4mm Ivatt Class 2, 2-6-2 tank in P4

Dave Holt

Western Thunderer
As a relative newcomer to WT, I hope this is the appropriate place to write about my latest loco building project, which is to finally complete a model which has remained part done for quite a time. If it should be posted in "Workbench", I'm sure someone will advise me accordingly.
Early in my loco modelling life, I maintained the discipline of not starting a new project until the previous one was complete. Unfortunately, I failed to maintain this situation and ended up with several part completed locos in various states. A year or so ago, I resolved to finish these off before starting anything new and the Ivatt is the last to be tackled, despite probably being the first one started. Unfortunately, I didn't date my earlier sketches or notes, so I'm not entirely certain when this loco was started, but I found a letter relating to possible etched pony trucks dated 1995! I'm not sure if physical work had commenced, then, but I was clearly thinking about it and making detailed plans. I'm always amazed when people post about locos assembled in a matter of weeks, but even by my standards, this has dragged on a bit. Quite a few locos have been built during the period since this one started but this could still be a record for an extended build.
The basis for the model is a Bachmann body, which will be suitably modified and detailed, mounted on a chassis made from a Comet kit. The loco reached the stage of being a runner many years ago but never progressed to have the cosmetic details added. Here it is in that condition, with its near sibling BR Standard version partially visible in front.
Ivatt_2T_001.JPG
The BR Standard was completed late last year and appeared in its final state in my first post in the Newcomers section.

Work to complete the Ivatt has concentrated so far on finishing off the chassis by adding such items as buffer beam gussets, front and rear steps, sand pipes and the injectors and associated piping. A number of these details have been made with the aid of custom etchings, produced from my sketches, by Rumney Models.
Except for the cylinder drain cocks, all the chassis parts are now completed, ready for painting. The following photos show the whole set of parts and some of them in detail. I hope they are of interest.
First, the set of components.
Ivatt_2T_008.JPG

The frames are arranged to provide fully floating compensation for the driving and coupled axles with the pony trucks being sprung against bearing pintles, fore and aft - as per the real thing. The frames also carry the steps, injectors and piping, steam heating hoses, the pick-ups (which bear on the tops of the driving wheels) and Alex Jackson couplings.
Ivatt_2T_009.JPG
Ivatt_2T_010.JPG
Ivatt_2T_010.JPG

The injectors were rather fiddly, consisting of twenty odd separate pieces as no suitable commercial casting are available, as far as I know.
Ivatt_2T_011.JPG
Wherever possible, I try to use a removable keeper plate to retain the driving and coupled axles, as in this case. The keeper also carries the rear sand boxes, sand pipes and their support brackets, ash pan and hopper operating mechanism and, in this case, the pony truck pivot points.
Ivatt_2T_012.JPG

The brake rigging is spit into two sections because, inconveniently, the rear, single pull rod has to pass through the "A" frame of the rear pony truck. The front section becomes entangled with the front sand pipes and brackets, meaning the two assemblies have to be juggled into place together. Inconvenient, but unavoidable.
Ivatt_2T_013.JPG
The cylinders and valve gear are assembled as a single unit, which also includes the motor torque reaction arrangement. The up-stand has a pivoted link which connects to the gear box, preventing rotation of the latter but allowing for suspension movement. I've tried to represent the support brackets and integral splashers on the slide bar braket and reversing shaft supports.
Ivatt_2T_014.JPG

The driving and coupled wheel sets are Alan Gibson parts but fitted with modified Ultrascale crank pin bushes. The balance weights are again custom etches as all the readily available items were the wrong shape and size.
Ivatt_2T_015.JPG
Finally, the two pony trucks. Unfortunately, my 1995 discussions about etched version came to nothing, so in the end, I had to make my own, using the basic Comet "A" frame with hand made parts to turn them into representations of the spring and swing link side control types fitted to these (and the BR Standard) locos. For whatever reason, the Ivatt appear always to have the swing link at the front, whereas the Standards had the spring control at the front. This latter type was also used on Ivatt and BR Standards with just a front truck (2-6-0's, 2-6-4 tanks and 2-10-0's). Subsequent to me making these trucks, Brassmasters produced the spring control type for their Flying Pig chassis and I used these (one modified to represent the swing link type) on my BR Standard 2 tank, which save a bit of work. The trucks have the axle sprung with two hair pin wire springs, reacted against the bering pintles previously mentioned.
Ivatt_2T_016.JPG
So, just the drain cocks to do, then onto the body. Needless to say, there doesn't appear to be a commercial source for the style of drain cocks fitted to Ivatt locos, so scratch building will be required. Fortunately, I had to do the exact same cocks on my Caprotti Black 5, so I at least have an idea how to replicate them this time.

Dave.
 

LarryG

Western Thunderer
Having done all the donkey work on the really neat chassis and produced the bees-knees, I would be tempted to knock up a brass body rather than gold-plate the elderly Bachmann body. I had to marry a Bachmann Ivatt 2-6-0 boiler and chassis to the older tanks and bunker before I was satisfied.
 

Dave Holt

Western Thunderer
Larry,
Your solution sounds quite drastic although I seem to recall the result was very good. The problem is that I'm not aware of an accurate brass or metal body for the this loco. The DJH I used for the Standard was 2 mm short and required a stretched cab, but was still not really right. At least the Bachmann body is dimensionally very good and fits my chassis, so I think I'll stick to trying to gold plate it, as you say.
Dave.
 

Dave Holt

Western Thunderer
Very nice, Larry. Funny, I've got some coaches that look quite similar to those! For purely alliterative purposes, perhaps it should be the 'Holt Horse'?
 

P A D

Western Thunderer
Hi Dave,
Welcome to the "Dark Side". The Ivatt chassis looks very nice. I don't know how you 4mm boys can do such complex work on such small models. I wasn't aware of the pony truck variation that you mention, so I might have to revisit that area on the one I built for my brother.

Area 51 is the correct place for your thread. What's on your workbench is more for intermittent posts on various projects rather than complete builds. Now if you had put it in "God's Wonderful" forum, that would have been a heinous crime! :)

Looking forward to seeing more of your builds.

Cheers,
Peter
 

LarryG

Western Thunderer
'Holt Horse' doesn't have the same ring about it ha ha. 'Dobcross Dobbin' if you called your station Dobcross, which I think it was nearer to than the actual Delph village. I did a Google Earth this morning and could barely see the old station buildings for trees and properties. It's the same in Wales. Open vistas that we saw as children are now hidden by curtains or forests of tall trees.
 

Peter Cross

Western Thunderer
I did learn that the ponies were different side control. But there did not seem to be an answer to which way around they went.
 

Dave Holt

Western Thunderer
I thought I had more or less finished the chassis, apart from the cylinder drain cocks - still not started. However, the marvelous set of photos posted by PAD, in Gallery, showed that I had missed the ash pan damper and duplicated hopper door linkage on the RHS of the ash pan. Checking the LMS GA, I could see that these items were shown, but not quite as seen on the preserved example. The drawing shows the hopper link to be horizontal rather than sloping and the damper rod to be flat bar rather then round.
I've now added rough representations of the versions shown on the GA drawing to the keeper plate unit. Unfortunately, my efforts to illustrate the results have been an abject failure - just can't get to grips with the macro facility on my camera or get adequate lighting for such close up photography.
Dave.
 

LarryG

Western Thunderer
Hi Dave,

Rest the camera on something solid and close the aperture down to in maximum (f22 or something). You will be left with a longish time-exposure but this doesn't matter if the camera cannot move. I shoot in all lights when doing a workbench. As for getting close up, you have a macro facility. I have to use additional close-up lenses. The resulting images are good enough for a low resolution computer screen.
 

Dave Holt

Western Thunderer
Thanks for the advice, Larry. I have to confess that I've never mastered all the facilities on my camera and basically just take snaps.
Anyway, I've had another go at photographing the new levers on the ash pan with reasonable success (I think).
Ivatt_2T_017.JPG

You can just about make the two levers out. They are much simplified, being a single layer of spare etch and are attached direct to the side of the ash pan, whereas they should stand away by a mm or so. In the gloom under the loco, I think I can live with the result.
Dave.
 

P A D

Western Thunderer
Hi Dave,
Looks good. When its painted if will pass muster and add to the overall impression.

Glad the photos were useful.

Cheers,
Peter
 

Peter Cross

Western Thunderer
As larry say a high f stop number, and i use the timer as then there is no shake at all when the picture is taken. I fine it better than the remote button, less chance of snagging on the lead and breaking something expensive.
 

Dave Holt

Western Thunderer
After a period of reluctance to actually do anything, I've finally roused myself to make and fit the cylinder drain cocks and operating mechanism to the cylinder/valve gear unit. To be honest, my efforts probably fall into the "artistic impression" category, rather than a scale reproduction. That said, the results better represent the type of cocks fitted to these locos than any of the commercially available versions, that I am aware of. Just need to re-fit the front cylinders cover , which fell off several years ago, to the LH cylinder to finish the chassis parts.
Then to the body. Argh......
Here are some views of my efforts.
Ivatt_2T_018.jpg
Ivatt_2T_019.jpg
Ivatt_2T_020.jpg
Dave.
 

paulc

Western Thunderer
Hi Dave , is the omega loop at the rear of the front pony to keep it on the track ? Great idea , i might have to try it . I have a DJH A4 that has its own mind as far as corners are concerned.
Cheers Paul
 

Dave Holt

Western Thunderer
Hi Paul.
No, the loop you can see is in the side control spring, which extends inboard of the trucks and engages in a hole in the keeper plate. The truck axles are sprung within the truck itself. You can just make out part of the springs either side of the axle. This sketch shows the idea, in rough form. There is a second spring mounted diagonally opposite, bearing on the other end of the axle (not shown). Unfortunately, there's no science to the forces involved. For my 4 mm models, I use 0.33 mm brass wire and provide about one and a half turns in the coils, to give a bit more effective length to the spring.
Pont_truck-spring_sketch.jpg
I've had a rather frustrating morning with the chassis. First, I dismantled it ready for cleaning and noticed that the drain cock operating rods had each come adrift at one end, probably due to me tweaking the cross shaft stub ends to align with the centre section. I then decided I really should make some effort to represent the lubricator drive mechanism. Whilst handling the cylinder assembly, I found that the slide bars on the RHS had become detached from the motion bracket. So, the cylinders were fitted to the frames to hold the parts in the correct position for re-soldering. This was done satisfactorily but in handling the chassis, one of the drain cock rods came off completely. Obviously not very well soldered! Anyway, all is now well attached and shouldn't cause any further issues. Better to find this sort of thing before painting so perhaps it's all for the best.

Dave.
 

Dave Holt

Western Thunderer
I've now fitted a representation of the lubricator drive linkages which showed slightly more prominently than I had thought on the detailed photos posted in Gallery by PAD. I practice, at 4 mm scale, they don't actually show that much, with the main drive rods being inboard of the valve gear, but at least they're there now. I'm fairly sure that all the detail work on the chassis is completed, so it's now on to stripping, cleaning and painting.

These photos show my efforts with the loco partially assembled to check clearances and running as an 0-4-2-0 and cut down bunker arrangement!

As originally assembled, the lubricator drive rods came perilously close to the oil boxes on the front coupling rods and had to be moved up, slightly, at their front ends. Running clearance is now acceptable, even with the wheels at maximum rock.

Ivatt_2T_021.jpg
Ivatt_2T_022.jpg
Ivatt_2T_023.jpg
Ivatt_2T_024.jpg
Dave.
 

P A D

Western Thunderer
Hi Dave,
I'm a bit late on this, but if it helps, I can scan the article from MORILL and send it to you. It has a very nice set of 7mm drawings.
Just let me know.
Cheers,
Peter
 

Dave Holt

Western Thunderer
Peter, that's a very kind offer but I already have that magazine, thanks. As you say, the drawings are very good and provided me with vital information on the push-pull vacuum control gear. Luckily, the article also has partial 4 mm scale drawings, too, so it saves an awkward 7 to 4 scale conversion. The VCR equipment does not feature on the LMS GA drawings I got from OPC many years ago. I presume there were some additional drawings I failed to spot and purchase.
On to the body now. Gulp!
Dave.
 

Dave Holt

Western Thunderer
Well, not quite straight on to the body.
I had noticed that the RH return crank was tightening up some way beyond the desired angle. I thought I could correct this by building up the back face of the inner crank pin bush with superglue which, when set can be filed back to allow just the right tight position. Unfortunately, whilst rubbing the back face of the bush to remove oil residue, the bush pinged out of the tweezers across the work tray, or so I thought. This forced me to have a thorough clearance of said tray - much overdue I have to say. Despite searching the mass of debris for an hour or so, no bush could be found - loads of other useful stuff - screws, washers, a hand rail knob, etc. Reluctantly, I resolved to make a new bush from spare Ultrascale bits - a short tube and a rear washer, soldered together and the back protrusion filed flush to make a top hat shaped bush. It didn't take more than a few minutes. Much less time than I spent looking for its predecessor, but at least I've now got a clear work area!
The new bush did result in the return crank tightening at just the right position but the back washer must have been thicker because the return crank now fouled the eccentric rod. The rear washer was filed thinner and by good luck, the reduced length bush again gave just the right orientation but without the fouling. Just luck or inspired judgement? Quit whilst you're ahead I say.
No modelling for a few days now as I'm off to the Ffestiniog Railway for the WHR Gala.

Dave.
 
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