Minibrute Construction Thread / FAQs / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Minibrute Construction Thread / FAQs

first previous 38 39 40 41 next last

Move Thread

LAN_403

HV Enthusiast

Fri Apr 30 2010, 04:59PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Thanks to everyone for their comments and errors you pointed out, i have summed them up into a single document.

You can access the PDF addendum here:

http://www.easternvoltageresearch.com/drsstc_minibrute.html

raysf

Mon May 03 2010, 06:54AM

Registered Member #2845 Joined: Mon May 03 2010, 06:40AM
Location:
Posts: 12

Hi Just joined the forum and am working on building a Minibrute kit, which is my first Tesla coil. Just got it soldered together and it passed the smoke test. I have a question about the enclosure: The coil is going on a piece of metal artwork, and it would be much more optimal as far as aesthetics and construction if the housing at the base was metal. Assuming good precautions against shorting the electronics to the housing were taken, maybe even with some plexiglass under the high voltage boards, could there be any other issues with this?

Edit: One other issue I thought of might be the primary causing inductance in the metal housing and heating it up/wasting power, so I guess i'd just cut a gap(like a very thin pie slice) into the housing from the center to the outside and fill it with something nonconductive.

UnionTesla

Wed May 05 2010, 09:19PM

Registered Member #2685 Joined: Sun Feb 14 2010, 07:23PM
Location:
Posts: 11

Because I am building the minibrute through a University, safety is a very important aspect. I can see the different types of grounding equipment people use, but I am wondering what exactly they consist of and how they are constructed. Can anyone help?

HV Enthusiast

Thu May 13 2010, 02:27PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

UnionTesla wrote ...

Because I am building the minibrute through a University, safety is a very important aspect. I can see the different types of grounding equipment people use, but I am wondering what exactly they consist of and how they are constructed. Can anyone help?

Not sure exactly what you mean by this question. What do you mean by "grounding equipment?"

raysf

Sun Jun 06 2010, 05:36PM

Registered Member #2845 Joined: Mon May 03 2010, 06:40AM
Location:
Posts: 12

Hi,
I'm wondering about the maximum frequency for doing audio modulation. Further back, I saw evr say that the xenosonic goes up to about 2 khz. Assuming duty cycle is held to a fixed percentage, what kind of bad things could happen if you go above that?
I made a microcontroller based audio modulator that seems happy up to about 6 or 7 khz and keeps a set duty cycle, but for now I limited it in software to 2 khz. We've got to have the tesla coils going for a show in 3 weeks, so i cant afford to blow too much up before then!
Cheers
Ray

Rollingblackout

Mon Jun 14 2010, 05:25AM

Registered Member #1524 Joined: Sun Jun 08 2008, 05:25PM
Location: Grand Junction, Colorado
Posts: 38

Hello,
After almost a year in storage I got my miniBrute back out and to my delight It still works just like it did when I put it up. Less one minor issue with a modulator power switch.

I was never able to get the desired out put so I thought I would revisit the fine tuning. After looking through the advanced tuning section of Dr. McCauley's book on the miniBrute I have come to the realization that I have no idea what I'm doing here.

So as I commonly do I just fiddled with the primary tap at first moving it 1/4" at a time and documenting the output with markers. until I found no improvement in spark length to primary current. The best length of arc to a grounded object is 21".

I built my toroid with mandrel bent 3.5" 90 degree tubes welded them together and polished them up. this is out of the build spec a little so I threw a 3" sphere on to for good measure. Today I went to the hardware store and picket up a 4" aluminum duct to make the correct dimension of toroid 4" x 13". I performed the same primary tap adjustments and ended up a little short at only 20".
Back to the original 3.5 x 13" toroid and a final best primary tap location of 5.5 turns.

video of coil at 318hz prf and 150us pw

Also my variac is only capable of direct output so my input voltage is limited to 121 vac. Other then that I believe every other part of my build is within spec.

I also found the breakout point or its total distance from the toroid has a little bit to offer in regards to adjustments.

Are there any other areas I can address to try and achieve greater performance with out putting the system at risk?

Martin King

Tue Jul 27 2010, 04:32PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Hi, I've just joined the forum after receiving the miniBrute reference design book. I've already ordered up all the plastic and copper stock. I'm going to try and spin the top toroid myself but have a local spinner preparing a quote as a back up

but I suspect a one-off will cost far too much

. I'm going to wade through all the previous posts at some point but to answer some recent questions (sorry if they have been answered in previous posts) When bending copper tube if you fill it with dry sand or molten wax and then seal the ends it helps prevent crushing while you bend it although you still need to bend it carefully a little at a time. The "proper" but expensive way to do it is to fill the tube with a very low melting point alloy such as "woods" metal WARNING contains cadmium=nasty, although I think there are safer versions around.

Martin King

Tue Aug 10 2010, 07:26PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

OK so I've started building the mechanical bits of the miniBrute, I'm a bit annoyed that the addendum doesn't mention a couple of mistakes in the mechanical drawings/items list, although luckily none of them are major problems, also I feel it would have been better to have the 0 datum either at the edge of the plate or reference everything from the centre line, Having the datum 0.75" in from the edge is a pain for marking out and a calculator error meant I had two holes in the wrong place but luckily they were only small pilot holes and are covered by the primary coil supports. Now to my main question, there is a central hole shown in both the mounting plate and the coil base that doesn't appear to be used for anything? Of course I drilled the holes before I noticed they're not used and I was wondering if I could use it as a plug/socket connection between the secondary and the base to make the coil easier to dismantle for transport/storage are there likely to be any issues with doing this e.g. arcing in the connection? Another option would be to use a brass bolt and make the ground connection with a solder tag and brass nut, again are there likely to be any issues with this?

Cheers.Martin.

Martin King

Tue Aug 10 2010, 09:23PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

BTW is there anyone else here (particularly UK based) building or looking to build a miniBrute? If so I have a list of useful UK suppliers that I've found so far. Also I will very likely have some surplus parts that I can post in the sales forum if anyone's interested, particularly (as it stands at the moment) Metric screws and inserts, PVC offcuts, imperial drill bits (for the primary and strike rail support holes) and copper bar for the strike rail post. I'll probably post what I have left over in the sales forum as one big post anyway at the end of the project but if anyone has any particular needs now them PM me.

Cheers.
Martin.

Martin King

Thu Aug 12 2010, 12:26AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Hm, wound the primary coil tonight, does it normally take four hours ?!?!?! Everything was as per the book, PVC supports, hole sizes, copper diameter etc. I even chamfered the end of the tube with a file to reduce the chance of it sticking in a hole and lubricated the tube/holes. After the first turn I had to take out one screw from each support and loosen the other so they could float a bit, this improved things a bit but not much and after I'd eventually finished it was a real bitch to get the supports back into alignment and get the screws back in

Martin.

first previous 38 39 40 41 next last

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob