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Giant Wimshurst Machine - could use some guidance

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LAN_403

Eleccentric

Tue Jun 10 2014, 05:51AM

Registered Member #33460 Joined: Tue Aug 27 2013, 06:23PM
Location: Seattle
Posts: 46

Awesomesauce! No, don't worry about it only doing 8" without the Leyden jars. The sparks will be muuuuuch longer once you have those in place and sized properly. Your neutralizer brushes are set quite high/steep, but it doesn't seem to be negatively affecting operation.

Once the jars are attached, there will be a heavier electrical load on the machine and you should feel it take more energy to turn, or else your discs are too far apart and you are only getting a fraction of what the thing is capable of producing.

Regardless, congratulations on a crazy huge machine!

AwesomeMatt

Tue Jun 10 2014, 09:22PM

Registered Member #4454 Joined: Sun Feb 26 2012, 12:47AM
Location: Western Canada
Posts: 74

I found a capacitance meter.

Leyden jars without endcaps put on are 1.53nF and 1.57 nF each.

3.10nF.

At 300,000v...

140 Joules. About the energy of a .22LR bullet.

Umm...

Terrifying.

Back on page 1, people said I might have as high as only 30 joules, which would be an impressive bang. 140 is.. MORE IMPRESSIVE.

Well, time to finish them up and see just how loud they are.

I got consistent 12" sparks (1hz) today (could hear but not see), without any capacitors.

Ash Small

Tue Jun 10 2014, 10:42PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

AwesomeMatt wrote ...

Leyden jars without endcaps put on are 1.53nF and 1.57 nF each.

3.10nF.

I think in series, the capacitance is halved. I think you need to re-calculate. I've had a drink, though.

Awesome machine, though

Eleccentric

Tue Jun 10 2014, 11:02PM

Registered Member #33460 Joined: Tue Aug 27 2013, 06:23PM
Location: Seattle
Posts: 46

Yes, that is only 150kV on each jar, but even so, those may be bigger than you need. Wear hearing protection when you first fire it it up.

So far your machine seems to be acting normal - the "failed" sparks that you can hear but not see happen with my machines as well if the electrodes are too far apart.

2*0.5CV^2 = 34.875 joules (using 1.55nF and 150kV) Much more reasonable!

Hmm.. ..0.5CV^2 = 34.875 joules (using 775pF and 300kV) So I'm pretty sure I've got that right.

AwesomeMatt

Wed Jun 11 2014, 05:35AM

Registered Member #4454 Joined: Sun Feb 26 2012, 12:47AM
Location: Western Canada
Posts: 74

Well... frustrating turn of events.

Coincidentally, the day I provide them with a functioning prototype, is the same day they (bigwigs, different than before) decide, retroactively, they don't have the budget to build one (the prototype, they still have buckets of money for the fabbed version based on all the documentation, measurements, etc from the now-finished prototype).

They approached me and asked me to do this, not the reverse. I've been regularly communicating the costs to them, and gotten repeated assurance it was within budget and to keep progressing. Of course, working on trust and not legal documents, I don't have much legal recourse for time or materials.

Which is fine. If you can't trust someone without a contract, at sub 6-figure ranges there's not much point in trusting them with one either. Lawyers win it all anyway and I don't want to live my life in litigation.

I'll try tomorrow directly with the person who made the decision to see if it's just miscommunication, but, I wouldn't even say my mood is cautiously optimistic.

Oh yeah, so, it's done. Just waited for the PVC glue to dry on the Leyden jars before I could test it.

Bittersweet.

Patrick

Wed Jun 11 2014, 06:57AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

thats crap on a stick...

AwesomeMatt

Wed Jun 11 2014, 07:32AM

Registered Member #4454 Joined: Sun Feb 26 2012, 12:47AM
Location: Western Canada
Posts: 74

Ehn, let's see what happens tomorrow. I'll give them the opportunity to save face, maybe it's all a big misunderstanding.

Finn Hammer

Wed Jun 11 2014, 08:10PM

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

AwesomeMatt,

Whatever happens, you have done an outstanding job with this prototype, and that is your intellectual property, the hands on knowledge about how to build a large Wimshurst. Not many people try that.
And it has been very interesting to follow this thread!

Cheers, Finn Hammer

Hazmatt_(The Underdog)

Thu Jun 12 2014, 03:09AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Wonderful to see that IT LIVES!!!

1. NEVER trust anyone with money. They don't make or keep money by spending it.

2. They will probably aim to steal what they can from you. You've already done all the footwork for them.

3. I can't tell you how many projects I've done for people that had big mouths and never paid. This is what happens when you do a job for a dreamer.

4. You come first. No more work until there is reimbursement. Labor is worth something, you need to be compensated for materials AND labor.

5. SOW. Statement of Work. Always get a statement of work, regardless of contract. This ensures no miscommunication.

6. Reserve the right to refuse work if possible. You shouldn't have to let the customer break your arms so they can have a pretty spinning gadget.
I have a hard time with this one because I do help people who don't know what the hell they are doing, and to my detrement. It's better not to.

-Matt

Dr. Slack

Thu Jun 12 2014, 07:41AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Going back to your OP, you've been 'brought in on a team'.

So the machine so far, who's paid for all the acrylic and stuff? You, or multiple people across the team? I'm trying to understand actual ownership of the machine or its parts.

Where I'm going with this is, if it's all your stuff, and you haven't been reimbursed for it, it might cross your mind to take it off site.

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