7mm The Derby Line - Rolling Stock

[dibateg]

I'm tackling the valve gear, here is 92204, and finding irritating things. The weighshaft is a sleeve into which the right hand and left hand stub shafts fit ( my design ), but with the weighshaft in place the screws to secure the motion bracket cannot be reached, so I drilled and tapped for 2 12 BA screws in each. Then the radius rods seemed slightly short, and the valve spindles were hanging out of the backs of the guides. So I cheated and drilled a pivot point further back, with a false 'pin' on the visible side. Various people have told me there is a problem with the eccentric rod - that will be next....

 

[dibateg]

I think I finally worked out why folks have had problems with the left hand eccentric rod on this 9F kit. The pivot point on the motion bracket casting is in a different position to that on the drivers side. Both castings seem to have errors. The drivers side should not be so recessed below the weighshaft - this makes the lightening hole far to small. The fireman's side doesn't look deep enough in the area of the lightening holes. I considered Ragstone ones - but it would mean more back tracking and retro fitting. I've done a cut and shut job on the right hand eccentric rods to shorten them a couple of millimetres.

 

[dibateg]

And I should have said right hand eccentric - that's what toothache and headache do for you. Despite that I have pressed on today, snow outside and storm approaching...
I can't get on with some of these one piece fold ups, I couldn't get a clean fold, or the front panel in the right place at the top of the side piece. So I broke them off and cleaned up. It was a lot easier to gettem in the right place then. I also cut out the holes for the filler access on the mechanical lubricators, it just looked blanked off as a half etch.

 

[alcazar]

I thought I'd read somewhere that you cut those out once it's fitted, to retain rigidity?

Will you reinforce those joins above?

 

[dibateg]

No - there was a representation of the lubricator top in the half etch. There is a massive casting that goes under the whole running plate, I'm considering whether to modify that and just use parts of it.

Also - no need to reinforce, they'll be strong enough.
Tony

 

[dibateg]

The running plate is supported by a hefty casting, I didn't want to use all of this as in places it made the running plate look to solid, so I cut off each end and used bullhead rail as re-enforcement. It also makes it easier to pass pipes etc through.
The boilers were interesting, the one for 92031 bought who knows how many years ago needed hardly any cleaning up, that for 92069, about 5 years old and 92204's fairly new, needed flash cutting off with a hacksaw... Moral - buy a kit when it is introduced, when the moulds are in good condition.






And at last we have a line up, propped up with bits of wood and plastic, but you get the idea...

 

[dibateg]

92204 takes shape, although not seeming very different from the previous photos, the boilers have been drilled and as many item fitted as possible before attaching to the running plate. As usual BR Standard cabs are tricky and all three locos needed careful fettling of the firebox end of the boiler to ensure the cab fits tidily and is level. There is still some work to do before permanently attaching the cab. Most of the items cannot be soldered from the inside of the boiler as the spigots are too short - or the boiler is too thick! So I've had to resort to epoxy. I feel I'm getting somewhere now, although there is a long way to go yet.
The roller bearing covers have arrived from Ragstone, so I can put on the eccentric rods when I return to the chassis.

 

[dibateg]

I've had 5 days in bed with flu since the Bristol show, but I had spent time mulling over the DJH motion brackets. I wasn't fully happy with the castings as they didn't quite represent the prototype fully in that the main bearings were too inboard and the distinctive triangular hole on the drivers side was far too small. The Ragstone ones are crisper castings, although the bearing bosses seem slightly large. So 92031 was selected for conversion. It was a fiddle to make them removable, and the screw mechanism seems a bit low, but the overall effect is far better than before.
Here's a comparison of the castings.


A test fit and I think the whole thing needs to go about a mm higher, but I'm on other stuff for a day or whilst I think about it..and I don't like those frame humps for the weighshaft, the real thing doesn't have them....they might go too. Lots of tidying up to do yet

 

[mickoo]

Comparing the two castings, it's a no brainer really and yes, those weighshaft frame lugs have to go, but only the top half and they need reshaping to represent what I think might be emergency support lugs, I presume they are there in case a bearing fails and the shaft doesn't jam up.

This is a view from the firemans side across to the drivers side bracket and looking rearward.


The motion bracket does need to move up, or the footplate down, problem is if you move it up it's base will protrude above the frame line.


If you move the drivers side up so the arm attached to the screw shaft is in the correct relation to the footplate then the fireman's side will have to go up as well or your shaft will have a tilt in it, that would bother me, and I'd guess given the lengths you've already gone for accuracy, it'd bother you too

Moving it up may also put the shaft too high above the frames, looking at the slide bar bracket and the base for the lubricator, could the footplate be a little high? Either way, super work so far, I must resit mine under the desk a little longer

Addendum, I've been thinking about these castings, how do they compare in height to the DJH one? I wonder if both are biased toward the Britannia motion bracket which is slightly shorter.

The red line is the weighshaft axis, the green line is the bend line in the casting, on the Britannia the lines are almost in unison, on the 9F the weighshaft axis is much higher.

9F annotated motion bracket


Britannia annotated bracket


Model motion bracket.


Note also much larger bearing boss on the Britannia casting which matches earlier observations.

I've no idea what the Seven models 9F and Britannia look like or if they are the same in each kit, I suspect they are I suppose I could open the boxes but that might lead me astray

There's one thing I've noticed when researching the Britannia and 9F, Standards in name, but rarely in practice

 

[dibateg]

Thanks very much for your excellent assistance Mick, and yes the thought process has been the same. It does look like the weighshaft is too low, so I shall tweak it upwards and post results.
When you compare the two castings, the dimensions seem very similar. The DJH reverser screw is set too far inboard, so even though its only fractionally higher than the Ragstone one, it is further back from the edge of the running plate and not so obvious.
Cheers
Tony

 

[mickoo]

Tony, moving up will help things, certainly toward the footplate visuals.

I checked the Seven Models 9F, it's a fabricated motion bracket and from a basic look at the instructions looks wrong above the bend line on the rear face, I.E no bend line.
It's easily fixable, but the initial survey is from the hand drawn assembly notes, not the actual etches, I like to leave them wrapped up until I begin the model

Now that Winston Churchill is back at NRM I need to visit to shoot some details, as well as the hundreds of details I missed on the 9F and a whole load I need from Mallard and her tender, oh and some drawings

 

[dibateg]

In the end it's all compromise, maybe the running plate is a shade high, but I couldn't get both Ragstone castings to fit and look right. The bracket on the fireman's side should sit well down between the wheels. So I ended up leaving the weighshaft at the original height setting and using the DJH casting on that side. The Ragstone one looked better but sat too high, and I didn't want to start carving up castings in decreasing circles of despair.. The drivers side captures the beefiness of the bracket and also reaches up closer to the running plate. Although for me the boss for the expansion link bearing seems slightly too large, but I'll live with that. Those frame 'humps' will have to go eventually.
The cab roofs are now on - they were a battle as they were a very tight fit. More to follow..

 

[dibateg]

I thought that Simon ( Hobbyhorse ) came up with a great way to make the deflectors removable. I used some angle section and drilled and tapped it. Each deflector consists of 23 parts, so it was a days work to make them all up and fit them.

 

[Nick Dunhill]

It's a cracking build Tony. Are they all commissions? It seems the world is about to be flooded with RTR 9Fs.

 

[oldravendale]

I thought that Simon ( Hobbyhorse ) came up with a great way to make the deflectors removable. I used some angle section and drilled and tapped it. Each deflector consists of 23 parts, so it was a days work to make them all up and fit them.

View attachment 40940

I could do with plagiarising that method of fitting the smoke deflectors. Can someone point me in the direction of then original post?

Brian

 

[OzzyO]

Hello Brian, try this link http://www.rmweb.co.uk/community/index.php?/topic/88206-updating-30862-and-2-more-7mm-nelsons/page-8

OzzyO.

 

[mickoo]

Hello Brian, try this link http://www.rmweb.co.uk/community/index.php?/topic/88206-updating-30862-and-2-more-7mm-nelsons/page-8

OzzyO.

Its craftsmanship like that and threads like this which drive home how bloody inept I am LOL, nice tip on the low melt solder though, I've always struggled fixing white metal to brass and often end up using an adhesive.

 

[richard carr]

Mick

Stick with the glue its miles easier than faffing with solder on white metal and brass.

Richard

 

[dibateg]

Thanks guys -

Yes I've got my eye on the RTR 9Fs and very nice they are too. Two of the 9Fs are for me, the other is a commission. If I had the money, I'd probably go for the Lee Marsh model, but the kits have been in my cupboard for a few years and to raise the money for MOK/Marsh is just not an option. So we do the best with what we have got....
I use 70 or 100 degree solder to join brass to whitemetal/pewter depending on the nature of the join. I tinned the chimneys first with 145, before using 70 degree.
Regards
Tony

 

[mickoo]

Mick

Stick with the glue its miles easier than faffing with solder on white metal and brass.

Richard

Yeah, kinda arriving at the same conclusion myself. This 604 is pretty good stuff, I stuck two strips of 10 thou together to strength test, tried pulling apart, one end in vice the other in grips, it pulled the bench top up (MDF 25mm 4x2' with all my stuff on), then tried to twist them and it just failed to part and ended up nearly tearing the metal.

Mind, I just know when I use it on the Cartazzi axleboxes and driver spring hangers one of them will drop off LOL.

Thanks guys -

Yes I've got my eye on the RTR 9Fs and very nice they are too. Two of the 9Fs are for me, the other is a commission. If I had the money, I'd probably go for the Lee Marsh model, but the kits have been in my cupboard for a few years and to raise the money for MOK/Marsh is just not an option. So we do the best with what we have got....
I use 70 or 100 degree solder to join brass to whitemetal/pewter depending on the nature of the join. I tinned the chimneys first with 145, before using 70 degree.
Regards
Tony

I've been trying to use 145° only, never thought to use 70°