Drawings of Stan Bray's Ossie

[districtgrandmaste]

I'm making this osillating engine from the Model Engineer drawings published from August to October 1998.

There are some omitted measurements - like the Piston Rod length for example - and I'm wondering if there is some other set of drawings available ? The articles say nothing.

I expect to scale off from the GA but would appreciate any comments.

[circlip]

July 98 to Jan2000 seem to have gone missing from my collection, despite dire threats to SWMBO we don't seem to know where they have been stored for "safe keeping" Is it not possible to work it backwards from the details for the other parts?

[paul]

I've got Stan Bray's book and have built or am building 3 engines from it. I've found errors in the plans for all of them so far so I wouldn't put too much faith in them (in my current engine the frame is shown as 35mm + 45mm + 35mm which apparently equals 100mm!!).

What sort of wobbler is it? Single/twin/Vee, single acting/double etc?

It may be that the design was incorporated into the book if so I might be able to help out.
As circlip says, if it's a simple oscillator you should be able to deduce/calculate most of the meaurements.

[districtgrandmaste]

Hi Paul - I have Stan Bray's book and 'Ossie' is not in it - so no help there.

The missing dimensions don't hinder me greatly - it was just a bit of a surprise to realize they are not there.

I know there are warnings sometimes about missing or wrong measurements on drawings. I've never learnt anything about making mechanical drawings and always admire those who create these things!

Thanks for the comments.

CEW

[paul]

Check out the clapper valve engine in the book - the metric and imperial drawings for the frame are both wrong!

What is Ossie anyway?

[kingsteam9]

You're not alone with that one - I've got his De Winton ' Mutatis Mutandis' under construction and found loads of dim errors on it which frustrates me no end as I wanted a 'quick' project! Is there such an animal.

will have a look thro my back ME's and see if I can help.

Robin

[kingsteam9]

Finall dug out my copies of ME, and subsequent issues, but no further info seems to have been published to add missing dimensions as far as I can find. The only clue to piston rod length is on the GA (28th August, P255) which you could take as centre of cylinder length to centre of crankshaft - which from dimensions given is 3 1/2" - 7/8" = 2 5/8"; add to that half the piston thickness at 5/32", gives big end bearing centre to end of piston rod of 2 25/32". That said you'll need to check it against the dimensions of your assembly as built. Hope that sheds a bit of light. The only other suggestion is possibly writing to Stan c/o ME and see if he can fill in the details?

Robin

[districtgrandmaste]

Thanks Robin - I reckoned the rod would be about 2 3/4" - so I've got enough material at least!

The great lesson seems to be - watch out when building because drawings may not the complete nor accurate!

CEW

[dscott]

Dear all,

Its lovely to hear that Stan has carried on the wonderful tradition started by Martin Evans with his drawings and errors. This is such a shame as most of us have only time to make one set of parts in an evening once we have survived the journey home, the meal, the washing up, the change of nappies, and battled with the change of rules in various childrens bedtime books to make them P. C.

To help in my designs I try and get someone else to go over them then I make the parts, and then re-work the drawings, I spent some time last week checking the twin vertical cylindered engine and cylinders on my S.I.M.P. engine.

Anthony Mounts engines are allways well drawn and the design built before publishing.

David.

[kingsteam9]

CEW

'Fraid you're right, and that's probably one of the causes of so many unfinished projects. Just to add to your joy you might want to have a look at the drawings of the piston rod bearing big end) and the crankshaft ME 23rd October '98, P496. Big end is shown as 3/8" thick but dimension between crankshaft webs is shown as 13/64" - methinks should be 13/32".

Like David, I have a high regard for Anthony Mount's work, - lessons there for other designers.

Robin

[steam4ian]

G'day all

I'm just surprised people blindly follow drawings. Surely it can't be that hard to work out the piston length from the other dimensions and allow a bit of clearance.

Regards,
Ian

[districtgrandmaste]

Hi Robin - Last night I made the crankshaft per drawing and thought to myself - that web's very thin/narrow but left it for the loctite to cure.

Today I shall make another crankshaft with a 3/8" gap!

I do tend to follow drawings - afterall that's what they are for - and 'Ossie' is the first time I've had serious irritations!

CEW

[kingsteam9]

CEW

Ah, sorry to hear that! You might not need to make a whole new crankshat tho' because if you heat up your crankshaft assembly the Loctite will soften up enough to allow you to pull it apart - should then just need a new longer crankpin; hopefully you've got a long enough shaft to finish overlength and trim it up later when you can do a trial assembly - if not then a new shaft length as well :-(. I'd still go for the 13/32" gap to allow a little clearance.

Ian,

I agree, but we all place our faith in designers and suppliers to give us good info on drawings and so on - unfortunately some are better than others and it's only by experience that we learn what to watch out for. I was a tyro once - best part of fifty years ago - and it's been a slow learning curve but I don't get caught out as often as I used to.

Robin

[steam4ian]

G'day Robin

Thanks for your pacifying comments ("Blessed are the peacemakers"); I realise mine could have been seen as intemperate. I have in mind to set up a spreadsheet for dimensioning up a engine; put in crank throw, cylinder length, clearance, piston length etc, etc ands get out the missing dimension. maybe a little "over Easter" project.

regards,
Ian

[kingsteam9]

Ian,

Dunno about that but no criticism intended, I assure you. I've a lot of sympathy with others who get caught out like this - I still have a couple of jobs under the bench that I abandoned forty odd years ago because of this sort of problem. Had I been able to talk to others about it at the time I'd probably have completed them; come to that maybe it's time to get 'em out again. That's one of the great benefits of this site - being able to chew over the problems.

Good luck with the spreadsheet, btw, that sounds like an interesting idea. I know that in one of my old 1930's engineering pocket books it gives details for proportioning various parts of a steam engine and would plug into something like Excel.

regards

Robin