intend just polishing the copper, it will colour and burn black oxide, depending on how hot it gets. I have discoloured copper pipes from my boilers with the temperature of super-heated steam.... not as hot as your exhaust gases?
Now I am hot, exhausted, and too blown way for more comments...
K2

 

[Peter Twissell]

Hi Ken,
Thanks for the tips.
It was my understanding that anode proximity had a direct effect on current per unit area and therefore deposition rate.
My exhausts are not copper plated, they are copper!
The part I am plating onto is a sacrificial 3D print, which will be dissolved out later.
I will nickel plate the pipes after I have silver soldered the flanges on.

 

[Steamchick]

Thanks Peter. That clarifies your need for more wall thickness.
K2

 

[Steamchick]

I am a bit surprised you can't bend pipes from copper tube?
K2

 

[Steamchick]

Hi Ken,
It was my understanding that anode proximity had a direct effect on current per unit area and therefore deposition rate.
My exhausts are not copper plated, they are copper!

I guess that if you use a small anode, close to the zone you want plating, the locally the electric field will be a bit stronger. It relies on the inverse square law. But most plating keeps the anode further away to try and obtain a more uniform field. I'm sure you are using CAD for the component design, so load-up an electric field programme to look at your proper anode shape and placement.
K2