0-6-0 Mamod Locomotive.

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
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Tony Bird
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0-6-0 Mamod Locomotive.

Post by Tony Bird » Sun Dec 14, 2014 5:08 pm

Hi,

Miniature Steam Railway’s 0-6-0 a modified Mamod though I suspect not many original Mamod components were used.

A few evenings ago I re-read Peter Jones’s very interesting booklet titled Miniature Steam Railways. “A Brief History”. The booklet deals with the modifications done by Terry Shirley and Jim Wilson to Mamod locomotives imported into the USA.

Possibly their last prototype design was for a 0-6-0 Continental style locomotive. Peter has made a very good replica of this model. On the original MSR design the cylinders drove the centre axle; Peter sensibly drove the leading axle as per Mamod. MSR had problems with the valve events on their model as they used their standard cylinders and port block. Moving the axle further away from the cylinder trunnion to allow for the extra wheel meant that the cylinders moved through a smaller angle and the ports opened less or barely at all.

The model I have been playing with needed bits painting and a day or so drying time, so I thought I would work out what size ports would be needed to dive a Mamod 0-6-0 with centre wheel drive. So a drawing was done positioning the leading wheel close to the port block and the centre wheel as close to the leading wheel as practical. Doing this increased the standard Mamod cylinder trunnion to driving axle distance of 45mm to 67mm, this reduced the cylinders operating angle from 24 degrees to 17 degrees. The lower angle meant that the Mamod’s original steam ports of 2.2mm with lap are reduced to 1.6mm with no lap. This should work OK, so I started to make some frames to see how well it would work.

The drawings.

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A new drilling jig was made using an old jig for making standard Mamod frames. A Mamod frames could have been used, only the holes that weren't to be altered were transferred to the new jig.

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Another jig was made so that the angle of the cylinder port block and reversing block could be altered to suit the new position of the driving axle.

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The port block jig is designed so that it can be used by lining up a centre line with the driving axle hole.

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Old jig and the two new jigs.

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Some recycled sheet steel were used to make some frames.

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The frames will remain rectangular until it is seen how well they work.

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A jig was used to position the steam and bolt holes for the cylinder using the driven axle hole as a reference.

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The posion of the holes was checked.

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Position of leading and driving wheels.

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Frames to date.

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The paint on the other project will be dry tomorrow so this playing will be put aside until some more free time becomes available.

Regards Tony.

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Post by Tony Bird » Tue Dec 16, 2014 10:42 am

Hi,

Further progress.

Using a jig to drill holes for the axles the same jig will be used to drill the connecting rod.

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Reducing the lap on the port block.

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Chassis to date.

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I will have so source some more second hand bits before the project can proceed further.

Regards Tony.

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Post by kandnwlr » Tue Dec 16, 2014 6:53 pm

Hope you are going to source some 2nd Hand stuff quickly so that we can see the pics during the hols. :D

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Post by Tony Bird » Wed Dec 17, 2014 8:59 am

Hi,

Hope you are going to source some 2nd Hand stuff quickly so that we can see the pics during the hols.

Unlikely given Christmas. To get a running chassis I need a pair of cylinders as they have to be taken apart those considered worn out would do and a set of wheels I have one set of wheels an axle and crank pins which are apart. Other than a boiler without a back head, a cab back and two roofs these are the only parts that I have that could be used to complete a model. I thought I might wait until the 16mm AGM and try and purchase a complete worn out Mamod.

Regards Tony.

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Post by daveyrd11 » Wed Dec 17, 2014 8:25 pm

Some very nice quality work, I'm looking forward to seeing how this develops.
Put that light out!

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Post by ace » Mon Dec 22, 2014 9:24 am

That's great Tony! I have a set of MSR 0-6-0 frames, cylinders, coupling rods and the overlays that I am turning into the same continental loco. Sadly they have been sat in my box for over a year before I have had a chance to do anything with them.

Having emailed Terry about his prototype, it was only recently that his 0-6-0 would work as he was playing with the port events. This is something I have worked out, surprisingly the same as yourself.
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Post by Tony Bird » Mon Dec 22, 2014 6:07 pm

Hi Mark,

Given that oscillating cylinders have little or no lap, they will open to some degree regardless of actuating angle. Mamod cylinders as as made at least the older ones have quite a lot of lap so with a very much reduced operating angle would not open much if at all. See Attachments.

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Which I hope explain what increasing the port size and reducing the operating angle does. The red circles not very distinct represent the cylinder's ports.

Regards Tony.

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Post by Tony Bird » Tue Dec 23, 2014 9:03 am

Seasons Greetings,

My workshop won't be used over the festivities so it was given a bit of a tidy up. In doing this an old split Mamod locomotive cylinder was found It is beyond practical repair but it could be used to see what the chassis would look like with a cylinder fitted.

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As can be seen from the photograph with a flange less driver if found necessary the wheels could be moved closer together so increasing the port opening.

During the clean up a number of wheel castings came to light that could be used on the chassis.

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The backs and edges of all the wheels have been roughed out along with the face of one wheel. These wheels could be machined to Mamod size and their throw is large enough for a 19 mm stroke. So if suitable Mamod wheels don't become available they might get used for the project.

Everyone have a great time over Christmas.

Regards Tony.

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Post by KNO3 » Wed Dec 24, 2014 10:28 pm

Very interesting conversion and especially your comparison of port sizes and cylinder angle. I really like these custom 6-wheeled Mamod locos.

And merry Christmas!

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Post by Tony Bird » Thu Jan 08, 2015 6:06 pm

Hi,

Thanks to a member of the forum (thanks Chris) who sent me three axles and wheels I have been able to do some further work on the 0-6-0 chassis.

The first job was to try out a suggestion from a member of the forum. His suggestion was to use the keeps that stop the bearing revolving to hold the wheel/axle/bearing assembly in place so that they could be removed from the frames without separating them. It needs some tweaking but the idea works really well!

Filling the bearings of the 'new' wheel assemblies.


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Modified bearing slots.

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Later frames will have the screw hole moved for the frame spacer so a straight keeper can be used. These frames are for R&D so probably wont be fitted to a model.

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Keeps used.

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Wheels fitted to the assembled frames.

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The jig that was made to drill holes in the frames for the axles was used to drill the connecting rod.

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Frames to date.

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Until I get some working cylinders and seals for the port blocks no further work will be done. Maybe I will find some used ones at STIA.

Regards Tony.

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