Forums

Portable Electronic Glass Stength Tester

Started by Unknown June 26, 2013
On Wednesday, June 26, 2013 11:52:31 PM UTC-4, Jeff Liebermann wrote:
> On Thu, 27 Jun 2013 11:10:33 +1000, mharris@comprodex.com wrote: > > > > >It is intended to test the breaking strength of glass sheet on solar > > >panels in the field. Hence, it needs to be portable, running off > > >something like two 3.7V Li-ion batteries. > > > > > >The concept is to use a solenoid-type plunger that is activated one > > >time by a push button. This strikes the glass with a predetermined > > >breaking strength to check for durability against hail damage, etc. > > > > Find a low friction ramp, and a method of supporting it perpendicular > > to the panel. Roll a large steel bearing down the ramp. The energy > > transferred will be controlled by the distance the ball is started up > > the ramp, and the angle of the ramp. Some math will be required. This > > is similar to the Charpy and Izod impact tests. No electronics > > required. > > > > Sounds like a job for an air canon. Mythbusters did something like > > that when testing the resistance of a Cessna 150 wind screen to > > impacts by frozen chickens. A scaled down version should work. > > Presumably, the hail stones will hit terminal velocity (about 200 mph) > > depending on its wind resistance, which will probably destroy any > > solar panel. Safety might be a problem. > > > > However, if you're "only" interested in launching hail stones at the > > solar panel: > > <http://www.renewableenergyworld.com/rea/blog/post/2010/08/the-strength-and-durability-of-solar-panels> > > "This type of glass is designed to withstand a direct vertical > > impact of hail up to 1 inch in diameter, traveling at 50 miles > > per hour." > > > > With the 1" hailstone and 50 mph. > > volume = 4/3 * Pi * r^2 > > = 1.33 * 3.14 * 0.5^2 = 1.04 in^3 > > which has a mass of: > > 1.04 * 0.036127 lbs/in^3 = 0.038 lbs = 0.0172 kg > > 50 mph = 22.4 meters/sec > > At 50 mph, the energy delivered is: > > Energy = 0.5 * mass * velocity^2 > > = 0.5 * 0.0172 * 22.4^2 > > = 4.3 joules > > That can be done with a solenoid gun or an air or spring power > > launcher.
For only 50 mph (~22m/s) he could just drop ice cubes from a ~25m building. (v^2 = 2gh). I guess that's not very portable :^) George H.
> > > > > > -- > > Jeff Liebermann jeffl@cruzio.com > > 150 Felker St #D http://www.LearnByDestroying.com > > Santa Cruz CA 95060 http://802.11junk.com > > Skype: JeffLiebermann AE6KS 831-336-2558
Thanks for sall the mechanical suggestions. We ruled these out due to
inherent variables and aging of parts.

Can anyone tell me how to build a solenoid operated plunger that will
have the necessary force? Or at least a viable starting point with
regard to circuit design.

Mark "Hailstorm" Harris
On Thu, 27 Jun 2013 11:10:33 +1000, mharris@comprodex.com wrote:

>The concept is to use a solenoid-type plunger that is activated one >time by a push button. This strikes the glass with a predetermined >breaking strength to check for durability against hail damage, etc.
You may get some ideas from these articles: IEC 61215 (crystaline panels) 10.17 is the hail impact test. IEC 61646 (thin film panels) IEC 62108 (CPV Modules) "Simulated Hail Damage and Impact Resistance Test Procedures For Roof Coverings and Membranes" <http://www.jdkoontz.com/articles/simulated.pdf> "Construction of a Hail Gun for Solar PV Module Testing" <http://www1.eere.energy.gov/solar/pdfs/pvmrw12_poster_si_uselton.pdf> JPL at its best. PVC air cannon firing 1" ice balls. "Effect of Hail Impact on Thermally Tempered Glass Substrates Used for Processing CdTe PV Modules" <http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/TESTEVAL/PAGES/JTE101036.htm> I really like this video, which uses frozen paint ball pellets to compare impact strength of tempered glass and acrylic skylights: <www.youtube.com/watch?v=xf9A5nk-KF0> "Photovoltaic Solar Panel Resistance to Simulated Hail. Low-Cost Solar Array Project." <http://www.ntis.gov/search/product.aspx?abbr=DOEJPL1012782> -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote:

>Thanks for sall the mechanical suggestions. We ruled these out due to >inherent variables and aging of parts.
No fun. I was hoping for an ice ball cannon. From IEC 61215 10.17 1st edition(1993) - Test apparatus as described in section 10.17 with a velocity repeatability of +/- 5%. - Instrument for velocity measurement with an accuracy of +/- 2%, no more than 1 m from module impact surface - Weighing instrument with an accuracy of +/- 2% - Freezer and container for production and storage of ice balls - Apparatus to verify ice ball diameter to within +/- 5% of requirement and mass within +/- 5% of requirement. This looks more like a piece of laboratory equipment, instead of a field tester. Which are you designing?
>Can anyone tell me how to build a solenoid operated plunger that will >have the necessary force? Or at least a viable starting point with >regard to circuit design.
No, but I have a suggestion. The mass of the impactor isn't going to change between shots. The velocity will. So, the problem is how to get a controlled and accurate velocity. Measure the velocity of the ice ball with two photocells. Setup a non-destructive target, like a block of wood. Fire the ice ball and measure the velocity. Adjust the launcher pressure, position, tension, whatever to obtain the desired velocity. Once the velocity is set, subsequent shots should retain the same impact energy as the test shot, within variations of ice ball shape, mass, surface smoothness, etc. For building the electronics, it's just a period counter, with start and stop inputs. The ice ball breaks a light beam to start the counter and breaks a 2nd beam to stop the counter. The speed is the distance traveled divided by the time it took to travel the distance. If you want to get fancy and expensive, I guess you could provide feedback to propulsion device. For example, an air cannon could have its pressure controlled by the velocity calculation. After firing a few shots in rapid succession[1], the ice ball velocity should converge on the target value. I see a major problem in casting or delivering ice balls to the test site. A portable freezer might work, but does tend to be rather clumsy. It might be possible to use plastic or porous clay balls in place of ice. The specific gravity should be about the same, and with sufficient porosity, simulate the brisance of ice shattering on impact. However, this may be breaking new glass, errr... ground, as all I could find under simulated hailstones were those made from ice. Various commercial ice ball makers: <http://cocktailsandcologne.wordpress.com/2012/02/24/the-macallan-ice-ball-machine-and-other-ice-sphere-tools/> Lots of good ideas here: <http://www1.eere.energy.gov/solar/pdfs/pvmrw12_poster_si_uselton.pdf>
>Mark "Hailstorm" Harris
Beware of those that take "hail to the chief" quite literally. [1] Check with the DHS if a full auto ice ball cannon is legal. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote:

> >Thanks for sall the mechanical suggestions. We ruled these out due to >inherent variables and aging of parts. > >Can anyone tell me how to build a solenoid operated plunger that will >have the necessary force? Or at least a viable starting point with >regard to circuit design. > >Mark "Hailstorm" Harris
They're all mechanical to some degree. It remains to be seen whether the friction and other temperature etc. related variations in a solenoid plunger would be any better than an electronically calibrated spring force. Regardless of how you drive them, solenoids provide a very nonlinear force with plunger position.. so they're actually not very well suited to your application. The more efficent ones (with a closed magnetic circuit when they're actuated) are much worse. Some of the temperature related variation could be eliminated with a constant current type drive, but I doubt that's your biggest problem with that approach. Maybe you could fling a mass around with a motor. Or pump up a relatively large reservoir with air to a calibrated pressure and use an air cylinder. Or if cost is not a concern and you're stuck on the solenoid-ish idea, consider a linear motor*. BTW, (baseball) pitching machines use two methods that I've seen- the portable ones use a rotating urethane wheel set to a calibrated RPM. The "Iron Mike" style uses a spring that is deflected by a motor-driven cam which releases under set tension to pitch the ball at up to ~90mph. * eg. from the makers of the Retro Encabulator:- http://www.rockwellautomation.com/anorad/downloads/pdf/LEULinearMotor10-06.pdf Uses semi-boloid slots?
On 27/06/2013 17:18, Spehro Pefhany wrote:
> On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote: > >> >> Thanks for sall the mechanical suggestions. We ruled these out due to >> inherent variables and aging of parts. >> >> Can anyone tell me how to build a solenoid operated plunger that will >> have the necessary force? Or at least a viable starting point with >> regard to circuit design. >> >> Mark "Hailstorm" Harris > > > They're all mechanical to some degree. > > It remains to be seen whether the friction and other temperature etc. > related variations in a solenoid plunger would be any better than an > electronically calibrated spring force. > > Regardless of how you drive them, solenoids provide a very nonlinear > force with plunger position.. so they're actually not very well suited > to your application. The more efficent ones (with a closed magnetic > circuit when they're actuated) are much worse. Some of the temperature > related variation could be eliminated with a constant current type > drive, but I doubt that's your biggest problem with that approach. > > Maybe you could fling a mass around with a motor. Or pump up a > relatively large reservoir with air to a calibrated pressure and use > an air cylinder. Or if cost is not a concern and you're stuck on the > solenoid-ish idea, consider a linear motor*.
<snip> A 'voice coil actuator' would be better than a solenoid. I know little of these but Google has lotsa hits... http://www.orlin.co.uk/voice-coil.htm is one such. Cheers -- Syd
On Thursday, June 27, 2013 12:18:41 PM UTC-4, Spehro Pefhany wrote:
> On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote: >=20 > >Thanks for sall the mechanical suggestions. We ruled these out due to >=20 > >inherent variables and aging of parts. >=20 > >=20 > >Can anyone tell me how to build a solenoid operated plunger that will >=20 > >have the necessary force? Or at least a viable starting point with >=20 > >regard to circuit design. >=20 > > >=20 > >Mark "Hailstorm" Harris >=20 >=20 > They're all mechanical to some degree.=20 >=20 > It remains to be seen whether the friction and other temperature etc. > related variations in a solenoid plunger would be any better than an > electronically calibrated spring force.=20
I think I'd try some spring loaded gizmo first. =20 I was thinking about the ice cube on the end of a string idea, but unless y= ou've got a long string it's hard to see how you'd get the panel inserted..= . You could release the string at some point, but that strikes me as scarie= r than the ice-ball air cannon. =20 I've got it, set the panel on the side of the road, get your car up to 50 m= ph with the ice ball held out the window. Trigger some release mechanism a= t the right point so the ice-ball drops and impacts the panel. Slightly = more portable than than dropping ice cubes from buildings. :^) George H.
>=20 >=20 >=20 > Regardless of how you drive them, solenoids provide a very nonlinear >=20 > force with plunger position.. so they're actually not very well suited >=20 > to your application. The more efficent ones (with a closed magnetic >=20 > circuit when they're actuated) are much worse. Some of the temperature >=20 > related variation could be eliminated with a constant current type >=20 > drive, but I doubt that's your biggest problem with that approach.=20 >=20 >=20 >=20 > Maybe you could fling a mass around with a motor. Or pump up a >=20 > relatively large reservoir with air to a calibrated pressure and use >=20 > an air cylinder. Or if cost is not a concern and you're stuck on the >=20 > solenoid-ish idea, consider a linear motor*.=20 >=20 >=20 >=20 > BTW, (baseball) pitching machines use two methods that I've seen- the >=20 > portable ones use a rotating urethane wheel set to a calibrated RPM.=20 >=20 > The "Iron Mike" style uses a spring that is deflected by a >=20 > motor-driven cam which releases under set tension to pitch the ball at >=20 > up to ~90mph.=20 >=20 >=20 >=20 > * eg. from the makers of the Retro Encabulator:- >=20 > http://www.rockwellautomation.com/anorad/downloads/pdf/LEULinearMotor10-0=
6.pdf
>=20 > Uses semi-boloid slots?
On Thu, 27 Jun 2013 10:17:59 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>I think I'd try some spring loaded gizmo first.
The OP mentioned something about an accuracy problem. Citing my last rant: From IEC 61215 10.17 1st edition(1993) - Test apparatus as described in section 10.17 with a velocity repeatability of +/- 5%. - Instrument for velocity measurement with an accuracy of +/- 2%, no more than 1 m from module impact surface - Weighing instrument with an accuracy of +/- 2% - Freezer and container for production and storage of ice balls - Apparatus to verify ice ball diameter to within +/- 5% of requirement and mass within +/- 5% of requirement.
>I was thinking about the ice cube on the end of a string idea, but >unless you've got a long string it's hard to see how you'd get >the panel inserted... You could release the string at some point, >but that strikes me as scarier than the ice-ball air cannon.
Yeah, but I like your idea. However, not one string but two as in a traditional sling: <http://en.wikipedia.org/wiki/Sling_(weapon)> <http://www.slinging.org> It worked on Goliath, so a mere tempered glass window should not be a major challenge. I prefer 2 or 3 overhead spins because I can use a longer length rope, and it helps seat the projectile in the pouch, but vertical spins with shorter ropes should also work. To indicate the desired velocity, a teapot whistle, or electronic equivalent, is attached to the end, which signals the when to let go. Some practice and calibration will be required. In the event of collateral damage, a good insurance policy might also be useful. I suppose all this could be automated, in the Mythbuster style, that takes the fun out destructive testing. If accuracy is a problem, then several small hailstones could be simultaneously launched. At least one might hit the target panel.
>I've got it, set the panel on the side of the road, get your car >up to 50 mph with the ice ball held out the window. Trigger some >release mechanism at the right point so the ice-ball drops and >impacts the panel. Slightly more portable than than dropping >ice cubes from buildings. :^)
Ummm... the panels are usually mounted on a rooftop. Unless there's an adjacent building, that is 25 meter higher, the drop test method isn't going to work. However, you gave me yet another marginal idea. At 50 mph (22.4 meters/sec), liquid water and ice will transfer about the same amount of energy to the glass. No need to use a frozen ice ball proxy, when a small water balloon filled with non-frozen water will suffice. This was demonstrated by Mythbusters in the chicken cannon, and by me in college when I used a sling to launch water balloons. This was deemed a major escalation in inter-dormitory warfare and was immediately suppressed by the administration after I sent a fairly small water balloon through a non-tempered window (at about 30 meters range). -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Friday, 28 June 2013 02:18:41 UTC+10, Spehro Pefhany  wrote:
> On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote:=20 > >=20 > > Thanks for all the mechanical suggestions. We ruled these out due to=20 > > inherent variables and aging of parts.=20 > > =20 > >Can anyone tell me how to build a solenoid operated plunger that will=20 > >have the necessary force? Or at least a viable starting point with > >regard to circuit design. >=20 > Regardless of how you drive them, solenoids provide a very nonlinear > force with plunger position.. so they're actually not very well suited=20 > to your application. The more efficent ones (with a closed magnetic=20 > circuit when they're actuated) are much worse. Some of the temperature=20 > related variation could be eliminated with a constant current type=20 > drive, but I doubt that's your biggest problem with that approach. =20 >=20 > Maybe you could fling a mass around with a motor. Or pump up a=20 > relatively large reservoir with air to a calibrated pressure and use=20 > an air cylinder. Or if cost is not a concern and you're stuck on the=20 > solenoid-ish idea, consider a linear motor*.=20
=20 <snip> =20
> * eg. from the makers of the Retro Encabulator:-=20 > http://www.rockwellautomation.com/anorad/downloads >/pdf/LEULinearMotor10-06.pdf=20 > Uses semi-boloid slots?
That has a moving coil. Inland Motor (now part of Danaher Motion) used to m= ake a linear motor in which the moving part was a steel rod into which had = been cut a helical groove. The groove was then back-filled with non-magnetic chrome, You did have to p= revent the rod from rotating, but the groove was enough for a Sawyer type l= inear synchronous motor to grab onto. The flat linear motor in your URL could be topologically transformed into s= omething similar by stacking Neodynium-Iron disk magnets (of alternating po= larity) into a rod, but keeping them stacked would be tricky, and grinding = them into a uniform circular rod would be worse. Soft iron aka steel isn't a nice material for fast-stepping synchronous mot= ors - the rapidly changing magnetic fields turn into current circulating wi= thin the metal, which doesn't do anything except warm the rod. --=20 Bill Sloman, Sydney
George Herold wrote:
> > For only 50 mph (~22m/s) he could just drop ice cubes from a ~25m > building. (v^2 = 2gh). > > I guess that's not very portable :^)
The ice, or the building? ;-)