Loco at Marshalls Works 1906

[JasonBModerator @jasonb]

Posted by duncan webster on 08/09/2019 11:13:19:

…

Putting it another way, I think the engine's centre of gravity is too high for the distance between axles. They've addressed that by dropping the boiler, cab, gearing etc deep inside the frame, but maybe that means it's running on less stiff stub axles. (Do the axles run through the boiler's innards?)

….

Dave

Coupling rods only work if both wheels are on one axle. I'd guess that the boiler only just clears the axles, but from the photo it looks very close

They would also work if there were a solid shaft like a traction engines 3rd or 4th shaft with a gear at each end driving the left and right rear wheels which would then turn the coupled front wheels.

[Brian GParticipant @briang]

It looks to me that the boiler is at a similar height compared to the buffer beams as that on Sydenham (pictured), which has 4' drivers. If so there should be enough room for the Marshall loco's axles to be set 9" higher.

Brian

[JasonBModerator @jasonb]

Brain, did you see this photo from another post on TT?

Also did you get the works drawing numbers from the guy that offered ?

[Brian HParticipant @brianh50089]

Thanks very much Jason; no, I didn't see that the first time around and No, I didn't get the drawing numbers.

I'm going to contact the Gainsborough Heritage Society who own the drawings to see if they can help.

This engine is now on my list of ones to make when I've finished the two I'm working on at the moment. Come back in about 50 years!

Brian

[old martParticipant @oldmart]

It looks strange, as though the axels pass through the boiler, I think I would have rejected it too, if I had ordered a shunter and that monstrosity turned up.

[Brian GParticipant @briang]

Posted by old mart on 08/09/2019 16:27:33:

It looks strange, as though the axels pass through the boiler, I think I would have rejected it too, if I had ordered a shunter and that monstrosity turned up.

I'm not sure the Marshall looks that strange, to me it seems fairly conventional as traction engine locos go (in other words a bit like an Aveling geared 0-4-0), and such locomotives were almost the standard type for chalk quarries, perhaps because the drive on many of them could be disconnected to allow them to operate crushing machinery.

Hall & Co. had already operated one traction engine locomotive for over 30 years when the Marshall was supplied, and ordered another several years after rejecting the Marshall. They weren't even the only operator of traction engine locomotives in Croydon.

Brian (G)

[Brian GParticipant @briang]

I just now came across these two pictures of the Marshall locomotive in "The Chronicles of Boulton's Siding, apparently taken at Ashton before the locomotive became Marshall's shunter, and without the rectangular box (tank or ballast weight perhaps?) beneath the firebox smokebox (whoops). This came as a surprise as I understood that Hall & Co. returned it directly to the builder.

Did Marshall's try to palm Boulton off with the loco when it was returned to them? Whatever the reason, they provide a lot more information on the loco and its one-sided cab. Other than the length, which is given as 21' 11". (5" longer), the text confirms the dimensions given in "Traction Engine Locomotives", whilst adding that the water capacity was 230 gallons and the bunker 5 1/2 cwt. Despite the evidence of the photos, it is described as having a "solid fly-wheel 4ft.8in in diameter"!

Unfortunately the book and its reprint have been out of print for many years, so hopefully the copyright holders won't object to a single scan.

Brian G

Edited By Brian G on 09/09/2019 16:16:12

[Brian HParticipant @brianh50089]

Many thanks to Brian G for the pictures, very helpful.

Brian

[JasonBModerator @jasonb]

I think the one in fig 32 is the same image that was on TT but not as clear. Click image to see it larger.

 

Edited By JasonB on 10/09/2019 07:04:01

[Brian GParticipant @briang]

Thanks Jason, that is a much better reproduction than in the book. Does the posting on the forum confirm that it was taken at Boulton's siding?

Brian G

(Who is starting to suspect that the confusing number of Brians on this forum may be related to the age profile of its members ONS Graph ).

[JasonBModerator @jasonb]

No extra info on TT

[duncan webster 1Participant @duncanwebster1]

Posted by JasonB on 08/09/2019 12:35:22:

Posted by duncan webster on 08/09/2019 11:13:19:

…

Putting it another way, I think the engine's centre of gravity is too high for the distance between axles. They've addressed that by dropping the boiler, cab, gearing etc deep inside the frame, but maybe that means it's running on less stiff stub axles. (Do the axles run through the boiler's innards?)

….

Dave

Coupling rods only work if both wheels are on one axle. I'd guess that the boiler only just clears the axles, but from the photo it looks very close

They would also work if there were a solid shaft like a traction engines 3rd or 4th shaft with a gear at each end driving the left and right rear wheels which would then turn the coupled front wheels.

No it won't work like that, you need 2 coupling rods and an axle connecting the front wheels even if the rear wheels are gear driven from a cross shaft

[JasonBModerator @jasonb]

Duncan, I'm still having a job to understand why it would not work. Where does the second coupling rod go as you say two are needed?

My thinking is that as a front wheel is coupled to a rear wheel then the front will do whatever the rear one does. With both rear wheels being driven I would expect the two front wheels to be driven via the coupling rod each side be they on stub axles or a solid one right across.

I can understand the need to have some form of link from one side of the engine to the other but this only needs to be one of the axles or as I suggested a separate shaft driving the rear pair. More so on a loco where one cylinder could get out of phase with the other

Edited By JasonB on 10/09/2019 20:19:49

[Brian GParticipant @briang]

Posted by JasonB on 10/09/2019 20:11:24:

…My thinking is that as a front wheel is coupled to a rear wheel then the front will do whatever the rear one does. With both rear wheels being driven I would expect the two front wheels to be driven via the coupling rod each side be they on stub axles or a solid one right across….

Edited By JasonB on 10/09/2019 20:19:49

If you picture the geometry, with only one rod the front and rear wheels could in theory rotate in opposite directions. In practice, what is more likely is that the whole thing would stop at what is effectively top or bottom dead centre (on a coupling rod this would really be front or rear dead centre). The second coupling rod is "quartered" 90 degrees out of phase with the first, which is why railway locomotives are either left or right hand leading.

NSU bike and car engines used a similar system of two rods to drive their camshaft, although there was of course also a gear to halve the speed.

Brian G

Edit:  Don't look at the picture of the Aveling loco further up the page, on their 0-4-0 geared locos the side rods are just there to keep the axles pointing the same way, which says more than it should about the lack of rigidity of their design.

Edited By Brian G on 10/09/2019 21:30:07

[duncan webster 1Participant @duncanwebster1]

Brian has said it all, with the wheels not coupled by an axle, if the wheels on one side stop with the rod (singular) on front or rear centre, the front wheel doesn't know whether to go backwards or forwards when it all sets off again. With 2 wheels on the axle, the rod on the other side keeps it all going. Just try taking one coupling rod off a loco and turning one of the axles (wheels lifted off the rails obviously) It will soon get in a right tangle

[JasonBModerator @jasonb]

Got you now, basically if started at front or read DC then the pin could go up or down and coupling rod not stay horizontal

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