Multi-dimensioned Drawings

Purely out of interest have a look at the following drawing from the description of LBSC's Netta where the axles for gauge O, gauge 1, 2½", 3½" and 5" are all shown together.

That looks to be very bad practice to me, very confusing and open to mistakes.

Normally you would assign each dimension a letter, and then tabulate them in a chart on the drawing for each alternative size.

Phil

Probably comes from the days when the machine shop planer would strike out the dimensions not required, so that there was only one set left.

Confusing at first blush but ok once you work his system out. I guess you were expected to have a modicum of initiative in those days compared with modern practice.

The use of fractions still drives me nuts as i have to look up the decimal equivalent every time. I guess those old guys had them all in their head, or did everything with a steel ruler and calipers.

That's why my old Moore & Wright micrometer has decimal equivalents engraved on it

If you happen to have an iOS device ...

This is brilliant : **LINK**

https://apps.apple.com/gb/app/fraction-calculator-plus/id504494723

MichaelG.

Provided parts were fitted to each other, would there be any need to measure more accurately than the 64ths divisions of a rule? Until recently the only way I would have been able to set the lengths of those axles would have been with a surface gauge and a 4R rule

Just because we can buy instruments graduated to 0.001mm doesn't mean we have to (or that the measurement will be that accurate). I spent a large part of my career explaining to engineers that specifying unnecessarily tight tolerances wastes time and generates an excess of either scrap products or concession notes, adding to the cost without benefiting the customer.

Brian G

Initiative? Wonder how many of todays "Managers" can flip between fractions, decimals and metric measurements WITHOUT a smart(?) phone let alone the great unwashed. Used to be par for the coarse before electronic calculators, computers and t'internet and non disposable income. Wonder how many muddle ingineers are working to microns, obviously outworkers for the Swiss watch industries where interchangability is a necessity? Fitting seems to be a forgotten art for one offs.

Regards Ian.

As far as limits and fits are concerned, back then, certainly in my 50 years of draaughting BS or ISO standards were rarely used. Some companies used the Newall system but most older engineering companies, and a lot of these were established around 1900m had established their own standards which they continued to work with until they needed to standardise. The reason for standardisation was the decline of the "make all" factory, where the raw materials went in one end and the finished goods came out the other with no subcontracting. Since, probably the second world war, industry changed and manufacturers did what they did best and let some one else make the other bits. So now we have drawings with all the information on to make a fully interchangeable part so that everybody who reads it has the same information without query.

The practice shown in the drawing in Nick's post may have had more to do with magazine publishing of the time than general engineering practice. LBSC may have had some editorial pressure to produce more bang for the buck and get more data for a wider audience on fewer costly pages. In different biographical accounts of LBSC there are some references to his interactions with the editors of various magazines he wrote for.

I personally would find it distracting to work to such drawings but as Hopper said you soon work out which set of dims is the one for your gauge / scale. It would not take long to circle the pertinent dims on each drawing as you went, or maybe make your own dimensioned sketch. This is akin to making your own CAD files these days to weed out as many errors as possible from long-published model engineering drawings still circulating.

As to fractions, I expect LBSC wrote to the wider audience of working people and trades people as well as the aristocracy of the time. The average guy could probably afford a fractional 6" steel rule but maybe not a micrometer or a slide rule to do decimal conversions. LBSC also published instructions to use commonly available items as substitutes for costly engineering tools - like setting valves to "the thickness of a tram ticket" spacing, or "use a bicycle spoke". His main point was that anyone could build a people hauling live steam locomotive if they really wanted to, and his articles were intended to teach anyone of any social position (that could afford the magazines he published in, that is) to do it.

I'd not be too worried by multiple dimensions as long as they are coherent and reasonable easy to follow: as others say, simply highlight the relevant ones, or make a copy with them alone.

More to the point is having drawings without errors! I wonder how many projects have come to grief over that.

Oh, I use things like drill or milling-cutter shanks as gauges, bits of old plastic bank-cards - our town never had trams so no tram tickets - and the like; though I do measure them with a micrometer. Actually that's reciprocal. Ground cutter-shanks are good for verifying micrometers. I set my mill's DRO read-heads using a plastic feeler-gauge cut from an expired caving association card. I do need use the firm-joint caliper and rule sometimes.

'

What I have noticed elsewhere on this forum is something of a corollary to this thread. This is the fretting about model-engineering drawings not published to the very latest industrial presentation to ISO-rhubarb, rich in tolerances, correct line-thicknesses, proper boxes of precise material and finish codes, "approved by " and revisions lists, etc.. A certain point-missing, one thinks...!

Besides, model-engineering often means replicating in miniature, machines originally built using rules, stiff-joint calipers and genuine blue-print copies of linen tracings of beautifully-made pencil drawings.

I could live without the suffix " bare " though. So-many-sixty-fourths are fine and solved by the Tracy Tools conversions poster... but is that an Imperial Doncaster "bare ", an ISO-approved Thetford " bare "... ? Perhaps I'll use the " just-about-fits bare " .

Maybe we are spoiled - though no, I don't pine for the chain-drill, cold-chisel and file, despite sometimes needs-must.

Thanks MichaelG for the link although I OK with fractions I am these days lazy

H

The Apple store offers various calculators for fractions - but how can one tell which are FREE and which require payment?

I have not been able to set up my iPhone for payments - and it has NOT proved a problem to date.

MC

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Just look on the AppStore listing ...Either there will be a price listed, or the word GET if it’s free to download

Some ‘free’ Apps offer in-App purchases ... which are detailed in the listings.

All that ^^^ presumes that you are at least able to access the AppStore

... it seems to rather limit the scope of an iPhone if you cannot

MichaelG.

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P.S. ... I would happily do a screen-shot for you; but because I have already bought the referenced App, the current price is no longer displayed to me.

P.P.S. ... I use the iPad

Edited By Michael Gilligan on 07/04/2021 08:02:42

Perhaps one of these!

**LINK**

FC

Same people do an Android version **HERE**

https://play.google.com/store/apps/details?id=com.digitalchemy.calculator.freefraction&hl=en_GB&gl=US

Thank you for taking the time to respond.

I have now installed the calculator on both iPhone and iPad. it appeared that the same thing was available at £3.99 and free. I'll see how useful it is in practice.

I have been using a Hewlett Packard 11C calculator since the mid 70s. That uses Reverse Polish Notation and I've found that it's available for the iPad - "Touch Fin RPN" without charge.

This is an exact copy of the physical calculator and can be switched from Scientific to Financial functions (which the physical one can't)

I find it very difficult to use a calculator with algebraic notation these days!

MC

I tried clicking the link at the end of the film but nothing happened!

I wondered if it's possible to buy one of those rulers in the United Kingdom

MC

Nigel

I agree with your comments above. The drawing in the opening post is one of the most diabolical pieces of rubbish I have seen. Ignoring any standards, they are to a certain extent irrelevant, the purpose of a drawing is to provide with clarity and without any ambiguity all the information required to manufacture or assemble an item. Initiative has never been a requirement for reading drawings. Another Interesting point, having spent 40 years working as a Design Engineer ending up as Chief Designer in industry, I had never come across the term 'bare' until I looked at the drawings for my Aspinall. I had to Google it to make sure I understood the context!

Dave