Best way to drill through cast iron???

I have no idea how to calculate that, so we'll just skip it. It's more than plenty enough to throw a baseball. I hate sewing, and I made a sling that can't fit anything larger than a baseball, so a baseball it is.

I wonder how you'd factor in the roller bearings when calculating arm inertia. I gather these things aren't usually built that way. The arm is ~2" wide along the pivot axis, but the contact patch is much narrower, since the only bearing surfaces are a couple of 1/4" thick roller bearings. Very low resistance; very smooooth. If I put a fixed weight on the bottom and give it a good shove, it will rock back and forth for 20 minutes.

I got to about 70' with half a brick. But your machine is much larger than mine. From ground to the top of the hook is 60".

Anyway, there are lots of trebuchets out there in the world that are bigger/stronger/faster/cooler than mine, but there's only one like this one, and I designed and built the thing myself, and it kicks ass, no matter what anybody else says. :)

Reply to
Silvan
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Download the programs WinTreb or TrebStar

My one started with an axle of 3/4" tube, then bent that during testing. Nw it runs with solid 3/4" steel. Don't underestimate the forces around that pivot ! (like they did on Scrapheap Challenge)

Absolutely !

BTW, the last couple I made were mangonels, not trebs (twisted rope, not a weight) One had a 9" arm, for my 8 year old, and the other had a 12" arm for a friend's birthday.

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Reply to
Andy Dingley

Constrain the payload to approximate size and mass of a USDA grade A extra large hen's egg: good aerodynamics, harmless, but still lots of fun. What range could you achieve with a modest treb?

Reply to
Dr. Rev. Chuck, M.D. P.A.

And run them on what?

I haven't found any trebuchet software for Linux. Actually, I just looked again, and there _is_ something, but SourceForge is being uncooperative at the moment.

Mine is only 5/8" but it's serious stuff. I couldn't drill a hole in it. When I tried to mark the starter dimple with my center punch, I ruined my center punch. I never could get a bit into it.

the line somewhere, and that's it. Using archaic technology is fun, but for the scale of machine I have to build, I'd be surprised if a torsion bundle is worth the effort compared to bungee power.

Reply to
Silvan

Hmmm... Now why didn't I think of that? We don't eat a lot of eggs, and I'll bet there are still eggs in the fridge left over from last winter's cookie baking season. Maybe I'll decorate the gigantic concrete wall beside my house. :)

Reply to
Silvan

Hmmm. Flashback from working on heavy equipment! I used to hate drilling holes in thick cast iron - a realitively thin table saw should be a cakewalk. We used a 2 HP drill - if the bit bit - you went for a ride! My Delta TS has 3 holes drilled on each side for this purpose. You will need Cobalt Drill Bits. The bigger the drill the better. Start out with a small bit and work your way up to whatever size you need. I assume you'll wind up using 3/8" bolts (?). Optionally you can tap the holes to receive the bolt. Mark from Pasadena, MD

tnfkajs wrote:

Reply to
Mark

I too have the Jet SuperSaw and I have added an outfeed table to the back (32"x57" I think), an extention table to the right hand side, a drawer under the extension table (for push sticks and feater boards) and a large drawer under the saw cabnet for blades and such.

Drilling through the cast iron was easy (1/4" holes). I used a BD elec drill, 1/4" 'Bad Dog' bit and a little 3-in-1 oil. Worked like a champ.

If you want more info or some pictures, email me.

Cheers, john

tnfkajs wrote:

Reply to
John Mohn

Wine ?

A torsion bundle works better when scaled down than either a weight machine (especially) or a bungee.

Nylon bricklayer's line is the best I've found. Horsehair is more in period.

Reply to
Andy Dingley

Reply to
"Bo" Mathews

If there is a flat surface, you can atach a magnetic drill. Good tool rental shops have them, but it will probably be $50 for the day. You supply the bit. Yes, lube as you drill, even if it is only a spray of WD-40.

Anything you can clamp on to? Ed

Reply to
Edwin Pawlowski

How do you get a couple of turns? I've never been able to get more than a half turn or so before things tighten up enough that I'm afraid of breaking the tap.

There must be some sort of corrolary to Murphy's Law about this; taps only break in locations whose position is absolutely essential and for which no alternative exists. I don't want to fall prey to that...ever.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

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Reply to
LRod

If he's going to tap the holes, it's also worth conidering using a drill jig to assure the hole is perpendicular to the surface. A block of hardwood 1.5 inches or so thick with a drill press drilled hole in it makes a good drill jig for quite a few holes before it wears out. Just clamp the jig in place and use it to align the drill. Not necessary, but it makes for a nicer job.

Reply to
D.B.

Back up as it starts to get tight, don't wait until it's tight.

Are you using the right size tap drill for the material?

Don't have good tap drill chart?

Subtract one thread pitch from the nominal screw diameter. .250-20 Tap drill = .250 -1/20 = .200. Then pick the next largest actual drill size (assuming you have a complete set of drills). If you only have a set graduated in 1/16th or

32nds you have a problem.

Also use coarse threads everyplace you can. They are easier to cut and hold up better in many materials, cast iron and aluminum being two good examples.

Rico

LRod wrote:

Reply to
D.B.

I'm the OP - I asked this about a month or two ago... I asked because I didn't have the slighest idea on what it took to drill into cast iron. Now I do... :)

Reply to
tnfkajs

I do that. It just doesn't take very long; certainly not two turns.

Yes.

I do.

If I can remember all that, I'll try to use it if my chart isn't handy.

I have fractional and numbered, but I don't have letter size. Most of the time I'm tapping sizes that need number sized bits. No problem there.

Probably stainless, too, I would think, because of the ease of galling.

Thanks for your thoughts.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

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Reply to
LRod

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