Jump to content

GNRi Class V Merlin Gauge OO Build

Rate this topic


Recommended Posts

This is the build of a Studio Scale Models Kit of Merlin, building it to Gauge OO and not decided on suspension type yet!!

Main chassis components & coupling rods removed from the fret, edge cusp removed and ready all for soldering.


Soldering the frame spacers to alternate frames, the ash pan sides and the coupling rods.


The frames are then bolted together with screws supplied in the kit and then all soldered.


Note;- **** The Motion Plate frame spacer, Part No. 108 - is in upside down in this sequence of photos. I will show it in the correct orientation in later photos when the error is fixed*****

Captive screws and nuts are also fixed into the frame spaces to hold the front bogie and body onto the chassis.


Crosshead parts ready for soldering, the long bits are a jig when soldering the parts together with a bit leftover as the sliders! see below.


Jigged up and parts being soldered in.


Soldering complete.


Then the jig ends are cut off to complete the crossheads, a pit of filing and clean up is required.


Motion brackets, cylinder wrappers and ends removed from the fret, cusps removed and ready for soldering.


Motion brackets jigged up on a piece of MDF for soldering.


Bracket folded n soldered.



Preparing the relief valves for the cylinder front covers- these small bit of wire have a tendency to float out while soldering the covers on so I put a burr on one end with a hammer, thread the wire through the hole from the inside and solder on the inside, this stops the wire popping out later.


Embossing the bolts on the covers.


Inner cylinder wrapper bent to shape around a 6mm brass bar and ready to be soldered.


Solder applied to inside of the wrapper, then the top is soldered onto the bracket first, then the wrapper is forced around the bracket, held with a strip of wood to save the fingers and the bottom soldered.




Front cylinder ends soldered on.


Bogie front splashers were bent up and soldered to the chassis, gusset plates also done at front and at the firebox.


Crosshead slide bars being folded up and soldered.


Installing the slide bars into the back of cylinders and the motion bracket. A bit of fettling was required to the crossheads to ensure they could move freely in the slide bars, this was done before soldering the bars in!


Outer cylinder wrappers bent up and ready to be soldered as per the inner wrapper method.


Wrappers on and whole assembly cleaned up.










Edited by murrayec
Part 108 in wrong orintation
  • Like 8
  • Informative 1
  • WOW! 5
Link to comment
Share on other sites

I Fixed up that frame spacer and did a bit more of the build.

De-soldered the frame spacer, also the bogie mounting plate to facilitate bending the frames to sneak the spacer out of it's half etched tabs!


Now its soldered back in the right way up.


Bogie parts prepared for soldering up.


Main parts folded and front axle hornblocks prepared with a bit of solder to sweat them onto the frames.


Frame soldered and stretcher parts ready to be soldered in- oops! upsidedown parts again- that main stretcher is in the wrong way up and I did not notice until the bogie was complete but it was easy to rectify.


Stretchers in and now the outside frame laminates are prepared to sweat solder them on.


Soldered on and the iron is run around the edges to fill any gaps.


Bogie cleaned up and holes being sized for rear axle bearings to be soldered in.


This is the bogie end plate for the compensation beam a 10BA screw is the rubbing pin which is bolted through the plate, this allows adjustment of the beam.


After soldering the nut onto the plate a 10BA tap is run through to clean the threads.


The bogie pivots on a 3mm long 3/32'' tube fixed with a 10BA bolt to the bogie fixing plate on the chassis, the tube is not supplied in the kit. Thin tube is easy to cut with a craft knife by rolling the tube with the knife blade, after a few goes the tube eventually cuts- light pressure should be used otherwise the tube will deform at the cut.


All the bits to fit the bogie to the chassis. Note the bogie main stretcher is now in the right way up!


Test fitted.


After a good rummage through the spares box I found a 'Puffers' Flexichas Hornblocks and bits, this will do the front driver axle bearings and compensation beam.


Chassis holes cut out and hornblocks made up.


Coupling rod holes are sized to fit the Alignment Jigs.


The rear axle bearings are soldered in and all is jigged in the chassis.


The hornblock frames are set at the top of the chassis opening and then soldered in on the inside.







M-34 20210501_123143.jpg

  • Like 6
Link to comment
Share on other sites

@Galteemore That first photo is pretty handy after a bit of contrast adjustment a lot of cab detail can be seen.

Getting ready to do the compensation beam so we need wheels n axles. Alan Gibson wheel sets came with the kit- not my favourite type, with their push on axles. I prefer squared end axles and screw on wheels, easy to put on & off as the build requires, where if one pushes the Gibson wheels all the way on their a devil to get off! But I do have a trick for working with these.....


.....the trick is to make up 1/8'' dia brass axles with the ends filed down slightly in the lathe so that the wheels are a slight push fit and then easy to get off again, I estimated the length required- 24mm and made them to this length which can be used to size the final steel axles.


As you see in the photos the drivers come with separate crankpin wheel boss! This adds 2.14mm to the axles which will push out the rods by the same- Not sure about this and have an enquiry out to SSM.


.45mm NS wire keepers soldered onto the bottom of the hornblocks of the bogie front axle.


Axle'd up.



Front axle compensation test, the axle pivots on the central bearing downstand from the stretcher.


All wheels on.


In this photo one can see the 3mm long tube above the rear bogie wheels that the bogie pivots on.


Parts for the comp beam- 1.6mm brass wire beam, front screw plate from the kit, 1.6mm brass cross pin, 1.6mm internal dia brass pivot tube, and little bits of tracing paper with holes in, which will be used while soldering in the cross pin to stop solder wicking through into the tube- we want that to pivot!


This is a handy tool for punching holes in things, I got it in the Art & Hobby shop- in the paper card section, with heads of 3 hole sizes and 3 dome sizes.


Screw plate soldered onto the front of the beam first.


Then it has it's 10BA screw fitted and threaded into the chassis, which will only work with the front driver axle removed. The bogie mounting screw also has to be filed down flush with it's corresponding nut, otherwise the end of the screw fowls the beam! The cross pin is soldered on the outside of the frames with the tube threaded on and the paper washers on each end of the tube against the frame.


Then the front axle is fitted and the beam soldered under and to the pivot tube, soldering at the top is easiest. One can now see the screw at the beam front protruding through the fame stretcher which will act on the bogie creating a 3 point compensation suspension system with the front drive axle.


Wheels back on.


The beam front screw is now adjusted to level up the wheels, the front driver axle ends up in mid position on the hornblocks. After running and weight tests a splash of Loctite will go on the screw.


Next will be the gear box and motor......


.........in a while! other projects to be getting on with!




  • Like 4
  • Informative 1
Link to comment
Share on other sites

It looks like the loco may have been supplied with a set of plain driving wheels and outside cranks intended for a GWR outside frame 4-4-0.

There is a 4880G 6'8" spoke outside crank driving wheel listed in the Alan Gibson catalog with are used with the 5000 outside cranks and extended axle.

The driving wheels listed OC are for outside framed locos, the outside cranks and extended axles are supplied as a separate part


  • Informative 1
Link to comment
Share on other sites

53 minutes ago, Mayner said:

It looks like the loco may have been supplied with a set of plain driving wheels and outside cranks intended for a GWR outside frame 4-4-0.

There is a 4880G 6'8" spoke outside crank driving wheel listed in the Alan Gibson catalog with are used with the 5000 outside cranks and extended axle.

The driving wheels listed OC are for outside framed locos, the outside cranks and extended axles are supplied as a separate part


@Mayner I reckon you right there, I'll wait for SSM to come back on my query and see if they have replacements drivers.


Link to comment
Share on other sites

  • 2 months later...

After getting the replacement wheels I decided to finish off the chassis bits before doing the gearbox & motor!

The right wheels this time, I got them from Alan Gibson in the end- after weeks of telephoning and just getting the answering machine.....


The crankpin BA screws were installed, all was assembled and wheels quartered to broach the coupling rods for free running. In the foreground is the brake parts, connecting rods & wheel weights all cleaned up, holes sized and ready for folding/soldering.


Connecting rods and brake shoes folded/soldered, yet to be cleaned up.


These are the break hanger brackets being folded up. Their threaded onto the .5mm wire pins through the chassis for hanging the brakes off.


Now to solder them on to the chassis.


The rear brake frame bracket are fitted onto a .9mm brass wire through the chassis brackets, I left the brackets free on the rod to be soldered when the brake pull rods are on for positioning.


.5mm wire pins soldered through the chassis frames with the little spacer brackets threaded on and soldered.


Next the shoes, pull rods and beams were joy rigged in place and soldered up- very fiddly as one wants no contact between the shoes n wheels which will cause a electrical short. Those rear brackets are now soldered to the .9mm brass pin. The back end of the pull rods and the top of the shoe hangers are not soldered so that the assembly can be removed.



And removed.


Wheel weights being epoxied on.


The connecting rods were cleaned up and the crankpin end generously broached as these will be at quite an angle out to the crosshead. Wheels back on and time to assemble the gear.





The connecting rods are at a crazy angle, causing binding on the crankpin bearing and the coupling rod, the bearing is not long enough, which also needs a washer and a bit of free space for this angle. I'll make up a bearing to suit.




  • Like 9
Link to comment
Share on other sites

On 16/7/2021 at 8:50 AM, murrayec said:




The connecting rods are at a crazy angle, causing binding on the crankpin bearing and the coupling rod, the bearing is not long enough, which also needs a washer and a bit of free space for this angle. I'll make up a bearing to suit.




One of the challenges of building an Irish Broad Gauge steam locomotive in OO gauge!

On the majority of outside cylinder steam locos the conrods are on the outside of the coupling rods but not on some outside cylinder 4-4-0 classes including the GNR Compounds and Metropolitan 4-4-0T.

It basically leaves the builder with the choice of cranking the coupling rods to avoid running problems or fitting the conrods on the outside of the connecting rods and using a longer crank pin bush.


Edited by Mayner
  • Like 1
  • Informative 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

Terms of Use