Member postings for julian atkins

Hi Simon,

Hacksworth valve gear does not produce near optimum valve events as the gear is notched up, due to it's simplification. A well designed Stephenson's and Walschaerts valve gear does provide such valve events.

When you also factor in the up and down movement of the driving axle on steam locomotives further compromising the valve events, then it is a poor substitute, except for it's simplicity and cheapness of construction.

I remember as a young Talyllyn Railway volunteer the late Ron Smith (TR Driver) adjusting the valve gear of TR No.4 'Edward Thomas' regularly. If Ron had properly understood the limitations of Hackworth valve gear it is arguable his efforts were in vain.

One of the supreme rare enjoyments of miniature locomotive driving is to have a loco with superheaters and a decent valve gear when you can open up the regulator and wind back the reverser to 20% cut off and drive on the reverser as per fullsize steam express locos! You adjust the reverser from between 25 and 15% cut off to cater for all track conditions and a heavy load of punters behind.

Very few miniature locos can be driven in this way.

Cheers,

Julian

I don't actually agree with Jeff re separate shut off cocks top and bottom of the gauge as in 3.5"g and 5"g these restrict the passageways, and in any event I have never found them necessary.

Cheers,

Julian (first of Jeff's 1 in 15)

Hi John,

It was told to me by Don Young after his Eastleigh apprentice days, and also related in his writings. Try greenish ended water gauge glass if you dare! I haven't tested it myself, as I have a large tin of gauge glass of various sizes, and I am quite happy with non- greenish glass ends that have never caused a problem!

Cheers,

Julian

Hi David,

Not sure why you raised this issue.

If properly made and fitted, a miniature water gauge is as easy to read as in fullsize. I have never used a commercial fitting, making all of mine. In 35 years I have never had a gauge glass break, and on the 4 yearly boiler hydraulic test they withstand a pressure of 1.5 x working pressure. I have followed a series of articles for many of mine from EIM many years ago.

Some miniature locos give a poor reading in the glass because of restricted water legs in the backhead and protrusion of the lower bushes and water gauge fitting. There is much turbulance of the water and foaming in this area of the boiler.

Reading the gauge itself is simplified by sticking a bit of white card behind with diagonal parallel lines written upon it in black ball point. A gauge glass against a black painted backhead is not easy to read.

I have never used schellbach glass (though I have a stock of it) because it is more brittle. Discard any ordinary gauge glass that shows greenish ends.

Cheers,

Julian

Edited By julian atkins on 01/02/2018 21:04:05

Hi Brian,

You have a relatively mass produced clock sadly of no great value. However, I would be as keen as you to get it running again and overhauled.

In my youth, a number of striking clock mechanisms (of no particular worth) were left in a tub of petrol, and the petrol squirted through all pivot holes with something like a turkey baster moving the pivots for and aft.

Later, other valuable movements were treated better and more thoroughly in subsequent years, and worn pivot holes rebushed, and damaged pivots replaced. But the tub of petrol approach is not to be dismissed if all pivots show no play in the pivot holes.

I can cope with English movements and their striking, and Longcase clock movements and their striking.

However, I failed miserably with an American striking movement on a rather nice family heirloom, and I failed to re-assemble the striking mechanism correctly after repairing some worn pivots and pivot holes with the clock completely dismantled. It runs ok and keeps good time, but I do not wind up the striking mechanism as it goes mad. Your project has inspired me to have another look at it after some 23 years.

But I think my point is that in these cheaper foreign movements is to be very careful what you do so far as dismantling and the striking mechanism. Others far more expert than me will no doubt give you far better advice.

Cheers,

Julian

Hi Peter,

For the final machining I use a long series end mill reserved for such jobs.

The frames are set up as you describe in the vertical mill with the frames horizontal and clamped together and bolted together. The horncheeks have already been machined before riveting to the frames. Less than perhaps 10 thou is taken off with the long series end mill to final size for the axleboxes to slide. The hornstay faces on the horncheeks are done the same time.

Years ago I used the same proceedure using the vertical slide on the lathe but the whole frame assembly had to be carefully repositioned for each hornblock pair.

What you want to aim for is as near perfect parallel and matching faces to the hornblocks/cheeks for the axleboxes.

Cheers,

Julian

Brian said "Surely miniature pressure gauges can only be used as simple indicators."

Not if you have FSD miniature pressure gauges!

These were all individually calibrated on Freddie Dinnis's dead weight tester.

Freddie also re-calibrated a number of commercial gauges on the club locos, painting out the old dial and re-doing them.

Cheers,

Julian

Hi Peter,

As the horncheek castings (whether of cast iron or gunmetal) will be softer than the steel frames, then I would drill the frames first, checking of course that where you drill will avoid any ribbing on the castings etc. Then spot through one hole at a time into the horncheek castings.

Add temporary bolts as you go de-burring the castings as you go if gunmetal (easy if for 1/8" rivets and use temporary 5BA bolts).

When you rivet up, add all the temporary bolts etc and do one rivet at a time.

Then I put the 2 frames outside facing outside if that makes sense, then mill the final working faces in the vertical mill.

Cheers,

Julian

Hi Nigel,

I agree the fullsize examples of the SR 'Schools' were and are still very impressive locos!

Unfortunately, LBSC's 'Roedean' is not well drawn, and IMO requires considerable input and detailed knowledge of the fullsize locos to put right plus the middle cylinder valve gear problems.

I may be coloured in my own opinion when the only example I saw close up on boiler test when first built had the firebox crown collapse. This was the LBSC version, not Clarksons.

Cheers,

Julian

Hi Nigel,

Roedean was originally described in English Mechanics with the rather less detailed description of construction that equally applies to Speedy also described in English Mechanics. ME subsequently acquired English Mechanics so then owned the copyright to Roedean and Speedy.

As stated above, ME reprinted the English Mechanics Roedean articles in recent years in 2011. Sadly the drawings especially the boiler were NOT updated though this was an ideal opportunity to do this.

In 35 years at this lark I have never seen a Roedean in steam on a track, and there are numerous complications with the middle cylinder valvegear and weighshafts and I would not consider Roedean by any stretch of the imagination to be a beginner's loco.

So I wish you all the best with a design that many have struggled with and many more simply avoided.

Cheers,

Julian

Hi Gary,

You need to obtain the relevant copies of LLAS if it was described in LLAS (Don Young's quarterly magazine). I will need to check if it was so described as a construction series in LLAS.

It is a fantastic loco to drive! I drove a rather poorly made example that nevertheless went like a rocket, steamed superbly, and rode like a bogie coach. It is an excellent design IMHO.

Cheers,

Julian

Hi James,

I will chip in with my usual advice for beginners not to choose a loco with piston valves or a boiler with a tapered barrel and belpaire firebox or combustion chamber.

The Black 5 and Brit have tapered barrels and belpaire fireboxes and piston valves.

The A3 has piston valves, 3 cylinders (which in the case of Don Young's 5"g 'Doncaster' are very expensive castings and very complex to machine), and the boiler has a short combustion chamber which complicates things.

Also bear in mind that a big ie long 5"g loco is uncomfortable for many people to drive and fire properly on a raised track, and on ground level 7.25" you are likely to have your face in the exhaust most of the time and many people also find the driving position uncomfortable. 5"g ground level is even more uncomfortable IMHO.

So best to join the Llanelli club, and find out a bit more first.

Cheers,

Julian

Hi Ryan,

You can use copper and I note you appear to have some big pieces noting how your firehole ring was turned out of solid. LBSC often used copper for the dome bush.

Personally, I hate turning copper, and drilling and tapping it even less. Save the copper for something else.

The fixings - you will need bolts to hold the dome to the dome bush. Brass screws are not strong enough. I prefer to have an unthreaded plain shank up to the bolt head which aids sealing. Commercial bolts in stainless will probably be undersized on the thread, and won't have an unthreaded portion, and the heads will be too big and will interfere with the dome itself. So I make them all myself out of stainless hex.

Cheers,

Julian

Hi Ryan,

I have always drilled and tapped the dome bush, regulator bush on the backhead, and regulator bush on the smokebox tubeplate before silver soldering.

I have always used hard drawn phos bronze for these bits. The usual tip is not to fully complete the tapping in case the threads get damaged by the long heat ups on the boiler and repeated dunking in sulphuric acid. I have never had this problem, but it might be more of a problem if you use gunmetal for these bushes.

The regulator stand is ok because the fixings are tapped into it and not the copper.

One of my least favourite jobs is making all the fitted bolts out of stainless for all the fixings.

Good luck!

Cheers,

Julian

Hi Ryan,

Your LBSC drawing on 15th January of the regulator arrangement would not be ok on a new build in the UK or Australia.

Instead of the copper backhead and smokebox tubeplate being threaded, bushes are now required which are threaded and silver soldered to these plates (the threading is only partly done before silver soldering the bushes to the plates).

The threaded smokebox end of the regulator steam pipe into a further threaded bush is quite tricky to do, and so I would also recommend John Baguley's arrangement.

I would silver solder a bronze tube to the smokebox end of the copper regulator steam pipe. (The regulator pipe should be of thick wall copper tube to accept the thread to screw into the regulator valve body). A screw driver slot can be added to the smokebox end which if bronze will be undamaged.

I am very interested in Pete's use of a turned PTFE bush to seal the smokebox end between regulator steam pipe and the wet header.

Cheers,

Julian

Does the Jodrell Bank thing still rotate on a track on ex-GWR Castle class bogie sets?

Cheers,

Julian

Edited By julian atkins on 16/01/2018 23:11:30

I am losing the will to live watching the second instalment.

What could have been a fine example of model engineering in the smaller gauges has become utter rubbish and drivel.

I am just about to change channels or fall to sleep.

Cheers,

Julian

Hi Simon,

3 litres is a lot!

Can you pour it around the base of neighbours' leylandii trees?

Cheers,

Julian

Hi Robin,

Fowlers Fury is quite correct that ordinary PTFE piston valves will leak on air, but should be ok on steam when the cylinders have warmed up.

Note also that I do not use steam oil when running on air, and use Singer sewing machine oil to lubricate the valves and pistons.

On the modeleng.proboards.com forum site, Roger Froud has developed a way of making piston valves with PTFE and 'O' rings underneath that seal on air and steam.

Cheers,

Julian

Hi Robin,

As you are probably aware the GWR Stars, Castles, and Kings have inside Walschaerts valve gear operating the inside cylinders and their piston valves.

The outside cylinders have their valves driven by cranked rocker arms worked off the valves to the inside cylinders.

The expansion links are very difficult to access, as is most of the internal valve gear without a major strip down of the whole loco. There is a substantial horizontal frame stretcher on the top of the frames which contains the expansion links and the intermediate weighshaft (which is split into 2 sections).

I presume your acquisition has piston valves, which are not easy to set accurately, and in any event there are peculiarities with the gear geometry that require subtle non centralising of the valves to get all the cut off and exhaust positions the same, compromising the admission points somewhat.

Any slack in the inside gear makes setting the outside piston valves difficult to achieve with accuracy.

Checking the valve settings the proper way is very involved on a GWR King, but essentially the same process is used as you would on a simple 2 outside cylinder loco with Walschaerts.

The complications arise because the expansion links are pretty much hidden, even with the boiler, smokebox, and front bogie off, and checking the correct setting of the 2 eccentrics and the correct length of the eccentric rods is similarly inaccessible.

If you say the loco runs on steam, I would give it a decent load on the track and listen.

You ought to have 4 distinct beats from the exhaust, each side of the loco exhausting at the same time, and you ought to be able to notch up the gear on the reverser to at least 25 % cut off with the beats still being loud even and clear.

If the beats are ok and you can notch up the gear then I think I would leave well alone. If however you are getting a 'whoosh whoosh' then there is probably something wrong with the piston valves leaking. (There is a further fullsize proceedure that can be used in miniature to check this further).

The exhaust pipes and passages on the GWR Kings are rather complicated and in miniature I have yet to see a 5"g example that really sparkled as it should, and with the distinctive GWR 'bark'.

Do not start to dismantle the loco unless you are absolutely sure what you are doing, and are absolutely sure you will be able to put it all back together again!

Cheers,

Julian