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Giant Wimshurst Machine - could use some guidance

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AwesomeMatt

Sat Aug 09 2014, 01:13AM

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

wrote ...
AwesomeMatt, how is the actual status of this project now? Did you perform some improvements futher or is it discontinued?

To be honest, I'm not sure. I have not been back to the science center where I built the Wimshurst since I last mentioned.

I thought their plan was to use my expertise to review and evaluate the proposals and quotes sent in by the professional fabrication shops, and then to tweak their designs. I emailed my contacts and the said they wanted to bring me into the process later, if at all, if further work on my prototype is needed for the fab shop.

So, they've now chosen a fabricator without my advice, for, I think, all 8 new exhibits (the Wimshurst is the centerpiece exhibit of these 8).

They have worked with this fabricator before. The shop has built several of their electrical exhibits, and they have experience making things like Hailstorm boxes, tesla coils, etc for other museums. They do pretty good work.

But, they seem to be very much mechanical engineer people. And, frighteningly, they seem to have (admittedly) sent in a (flexible) quote (that was accepted) for the Wimshurst without knowing anything about them.

And, I mean anything. It appears 100% of what they knew about Wimshursts was from my last video, that the science center sent them.

I had a 2 hour phone call with them, and they asked questions about the design that were the most basic possible. Like, 5 minutes of wikipedia or youtubing "What is a Wimshurst?" would have answered.

They were very nice and intelligent people, and, reassuringly, as I started to explain things, they admitted there was hubris on their part in bidding on the job without knowing a lot more. They didn't know it had 2 wheels. They didn't know they were counter-rotating. They didn't what the Leyden jars were or what they were connected to... nothing.

These are the "experts" that were hired instead of having me build the machine pretty and solid the first time (toss in some budget for a carpenter and a machinist). These are the "experts" who were going to put an engineering stamp on the electrical safety requirements.

Not to impinge them, again they are very kind, very intelligent, very skilled people for mechanical and finishing work. I'm just blown away that the people who reviewed the bid process chose this fab group as the most qualified for this particular project.

I understand it's a managerial role, but, jeez, it's a science center, when choosing a builder for an exhibit, one should at least have a comfortable enough grasp of the technology to ask the right questions.

...

I've asked (to reconfirm) if I could show off the prototype at the local Makerfaire coming up soon, as first agreed, but gotten non-committal responses.

...

Oh, and let me back up. BEFORE I even talked to the fabricators, the science center was thinking of pulling the plug, citing affordability from the quotes they received.

They were thinking of making 2 reductions to the exhibit:

1 - Reducing the interaction
2 - Reducing the "genuine spark creation"

I'm not sure what that means, but the only way you interact with it is by turning the crank (so no more turning a crank?) and I suspect the second item means they're going to have a lightningbolt shaped piece of foil painted blue between the electrodes and an audio speak going "zap zap zap", while a motor turns the wheels which do nothing.

But whatever, maybe they figure who cares about science, as long as there's a big wheel that turns and the media has something to show while they interview some director or VP in the foreground about all the amazing things they're unveiling. Because that "inspires" kids to learn more about science.

...

Oh, or, they may scrap the Wimshurst entirely and go with something boring.

...

Right now, I'm basically writing a "How to Wimhurst" document for the fabricators, *without* telling them exactly what to do, which is 10x as long as it would be the short way.

.

Antonio

Sat Aug 09 2014, 02:00AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Thank you for the updates. About interactions between "regular people" and Wimshurst machines, what I can say is that they will break it in little time because most people don't know how to turn a crank. I would keep the machine in a sealed enclosure, dry and clean, and drive it indirectly through a very solid crank, connected to the machine by some method that limits the force applied, the speed, the direction, and the time. A possibility is to use a fake crank that actually causes a motor to turn the machine in a controlled way. Other questions that could be better investigated are how to make brushes that don't break nor damage the disks, and a driving system without cords that slip and soon break.

Nik

Sat Aug 09 2014, 03:29AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

A cheap trick for "people proof" cranks is to put a loose belt from the crank to the machine. Over a certain torque the belt will slip, saving the machine.

RAJEEV TUTEJA

Sun Aug 17 2014, 01:58AM

Registered Member #46265 Joined: Sun May 11 2014, 06:01PM
Location: AMBALA CANTT, INDIA
Posts: 9

well my 36" machine islo ready but i have a problem.
as soon i connect the layden jars all the his his sound and the corona discharge dissappears. without layden its giving me three inch sparks. am trying now with a different layden jar will post pictures in a few hours. what am i doing wrong

Antonio

Mon Aug 18 2014, 12:13AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Probably Leyden jars with excessive leakage. Verify what happens if you first operate the machine without jars, and while it is sparking connect one of the jars to a terminal.

Newton Brawn

Wed Aug 20 2014, 01:31PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi Rajeev,

We are haappy to see your machine, let us see your pictures .

Regarding the capacitors tell us what materials and dimensions you have.

Regards

RAJEEV TUTEJA

Thu Sept 04 2014, 08:20PM

Registered Member #46265 Joined: Sun May 11 2014, 06:01PM
Location: AMBALA CANTT, INDIA
Posts: 9

some photos attached am getting 6-8 inches spark using 40mm dia and 1 1/2 foot layden jars.
would like to increase the spark lenght. any suggestions are welcome.
thanks and oblige. WATCH VIDEO AT

YOU WILL NOTICE THAT I AM SPINNING AT ABOUT 30 RPM my seven inch wheel driving 2 inches boss heads
anysugessions and improvements will be highly appreciated.
thanking you and oblige
regards
RAJEEV TUTEJA

Hazmatt_(The Underdog)

Fri Sept 05 2014, 02:47AM

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

That is a really great looking machine you have there!
Post some pictures!

Tony Matt

Fri Sept 05 2014, 05:15AM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

Hi Rajeev !

Your machine is so nice !!
Congratulations

I have understand that you have said that the acrylic disks have 12" WOOD DISKS, (the wood disks provide a shoulder to the acrylic discs)

I suspect that the wood disks limits the voltage of the machine. Is it possible reduce this wood disks to 6" or Less ?/

Regards

I also suspect some corona inside the capacitor dielectric that limmits the spark lenght. Do you mind to show us a sketch of the capacitors, with specs of the materiasl ?

Someone has a suggestion to increase the lenght of spark ?

RAJEEV TUTEJA

Fri Sept 05 2014, 08:31AM

Registered Member #46265 Joined: Sun May 11 2014, 06:01PM
Location: AMBALA CANTT, INDIA
Posts: 9

dear tony and hazzmatt
here are some pictures. i have reduced the size so they not come out very nice if you enlarge them.

1409905902 46265 FT163022 Img 20140811 113430

1409905902 46265 FT163022 Img 20140811 113647

1409905902 46265 FT163022 Img 20140811 113658

you can see some other layden jars laying on the table in the last two pics

maybe if you like i will upload 2-3 videos on you tube

dear newton,
i tried four different types.
1. PVC pipe used in electrical fittings in homes dia 40 mm, length one and a half foot, spark 6-8 inches with a bang like a shotgun. 120 decibles at 6 foot to be exact, and the light as i have posted in video on youtube shot in broad daylight at afternoon with the sun on top of my head. at night it looked like a welders arc illuminating area upto 100 meters.
. -do- dia 70 mm spark 7-9 inches a litter louder sound and brighter light.
3. pvc jar 6"H*4" base inside outside aluminium foil .4 mm thick result same as 1
4. -do- "h*5" base result same as 2.

by the way the layden jars no. 1& 2 were filled with pure aluminium fine cuttings precured from chemicals dealer used in chemical labs.a brass rod was then inserted into them. if anyone wants i can draw its diagram in coreldraw and post on this forum with complete instructions to make them. but it will take me a week to post them as i am going to mumbai and pune for a few days.
jars no. 2 and 3 with al. foil inside and out with a chain in the jar type of laydens

dear tony,
sorry i forgot to metion you in my last post.
the wooden disks were made up of dried heat fire and water proof plywood as used in high end furniture so i dont think there was any leakage due to them.
regarding your second question i will surely provide complete details but please give me some time.

TILL NOW NO SUGGESTIONS FOR IMPROVING SPARK LENGTH.

any suggestions will be highly appreciated
thanks to all of you out there
regards
RAJEEV TUTEJA

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