Tender journal scrapping size questions

I have some questions in relation to scrapping size of tender wheel axle journals; if you've never been invovled in wheels & axles, then look away now.

In essence it is this:

For those of you who are familiar with the LMS limits and fits book, sheet W5 for straight axles gives journal diameter (LM) tolerance as +0, -0.0025 for shafts between 4.73 - 7.09" diameter - per table G9. So say for a nominal 5 1/2" dia journal, you can go down to 5.498" dia before you have to do something about the wear.

-2.5 thou seems to be on the 'tight' side, when one considers the wear and light pitting that will be present on a Barry loco where the 'boxes have been left open to the elements, and doesn't leave much room for maneuver when trying to clean up journals for future use.

Is my interpretation correct, or do people have experience of taking a clean up cut greater than 2.5 thou to clean up a journal?

What stops one from just picking a new nominal diameter (for all six journals on the tender) thus effectively starting your tolerances from a clean sheet?

Are there nominal sizes or other journal tolerances in accepted use elsewhere?

Are there alternatives to making a new axle, i.e. by sleeving the journal? (feels like a bad idea).

Thanks in advance.
James

 

I hate to ask, but are you reading this right? I don't have the necessary books so can't say, but a reduction in diameter of 0.005" doesn't sound a lot. On a 5 1/2" journal it represents a loss of cross-sectional area of only 0.0332 sq ins. I don't think they were made that close to maximum loading when new!

Are you sure it isn't 0.25"?

 

Well I think so. All the dims in the Lims & fits book to my knowledge are in thous.

Here are the relevant pages:

 

Right, I think I've got it. These are the maximum and minimum clearances of shafts or axles in their bearings. For example, let's take the 4.73" to 7.09" journal. For a nominal size, it can be between 0.000" and 0.0025" below that size, i.e. +0.000" to -0.0025". The bearing can be from 0.0035" to 0.0075" larger in diameter than the shaft, so the clearance is from 0.0035" to 0.010" (largest size axle in smallest bearing (0.000" in + 0.0035" = 0.0035") to give a clearance, or smallest shaft in largest bearing (-0.0025" in +0.0075" = 0.010"). If the journal wears beyond 0.0025" below a given dimension, it is turned down to the next available underside, and the bearing is remetalled and machined to the same tolerances relative to the new bearing size.

Hope that makes sense. I know what I mean, anyway...

 

That is correct LMS2968, and your description does make sense!

James - those are tolerance tables and not scrapping tables.

Keith

 

So how do I get to the scrapping size then?

 

I don't know for certain, but I imagine there is a maximum amount of whitemetal that can be added to a bearing to compensate for wear in the axle. Once you reach that maximum amount then the axle is scrap next time around as you can't compensate for any more wear.

Keith

 

You also need to consider the cross-sectional area of the axle; as the journal is turned down to compensate for wear or damage, so this and the strength of the axle reduces. This could lead to the point where it cannot withstand the shear forces imposed by the vehicle's weight and snaps. So a practical limit emerges.

Also, the pressure on the bearing surface increases as the axle diameter reduces (pressure = force / area), leading to loadings in excess of what the bearing can carry, and an increase in the tendency to run hot.

 

Ok, thanks for this debate and comments guys.

Whilst a theoretical minimum journal dia can be calculated (I suspect this will be relatively small for a lightly loaded tender axle), the railways must have had guideline amounts written down somewhere. This I guess is what I need to find before making a decision. If anybody has anything, I'd be glad to hear from you.

Thanks
James

 

What the railways would have done when they had large workshops will probably not be relevant to today. You could recover an axle by turning down and shrinking on a sleeve, and then finish turning it to standard size, or metal spraying could be an option. I don't know whether the railways would have turned them down and used non-standard bearings or just knock out a new one. I suspect they might have turned them down a couple of times, by an 1/8" or so each time and used a non standard white metal brass. With an axle of this size (>20square inches) I don't think shear failure is in the equation.

Rob

 

OK, so if I may put this in another way then; Does anybody have any experience of sleeving or metal spraying that they'd be prepared to share here? I don't particualrly like the idea of either, but I also don't like the thought of making a new axle. I had always assumed that 'thermal' processes on axles were not permitted, but perhaps metal spraying does not raise significant issues.

I had a recollection of seeing something in one of the comics years ago which had an article on Bellorophon (?) which mentioned that it had had journals improved by metal spraying.

 

Is there no journal (sleeve) pressed on the axle?? I'm sure some railways did this. Is there any markings on the end ox the axle?

Stephen

 

mcjlf1 what type of tender are you talking about. Is it one of the fowler type?

 

Yes.

 

My photocopy of the BR/LMR scrapping limits is a bit poor and this particular section is difficult to read but the scrapping limit for tender axles appears to be 0.625" reduction on new dia. I can't read the accompanying note, though. It doesn't relate to any particular diameter. 'Obsolescent' loco tender journals were allowed to be reduced by 0.75". The same figures applied to bogie and pony axles. Repair (re-machining) was required when ovality/taper reached 0.020".

Edit: I've now managed to decipher the note, which states that the root radius should be kept as large as possible but to avoid scrapping an axle it may be reduced to 0.25"

HTH.

Steve

 

That seems a pretty cmprehensive reply!

 

Oh that's interesting Steve - thanks for posting - any chance you could scan that particular page and let me have copy? (or even a scan of the whole thing?!). I'd be very greatful, as hopefully this may allow me to proceed to sort out the wheelsets. [I'm talking here about the tender for 4F no. 4123 by the way, so yes it's a Fowler type - sorry for previous brief response - was pushed for time and tired... no animosity intended.]. Oh yeah - all I need to do now is establish what the new size is supposed to be for a Fowler tender...

 

I've scanned the two pages but they reflect the quality of the original! The document is entitled 'Repair Limits & Scrapping Sizes' and has a revision date of May 1964 and originated with the CMEE Derby. You'll note that by this time 4F's were regarded as obsolescent!

 

Thanks to all for the information. Scrapping limits particularlly useful. But.... I can't seem to find the 'new' diameter of the journal anywhere. It must be on a drawing somewhere, but I can't locate it. If anybody can shed any light on the 'new' new diameter of a Fowler tender journal I'd be very pleased to hear from you...I hoping not to have to make a new axle.

Thanks
James

 

From LMS LOCOMOTIVE PROFILES No 2 - The Horwich Moguls by Davbid Hunt, Bob Essery and Fred James, Wild Swan, 2000 ISBN 1 874103 56 9. This is just a small part.