jma1009
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Post by jma1009 on Jun 28, 2011 10:11:49 GMT
i am building a 5"g TERRIER, a miniature version of A1X STEPNEY on the Bluebell Railway as preserved. i am very well acquainted with the full size locos, and have quite a file of info on STEPNEY and her sisters plus quite a few books. ive got the Martin Evans BOXHILL drawings plus the ME's for the period, plus Don Young's drawings and description for his 7 1/4"g NEWPORT from LLAS.
i have made the cylinders and buffer beams and crank axle etc.. and intend to build the loco as near scale as possible and fit a shorter firebox to clear the rear axle as per prototype, and a few other bits and bobs to my own way of doing things.
anyway questions...
1. Is 3 3/4" dia drawn copper tube still available for the boiler, or am i going to have to go up to 4" dia?
2. Any ideas please about cheapest source of wheel castings? (ive got set of Dukedog/Bulldog driving wheels if any one wants a swap!)
3. Any problems with the valve gear please?
4. Can anyone help please with a suitable 'squat' safety valve design ala Gordon Smith
5. Any other hints and tips would be gratefully received, especially from fellow Brighton fans and anyone familiar with operating the full size locos!
by the way ive found Alan Stepney's site of corrections, and Norman Barber's excellent web pages for his 5"g TERRIER
cheers,
Julian
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Post by donashton on Jun 28, 2011 13:17:51 GMT
Julian,
Although not especially relevant, I looked at the Terrier full size gear for a friend and found it well designed. Things tend to deteriorate when asked to provide greater valve travels.
What a lovely little engine in any gauge!
Don
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Post by alanstepney on Jun 28, 2011 14:25:32 GMT
Anyone who builds a loco that is named after me, gets my vote!
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 28, 2011 15:01:25 GMT
thank you Alan! STEPNEY is the first loco i had a ride behind when i was 4 years old, so sentimental reasons for choosing No.55!
thank you Don...that is very good to hear, and wonderful to have an expert provide a considered reply!
i gather clearances are a bit tight between the inner slidebars to fit the lifting links (only 2 on BOXHILL compared to 4 on the fullsize locos).
i also notice there isnt a suspension point offset on the expansion link brackets, and the exhaust passages in the cylinder block are a bit restricted. i have got your stephenson's valve gear book, Don, so i will have to work out the suspension point offset, and check that the lifting links and weighshaft are in the correct position.
surprisingly the fullsize locos seem to be capable of quite a degree of notching up, despite the small valve travel.
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Post by albert on Jun 28, 2011 15:04:19 GMT
Hello Julian,
Just my opinion---I would not cut down on grate area--a smaller area will cut down steam production and will also make you force the fire, hence quicker clinker build up and more tendency to throw hot ash out of the chimney.
Working to as near exact to original does not always work in miniature.
Albert.
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 28, 2011 16:40:51 GMT
thank you Albert for your advice re grate area.
my reasoning is that
1. i cant stand sloping grates, and
2. as the boilers on the fullsize locos were excellently proportioned and excellent steamers and are full depth in front of the rear axle, there shouldnt be any need to extend the firebox over the rear axle as per BOXHILL.
3. Don Young didnt extend the firebox when designing his 7 1/4" gauge NEWPORT, despite having proportionately bigger cylinders than BOXHILL.
i have done my free gas flow calculations and they work out ok with the smaller grate. a friend of mine has a 3 1/2"g LSWR Adams '02' using a Rob Roy boiler, and cylinders about the same size as BOXHILL and it steams wonderfully without the fire being too fierce and forming clinker.
too big a grate can lead to a lazy fire, and the free gas flow figure for BOXHILL is quite low.
by fitting a backhead with a large radius to the flange (as per prototype) i can get a grate area of 8.25 square inches, as opposed to 9.97 square inches on martin evan's boiler design, and thats with me increasing the foundation ring width from 1/4" to 5/16" too. needless to say i dont like martin evan's BOXHILL boiler design at all! even the firehole door is the wrong shape for a TERRIER!
or am i missing something?
cheers,
julian
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Post by newington on Jun 28, 2011 18:47:38 GMT
Hi,
Building one as well, Blackgates supplied my boiler tube as part of their boiler kit,May be they can help. This my first attempt at loco construction and enjoying every minute. Ok the Finnish of my machining is not perfect but I am learning! Also the eccentric fitting to the crank axle, I should have made two fixing points instead of one as the eccentrics are prone to slipping.
Alan
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Post by donashton on Jun 28, 2011 19:04:05 GMT
Many models have difficulty in finding space for lifting arms, etc. If the full size had room so does the model. I prefer using a better steel spec. like EN 8 or even the more exotic steels. It may be more work but the parts will be plenty strong enough in scale sizes, and as a bonus they take a polish better.
Don
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davidm
Seasoned Member
Posts: 109
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Post by davidm on Jun 28, 2011 19:19:02 GMT
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Post by Jim Scott on Jun 29, 2011 9:39:58 GMT
Hello from yet another 5" Terrier builder. (No 83 Earlswood, 70% complete, modelled circa early1890's so as to retain the condensing gear and Stroudly livery). In reply to your questions 1 My alternative boiler shell construction was to roll from 13 SWG sheet (which I already had).The boiler is now complete and tested. Note that the bottom water gauge fitting as specified could leave the firebox crown uncovered with water still showing in the glass! Modern practice in our club is to fit rod stays to the crown instead of plate stays. 2 If I were to do my wheels again I would N/C or laser cut them from solid steel. The spokes on the original loco wheels were quite thin and almost rectangular section (possibly forged?) and the castings look overscale. 3 No real problems constructing the valvegear but I'm not quite finished this bit yet. Try inputting the info into Prof Hall's simulator, from which I optimised the link suspension to point to be 0.061" ahead of the link centreline. Link swing does seem excessive though at ~ 60 degrees. (Any comment Don?). 4 I have still to make the safety valve. I believe Gordon Smith's designs were published in EiM. 5 I'm also trying to make a true representation using Martin Evans plans and consequently there are many changes/additions. One early frame headache was the size of the frame lightening holes; I believe these were both the same depth in the original loco. Martin reduced the depth on the front one to accomodate the crosshead pump mounting. Also, look at the 'Metro' notes as there were some changes of materials specified. I concur with Don's comment re better materials for the valvegear linkages as some items are quite fine when kept to scale. Try 'Portrait of the Terriers' by Handel Kardas for some accounts of operating full size Terriers. Also, this youtube clip spurred me back into action when in the doldrums a few years ago: www.youtube.com/watch?v=JM30VZAeLA4&feature=relatedFinally, some good ideas on Norman Barber's build site but I have yet to look at Alan Stepney's 'Site of Correction'. I'll do it when I'm not thinking about model engineering... Keeep up the good work! Jim S |
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Post by donashton on Jun 29, 2011 10:17:10 GMT
Jim,
The 0.061" offset sounds about right when taking into account the overscale valve travel on Boxhill, but I have not looked closely at Martin Evans' drawings - yet! The swing is massive, but where are we measuring? My spreadsheet limits this automatically to 25 degrees, but we have to add the angle caused by depth in gear. The curse of overscale travels will exaggerate this.
I'm currently looking at Julian's competent figures, particularly as he is much closer to the excellent original gear. Many old gears from this era are poor, but the Terrier is not one of them. Also, one might logically expect to have back gear mirror fore gear, but one often meets with poor forward and better reverse - it can be long-winded to switch the better bias to fore gear.
Don
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Post by alanstepney on Jun 29, 2011 10:27:06 GMT
At one of the exhibitions a few years ago, was a display of locos built by "the professionals".
One was a Terrier to 7 1/4" gauge, which was highly detailed and from my brief examination, appeared to be accurate to both scale and detailing.
Someone may recall which exhibition it was and who the builder was.
(On the other hand, I might be able to find a photo of it, I'm almost sure I took one.)
I wonder what drawings the builder used?
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 29, 2011 10:28:18 GMT
thank you for some excellent replies!
anymore help would be gratefully received!
the original wheels are a Brighton feature being a cast hub and rim and cast balance weights, with wrought iron spokes. the hub (wheel centre) is therefore quite big and stands proud of the spokes by quite an amount. also the balance weights are opposite the crankpins, and the crankpins are in line with the connecting rod pins... Stroudley's pet idea about balancing, which necessitates a larger balance weight.
i dont like martin evan's peculiar crownstays which dont connect with the outer firebox at all, though he claimed with a curved inner crown to the firebox his method was ok. ive never had a problem silver soldering up proper plate type crown girder stays to the 'box and outer firebox.
i presume alan that you are building No.46! i remember seeing her outside the hayling billy pub, and have enjoyed a ride behind her many times on the IW as W8.
thankyou jim for your very helpful comments. i do like the idea of steel wheels. one of my other locos has steel wheels. thankyou for the very helpful information about the valve gear suspension offset and swing... neither my brain or computer is up to using a simulator, but i am working through Don Ashton's excellent book (ive used it quite a few times with excellent results).
i had worked out a boiler design based on 4" dia tube, partly because a 4" wide firebox will fit between the frames, and the better tube layout i can get with a higher crown and flat topped and straight-sided inner firebox as per the prototype, and also the fact that martin evans shows the wrong diameter of smokebox (and smokebox door) and im proposing to do an A1X rebuild.
the smokebox should be 4 1/4" dia and not 4" dia, and the smokebox door should be 5/16" greater in diameter.
martin evans also widened the loco to fit in wider side tanks! the buffer beam width should be 7 1/2" not 7 7/8". the tanks should be 6 29/32" across and not 7 3/4"! it will be clear from the above that whereas martin evans' side elevation drawing is correct to 1 1/16" scale, his end elevation is not! why mess up an otherwise 'scale' design i really cant understand, just to get a bit more water in side tanks that are still too small for most of us! (i am building an LBSC 10 ton truck which will have a water tank and coal space to go behind the loco).
Someone on the ME forum site has also pointed out that the cab roof shape is incorrect on sheet 8, though the general arrangement drawing is correct. (anyone made a former for the cab roof?)
all the fullsize locos had sight feed lubricators to the cylinders, so ive already made a rather dinky little one that ive tested.
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Post by GeorgeRay on Jun 29, 2011 21:01:53 GMT
Actually Julian the full size locos did not originally have sight feed lubricators. They had little displacement lubricators on the front of the wing plates. But as you are building an A1X then sight feed is OK. The biggest error with Martin Evans design is the smokebox which while OK for an A1X is totally wrong for an A. It should not be circular but slab sided below the centre line. However my Fenchurch will make three laps of our 850 foot club track on one fill of the tanks with no other water supply. I should add that there are two long climbs of 1 in 100 to cater for. All in all a super model which is smaller than many 3 1/2 locos but goes extremely well.  |
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Post by chris vine on Jun 29, 2011 21:10:56 GMT
Hi Alan,
I wonder if the exhibition you were thinking of was the old midlands at Donnington. Maybe the last before the move to the Fosse.
There was a display of 2 or 3 locos by David Aitken. A Castle I think and a 7.25" gauge Terrier. Quite beautiful. I was particularly taken by the hand painted coat of arms on the side tanks.
Chris
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Post by Jim Scott on Jun 29, 2011 21:37:36 GMT
Julian
It hadn't occured to me to check the overall widths etc, probably because I built the frames almost 40 years ago (slow builder!). I had realised though that the smokebox dia was too small, and no attempt had been made to represent the flat-bottomed appearance as per the original unrebuilt locos.
My intention re lubrication is to fit a hydrostatic type with the tank under the footplate. Could be interesting...
Would be interested in details of you LBSC 10-ton truck at some later date.
Don
I may have misunderstood, but the Hall Sim reports link swings in full forward gear as: anticlock -24.9, clockwise 34.7 degrees. However, as most of the valvegear components had been built exactly (and in the case of the eccentric rods, incorrectly) as plan before I discovered your book, my only variables left were valve adjustment on its rod, the link suspension offset and the eccentric positions. The table of cutoffs looks reasonable though; I look forward to the results of your evaluation of Julian's layout.
Jim S
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Post by donashton on Jun 29, 2011 22:11:47 GMT
Jim,
I'm sure that you are right, though I never grasped Bill's anticlock and clockwise - as the link swings about a centre. Which side of the engine are you standing to determine clockwise?! His diagram is American style and I think British. You also have to decide at which cut off position the leads are equally set, whereas if the eccentric rods are corrected in the first place the leads remain equal throughout, or very nearly so.
An oval diagram is not my favourite at-a-glance indicator of good equality. Mainly, I use the Wallace 'family' graphs - much quicker and easily evaluated equality of all events at once. Neither provides the tell-tale cut off table even though the information is all there, and I'm not clever enough to tinker with the program.
Julian's case is interesting in that he already has the eccentrics in place, so everything revolves around that, which entails a lot of 'reverse engineering' to arrive at suitable ports and valves - the normal starting point! On the real Terrier the expansion link gets very close to the motion plate and there is an accommodating scoop to cope with it, and the boiler is almost clouted in full reverse.
I'm sure Julian would like to inform those who have shown interest in his thread, but there's a little bit more design work to accomplish first. Thanks for all the comments on this fascinating little engine, quite apart from just the valve gear.
Don
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Post by alanstepney on Jun 30, 2011 6:13:00 GMT
Hi Alan, I wonder if the exhibition you were thinking of was the old midlands at Donnington. Maybe the last before the move to the Fosse. There was a display of 2 or 3 locos by David Aitken. A Castle I think and a 7.25" gauge Terrier. Quite beautiful. I was particularly taken by the hand painted coat of arms on the side tanks. Chris Chris, I think you are correct. They were, as you say, works of art. I wonder what drawings were used for the build? |
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Post by donashton on Jun 30, 2011 8:35:10 GMT
Alan,
Knowing David Aitken they will be the Swindon drawings!
Don
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jun 30, 2011 8:59:32 GMT
thank you all again for some wonderful replies. Don has been extremely helpful with his time and expertise, and i am sure in due course many will be interested in his results of grappling with martin evans' version of the TERRIER valve gear. the LBSC 10 ton wagon is to SR diagram 1369. very few survived into the BR era; luckily the Bluebell Railway has a preserved example, and a few survived on the Isle of Wight to the end of steam and a couple are preserved at Havenstreet. George is quite correct about the Terriers only being fitted with sight feed lubricators later on... there is plenty of room to fit a displacement tank under the cab, and it doesnt have to be very big as hydrostatic lubricators feed far less oil than the usual mechanical pump. the sight glass should be in the right hand front corner of the cab, where, incidentally STEPNEY's pressure gauge still is - the original position - though all the other Terriers i have seen (apart from BOXHILL in the NRM) have the pressure gauge now on the cab spectacle plate. i find it remarkable that after some 120 years new boilers, wheels, and cylinders were made for this marvellous little engines to keep them in steam for future generations! such is their appeal and usefulness! i am guessing that the 7 1/4"g example referred to is to Don Young's NEWPORT design, which is much more accurate to prototype than martin evans' BOXHILL. Don did an A1 version and an A1X version. anyone still at the frame stage could easily copy the fullsize frame stretcher across the rear horns and extend the drawhook to a mounting on it so maintaining another of Stroudley's pet ideas. i came unstuck with STEPNEY's buffer beams as from 1905 a lot of the surviving locos were converted for motor train working and had their buffers raised... STEPNEY is one of those, as was BOXHILL, though BOXHILL's buffer beam was altered back to the original when restored in 1947. i notice that the inner slidebars on BOXHILL have to be relieved to clear the lifting links/suspension levers. this is a bit of a pain as i would quite like to have fitted the channel type slidebars as fitted to the originals. i think martin evans could have moved the cylinder bores out a bit to give more room for the valve gear suspension... i dont think that slightly thinner crank webs and axleboxes would have been a problem... Don Young's 02 FISHBOURNE has the cylinder bores 3/8" further apart with considerable advantage for the valves between arrangement and the valve gear. if i was making another Terrier i think i would follow Don Young's layout of the cylinders and crank axle (haha could always swap as i made a set of cylinders for a 5"g 02 to Don's design out of solid lumps of cast iron, and made the crank axle as well...only joking as the bore and stroke is wrong for a Terrier). we havent discussed the Stroudley livery yet....! many thanks again, Julian Attachments:
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