Not fit for purpose

[David Clark 13Participant @davidclark13]

Hi There

Topic now set up in general discussions.

regards David

[Michael GilliganParticipant @michaelgilligan61133]

Thanks David,

Much appreciated

Provided you can keep posters "on-topic" … I think that's a practical way forward.

MichaelG.

 

Link to Topic

Edited By Michael Gilligan on 30/06/2012 11:48:31

[John Stevenson 1Participant @johnstevenson1]

The Model Engineers Clearing house web site has had a post up defining known faults for ages but it still doesn't stop this subject being raised time and time again.

If you search most popular plans have pages where corrections are listed.

However as David has said many are not mistakes but errors in reaing and this then spawns further posts where someone is usually told to go to specsavers.

John S.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks John … I was unaware of that.

However,I still think it "proper" for the ME/MEW forum to host its own review of the drawings.

MichaelG.

[Ian S CParticipant @iansc]

I think that if anyone has a problem with a published drawing, they could after building the subject of the drawing, redo it, and foreward it to the publisheras an updated and corrected version (and hope to h**l theres no misstakes). In my oppinion, just get on, its part of engineering, you get misstakes in the big boys world too as pleant have found. Ian S C

[KWILParticipant @kwil]

I have for a number of years always sketched the item from the plan with my own annotataion from the given dimensions. When I am satified, I move onto cutting metal. This also applies to looking at General Assembly drawings and sometime drawing these out as well to see “if it fits”. I have been told of some “known errors” on published drawings which if you follow the dimensions you end up in trouble. On a Martin Evans design, “impossible to make”, however careful assessment of the parts showed clearly there was in fact tolerance in hand and my informant clearly could not work to drawing, correct or not!

[doubletopParticipant @doubletop]

I do find this all mildly amusing. From what I can see this topic of errors on plans seems to crop up regularly and has no doubt been a problem from issue 1 of ME. I consider myself a beginner albeit now with 2 years behind me. I've built the Northumbrian and it runs, I didn't use the plans, just the magazine articles. Before I started I asked if there were any problems and David, Jason and others pointed me at all the known issues. In my journey I found more and published them on the Northumbrian thread.

My point; It’s clear there have always been errors in drawings, there always will be. In the past model builders either put up with it and suffered in silence or wrote a letter to the editor and may or may not have got a reply in a subsequent issue. No doubt some months later. We now have the Internet so we either use it as a means for near real time whinging or better use of the forum and report and check for errors. No need for re-prints, or rebuilds to check corrections, just everybody contribute errors as they find them. Subsequent builders can check and confirm for themselves if the reported issues are material or not.

That said MHS still has a duty to ensure the quality of published plans but won''t find everything so “Buyer beware”.

Pete

[Tony JeffreeParticipant @tonyjeffree56510]

Posted by Doubletop on 01/07/2012 11:31:55:

My point; It’s clear there have always been errors in drawings, there always will be. In the past model builders either put up with it and suffered in silence or wrote a letter to the editor and may or may not have got a reply in a subsequent issue. No doubt some months later. We now have the Internet so we either use it as a means for near real time whinging or better use of the forum and report and check for errors. No need for re-prints, or rebuilds to check corrections, just everybody contribute errors as they find them. Subsequent builders can check and confirm for themselves if the reported issues are material or not.

Pete

 

Yep – exactly so. Drawings of any significant complexity share this characteristic with software – the one thing that you can always say about a piece of software is that it has bugs. Interestingly, as David has observed, every time you attempt to fix a bug in a programme (or a mistake in a drawing) you run the risk of introducing more problems that weren't there before, whether or not the original bug gets fixed in the process; also, the fact that a "bug" has been reported is no guarantee that the problem reported really is a problem or just a misinterpretation on the part of the reader/user.

Consequently, maintaining software of any kind, be it drawings, programmes, or whatever else, is a non-trivial problem, and frankly, one that My Hobbystore as an organization isn't geared up to handle – if it was, you could probably add a zero onto the price of the magazine (seriously), and I don't think any of us, including My Hobbystore, would be up for that.

IBM used to track the rate of bug reports on each software package they released & it goes through a repeatable pattern – initially, a high rate of reports (and fixes to them) when the package is first released, then it plateaus out as the major and obvious bugs are dealt with, then the rate starts to rise again as the fixes to the more obscure bugs start to generate more problems than they solve. At that point, they used to stop attempting to fix any further bugs, and (if necessary) started work on a total rewrite. But the point here is that you will never reach the point where there are no bugs to fix.

So, "Fit for purpose"? Most definitely yes – the purpose of the articles & designs published in these mags and in the re-printed plans is to provide a starting point and ideas for the budding Model Engineer to work with and to develop his/her creative abilities; emphasis on "starting point" and "Engineer" here – they aren't intended to be instructions provided to a production team in a factory. If you are expecting to be able to follow one of these drawings blindly, without applying any engineering thought and without checking that everything you see on the paper is correct, then it is YOU that is not fit for purpose, not the drawing.

I have built things over the years from various articles published in the various ME mags and books; I don't think there has been a single instance where I can say, hand on heart, that the drawings/build instructions were 100% accurate; equally, there hasn't been a single instance where I haven't said to myself "There's a better way of doing that" and followed a different path. Sometimes the different path has proved to be a dead end, and I have realised that I should have done what was suggested; other times, my ideas have improved on the original. Either way, you come out of the process knowing more about ME than when you started, and to me, that is the real purpose.

Regards,

Tony

Edited By Tony Jeffree on 01/07/2012 12:42:21

[John Stevenson 1Participant @johnstevenson1]

Posted by Tony Jeffree on 01/07/2012 12:39:32:ne (seriously), and I don't think any of us,

If you are expecting to be able to follow one of these drawings blindly, without applying any engineering thought and without checking that everything you see on the paper is correct, then it is YOU that is not fit for purpose, not the drawing.

Regards,

Tony

Edited By Tony Jeffree on 01/07/2012 12:42:21

Very good post Tony.

This "fit for purpose " handle is abused no end nowadays but there are two sides to the story.

Said Herbert rushes into Machine Mart / Warco / Arc / Chester [ delete as nessesary ] and buys a lathe / miller.

Takes said item home, unpacks it and starts to knock lumps of metal but because of his / her inexperiance nothing comes out as it should.

So play the "unfit for purpose card " but how does the seller know the USER is fit for purpose ?

Take a car, you need training or having to pass a test to use it on the road. Personally i have met people who i wouldn't trust with a toothbrush.

John S.

[Ian S CParticipant @iansc]

One thing, in the very early days of ME you (well your great great grandfather could) could write in, and if your letter arrived even just a few hours before printing time it could be included in that issue, and possibly a reply also, so that within a week of an artical appearing, you could ask about a misstake in a drawing, and have it corrected. Thing have changed a little since then have'nt they. Ian S C

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Tony Jeffree on 01/07/2012 12:39:32:

Posted by Doubletop on 01/07/2012 11:31:55:

My point; It’s clear there have always been errors in drawings, there always will be. In the past model builders either put up with it and suffered in silence or wrote a letter to the editor and may or may not have got a reply in a subsequent issue. No doubt some months later. We now have the Internet so we either use it as a means for near real time whinging or better use of the forum and report and check for errors. No need for re-prints, or rebuilds to check corrections, just everybody contribute errors as they find them. Subsequent builders can check and confirm for themselves if the reported issues are material or not.

Pete

Yep – exactly so. Drawings of any significant complexity share this characteristic with software – the one thing that you can always say about a piece of software is that it has bugs. Interestingly, as David has observed, every time you attempt to fix a bug in a programme (or a mistake in a drawing) you run the risk of introducing more problems that weren't there before, whether or not the original bug gets fixed in the process; also, the fact that a "bug" has ………………………………..

Regards,

Tony

Edited By Tony Jeffree on 01/07/2012 12:42:21

Hi, I'm no expert in CAD, but for a few years now I have used a cheap CAD programme to plot out my family tree in the old traditional way, which I can then print out on my A0 printer. This has not presented me with any significant problems, but as more information was added I found that errors were creeping in. It turned out that the errors were induced by myself by not realising that information that was already in the programme were accidentally highlighted while adding new information. Following on from this, I continued to be vigilant as to make sure that nothing else was highlighted while adding or updating more information and checking everything before saving, however, as the tree became bigger, the task of maintaining correctness became more involved.

Even when I got to the stage of the first printout, and checking everything before hitting the start printing button and then reviewing the the printout afterwards and believing it all to be OK, errors were found when other members of my family viewed it.

So yes even when you believe you have done everything correct and there is no one else to blame, errors can still creep in and it takes more scrutiny to make sure you don't make more errors when correcting those that you find, especially when the programme gets more complex.

Regards Nick.

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