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Boxhill by Martin Evans

Driving Wheels

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TED ROGANS23/09/2009 13:49:34
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The drawings for Boxhill in "The Best of Model Engineer" are a copy of the original drawings published in the Model Engineer. Martin Evans made a correction in a later article on the construction. This was that the balance weights  should be finished flush with the tyres. Apart from being true to the prototype this simplifies the turning of the wheels.
 
Unfortunately the drawings were never been corrected.
David Clark 123/09/2009 14:25:12
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3357 forum posts
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10 articles
Hi There
Do you know which issue the correction was in?
regards David
 
TED ROGANS20/10/2009 10:49:54
2 forum posts
Yes, the correction occurred in the very first paragraph of the next issue after instructions for machining the wheels, October 1st 1963. This must have been very frustrating for anyone who had already finished the wheels, after setting up on a face plate or in a chuck  with the chunky balance weight of the Reeves castings sticking out.  I did tell Reeves about this many years ago but no action was taken.  I suppose the plans would have to be updated before they could change their patterns.
 
Peter D Hingley 105/11/2009 14:47:35
3 forum posts
I am sorry  to say that,  in general,  the  quality and accuracy  of  drawings   sold for model engineers   is pretty  abysmal.     One chap I know,  a highly  experienced  model  engineer,   was  busy  building  a   5 inch 'Duchess'  complete with all  4 cylinders,   carefully made and  stored away the   very complex crank   axle and the   coupled  ones ,  then   turned  all the coupled wheels  exactly to drawing,    then  discovered that the   holes in the  wheels   were  bigger than the wheel seats !!   He   wrote to complain   to  the  publishers   of the drawings  who  just said   oh  well,  you are an engineer, you should  have checked !   But surely  if  one has paid   a   sizeable chunk of money  ( and a full set  of drawings for a large  and  complex loco costs a very tidy  sum)  one has a right to expect that  they will be accurate and   that  any errors   have been corrected.   A draughtsman who made that sort of  error in industry    would be sacked and  quite rightly too. 
 
But  I am afraid   this is a   very similar situation  to kits  made for  smaller scale  modelling   such as 0  gauge.     These vary   from absolutely  wonderful  (such as  Martin  Finney and David  Andrews) to the  abysmal and  virtually   unbuildable.   Consumer legisation   offers   little   realistic redress and  one's only  recourse is to  rely on  reviews and      other peoples'   knowledge and   experience, and for   that this  kind   of forum is  invaluable !  
                                                Peter D Hingley 
Andrew Loubser23/04/2011 10:28:17
2 forum posts
I am currently constructing Boxhill as per the plans provided but to 71/4 inch gauge. The placement of the two oval openings in the frames in relation to the wheels is not evident e.g. no measurements to indicate how far from the front or rear wheel centreline it is.
I am pleased with this model chosen by Model Engineer to provide the plans for as in our club we have open days steaming and take passengers for rides. This model shows every promise to pull exceedingly well.
 

Edited By Andrew Loubser on 23/04/2011 10:29:07

Weary23/04/2011 11:35:55
421 forum posts
1 photos
I guess that you know that Don Young designed and described a 7.25" gauge IOW Terrier 'Newport'. I assume that the cut-outs are standard amongst the class.
 
I have checked the Don Young drawings (sheet 3, illustrated Locomotives Large and Small No.52, August 1992) and these seem to be the relevant details as drawn by Don.....
Both the cut-outs shown as 1 7/16" (one and seven sixteenths) high, and rounded to that diameter at each end. The radius centre to radius center of the end radii of the front -cut-out is 2 3/8" (two and three eighths), that of the rear cut-out is 3 5/8" (three and five eighths).
The bottom edge of both cut-outs is 5/8" (five eighths) above the frame edge immediately below the cut-outs.
The center of the radii nearest the center wheels of the two cut-outs are 2 13/16" (two and thirteen sixteenths) from the centre-line of the middle axle.
 
Hopefully some of that fits with the 'Evans' drawings.
 
There also seems to be a round openings to the rear of the rear axle, but I guess Mr Evans has specified that position. Don makes that 1 7/16" (one and seven sixteenths) diameter too.
 
Regards,
 
Phil

Edited By Weary on 23/04/2011 11:41:32

Andrew Loubser23/04/2011 21:46:34
2 forum posts
Phil
Thank you for the prompt reply. The info is spot on. Any information is valuable especially drawings to collate.
My Club is the Western Province Live Steamers in Cape Town South Africa. W've just hosted the National Steam Meet for four days and was it a blast!
Weary23/04/2011 22:36:25
421 forum posts
1 photos
Reeves 2000 can supply the drawings and castings for the Don  Young 7.25" gauge 'Newport'.
 
Mr Loubser, please check your messages.

Edited By Weary on 23/04/2011 22:44:04

John Olsen24/04/2011 05:59:48
1294 forum posts
108 photos
1 articles
Well, how about a section here for some of the more popular models, where errors and improvements can be described. This does not of course help the guy who does not have Internet access, but it would help with what is otherwise a very difficult problem, which is getting a correction out to all the people who might need it. Even if a correction gets published in the magazine, there is no certainty that the future builder will find it, and with printed set of plans, I suspect once a print run has been done, that will be used until they run out.
 
But if the prospective builder knew that they might find some useful information here, it could save a lot of wasted effort.
 
regards
John
Colin Jacobs 129/04/2011 20:01:42
69 forum posts
2 photos
This could even make a magazine page?
John Olsen30/04/2011 01:15:45
1294 forum posts
108 photos
1 articles
The trouble with a magazine page is that you may not have that particular page available a few years later when you buy a set of plans and set out to build a model. Websites can of course disapear too, but useful information seems to have a habit of staying available.
 
regards
John
Weary30/04/2011 09:20:48
421 forum posts
1 photos
For those unaware of it, this site might be of interest as it lists many errors.
Alan Stewart 201/05/2011 17:58:34
3 forum posts
The real problem with Boxhill wheel castings is, I think, that the weights are 90° out of place. Cranked wheels for small locos have the counter weights at right angles to the coupling pin. The coupling pins are opposite the nearest crank and the weight is opposite the far crank hence putting the weight at 90° to the coupling pin. Box Hill weights are opposite the coupling pins! I suppose the recommendation to machined the weights flush with the wheels is to reduce the out of balance effect that I think the weights will produce. I have already resolved to leave the weights protruding (as I think they would not look good flush) but to drill a few holes in them and add balance weights
Alan Stewart 204/05/2011 15:57:43
3 forum posts
Alan Stewart 204/05/2011 16:03:46
3 forum posts
Looking at the cranked wheels of GW engine 6412, the balance weights on the cranked wheels are at about 60° rather than 90° to the coupling pin so I now think they are for balancing the eccentrics which are between the cranks.
julian atkins13/06/2011 09:19:36
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1285 forum posts
353 photos
Stroudley had his own pet ideas about balancing cranks, and position of crankpins vis-a vis the crank axle... the balance weights were large and crescent shaped and at 180 degrees to the crank axle webs. the crankpins were in the same position and in line with the crank axle webs/connecting rod pins for each side of the engine. martin evans explains this on p. 360 ME 15th sept 1963, and there is no error in his drawings for the wheels, apart from the fact that to be true to prototype the balance weights are flush with the spokes which as already commented upon he corrected in a later article. it would be quite wrong to follow the 'usual' arrangement of balance weights and their position relative to the crankpins and crank axle on a Stroudley engine!
a close examination of photographs of Terriers will confirm this.
hope this helps.
julian atkins13/06/2011 09:50:53
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1285 forum posts
353 photos
by the way, martin evans did take liberties with the buffer beam and running board width to accomodate wider side tanks than prototype, and of course the tanks never protruded into the cab as per one side of BOXHILL. anyone building a model of engines post 1905 needs to check if it was one of the locos fitted for motor train working because these had their buffers raised (see pics of Stepney etc..). A class Terriers should not have a round smokebox as described by martin evans, and the boilers of the prototypes were quite different with the rear of the boiler being shorter and not sitting above the rear axle, and with a large radius to the backhead flange and a completely different arrangement of controls and firehole ring and door 9what an awful backhead he designed when compared to Stroudley's artistic design!).
the smokebox diameter and smokebox door diameter should also be larger by 1/4".
there are other detail differences between martin evan's drawings and the fullsize locos...the rear drawbar should extend forward as far as the rear axlebox, and martin evans did comment on the use of 'channel' shaped slidebars in his description. the axleboxes had a high lip on their outside face to prevent grit and dirt getting into the axleboxes from the wheels, and of course the prototype engines all had underhung leaf springs which isnt difficult to do in miniature.
you will gather from the above that martin evan's side elevation is very accurate to prototype at 1 1/16" scale, but the end elevations are not! i have a copy of the original Stroudley general arrangement drawing from Engineer magazine in 1873. don young's 7 1/4" gauge design NEWPORT is far more accurate to prototype.
Dennis Rayner13/06/2011 13:23:51
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137 forum posts
9 photos

"martin evan's side elevation is very accurate to prototype at 1 1/16" scale, but the end elevations are not!"
 
Nowhere more so than the cab roof which is totally wrong. From the end elevation the cab roof should follow a continuous arc but the Martin Evans drawing shows it as being flat.
 
So many wonderfully lined out models are spoilt by this massive error.
julian atkins24/06/2011 13:20:41
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1285 forum posts
353 photos
Dennis is quite correct about the cab roof... sheet 8 of the drawings shows the shape of the cab for the side elevation as the front elevation! a typical martin evan's error, though to be fair to him the general arrangement drawing on sheet 1 does show the correct front elevation curve to the very distinctive Stroudley cab roof.
 
i would be very interested if anyone has the details of a Gordon Smith type safety valve suitable for Boxhill please?

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