7mm Mickoo's Commercial Workbench

[James Fibbens]

Here's something a little left field triggered by a discussion today on Facebook about motor & gearbox clearances.

I've been meaning to do this for a long time now and today finally pulled the proverbial digit out. I'm not sure how or when others fit their motor gearboxes or test for clearances; but I frequently find that one orientation that's perfect for the chassis suddenly needs moving when you add the body, ash pan, brake gear.....insert excuse here......

Even when fitted you shouldn't really be soldering and spattering hot flux around drilling or grinding with it fitted, consequently it ends up going in and out during different stages of the build. In the case of the King I had to leave final positioning until the footplate (and at least firebox shell) was completed before I could work out clearances and final position, resulting in some hacking here and there to get the best position.

The upshot of all this was some sort of crash test dummy motor gearbox, one that you could install and work around, check clearances, grind, solder, drill and check side play with ill effect.

The first test one came out just fine, in this case the Slaters SG38 unit, my 1:1 unit has the older slightly longer motor fitted with the flat sides. Slaters latest drawing on their site shows a shorter cylindrical motor, which is what this crash dummy represents.

In time I'll do all the most popular ones I use, building up a stock of units I can just throw in with little care if they get damaged during the build.

I tend to make my driven axle rigid, especially if it's the rear one, so my motor fixings are really simple, two transverse bars that simply stop rotation of the unit under load, hence the solid gear box on the dummy.

Sometimes the motor is designed to float so I make a hook/claw that grabs one of the gearbox tubular spacers. Thus Mk II will have a slightly hollow gearbox with those spacers in the right place so you can fabricate the mounts with the dummy in place.

They also allow you to test several different types/designs before splashing out and buying one.

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That is an excellent idea. It's been a while since I built anything, however I recall a great deal of faffing about getting motors/gearboxes to fit into loco bodies.

Have you considered adding a couple of mm to the envelope of the thing, mainly on the motor, to provide a little bit of extra clearance for when the actual motor is finally installed? You could also add a range of dummy flywheels, although perhaps its easier to just use the real thing if your temporary motor shaft will allow it to fit.

 

[michael080]

Brilliant idea! Wouldn't that be something for the resources folder?

Michael

 

[Rob R]

Ideal for static showcase models!

Ideal for a certain Q1............

 

[oldravendale]

Brian

 

[mickoo]

That is an excellent idea. It's been a while since I built anything, however I recall a great deal of faffing about getting motors/gearboxes to fit into loco bodies.

Have you considered adding a couple of mm to the envelope of the thing, mainly on the motor, to provide a little bit of extra clearance for when the actual motor is finally installed? You could also add a range of dummy flywheels, although perhaps its easier to just use the real thing if your temporary motor shaft will allow it to fit.

Cheers.

I haven't added any additional clearance, that could be misleading in so much as, with the extra clearance modeled the unit might not fit, but to scale it would.

I don't think the printed motor shaft would take too much load from flywheels etc, so for Mk II I'm taking that off and putting a corresponding hole in the motor block, then folks can add a suitable metal shaft and attach a flywheel if they choose, it's more a durability than feasibility issue.

 

[mickoo]

Something else a little left field, more an example of opening your mind to other aspects for 3DP. I've shown the concept before but it makes no harm to show a further example.

In this case the Finney7 Hall, I used the same motor clip design (modified to fit the larger Maxon 10W on the ABC VML2) to hold the chip but added shallow troughs under the chip. This allows the cables to run up the back; in the case of the stay alive, from the top down and in the case of the motor feed, from the bottom up.

The stay alives are an odd shape and a bit of a pain to secure with little or no real flat surfaces, there wasn't room to add a pocket onto the motor mount (preferred) so it had to go somewhere else. The option for double sided foam was a consideration and I've got some good stuff that sticks well, too well sometimes; but it's not an ideal long term engineering solution in my mind.

Luckily the chassis rear stay has a small ledge under the cab so a 3DP pocket was drafted and glued in, there's a small cut out in the top front edge (rounded off to stop cable chaffing) to pass the cables through. There's just enough room for a loose but not sloppy fit for the stay alive, and once the body is added the cab floor acts as a lid to hold it all in place.

 

[mickoo]

Ideal for a certain Q1............

 

[Pencarrow]

Very restrained Mick.

 

[mickoo]

Very restrained Mick.

I try, but it's hard work

 

[mickoo]

Something less demanding across the bench, a simple repair job, which normally just go straight in and out and I don't do a photo shoot or post about it, but, it's a Britannia and those that know me (well) know I can't resist a Britannia.

In this case it's the Masterpiece rendition, and I have to say they have captured the look well. I've long coveted a good Britannia model and have been collecting photos, works drawings and visiting preservation sites when they have one stripped down, all with a view to making my own.

But I have to say the Masterpiece model questions that, cost wise they'll probably work out the same once you add your man hours in, bespoke castings and etch work. The only real difference being the journey of building your own.

Anyway, the model comes with two draw bars, a static close coupled (rigid) display one and a sprung extending type running one. Sadly the client was not aware of that and the model only came with the rigid one, consequently when it got to the first corner the draw bar pushed out and derailed the rear end of the engine. Luckily it stayed up right and only broke one set of tender steps off.

The remit was repair and fabricate a new flexible draw bar, simple enough to do, but it had to have two pivot points to work on sharper curves, one on the engine, one on the tender.

I reused the fixed unit securing plate after cutting off the old rigid draw bar, fashioned a pivot and made a new draw bar to suit; the photos are hopefully self explanatory.

The securing plate fits neatly into a cavity below the main tank, unfortunately the cavity doesn't allow access to fit the retaining screws on the rear of the intermediate buffers, so they've not been fitted as yet, possibly not at all. Given that access is near impossible I'm not sure how the screws were removed in the first place, possibly vibrated free.

It'll be hard to give this one back, slightly easier because it has the BR(W) deflector with square hand holds and I prefer the BR(LM) cupped versions.

 

[mickoo]

Onward with a new project, a second MOK King Arthur but this time with Maunsell cab and in it's last years of BR.

The slot and tab construction really does speed things up and you only need a few dabs of solder here and there to make it a nice solid build, that's especially noticeable on the bogies which are a master of art and metal work.

The castings are all good but like last time the corner posts are short at the base, however, unlike last time I already knew this so simply grafted some 0.5 mm brass on the base and dressed back.

The tank top and footplate (moved during the photos ) are still loose and the next stage is to seam solder the tank base and then give the whole lot a good clean before adding the remaining few pieces.

The gaps in the corner posts will get filled once the beading is on, first with 70° and then a few witness coats of filler primer and finally auto filler to get it all nice and smooth.

Once the tender is done it's back to the 4F and picking bits off the Bulleids.

 

[Richard Gawler]

The castings are all good but like last time the corner posts are short at the base, however, unlike last time I already knew this so simply grafted some 0.5 mm brass on the base and dressed back.

Please Mick, do you feed back this sort of information to kit manufacturers? I have sent off emails from time to time but so far only one manufacturer has written back and indeed thanked me.

 

[mickoo]

All bar done, the tool boxes are 3D prints but I've not fired up the spray gun to finish them off, I'll do that when I have a handful of bits for the engine to do at the same time, I also need to fit the water gauge pipe but that'll get in the way when smoothing out any gaps in the corner post after the filler primer witness coats are put on.

The tank top is still loose as I may need to get under the small deck where the tool boxes go when I'm filling the corner posts.

 

[mickoo]

Quicky little update on the DA 4F as I've a weekend away at GWSR hoping to photo shoot some future projects.

It does what it sez on the tin, so far all drops into place with little effort, typically with DA kit's its the hot wet bit up front that may have issues, but so far everything is just fine.

 

[Lancastrian]

Imposing on Mick's thread, and referencing back to one of his posts in January, we finally managed to source some lenses for the colour light signals.


Ian

 

[mickoo]

Small progress update on the DA 4F, the plan was to complete for Kempton but you don't need to be a rocket scientist to work out that's not going to happen So a new target date for Barnsley is now in force.

The earlier short chimney and dome are not in the kit so they'll need to be 3DP, as will the safety valve base; the white metal one got a little too warm when soldering it in place The snifting valves will also be 3DP as the kit ones are just brass blobs.

The etched front sand box fillers in the footplate will be drilled out and solid ones attached to the boxes below to give a better look.

There's quite a lot of seam filling to do and more edging strips to fit to close off gaps, hopefully the body well be complete this week; but I'm not holding my breath as 1:1 scale life has had a habit of thwarting plans of late.

 

[Pinkfloyd]

Nice.

 

[mickoo]

Sometimes things don't go swimmingly.

Whilst ultrasonically cleaning the King for delivery the firebox shoulders caught my eye so I blew a witness coat on...

The solder has sagged so it all needs repairing, needless to say it'll almost certainly not get done by Kempton.

 

[Dog Star]

Now that is a concern. Is the change in the shoulder surface a consequence of using the ultrasonic cleaner? Or is this an accelerated case of "creep"?

 

[mickoo]

Now that is a concern. Is the change in the shoulder surface a consequence of using the ultrasonic cleaner? Or is this an accelerated case of "creep"?

Not sure, my gut feeling is that the solder fillet behind wasn't thick enough and the metal flexed during rounding off (taking more solder than brass) and I never noticed.

I've either over rounded the shoulders (they match photos) or didn't have enough material behind (more than likely) to avoid cutting into the solder fillet, the front piece is a triple laminate but I think I needed about five in that area.

I'm going to back it with a slug of 70° and hopefully that'll give a more solid foundation to work with, touching it with 145° will just delaminate the whole lot.