Neat explanation of the planimeter

Sorry to hijack the thread. Can any one tell me why I can't post a new topic on this NG? It seems I can reply to threads, but not start one.Try as I may.... Thx.

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If you tell us which newsreader you are using it might help.

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I've never seen a cheap office type planimeter, or one in use. Hopefully I looked at the site but am still none the wiser!. I'm seeing lots and lots of maths and line drawings and animations, lots and lots and lots of words and a couple of grainy pics. But absolutely nothing on what (to me) is the show stopping critical feature, of how the integrating wheel manages to accurately turn when being dragged near sideways over paper. I used to deal with Honeywell mechanical gas mass flow computers. Their integrating discs were an expensive, complex marvel of mechanical engineering but it was quite clear from watching them how the X-Y-(Z) forces resolved. Not so with these office devices . The planimeter site could have been vastly improved by offering up an mpeg of one actually in use. john

File : New : News Message

must be something wrong with this:

Bye. Jasen

low friction bearings, as long as the friction of the bearings is less than the dynamic friction of the wheel-rim it'll turn acurately.

The one I used back in the 70's had fine grooves on the surface of the wheel parallel to its axle, so it would slide sideways and roll lengthwise. Useful for rough estimates on preliminary designs only even then.

Speaking of ancient mechanical curiosities, I recently uncovered some old operation and calibration instructions for a Bailey pneumatic PID controller, a "very very reliable" design from the 1940's, some of which are still in use today. I will scan the schematic diagram and post to ABSE for your entertainment.

Thanks. Fine bearing surfaces and the rim lines make good mechanical engineering sense.

mpeg

Blast from the past!. Yes I'd love to see 'em. Formative years in the 70's spent amongst petrochemical control rooms stacked out with 3-15psi Foxboro, Taylor, Kent, Honeywell etc control gear and some truly 'evil genius' pieces of air engineering which effected cascade control and computing functions. Every time I programme a sqrt routine on a PIC I think back to those massed ranks of Foxboro pneumatic 'square root extractors' and marvel as to how easy it all is nowadays. john

I got busy for a while but finally got around to scanning and posting some unfortunately poor quality schematics to ABSE thread title "OT: Schematics of Bailey transmitters and PID controller" The transmitter square root mechanism and the controller gain adjusting mechanism are both interesting IMO.

I haven't worked on any of these Bailey controls since '72, but I remember them like it was only 35 years ago. My memory was jogged by mention of a 2006 upgrade of a 1949 Bailey control system in Control Engineering. A 57 year service life for a control system is not too shabby.

Glen