[oracle99]

I hope this make sense. I do not have a cad program. I was thinking about making a manual 3d object copier. It would use 2 swing arm desk lamps as the base. The arms would be attached together by rod end bearing for free movments. At the end of one arm would there would be a tracer tip. Ths tip would touch the object. The other arm would hold a dremel tool for carveing the part out of sometype of light stock material.
I hope this makes sense.
Conan

[DrewSmith007]

I've had the exact same idea in the past. It's kinda like a 3d key copier. If you do it right you should be able to either make a positive copy or a negative mold. You could also scale it up or down, i would think. Have you worked on this idea at all?

[DrewSmith007]

not exactly the same thing, but similar.

http://www.cnczone.com/gallery/showphoto.php/photo/2895

[greybeard]

If you ever get to the British Museum, you will find an almost identical device in the reconstrution of James Watt's workshop(if it is still there !!).
He invented/designed the same mechanism for copying busts in stone, and his cutting tools were drills. Late 18th century. He braced his with a "pyramid" space frame on both the pivoting frames.
The copying process was a case of continually drilling into a block of stone from all directions, and reducing the diameter of the drill as he got closer to the finished detail.

Anything new under the sun ???

Regards
John

[DrewSmith007]

Not really, I've started spring semester, and I havn't really had time (or money) to do anything. I've got an ongoing project where I'm making a concrete curb extrusion machine so I can start landscape curbing this summer. I've actually incorporated some of the cnc stuff into it, but nothing with computers. I was having trouble with the slide mechanism binding up, but I think I've solved that with the angle iron and skate bearing linear rails. I'll post some pics when i have them. In the mean time, check out www.kwikkerb.com or www.borderlinestamp.com for an idea of what i'm talking about.

[drcrash]

Try doing web searches for "3D pantograph," "Collas Machine," and "Cheverton Machine."

A pantograph is a system of four levers that keeps three points in a line, and in the same ratio of distances from each other. Most pantographs are 2D, but they work in 3D if you have rigid levers, and pivots that keep them in a plane. Given a pantograph like that, you can put it on a universal joint and use it to scale 3D shapes up or down, or scale and invert them (from positive to negative. It all depends on which of the 3 points you use to attach the universal joint (at a fixed point) and which you use for the probe or the cutter.

The Sears Craftsman Deluxe Router pantograph is a limited 3D pantograph. In normal use, it's only good for relief carvings up to about an inch deep, and only lets you reduce things (to 40, 50, or 60 percent) but you can do some perverted things with it. (If you extend the u-joint mount, probe, and cutter a few inches out of the plane of the pantograph, and mount a lightweight low-kickback cutter on it, you can do a fair bit of stuff.)

A Collas machine is a different thing that uses a simple lever on a universal joint (I think), and a pair of synchronized turntables. (Using gears or sprockets and a chain or whatever.) You can move a probe attached at one point on a lever, moving it in and out or up and down to scan over a model, and a cutter at another point which will move proportionally. By itself, that would only give you an arc, but if you rotate the model and the copy (blank) you can do full 3D shapes in the round.

Most of Rodin's sculptures were scaled up/and or down from macquettes (terra cotta, I think) using a Collas machine.

A Cheverton machine is sorta like a Collas Machine, only instead of using a simple lever, you use a pantograph in combination with synchronized turntables. That lets you do not only full 3D in the round, but some fairly serious undercuts, because you can come at the work from different directions with the probe and cutter.

Cheverton machines were used to produce lots of sculptures in the 19th century.

Paul

[greybeard]

For any one interested in my earlier mention of Watt's invention of a copying machine, Google for "James Watt workshop picture", there's a picture in the first link at the "Ingenious" site.

The photo has the caption "......and the workshop from J. M. Gibson Watt in 1924 - it has not been disturbed since Watt's death in 1819 and includes some of his three dimensional copying machines."

If memory serves, both the original and the block of stone were mounted on turntable that were not only linked to rotate together, but they could also be tilted, and still stay in sync with the probe and drill holder !

Regards
John