Kit Build - LRM LMS 2P 0-4-4T (P4)

[Jub45565]

So to the chassis.  Firstly, the etch (minus the rear bogie bits already played with):

 

 

The spring hangers could be more detailed, or better still supplied as per the current generation of Comet kits so as to allow them to be readily removable.  Also, while the kit is sold as being designed with twin beam compensation in mind, there isnt a half etch marker for where the beam should sit.  I'm glad I'm fully aware what the different forms of compensation are, as going blind into this would be impossible via the instructions!

 

The current state of play is thus, clamped together with the Comet frame jigs having had the hornguides opened up.  Nothing has yet been soldered...

 

 

As I've said, my plan was to construct the chassis with twin beam compensation 'as per the instructions' but as this isn't actually fully allowed for I am having second thoughts.  I was going to use Comet(/Brassmasters) hornblocks anyway, so while I now have to locate the pivot point for the beam, I could just cut slots to allow for the Comet blocks to be used with their springs as intended.

 

The concern I have with springing the drivers is that I think I would need to be more precise with the overall centre of gravity, to ensure both driven axles are compressed equally whilst also keeping a bit of weight over the bogie to make it road hold.

 

Any thoughts appreciated :-)

[garethashenden]

The centre point should be pretty easy to locate. Take one beam and one frame and put them together with 1/8" bearings, so that the bearing goes through both the hole in the beam and the hole in the frame. Then use the hole in the beam as a guide to drill the hole. It may be better to do both frames together so that they are consistent. It doesn't need to be perfectly centred, but they do need to be the same.

 

You need to decide between twin beams and hornblocks. It's one or the other generally. The hornblocks move vertically while the beams rotate. If you have both it won't move at all and you may as well build it rigid.

 

EDIT: It seems you've already removed the bearing holes from the frames, my suggested method will no longer work.

Edited May 10, 2015 by garethashenden

[Jub45565]

Cheers Gareth - you make an interesting point... I was thinking the twin beams would be beams resting on the axles and with hornblocks in hornguides doing the axle holding, but working from your comment you are correct that the twin beam setup does have two full beams supplied for use with 1/8" top hat bearings.

 

Reading the instructions again properly the pivot point is marked, though it confused me as there are 2 points etched and so I assumed them to be rivets...  The compensation build isn't covered ongoing in the chassis build section but is covered in the preamble to the kit as it notes the different options available. It doesn't fully mention how to make them work, but I am assuming top hat bearings in the beams and mount these on a pivot rod with a suitable length of tube to keep the beams next to the frames.  It would be possible to just use pins to hold them to the frames, but my brass pins are 0.55mm so are a bit too flimsy for the task in hand I think.

 

Humble pie to be eaten by me then!

[Jub45565]

That is actually pushing me towards springing though, as with the beams holding the axles in (rather than just resting on the top) it prevents the wheels from being dropped out of the chassis.

[N15class]

If the beams are detachable you can undo them abs drop the m and the wheels out as a unit.

[Jub45565]

I agree in principle, and that would do the trick as the wheelsets would be tied together by the coupling rods anyway.  I can't readily think of a way of making the pivot beam removable though, without having that connected via screws or something which would be visible from outside the frames?

 

I hope I'm not coming across as negative - it probably is in text! - but it is actually an interesting challenge to come up with a functional yet clean/paint/repairable solution!

 

Plenty of time to sort it all out in my mind before the wheelsets arrive :-) 

[N15class]

I use a screw each side with a nut to hold the beams on.

[Horsetan]

There's not enough allowance in the chassis topline to use coil springs, Brassmasters/Comet style, but if you're going to be using the CSB system, it doesn't matter too much.

[Jub45565]

Good point. I've just looked at the high level csb bits I have. I only have the 2mm ones, but looking at the 1/8'' blocks I would guess that the csb adapter wouldn't be compatible with the BMW blocks.

 

I could use the HL blocks themselves - but it is far too easy to misalign something as it is without adding more variables!

[billbedford]

See this page and scroll down to Allan Ferguson's 4-4-0 to see how to use Brassmasters bearings with CSB

[Jub45565]

Thanks Bill - that is a neat solution.

 

I am definitely sold on the CSB principle, but have only implemented it on tenders so far (1 of which is a complete loco - albeit a Hornby based 4F, with a Dave Franks chassis under a Comet tender), a second Dave Franks tender, and 2 Brassmasters Easi-chas tenders.  I might yet get the 3F pickups sorted tonight, but I digress...

 

I would be best off cutting my teeth on a fairly well balanced loco (my plan is an Ivatt tank), while the 0-4-4 is always going to end up back heavy - especially with the resin boiler - and worrying about how the trailing bogie works with the springing would, I think, be a nightmare for a first attempt at sorting out CSB anchor points.

[billbedford]

Ah, but the world would be a better place if people just worried less and built more.........

 

As for 'balancing' a 0-4-4T forget about it. It's a myth. It may have had some currency in the days when four coupled locos were built with all the weight over the drivers and the bogie just waddled on by itself. Most people today would say that if you want a well performing loco the bogie has to carry its share of the weight. What you have been planning seems to be more or less ideal to me, a bogie with working compensation beams, though it would be better if neither beam was fixed, and CSBs on the drivers. 

 

I looked up the diagram for the 2P tank and it show the axle weights to be 16 T - 8 cwt, 17 T 8 cwt, and 24 T -11 cwt on the bogie. I suspect that even with a resin boiler you can make you model better 'balanced' than the prototype without a lot of effort.

 

BTW is the boiler completely solid?

Edited May 12, 2015 by billbedford

[Jub45565]

There was me thinking that procrastination was an art form 

 

I quite agree that the bogie should take its fair share of the weight - but I'm not quite sure how to go about working out CSB hanger points.  I could take the bogie pivot point as effectively a third axle, but that would mean the maths would be worked out on having the bogie pivot hanging off the CSB itself, which I wouldnt want to do.

 

With the body built as far as it is, it would be possible to add weight to it and work out where the actual centre of mass is going to be, but as I say the question is how to remove the effects of the bogie from the CSB calculations.

 

It is interesting to see your comment on the bogie sideframes Bill - I too thought that having both free would make more sense, and surely the downforce from the spring would keep the main frame level.

 

The boiler as supplied is solid (only full diameter to just behind the tank fronts, and is semicircular backwards from there) but I have already drilled a bit of an opening, and intend to carefully continue with this to allow some weight to be packed in.

[billbedford]

I generally ignore a bogie when designing CSBs. For a four coupled loco this makes the setting out of the anchors really easy: The centre one should be halfway between the driving axles and the outer ones are a equal distance outside their respective axles. Optimally the outer anchors should be about 30% of the wheelbase outside the axles but often that coincides with a brake hanger and they have to be moved. Setting the vertical height is more tricky especially as you have soldered up the frames. The height of the anchors above the finished axle centres, should be about 0.5 mm below the distance between the centre of the bearings and the centre of the anchor. However it is more important to get the anchor points matching on each frame than to have them in a horizontal line. If the anchors are higher on one side that the other the loco will tend to list, while if they are not in line it just makes the calculations more difficult. This is the reason that it is preferable to make the holes for the anchors with the frames stuck or soldered together, presuming you are using handrail knobs for the anchors. 

 

Rather than trying to calculate the centre of mass etc. it is a whole lot easier to move ballast weights and use spring wire of different diameters to get the loco the sit well.

 

You can spring the bogie if you wish. There are ideas of how to do it in the instructions here and here. 

[Jub45565]

Thanks Bill.  I haven't yet soldered up the frames - they've just been clamped in the frame jig but taken no further as yet, so the only thing that isnt there is the vertical axle centreline - but I have the cutouts still so can easily see where that was.

 

Thanks for the dimensions. I'll have a look and see where that puts them.

[Jub45565]

Well 1 hornblock has been modified for CSB, and so far so good!

 

First I filed off the lip, as there isnt enough 'meat' between the edge of the lip and the top edge of the hornblock to drill out for the handrail knob.

 

Brassmasters/Comet hornblocks are handed, in that the slot for the frames is offset so as to allow different amounts of sideplay on the axle.  As this is a 4 coupled loco, I don't feel the need for much sideplay, so am putting the 'fat' side of the hornblock on the outside of the frames, and so have drilled for and fitted the handrail knob from the 'thin' side.

 

I used (part of) a lacemaking pin to hold the handrail knob in the correct orientation while I soldered it in place.

 

 

[N15class]

Well 1 hornblock has been modified for CSB, and so far so good!

 

First I filed off the lip, as there isnt enough 'meat' between the edge of the lip and the top edge of the hornblock to drill out for the handrail knob.

 

Brassmasters/Comet hornblocks are handed, in that the slot for the frames is offset so as to allow different amounts of sideplay on the axle.  As this is a 4 coupled loco, I don't feel the need for much sideplay, so am putting the 'fat' side of the hornblock on the outside of the frames, and so have drilled for and fitted the handrail knob from the 'thin' side.

 

I used (part of) a lacemaking pin to hold the handrail knob in the correct orientation while I soldered it in place.

 

20150513_212234(1).jpg

 

20150514_181054(2).jpg

I think I would file the flange on the knob down on one side less filing and probably a lot quicker.

[Jub45565]

Sorry I've been quiet - I've been floating around Warwickshire for a week. 

 

You may have a point Peter, but the Brassmasters block was pretty easy to file down. It also wasn't just the size of the knob but also the meat available on the hornblock outside the flange but below the edge available to drill.

 

That all sounds a bit innuendo bingoey when re-reading, but nevermind...

[Jub45565]

I have now assembled all 4 hornblocks and done some measuring.

 

These locos had an 8' wheelbase, and the etch measures correctly at 32mm. There are the 2 half etch points for the twin beam arrangement, 1 of which is at axle centre height so can be used as a datum.  My Brassmasters hornblocks with handrail knobs fitted is 2mm from axle centre to handrail knob centre.

 

From the maths Bill gave earlier (30% of wheelbase outside the axle), the outer anchor points therefore go at 25.6mm from the centreline, and with 2mm axle to handrail knob the anchors (all 3) should be 1.5mm above the axle centreline.

 

I think all this is correct, so will mark out the points, but not drill anything tonight in case someone spots an error in the above!

[Jub45565]

Sorry for the slight delay - partially due to the nice weather, and partially due to starting a new topic (http://www.rmweb.co.uk/community/index.php?/topic/99883-ilkley-locomotive-shed-4mm-p4-1950s/) but I am keen to keep the momentum up with this build before another distraction appears!  It has been a really enjoyable build so far though.

 

I took the loco up to the Glevum P4 group last Tuesday, and Morgan kindly showed me how to sort out the cab sides above the doors, with the use of a handy wagon axle.  This left the soldered corners with a bit of a droop, so I have continued with one of these, and am happy that I have improved it, so will have a go at the other...

 

The tackled side:

 

The second side to tackle - still a bit droopy:

 

 

Another thing Morgan spotted was that the splashers both had a lean on the go.  I hadnt spotted this as (my excuse, anyway:) it wasnt as noticeable before the tanks were fitted, and I hadnt closely examined them since.  Morgan did share a good method to do these though, by soldering a cross member between the two to get the sides square, and this can be left in while (re)fitting the tops and then removed at the end - keeping it all square.  I've done the first bit...

 

[45609]

Hello Pete,

 

The left hand side cab awning is looking much better now.  Well done.  As I said to you last week its rare that something is completely irretrievable and it really depends on how much work you are willing and prepared to put in.  This loco body (considered a basket case by some) was completely rebuilt after attacking it with a cook's blow torch to get it back to component parts and cleaning up.  I've done this quite a few times with poorly built brass kits.

 

https://www.rmweb.co.uk/community/index.php?/blogs/entry/9490-coronation-tank/

 

Of course having a few sneaky tricks up your sleeve to get the metal to do what you want helps but on that subject there is always help and advice available.

 

Cheers.....Morgan

Edited November 17, 2017 by 45609

[Jub45565]

So with the splasher sides held vertical, the next step was to add the tops:

 

 

And then remove the cross piece, cutting it in two and then desoldering from each end:

 

 

Next up was preparing the bogie for split pickups.  I created a sub stretcher from 60 thou plasticard, and stuck that in place with epoxy.  Once fully cured, the metal frame was cut through, off centre so as not to interfere with the attachment point.  I ensured that two metal structures were fully isolated, checking with a multimeter, before filling the cut slot with more epoxy.  This now needs sanding down, and the bogie pivot hole redrilling.

 

 

 

The last bit of progress, for now, has been the adding of brake gear hanging rods.  Another gem pickup up from Morgan, these are made of 1.2mm OD 0.6mm ID tubing, and the brake gear itself will be constructed on 0.55mm lacing pins cut short, so that the brake gear will be able to be clipped on and off - making the painting job easier, but also allowing the wheelsets to be released.

 

[Jub45565]

Time for an update!  Not a lot has been done of late, mainly as I was waiting for the Ultrascales and then Ilkley has taken over a bit (http://www.rmweb.co.uk/community/index.php?/topic/99883-ilkley-locomotive-shed-4mm-p4-1950s/page-2&do=findComment&comment=1958849).

 

However, the trailing bogie is now complete, with its split axle pickups.  These use Branchlines axle parts (and jig) and standard phosphor bronze pickup wire which as can be seen was aligned over the axle hole when fitted to keep it in tension.  The photo was taken as soon as I'd done the soldering, these where then cleaned up and sanded flush.

 

 

 

Next on the agenda is constructing the gearbox and playing with the CSBs. I'm going to try 12 thou first I think...

[martin_m]

Very interested in the bogie arrangement.

 

Could you use rubbing pads/plungers to pass the power to the main collectors?

 

Do you know if the Branchlines axle parts (and jig) for 2mm axles are still available?

 

martin

[Jub45565]

Hi Martin,

 

As per Bachmann DMUs and LMS bogies?  I don't see why not.One reason for doing it this way is that I can do powered tests with coupling rods before sorting out the driving wheel pickups, but using plungers might actually help with road holding as well as being a means of pickup.

 

I very much hope the Branchlines bits are still available - but aside from a phonecall I couldnt confirm, someone else may be in a position to know though.  I believe they were at Larkhill recently, and will be at Railwells, so I'm sure someone will be aware.

 

Cheers,