dscott
Elder Statesman
Posts: 2,440
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Post by dscott on Jan 5, 2018 0:06:05 GMT
The solution is I have found with current projects, is to attach a big sheet of white card onto the drawing board!
Get a works drawing and fix it up to the left! On the right are the drawing bits and a supply of wine!
Deep breath and mark out the wheel centers. Draw in a correct wheel with the correct number of spokes, spoke from
the crankpin or spokes either side! Correct hornblocks! Valve gear computer corrected. Then get the cylinder in
the right place.
Now draw the correct size of boiler leaving room for some insulation? Asia take note (4 1/2 diameter and 4 1/2 diameter
over cladding is not the way to proceed!!! She now has a 1/2 inch slab for the firebox stay and a huge block under
the footplate! Oh and from the works drawing comes full length inner frames to be cut out when I get the 1500 ones done!
Take tracings for detail parts onto A4 or A3 so you can photocopy and use them in the workshop and still correct them.
Rooter, Europa 54, and 15XX should get you and me round any copyrite issues especially if you swap 4 BAs for 6 BAs and
go for more scale parts!Now in the right places! Swapping the reverse lever from left to right alters the small Prairie
sufficiently plus smaller tanks, smaller boiler, better pony trucks... Oh stop it! Not another!!!
David and assistant Lily now expert on how to get a heavy milling machine onto the bench using everyday objects found
around the home!!!
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Post by terrier060 on Jan 13, 2018 11:45:55 GMT
Has anyone got details of either 5" or 7.25" 'Terrier' chimneys. The reason I ask is that I am not sure whether to use a parallel steel tube for the inner liner and have the chimney slide over it as I have done on my other engines (they have short chimneys though). The full size chimney is slightly tapered inside. The experience of those who have 'Terriers' running would be greatly appreciated.
Ed
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Post by Deleted on Jan 13, 2018 12:15:18 GMT
Hi Ed....I think that most answers will be that the taper is an important part of the drafting and therefore best kept, whether you follow the drawing or investigate the drafting further for better steaming will be your decision...I'm sure that Julian can help guide you with this...
regards
Pete
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Post by terrier060 on Jan 13, 2018 14:44:38 GMT
Cheers Pete - I guess you are right about the taper.
Ed
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Jan 13, 2018 18:36:00 GMT
Hi Ed,
Long chimneys are more forgiving for smokebox draughting than short chimneys (including the petticoat pipe).
My own example has a 3/4" dia 'choke' above the bell or flare on the bottom of the petticoat pipe. Martin Evans specified a 7/8" dia choke. He also got the distance between blast nozzle top and choke far too great for optimum performance.
The converging taper from choke to chimney top on the fullsize Stroudley chimney would now be regarded as far from optimal, a diverging taper being preferred. Hence the Drummond chimney fitted to W8 on the IOWSR (and most IOW Terriers at the instruction of A B Macloed in SR days) is regarded as an optimal arrangement. The Drummond B4 chimney fitted to the IOW Terriers has a diverging taper internally from choke to chimney top.
If you care to study the works of Goss and Young in the USA on smokebox draughting, a diverging taper as above of some 1:12 or 14 gives superior results and something like a 20 or 25% better performance compared to a parallel internal bore. Sam Ell used this diverging taper on the GWR and later at the Rugby testing plant and Swindon in BR days.
My own example has a slight diverging taper from choke to chimney top.
I sent the drawing of my chimney and smokebox draughting dimensions to Jos Koopmans, and he commented that the choke should have been smaller still by 1/16" and in retrospect I would probably agree with him, but the reduction from 7/8" to 3/4" dia for my choke plus the diverging taper will definitely be an improvement on the Martin Evans drawings, plus the distance from blast nozzle top to choke is considerable less than the Martin Evans dimension notwithstanding the smaller choke on mine.
Anyway to summarise, it is possible to achieve a very good arrangement for the smokebox draughting for a Terrier fitted with the Stroudley chimney (and the later Basil Field/Marsh cast iron chimney). The Drummond B4 chimney would be better still, and Don Young comments upon this in his construction series for his 7.25"g Newport in LLAS.
Ed, if you email me a few details I will work out for you something close to Jos Koopmans' research.
Cheers,
Julian
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Post by terrier060 on Jan 14, 2018 13:30:11 GMT
Many thanks Julian - that would be greatly appreciated - I will email you a couple of PDF files which should print out to scale. Measurement details are on a couple of drawings in my 'Terrier' thread.
Ed
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Post by Jim Scott on Aug 29, 2018 22:37:26 GMT
In a gentle attempt to further the continuing construction of 'Stepney' I include this link to an un-edited video clip of the first run on air of my Terrier 'Earlswood'. Always an important milestone, especially when you have been mucking about with the design of the valve gear. www.youtube.com/watch?v=VzEEJnKXIdUAir is supplied by a small 12V compressor as used to pump up car tyres, there is no receiver hence the operating pressure of 9 psi in full gear. Notching up uses less air and the pressure can get up to about 17 psi with a slight increase in speed. Julian, this thread has been going for some years now and it contains much good info for those building Martin Evans 'Boxhill' design. I hope you can find a way past your current hiatus, I would love to see it finished but remember I haven't got too many years left...! Jim S |
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Aug 29, 2018 22:57:25 GMT
Hi Jim,
Thank you so much for posting the above youtube link. I hope all will take a good look at same.
Absolutely wonderful and superb! You ought to be very pleased with Earlswood's chassis running on air so sweetly!
Cheers,
Julian
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Post by Deleted on Aug 30, 2018 7:02:31 GMT
Hi Jim
Great video of a very well made loco...she runs very well sir...I echo your encouragement to entice Julian back to his lovely A1 too..please do continue with yours Julian. I for one would love to see it in steam...
Kind regards
Pete
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Post by terrier060 on Aug 31, 2018 23:51:15 GMT
In a gentle attempt to further the continuing construction of 'Stepney' I include this link to an un-edited video clip of the first run on air of my Terrier 'Earlswood'. Always an important milestone, especially when you have been mucking about with the design of the valve gear. www.youtube.com/watch?v=VzEEJnKXIdUAir is supplied by a small 12V compressor as used to pump up car tyres, there is no receiver hence the operating pressure of 9 psi in full gear. Notching up uses less air and the pressure can get up to about 17 psi with a slight increase in speed.
Julian, this thread has been going for some years now and it contains much good info for those building Martin Evans 'Boxhill' design. I hope you can find a way past your current hiatus, I would love to see it finished but remember haven't got too many years left...! Jim S Great Jim. It is so satisfying to see and hear them running. Mine have actually carried passengers! About 20 years ago I put a plank of wood across the top of them and my friend's two five year old twins had a race down my workshop on compressed air! I said by the time they were 8 they could drive them properly on a track. They are now both qualified vets!! You can see how far I have got with the locos - not a lot further. But this CNC and Roger, bless him, have given me a new drive. |
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Post by terrier060 on Aug 31, 2018 23:54:08 GMT
Hi Jim Great video of a very well made loco...she runs very well sir...I echo your encouragement to entice Julian back to his lovely A1 too..please do continue with yours Julian. I for one would love to see it in steam... Kind regards Pete I echo those remarks, having met Julian at Bristol ME exhibition. Perhaps like me he should go CNC!! How about it Roger, shall we brainwash him. Ed |
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Post by Roger on Sept 1, 2018 8:59:05 GMT
Hi Jim Great video of a very well made loco...she runs very well sir...I echo your encouragement to entice Julian back to his lovely A1 too..please do continue with yours Julian. I for one would love to see it in steam... Kind regards Pete I echo those remarks, having met Julian at Bristol ME exhibition. Perhaps like me he should go CNC!! How about it Roger, shall we brainwash him. Ed Good luck with that Ed... |
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Post by Jim Scott on Sept 1, 2018 19:50:42 GMT
Mine have actually carried passengers! About 20 years ago I put a plank of wood across the top of them and my friend's two five year old twins had a race down my workshop on compressed air!
Hi Ed
I have a battery and the compressor line is long enough. The temptation to do just one lap around our track may yet prove irresistible......
Jim S
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Post by steamer5 on Sept 1, 2018 22:57:13 GMT
Hi Jim,
Do you know anybody that scuba dives? Dive bottle & a regulator has got to be better than getting your power cable caught on something or stood on!
Cheers Kerrin
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Post by Jim Scott on Sept 4, 2018 17:29:16 GMT
Hi Jim, Do you know anybody that scuba dives? Dive bottle & a regulator has got to be better than getting your power cable caught on something or stood on! Cheers Kerrin Hi Kerrin, Just to clarify, the small compressor and its 12V supply battery are small enough to carry on the driver's trolley, there would be a relatively short pipe connection to the steam chest inlet.
Cheers Jim S |
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Post by runner42 on Sept 4, 2018 22:47:51 GMT
Hi Jim,
an excellent well made chassis, a final touch to demonstrate its capabilities is to see it running in reverse.
Brian
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Post by Jim Scott on Sept 5, 2018 21:56:18 GMT
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Post by runner42 on Sept 5, 2018 23:40:38 GMT
Hi Jim,
it runs on the smell of an oily rag. Did you modify any of the original valve gear arrangements and or the method of sealing the pistons. Notwithstanding any changes the design is probably one of Martin Evans' finest examples of Stephenson's valve gear.
Good luck with the remainder, it will be a winner at some level or other.
Brian
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Post by terrier060 on Sept 5, 2018 23:59:19 GMT
What a pity the compressor drowns out the beats. Nothing like Stevenson's valve gear for even running in both directions. You can borrow my oxygen cylinder if you like - that should really perk it up! Wizz around the track!
They look so much better painted - shall have to have a go at mine.
Ed
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jma1009
Elder Statesman
Posts: 5,922
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Post by jma1009 on Sept 6, 2018 0:07:58 GMT
the design is probably one of Martin Evans' finest examples of Stephenson's valve gear Sadly, Brian, the Martin Evans valve gear is wholly deficient, as is your own Rob Roy of similar design vintage from the early 1960s. We discussed all this in some detail early on in this thread, but I excuse you for not going back to the beginning of this thread! Martin Evans had very little understanding of Stephensons valve gear. Jim spent a lot of time on the Hall simulator correcting the Martin Evans design of the valve gear. With a centrally suspended link your request to see his chassis running in reverse did not make much sense to me, as it would perform as one would expect as the result of the geometry and Jim's modifications. It would perform perfectly well in reverse as in forward. In my case, as exemplified by the beginning of this thread, Don Ashton did all the hard work for me, which Jim did not have the benefit of. Don did an analysis for me of the original Martin Evans Stephensons gear and the results were VERY poor! All this was discussed early on in this thread, and Jim contributed his own computer simulations from Hall which actually were not far off Don Ashton's redesign for me, which incorporating alterations to the Lap and valve travel, meant that the 2 versions are not exact, but I have run Jim's own version on Hall and the results are compatible and very close, and by a simple adjustment (of which Martin Evans was ignorant of) Jim got very close to what Don Ashton devised very kindly for me. What I take issue with you is that this was "probably one of Martin Evans' finest Stephenson's valve gear' ". If this was his 'finest', which Don ran on his simulator and produced VERY poor results, one might be very alarmed at Martin Evans' less than "finest" Stephensons valve gear designs!! Cheers, Julian |
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