Errors on drawings

[springcrocus]

I have started to compile a (quite extensive) list of errors and omissions for the 5" Britannia to the Norman Spink drawings, as supplied by Blackgates. There is no point listing them on here (they will get lost in the mists of time) and have created a dedicated page on my website instead. I don't know if these also apply to the Perrier drawings which were the forerunner to my set. If any Britannia builder would like to advise me of any errors they have found in their own constructions, I am happy to add them to my list and credit them accordingly.

Regards, Steve

[JonL]

May 26, 2018 22:17:41 GMT springcrocus said:

I have started to compile a (quite extensive) list of errors and omissions for the 5" Britannia to the Norman Spink drawings, as supplied by Blackgates. There is no point listing them on here (they will get lost in the mists of time) and have created a dedicated page on my website instead. I don't know if these also apply to the Perrier drawings which were the forerunner to my set. If any Britannia builder would like to advise me of any errors they have found in their own constructions, I am happy to add them to my list and credit them accordingly.

Regards, Steve

Would it be possible for me to use the list on your website on the Small Steam Engine Wiki please? It would be a great help to potential builders.

[ettingtonliam]

This relates to the drawings for the 7 1/4" gauge model of 'Locomotion' designed by David Piddington around 1997 or 8, for A J Reeves. He did keep up with any amendments brought to his attention, and revise the drawings up to the demise of the 'old' Reeves in late 1999. Since then, nothing seems to have happened, nor does there seem to be any interest in making it happen.
I know its not the most popular model in the world, but I do know there are several of you out there in various stages with it, so this might be of some help.

Sheet 1 - general arrangement right hand side.
On the prototype, now in Darlington, the pump is mid way between the 2 wheelsets. In 1928, when Henry Greenly produced a design for 'Locomotion' in 7 1/4" gauge, for reasons I don't understand, he moved the pump forwards so that it was very close to, almost fouling, the front right hand wheel.
The Piddington design replicates this pump position, as does the German Atelier design ion 5" G. Later, on sheet 4 (wheels) there is a note to reduce the flange depth of the front right hand wheel to 1/8", from the designed 5/32", to aid clearance of the pump, and on sheet 6, showing details of the pump, there are more notes about filing flats on the pump body to clear the wheel. I don't see the point of this, and am going to move the pump rearwards by 1/2", so that it clears the wheel.

Sheet 2
The length of the tender water tank top plate is shown as 5 7/8". This should be 6" to fit the tank body.
Update 17/09/2021.
The tank drawing recommends the installation of a Reeves standard hand pump to drawing RV60. I bought the casting for this at the same time as the other castings, but have only just got around to making it, having made the tank a couple of years ago. Now I discover that the pump is 3 1/2" high to the top or put a 1/2" raising flange round the tank opening cut out to lift the level of the lid above the pump. The original is on at least its third tank, so theres no saying that it never had one. If I'd realised the problem before I made the tank, I'd simply have made the tank 3/8" taller. Oh yes, its also necessary to convert the pump outlet to a 90 degree fitting because 'straight up' as drawn would be too tall as well, but this isn't a big deal.

Sheet 3 - boiler
This has several amendments dated 1998 and 1999, which I believe increased the wall thickness of the firebox tube, and gave additional clearance under the firebox, following adverse comments from boiler inspectors. There are a large number of thickening plates shown on the inside of the barrel for numerous bits and pieces to be screwed on, as the boiler is in effect the chassis, and everything fits on it. The idea was, with a 10G barrel and 4mm thickener plates, for blind holes for the fixings to be drilled and tapped into the copper, and then the whole assembly to be caulked with Comsol after assembly. My boiler inspector wasn't happy with this and neither was I, so my approach is going to be to fit 3/8" long, 3/8" OD phosphor bronze blind bushes, screwed 3/8 x 32TPI instead. For high load items such as the axle mountings I will retain the thickener plates, but where its only low stress such as for footboard mountings, I'll leave out the thickeners.
As noted above the pump position needs to be moved back to 2 9/16" behind the front axle, instead of 2 1/16 as shwon. and the pump stay moved back correspondingly.
There are 3 bushes under the barrel for blowdown and 2 feed clacks. Firstly theres no need for 2 feed clacks, as the pump feeds directly into the boiler without an external delivery pipe, and that only leaves the hand pump. This position does correspond with the prototype, but a worse position for a feed clack I can't think of. Therefore, I'm going to delete the 2 clack bushes and fit one on the backhead, 1/2" below boiler centreline, and 2 1/4" to the left of centreline. Not ideal I know, but better than under the barrel. I'd move the blowdown too, if I could, but there isn't any room at the bottom of the backplate.
The safety valve is a single deadweight valve to match the prototype. I'm not happy with this, so am going to in corporate 2 bushes on top of the barrel between the backhead and the rear cylinder, for 2 modern low profile valves. Then the deadweight can just be a dummy.

Sheet 4 - Loco Wheels and axleboxes

The wheel tread profile given doesn't correspond with the 7 1/4" gauge Society recommendations for standard gauge prototypes. The wheel width needs to be increased from 3/4" to 13/16", and the flange depth from 5/32" to 3/16", with slight alterations to the profile of the flange. There seems to be enough metal in the castings to enable this to be done.
Back to back dimension from the 7 1/4" Society is 6 13/16". Nowhere on the drawings is this dimension given, you have to calculate it by adding and subtracting various dimensions, and it doesn't work anyway! Width over the axleboxes is 5 3/4", so allowing 1/32" sideplay each side, the hub projection at the back of the wheel should be 1/2" beyond the back face of the wheel, or 21/32" from the wheel centre which is recessed by 5/32" from the back of the wheel face. Therefore, you would think, the length of the axle between wheel seats should be 5 13/16", but its shown as (after some calculation as 5 5/8", with a wheel seat length of 1 13/32", which should I think, be in fact 1 3/8" allowing for a 1/16" chamfer at the ends of the axles.
This lot should have some effect on the length of the overhead crossbeam which the con rods fit to, but I can't make any sense of this at all, and will wait until I've got the wheels and crankpins done, and measure them before attempting the cross beams.

Update 07 04 2020. Measuring across the wheels 'as built', gives me a distance between centres of the vertical connecting rods of 9 3/16". The drawing dimension is 9 1/4", so given that I've played around with the wheels to acheive the 7 1/4" gauge Society wheel profiles and back to back dimension, I'm not disatisfied with the result, and will just shorten my overhead beams by 1/16" to suit my wheelsets 'as built.

If the cast gunmetal sticks (2 of them) I was supplied with for the various con rod and coupling rod bearings are the right ones, then they are too short to cut into the requisite number of bearing halves! By my calculation it needs 3 sticks.

Update 7/04/2020. The gunmetal sticks are inscribed 'Invicta Mains' and are in fact the castings supplied by Reeves for the driving axleboxes of their 3 1/2" gauge 'Invicta'. I checked with them that I'd got the correct item for Locomotion, and was assured that I had, and that 2 of them should be sufficient, and anyway 'no one else has complained'. Well, yes they are right, they can be got from 2 sticks, but only by using a 1/32" slitting saw for cutting them up. As the Duke of Wellington is supposed to have said after the Battle of Waterloo, 'it was a mighty close run thing.'
Update 05 03 2022. Some of the parallel motion parts are on this sheet as well and I've just noticed that for the parallel pivot lever the drawing says 2 off. It should say 4 off!

Sheet 5 No comments at present

Sheet 6 Valve gear layout and pump details.
Locomotion has an odd valve gear, both valves being driven from one slip eccentric on the front axle. The front cylinder valve is driven directly from the eccentric strap by a long rod to a rocking shaft at cylinder level. The rear cylinder valve is driven from the side of the eccentric strap via a bell crank, and then by another long rod up to the rocking shaft at cylinder level. An original sketch done at Robert Stephensons works in 1825 showed that they appreciated that the 2 valve operating rods should be as near as possible parallel to give similar valve events. The prototype roughly achieves this. Greenly showed the position of the pivot of the bell crank to be well to the rear, behind the rear left hand wheel. This resulted in the 2 valve operating rods being considerably out of parallel, so angularity effects on the rear valve would be considerable compared to the front valve. David Piddington's design and the Attelier one both replicate this position of the bell crank. To correct this means moving the position of the bell crank forwards significantly. How much I haven't yet worked out, but probably about 1". This means redesigning the bellcrank mounting, and probably hanging it off the boiler rather than off the axle mounting saddle. The bell crank itself would benefit from longer arms to reduce errors induced as it rocks. A work in progress!

Update 21/03/2022.
The lower section of the valve spindle is shown as 1 1/4" long. It should be 1 3/4" from the centre of the buckle to the end of the threaded section, at least it is on mine!No dimension is given for the length of the buckle, but 3/8" seems to work OK.

Update 06 09 2022
As drawn, there are 1/16" dia stainless steel pegs press fitted into several places in the pump body to act as lift restrictors for the pump balls. This is all very well, but does make dismantling the pump for cleaning very difficult. Anyway I've modified the design of the square headed caps to incorporate a 5/322 dia pintle extending down to 3/32" above the ball. This will restrict the lift and at the same time allow the balls to be readily removed. There are also several 1/4" x 40 TPI plugs to be inserted to seal off the ends of cross drillings, to be trimmed off flush after assembly. I've made these little square headed plugs, again to allow for removal later if required. Not prototypical, I know, but forgivable I think in the circumstances.

Sheet 7 Cylinders and chimney

I really haven't looked at the cylinders yet. Julian has expressed some doubts about the draughting in the chimney, as drawn, and certainly a blast nozzle size of 3.7mm for 2 no. 7/8" bore x 3" stroke cylinders seems a bit on the small side. So do the exhaust pipes which are 3/8" OD 16G pipe and over a foot long. I'm considering 7/16" OD 20G, which would still be reasonably to scale but free up the exhaust considerably. Still a work in progress. Julian also thinks that the exhaust manifold in the chimney could be more streamlined, to eliminate sharp 90 degree bends.



Update 06 09 2022
I didn't in the end increase the size of the exhaust pipes, but used the 3/8" 16G as designed. I may live to regret this, but its made now.

Update 07 04 2020. I've made the blast nozzle with a 4.5mm bore rather than the 3.7mm as drawn. In 5 years or so, I'll report back on how this works!. I've also streamlined the manifold passages as much as possible. In a conversation with one of the few chaps who have actually built and run 'Locomotion', he commented that the blower needs to be larger. As designed its a ring of 1/16" dia copper pipe surrounding the blast nozzle, with 3 0.75mm holes in it. 1/16" pipe seems a bit small, certainly, so I'll make it from 1/8" pipe, and see how that works.

Update 24 02 2022
There are numerous flanges intended for 8 BA fasteners (Piston rod gland, valve rod gland, exhaust pipe flanges) which are shown as 'drill 1.8mm ' intended to be clearance, when it should read 'drill 2.3mm '

Sheet 8 Boiler lagging and ashpan details. The only thing I've noticed on this (work on these items is about 5 years in the future) is that the boiler lagging planks are shown a 30 No 5/8" wide ash strips to cover the top half of the boiler only. For a 6" OD barrel, 30 strips need only be 5/16" wide, and this looks to be about 'scale' to the prototype.

Sheet 9 Tender GA and tender wheels

The same issues as the loco wheels described for sheet 4 above.
Width should be 13/16", flange depth should be 3/16". Machined to the drawing dimension of 3 3/4" tread diameter, the wheel tread ends up looking very thin. It might be an idea to increase the tread diameter to 3 7/8", to give a more robust wheel. There's enough metal in the casting, and an increase in tender ride height of 1/16" isn't going to be noticed.

Width over the axleboxes is 6 1/2", so allowing 1/32" end play each side, should need a 1/8" long boss at the back of the wheel, not 1/4" as shown. The axle length between wheel seats should be 6 9/16", with a wheel seat length of 29/32. (the tender wheels are clamped onto the axle by a bolt and washer on the axle end, so the wheel seat is 1/32" less than the wheel width.)

As drawn, the tender has no springing at all, in accordance with the prototype. I'm incorporating a couple of 9/16" long x 1/4" dia coil springs to each wheel, pocketed 1/4" deep into the top of the axlebox and 1/8" deep into the top flange of the axlebox pedestal, to give a movement of 1/8". Not much, but better than nothing.
Its worth commenting that if you are using the Reeves axlebox castings, theres no machining allowance worth speaking of across the faces that slot into the pedestals. With care, and reducing the 7/8" dimension to 27/32", its possible.

Sheet 10 - tender body

Not much here to honest, except that only 2 inner stretchers are needed, not 4 as shown.

As designed, the front and rear drawbars bolt to wooden cross stretchers, so the whole tractive effort is taken via a couple of small mortice and tenon joints. I'm going to fit a couple of long threaded bars, 3/16 dia, running the whole length of the tender, to directly connect the front and rear drawbars. A bit safer I think, even though 'Locomotion''s tractive effort at 50 psi is likely to be in the 'won't pull the skin off a rice pudding' category.



A lot of the valve gear has a recommendation that temporary flat steel links are made first, only making the final ones when satisfied that they work. There have been several completed models, but I believe that a fair amount of modification was needed. I'd be interested to hear from anyone who has made and run one, or even anyone who runs one they didn't make themselves.

[JonL]

I'd like to copy this onto my wiki for the help of other builders, if you are not happy with that let me know and I will remove it straight away.

[dscott]

I have got to the point of not cutting any metal until the design has been re worked with possibly the works drawings in the other hand!!
The Asia is being done from the last painted and lined piece being bolted in place. And the ash pan sliding effortlessly into position. And masses of added weight hiding within a full length inner frames which makes her inner motion easy to set up! Last week saw the leading drivers having an inner pair of horns and axlebox added to enable this to be done! The outer frames now slot into 3 blocks attached to the inner frame and get secured with 6 bolts or grub screws from underneath! So simple and not messing up any Brown paint!
Solutions mostly thought up while struggling with other projects???

I started again with the Speedy unfortunately it is the only way as there is far too many problems starting with the angles at the front of the frames, and cut outs under, the width, and sheer number of holes needed as per full size!

Even the Black Five is let down on numbers of rivets on the tender frames which can be counted from a OO Hornby model to being more accurate! Again I am not adverse to having 2 or 4 larger bolts holding say smoke boxes to saddles and an array of scale ones fitted in the right places! In fact the Speedy is having a backing plate fitted as per the Five and using the existing cylinder casting.

David and Lily.

[ettingtonliam]

Works drawings for 'Locomotion' You must be joking! Apart from the schematic sketch of the valve gear proposal, there is nothing else, probably never was. Trevithic is supposed to have done his 'drawings' with a poker in the sand of the foundry floor! Not even any contemporary sketches or paintings, until early photographs appear around the 1860s. By this time it had worked for 15 years, was on its 4th boiler, had been set aside, used as a colliery pumping engine, and finally 'plinthed' in the open air. Since then, its been 'restored' several times.
At least the rivet counters can't get me, my guess is as good as theirs.

[ettingtonliam]

More Locomotion stuff.

Following my investigations into the valve gear, the pivot point for the rear valve rod bell crank is now 3 7/8" behind the front axle centreline and 1 1/2" above it. There are a few other changes necessary to accomodate this, but they are new components, so not 'errors'. With the change in pivot position, the bell crank is best driven via a straight link from a pin at the foot of the eccentric rod, rather than a bent link from the eccentric strap. There are thoughts that the original had this arrangement at one time. The bell crank now has 1" crs on the vertical leg and 1 3/16" on the horizontal leg to compensate for the reduced travel from foot of the eccentric rod.
I'v e just noticed that the axlebox pedestals are shown as 2 13/16" long on Sheet 4, but as they are supposed to be the same length as the cradles which support them, this dimension should be 2 1/2".

Investigations into the parallel motion suggest that the radius of the swing link should be 1", not 0.875 as shown on Sheet 4, and the pivot frame shown on Sheet 5 should be 4 5/8" centres between upper and lower pivots, not 4 3/4" as drawn. David Piddington's suggestion about making temporary flat links to check things out seems a good idea. It seems to be critical to the geometry to ensure that piston mid stroke, the swing link pivot at the top of the swing link stanchions and the top pivot pin of the pivot frame are all at the same level. This might need some adjustment on erection to achieve.

[cadser]

I am currently looking for a set of drawings for the 5” Britannia. I will not be using them to build to, rather as a reference to get my Winson running correctly and get certain detail correct.

Looking at all the posts for corrections which should i choose if i am offered a set?

The biggest unknown for me is the valve gear and timings. There are also lots of post on this but not enough to go forward with to be confident to make changes. If i had a set i would be able to get centre distances.

Brian

[heyfordian18]

I would like to share information with anyone who has built or is building Don Young's Tom Rolt in 5" gauge
I would appreciate help and information about the radial truck construction.
Specifically, how does it attach to the spring beam, I think that there is detail missing from the drawing.

[choochooenthusiast]

Jan 29, 2012 9:55:31 GMT springbok said:

Page 2 of errors in the Martin Evans Thompson class B1 Springbok

Based on having to raise the footplates on the sides of Springbok, would you say its worth bringing up the width of the mainframe 1/2" as well so there isn't an unsightly gap?

Connor

[tigermoth]

Hi All.

When I was building the Kennion's King I had an arraignment with them that when I found an error I marked the sheet up and sent it back to them so they could change the master and then send my copy back to me, this worked quite well as I knew that the alteration had been double checked at my end and then corrected.

Wish I had kept those sheets but I sold them on when the engine went.

Norman.

[dscott]

I got a lovely response from a builder of an ASIA?
Yes he completed it very quickly and it does look superb. Surprise when he said that the done to drawings eccentrics clash with the Boiler. DO NOT WORRY AS HIS IS A WOODEN MODEL.
My conclusion during the re draw is that the Boiler barrel is far too big and the same size as the outer cleading.
Remember that she is an old design and set to potter round the track.
Spent some time working on the inner horn plates... I need 4 as I am building 2!!!
Part of these will become 1500 forward rear horns. Heavy and designed to keep the ash out.

David and Lily.

[tigermoth]

When I started on the 5" Lion I quickly came upon the first of the errors and posted a Question in M.E. and soon got a wonderful 3 page letter from a gentleman listing all the mistakes, I still have that letter somewhere.

Got quite disheartened by that and changed direction and built a boat, no not a model, I never think small, it was a 42ft steel cruiser with a Ford 6D engine, we will not go into that one on here though.

Norman.

[simplyloco]

Aug 24, 2020 6:43:33 GMT tigermoth said:

When I started on the 5" Lion I quickly came upon the first of the errors and posted a Question in M.E. and soon got a wonderful 3 page letter from a gentleman listing all the mistakes, I still have that letter somewhere.

Got quite disheartened by that and changed direction and built a boat, no not a model, I never think small, it was a 42ft steel cruiser with a Ford 6D engine, we will not go into that one on here though.

Norman.

By a strange coincidence I did the same thing! Bought a 42' hull and engine and we did the rest. 12 very happy years. Now sold to a happy Frenchman.

[tigermoth]

Always ready to make myself look a pillock, I bought the plans then thought about where do I start.

No internet in those days so in with both feet, buy a welder, grinder etc, start on the keel, learn to weld, make the frames on the factory floor ( my governor wanted to know what all the chalk marks were on the floor), build up the prow, do it wrong so do it again, get a mate with an engineering company to press the bow sheets to shape, get it inspected, then plate the stern and sides after working out the angle of the prop shaft, I could go on and on but suffice to say when it was all watertight with engine in and ready for the water the girlfriend and I split up and she wanted her half of the boat (in cash) so it was sold 75% complete, went to Wakefield.

 Forgot to mention that also went to night school to learn navigation, started a boat club in the marina, got the collage teacher to do a 1 year class every week in the marina club house, used to get a phone call about once a month from Keith (the teacher) Norman I cannot make it tonight will you take the class for me.

I then bought a 30 ft lifeboat and fitted that out, lived on it for a few years.

[dscott]

Our Washing Machine came from a couple splitting up.
Well its White and the reverse of a boat in that it has to hold water!!!
By the look of the house they had worked all the years and achieved the ultimate in everything.........
Then one of them must have got replaced with an UPMARKET MODEL...
Know the Feeling 17 years ago. Our Daughter loves any story relating to ending up with HER MUMMY.

Still going ahead with putting Jessie's valve rods in the center of the buckle to save wear.
No other mistakes to report so far.

David and Lily.

[stevep]

Not a major error, but I was marking out the frames for Doris, and when I came to the reverser stand, there was a mistake. The holes on the stand are marked as 3/16" in from each edge, with 1/2" between them. The material is 1" wide!

[uuu]

This is on Ken Swan's Jessie. The drawing is entirely accurate, but exposes a possible conflict between the wheel rim and the motion bracket.

Here's it as drawn:

DrawingConflict0 by Wilf, on Flickr

You can see the nice gap between the top right of the wheel rim and the diagonal edge of the motion bracket. But that's the rim - the gap is smaller at the larger diameter of the flange. And that's with the wheel at normal running height. If it's displaced upwards on full bump, then the gap disappears.

At least, that's what my re-draw shows:

DrawingConflict by Wilf, on Flickr

The thin blue arcs are the wheel rim and flange in normal running height, and the dotted arc is the flange on full bump. You can see it overlaps the blue diagonal.

I've drawn a curved cutaway that just clears.

And here's mine in the flesh, with the curved cutaway clearing the flange:

DrawingConflict2 by Wilf, on Flickr

I don't think anyone has ever reported this, so I suppose in use, the wheel never bumps up this high.

Wilf

[dscott]

Half round files at DAWN it is then!!! Thank you Wilf for this hint.

And on the sad day we hear that Jack Buckler has died. Sweet Peas will never be the same again.

David and Lily.

[classicbiker]

Hi All
I have taken on a part built Wessie 0-8-0 chassis from the estate of a former member of my club. I am just completing the cylinder installation and about to start on the joy valve gear. has anyone any information of drawing errors I should look out for.