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5" Maid of Kent Build Log

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William Ayerst04/02/2021 15:59:18
132 forum posts

Good afternoon gents, due to the falling through of a house purchase that would allow me to run my own 2-1/2" gauge railway and the distance to the nearest track, 2-1/2" is on the shelf in favour of my other joint-first choice of a 5" Gauge Maid of Kent.

My overall goal is to amend the platework around the cab, splashers and tender to represent an earlier SECR 4-4-0 - while the chimney is misplaced the rest of it is good enough for rock and roll for an E-class, and if I made the firebox round-topped it's good enough for a D-class.

As a first step - after speaking to Nick Clarke he has advised that the stephenson valve gear version has problems, with numerous solutions proposed each with their own idiosyncrasies. Does anyone know where I should be looking for the lesser of these evils?

Many thanks,

br04/02/2021 16:25:35
465 forum posts
4 photos

You could try asking on the Model Engineering Clearing House forum as there are members on there with the same loco.

It is a forum that locomotives seem to be the main topic of interest.


Nick Clarke 304/02/2021 16:35:21
1159 forum posts
48 photos

William -

The drawings include the KN Harris modifications for both inside and outside valve gears on additional sheets, however these are a total rework of the original design, and not just of the valve gear but the cylinder block and pipework as well to meet up with what KNH thought the design ought to have been like in the first place. This may not be necessarily correct.

Reeves will also sell you the additional drawings by Don Young for his revision of the valve gear, but again there have been criticisms of Don's valve gear designs, particularly for excessive lead.

You need to talk to people who have built a successful loco or who are sufficiently experienced to look at all the drawings and interpret them accurately - and I most certainly fit neither of these criteria!

If you look at the Model Engineering Clearing House website you will find a bigger concentration of locomotive experts than virtually anywhere else on the Internet.

Take care,


William Ayerst04/02/2021 19:02:17
132 forum posts

OK, I will do that and then report back here - thank you both!

Dave Smith 1404/02/2021 19:47:48
165 forum posts
25 photos


Agreed with using MECH for your queries, you will find good advice. I mainly post there as I am building a DY L & Y Aspinall class 27 which is a 5" gauge loco.


br04/02/2021 20:16:18
465 forum posts
4 photos

Hello Dave

I glanced in there by chance today and saw that thread - Aspinall caught my eye as something different.

Absolutely superb photos of outstanding workmanship.

Well impressed.


Jon Cameron04/02/2021 22:00:56
352 forum posts
113 photos


Would love to follow your build log either here or on MECH forum. MOK is a loco id love to build one day. The Minx might be made first. as I quite like its simplicity. If you were itching to get started on MOK then start with the tender while you can get the valve gear figured out.

From what I recall when I asked some questions either here or on MECH, the Stephenson's valve gear was terrible, the loco would run but it would struggle and be down half of full pressure when running round a track the loco didn't vent steam from the cylinders correctly and it would be a bit wheezy when it finally came into the station to swap passengers. (So I'm told). Link valve gear was better, simpler to build too, but on MOK it still wasn't 100%.

I'd message Julian Atkinson I think he's on both forums, he has a far better understanding of the valvegear, but is modest to say the least. They are online simulators that will allow you to run simulations of valve gears. These can determine how good the valve gear actually is. The key is getting equal openings for valve events, to both sides of the cylinder.

Will be following your progress even if I don't comment much.


julian atkins05/02/2021 10:41:00
1238 forum posts
353 photos

Hello William,

MOK. Where to start!

For the SR L1 (inside cylinders version) you have a choice of Joy valve gear or Stephensons valve gear.

The Joy valve gear version is regarded as very good, but not prototypical.

The Stephensons gear as designed by LBSC in the late 1940s is awful.

Hence, K N Harris, and later Don Young redid it. The K N Harris version is more of a complete rebuild, and has a peculiarity from memory.

The Don Young version is less radical and I would suggest be considered. See ME 7th and 21st November 1969.

The Don Young version could do with amending in some minor details as there is no suspension offset, and the lifting arm length may be wrong on the weighshaft, and I am far from convinced that the rocker arm bearing is in the optimum position.

As for Joy gear being not to prototype, there are lots of things about MOK that are not accurate, and to start with it doesn't have piston valves, so personally I wouldn't be too bothered about this.

The driving wheels are BIG!



Jon Cameron05/02/2021 11:04:31
352 forum posts
113 photos

My apologies Julian, got your surname wrong.


William Ayerst05/02/2021 13:42:55
132 forum posts

Thank you Julian, I'm sourcing the original LBSC series and will read through that. Would you recommend looking into the Don Young modified Stephenson's Valve Gear, or the original Joy Valve gear version? I'm going to be building it as facsimile of an SECR loco that's even further away from the L1 than LBSC may have sketched.

Given an equal balance I'd go with Stephenson's, but not if it's going to introduce problems - in line with Henry Greenly's view in Model Steam Locomotives "Form must folllow function, it doesn't need to be a slavish recreation of the prototype as long as it does the work" - at least, that's what I'm telling myself!

Also thank you Jon for your kind advice and info.

ps. I'll post this in the MECH forum and move the discussion there, if that is a better place...

br05/02/2021 13:49:41
465 forum posts
4 photos
Posted by William Ayerst on 05/02/2021 13:42:55:

ps. I'll post this in the MECH forum and move the discussion there, if that is a better place...


Definitely .

MECH is recommended for locomotives, TRACTION TALK for traction engines, HMEM for stationary engines.

From reading previous posts asking for advice.


Edited By br on 05/02/2021 13:57:11

julian atkins05/02/2021 20:46:54
1238 forum posts
353 photos

Hi William,

The late Percy Wood won IMLEC with a Joy valve gear inside cylinder MOK.

If the Don Young Stephensons valve gear version is improved it ought to be equal if not superior to the Joy valve gear version.

I had drives many times of the outside cylinder version and personally I disliked it. Tricky to drive and fire with the sloping grate and leaning over a long tender. But others with different examples had different experiences.



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