If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Hey all, just want to assure I do everything right with my first SCR pucks.
I have the C398 model, and the datasheet says MAX force 2000 pounds. No min. force is listed. So, Not sure how much force I should apply to this. The other issue, I have a torque wrench, 0-140 foot pounds. Is there any way to know a SAFE foot-pounds torque, without passing the 2000 pounds of force limit? My hardware store only sells 100 pound spring washers, So the only other thing that I can do, is fine some place online that sells around 1500 pound spring washers...
Also, I'm hoping this 1/4" steal beam is thick enough. It came from a 2x2" steal L beam...Was fun cutting it, hard stuff!
Any feedback will help, Thanks all!
Also...What might be a safe ft/pound to test a SCR at maybe 30V or so?
edit My SCR that isnt pressed has 1mm of metal showing above the ceramic material. My one in the press, isnt shown. I tighten it down by guessing, and I didnt even hit a foot pound of torque, and my 1/4" thick iron beam metal, is already bending in a ( shape...so far, i did a 70V test, and it worked. But just because it works, doesn't mean it will at 450...
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Here are a few hints. Many kinds of spring washers, such as Bellville washers and wave washers, can be stacked in such a way that each one gets the full deflection, so the forces add. With a bolt on each side of SCR, and three 100-lb spring washers on each bolt, you are up to 600 lbs.
As for the torque to get a given bolt tension, it's easy to find tables and formulas on the Internet. All approximate, because of variables such as friction between the mating threads. But as you know, most bolting instructions specify torque when what matters to the engineer is tension. Find a smaller torque wrench. 1/4-20 bolts and torques less than 5 ft-lb can overstress your SCR.
If your steel beam is measurably bending into a ( shape, it can serve as a pretty accurate gauge of clamping force -- much better than the torque wrench. With a dimensioned drawing or picture, you (or anyone who has studied "strength of materials") can calcuate the amount of elastic bending when there is (say) 1500 lbs of force on the SCR puck.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Ah...Well, Here is a picture of the SCR. Right now it has 1/4" Iron I beleive. My dad picked it up at work for welding practice. So I cant fully say what it is. I will try to hit the hardware store tomorrow, and see if they have any types of washers that are rated in pounds...So far, the torque meter gets to about 8. on each. I may consider though getting a new wrench before I redo this too...Because its my dads old one, and it still 'frictions' on the scale a little, so im questioning if that is going to effect it a lot.
I will try to get in tomorrow and see what they have. If the max is 2000, do I want to aim for 1000? 1500?
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Wow! If those flat steel bars are 1/4 inch thick and 2 inches wide, either you are way over 2000 lbs, or the bars have yielded and are permanently bent.
My unreviewed calculation says that with a 2000 lb load midway between two bolts 4" apart (at 1000 lbs each), the elastic deflection would be only 0.035" and peak stress 96000 psi. That's too much for mild steel, especially hot-rolled stock, which would probably yield at a lower stress. If the bolts were only 3" apart then deflection would be .015" and stress 72000 psi.
p.s. the deflection values are for just the section between the bolts. Anyone else care to review these numbers?
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Well, I put the spacing where the SCR plastic things were. Clearly, if it was 2000 pounds, it would prob break because the max force, is 2000 pounds. I also have 1/4" acrylic isolating the clamp and the pic, with a washer to focus the force to the center. That hasnt snapped, and I dont think acrylic could handle over 2000 pounds of force, on top of a small washer.
Measurements!
bars are 1.5" deep. and 5" wide. 1/4" thick. the 2 bolts, from the CENTER, are exactly 2 6/8" apart.
When putting a flat piece of wood along the steel, the 'bow' is about 1mm higher than the ends.
Again, unless my torque wrench is THAT bad, i didnt even get past 5-6 foot pounds of force.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Killa-X wrote ...
Well, I put the spacing where the SCR plastic things were. Clearly, if it was 2000 pounds, it would prob break because the max force, is 2000 pounds. I also have 1/4" acrylic isolating the clamp and the pic, with a washer to focus the force to the center. That hasnt snapped, and I dont think acrylic could handle over 2000 pounds of force, on top of a small washer.
Measurements!
bars are 1.5" deep. and 5" wide. 1/4" thick. the 2 bolts, from the CENTER, are exactly 2 6/8" apart.
When putting a flat piece of wood along the steel, the 'bow' is about 1mm higher than the ends.
Again, unless my torque wrench is THAT bad, i didnt even get past 5-6 foot pounds of force.
My thought, was I need a thicker bar.
Thanks for the numbers. Unfortunately I'm just about out of time.
The datasheet says "max clamping force 2000 lbs". That's the maximum design load in the SCR application. Like saying a 1/2 ton pickup truck is rated to carry 1000 lbs -- we would not expect it to break at twice that load, but can't depend on the maker's warranty if it -does- break.
I bet your steel beams have yielded -- taken a permanent set -- so we can't use their elastic deflection to gauge the load. If the SCR and stuff stacked with it were incompressible, you would hit 2000 lbs with less than 1/2 turn of each nut. If the nut keeps turning without a proportional increase in torque, something is yielding.
The compressive strength of acrylic (PMMA) is given by a couple references as 10,000 to 18,000 psi.
I think your thicker bar idea is good. How 'bout some 1" square tubing? Could safely give you 2000 lbs of compression with up to 7" between the bolts, [edit] Read about spring washers at McMaster. Part 9712K71 is 12 for about $4. WIth two on each bolt, the load when flat would be 1600 lbs.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Well I know a puck that is NOT pressed has 1mm of metal showing between the plate and the white ceramic. In my clamp, it has been pushed down to the ceramic, which we want. As to how hard, I can't say.
So my best bet may be to undo it all, get some 100+ rated washers, new steel, and aim for a number? I got more steel I can sawsall cut to have fresh unbent metal... My datasheet doesn't say a minimum force, so I have no idea what to aim for.
Seeing we don't know if it's overpressured, and that I did 70v tests, is it possible the scr could suffer damages? And should I only get washers for the bolts, or should I try to get some on the puck to go by center force?
Thanks for the help so far!
edit Thanks for the help too, My hardware store did not have ANY at all! Have to go online.
So basically just screw down until they are completely flat. Sounds good :)
Yeah...I'm going to need to cut new pieces. Or in fact, Since this bent, I should probably get thicker metal...Right? The torque wrench was under 5 foot pounds, so there's no way it was even close...
If not... would 1" thick steel work? I'm not too knowlageful on metals and strengths. I know a 1" bar of aluminum would be cheaper, but is 1" x 1" of 6061 strong enough to apply that much force? or will it bend?
Ebay has a 1" x 1" x 12" 6061 aluminum for $8 after shipping. Ebay also has a 1" x 1" x 24" Steel ALLOY 12-L-14 for $15 after shipping...
Guess I answer my own question...Given your calculator is right with 6061, it says 1" x 1" would bend 0.0365 with aluminum.
Wiki says, "6061-T6511" is rated tensile strength of 42,000 psi, yield strength of 35,000 psi
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
SCR clamping - Torque
