darjeeling locomotive

[David Clark 13Participant @davidclark13]

Ray does say he has used different wheel standards in the article.

regards David

 

[Dave HarrisParticipant @daveharris36943]

Thankyou for the responses. i regret to say I cannot understand the logic of using ‘different standards’ for NG locosas surely this is one area where the loco has to conform to track standards and not expect the track to conform to the loco? My other questions seem to have been ignored re drawing standards. i will retire from this forum, very confused and dissapointed!

[John Stevenson 1Participant @johnstevenson1]

Posted by Dave Harris on 31/07/2010 22:11:52:

 My other questions seem to have been ignored re drawing standards. i will retire from this forum, very confused and dissapointed!

 Sorry ??

 

Is it that the drawings are so messed up that you cannot understand them [ I have not seen them ] or is it that you expect every drawing to be of a standard even though they may have been prepared by  someone more used to making things than drawing things ?

 

If the first then I can understand your concern.

 

If the latter then, no don’t bother – forget it…….

 

John S.

[Dave HarrisParticipant @daveharris36943]

John,

 

   It a combination of both your observations.

 

   I do expect drawings produced for publication to be correct as far as dimensions are concerned, and to mix standards I feel is wrong as I said in one of my earlier posts.

 

   I am also puzzled by David Clarke’s reply that ‘different standards’ are being used for this loco. I feel the standards in the Model Engineers Handbook are well known and should be adhered to for everybody’s sake as tracks have been made to those standards for many years. Dusty’s reply leaves me very confused, as, if the loco cannot be run on ‘standard’ 3 and 1/2 inch gauge track, then where can it be run?

 

   If the answer is to modify to suit current track standards then I feel that the series should have had this explained at the very start, especially for the benefit of ‘beginners’ like myself who, rightly or wrongly, expect the articles to be correct, and provide the means to complete a workable model,minor typos excepted.

[JasonBModerator @jasonb]

Well I thought that both Kwil and myself gave an answer as to why decimals may be used although it does not ap[ply in this case.

 

Its a bit much to expect the editor to spend his Saturday and Sunday reading through every post as I’m sure he does not get paid for it, perhaps wait until the beginning of the week to see if he replies. And also have a look back through some of the older posts as the same point has been raised several times in the past and I expect you will find your answer there.

 

Lets just be happy that people are willing to provide these drawings, Asd long as there are no errors I’m happy to work in any measurement or mixture

 

I would think that a narrow gauge loco by its very nature is somewhat top heavy and short wheelbased so thats why adjustments need to be made and they often also ran on tracks with a much smaller turning radius so a bit more “play” between the flange and the track is required if they are not to jam on the rails.

 

The Author also says its is “not unusual” for a narrow gauge loco to to use thicker flanges, so its not just a different standard being used on this loco

 

Jason

Edited By JasonB on 01/08/2010 08:35:05

Edited By JasonB on 01/08/2010 08:40:52

[StirlingSingleParticipant @stirlingsingle]

Hello,

 

Are the cylinders on this loco going to use Conway Castings and wheels?

 

Many thanks,

 

Stirling Single

[steve milnerParticipant @stevemilner53244]

Hi sterling Single,

 

Cylinders are new castings to new patterns going to be available from Blackgates Engineering. Or you can machine from solid.

 

Wheels again available from Blackgates Engineering as existing ‘Conway’ castings but again can be manufactured from solid.

 

Hope this helps,

 

Steve

[DustyParticipant @dusty]

Dave

       I am sorry if my reply confused you. What you must remember is that this Loco is scaled at roughly 1 3/4″ to the foot. The wheel standards you are quoting apply to locomotives that are scaled at 3/4″ to the foot. My current Loco is a 3 1/2 N.G. Loco. My wheel back to back dimension is 3 5/32″, the flange is 1/8″ wide, simple maths show that this gives a dimension of 3 13/32. A whole 3/32″ narrower than the nominal 3 1/2″ gauge track. I did not say as designed this loco would not run on 3 1/2″ track, but there is a real danger that it would have a propensity to de-rail. I think that when I get round to building I will reduce the width of the flange to 1/8″ this would in someway overcome the potential problem I have highlighted, without the need to completely redesign the axles. I dont know how Ray has got on with his loco, a lot depends on the accuracy of the gauging of his track.

[Dave HarrisParticipant @daveharris36943]

Dusty,

 

   Thankyou for your clarrification.

 

   I have to say that I ran the discussion re this loco past some other model engineers and their reaction was that they would have used the ‘standard’ as per the model engineers handbook for the wheel profile, although one did say that if he were to do what your most recent post in fact has said, then he would have made it clear that some modification to the ‘normal standards’ would be necessary for the benefit of the less experienced. The ‘fog’ is gradually clearing!

[DustyParticipant @dusty]

Dave

       I forgot to say that the wheels of my Loco are in fact 43/64 wide, even wider than Darjeeling Loco

[KWILParticipant @kwil]

Looking at our club standards, the flange width for 3 1/2″ NG is 0.090″, it is the tyre width that is much bigger on NG, 0.520 cf 0.370. The was a very comprehensive series of articles in EIM starting Jan 1994 which dealt with all the detail of guages, flange depths etc aimed at preventing conflicts arising.

[Chris BParticipant @chrisb73862]

I would have thought with 3 1/2″ the back to back would not be particularly critical for raised tracks as flangeways and check rails do not seem to feature on this type of track.

The problem area would be where ever 3 1/2″ is “on the ground” and has points to negotioate.

In 7 1/4″ there are std (6 13/16″ back to back) and narrow (6 3/4″) wheel standards but the track standard will accomodate both as the flangeway width and check gauge are big enough to accomodate the larger flange width. Although I found at my local club one particular point had been built particularly tight and I had to increase the back to back on the slate waggon I have just finished by 15 thou to stop it trapping the flanges and riding up.

Edited By Chris B on 02/08/2010 12:24:28

[Dave HarrisParticipant @daveharris36943]

I am reading the responses with great interest and some confusion.

 

I am told by by other model engineers that even if one is building a ‘NG’ loco such as ‘Conway’ or the Dargeeling loco the back to back standard for 3 and 1/2inches still applies and that any machining of the wheel to a given size should not result in sacrificing the back to back dimension on the axle.

I note that the Conway wheels which are suggested for use in this instance are 1/4inch larger in thier tread diameter, and are 5/8” thick, which would allow them to be machined back to the dimensions shown in the drawing for the ‘Dargeeling’ wheels  –  what I do not understand from all the previous posts is why the back to back measurement needs to be different to the already defined measurement given in the standards in the ‘Model Engineers handbook’ and as ‘Dusty’ has said, if left as per the drawing in ME, will give rise to a loco likely to derail. Surely if there are ‘standards’ for each gauge then whatever type of loco one is building to whatever gauge then the wheel treads and back to back measurements have to conform to the track standard?

I agree with Chris B that the main time this difference will show is on ground level tracks with multiple gauges and therefore using points. This may not seem to matter too much but it does mean that the standards set for our tracks, albeit a small minority of tracks, are being ignored for want of a better way of putting it and I still cannot understand why this has to be when it doesnt happen if building locos like ‘Conway’ or the smallest gauge version of ‘Sweet Pea’?

[Donald MitchellParticipant @donaldmitchell68891]

Hi engineers,

 

I have been watching this thread about the wheel back to back size with growing interest.

 

Raymond McMahon is presently away from home on holiday; he will be returning on Tuesday 10th. Aug; and will no doubt clear up this dilema via this keyboard as soon as possible thereafter.

 

Raymond does not use the Internet himself.

 

Donald Mitchell

Castle Douglas
Bonnie Scotland

[DustyParticipant @dusty]

I am afraid that a lot of you seem to be missing the point. In effect the back to back dimension means nothing, it is the thickness of the flange and the measurment over the flanges that is important. This measurement has to be less than 3 1/2″ by, I would say 1/16″. This is to allow the loco to run on the tread of the wheel as oposed to tight on the flanges. The larger the radius between the flange and the tread then the nominal 1/16″ needs to be larger. In essence the thicker the flanges the smaller the back to back dimension needs to be.

 Playing the devils addvocate, if for instance we had a back to back dimension as per Martin Evans of 3 9/32″ and flanges of 5/32″ The loco would not sit on the track. I am afraid I cannot advance this any further. Everything in life is a comprimise especially Model Engineering.

[Dave HarrisParticipant @daveharris36943]

Dusty,

 

I am sorry but I do not understand your logic.

 

If one takes a ‘Speedy’ wheel as an example, the overall thickness of the wheel is 9/16”, as for the Dargeeling wheel, the thickness of the flange is 3/32” and the tread is 3/8” and this allows for the 5” gauge back to back measurement.I cannot see why with the same overall wheel thickness it is not possible to adhere to the 3 and 1/2” standards already quoted.

[JasonBModerator @jasonb]

Because the 3 1/2″ has no the flange is 5/32″. on the 3 1/2″ drawings

 

3 3/16″ back to back plus (2x 5/32″) = 3 1/2″

 

Jason

[Dave HarrisParticipant @daveharris36943]

JasonB,

 

            Thank you, having re – read all the forgoing, and re – studied the diagram regarding the back to back/wheel profiles in the article re track and wheel standards in the ME handbook, and your comment above, I now understand the dimensions. I had a fixation over the back to back dimension and was not taking into account the flange dimension! My apologies to all for being so ‘thick’!

 

Dave

[David Clark 13Participant @davidclark13]

Hi There

I only edit the articles, I don’t rewrite them.

Also, some methods used by authors I would not use if building it myself. That does not mean they are the incorrect method. If Ray decides to change recognised standards, that is his decision.

 

If I start changing anything then I would probably introduce major errors.

All I can do with any article is edit it for grammar if needed and ensure all is in the correct order.

regards David

[DustyParticipant @dusty]

Having just read the latest instalment of this series I have noticed that the drawing for the main spring shows the thickness as 0.78. Ray says that it is masive and would be rigid in the model, that is an understatement. By my calculation the thickness of this spring should be 0.054. How did I arrive at that, The spring on the original is 3/8″ or .375, if you use a divisor of 6.85 this will give you 0.054. Why 6.85, this is arrived at by dividing 24″ (the gauge of the original loco) by 3 1/2″ (the gauge of the model). By the way the remaining springs in the stack are 5/16″ thick or 0.045 in model terms.

[JasonBModerator @jasonb]

Just looking at the proportions of the rest of that part its obvious the thickness should be 0.078″, look like someone left a 0 out.

 

Jason

[DustyParticipant @dusty]

Jason

          I do not agree, my sizes have come from the works drawing which shows 3/8″ thick by 3″ wide for this spring. This makes the model spring 0.054 thick by 7/16 wide. The drawing in M.E. is 7/16 wide but .78 thick. This would then make the full size spring 17/32″ thick if the dimension should be 0.078 on the model. I doubt that they would have made the spring such a bastard size, especially with a stack of leaves underneath it.

If you look at album 5 of David Clarkes photo’s a very good view of the springs is available the top leaf is not massivly thicker than the lower leaves, this I think supports my argument.

Edited By Dusty on 27/08/2010 16:41:23

[JasonBModerator @jasonb]

As the spring on the model is infact a “beam” that supports a coil spring (thats how I read it) then I assume the maker has made this one stronger as all the other leaves are just dummies. If it were scale size without the other 15 leaves to add support it would likely flex and risk going curve up

 

If you are going to make working springs then yes the thinner size would be better. But as they are dummies there is likely to be a reason teh top load bearing one is thicker

 

Jason

[DustyParticipant @dusty]

Hi Jason

     Yes that would be sensible. I must admit that I had not thought along those lines. Bit of tunnel vision on my part I fear.

[peter ravenscroftParticipant @peterravenscroft57700]

hello

       has anybody fitted the cylinder mounting plates yet as i am having problems i have marked everything out ok and have checked it all but the plates seem to foul the tank mounting brackets

any idea’s

tia

regards

peter

 

[Author]

Posts