Pitch Circle

[Roy BirchParticipant @roybirch29994]

Hello Howard

Actually going to a local club was where it all started, I knew the director at Myford and he had a part built Maisie just arrived that he let me have, I was his Tailor, I went along to the local club, I live near Cambridge and 1 person bought in for me to photo his build of Maisie, but that was it, no one else was interested in really talking to me as it seemed a boys club just for a select few boys, I did go to the Saffron Walden club at Audley End and they were great but they now seemed to have vanished. So after the visit I just shelved the projects much to my regret and sadness. It is during this lockdown and no business to open and run in London that I kept looking at my Myford Tri-Leva and Boxford VSL500 that I thought I have to build something as I have a well equipped workshop just idle and lets be honest some of you guys build the exceptional from very little.

[Roy BirchParticipant @roybirch29994]

Hello Dave

One thing is clear though, everyone on here has a lot more common sense than me, I did start with the Rob Roy before getting Maisie but the then editor of Model Engineer who was Mike Crisp I believe told me I should start with an engine I liked as I had far more chance of finishing that loco, so I had two in mind, Virginia and Gresley A4, as you can see from these choices I aimed low using my bounds of common sense until a visit to the model engineers exhibition had 1 stand laughing at the thought of a first timer with no complete loco on his list building an A4.

[Rik ShawParticipant @rikshaw]

I think it might have been a couple of weeks ago someone on here had written a prog/code to calculate PCD's using XY co-ordinates. I seemed to remember that the co-ordinates could be calculated from a point outside of the circle and that is what interests me in a jig boring sort of way. I have looked back at previous posts but cannot seem to find this one.

Apologies to the chap who was responsible but I cannot remember his name. If you can prod me in the right direction I would be grateful.

Rik

[Howard LewisParticipant @howardlewis46836]

Hi Roy,

I envy the folk who have the skill and patience to produce working and highly detailed models.

My stuff just gets made from whatever is lying around! Which explains changes of course, mid voyage!

You are not too far away from me, in Peterborough. (Waiting for Club meetings to resume and see friends again )

Have never visited, but have met a couple of members of the Cambridge Club. Sounds a good place to join./ visit.

With a lathe, ALL manner of things are possible.

Howard.

[old martParticipant @oldmart]

A very useful addition to any workshop would be a Zeus book of engineering formula. There is a page showing how to produce pcd's using X and Y coordinates on mills and jig borers if you don't have the luxury of a rotary table.

[Roy BirchParticipant @roybirch29994]

I actually have both but it was not until this morning that I realised the zeus book had this in, that said due to the help from others here I wont face the problem again hopefully.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Roy Birch on 22/06/2021 14:23:49:

…I went along to the local club, I live near Cambridge and 1 person bought in for me to photo his build of Maisie, but that was it, no one else was interested in really talking to me as it seemed a boys club just for a select few boys…

This is a common problem with clubs because most ordinary folk are nervous of newcomers. They are more afraid of you than you are of them. Stranger danger! It's well known that the only two Englishmen within 5000 miles who find themselves sat next together for a week in a train crossing the Gobi Desert won't speak unless they've been introduced.

Some clubs arrange a special greeter to make sure newbies aren't put off by their initial cool reception, most I've attended leave folk to get on with it.

The secret is to persist. Quietly find out what each member is into, who is approachable, and who the gits are. Mutual acceptance grows each time you turn up. Smile and nod a lot, and ask appreciative questions. Amazing, how did you do that?

After 3 or 4 visits, you will be Chairman…

Dave

[Former MemberParticipant @formermember12892]

[This posting has been removed]

[BazyleParticipant @bazyle]

I dropped in on the Cambridge club two years ago as I happened to be in the city on a Sunday and found them extremely friendly. After tea and biccies I got a ride round the track on a loco that happened to be needing a test run, then a guided tour of works in progress. Seems likea great club if you can afford to live in the county.
A lot of men seem like grumpy sods so at a club those ones are the ones not deep in conversation with others, So the newcomer seems to be drawn to them with inevitable bad results. Don't expect club members to recognise that you are on your first visit and welcome you appropriately. I can't remember half the members of either of the clubs for which I'm membership sec. Twenty years ago I could greet them all by name, but now the names sort of come to me a couple of hours later. When you arrive just say "I'm new here" so they know and can go into welcoming mode.

Rob Roy – the build was probably stopped when it was found the valve rods didn't line up. Common fault in the design – search the forum for mentions of this and other problems.

Miranda engine – are you going to build the boat? It is an interesting display engine but looks crap in the launch as it is too big by far and forget the boiler. There is however a great wheeze published on Paddleducks forum. If you turn it upside down by exchanging the base and top plates it makes a very nice paddle boat engine.

[Roy BirchParticipant @roybirch29994]

I am in no way trying to run Cambridge MES down, there were some seriously clever people there, I also got to do a couple of laps on a 7 1/4 gauge loco, in many respects I looked at what they were doing and the Locos that had been built and felt completely out of my depth, I should now really go back and make a better effort, to be fair though I have learnt more in two days on this forum from a simple post than I have in 20 years.

Rob Roy was discontinued due to some errors but the thing I am learning here is that a lot of drawings have errors and with a bit of experience you learn to spot them. One thing I did as a cabinet maker when presented with drawings was to take the finished size and then subtract all of the components to hopefully end up at zero, any differences were spotted long before the mistake was made, if I had used the same thinking here I would have seen that some things just did not work, I knew 7/32 pitch circle was wrong but I did not know how, so I assumed that measure was taken from somewhere else, I just followed the error with out questioning it.

With regard to using the Zeus data book, I took a look at it last night and I realised that it did not have a 4 hole patten and I did not know if you could use some math to change a 8 hole patten. In any case the reference asks you for the pitch circle which I was still believing it was 7/32 so I would probably of still ended up here, this experience on here has now made me feel that I can just get on and if I get stuck just ask, I have also decided to stop reinventing the wheel and just use the full set of drawings where I can see the whole layout rather than A4 sheets of components.

Bazyle many thanks for the link to Paddleducks, that looks interesting and I might give it a go.

[JasonBModerator @jasonb]

For a 4 hole pattern where the holes are at 45deg to each axis like your drawing a simple method is to multipy half the PCD x 0.707

So 0.5 x 27/32 x 0.707 = 0.298" so you can mark off that dimension in both directions ( also shown bottom left of the sketch I posted)

If the holes are at right angles then they are simply placed on the radiu eg half of teh PCD so 0.5 x 27/32 = 27/64" or 0.422"

[Roy BirchParticipant @roybirch29994]

Many Thanks, So simple when you know how.

[egaParticipant @ega]

Posted by old mart on 22/06/2021 15:21:26:

A very useful addition to any workshop would be a Zeus book of engineering formula. There is a page showing how to produce pcd's using X and Y coordinates on mills and jig borers if you don't have the luxury of a rotary table.

Those handy coordinates have been omitted from my last-bought Zeus and I can't find the old ones!

[old martParticipant @oldmart]

I'm surprised that the jig boring coordinates are missing from a Zeus book as the metric revision has been out for a number of years. I have recently bought some copys marked issue 11/19 and the hole spacing page is about 3 pages after the UNF threads.

[Anonymous]

PM sent to the OP.

Andrew

[egaParticipant @ega]

Posted by old mart on 23/06/2021 18:34:58:

I'm surprised that the jig boring coordinates are missing from a Zeus book as the metric revision has been out for a number of years. I have recently bought some copys marked issue 11/19 and the hole spacing page is about 3 pages after the UNF threads.

Many thanks for that. I have just checked and the coordinates are indeed there on one of the middle pages.

I think I must have had in mind the omission of the "BA std threads" data from later editions; the BA tapping drill sizes are still present in the 1995 metric revision and the newcomers are, of course, the NC pages and the drawing symbols and abbreviations.

[old martParticipant @oldmart]

It would be a good idea for everyone with a Zeus book to run through all the pages, I have used them for many years, and surprised myself finding some info that I didn't know was in the book.

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