Pantograph??

[CPDDET]

Wondering if anyone is using a pantograph to copy sections of build plans?

 

Some items on my build plans are shown at twice scale size. Thought it might work using a pantograph to trace at scale size, cut out the item and then glue / past scale size drawing to whatever medium being used (wood, plastic, metal) before fashioning the item.

[druxey]

A pantograph is a rather difficult tool to use in practice. You need to have an extremely steady hand on the tracing point, sufficient weight on the pencil point for it to mark properly and a solid mounting on your drafting table. It was useful, I suppose, in the days before scanners and digital enlargement, but I'd scan and (in your case) reduce and print out what you need. 

[Roger Pellett]

For me, a timely thread.  I have a pantograph that was bought at a flea market many years ago.  I tried to use it to copy a plan and the results were, to say the least poor.  I consigned it to my scrap box.

 

I recently decided that I would like to have a beam compass for a project that I have been considering.  After being outbid for one on Ebay, I decided to make one.  While rummaging in my scrap box I found the pantograph.  I cannibalized it to build my beam compass.

 

I agree with Druxey, the pantograph would seem to be outdated technology.  Most modelers can change the scale of drawings digitally, and old fossils like me can redraft.  Since your drawings are twice your intended scale, an architectural copying service can make accurate prints.  For my last model, I drew the plans at twice scale.  I then had the drawings copied at half size, the idea being that any drafting inaccuracies would be halved.  I was happy with the results. 

 

Roger

[Bob Cleek]

Most pantographs available today are really little more than toys. The really good ones used back when are very complex pieces of precision equipment and rather heavy. If you can find a complete one, it will likely be quite expensive if the seller knows the collector's market.

 

In practice, the pros used the pantograph to simply mark points from the original to the copy and then "connected the dots." That's much easier than trying to trace lines with the instrument. Using this method, acceptable results can be realized, even with the cheap ones. In most instances, however, scaling is today far easier with a copy machine.

 

If you find one like this at a garage sale, grab it!

 

 

 

https://americanhistory.si.edu/collections/search/object/nmah_904629

[druxey]

I've never seen a pantograph as sophisticated as the one above. A beautiful bit of kit.

[Bob Cleek]

1 hour ago, druxey said:

I've never seen a pantograph as sophisticated as the one above. A beautiful bit of kit.

They got even more complex than that one. It's a Keuffel and Esser, circa 1920. The little cup on the post at the pencil joint is for putting coins or lead weights in to adjust the pressure of the pencil on the paper. I though that was very cool. With the right weight applied, there's no need to hold the pencil end down by hand to make sure it's writing. You can just concentrate on the cursor point on the original.

 

[wefalck]

This kind of sophisticated pantographs was used by cartographers in the old days, for instance, when they had to transfer the hand-drawn ordonance survey map originals onto the plates for printing. In fact, any time you needed a (technical) drawing for printing in a different size/scale you would have to re-draw it using a pantograph.

 

Important point by Bob about transferring points, rather than lines. The same technique was/is used by sculptors, when they want to transfer their clay 'bozzetti' (the design model of the sculpture) onto a block of e.g. marble - but using a 3D-rig.

[Bob Cleek]

Great old-time project! I used to love reading those old magazines as a kid. 

 

A 3D carving pantograph would be just the ticket for modelers who scratch-build those 17th and 18th Century "gingerbread" encrusted men-o-war. Such a device could sure make all that repetitive carving go a lot faster.

 

I must be missing something, but I don't see from the drawings how the "Z" axis operates. The cursor (tracer pin) and the cutter have to move up and down in proportional unison on the "Z" axis, just as they do in the "X" and "Y" axes, but I don't see a mechanism that would accomplish that. Any answers?

 

 

Edited April 3, 2021 by Bob Cleek

[Bob Cleek]

On 4/1/2021 at 4:24 AM, wefalck said:

Important point by Bob about transferring points (with a pantograph,) rather than lines.

Yes. I neglected to mention that when using this "connect the dot" method to draw curved lines laid out by points made with a pantograph or by points defined by a table of offsets, a batten and weights ("ducks") and/or curves are required, preferably a set of ship's curves if you can find them. (See: https://www.mp-artware.de/shop/en/Templates/Ship-curves/)   Drafting curves are more than just a bunch of pretty random shaped templates. The curves are mathematically generated so that in use a fair curve will be yielded. These curves are all segments of what is known as a "clothoid," "Cornu," or "Euler" spiral:

 

The principle of linear variation of the curvature of the transition curve between a tangent and a circular curve defines the geometry of the Euler spiral:

• Its curvature begins with zero at the straight section (the tangent) and increases linearly with its curve length.
• Where the Euler spiral meets the circular curve, its curvature becomes equal to that of the latter.

 

https://en.wikipedia.org/wiki/Euler_spiral (More than you'd ever want or need to know unless you are a Ph.D. mathematics wonk.)

 

For those who may be interested, and because I've often encountered those untrained in the use of drafting curves, the below explains the proper use of drafting curves to develop a fair curve:

 

Use of the French Curve

The french curve is used to draw a smooth line through predetermined points. After the points are plotted, a light pencil line should be sketched to connect the points in a smooth flowing line. To draw the finished line over the freehand line, match the various parts of the french curve to various segments of the freehand curve. Avoid abrupt changes in curvature by placing the short radius of the french curve toward the short radius portion of the line to be drawn. Change your position around the drawing board when

necessary so that you can work on the side of the french curve that is away from you. You should avoid working on the "under" side of the french curve. Place the french curve so that it intersects at least two points of the line. When drawing the line along the edge of the french curve, stop short of the last point intersected. Then move the french curve along to intersect two or three more points and make sure that the edge of the curve connects smoothly with the line already drawn. When using the irregular curve, you can draw a perfectly smooth curved line by plotting enough points (the sharper the curve, the more points you need) and by drawing in shorts steps.

 

Figure 3-10 shows how a smooth line is drawn through a series of plotted points. The french curve in view A matches points 1, 2, 3, and 4. Draw a line from 1 to 3 only (not to 4). At B, the curve matches points 3 to beyond 4. Draw a line from 3 to 4 only (not to 5). At C, it matches points 4, 5, and 6. Draw a line from 4 to just short of 6.

At D, it matches a point short of 6 to beyond

7. Draw a line from 6 to 7.

At E, it matches a point short of 7 to beyond

9. Draw a line from 7 to 9.

At F, it matches a point short of 9 to beyond

11. Draw a line from 9 to 11.

You will probably notice how the french curve is turned over and reversed to find portions that fit the points on the line with increasing or decreasing changes in curvature.

When you are drawing a curved line that extends into a straight line, the curve should be drawn first, and the straight line joined to it.

 

https://www.tpub.com/engbas/3-8.htm

 

It is possible to generate these curves using some of the very expensive and highly sophisticated CAD programs today, but I've read that because there are so few straight lines in a vessel's drawings, manual drafting still offers advantages over CAD in terms of programming time saved.

 

See further extensive discussion of the use of curves at: 

 

 

 

Edited April 3, 2021 by Bob Cleek

[wefalck]

We are veering off a bit from the original subject of thread ... nevertheless the article quoted above seems to show an ordinary 2D pantograph engraving machine, though I didn't carefully look at all the details.

 

As matter of fact, such engraving machines for door-bell signs, fountain pens, sports trophies (with special mounts) are an application of pantographs that persists until this day. The letters etc. to be engraved come in sets of templates. The machines and the special grinding machines for the engraving bits are still being sold.

 

Otherwise, pantograph work has largely been replaced by CAD and CNC-milling or laser-cutting.

[Bob Cleek]

13 hours ago, wefalck said:

As matter of fact, such engraving machines for door-bell signs, fountain pens, sports trophies (with special mounts) are an application of pantographs that persists until this day. The letters etc. to be engraved come in sets of templates. The machines and the special grinding machines for the engraving bits are still being sold.

And travelling even farther afield in the discussion, mention should include the once-ubiquitous LEROY lettering system used by draftsmen (and comic book artists) in later times when hand-lettering as an art form was lost when the ISO standard font was dictated. the LEROY system used a pantographic planchet and templates. The  LEROY kits and standard ISO font templates are still quite commonly and inexpensively available on eBay, but the older, and much wider selection of fonts and templates more frequently used prior to the ISO font standards' implementation are now quite rare and highly collectible. Old-style lettering systems can be handy for modelers sometimes, although digital fonts generally supplant them.