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TDU has twins

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Tesladownunder

Fri Aug 21 2009, 04:20PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

This is to announce the arrival of my twins. I hope this is the start of something wonderful and that you will see a lot more of them as they mature.
Lots of little "different things" about these coils. Like the individually wrapped caps to allow a compact MMC and coax feed for the primaries (parallel wiring), plastic wrap on the secondaries, spherical toploads etc.
This is a part only of my big project which is still under wraps with a lot of development and design to come.

Specs: 4 x 20 inches 1260 turns, 8 inch spherical toploads. Cylindrical primary.
Driver is an SISG (Twin MOT Piranha from Terry Fritz using 5 of Mark Dunn's boards)
Sparks to 40 inches.

Coronafix

Fri Aug 21 2009, 11:03PM

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

I love your primaries, very nice looking! Why did you use plastic wrap around the secondaries though? It takes a lot of time, but 10 or so coats of enamel is so worth it.

Tesladownunder

Sat Aug 22 2009, 01:12AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Coronafix wrote ...

... Why did you use plastic wrap around the secondaries though? It takes a lot of time, but 10 or so coats of enamel is so worth it.

A lot of time is a commodity I don't have particularly as drying time is a bit hard to come by in the weather we are having at present. At present I need a knockabout surface while it gets tested and installed in the setup I am planning. Originally I had planned a corrugated plastic surround like Greg Leyh's one at Maker Faire but I need a Steampunk theme so I am a little undecided yet.

The primaries do look neat and were easy to do and it is easy to adjust coupling too. I will probably fully cover the primary winding with split clear plastic tubing to preserve the copper sheen.

I needed a low profile primary. The topload will be a "new" design too with a visible internal structure that does things....

Here is an earlier shot using an old conical primary for testing. And yes there is a lot of top turn corona because the secondary is mounted upside down because that's how the screw in connections mated. That is not a problem now but what is, is the primary to secondary corona. I suspect that this is how I blew my MOT. It is due to capacitative leakage of the individual TC to ground which returns via the mains cord/earth. I may have to devise a fix for this, like a better direct earth and lots of MOV's.

1250903551 10 FT74768 Sisgsingle48cmsparksmalltoroid

Coronafix

Sat Aug 22 2009, 10:24AM

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

Tesladownunder wrote ...

A lot of time is a commodity I don't have particularly as drying time is a bit hard to come by in the weather we are having at present.

I use a motorised winder (cordless drill) that I set to rotate at not too fast a speed, apply enamel quite thick and put a heater in front of it. In a couple of hours it is dry enough to stop rotating and switch off the heater. 24 hrs later I repeat process. Of course for ten coats it is ten days, but the end product is the first thing people comment on. "Ooohh, shiny...." :)

Herr Zapp

Sat Aug 22 2009, 03:49PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Coronafix, TDU -

Regarding secondary coatings, drying time, 10 days of applying thin coats of varnish, etc.:

1. A single coat of clear two-coat epoxy gives a finish that is as-thick or thicker than (and more durable than) 10-20 coats of varnish.
2. The epoxy cures hard regardless of amblent humidity, and has only a fraction of the "wet-time" of multiple coats of varnish, when it is susceptable to picking up bits of dust, lint, insects, etc. It is affected by ambient temperature, by curing more quickly at elevated temperatures.
3. Just like varnish, it requires a motorized fixture to keep the secondary rotating until the epoxy has gelled.

Regards,
Herr Zapp

Tesladownunder

Sun Aug 23 2009, 12:55PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I am aware of Envirotex and also multiple coatings.
Neither may be relevant here for two reasons. My project may result in this being prone to bump and scrapes (while off!). It needs to be transportable too. An exterior replaceable covering may be preferable to a beautiful shiny surface in a static installation.
There is one big advantage of the thick coating of Envirotex in that it helps disperse errant strikes to the secondary. While this is a low power installation it has the difficulty of variable earthing. Problem in this area will give primary to secondary sparks and even on a minor setup I am seeing a bit of corona in that area.

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