The Bodgerigar attempts to build a Collett 1938 31xx

[The Johnster]

I have ordered some parts from Hornby that are to be used for this project, so I suppose I can claim that it is officially in progress as of now, awaiting delivery of parts.  The project is to build an acceptable layout model of 3100, doyen of this Collett large prairie class of 5 locos.  Introducing..., 'Johnster's big big prairie build/bash/bodge etc'!  It is a proper project, because I've labelled a cardboard box for it so there's no going back now!  Been talking the talk for years, time to walk the walk, Johnster me laddo...

 

The development of the various large prairies is complex and at times seems deliberately confusing; to briefly summarise, the original design was the Churchward 31xx which was developed by Collett into the 5101 class and all Churchward 31xx locos were eventually absorbed into this class; no.2 boilers and 5'8" driving wheels, all conforming to Churchward standard practice.  The other Churchward large prairie was the 3150, a similar design but with the larger no.4 boiler as opposed to the 31xx no.2, making the locos heavier and more powerful.  Collett clearly thought there was more to be had from the concept and developed the 5101s into the 61xx class, which had higher boiler pressure to enable faster getaways from stops on the intense Paddington suburban trains, and then developed that successful class into the 10-strong 81xx, with smaller 5'6" driving wheels for the hills of the Midlands.

 

He then turned his attention to the 3150 'larger' prairies, and rebuilt 3173 into 3100 with a higher pressure no,4 boiler and 5'3" driving wheels in 1938.  The original 3150s had been used largely on heavy transfer freight and banking work, and the 31xx were seen as a development of this.  Collett intended to rebuild the entire 3150 class to this new 31xx specification, but the impact of German foreign policy decisions between 1939 and 1945 prevented this and the bulk of the 3150s survived into the late 50s or early 60s in their original form, albeit with modernised bunkers, curved front running plate drops and such.  Hawksworth built more 5101s, which Swindon turned out until the early 50s when they were replaced by the BR standard class 3MT tanks.

 

3100 was sent to Tondu, which is where all the locos at Cwmdimbath are allox, in 1946 to resume the daily Porthcawl-Cardiff 'residentail' commuter service, which had been suspended during the war.  Before the war, it had been hauled by a series of Bulldog 4-4-0s allox TDU for the purpose.  It's large boiler, smaller driving wheels and higher boiler pressure made it well liked for it's ability to get away from the main line stops with this train without delaying faster traffic, and it was associated with the 'residential' until 1957, when it apparenlty impacted the buffer stop at Porthcawl fairly hard, resulting in damag to the frames according to the John Hodge and Stuart Davis book on the Tondu Valleys.  It spent some time as Ogmore Junction Yard Pilot, before being withdrawn from service and sent to Swindon, where the decision was taken to scrap it, though it was not actually dismantled until 1961.  Photos of it at Swindon during this time do not show any obvious damage, and the running plate is level and unbent, and Hodge/Davies suggest that a loco less than 20 years old should not have been done away with and that it is possible that some confusion led to a mistaken belief that the loco was a 3150, but of course in many ways it was, and the 31xx class was in any case extinct only 4 years later.  Here it is at Swindon after withdrawal, looking to be in full working condition.

 

 

 

So, what has this got to do with Cwmdimbath, up in the mountain fastnesses among the sheeps far, far away from the seaside or the SWML, Johnster, I hear you ask, your little faces all eager for enlightenment.  The answer is to be found on page 323 of the Hodge/Davies book, a photo of the loco in the platform at Abergwynfi with a Bridgend train, in unlined black livery with BRITISH RAILWAYS in Gill Sans lettering on the tank sides and a train still in GW livery.  The photo is credited to I.L Wright and dated 28/8/61, clearly a misprint for 1951, but it proves that 3100 did spend time away from it's usual job on the Porthcawl residential.  That's good enough for me, if it got to Abergwynfi it might have plausibly got to Cwmdimbath occasionally!  I don't need much arm-twisting as I like these thuggish looking beasts, the small wheels and big boiler making them look bigger than a 3150, and the high domed cab roof enhancing the impression of bulk, a 3150 on steroids and the ultimate large prairie development.

 

The plan is to use a the chassis block, motor, pickups, and motion from an old Airfix 61xx, and to hack the boiler and cab out of it's body moulding.  We will then need new wheels, a cylinder block to replace the broken Airfix one, and a front pony to replace the missing Airfix, the latter items being on order from Hornby.  The cylinder block is actually for a Grange and the pony for a 42xx, and we also need a new motion bracket.  We need to cut the running plate to be at a lower level and raise the mounting of the body to account for the smaller driving wheels to get the buffers to sit at the right height, and new cab sides to incorporate the distinctive gap between the top of the cab cut-out and the high domed roof, which seems to be similar to that of a 42xx.  The tanks are a completely different profile to a 42xx, though, and it is not a matter of grafting a 42xx body to the Airfix underpinnings.  Trimming 42xx tanks from the bottom would lose vital rivet detail, and the protrusion of the boiler at the tank tops is different.

 

We then need a no.4 boiler, and this might be sourced from a Kitmaster CoT kit or a Mainline 43xx body tooling, and a new cab roof and front and rear spectacle plate fabricated or possibly bodged from a Hornby 42xx body.  Plan is vague and subject to arbitrary alteration for no apparent reason, but will go something like:-

 

. Remove motion from Airfix chassis for re-use later with new 5'3" diameter driving wheels.

 

. Remove Airfix wheels and dispose.  Easy enough so far...

 

. Fit replacement driving wheels, and fettle and test run chassis with original motor and pickups.

 

. Fit Grange cylinder block and test run with Airfix motion re-fitted.  I am expecting trouble here.

 

. Cut the boiler and cab sides out of the Airfix 61xx body.

 

, Cut the running plate valance horizontally beneath the running plate at the front drop, and through the cab steps to the rear drop, and fettle until the body sits level at the right height.  The cylinders will now be sitting lower because of the smaller driving wheels, so some packing will be needed to get the buffer beams to the right height, which will leave an incorrect gap between the bottom of the running plate and the top of the cylinder block, but I can't see a way around this at the moment and will have to live with it.  Comments will be referred to my Hornby 2721...

 

. Test fit to chassis to establish clearances, level, etc., then remove for futher work.

 

. Fit new no.4 boiler.  Should be ok once there is sufficient clearance for it between the tanks, but it will need a lot of surgery, I mean brutality, to its lower portions

 

. Fabricate and fit front and rear cab spectacle plates, and fit cab detail if possible (rear of Airfix chassis block may need to be cut out for this.

 

. Fabricate new cab roof, possible 42xx part.

 

. Probably needs 42xx chimney.

 

. Fit body to chassis, test run, paint (1951 livery), details, number plates, into service.

 

This is never going to be a fine scale model, and will be a 'representative' layout model.  I will be happy if it runs reasonably well and looks sufficiently different to a 3150 to be identifiable as a Collett 1938 31xx.  Cost so far is £10.04 for bits from Hornby, but that will rise as more components are needed.  I'll be happy if I can bring her in under £50.

 

Watch this channel for the next thrilling installment, 'innocent 61xx savagely murdured'.  I'll try to take photos which will illustrate the project as it progresses.

Edited September 3, 2021 by The Johnster

[The Johnster]

Well, I opened hostilities last evening, and some progress has been made in taking the 61xx to bits, but I ran into an unexpected problem as well.  Expecting to be able to remove the Airfix crankpins with a nut spinner, I discovered that they have round head, and are therefore so far as I can tell impossible to take out. This means that, if the motion cannot be separated from the wheels, a new set of motion must be sourced.  Then I hit another problem; the wheels are not coming off the axles.  This is serious, as we are now into having to obtain new axles and gears as well, so probably a new motor.  This is a lot more faff and expense than I signed up for!

 

The progress, such as it is, is in removing the boiler and cab from the running plate and tanks/bunker.  I've got the smokebox end off, and have made a cut horizontally to remove the front dropped part of the running plate, the width of the cut being (I hope) sufficient to allow the running plate to sit a scale 2.5 inches lower because of 3100's smaller driving wheels.  This is the state of play at the moment; I have started the cut along the tank tops and made the cuts at the cab steps to lower that end. 

 

 

 

The running plate forward of the tanks is very flimsy and has cracked at the front on the left hand side.  This will be easy enough to repair, but I'll be happier when the new boiler is in to give it some structural integrity.

 

But the chassis problems have cast a doubt cloud over the whole project.  I'd hoped I was going to be able to get away with just replacing the wheels, but I'd hoped in vain!  In the meantime I'll plug on with the body, while giving thought to alternatives.   In terms of RTR running chassis tha might fit the bill, BR standard 3MTs have the same axle spacing as the GW large prairies, and the correct diameter driving wheels.  The Hornby K3 also has the correct size driving wheels, but I am not sure of the axle spacing on this loco.  Using either of these has the advantage of providing a running chassis with the correct size wheels for 3100, and the motion should fit the 3MT.  But it's expensive, prohibitively so, and I will still have to source motion (Hornby?, Dapol?, Mainline?, Southeastern?)  Both the RTR chassis mentioned (I would be grateful to hear of any more with the correctly spaced 21mm drivers and suitable wheels, I can live with an extra or missing spoke or so) would need a good bit of savagery to the chassis block, but I am having to consider alternatives now!

 

Of course, there may come a point when it is simply not worth the effort, which will only produce an impressionist 'layout' model anyway.  But I haven't thrown in the towel yet!

 

[lofty1966]

Don't the crankpins just pull out on the older 61xx models?

 

[Nick Gough]

The crankpins on the centre drivers definitely should unscrew - I had to replace damaged con rods on a couple of mine.

 

As you say the heads are rounded, so I had to use pliers.

 

I haven't tried but I would expect the pins on the other wheels to also unscrew.

Edited August 23, 2021 by Nick Gough

[AdamsRadial]

4 hours ago, Nick Gough said:

As you say the heads are rounded, so I had to use pliers.

I managed to get a small collet chuck to grip after rally tightening the thing up.

[The Johnster]

6 hours ago, lofty1966 said:

Don't the crankpins just pull out on the older 61xx models?

 

This occurred to me lying in bed this morning while I was gathering momentum to actually get up.  I will try again later.

 

4 hours ago, Nick Gough said:

The crankpins on the centre drivers definitely should unscrew - I had to replace damaged con rods on a couple of mine.

 

As you say the heads are rounded, so I had to use pliers.

 

I haven't tried but I would expect the pins on the other wheels to also unscrew.

 

I may need better quality pliers, then; mine are slipping over the shoulder of the crankpin heads and it is difficult to get a grip to actually turn them.

 

1 minute ago, AdamsRadial said:

I managed to get a small collet chuck to grip after rally tightening the thing up.

 

A very good idea and may well be the answer that gets me out of this mess; thank you, sir!

 

I think I need some sort of spreader to deal with removing the wheels from the axles; it is not a problem if they are damaged in the process as I have no further use for them, but of course I do need to preserve the nylon cog gear if I am to use the original motor. 

 

If push comes to shove I can saw the wheels off the axles.  Nil desperandum.

[lofty1966]

2 hours ago, The Johnster said:

This occurred to me lying in bed this morning while I was gathering momentum to actually get up.  I will try again later.

 

 

I may need better quality pliers, then; mine are slipping over the shoulder of the crankpin heads and it is difficult to get a grip to actually turn them.

 

 

A very good idea and may well be the answer that gets me out of this mess; thank you, sir!

 

I think I need some sort of spreader to deal with removing the wheels from the axles; it is not a problem if they are damaged in the process as I have no further use for them, but of course I do need to preserve the nylon cog gear if I am to use the original motor. 

 

If push comes to shove I can saw the wheels off the axles.  Nil desperandum.

I use mini snips as the bevelled edge slips under the head of the pin.

Just don't close them right up an snip the pin head off. 

[1466]

On 23/08/2021 at 17:05, lofty1966 said:

I use mini snips as the bevelled edge slips under the head of the pin.

Just don't close them right up an snip the pin head off. 

I converted  a couple Airfix 61xx  to EM EM gauge 30 odd years ago .

The crank pins  do pull out as others have said .

I reused the original Airfix drivers on one , to represent the smaller wheels . I seem to recall supporting the wheels in a vice and drifting them off the axles with a hammer and drift .

I hope this helps and look forward to seeing more .

Ken 

 

[The Johnster]

More good ideas, and much to mull over.  Thanks again Lofty and everyone; the site is performing magnificently as a problem solver in the best of it's traditions; the collective are going to be invaluable during this project!

 

Snipping the heads off may be the way to go, since these wheels are going to be surplus, and I will need new crankpins for the 21mm Markits replacements anyway, and it would enable me to save the motion for re-use.  I will report back later or tomorrow on how I get on this evening, but even with the crankpins beheaded, I will still have to find a way to force the wheels off the axles, or resort to hacksawing them in half so that they fall off.  The project is predicated on re-using the Airfix chassis block/mech, axles, motion, and a good part of the body for easyness and money saving; I will have to fabricate new cab side sheets, front and rear spectacle plates, and roof but these sound like jobs within my comfort zone. 

 

Of course, Comet, Southeastern, and High Level all provide chassis compenents that are suitable, though High Level are probably beyond my capability.  And I would have the opportunity to provide my own motor and gears so that more cab detail could be included.  But there is a limit to how much this sort of t*rd can be polished, or how much time, effort, and cash it is sensible to spend; to match the quality of a Comet or Southeastern chassis one would want to be doing a dead scale scratchbuild of the rest of the loco, and while I want a passable 3100 to run occasionally on Cwmdimbath, I am not really keen enough to go to the amount of expense, work, and time needed to make a 'proper' scale model.  That said, I would be very tempted by an RTR 31xx to current standards; I am just not very hopeful that anyone will make one. 

 

OTOH, the Churchward 3150 out of which the Collett 31xx were rebuilt are, by current standards, fairly low hanging fruit; a class of 41 is a reasonable size and they were fairly well spread around the GW geographically on the red routes and lasted until the late 50s.  Should any producer or even kit manufacturer read this and think to themselves 'ecky thump, that's a cracking idea, Johnster, we'll make one', I'd be very tempted by this loco as well, with a view to converting it to Collett 1938 31xx specification, but it would almost be as much work as this project; new wheels, cab sides and spectacle plates, and the tanks lowered with the boiler standing a little more proud of them than the 3150.  Sadly for me there were none of these heavy prairies at Tondu.

[The Johnster]

Thought I'd posted the above  on Monday, but clearly I didn't; apologies for any resultant apparent chronological inconsistencies.  My usual inconsistencies are not included in the above apology, and I apologise for them separately...

 

OK, hostilities continued this evening and were extremely hostile, to the point of brutality and thuggishness; anyone of a delicate disposition or the sensibilities of a finescale modeller should probably find something else to read.

 

If you're still here, you are a tough old bird or don't rate your own modelling skills that highly, and when you finish this screed you may realise that you are better than you thought you were once you've seen what a real bodger can do!  I have managed to further dismantle the wheels and motion.  I was going to attempt to snip the crankpins, but having got the snips behind them, thought I might as well have a shot at levering the motion upwards, firstly at the ends of the coupling rods, and away they came.  Heartened, I did the same to the centre ends of the coupling rods and the big end of the connecting rod; success.  Found a sealable bag to keep them safe in in the project box; rods, crankpins, and spacing washers. and then removed the brass whistles to go in the same bag; it may well be some time before we encounter these items again...

 

Then I turned my attention to the wheels, and found that by gripping them with a chunky pair of pliers I could get the other wheel away with the axle attached by pulling and twisting.  The same technique but with the pliers on the axles got rid of the other wheels, which were now useless for any further purpose as I have destroyed the square plastic axle receptor holes. and have beem binned.  The axles, all rescued for re-use on 3100, have square ends which I am hoping will accept Markits 21mm wheels, and they have been put in the sealable bag for safe keeping.  The nylon gear will not be harmed by a good cleaning up, but seems in good condition with little wear; all the cog teeth are level and a consistent width throughout their length.  This is very re-assuring for such an old chassis.

 

Now we get to the brutality.

 

 

 

A combination of hacksawing, making repeated xacto cuts, and pulling things around, has removed the rest of the boiler, firebox, cab front and rear, cab roof, and coal.  But the structure was already somewhat flimsy and the inevitable heavy handedness of the job has caused splits and a broken section in the tank tops, all of which will have to be made good when 3100 is built.  The structure in the photo will form the tank and bunker, and cab cutouts of 3100, and new front and back spectacle plates and a high dome roof will either be cobbled from 42xx or even 56xx bits if I can find a cheap body, or fabricated.  Fillets will need to be inserted between the tops of the cab sides and the new roof, a very noticeable feature of the Collett 31xx which is part of the look and character of the loco. 

 

The tanks/cab sides/bunker/running plate piece needs of course to be tidied up and the round boiler support flange plates at the front of the tank area (I'm assuming that's what they are)  removed.  The next part will be to acquire a no.4 boiler of some description and fettle the 'piece' until the boiler can be made to sit happily level between the tanks at the correct centre line height above the rails, or as close as I can get it, again a vital component of the distinctive character of the Collett 31xx.  It will have to have a lot of material cut away behind the support flange plates at the tank fronts to clear the Airfix chassis block and mech, but this should be a lot easier than the butchery to the 'piece'.  The 'piece' is seriously flimsy in it's current state and I intend to handle it as little as possible until the boiler try fit.

 

The next job then will be to reconstruct the chassis and mech; I'll give the motor and wiring a full going over as well.  Markits 21mm wheels will make it sit about a scale 2.5" lower than the Airfix wheels, assuming those were correct for 5'8"; I haven't measured.  In any case 21mm is spot on for 5'3", correct for 3100.  I intend to re-use the Airfix pickup cradle, and will have to give the chassis extensive running tests to ensure ground clearance. 

 

Then we can embark on the assembly of 3100.  I am not clear at present if this will be best done with the 'piece' and the boiler pre-assembled as a unit, and there seem to me to be pros and cons both to fitting the 'piece' to the chassis before the boiler is fitted, or as an assembly.  The loco must ride at the correct height at the buffer beams, and this will be achieved by spacer pieces on the chassis block top on which the 'piece' will sit, probably secured by my usual bodge method of pound shop superglue, bond easily broken if one needs to get the thing apart.  The biggest visual drawback will make it's unavoidable presence felt at this point; there will be an inauthentic gap between the valance and the top of the cylinders, which will be set too low.  The 'piece' will be much stronger with the boiler fitted to it, but there might be some case for making the boiler unit removeable to get at the innards rather than taking the whole body top off. 

 

At that point I should have a running chassis on top of which is the 'piece', with or without boiler, and the drop part of the running plate at the front.  I will then be able to make some decisions about cab detail, and the cab front/roof/rear.  It is possible that this could be an assembled unit from a 42xx or 56xx, but more research needs to be done.

 

That's the story so far tonight; progress, but shocking brutality!

[The Johnster]

4 hours ago, 1466 said:

I converted  a couple Airfix 61xx  to EM EM gauge 30 odd years ago .

The crank pins  do pull out as others have said .

I reused the original Airfix drivers on one , to represent the smaller wheels . I seem to recall supporting the wheels in a vice and drifting them off the axles with a hammer and drift .

I hope this helps and look forward to seeing more .

Ken 

 

Yes, as I now know the crankpins just pull out and the wheels can be pulled off the axles.  Your mention of the original Airfix drivers on one loco, to represent the smaller driving wheels, suggests that they are in fact 22mm to represent 5'6" driving wheels as fitted to the 81xx class.  This would play in my favour, as there would be less differential in the 'sit' of the body piece needed to keep the buffers the correct height above the railhead on a chassis running on 21mm wheels to represent 5'3".

 

This does help, thanks, and I hope to provide you with more to see fairly soon, but I am expecting matters to be delayed for a while now while I investigate the new wheels, and will have to wait for pension day next Wednesday to buy them!  As I've said, next job is to clean up the remains of the Airfix body and cut out the boiler support flange plates. 

 

I broke my vice and haven't replaced it yet, but am managing without thus far.

[1466]

On 23/08/2021 at 17:05, lofty1966 said:

I use mini snips as the bevelled edge slips under the head of the pin.

Just don't close them right up an snip the pin head off. 

I converted  a couple Airfix 61xx  to EM EM gauge 30 odd years ago .

The crank pins  do pull out as others have said .

I reused the original Airfix drivers on one , to represent the smaller wheels . I seem to recall supporting the wheels in a vice and drifting them off the axles with a hammer and drift .

I hope this helps and look forward to seeing more .

Ken 

8 hours ago, The Johnster said:

Yes, as I now know the crankpins just pull out and the wheels can be pulled off the axles.  Your mention of the original Airfix drivers on one loco, to represent the smaller driving wheels, suggests that they are in fact 22mm to represent 5'6" driving wheels as fitted to the 81xx class.  This would play in my favour, as there would be less differential in the 'sit' of the body piece needed to keep the buffers the correct height above the railhead on a chassis running on 21mm wheels to represent 5'3".

 

This does help, thanks, and I hope to provide you with more to see fairly soon, but I am expecting matters to be delayed for a while now while I investigate the new wheels, and will have to wait for pension day next Wednesday to buy them!  As I've said, next job is to clean up the remains of the Airfix body and cut out the boiler support flange plates. 

 

I broke my vice and haven't replaced it yet, but am managing without thus far.

A bit more detail , in case it helps .

I reused the original Airfix drivers to represent the smaller wheels of the 81xx  class .BTW , the earlier production runs had flangeless centre drivers and I replaced those with flanged . I may even have pushed the metal tyres off the plastic centres  and then swopped tyres . It was 30 years ago so detail is hazy .

I see you used pliers but I had a small square of metal into which I cut a slot when drifting the wheels off .

Of course the axles were 1/8th diameter which was the norm then rather than  today’s 3 mm. I cut longer EM gauge axles from silver steel rod ( Eileen’s).

I dimly recall an article in the old Airfix magazine on doing this conversion.  In that case I believe the boiler came from a Kitmaster  City of Truro . Anyone remember which edition?

Great project . Innovative approach.

Ken 

[The Johnster]

Possibly insane approach, and you are being very diplomatic...  Fun project so far certainly so far, though, and potentially very satisfying.  The finished product may possibly inaccurate in some dimensions and details, and the crosshead area will be a definite visual weakness, but I reckon I ought to be able to cobble together a passable impression of the distinctive character of these thugs. 
 

More valuable info to thank you for, Ken, confirmation that the axles are 1/8th diameter and that therefore Markits 21mm wheels should be fittable to them.  I sort of knew I could remove Airfix wheels from the axles because I replaced the traction tyre ones on both this ancient chassis an a 14xx back in the day, but have long forgotten how I actually did it! 

3100 may possibly end up with a CoT kit no.4 boiler; it’s dimensionally correct and the inappropriate bits are hidden by the tanks.  A Mainline 43xx is a better deal though, as the handrails and steam pipes are done for you.  The chimney would need replacing with a copper capped version for 3100 if I use a 43xx, and CoTs is far too slender and graceful.  Bit of research needed on this point, but there’s some time before it becomes a matter of urgency.  31xx is parallel, and quite stout in proportion, not that Johnster holds any moral high ground in this matter. 56xx may be close enough for jazz…

[The Johnster]

Have bought a Bachmann 43xx body on the 'Bay, which will be the boiler donor, and possibly contribute the front buffer beam as well.  Should arrive by the weekend, and I can start what is probably going to be a faffy fitting and fettling process to sit it between the tanks and get it level at the right height.  Next job is to order the wheels, and begin assembling the rebuilt chassis, though in the mean time I should probably check out the motor and gears for free running, deep clean and new lube. 

 

This mech has not run for some years, since it's plastic slide bars went the way that all Airfix plastic slide bars eventually do.  The original body piece was binned when I acquired a more recent (not the current model) Hornby loco which had been retooled with a much more plausible smokebex door (the current 4145 in service on the layout), but the last time I could swear this mech ran was about 4 years ago.  It was not a bad runner at that time though noisy be modern standards.

[The Johnster]

Just ordered the wheels, Markits from Wizard, gone for 20 mm 16 spoke insulated.  Slightly underscale (Wizzo don't have 21mm in stock), by a scale inch diameter, but within high mileage wear tolerances and it will help to make the point that this is not a 3150 or even an 81xx.  Wizzo list this wheel as correct for 31xx, and presumably are referring to the Collett 31xx not the Churchward 31xx, which had 5'8" wheels.  The overall cost on the project is up a bit now, £57 spent so far, but the wheels are probably going to be the biggest single hit.  I'll need buffers, a chimney, and possibly some handrail knobs; the rest is in stock, and of course number plates; I reckon I can bring her in at around £80, not bad for a working loco with a reasonable level of detail.  I would guess an RTR would be about twice that, but would be much better detailed and a better runner of course.

 

Work on hold for now awaiting the new boiler for the body and wheels for the chassis, will update when there is something to talk about!

Edited September 2, 2021 by The Johnster

[The Johnster]

Bachmann 43xx body arrived this morning courtesy of Royal Mail, and I will probably attack it with the slitting discs this evening.  The no.4 boiler is the name of the game here, and the rest will probably be binned.  It's a reminder, as was the Airfix 61xx body, of the days when locomotive bodies were one-piece mouldings, often of some ingenuity.  I think it was Lima who broke the mould (sorry) as I know thier 94xx has separate components for the running plate and the boiler/tanks/cab/bunker peice; I assume the J50, which preceded it, is similar.

 

The boiler, which I think of as the boiler assembly because it includes the smokebox and firebox, once removed from the rest of the piece, will have to be cut away considerably, and I am expectning all of the area hidden by the tanks to be removed.  The exact area to be removed will not be determined until the final fit of the assmbly in the cradle formed by the tanks and 61xx running plate forward of them is settled.  There may be some fettling to be done before the completed 'body unit' clears the Airfix chassis block and motor; I am expecting problems with this because the whole sit is different to the 61xx and the Mainline plastic is thicker than the Airfix, and it's all going to get a bit bodgy and messy in there!

 

I think the 43xx body will be able to provide sufficient handrail knobs for the extra handrails needed, cab door and so on.

 

I'm getting into the swing of this project now, and starting to enjoy myself!

[DCB]

Just wondering if the 43XX footplate and boiler with 61XX tanks grafted on would make a better starting point than a 61XX with the boiler chopped out.  However I am trying to make a 3150 from a Grafar OO 61XX body  so maybe take my suggestion with a large pinch of salt.   

A Bachmann 43XX chassis works very nicely under a 61XX until the wheels fall off.  We have just about every iteration of the Arfix / Hornby 61XX and only the latest 61XX runs acceptably without mods.  I put romford wheels, brass axle bushes, packing pieces to keep the worm wheel centred, an X04 motor and Triang gears to one Airfix chassis but it still can't equal a Hornby Hall chassis with Romford or H/D 2-6-4T wheels and a 5 pole motor for the smooth running I need as my Prairies are mainly used as bankers.

Edited September 4, 2021 by DCB

[The Johnster]

You may well be right, but it’s too late now; I’ve cut the boiler.  I’ve decided to do it by fitting the 43xx boiler in to the 61xx ‘body’ to attempt to get the rather odd proportions of the Collett 31xx right, but I’m not sure that the result will be dead accurate.  The issue is that, because the smaller driving wheels effectively lower the body by scale 3 inches, a millimetre, it has to be raised by this amount to get the buffers to the correct height while reducing the drop in the running plate ahead of the cylinders.  The 43xx relationship between the boiler and running plate is correct (I think!) for a 3150, but the Collett 31xx rebuild is not quite the same as a 3150 with smaller wheels; it ‘sits’ differently and has a higher domed cab roof. 
 

3100 will be a cheap’n’cheerful mongrel, hopefully close enough for jazz, the offspring of a probably ill-advised night of passion involving an Airfix 61xx, a Bachmann 43xx, and a Mainline 56xx.  The 61xx mech involved is very old, but not a bad runner; it is noisy though.  It hasn’t run for some time and will need a good seeing to, though. I find these old Airfix chassis to be acceptable in terms of smooth stops/starts and good controllable slow running once the traction tyre is binned; haulage is not an issue at Cwmdimbath.  They take about 30 years to run in properly, though, just before the plastic slide bars give out...   I have one in service, picked up cheapish from a stall at the Wales/West show at Thornbury 4 years ago and with a later Hornby body, the one with the better smokebox door, sitting on it.  I also have the current Hornby, which is in a different league.  The Airfix chassis loco would probably pull two current Hornbys backwards, though!

 

The Grafar is actually an 81xx, and I have no idea what Spaniards that throws into the works.  The difference in wheel diameter is only scale 2”, though, assuming the Grafar and Airfix wheels are to scale, and 2” is not far off the range of normal high mileage tyre wear in service. 
 

More fun later; I’m going to try to get the Mainline boiler to fit between the Airfix tanks, and there will no doubt be gratuitous profanity a-plenty…

 

 

 

 

Edited September 4, 2021 by The Johnster

[The Johnster]

 

Photos of this evenings' destruction/progress, trial fitting the boiler into the tanks/running plate unit, and a shot of the loco body (now recognisably a 31xx to my view, with the boiler sitting correctly lower to the running plate and giving a general feeling of bulk and brute power) lined up against the Airfix chassis block showing marks for the area of metal to be removed if I am to retain the backhead detail of the 43xx boiler.

 

There will be a good bit of making good work to do.  I have rescued the lubricator/boiler support plate pieces from the 43xx, and I may be able to get away with 3100's shorter safety valve cover by sawing it's top off, filing the stump down a bit, and glueing the top back on; of course, if this doesn't work, I'll need a new safety valve cover!  There will be a good bit of filling between the tanks and the boiler, and I will need new tank front footsteps as well. 

 

I've taken as much plastic as I can away from the boiler where it is not visible behind the tanks, and was amazed at the thickness of the tooling here.  I'm having second thoughts about using a 56xx cab and bunker, as it will need a good bit of surgery to accommodate 3100's higher (but not as high as a 61xx) running plate; it may be better to fabricate scratch build cab front and rear bulkheads and the roof.  I'll have a bit of a play around lining the two bodies up against each other before I commit.  3100 has a distictive area of plain cab side between the top of the cutout and the 'eaves' of the roof, about 6 inches, 2mm on the model, and with rivet detail!

 

Anyway, that's the current state of play, and I'm happy with progress.  The chassis is on hold as the front pony and cylinder block are still pending from Hornby, and the driving wheels have only just been ordered from Wizard, so it is hardly fair to expect those yet!  I'm getting concerned about the Hornby order, which also includes a GLV, as they said they would email me when it was dispatched, which they haven't. but I got an email last night from them asking if I was satisfied with my order.  Order went in on the 20th of August, 2 weeks ago.  Digging in to the site to find a way of contacting them, I got a page saying that I should contact the dealer that I ordered them from, but I ordered direct on the website, not through a dealer.  I'd be happy to wait patiently for a week or so more, but last night's email has worried me!  I'll phone them on Monday to check all is well...

 

I will be able to start to assemble the body unit, though, and try fit it to the chassis block to establish that there is motor clearance.  Final fitting will not happen until the chassis is rebuilt with the new driving wheels, though, in order to establish the correct height at the buffers.

[The Johnster]

Cylinder block/slidebars (actually for Hornby Grange) and front pony (actually for 42xx) delivered this morning, along with the GLV.  Onwards and upwards, or in my case probably sideways...

[The Johnster]

More goodies today, in the post this time, the wheels are here!  20mm Markits, should be 21mm but we've discussed this earlier.  Too hot for modelling so I'm waiting for the weather to break and things to get a bit less humid and sweaty before continuing.  But I have enough components to carry on with both body and chassis for now!  Once I've fitted the wheels to the axles and try-fitted the chassis block on top of them, and the body is completed, I can try-fit it for 'sit', the main task being to get  the buffers at the correct height above the railhead.  We should finish up with a loco that a) sits at the right height at the buffers, b) works, and c) looks reasonably like 3100.  I'm feeling quietly confident at the moment; I'm sure there will be problems I haven't foreseen, but there should also be unforseen solutions to them.  Of course the perfect situation would be to have foreseen solutions to the unforeseen problems, but I'm not sure how to manage that...

[The Johnster]

 

Try-fitting and intial re-assembly of body parts.  The new body clears the motor and sits perfectly well on the original Airfix chassis block, and the combination of the larger boiler and the 56xx cab roof/front/rear is already giving the loco a bit of a 31xx feel, even before I have made good the gaps and missing bits!  It is very clearly a departure from the usual large prairie form, even the 3150, and some of the squat brutality of the original is, I think, evoked. 

 

Pleased with progress but there is a very long way to go yet!  Not a race, though, and I'm in no tearing rush to finish the loco, progress will take place as and when I'm in the mood.  Good bit of filling and making good to do to the body, as well as replacing handrails and getting rid of the old moulded ones.  Cab detail may not be possible, or a compromise of just the upper half of the backhead sitting on top of the Airfix chassis block, with the 56xx rear casting.  New top furniture (parallel chimney, lower safety valve cover, new whistle), new tank top detail, buffers, vacuum pipes, lamp irons, smokebox dart, front steps, cab front is already glazed with Glue'n'Glaze.  Oh, and a Modelu crew.

 

A minor problem will be that the brass worm will be visible beneath the boiler ahead of the tanks, but the alternative would be skirts and I think the worm is the lesser of evils.  3100 is the illegitimate offspring of 1970s and 1980s models, so one cannot expect 21st century standards!  Painting it matt black will help...

 

 

[The Johnster]

Doing a bit of research last night and found out that I’m going to need new front pony wheels as well.  The 31xx had 3’ diameter as opposed to 3’2” on all the other prairies.  No biggie as I’d intended new pony and trailing wheels anyway, as the current ones are still the old solid backed Airfix, but I’m glad to have discovered this before ordering them!

[The Johnster]

Driving wheel axles have arrived, so there may be a little more progress may take place over the weekend to report on and take photos of.  Nothing has been done to the chassis since I stripped the wheels out of it, so this is a bit of a turning point, where I stop destroying stuff and start making stuff.  Onwards and upwards, or more like downwards and sideways in my case...

 

Cost is now about £62 all up.

[The Johnster]

Cog gear is a nice tight fit on the Markit axles and I put the wheels on yesterday evening during a running session.  Can’t find my ancient Romford axle nut driver so they’re only hand tight for now.