darjeeling locomotive

[peter ravenscroftParticipant @peterravenscroft57700]

hello

        i am building the new darjeeling loco and have just started the rear beam are the drawings correct ? or are they a copy of the front beam ‘

if you scale the drawing up to the correct size you will find that the beam is 2″ deep any comments or is this an error (posibily due to the editor’s demise get well soon)  

regards

peter

 

 

 

[peter ravenscroftParticipant @peterravenscroft57700]

latest drawings

[JasonBModerator @jasonb]

Well that would match the dimensions, 1 1/2″ verticals plus two 1/4″ thick plates.

 

Front Beam is dimensioned smaller at 1 3/8″ plus twice 1/4″

 

Jason

Edited By JasonB on 03/07/2010 15:56:44

Edited By JasonB on 03/07/2010 16:11:25

[peter ravenscroftParticipant @peterravenscroft57700]

thats the vetical measument the beams are supposed to be made from 1 1/2 x1/4 material but if yuo measue the rear one you will find it is 2″ with 3/8 x1/2 front spacer and 3/4×3/8 rear spacer

regards

peter

[JasonBModerator @jasonb]

Ah Got you now, you are talking about the plan view from inner face to teh outside of the curve which is dimensioned 1 1/2″ but the 3/4″ spacer looks a lot less than half that dimension,

 

So yes there is either a wrong dimension or its drawn out of scale/proportion, I would go with the former.

 

One would have expected it to be 1 7/8″ by the addition of an extra 3/8″ to the spacers but it scales at over 2″ but then again I do feel that the drawings are sometimes compressed to get them to fit the mag layout

 

Jason

Edited By JasonB on 03/07/2010 18:44:55

[peter ravenscroftParticipant @peterravenscroft57700]

thanks Jason

 i thought it was me not reading the drawings correctly i have the works drawings but it does not show this beam so i think i’ll go with 2″ i think the dimension should be 2 1/16 o/a no doubt time will tell

regards

peter

[Donald MitchellParticipant @donaldmitchell68891]

I have been authorised by my good friend Raymond McMahon to clarify the point raised by Peter Ravenscroft in regard to the apparent mistake in the drawings about the rear buffer beam.

 

Raymond does not use the internet, I am in constant conversation with him and can clarify any points raised.

 

On page 18 of M.E. issue 4381 at the top right hand side of the drawing there is a vertical measurement shown as 1.5″ (the back to front o/a measurement of the beam)

 

This 1.5″ dimension was not drawn by Raymond on the original plans and should not be there, it has been added (obviously in good faith) by someone at M.E. who assumed the dimension was missing and that it would be the same size as the front one, but its not !

 

Peter has correctly sussed out that the back to front measurement of the beam should be 2.1/16 o/a

 

I hope this clarifies the point for all.

 

Regards.

 

Donald Mitchell

Castle Douglas
Bonnie Scotland

[peter ravenscroftParticipant @peterravenscroft57700]

many thanks donald

i have made the beam this morning and it has worked out ok

please thank raymond for me it’s a loco i have always wanted i started to buid one in 5″ gauge but it was turning out too big for me to transport i still have all the bits for the 5″ and maybe i’ll photo the 2 together

regards

peter

[Donald MitchellParticipant @donaldmitchell68891]

Hi, Peter Ravenscroft, I have sent you a personal message.

 

Donald Mitchell
Castle Douglas
Bonnie Scotland

[DustyParticipant @dusty]

Hi to all who are building this Loco.

   Just a reminder to those of you who are using 3mm plate for the frames to compensate for the slight difference in thickness from 1/8″ plate. If you make the front beams and the angle which joins front and rear frames together 15thou wider and also the axleboxes 7thou narrower where they fit through the frames, you could save a lot of heartache later remembering to make compensation in valve gear components, fly cranks, cylinder bolting faces etc etc etc. No, I have not started building yet, another project to finish first, Then I will start. You may not think that such a small difference can affect the loco, I can assure you it can, having built a narrow gauge o/s frame loco I speak from experience. From what I have seen it appears that leaving the rear frames as the are will not matter, allwats remembering to adjust the joing braket fabrication.

[Dave HarrisParticipant @daveharris36943]

Having just read the latest installment for the ‘Indian Steam locomotive’ I am somewhat concerned about drawing being provided ie

 

Wheel section drawing: measurments given – 9/16” overall thick but then we are given a tread width of 3’8” and a tyre width of 5/32” which do not add up to 9/16” ?

 

Axle drawings show the outer parts which i assume are machined to accept the wheel as 0.531” for the rear axle and then 0.468” for the front axle? i would have assumed that the front and back wheels would be of the same thickness as no differencew is shown on the wheel profile drawing mentioned above?

 

Also, why do we have some measurements in imperial and some in decimal, surely we should have all measurements to one ‘system’?

 

A confused novice???

[JasonBModerator @jasonb]

The wheels do not mount onto the 0.531″ & 0.468″ long ends of the axle, if they did the fit would be a bit loose as they are bored 5/8″

 

Look at the photos, wheels are inboard of the bearings

 

As for the missing 1/32″ on the wheel drawing it could be the flange is 5/32″ with a 1/32″ radius at the base of teh flange where it flows into the tyre, I’m not enough into locos to be sure of this but you should be able to find the details in any table of wheel standards.

 

Jason

Edited By JasonB on 29/07/2010 19:34:19

Edited By JasonB on 29/07/2010 19:51:37

[Dave HarrisParticipant @daveharris36943]

Thanks for the comment re the fit of the wheels on the axles, i will try reading 3 times before i put fingers to keyboard!  However my comments about mixing decimal and imperial measurements still stand for a response from the editor; and regarding wheel standards, where does one find those, and perhaps the editor could confirm your assumption?

[JasonBModerator @jasonb]

No I can’t see why the dims are fraction & decimal, the only time I would expect it is if the size is not a fractional one and therefor has to be given in decimal. Decimals are sometimes used on fraction drawings where a size is more critical but that does not seem the case here.

 

If you read the first few lines about the axles you will see why the lengths are different.

 

Still it could be worse, the Rena gear drawings have no sizes for the hole on the smaller gear and don’t even have a hole shown on the larger one!!. David perhaps you could ammend this as I think you are redrawing this?

 

Most of the ME books such as Model Engineers Handbook give wheel standards, as I say I’m not into locos so can’t give you a decent explaination.

 

Jason

[KWILParticipant @kwil]

There used to be a convention that if given in decimals the tolerance was tighter than fractional, however as most MEs work to “fits” this does not necessarily arise. When did you last see a tolerance stated on a ME drawing?

[Ian S CParticipant @iansc]

Hi, I think the normal is that if a dimention is in fractions, use a rule, and if in decimals use a micrometer. ie., 1 1/2″ say +/- say.005″-.010″ or as good as your eyes will allow, Decimal, for rough working I use +/- .002″ but usually much closer, unless the fit is specified, then work to that.Ian S C

[peter ravenscroftParticipant @peterravenscroft57700]

i have just read the latest posts with interest because i think there is an error.

 in the write up it says that the rear axle is smaller to accommidate the pump eccentrics but in the drawings it shows it the other way round which is the right one as progress is now stopped

regards peter

[JasonBModerator @jasonb]

You must have a different magazine to me as the rear axle is shown at 0.718″ and the front at 3/4″ . I’ve always found 0.718″ to be smaller than 0.750″

 

The rear axle is LONGER but thats is to suit the cranks and is clearly stated in the first few lines of the axle description as I mentioned above

 

Jason

Edited By JasonB on 30/07/2010 16:49:28

[David Clark 13Participant @davidclark13]

Hi There

Rina gears

I believe the gears are standard gears.

However, as the small gear is fitted to the crankshaft, I suggest that 3/8in. diameter would be a suitable bore size for this.

As the large gear fits on the cam mounting shaft, a running fit on 1/4in. diameter might be suitable.

I did not have time to redraw this so the illustrator did it from the information on the original drawing.

 

regards David

[DustyParticipant @dusty]

I have looked at the axle drawing and am of the opinion that the wheel back to back dimension is wrong. These are my reasons; The axle is 3 and 3/16ths for the back to back dimension added to this is the width of the flange x 2 =5/16 added to the previous 3 3/16 = 3 1/2″.

 this is far to tight for a normal track let alone one where the gauge may be a little tight. The effect of this would be to cause the wheels to climb the track thereby derailing the loco this would be very evident on curves. The dimension should be, in my humble opinion no more the 3 1/8 for the back to back dimension.

 It would also improve running if the wheels were coned by about 2 degrees, this would help centralise the loco on the track. I am ready to be shot down in flames.

[David Clark 13Participant @davidclark13]

Hi There

Yes, that 1 1/2 should not be there.

I expect the illustrator left it in from doing the front beam.

Usually I catch these errors but I only came out of hospital Thursday night and went to press Friday so missed it.

 

We would not change dimension from imperial to metric or vice versa.

Although we make every effort to ensure everything is correct, occaisonally things will slip through.

I found this post by accident. If anyone spots an error, please email me so I can print a correction.

regards David

 

 

Edited By David Clark 1 on 30/07/2010 18:52:20

[peter ravenscroftParticipant @peterravenscroft57700]

oops thats what you get for reading it on the bus on the way home

you are corect it is 0.718 not 7/8ths as i presumed

regards

peter

[KWILParticipant @kwil]

Ian S C is “correct” if it is given in 1/32 then +/- 1/32 is OK,  as per his rule measurement, if in decimals, you takes your choice of how well you can work, 4th place on a DRO!

[Dave HarrisParticipant @daveharris36943]

Thanks to all who have responded as above.

 

I have located and read the standards information in the Model Engineers Handbook and this agrees with all the construction books produced by LBSC and indeed the Loco Construction book by Martin Evans ie that the back to back dimension for wheels of 3 and 1/2” gauge locos should be 3 and 9/32”, or 83mm.

 

Can the editor please explain the different ‘back to back’ dimension given on the drawing in ‘ME’?

 

Also, i am concerned that it seems to be acceptable to ‘mix’ dimension standards on drawings? My mentors tell me that drawings should be drawn to one standard, and whilst in this day and age there is obvious ‘discussion’ over which ‘standard’ to use…imperial, decimal, or metric; that all drawings for a project should be to ONE standard.

 

Would the editor like to comment / explain why what would appear to be accepted standards seem to have been ignored for this construction series drawings?

[DustyParticipant @dusty]

re Dave Harris’s post

     Wheel standards do not apply to narrow gauge loco’s. You must read the back to back dimension in conjunction with the flange dimension. Flange dimensions on narrow gauge loco’s are far more substantial than main line loco’s. If Martin Evans standard were to be applied to this loco the wheels would run on the flanges if run on a standard 3 1/2 gauge track. This would give an inside flange dimension of 3 19/32″ patently 3/32″ wider than the track. Hope this explains your query Dave. (yes I know I am not the Editor)

 

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