Stuart D10 Metric Plans

Hi Richard you have missed my point no problem working with 2.468 it is the converting of 1000's of fractions per Stewarts drawing into decimals that is painful, machine tools have dials now I know I will never buy another set of castings from Stuarts

Edited By Stephen Benson on 30/07/2014 15:24:58

Stephen, every engineer should have a small book of decimal equivalents,

1/64" = .0156

1/32" = .0312

1/16" = .0625

1/8" = .1250 etc etc

Just use a calculator......................................

Converting fractions to decimals usually means pursuing excessive accuracy. The fractional dimensions on a Stuart drawing are intended to be 'rule dimensions' and the parts should be made to fit each other.

These kits were originally designed for builders who probably didn't own a micrometer or a vernier caliper and certainly wouldn't have had handwheel dials on their lathes!

For those unfamiliar with fractions a calculator does make it easy. 15/64" literally is 15 divided by 64 = 0.234"

When converting to metric I use: fraction x 25.4, so (15/64) * 25.4 = 5.95mm

A tip, when using the calculator, don't round off until you have finished the calculation.

Cheap rulers and expensive micrometers usually have a table of equivalents (fraction/decimal inch) stamped onto them.

Neil

Nobody said it was hard to do I have a maths A level and I quite like doing trig when needed, but it is tedious to do every dimension when I would rather be cutting metal, but it seems I am alone it in this view. There are plenty of interesting projects with metric drawings out there so no problem for me however I did feel that Stuart Models were missing out but obviously I was wrong

Hi Stephen

You didn't explain it was tedium rather than knowing the methods that was your problem! There are plenty of younger people who have no experience of using fractions, so hopefully these posts will be of value to them.

As for Stuarts, they will change if they get customer demand, but I know there's a cost to having the drawings redone and proven in metric as this means converting to use sensible units (e.g. 6mm for 1/4" rather than just converting each dimension. Presumably they just don't get enough requests for metric drawings for it to be worth the investment?

Neil

About thirty years ago there was a metric version of the Stuart 10V published. The Unimat lathe people at the time were providing a set of castings with a booklet, all in metric. I would still have my copy somewhere, but please don't ask me to find it at the moment. As already mentioned a D10 is just a doubled up 10V.

But anyway, my experience of Stuart castings over the years has been that quite often there is not enough metal to clean up to the nominal size, so you end up making changes to get the fits anyway. For instance a valve chest which the drawing says should be machined to half an inch thick will already be a hair under half an inch in the rough cast state. So you have to have a think about the effect that will have on other dimensions anyway. Not so bad with valve chest thickness, but with some items the effects can be far reaching.

John

I worked in Drawing Office for a time and was tasked with getting the Draftsmen off their boards and on to computers it turned out to be much easier than you would think as they could see the advantages, production trebled in a matter of weeks. One of the thing we were very keen on was that they should make it easy for the machinists to read and use no calculations should be done on the shop floor everything from a common datum making use of the digital readouts all the machines had so I guess I am a bit more sensitive to bad drawings than most especially as I know how quickly they could be redrawn.

Edited By Stephen Benson on 31/07/2014 10:14:24

To no one in particular, to be a model engineer it is some times an advantage not to be a professional engineer, it's a branch of engineering where you need to visualise the thing you are making, be your own draftsman, either pencil and paper, or computer. Then your own metallurgist, sorting the right materials for the job, then get out and get the stuff, castings, bar stock what ever. Only now do we start putting things together. This is my way as I design, and build my hot air/Stirling Engines from scratch.

I did delve into the wonders of Stuart Tuner with the restoration/rebuild of an S9, unlike the Stirling engines that are a mix of imperial, and metric measurements, the S9 was all imperial. Ian S C

> I know how quickly they could be redrawn.

A fair point, but I was suggesting that the Stuart drawings need to be redesigned, not simply redrawn.

Neil

I started new into ME about 10 years ago having only ever used metric my whole life - I went down the route of converting everything only to find that I much prefer imperial now used to it and dont like using metric. Give it a go, its much nicer to work with IMO

My workshop is all metric, I do have some imperial slot drills and jobbers.

I'm on my second Stuart Model and the conversion isn't a problem. Excel will produce a chart tailored to the users short sightedness, which can be laminated and becomes extremely long lived.

I usually have a calculator to hand too. I just don't find the conversion an issue.

I have a similar chart which is fractional inches to decimal inches,  but never used it.

Steve

Edited By Steve Withnell on 31/07/2014 21:31:09

Edited By Steve Withnell on 31/07/2014 21:31:34

That is good to hear the castings must be flying off the shelves at Stuart Models with all their customers perfectly happy to convert their drawings dimensions to decimal imperial, does not follow any business model I am familiar with but I am pleased to be proved wrong.

Well, they have been selling them that way since about 1898 so they must be doing something right.

I think Imperial fractions are daft myself, but I wouldn't let that stop me making something I liked.

John

.

This :- (iPhone app or similar)

Plus :-

Plus :-

Plus :-

Half an hour with the drawing and it was all sorted for my Stuart James Coombes. While doing it I was familiarising myself with the general layout of the engine, which I imagine is time most people spend anyway.!

Nick

I think we are missing the point. Stephen isn't asking HOW he just can't understand WHY Stuart don't revise their drawings.

Neil

Fair point Neil.

Perhaps someone should email them a link to this thread.?

Nick

I don't suppose there is great demand. As Neil has said, the engines would have to be re-designed, not just re-drawn. Although it is great to see a few contributors to the various forums from continental Europe, it is clear that Model Engineering is largely confined to the English speaking world and of those the majority are in GB and the USA. I would bet that the overwhelming majority of lathes in UK home workshops are imperial, even more so in the US and these must surely be the biggest markets for Stuart. Metric fasteners in model sizes are still a niche market for the model engineering suppliers.

I am sure it would be forward thinking of Stuart to provide their kits in either Metric or Imperial form but the history of Stuart and the likes of Reeves show that being a model engineering supplier is a precarious business. The business risk involved in dual offerings would be considerable.

That's my take on it anyway.

Cheers,

Rod

It would not end with just the engine being metrificated, they would then have to stock a range of metric (fine)threaded steam fittings, fixings and carry suitable barstock to make up the kits. This all ties up capital and needs to be stored somewhere.

Personally I'd rather see any investment put into reintroducing some of the discontinued casting sets and updating any patterns/moulds so we have a bit of metal to machine off the castings.

J

My Stuart 10V drawing are covered in pencil conversions from fractions to decimal. An annoyance yes, major issue not really. As for metric, don't see the need. I can quite happily work in either metric or imperial. Have to say that I am happier with the latter. I learned metric at School in the '70s only have to learn imperial when I started in the aircraft industry in the '80s.

The issue was never the fact that the drawings were in imperial the problem for me was that fact that they are all in fractions and incremental.

It would very easy to lose the fractions and replace them with imperial decimal almost every customer has to do this for themselves as evidenced by this thread I would guess very few mark out the castings as the designer intended.

Slightly harder would be to make the dimensions come from a common datum I agree to make them metric would be impractical without a redesign but the longer they put this off the more customers they will lose in my opinion as already mentioned Stuarts are largely ignored by Continental Europe and of course the biggest new market is China which has always been metric.

Edited By Stephen Benson on 01/08/2014 12:34:41