Conversion

Advert

New Replies

Report Bug

Help/FAQs

Conversion

This topic has 9 replies, 7 voices, and was last updated 13 April 2010 at 21:25 by Terryd.

Viewing 10 posts - 1 through 10 (of 10 total)

Author

Posts
9 April 2010 at 15:08 #50552
Alan Gordon 2
Participant
@alangordon2
My skills at the moment are “fair” but as time goes on I hope to aquire more skills to undertake this construction, however what are people”s views on converting to metric measurments as one “goes along”

Regards

Alan
Advert

9 April 2010 at 15:08 #5028
Alan Gordon 2
Participant
@alangordon2
9 April 2010 at 17:30 #50555
JasonB
Moderator
@jasonb
Don’t see anything wrong with it myself if you find it easier to work in metric.

Quite a good ongoing build of the engien here that you may find helpful.

Jason
9 April 2010 at 22:20 #50572
Peter G. Shaw
Participant
@peterg-shaw75338
Hi,

Funnily enough I was recently reading Tubal Cain’s book on Workshop Drawing (WSP 13) and somewhere in that book he comments about converting to metric. Unfortunately, I can’t now find the reference. Anyway, from memory, the gist of it was that converting say 3/8in (eg a drilled hole) to metric becomes 9.525mm which in turn then implies an almost impossible level of accuracy, to say nothing about the availability of such a drill. It is important to realise that quoting 3/8in implies a specific level of accuracy which is actually less than the decimal equivalent (0.375in) and which in turn is less accurate than the direct metric conversion mentioned above.

What this means is that you would have to convert every imperial dimension to the equivalent level of accuracy of the original. And not forgetting any matching component, and any bolts, rivets, rods etc.

In theory, it sounds nice to convert, but in practice for something like this, I think one should stay in the original measurement scheme unless you are prepared to do virtually a redesign.

Just my thoughts,

Peter G. Shaw
10 April 2010 at 07:11 #50577
David Clark 13
Participant
@davidclark13
Hi There

I can’t see the problem with buying a 9.525 mm drill. It might be marked 3/8in. but it will still be a 9.525 drill.

regards david
10 April 2010 at 10:18 #50584
Ramon Wilson
Participant
@ramonwilson3
Alan,

There is nothing wrong in directly changing dimensions from imp to metric. Personally I do it all of the time when milling because of having a DRO fitted and the ease in which that can be done. On the lathe it’s different – that has imp dials so that’s what system is used. If that had DRO I would be using metric on that too. Again a personal thing but despite being of an age when imperial was ‘ingrained’ I find using metric much easier.

The problem can be if, when converting, you ’round up’ (or down) to meet available materials etc and particularly so if you do this as you say “As one goes along” On a carefully thought out and proven design such as you intend to make you need to be sure that anything changed at one point does not lead to a problem further down the line. However a basic change of a dimension directly from imperial to metric should not cause any issues.

My own preference is to sit down with the drawings before work starts and convert the dimensions either from fractions to decimal/metric or directly to metric. I use red ink so that it shows well for old eyes!

Hope this helps in some way – Good luck with your project.

Ramon

The above goes on the assumption that the relevant measuring kit is to hand. i.e. working on an imperial machine ‘in metric’ and measuring in metric then converting back to put the next cut on is is not what is meant!

Edited By Ramon Wilson on 10/04/2010 10:23:55
10 April 2010 at 11:24 #50589
Terryd
Participant
@terryd72465
Hi Alan,

Good luck with this engine, it is a real beauty when built. I have the honour of knowing Eric Whittle but haven’t seen him for a couple of years, since our ‘real ale’ village local was rebuilt and turned into a gastro pub! I’m not bothered about metric or imperial argument I am tooled for both and can slip from one to the other despite being schooled in imperial I had to work in metric as a draftsman. However I am bothered about about the much more serious problem of traditional pubs being closed. They’re one thing we do better than anyone in the world.

However, back to the V8, I have seen and held the original engine and seen it running and it is every bit as beautiful as the pictures. Eric is an irascible old b””’r but loves to tell anecdotes and talk about his modelling. This engine has won prizes in the UK and USA modelling events and was once stolen from an exhibition in the USA, but luckily it was recovered. Eric never did explain how but I’m sure it would have been interesting.

He also loved to talk about his wartime experiences in the RAF and was in his element describing the awful conditions for the flight crew of a Lancaster (even though he didn’t fly in anger. great man, great engine.

There is a youtube vid. of the engine running ihere:

http://www.youtube.com/watch?v=B-SNDErd1IM

I have a copy of that video and also have more videos of the engine which I’m sure that I could post somewhere if I can get to see Eric and gain his permission as he has the copyright.

Best of luck
10 April 2010 at 16:26 #50610
Circlip
Participant
@circlip
OK Alan you say at this point in time your skil is “Fair”. How are you with Numbers. If you check back, the metrication issue has cropped up many times and found to be WANTING. (Look at the Stan Bray dual dimensioned engines) I did it for Borderer, but the simple conversions don’t work so be aware what you are trying to achieve.

Very basically Ramon has given you the best approach, (I did it exactly the same way) Photocopy/print all the drawings and sit without any distractions and go through the lot noting the bits that interact WITH EACH OTHER and the build up of “shuffled” dimensions.

DC1 has given a simplistic veiw on a 3/8″ dimn. BUT 3/8 = 9.525mm Fine, that’s a hole, what fits in it? A shaft? and what Dia. is that going to be?? 3/8″ dia raw material, 10mm turned down to 9.525,?? But rounded, 3/8″ = 9.6 or 9.5,? Hmm B****r, see where I’m going??

I had an advantage when doing mine,

   A. A lifetime in full size ingineering.

   B. Lots of it as a designer.

   So the interaction between the bits was fully understood. I’m NOT trying to put you off, you can do it, but just be aware.

Oh yes, then there are the screw sizes ——–

Regards Ian

Edited By Circlip on 10/04/2010 16:27:21
13 April 2010 at 09:23 #50659
Alan Gordon 2
Participant
@alangordon2
Thank you gentlemen, this is all good stuff, i will take Ramon’s advice and go with it. I am in the process of Building the Nemett Lynx the construction of which is going well !! (touch wood).

Once i have completed this I propose to start on the V8. This will give me time to go over plans and convert. wish me luck ?

Alan
13 April 2010 at 21:25 #50674
Terryd
Participant
@terryd72465
Hi Alan,

I’ve put up some pictures in the album section of Eric Whittle’s original V8 engine which he designed and built, and used as the basis for the ME articles. I hope that they give you some inspiration. I have a whole bunch more (plus a couple of videos of the engine operating). If you would like to see more, just let me know.

Regards

Terry
Author

Posts