Planimeter

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Planimeter

This topic has 15 replies, 14 voices, and was last updated 30 July 2023 at 17:02 by Michael Gilligan.

Viewing 16 posts - 1 through 16 (of 16 total)

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31 December 2022 at 14:47 #626904
Speedy Builder5
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@speedybuilder5
Sorting through the dust and debris of the workshop, I uncovered again a planimeter, sitting in its box, nicely tucked up. I last used it probably 50 years ago to calculate the acreage of a piece of land.

Its a BOWEN & Co (America) model No1100 and the box is impressed U.S.C.E

Lovely bit of kit, plenty on the internet which probably don't sell, but what does one do with them these days ??

Bob
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31 December 2022 at 14:47 #3993
Speedy Builder5
Participant
@speedybuilder5
Planimeter – Who uses them now
31 December 2022 at 15:35 #626907
Michael Gilligan
Participant
@michaelgilligan61133
Store it in the Nuclear Bunker … for use after the great ElectroMagneticPulse bricks all the modern stuff.

MichaelG.
31 December 2022 at 15:51 #626911
Clive Foster
Participant
@clivefoster55965
Mine was new around 1980. Relegated to the loft donkeys years ago but too nice to bin. Unfortunately the box liner foam has collapsed so a serious clean is needed.

Clive
31 December 2022 at 16:13 #626914
Buffer
Participant
@buffer
The only time I used one of them was during a naval architecture course. We used it whilst making hull drawings to work out the area of each of the stations along the length of the hull. You could then work out the displacement and all the other performance coefficients. We didn't actually need to do it like that but they wanted us to do it old school so we understood what we were doing.
31 December 2022 at 16:20 #626916
Les Riley
Participant
@lesriley75593
The surveyors had them in the survey office at the collieries. Used them for working out the areas of coal that had been worked for royalty purposes and damage claims etc.

I used one just once at college as part of our course but would never need to use one in anger.

Les
31 December 2022 at 16:29 #626917
duncan webster 1
Participant
@duncanwebster1
I used one 50 years ago for calculating whirling speed of steam turbines. I'm struggling to remember the theory!
31 December 2022 at 19:08 #626931
David Ambrose
Participant
@davidambrose86182
There was I thinking that all the steam engine builders here worked out the IHP of their models by fitting an indicator, and using a planimeter to measure the area of the plot on the card to work out the mean effective pressure. Isn’t it something like IHP = PmALE/33000?
31 December 2022 at 21:57 #626957
Bill Pudney
Participant
@billpudney37759
My experience is similar to Buffer. I was a Draftsman at the Admiralty in the mid 70s. The task involved calculating the volume of spaces on a ship. The one that I was loaned from the store, was an English one (maybe Moore and Wright, but I 'm not sure), first purchased and calibrated on 1936. There were several inspection stamps suggesting that is was looked at every five to ten years. The instructions were excellent, however because the task involved lots of repetition calculations, I ended up not using the planimeter.

No doubt its in a Museum now, complete with my notes!!

cheers

Bill
31 December 2022 at 22:13 #626958
derek hall 1
Participant
@derekhall1
Posted by David Ambrose on 31/12/2022 19:08:23:

There was I thinking that all the steam engine builders here worked out the IHP of their models by fitting an indicator, and using a planimeter to measure the area of the plot on the card to work out the mean effective pressure. Isn’t it something like IHP = PmALE/33000?

Wow that brings back memories doing all that stuff in Technical College in the 1970's !
31 December 2022 at 22:59 #626962
Martin King 2
Participant
@martinking2
Hi All,

Have had quite a few of these lovely instruments over the years.

VERY limited market and they really don't make much when selling, we no longer buy them on their own.

Cheers, Martin
29 July 2023 at 23:21 #654350
Nigel Graham 2
Participant
@nigelgraham2
I wonder if any of the various steam-engine preservation / rebuilding groups use Indicators and Planimeter

.

The formula is HP= n[PLAN / 33000] where

P is Mean Effective Pressure in p.s.i. acting on the piston from lead to release ,

L = Stroke in feet,

A = Piston Area in square inches,

N = number of Strokes per minute (rpm X 2 for double-acting).

The denominator turns the top line product, in foot-pounds/minute, to Horsepower.

That 'n' is a fraction <1, or percentage, called the 'Diagram Factor', and is a rather empirical allowance for internal losses very hard or impossible to quantify. The letter was conventionally not an 'n' but a Greek character whose name I don't know, looking a bit like an 'n'. I think on a well-designed engine the Diagram Factor could be up around 0.8, even 0.9.

.

I can think of uses for planimeters in geographical work. Nature does not make areas of land, water bodies and the like to neat geometrical shapes. Nor, I very much doubt, really to those Fractals that were all suddenly so sexy to sum-smiths in the 1980s!
30 July 2023 at 12:36 #654396
Andy_G
Participant
@andy_g
Posted by David Ambrose on 31/12/2022 19:08:23:

There was I thinking that all the steam engine builders here worked out the IHP of their models by fitting an indicator, and using a planimeter to measure the area of the plot on the card to work out the mean effective pressure.

I knew I had used one as part of my engineering degree, but was struggling to remember what for – that was it, though: The lab had a large, single cylinder horizontal gas engine with an indicator fitted and we used the planimeter to measue the area of the indicator trace when analysing its performance.

Never used one since!
30 July 2023 at 16:41 #654434
Mark Rand
Participant
@markrand96270
When I recovered the drawings for the diesel engine at work when it was scrapped, with permission (so I could build a model of it in the future), there was an indicator and a planimeter in one of the cupboards. The engine was built in 1960-61 and used in the laboartories' building, that used to be the engine test house up until 2000 for peak load generation and blackout protection. It made a profit of £80,000 per year through the '90s…
30 July 2023 at 16:49 #654437
Roger Williams 2
Participant
@rogerwilliams2
Same as Andyg, our college had a single cylinder gas engine which produced an indicator diagram and we were tasked in working out the indicated horsepower with the planimeter. I often wonder what happened to that lovely engine.
30 July 2023 at 17:02 #654442
Michael Gilligan
Participant
@michaelgilligan61133
Not sure how readily any of them would adapt to Indicator Diagrams, but there are several ‘Planimeter’ iOS Apps available.

MichaelG.
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