Duncan's 7mm Workbench - Connoisseur 4F Tender Cab

[Fastdax]

Brakes and Valve Gear.

 

And also footplate! I made up the basic footplate at this point, as I like to make sure everything fits under it without fouling.

 

It's a 2-layer lamination, with the edges of the lower layer folded down for the side valances.

 

 

I used the chassis attachment bolt holes to bolt the layers together once accurately aligned.

 

Then it was clipped and edge-soldered, inside and out. I didn't attempt to sweat together such large pieces. Running solder into the edges seems to work fine.

 

 

The bottom of the footplate:

 

 

And the top. I placed it on a bit of mirror glass to make sure it was flat (which it was, after a little judicious twisting).

 

I left the footplate soaking in hot water for a good long while, to attempt to flush out any phosphoric acid flux trapped between the layers. The slots for the bodywork are not soldered yet, so hopefully any flux can escape through them before it gets sealed in.

 

 

The buffer beams are each a folded lamination.

 

 

The footplate is attached to the chassis with a couple of 6BA nuts and bolts. I positioned it carefully and tack-soldered the nuts to the footplate. Lots of oil on the bolts stopped them being soldered solid as well. Then, with the bolts removed, I flowed solder round the nuts for a permanent join.

 

In this picture you can also see the brakes and guard irons that I previously attached to the chassis.

 

 

Here are some of the bits for the left-hand side valve gear. I did a dry-run with all these parts to make sure I knew where everything went.

 

The cylinder blocks and motion-support brackets bolt to the chassis, which I like.

 

Also on the chassis now are the rear sandboxes with their lids.

 

 

The first valvegear job was to solder (with 70degree alloy) the two parts of the motion-support bracket together.

 

 

Here's the chassis with the non-moving parts bolted in place. The slide-bar (nickel-silver bar with a hole in) is just pushed into the cylinder block for now, as I'm not yet sure of its final position.

 

I glued the front of the cylinder block on with Rocket Hot CA glue, as I don't think it would be easy to get a consistent, thin solder joint between such large lumps of whitemetal.

 

 

In this photo you can also see the water tank balance pipe soldered to the chassis.

 

Edited December 30, 2023 by Fastdax
Reinstating photos.

[Fastdax]

Here's a question that someone may be able to help me with.

 

When this Deeley 0F Dock Tank is finished, I want it to have DCC sound. I can't see the exact loco listed by Loksound or Zimo (since none exist any more to record!), so what would be a likely alternative?

 

I guess some small 2-cylinder Midland tank engine would do, but which one?

 

Any information appreciated.

 

Duncan

Edited June 28, 2016 by Fastdax

[ROSSPOP]

Well my choice would be:

 

Zimo MX645 sound decoder with either  LMS 1F or 3F sound file...... all from Digitrains....

 

 

Regards

 

 

John

[sir douglas]

jinty?

[Fastdax]

jinty?

 

One point against this is that I already have a DCC sound Jinty. I don't really want two locos sounding the same!

[Fastdax]

Well my choice would be:

 

Zimo MX645 sound decoder with either  LMS 1F or 3F sound file...... all from Digitrains....

 

 

Thanks for the suggestion John.

 

I can't see a 1F option listed - could you point me to it please?

 

Thanks,

Duncan

[ROSSPOP]

Hi Duncan....

 

I hope I hav`nt misled you.....I`ve just gone through Digitrains products and you are right...the 1F aint there !!!!    BBBBut it was !! obviously some time ago attached to a Bachmann 1F loco.   Give them a ring and check they are very helpfull.  I was planning to use it on a yet unbuilt 7mm 1F !!!!!

 

I`ve only ever used Digitrains sound files for my 4mm( LMS) locos and am very impressed.

 

I`ve got the 3F sound file and the ZS006M 2P/3F for zimo which I am switching over to my 7mm Johnson 1P.

 

John

[Fastdax]

Rods and Wheels

 

The coupling rods are made up of 2 layers of nickel-silver. I opened up the end holes with a taper broach until they just fitted over the pins on my axle jig.

 

While they were in place, a tack solder held them together. They could then be removed from the jig and edge-soldered.

 

 

Here are both coupling rods on the jig, soldered and cleaned up:

 

 

In my Jinty build, I replaced the Slaters 12BA crankpins with 10BA brass countersunk screws. I wanted to do this again for the dock tank. However, the instructions suggest that the front crankpins are inserted from the outside to a captive nut on the back of the wheel.

 

Looking at the diagram, it seems that this arrangement has, sitting on the surface of the wheel: the combined thickness of a bush, a washer and the screw head.

 

So I decided to turn things round and insert the 10BA screw from behind, as usual, and screw on a reversed, tapped bush. This should save the depth of the screw head in the tight space between wheel and crosshead. The instructions do say that you may need to move the cylinders outwards using packing shims if this is a problem.

 

 

For comparison, the instructions have the crankpins on the rear wheels inserted from the inside as is normal.

 

 

I cleaned up the backs of the wheels and drilled the wheel crankpin holes 1.2mm in the pillar drill. Then I tapped the holes 10BA and countersunk the back to take the heads of the screws. A bit if superglue holds them in place.

 

 

To help get the bushes on and off, and to give something to grip while tapping them, I filed a couple of flats on the bush flange. These shouldn't be noticeable on the finished model as the rears will be hidden under the eccentric crank and the fronts are behind all the motion.

 

Once "flatted", I could grip the bushes in small pliers and work a 10BA taper tap through.

 

 

So, now I could assemble the basic 0-4-0 rolling chassis. The rods were a tight fit over the bushes and, initially, showed a tight spot. A little gentle broaching of the holes produced a free-running chassis.

 

 

 

Like this:

 

 

Edited to change 14BA to 12BA.

Edited December 30, 2023 by Fastdax
Reinstating photos.

[Guest Isambarduk]

"I replaced the rather weedy Slater's 14BA crankpins with 10BA brass countersunk screws."

 

They are not 14BA but rather they are 12BA and they are far from weedy in this application. 

 

In fact, if you ever manage to shear off a 12BA steel screw/crankpin you should consider yourself jolly lucky that it acted as a 'shear pin' and that more serious damage was not done.  Of course, with the top hat bushes in place, there is no way that you are going to bend the screw so, all in all, 12BA is just fine. 

 

I use 12BA on all my loco wheels, Slater's or 'home-grown', and they are perfectly adequate for industrials, on the one hand, and pacifics hauling twelve coach trains on extensive garden railways on the other.  A long standing urban myth seems to have grown up about the need to replace 12BA crankpins with 10BA ... but there really is no advantage.

 

David

[Fastdax]

"I replaced the rather weedy Slater's 14BA crankpins with 10BA brass countersunk screws."

 

They are not 14BA but rather they are 12BA and they are far from weedy in this application. 

 

In fact, if you ever manage to shear off a 12BA steel screw/crankpin you should consider yourself jolly lucky that it acted as a 'shear pin' and that more serious damage was not done.  Of course, with the top hat bushes in place, there is no way that you are going to bend the screw so, all in all, 12BA is just fine. 

 

I use 12BA on all my loco wheels, Slater's or 'home-grown', and they are perfectly adequate for industrials, on the one hand, and pacifics hauling twelve coach trains on extensive garden railways on the other.  A long standing urban myth seems to have grown up about the need to replace 12BA crankpins with 10BA ... but there really is no advantage.

 

 

Thanks for the correction David - I've edited my post to change 14BA to 12BA.

 

I take your point about 10BA brass being no stronger than 12BA steel. For me, the point of changing is mostly that I can tap the Slater's crankpin bushes and screw them onto 10BA pins with no need for extra washers or nuts. In cases with restricted clearence, like on the front wheels of this dock tank, the few extra thou is very useful.

 

Duncan

[Fastdax]

Cross-heads and Connecting Rods

 

The crossheads and their covers are nice lost-wax brass castings. A soak in Barkeeper's Friend brought them up quite shiny.

 

That's not my best toothbrush.

 

 

The two items on the left have been cleaned up with assorted needle files to remove flash. The piston rod on the right shows the "before" state with moulding lines top and bottom.

 

 

The connecting rods are 3 layers of nickel-silver, soldered together just like the coupling rods.

 

 

A 12BA steel bolt inserted from the back holds the connrod into the crosshead. The nut on the front has been cropped and filed flush. It doesn't resemble the real thing much, which had a horizontal strap across this area. I may add something later to represent this.

 

It's a shame that the hole in the front cover was already too big to tap 12BA as this would have removed the need for a nut.

 

While bolted up, I ran a bit of solder into the front cover joints to hold the crossheads together permanently. The conrods can still be removed by unbolting the pivot screw..

 

 

I added a "set" to the connrods to allow them to drive the crossheads which are a bit further out than the wheel crankpins.

 

 

While this was going on, I ran-in the motor using this extremely high-tech rig:

 

 

Half-an hour in each direction on 6V then 9V should see it nicely bedded in. Then I repeated this with the gears in place in the gearbox and a little ceramic grease on the teeth.

 

Of course, then it was just a quick bit of assembly away from being able to try out all the bits together.

 

The instructions suggest using two crankpin bushes on the rear pins but I found that a single bush screwed on gave enough depth for the coupling rod, connecting rod and a tiny bit of side-play.

 

The front crankpins had to be cropped and filed flush to the bushes to provide clearance behind the crossheads. There's just the proverbial fag-paper's thickness between the two but luckily this seems to be fine as neither crossheads nor wheels have any side-play.

 

So I arrived at this happy point:

 

 

Sorry about the intrusive Jessie J soundtrack in the background! Funny what you only spot later ...

 

It shows the motor running on 9V and being gradually turned down. It finally stopped at about 1.8V.

 

The big brown bottle of glue is to provide a bit of counterweight for the whitemetal cylinders, which have a tendency to tip the loco forwards in this state.

 

I'll do a bit of running-in while I get on with the rest of the valve-gear.

Edited December 30, 2023 by Fastdax
Reinstating photos.

[Fastdax]

Tethered Bearings

 

One thing that became apparent while running-in the 0-4-0 chassis with rods is that the front bearings were rotating in their elongated chassis holes.

 

This isn't necessarily a Really Bad Thing but I wanted to stop them turning so that there's no chance of the chassis frames cutting into the sides of the bushes.

 

So I used a technique that I gleaned from Jazz of this parish and stopped each bush rotating by holding it with a length of wire rod that rides in a hole in the bush.

 

I drilled out a 0.6mm hole in each bush, to lie just inside the frames.

 

 

 

Then I made up two 0.5mm nickel-silver wires with a small L-bend at one end, which locates into the hole in each bush. The wires are soldered to the inside of the frames and are as long as practical.

 

They are fixed in place with a small amount of spring holding the bush at the bottom of its travel. This way, the wires shouldn't come out of the holes when the axle tips to its maximum deflection, but the springing of a 0.5mm wire isn't enough to lift the body up off the pivot bolt.

 

 

Another view, this time from above.

 

 

Now the bushes don't rotate and there's the added benefit that they stay in place when the axle is removed, which makes re-assembly easier.

 

It only took an hour or so to do this and well worth it, I think.

 

Edited December 30, 2023 by Fastdax
Reinstating photos.

[Guest Isambarduk]

... and you will have introduced some degree of springing to help ensure that all four wheels stay in contact with the track.     David

[Simond]

David,

 

I have used the "10BA and tapped bushes" approach on all my locos, I think the bushes look better than 12BA nuts, or the slots in the screw heads, and the whole thing feels more "engineered", somehow. On the driving axle, I usually turn some specific bushes, to try to make them look more prototypical, but I have been known to simply use a pair of tapped Slaters' bushes back to back (narrow ends together).

 

I usually use steel screws, and Araldite them into the wheels.

 

On the 1366 pannier, I had to counterbore the coupling rods to recess the flanges of the bushes to get sufficient clearance behind the crossheads. Entertaining palaver that was...

 

I have no doubt that the 12BA screws are strong enough, but I think the 10BA's have it for a stiff assembly.

 

Best

Simon

[Guest Isambarduk]

Yes, Simon, I've done all that ... but with 12BA.  I, too, make my own bushes to suit the particular application and I usually machine small flats on them to tighten them up, sometimes the whole flange but more often just a turned down shallow shoulder.  Here's an example of the former, reworked rods for my Ixion Hudswell Clarke 0-6-0ST:

 

 

and of the latter on my reworked motion of a FineScaleBrass Jubilee:

 

 

David

[Simond]

I have to say, they do look rather nice...

[Fastdax]

I have to say, they do look rather nice...

 

Seconded - tasty metalwork there.

[Fastdax]

Valve gear

 

Here are the parts for the left-hand valve gear.

 

 

And removed from the fret and laid out in approximate position.

 

 

Perhaps some terminology would be appropriate at this point. Here's a diagram of Walschaerts Valve Gear from my Grandad's "Handbook For Steam Locomotive Enginemen".

 

 

This is the 3-layer Union Link, which took a bit of head-scratching to put together. The instructions merely say "assemble" and the drawing of it isn't much use. I figured out that the end with the fork connects to the Combination Lever and the end with the single hole attaches to the bottom of the Crosshead.

 

 

Most of the bits are 2- or 3-layer nickel-silver laminations, which I won't bore you with the assembly details of.

 

The first bit I added was the Radius Rod, as this is captive to the chassis at both ends and never moves. This represents the loco in "mid-gear" which is a compromise between forwards and reverse, one of which would be wrong when travelling the other way. The instructions tell you to use a wire pin at the valve spindle end, but I chose to use a 12BA bolt, self-tapped into the whitemetal guide block. This will allow me to remove the valve gear in two parts and not have the two bolt-on WM blocks held loosely together with the Radius Rod.

 

 

This is the 2-layer Return Crank, being tapped 10BA.

 

 

Once this was done, I added a 10BA brass nut to the back of the crank, as per the instructions. This allows the crank to be tightened onto the rear crankpin. If it (inevitably) comes to rest in the wrong position, a light file of the back of the nut, a bit at a time, allows it to be adjusted until it tightens up in the right place.

 

 

Here's the Return Crank, bolted (12BA) with washer and nut to the Return Crank Rod, which is jointed to the two halves of the Expansion Link using one of the valve gear rivets supplied.

 

 

The moving bits behind the Radius Rod could now be bolted and pinned in place, and tested;

 

 

Here's the Combination Lever and Union Link. Both ends of the Union Link are jointed with soldered rivets. To stop the joint being soldered up solid, I blacken the moving bit of the joint with permanent marker pen and get in and out very quickly with the iron on the tail of the rivet.

 

 

The top of the Combination Lever is held by the same 12BA bolt that holds the Radius Rod. I filed flats top and bottom of this bolt head, to make it resemble the real thing a bit more.

 

Then the full motion could be tested on the rolling road.

 

 

It was a bit sticky at first, but with a bit of sanding of the Slide Bar and lubrication on all joints, it freed up a lot.

 

There are still several jobs remaining on the valve gear, but this feels like a good start.

 

Edited December 30, 2023 by Fastdax
Reinstating photos.

[Guest Isambarduk]

You're getting there, well done!

 

" I figured out that the end with the fork connects to the Combination Lever and the end with the single hole attaches to the bottom of the Crosshead."

 

Well, yes, that's probably what the kit designer intended but, in reality, both ends of the union link would have been forked - either that, or there would have been a fork on the end of the combination lever (or the crosshead) to avoid the undesirable twisting moment of a plain pin joint.  There may have been examples where there was a stiff pin in the crosshead (ie no fork) but I am no expert so perhaps this was quite common?

 

David

 

PS They are still 12BA screws, not bolts, especially if they are self-tapping :-)

[Fastdax]

PS They are still 12BA screws, not bolts, especially if they are self-tapping :-)

 

Yes, I know they are really screws, not bolts. I thought the use of the word "bolt" was perhaps clearer for those who are not so familiar with the gritty details of engineering.

 

To many, a "screw" is a pointy thing that you drive into wood. I've had this misunderstanding before.

 

The screw I drove into the whitemetal wasn't a traditional self-tapper (it had no cutting flutes) but was a normal 12BA steel screw. It self-tapped because whitemetal has the consistency of elderly cheddar. I did work it through slowly though, backing it off every so often.

[Simond]

Not so much thread cutting as thread forming.

 

Used the trilobe thread forming screws (? ) lots in a previous life in the auto industry - they have the multiple benefits of no swarf, a stronger thread (particularly useful when you are using extruded collars in sheet metal, and you have no thickness to play with) and they have a very useful tendency to self-lock, in so much as the elastic deformation tends to prevent them shaking loose or reversing.

 

They were typically M6, not sure anyone makes them in 10BA sizes!

 

Best

Simon

[Fastdax]

Used the trilobe thread forming screws (? ) lots in a previous life in the auto industry - they have the multiple benefits of no swarf, a stronger thread (particularly useful when you are using extruded collars in sheet metal, and you have no thickness to play with) and they have a very useful tendency to self-lock, in so much as the elastic deformation tends to prevent them shaking loose or reversing.

 

I had to look up "trilobe thread forming screws" :-)

 

I assume this is what you're talking about ... ?

 

 

 

They look very useful although if I found one lying around, I'd probably think it was a setscrew and throw it away as a malformed 'un!

 

Duncan

[Simond]

Exactamundo!!!

[Fastdax]

More valve gear

 

In the ABS kit there's no provision for the valve spindle crosshead. The instructions ask you to add cosmetic bits of wire for the valve spindle gear, but nothing more detailed than that. The top of the Combination Lever is left just waggling around in free space.

 

So I made up a valve spindle from 0.9mm nickel-silver rod and fashioned a bracket from strip brass shim to hold it in the slot in the valve guide casting. I reversed the 12BA screw holding the Combination Lever so that it is screwed in from the back and a touch of solder (for now) holds the tip of the screw to the Combination Lever. This allows sufficient clearance to the new valve crosshead to allow it to slide back and forth.

 

It resembles the prototype valve gear, which has a noticeable strap across the top of the Combination Lever.

 

There's not much movement of the valve spindle - about 1mm - but at least it does now move.

 

 

Of course, I have got to do all this to t'other side now :-)

Edited July 11, 2016 by Fastdax

[Fastdax]

One thing I want to source is the correct 22" buffer heads. These were additional dished discs of steel added to the normal-size buffer heads to help avoid buffer-locking on tight industrial docks.

 

The buffer heads in the kit are 9.5mm dia (16" or so) so I need either 22" (13mm) plant-on buffer faces or replacement 22" buffers.

 

A quick search has turned up no results, so does anyone know where I can get such items?

 

Thanks,

Duncan