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Finn Hammer

Sat Feb 13 2010, 10:17PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Steve, Yes, I will use the Predikter coz I think it is pretty good too!

Anyway, I settled for the easy way out: 2 brushes. Below are details:

The carbon brush to the right is just there, because I didnÂ´t use that option. Daniel did, and he will harvest the consequences of that decision.
I decided to wrap lengths of RG-218 screen stocking around blocks of tufnol, clamped at the back with a copper block, which also acts as attachment for the tapping cable.
Seen from the front:

With one of the brushes protruding.
The front face of the tufnol stock is lapped to the curvature of the primary coil, and the fit would appear to be acceptable:

A view from the rear exposes the 4 possible connections to tapping point cable and reveals that I have not yet figured out how to make the spring that presses the brushes against the primary coil. I will tomorrow.
The 4 brass details that meet with the primary coil on the inside will be replaced with miniature ball bearings, as soon as they arrive.

Thanks for looking.

Cheers, Finn Hammer

Coronafix

Sat Feb 13 2010, 10:50PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Nice work Finn, but how does it travel along the primary?

Finn Hammer

Sat Feb 13 2010, 11:04PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Coronafix wrote ...

Nice work Finn, but how does it travel along the primary?

At the bottom of the primary coil is an arm, with a vertical stick that engages with the tapping point carrier. When the arm rotates, the tapping point follows.
As the work progresses, you will see it in detail.

Cheers, Finn Hammer

Killa-X

Sun Feb 21 2010, 12:24AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

So work is still going strong on this system? I recall you getting some very nice long streamers :) Keep making things look small and cool i guess!

Finn Hammer

Sun Mar 21 2010, 06:06PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Aarrrh! The smell of tufnol in the morning!

When coiling gets serious, the material of choice for select parts is Tufnol.

On a coil of this caliber, a surface finish of lesser quality than that produced by a tungsten carbide milling cutter would be an abomination.....

The primary assy' is tufnol, brass and stainless, except the high class Maxon DC-motor used to drive the adjustable coupling arrangement.

In this closeup, you can see the mechanism that will allow me to adjust the coupling of the coil, real time. It has been tested and verified to lift my 85Kg!

Cheers, Finn Hammer

Coronafix

Sun Mar 21 2010, 08:59PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Nice work Finn! The coupling adjuster is ingenious.

Nicko

Sun Mar 21 2010, 11:04PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Is that a hinged top by any chance - it looks like it...

...I only ask as its important to keep the bolts done up:

Amazingly, they fixed it (although it took 6 years) and it was launched in Feb '09...

Finn Hammer

Mon Mar 22 2010, 09:31AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Nicko, you are right.

Without it, it is a struggle beyond description to get the secondary with attached topload upright on the primary assy'. This coil is big enough to warrant the use of a crane, but we don't want to depend on cranes.
With this hinged platform, we can open the hinge, attach the secondary while it is lying in a horizontal position and then, with the bottom secured in position, just flip it up into vertical.

The space hardware you linked to looked like it had completed the same motion, but in reverse ?

Cheers, Finn Hammer

Nicko

Mon Mar 22 2010, 03:37PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Finn Hammer wrote ...

The space hardware you linked to looked like it had completed the same motion, but in reverse ?

...not only in reverse, but unintentionally (not that anyone would intentionally drop a satellite). It cost USD 217million to fix.

The lesson? Make sure if anyone borrows your nuts, they ask first !

Finn Hammer

Sun Mar 28 2010, 05:37PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Had a couple of hours to spare, so turned to Thumpa'

It would be an act of vanity to asume, that the primary coil could be produced completely round. Also, that the assembly that drives the tapping point along it, is centered with enough precision.

In the ordinary coil, this is of no consequence, but this is no ordinary coil.

So some sort of mechanical buffer has to be inserted between the driver and the driven, to keep it from jamming.

Inserted are 2 blades of 0.2mm thick G10. They act as leaf springs, giving the tapping drive stick unrestricted axial movement, within amble reason.
Took 4 hours to design in Solidworks, 3 hours to complete in real life.

I had put the solution to this problem out, due to it containing many parts to solve just one problem, so I am happy that it is now in the book.

Cheers, Finn Hammer

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