Building a SCR Clamp / Electromagnetic Projectile Accelerators / Forums

Forums

4hv.org :: Forums :: Electromagnetic Projectile Accelerators

« Previous topic | Next topic »

Building a SCR Clamp

1 2 next

Move Thread

LAN_403

aonomus

Mon Feb 16 2009, 08:01PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

So for my 3.8kJ capacitor bank I'm using puck SCRs, however after going through 2 iterations of clamps, I thought it would be helpful to get some second opinions.

My first iteration was mostly full of crap, 3/8" thick aluminum plates with screws that bent the plates under slight tension. Not even worth mentioning or showing pics.

My second iteration is below, 3/4" wide, 1/8" steel flats, and wide aluminum flats as conductors, this one seems to have much more promise, but its still not enough. The datasheet lists the clamping force as 2000lb or 8.9kN, and under a moderate amount of pressures the bars bend, as shown below. Also, I've added a single washer in the middle of each aluminum flat to concentrate the force in the middle of the plate to get maximum contact. Another problem is that the bolts are 1/4", and probably would not stand to a shared load of 2000lb tensile.

Unfortunately I don't think that there is sufficient pressure, so my third iteration on paper is currently using 1" wide steel, likely 4 plates per side, thicker bolts like 3/8" or 1/2", and a center bolt with belleville washers to calibrate the pressure to 2000lb (similar to

). This final iteration will end up costing me probably 4x as much, but the SCRs should last well I think....

What are other people's experiences when building their own SCR clamp? Does anyone with more experience in steel think I need to add more steel to the clamp?

Myke

Mon Feb 16 2009, 08:16PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Even though I haven't built and SCR clamp before, I would say that you should add more steel to both sides and move the bolts closer together. The farther away they are from the SCR, the easier it is to bend the steel.

badastronaut

Tue Feb 17 2009, 12:59AM

Registered Member #222 Joined: Mon Feb 20 2006, 05:49PM
Location:
Posts: 96

Use thicker steel, at least 3/8" and use belville washers, they will help. You'll also want to use insulating plates between the metals so you don't short everything out. To compress the washer, I would suggest using a hydraulic press to precompress the washers. Well, you only really need one washer. If not, you can use several bolts around the periphery of the scr and tighten them incrementally all around and evenly to reduce point stress.

aonomus

Tue Feb 17 2009, 01:19AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I just put a quote request in to metal supermarkets for 4 pieces of 1 1/4" square aluminum, 10cm long. Those should be sufficient no? Kizmo's SCR clamp used 30mm square aluminum, and his held up a treat.

Moving to thicker and thicker metal I'd really like to use aluminum, I don't have cobalt steel drill bits and I will just wear mine out drilling through so much steel, my only real choice is a big thick piece of aluminum which is actually reasonable to machine.

rp181

Tue Feb 17 2009, 02:30AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Aluminum will work. Keep the bolts as close as you can to the SCR.

El_Roberto

Wed Feb 18 2009, 07:31AM

Registered Member #1774 Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135

You Could use 2 bolts on each side of the SCR to make them easier to tighten, just tighten one then the one next to it and then tighten the first one again (and repeat till super tight), I dont know how well this works but someone told me it makes it easier.

Andyman

Thu Feb 19 2009, 12:01AM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

As long as you don't drill with high rpm, you shouldn't have a big problem with worn out bits.

aonomus

Thu Feb 19 2009, 12:29AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Lowest setting on the drill press with cutting fluid and a decent rate of chip removal seems to be doing it, I just need to get more cutting fluid cause steel chews through it...

Regardless I think I might go with aluminum just to avoid corrosion issues.

Firefox

Thu Feb 19 2009, 05:43PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

Looking at your SCR clamps, they seem grossly undersized. I have two SCRs (had three, but one went in the junkbox, which gets mailed out tomorrow), C387Ns with clamps, and the clamps seem to be 1" square steel bars with half inch bolts to clamp them together. The terminals were insulated from the clamp by a plastic shield over half the clamp.

Andyman

Thu Feb 19 2009, 06:02PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Yeah, I know what you mean. Just get some nice thick 7075 aluminum bar.

It's probably out of your price range, so just go with some 6061 or 6063.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob