Any "Beginners" building 5" gauge Boxhill?

Edited By pcb1962 on 07/10/2011 10:08:58

dennis,

thanks for your post! i had found your youtube clip sometime ago and it's great! you have built a cracking loco!

as mentioned in a few other posts on this subject here and elsewhere the drawing errors seem to be as follows:-

the axlebox and horncheeck drawings are awful.

the boiler is nothing like a fullsize TERRIER and neither are the cab controls (which is such a shame as Stroudley was an artist down to the very last detail). so far as the boiler is concerned, it goes for overkill with the grate area and ends up with quite a low free gas ratio through the tubes. it doesnt have the sort of rectangular firehole that the fullsize has nor the large radius on the backhead flange, and it is extended and slopes down over the rear axle. this is quite unnecessary IMHO, and mine has a full depth firebox sitting within the rear horns as per fullsize. the 1/16" inner wrapper i think is suspect as is the lack of proper girder stays. i dont think the palm stays are up to modern standards either. the lower water gauge bush is too low (there should be 2 water gauges anyway as per prototype). my boiler design has a 5/16" foundation ring all round and a 3/32" inner wrapper and a flat topped inner firebox with girder stays. dont forget the boiler is working pressure 90 psi. my own boiler is 4" dia which fits easily between the frames and the front of the rear horns losing only 1" on the grate area of martin evans' boiler design despite the wider foundation ring, and thicker inner wrapper. i have had to use some quite thin boiler insulation material to just about keep to the correct outside diameter. the dome is moved forward to be in line with the driving wheel centre line for the later Marsh boiler.

although the side elevation is pretty accurate in martin evans' drawing, the front elevation is NOT! for some inexplicable reason he widened the buffer beams and side tanks and cab. the GA side elevation is correct for the shape of the cab roof but as you have noted on sheet 8 the detail of the cab roof is not and is wrong.

depending on how particular you want to be, there are lots of differences from the prototype that add nothing to the miniature ie tank extending into the cab on the r-h side, cab windows too large and in the wrong place, tanks slightly too low etc..

for an original A class TERRIER the smokebox should NOT be circular, and in any event martin evans shows the diameter of the smokebox and smokebox door too small by quite a lot.

unfortunately martin evans also completely cocked up the valvegear which has far too large a throw on the eccentrics. this can be accomodated but only with a longer length expansion link to correct this fault. no suspension offset is shown whereas there should be one for good valve events.

apparently the balance pipe requires additional holes in the frame not shown, though personally i dont see a problem with making the balance pipe as per prototype. i dont like the well tank idea, so mine will have a wagon to go behind for extra water and coal.

i have heard horror stories of the press fit valve spindle glands coming adrift so best to silver solder these in place.

the balance weights on the wheels shouldnt be proud of the wheel tread and should be slightly less. the works diameter of the wheels is 4', so martin evans' 4 3/16" is slightly less than fullsize.

shame about the lack of room for 4 lifting links to the expansion links and the cut away required on the slidebars as this precludes the use of channel section slidebars as per prototype. my TERRIER has the cylinder block moved forward by 1/4" to give a longer conn rod length nearer to prototype. if i hadnt already machined the cylinders and crankaxle to drawing i would make the outer crank webs 1/4" thick and gain a bit more space for the port passages and a larger exhaust passage. i would also make the cylinders as long as the castings would allow to get a bit more piston width as there is ample room at the front for longer cylinders.

the front frame cut out should be the same height as the rear freame cut out and it doesnt take much to fabricate a crosshead pump body to fit the larger cut out. the crosshead pumps are in line with the motion centre line on fullsize, and again it doesnt require much to achieve this in miniature.

the reverser arrangement is nothing like Stroudley's, and can easily be made to be the same in miniature.

as mentioned above Stroudley was an artist when it came to details, and there is no reason whatsoever why the correct arrangement and design of cab controls should not be incorporated in miniature.

one advantage of modelling STEPNEY though is that she hasnt had a westinghouse pump fitted since the 1930's! on mine, the brake cylinder (vacuum on the fullsize STEPNEY) is a steam brake cylinder, and the large reservoir contains a filter and supply from the wagon and acts as a sump to feed the injectors which are rather small but are tried and tested!

martin evans' frame stretchers and motion plate are nothing like the prototype, and in fact the prototype had more frame stretchers that can be with advantage be reproduced in miniature.

Stroudley's design is so beautiful and perfect that it seems such a pity to depart from it in any way! generally, a very successful design in fullsize can be reproduced successfully in miniature without any departure from the original apart from the internals of the boiler, and the salter safety valves etc.

otherwise a lovely design and it is remarkable how so many successful working locos have been built to the BOXHILL drawings!

Hi Julian

You forgot to mention that the top of the of the side tanks should be recessed.

BUT lads, lets not forget that the start of this thread asked ' Any "Beginners" building 5" guage Boxhill ? '

I am fairly new to the "live steam" scene and I as mentioned above am embarking on an Adam's Radial "Combpyne" by Kevin Moonie. They are more recent drawings, and appear pretty good. I have also done a lot of research on that loco and will include some minor visual cahges.

I purchased an almost complete Boxhill to finish and run whilst building the Combpyne. But I, like a lot of enthusiasts out there, do not have the skill to redesign boilers and valve gear.

Julian, I seriously applaud your skills, but I do not want us to put off prospective builders who love the style of these diminutive locos. I have always liked them from being a youngster and find the Martin Evans Boxhill a 'fair' representation. Warts and all.

Happy building

Peter Hothersall

hi peter,

it wasnt my intention to put anyone off building BOXHILL, merely to list some of the design faults for the unwary.

i have never liked martin evans' habit of using the running plate as the bottom of the water tanks as this makes assembly and painting difficult, and the saving in brass is minimal and not worth the extra hassle... so i would recommend anyone to make the tanks as self contained units.

also be very careful with the castings as there is hardly any machining allowance on them.

good luck with completing your own TERRIER and the radial tank!

cheers,

julian

Edited By julian atkins on 22/02/2012 10:35:39

Hi Julian

Your comments about the side tanks got me wondering about the ones on mine. I won't be 100% sure until it is dismantled for painting, but it looks like the original builder had the same idea as yourself and has put a bottom in the tank.

Good idea, and I will also consider this theory for the radial tanks.

Regards

Peter

if you make the tanks as a self contained unit anyone starting from new can make the running boards out of steel plate anyway which saves on brass!

peter,

did you find there is much clearance between the top of the front axle and the bottom of the crosshead on your TERRIER? the axle dia is supposed to be 5/8" all along and i would be interested to know if yours is relieved locally to clear the crossheads.

cheers,

julian

Hi Julian

Good question !

On checking my Terrier, there is no clearence on full axle travel. In fact, because the original builder has pinned the Piston rod to the Crosshead the pin is also fouling the axle. I will have to restrict the axle travel as I think it does not need to so great and do something with the pin. Thanks for the heads up on that one.

This is a photo of the Cylinders and inside motion

Regards

Peter

Peter,

that's a great pic of what appears to be a very well made loco. you could always put the front axle between centres when dismantled for painting and turn the section between the axle boxes down to 1/2" dia.

cheers,

julian

Hi all, a question for you. I am looking at the crank shaft in particular the webs. The build notes call for 1"x5/16" material but all the drawings show 1 3/16" x 5/16" and i cant see a clue as to which is correct. Can anyone help?

Thanks

Bob Thompson

hi bob,

they are 13/16" x 1 7/8" each, 5/16" thick. thats 13/16", not 1  3/16"!

hope that helps!

cheers,

julian

Edited By julian atkins on 08/04/2012 13:10:54

Thanks Julian excellent service

Bob

hi bob,

i have sent you a PM

cheers,

julian

Hi Bob

Just in case it helps, I have included another one of the photos I took whilst my Terrier's unside was visible. This shows the crank in greater detail.

If you click on the picture (or the one above) then it will enlarge full size. You can then right click on the enlarged picture to save it on your pc if you felt it useful.

I always find a picture worth a thousand words. I have more pictures if you want to send me an email.

Regards

Peter

Thanks Peter thats very helpful indeed. As you say pictures always explain so much better than words. I will drop you a line.

Cheers

Bob Thompson

Thought I'd add mine to the thread.

Bought unseen from an auction last year with no history. Well made originally, but very poorly repainted at some point. Boiler needs work so I'm thinking of just getting a new one made up.