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Giant Wimshurst Machine - could use some guidance

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AwesomeMatt

Mon Jun 02 2014, 10:12AM

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

Well, won't be done *before* Monday, might not be done on Monday either.

Lots of video, no pics though, ran out of the building at the last minute before lockdown.

Progress for today:

- Shopped at Princess: 2x 3" sheaves, 5/8" bushings, 5/8" bolts, 5/8" washers
- Shopped at Lowes: 4x 10-32 threaded rods (replacements), small washers
- Disassembled disc, upper axle, lower drive assembly, frame, platform. Nothing left together.
- Migraine arrives, perfect timing.
- Chopped up frame cross bracing to new sizes. Reassembled frame. Is lower, will not short discs anymore.
- Reassembled platform, new spacing, 285mm separation inside frame. Should avoid other shorting issues.
- Drilled out new double-pulleys to match their twins.
- Used hydraulic press to disassemble jammed-on pillow block bearings from lower axle.
- Reassembled pulley triple-stacks, while trying to straighten crooked pulleys with holes that wouldn't line up until they were pulled straight by the bolts. Took forever. Stripped several bolts, used longer ones with plain nuts, hacksawed off excess threads (needs to fit closely), unthreaded nuts to autocorrect bolt threads, re-threaded with delicate but anti-vibration nylon nuts,
- Reassembled, adjusted, re-mounted lower drive assembly. One pulley was so deformed the other 2 couldn't straighten it, just averaged it out. Ugly but should be functional.
- Realized when I reassembled the frame & platform, I didn't square or center any of it. Discs will tear apart if not straight. Disassembled all of it, squared it, reassembled all of it. Migraines are exciting.
- Measured & cut upper axle PVC spacers.
- Lifted Disc #1 to final position, with PVC & Nylon spacers.
- Lifted Disc #2 to final position, with spacers. Exhausting trying to lift, and reach to the far side of, 150 pounds worth of acrylic that I can't see around, on a shaft that keeps sliding out of the way, when nothing can get scratched. Will be doing this at least once more, not alone next time.
- Figured out distance spacing for flat pulleys (the 3"), also calibrated height.
- Sourced and chopped material for pulley mounts.
- Drilled & mounted both pulley mounts onto lower frame.
- Skeptical of washer hose as a belt. Skeptical of charge rate. Skeptical of pulley ratios. May go buy oring cord or something more substantial tomorrow since everything's open again. Calculated edge speed of counter-rotating discs, 48" in diameter moving 2 handle cranks a second at 12:1 ratio, to be exactly 666 km/hr. That's as fast as a jet airplane. It's either crazy, or wrong. Now is not the best time for me to confirm that.

If I get a belt on it... it's ready to twirl and dance.

Then I need to take it apart and put the sectors on it.

And finish all the actual electrical stuff.

With setbacks, probably a full day behind, maybe 2.

Am putting like, 14+ hour days into it. Slow going but not much I can do about it, already throwing all my time into it.

Eleccentric

Tue Jun 03 2014, 03:04AM

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

I don't think you did your kph calculation quite right. I work it out to be about 205 mph, or about half your stated speed. This is still much too fast.

I think you need a lower pulley ratio, or else cranking this thing will be very difficult once it charges.

AwesomeMatt

Tue Jun 03 2014, 03:15AM

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

I just tried running a belt to hook up this mechanism that avoids crossed belts.

(Courtesy of Finn).

... I'm an idiot. Clearly, one of the giant pulley pairs has to be slipping. They can't *both* be locked onto the shaft.

FFFFFFFUUUUUUUUUUUU...

Need to be drilled out and a bushing put in on one of them. The plastic wheels are super grippy even if I loosen the set screw.

Bonus though... I don't need to disassemble the machine to put the belt on. I can make it and then install it after. I think...

HOLY SHIT.

I spun it up to speed and it didn't detonate on me.

No sectors, no neutralizers, no combs, no Leyden jars, but, it sort of actually mechanically works!

wrote ...
I think you need a lower pulley ratio, or else cranking this thing will be very difficult once it charges.

Argggggg....

Well they pulley ratio was the one thing I didn't bother to do myself. It was spec'd to me. I should have just thought about it and picked my own.

All this trouble with the stupid mounting of the 1" pulley... if I would have gone with, say, a 4" pulley I would have had lots of room to bolt to, no scary torque issues, no balancing issues. Hrmph.

...

Balls went together easier than expected. Just tapped the holes and screwed them onto threaded rod.

2033

I think they need a spacer between the balls. I was thinking, just a 1/2" or so chunk of 1/2" copper pipe, sandwiched in there, and hopefully no need to solder and such?

Right now the end of the 1" copper pipe has a flat end, that's what I'm screwing into. Would it be better to have the ball meet the copper pipe flush, without the flat? I can hammer in a chunk of wood with a nut bashed into the far side, and just screw the ball directly until it's touching the pipe edge.

Also, here's it's first spin. (It wobbles because the table it's on is a rolling worktable and I'm leaning into and out of it, not because the machine wobbles).

Today's progress:

- Tried to buy carbon fiber brushes. Record cleaning brushes may be carbon fiber? Store #1 has nylon only, Store #2 is closed Mondays, Store #3 won't pick up a phone.
- Tried to buy Oring cord. NAPA says they special order from Gregg's. Gregg's Distributors doesn't know what that is, Hitech seals has some but won't get there in rush hour before they close.
- Noted frame was leaning, cut support blocks and secured. Output braces later should help.
- Adjusted lower assembly to center.

2034

- Drilled out flat pulley mounting holes.
- Mounted flat pullies
- Experimented with belt paths.
- Realized one triple-stack pulley will have to be freewheeling on axle, obviously, can't have both going the same direction. Lots of friction from plastic pulleys, need to drill out and add bearing, later.
- Shuffled one flat pulley for necessary offset.
- Measured, cut, superglued belt.
- Realized belt was tied in a knot, ripped apart, reglued. Wrapped with scotch tape to make smooth.
- Realized upper and lower drive assembly requires disassembly to change belt, unless flat pulleys are inside-outside rather than staggered. Requires a larger pulley on one side later.
- Belted up machine. Seam held up!
- Gave machine test spin. It actually worked. Seam gets caught in pulley grooves, no big deal. Slips under startup and is ridiculously tough to turn, takes a couple minutes to reach speed and had me sweating. Whatever, it works!
- Test drilled conb pipe with microbit, seems to work.
- Drilled out output support pipes to accomodate comb mount. No drill size close enough, manually reamed.
- Attempted to tap output globes. $25,000 Shopbot? Check. $10,000 lasercutter? Check. 8 fancy dust collecting systems plumbed to every cutting tool? Check. 3 welders, mill, lathe, tooling? Check. $5000 in nut and bolt hardware? Check. $15 tap set? Not in the budget. Just a few misc pieces. Super. Made one work, tapped small globe, threaded, seems to work minimally but sufficiently. Tapped both ends of a large globe, wonky but works.
- Need to drill out copper endcap for threading. Drillbit smaller than 7/32"? Nope. Super. Hammer and reaming.
- One output electrode done. Done-ish. Needs some tubing spacers. Good enough for now.
- Cut pipe for temporary neutralizer mounts. Works okay.
- Mocked up assembly, made notes of what might cause issues.

2035

Issues:

1 - I kind of ignored where and how to mount the neutralizer brushes. I will probably cut that axle short, but even then, they stick out pretty far. They're close to the output electrodes. That'll be an issue, no?

Maybe shove them where the PVC sleeves are.

2 - Comb pipes aren't long enough. No matter, was just the leftover chunk, will cut more.

3 - Intended to cut acrylic supports to hold output posts steady to center post. Neutralizer brushes are in the way.

4 - Discs are a little far apart. Oh well. Could trim the spacer, but, I'd rather just charge the machine slowly but *not* have a catastrophic crash.

Won't make the deadline tomorrow don't think. Have other commitments.

RAJEEV TUTEJA

Tue Jun 03 2014, 05:44PM

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

dear Newton Brawn

sorry for the late reply.
i used 4 flathead screws to bolt wooden 12" 5 mm disk to 36" acrylic and the wooden pulley in that order.
for spaces between the disks i used thruster bearings with teflon sheet cut to bearing size to avoid any friction between them and the sheets.
hope this helps.

regarding pulley ratio mine is 3/7 i:e 3" wooden in the center with 7" driving pulleys

Dr. Slack

Tue Jun 03 2014, 09:50PM

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

- Measured, cut, superglued belt.
- Realized belt was tied in a knot, ripped apart, reglued.

- Attempted to tap output globes. $25,000 Shopbot? Check. $10,000 lasercutter? Check. 8 fancy dust collecting systems plumbed to every cutting tool? Check. 3 welders, mill, lathe, tooling? Check. $5000 in nut and bolt hardware? Check. $15 tap set? Not in the budget.

Oh, I feel your pain.

Hang on in there, you're doing a great job.

Ash Small

Tue Jun 03 2014, 10:12PM

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

AwesomeMatt wrote ...

Right now the end of the 1" copper pipe has a flat end, that's what I'm screwing into. Would it be better to have the ball meet the copper pipe flush, without the flat? I can hammer in a chunk of wood with a nut bashed into the far side, and just screw the ball directly until it's touching the pipe edge.

I'd probably drill and tap the hole in the centre, then solder on a short 'stub', or something, if I was pushed for time.

(Use the ball to hold the stub in place while you solder it)

Eleccentric

Wed Jun 04 2014, 01:59AM

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

Note the pulley ratio on the largest Wimshurt ever constructed:

You can also see that the neutralizer arms are much shorter than yours. They don't have to extend to the edges of the discs; they just have to touch the sectors. When it comes to carbon fiber brushes, if you can't find a junk printer to cannibalize, you can probably use carbon fiber tow. Google the phrase "carbon fiber tow" and you will find various cheap sources, including ebay, for soft carbon fiber cordage, string, rope, etc.

You are going to have a lot of problems with those tiny pulleys. I expect a lot of belt slip and wasted cranking effort, once the machine puts a mechanical load on the discs from coulomb forces.

Ash Small

Wed Jun 04 2014, 11:13AM

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

Eleccentric wrote ...

Note the pulley ratio on the largest Wimshurt ever constructed:

You are going to have a lot of problems with those tiny pulleys. I expect a lot of belt slip and wasted cranking effort, once the machine puts a mechanical load on the discs from coulomb forces.

I would have commented on this earlier, but I must have mis-read something about only needing the smaller pulleys to mount the larger ones.

AwesomeMatt

Wed Jun 04 2014, 07:56PM

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

wrote ...
I would have commented on this earlier, but I must have mis-read something about only needing the smaller pulleys to mount the larger ones.

Wrong set of pulleys. The lower drive assembly has these big black 12" (...) plastic pulleys that have no way of locking onto the shaft. So I used 6" pulleys that I bought earlier to just bolt right through into them and hold them to the shaft.

...

Took most of yesterday off.

Progress:

- Marked out disc. 47.75" * 3.1415 = 150.00" circumference. 50 sectors means 3" each exactly!

2036

(Anyone need some robotic pantyliners?)

- Oops. Not exactly. Shopbot was dead-on for disc size, but the very last mark revealed the width of the tape measure and other errors added up to 3/4" by the end (0.015" per sector). Measurement > Math. Thankfully didn't start adding sectors yet.
- Measured the circumference, made list of fractional measurements.
- Started converting decimal to nearest fractional inch.
- Metric > Imperial, stopped after about 5 stupid fractions and used mm instead. 3793mm, 75.86mm/sector. Printed out the table for reference.
- Marked out disc.
- Designed & cut sector layout template. A wedge shape I can guide the sectors to, depth and alignment-wise.

2037

(Pew pew!)

2038

(Left edge sits around shoulder disc, angled lines line me up, hole cutouts give me room to my fingers low and out of the way. Also visible is the old 2" template and the new thinner template)

- Tested soapy water method (gives time to adjust before stickiness grips). Doesn't work well with curled pieces. Better to just get it perfect and stay put.
- Started adding sectors, template works great, slow work, but compelted half a disc and they look perfect.

2039

Starting to look like a real Wimshurst!

Eleccentric

Wed Jun 04 2014, 10:29PM

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

Another thought on neutralizer brush material. You nay be able to use metalized mylar foil. This is used to make shiny decorative balloons as well as christmas tinsel. It is fairly conductive at these voltages, and having high resistance in series with the neutralizers really doesn't matter as the capacitance of the sectors is so small.

Another thing to consider would be solder wick - it is comprised of a bunch of extremely thin and soft bare copper wire.

Both of these suggestions lack the springiness of the carbon fiber tow or antistatic brushes. They might work in a pinch, however.

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