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Drewry O4 in 7mm


Nicktoix
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Leeds MRS are building a 7mm model of Plymouth Friary engine shed. When complete it will be about 42ft overall with a 25ft viewing area.

 

There was a variety of locos allocated to the shed usually several of the same type. Most can be provided from existing kits, O2, M7 and West Countries. But one or two are harder to come by.

 

The shed had several B4s which when withdrawn were replace by Drewry O4s. The B4s I have already done. The only sources of the O4s is a Vulcan kit or Sang Cheng brass. Neither are easy to come by and given the variations in the O4s I decided to produce some etches and build them

 

Variations in O4s are numerous. The first few had different size wheels, different cabs and sandboxes. They are various footplate patterns i.e. diamond and (what I call) “flecked” .

 

The chassis was etched in 22th nickel silver and the body in 15th.

Nothing special about the basic chassis. The rear pair of wheels are compensated.

The reason for slot in the frames behind the buffer beams will become apparent later

drewry_1.jpg

drewry_2.jpg

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More progress on the brakes. I found the covers on the pivots quite distinctive so had to include them.

 

801287326_drewry3A.jpg.f74dac0b837ad410ff36d448a3e2323a.jpg The brake mechanism can't be seen under the loco but I thought I put it in anyway.

Should have added a piece of tube and a small nut over the leading pull bar to simulate the adjuster.

1440506860_drewry3.jpg.5b782cc397e13e7ac89ba5f9c19c2bf6.jpg

 

That is going to make fitting pickups awkward but ho hum !

 

Nick

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The steps are attached to the frames. The rear set are screwed to the rear spacer to allow removal to allow access to the drive crank. The front set are soldered on.

1388803223_drewry5.jpg.994e8e83a31c47c84eeafb791489133b.jpg

 

The sandboxes are moulded using a 3d printed master by innocentman of this parish. The air tanks are also mouldings from my own masters.

 

2132421036_drewry6.jpg.60be110ca047695e8ee4d55d7cafadbd.jpg

 

Plenty of room for the motor and gearbox. The buffers are from NMRS and fitted with oval overlays.
 

The reason for the slot in the frames now shows. A piece of wire is soldered to the end of the buffer shank and passes thro' the slot which stops the buffers turning.

1809367289_Drewry7.jpg.5f067bd0cbc58034e4e6bef23d1da736.jpg

Nick

 

 

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Nothing special about the wheels (Slaters do the correct pattern) or rods etc. I have forgotten to put the “hooks” on the buffer beams will have to scrape some paint off and do them later.

1937568343_drewry12.jpg.2c2841f9c251b963872788aa53b1b5a4.jpg2097036312_drewry13.jpg.2ddb39428389b6ca9e28b3ef0e19369a.jpg

And yes the pickups were awkward. Plungers would be better or leave off the brake gear.

1658862318_drewry22.jpg.5c66ef8a4a239d52f7a7e9ed9815d701.jpg

 

One problem I have yet to solve is the sandbox outlets

 

Prototype1621573710_sandboxproto.jpg.62cd4e7c3f42d50b44cb61e97ccabefd.jpg

 

Model

225924561_sandboxmodel.jpg.1c5371524946be00a094babbb488b5d5.jpg

 

The answer might be lost wax castings but that will depend on my ability to make masters and the price

 

Nick

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Onto the body. The cab assembly is straightforward with tabs fitting into slots on the footplate. The edges of the footplate are bent over rather than the more traditional valance arrangement. The slots are filled with solder from behind. I made them rather too wide but now corrected on the etch

1982165781_drewry14.jpg.2891c488c16e2ffcc87cdee7dbc1536e.jpg

1547894620_drewry15.jpg.309525035182ec28d416764627950e33.jpg

 

The engine casing was a bit of a challenge. I had two sets of body etchings. One I bent without annealing and as it shows in the photos it didn't bend well the centre of the bend is very different from the ends even though there are half etched lines in the bend area.

703006086_drewry16.jpg.1ea6b70fd0b4d5786fd8de51e72f9019.jpg

 

Annealing along the half etched lines with a small blowtorch made all the difference. I much prefer nickel silver to brass because of the ease of soldering but I suspect that these bends are easier in brass.

2062337026_drewry17.jpg.9c21dff0bfd405b454f84bf76c20ca21.jpg

Fitting the doors is easy but the handles are tedious and I added a small jig to the etch to make bending them easier. The radius on it is a guide to the radius of the front of the casing.

1394890814_drewry18.jpg.79f727efa35d10fa615629bb2a1adbce.jpg

Rapid progress now

 

NIck

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I etched the front separate to the main casing thinking that it would be easier to handle when shaping the front. This was a mistake as it was tricky to get the front and the main casing to match properly. The corrected etch has it all in one piece.

 

I soldered some 1.2mm copper wire in to joint between the front and the sides of the radiator to give some extra bulk where it would be filed back to shape.

 

1652892727_drewry19.jpg.44e627fc0eda5651b620ae1acb7b8da7.jpg

 

Once the casing is fixed it's then just down to detail and doing it in the right order. The cab door handrails go on before the cab floor followed by the control desk (all the levers fixed before fitting) and finally the control panel.

44443657_drewry21.jpg.83911906964a792d89a93c6a9c4a37a0.jpg

 

571466154_drewry20.jpg.4c74000e2ecb61bd991ddae7680a0ee1.jpg

 

There are a lot of lamp brackets especially on the southern region engines. The fillers are all brass turnings but could easily be made up from telescopic tube.

Don't understand the variation in picture size though.

Nick

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I missed some rivets on the cab roof and vent but have added these to the drawings. There should also be a strip of rivets under the roof and along the cab front and back. These have also been added to the etch

 

 

The roof is held in by tube in each corner of the cab and legs of wire soldered to the roof.

952882377_drewry23.jpg.6b2bb894daf4e9d1f456f0b0196fcf18.jpg

 

The wipers were so small they were a pain to make but worth it I think.

786385067_drewry24.jpg.5bba38ae0a74f999a1bf845dca11555f.jpg

 

 

So that's it basically. There is one challenge ahead which is the cab side windows. They stand proud of the cab and I have a plan to make them by layering etches and glazing after painting. It should work (says he hopefully).

1557358643_DREWRY28.jpg.063167bd407337568025e24412d85d9e.jpg

 

Hooks attached to buffer beam

 

1150684121_DREWRY27.jpg.b9124432d9525c2ac7152c5390c94ce7.jpg

 

Finished item but missing vac pipes to come from Laurie Griffin

1437005444_DREWRY26.jpg.ab790e4395dd78eba207b4546f07dcad.jpg

1728440003_DREWRY29.jpg.330c04eefa7b0061d312c336498345af.jpg

 

Sorry for the different picture sizes. They are all 8cm wide from Photoshop but here seem to have a life of their own.

 

NIck

Edited by Nicktoix
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1 hour ago, Enterprisingwestern said:

 

Drewry shunter and problem solving, what's not to like?, and as a bonus a tin of proper flux lurking in the background.

 

Mike.

But I only use it for occasional electrical work otherwise it's phosphoric acid at a suitable dilution.  I've probably had the tin of Fluxite for at least 20 years. I saw an even bigger tin recently that would probably life several lifetimes. 

 

Nick 

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  • 1 month later...
  • 2 weeks later...

Whilst gearing up for a bigger project, i thought i would bump this one up the build queue..

 

All seems to be going according to plan, etches all fit nicely..

 

Wheels and rods are the next step, i don't like the slaters crankpins as supplied so will be tapping then 10BA.

20190406_113119.jpg

20190406_113141.jpg

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