7mm Mickoo's Commercial Workbench

mickoo

Western Thunderer
Start of a new project, in this case a S&DJR 7F from David Andrews (DA). Nothing unwary so far, in fact a perfect Forest Gump build.....simple is as simple does.

Couple of days finds a rolling sprung chassis, lost time on setting up the angles for the mechanical horn guides, if you'd opted for the kit method you'd save a good part of a day really.

The front axle is virtually rigid with only a small downward deflection available and not sprung, the intermediates have the greatest amount of travel and the trailing is the traditional screw and spring height adjustment.

I'll add my usual 3D printed cosmetic horn guides with springs and hangers in due course.

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mickoo

Western Thunderer
Small update on the S&D 7F.

Tender goes together reasonably well, beware the etched copyright text under the coal space floor, it's right in the middle of the lower bend and leaves ugly creases when you form the bend. Either fill the text with solder first, file out the creases afterward or fill with coal, I tried a bit of filing and opted for the coal route.

Engine is defined as preserved in S&D blue, handy as it removes a lot of work from the schedule, no tank vents, no scoop or scoop handle, not that they were fitted in S&D days either. It does mean you can use the Fowler tender as is with a small boiler.

Tender springs were replaced with 3D prints, the kit ones are not too bad but take an age to clean up the mould joint line, I got bored quickly, drew one up in CAD and let the machine do all the hard work.

Engine brakes, oddly the leading axle brakes are trailing, there being two pull rods going forward, maybe to a cross shaft and linkage to the rear, maybe another set of brake cylinders, I don't have sight of a GA so cannot be sure. Either way there are no pull rods in the kit, these will be tomorrows first chore and then it'll be onto the cylinder block and slide bars. Sand boxes and pipes all but finish the chassis structure off; I'll worry about the motor mount once the body is more complete.

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mickoo

Western Thunderer
Another update on the S&D 7F, the next one will probably be the last.

Still need to add the front brake pull rods and motor mount to finish off the chassis then it's onward and upward above the footplate.

Couple of niggles to deal with, the footplate deck risers do not match the valance so you're left with a gap between them and the deck above the cylinders, solution, trim about 0.5 mm off the top of the valance over the cylinders to lower the deck. Same applies to the risers at the cab front, a bit harder to deal with this as you cannot take 0.5 mm off the main footplate deck to lower it.....it'll just make the gap at the front even bigger. You could taper the valance depth toward the rear, I've opted to add a sliver of brass in the gap and trim back (still to do).

The smoke box saddle sides are too small, no matter how you juggle it you're left with a gap between the smoke box wrapper and footplate, news ones to be fabricated tomorrow, there's also no saddle rear face in the kit, trace around the front one and cut out from scrap is the only option.

The pony truck horn guides and springs are a fudge, the top hate bearings supplied are not long enough to go all the way through the 3D printed fitting, and that is with the fitting already compromised and reduced in width from scale. The result is the wheel rear rubbing on the print and it wont take long to do some damage.

Solution, find some spare top hat bearings and turn down the stub so that the flange butts up to the print, you can see the adhesive joint as a black ring inside the bearing. After all that, you can barely see them .... pahh.

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Genghis

Western Thunderer
We have some 3/16" bearings that are much longer than usual (actually have about 3000 of them, but that's another story). Would any be useful or will you stick with your solution?

Cheers, Dave
 

mickoo

Western Thunderer
We have some 3/16" bearings that are much longer than usual (actually have about 3000 of them, but that's another story). Would any be useful or will you stick with your solution?

Cheers, Dave
David, that's very generous of you.

These are now stuck in place with Loctite as is the 3D print, so I'm kind of stuck with this set up, it works well even if a bit convoluted.

To be honest I was kind of making that bit up as I went along and didn't really have a final (clear) solution on how to affix the print. I wasn't sure if there was going to be enough meat in the printed axle box sides to go over the spigot; or if the print would work with such thin sides, a, printing, b, surviving clean up and c, fitting to the pony truck.

I built the truck out of the box and added the kit bearings, I tend to work best by seeing or doing, then added the 3D prints and it worked, so I just then added the flipped bearing.

Mick D
 

mickoo

Western Thunderer
If I'm honest I'd hoped to be further forward than this, but it's not far off completion, so this becomes the penultimate post.

I just needed some photos for the client so posted here as well as it's been over a week.

The chimney will be replaced with a 3D print and a hole punched in the smokebox top to suit. The dome on the other hand was rather pleasing and fit for purpose with minimal cleaning up or adjustment.

Basically it's lubricators, injectors, valve gear and back head to complete, all hopefully by the end of the weekend.

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mickoo

Western Thunderer
Last post, finally there....well almost:cool:, David Andrews S&D 7F, not without woe in the last week it has to be said.

Generally speaking the kit is good and goes together rather well and easily, there are a couple of niggles but nothing untoward.....until you try and fit the completed body to the completed chassis.....we'll get to that later.

Couple of photos of the bare chassis showing motor mount and motor gearbox fitted, a simple tab plate to support the motor and retainer bracket is all that's needed, not too tight as to allow the motor to float a little with the suspension. One thing I added was a strip between the cylinder block and valve slide block bracket, just means it all comes out as one piece, word of caution, that bracket is too wide and needs trimming back to fit inside the valances, best done before you fit the brass bracket that hangs down.

Test fit the valve stem and cast block early on.... and this bracket, chances are the stuffing gland casting is too far outboard and the valve block jams in the bracket, fortunately the cast holes appear off centre so it's a case of rotating the stuffing gland until the valve stem hole aligns with the previously reduced width bracket.

Watch out for the front stay that secures the frames to the body, note the two notches in the frame top, this is where the stay is designed to fit, two issues with this, it's to high and impacts the screw heads (there are half etched discs to locate cheese head screws soldered to the base of the front platform), second, the slots in the stay are no where near the the fixing screws, you can't get them wrong due to the half etched recesses to line them up. By now the alarm bells should be ringing, but onward.

The only other change to the frames was the replacement rear sand boxes, they are fold up etches but the edges are too short so you end up with gaps all round the edges, you can flood it with solder but you wont get crisp sharp edges.

Don't worry about the over long pins through the expansion link, just for test running and will be finally fixed and shortened on rebuild after paint.
The overall views speak for themselves, I replaced the chimney because the cast white metal one was a little oval and poor casting in the bore.

Now the elephant in the room, somewhere, some how there's a discrepancy in the footplate, you can't build it wrong, tabs and fold up design means it can only built one way, rather well actually it has to be said. There are two above footplate frame extensions and these have raised sections for the reversing arm pedestal bearings, there are also slots in the footplate for the outer ones and holes in the footplate for the drop link.

Unfortunately they're all in the wrong place, by about 2 mm. The pedestal bearings should be directly above the expansion link and the drop link should line up with the tail end of the radius rod (which appears to be the right length). The drop link is also too short, nothing you can do about that as the drop link and crank are all one L shaped etch.

The issue also moves forward, the front drop section is too far ahead of the cylinder block, the gap appears too big. On the face of it you only need to move the whole body back, but then the rear end doesn't line up, the cab step up is in about the right place in relation to the rear driver and all the frame bits internally won't line up. You can't do this anyway as the smoke box saddle front is a fold up section and correct width, behind it is the narrow running frames and cylinder block section, the body only fits in one place.

There is only one real solution, bin the drop links and crank, enlarge the hole in the footplate rearward so that it's over the tail end of the expansion link, make new cranks and drop links, both sides. Either way something has to be done as right now the drop links obstruct the expansion link and jam the motion solid.

Other than that, a nice model and simple build, the replacement engine springs and horn guides are in the printer and will be fitted once the frames are stripped down for paint.

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simond

Western Thunderer
Found 7200 (12” scale) in Quainton on Wednesday morning. A pleasant surprise!

boiler is currently out whilst the backhead is replaced, but everything else is there, bit late now, I suppose!

Atb
Simon
 

Deano747

Western Thunderer
Hi Mick, very nicely turned out too. Did you ever produce 3d wheel weights for the Slaters wheels, as I'd appreciate a set, if possible for my 52xx. PM me with a price please and I'll send the appropriate fee.
Many thanks
Rob
 

mickoo

Western Thunderer
Hi Mick, very nicely turned out too. Did you ever produce 3d wheel weights for the Slaters wheels, as I'd appreciate a set, if possible for my 52xx. PM me with a price please and I'll send the appropriate fee.
Many thanks
Rob
Thank you.

As it happens I did :thumbs:

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The bevel is on there (not leading which is flush), just hard to see in plain grey resin.

Let me get the last few bits wrapped up and I'll PM you.
 

mickoo

Western Thunderer
Finally back to the MOK King Arthur, the delay was due to the long delivery time on the ABC bespoke motor gearbox, understandable being a special one off under the past circumstances.

Never the less it has arrived and sat on the desk a few weeks whilst I cleared away other projects that had moved ahead. The motor is a Swiss Faulhaber and it's pretty big I have to say.

The kit is designed to drive the centre axle and we're not overly happy with that as the motor gears stick out from under the firebox and are visible below the boiler and throat plate, so were stuck with driving the rear axle and the problems there in.

Option 1 is a vertical motor, problem here is the top end is close to the firebox crown, very close, the motor tails will have to be carefully folded over and fit down the sides, but not touching, it can be done and there is side clearance to do so. The motor shaft untouched will juts clear the crown with mm to spare, I don't really want to grind much if any off the end of the shaft to be honest.

This option also has a large portion of the gearbox mass inside the ashpan, just makes it a fiddle to make and fit and then cut away the floor to clear what ever protrudes below, and there will be some which ever way you orientate the motor combo.

Option 2 is a near horizontal alignment, you cannot have pure horizontal as it will impact the boiler rear and trying to juggle the tail end of the motor into there whilst attaching the chassis will be near impossible.

If you kick it up a a few degrees then the tail end will clear the throat plate, but, the rear end then becomes close to the cab front, probably even passing through it and near touching the backhead interior.

The advantage is that it leaves much of the ashpan untouched, easier to fabricate and install and less gearbox sticking through.

There's a couple of stays not in the kit, a vertical throat plate type, the exact shape (usually inverted U shaped of some kind) I've not determined just yet and a large flat one: this spans between the throat plate and the small vertical one just to the rear of the leading driving wheel.

Finally, the front compensation beams and rear fulcrum rocking assembly have all been omitted, in it's place individual springing will be fitted. By good design MOK have placed suitable etched holes in the fold up bearing strips making them dual purpose if you so chose.

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Brian McKenzie

Western Thunderer
If shortening the outer end of the motor shaft would produce a satisfactory solution, then a fairly exotic suggestion would be to take the well protected motor/gearbox to a toolmaker who has a wire-cut EDM (electro-discharge machine), which can do the job easily, without producing heat. Heat being the enemy when grinding, not to mention stray dust.

There are lots of these machines about, including at Peco (who are hoping for a new Sodick brand machine).

Refer this recent video for a visit to their toolroom:
 

simond

Western Thunderer
In the last photo, the “ears” of the gearbox are the rearmost part, I can understand a little reluctance given the custom nature of it, but they could be cut or filed down to reduce the potential interference with the backplate?

From your other comments, that orientation seems to be the preferred option anyway.

Atb
Simon
 

mickoo

Western Thunderer
In the last photo, the “ears” of the gearbox are the rearmost part, I can understand a little reluctance given the custom nature of it, but they could be cut or filed down to reduce the potential interference with the backplate?

From your other comments, that orientation seems to be the preferred option anyway.

Atb
Simon
Simon, yes I could, I hadn't spotted that :thumbs:

The angled orientation has the least impact on the ash pan floor but is the harder of the two to make a motor mount up for and fitting of the body, requiring an almost vertical fit. The vertical mount is the easiest to make a mount for and fit the body on, but has the biggest impact on the ash pan floor.
 

mickoo

Western Thunderer
Apologies for the photo flood, there's a lot going on in this update of the MOK King Arthur. Brass is new plate work, red oxide new 3D prints.

Moving the drive to the rear axle allows us to add all the nick nacks around the middle axle and add some more detail. The dummy axle box covers need trimming to sit better before fixing to the brass bearings in due course. The firebox front has bowed in the printer at the top (curses...a replacement is now being done) so is only temporary.

The injector vacuum pipe will drop down in front of the firebox and head back along the side of the ash pan to the rear eventually. The new brake cylinder has both pipe fittings modeled, one will feed back to the reservoirs on the RH side of the frames, the other runs down the LH side to the cab and kicks outboard just about level with the reservoirs. Two straps need to be fitted to finish off the reservoirs.

The ash pan is the best of a bad place, I've only stuck in one side frame to get an idea of how bad/acceptable it will look, the real one sweeps up over the rear axle but this exposes the massive gear box and final gear and frankly there's no point putting in any pan floor as it'll only consist of two strips 2 mm wide each side.

The flat bottom pan whilst un prototypical does at least cover/enclose 80% of the gear box though the axle gear will still poke through even this. I may add a small cover to hide that as well. I did at least slope the upper flange so that it looks like the real thing through the oval frame opening. The front and rear will be enclosed with a 3D print of the front and rear damper doors, the brass will be brass sheet. I could possibly do the whole lot as a 3D print, something to sleep on.

Seriously underwhelmed by the VML2 gearbox and it's massive steam punk final gear.

At the rear end a new double decked drag box section has been added that matches the GA a little better.

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