Project 65033 - a 3D printed LNER J21

[Daddyman]

A sensible approach, Paul.

So how good is the surface on this?

[Paul_sterling]

A sensible approach, Paul.

So how good is the surface on this?

Hi David,

Really good to be honest. I print them at an angle, which divides up the pixelating over several layers, meaning curved surfaces come out well.

As well as that, once the model is cleaned post print, I rub it over with a paper towel whilst its not fully cured, which helps to flatten out any minor ridges, so once cured, it needs barely any sanding at all. In fact a couple of those I've sold, the owners have gone straight to priming, no sanding at all.

Paul.

[Daddyman]

Sounds (and looks) good. So it's a PM to buy one, is it?

[Paul_sterling]

Sounds (and looks) good. So it's a PM to buy one, is it?

Yes please, I'll need to know which one of the 4 options you'd like, and I can send you the paypal details.
Cheers, Paul.

[Daddyman]

PM sent, thanks Paul.

[NZRedBaron]

What brands of primers would you recommend for this?

[Paul_sterling]

By and large I've never really stuck to any one brand. I prefer to use acrylic based primer, as it gives you more options about what goes on top of it.

I have used primer-filler on FDM based prints, to fill the woodgrain, but that is far less of an issue with resin printed models.

So I've used, Halfords, Plasticote, Rust-o-leum, and had no trouble with any for priming.

Top coats, I've used Humbrol (grasss green matt is a good match for LNER Darlington green once varnished), and Halfords Matt Black. Getting a "Black" looking black that doesn't look creamy or soft is surprisingly difficult.

I've used Railmatch, but found their green enamel isn't a good match for Doncaster Green, neither is the BR Brunswick. Their varnishes are excellent however, whereas Humbrol varnishes have to be pre-warmed and handled carefully, they bloom for fun.

Making sure the surfaces are clean is especially important with resin. A wipe over with IPA wipes/solution, and then a wash with cool soapy water is useful, and complete drying before painting, just to make sure no resin-IPA deposits are left on the surfaces or nooks and crannies. Don't use hot water, the resin will soften, especially on thin wall sections such as the cab.

Thanks, Paul.

[Atlantic 3279]

Our cheery postman has just brought me a well-packed, sturdy box containing printed bodies for both a J21 loco and its tender. Both are very neat with a surface finish that appears likely to require minimal refinement. I'm looking forward to the possibility of a project that might for once involve less time and effort than I initially expected. Fixing screws are even included. Excellent!

There might be a requirement for minor attention in order to prevent the tender sides from bulging out, but I'm sure that added internal bracing and/or a well placed relieving saw cut in the existing central cross-pieces will deal with that. As I’m a non-user of digital control and synthetic chuffing, should anything un-necessary on top of the tender chassis be in the way of added bracing, those un-necessary chassis-top parts simply be removed, although I don’t see much in the way unless somebody chooses to shoe-horn both a large chip into what ought to be the bunker space, and a speaker into the tank.

[Atlantic 3279]

After conferring privately with Paul, and re-examining the sides of the tender both by "sighting along" and by feel, I concluded that most of the slight splaying was below the level of the middle bulkhead. I'm not sure whether I'll achieve anything at this stage by simply supporting the sides firmly in dead-straight configuration for a few days while I get on with other things, but I'm trying that anyway. Paul also tells me that he is considering possible means of addressing this small problem at source on future prints.

I've used the smooth aluminium angle to protect the tender from the jaws of the vice, and I've only tightened the vice just enough to straighten the sides. That has put a very slight bend into the lowest part of the middle bulkhead. Vice jaws and alu angles quite handily are shallow enough to entirely miss the cornices and coal rails. Initially, I wondered why the sides were not straightening fully near the front, and then I realised that I needed to move my alu angles back clear of the beading on the front edges...

It may be that the printing resin has already cured too thoroughly for this simple attempt to correct the shape. If so, I might consider running some very hot water over the offending areas to soften the structure while it is held straight, prior to cooling again.

I notice in any case that there's actually enough space above the lip formed by the soleplate on the inside of the tank edges to accommodate a rigid strip of metal glued in place, if necessary, should that be needed to maintain straightness - and that won't interfere with anything on top of the chassis.

[Atlantic 3279]

I released the tender print briefly from the gentle grip of the vice last night. The sides appeared to stay dead straight rather than immediately springing out, and although judgement is highly subjective they seemed fairly stiff / rigid, so three or more days of firm support may have done the trick. The print is back in the vice for the time being, as I'm not yet ready to make a start on my J21. The "riveting" work on the D7 continues...

Paul: Only a thought - I'm fairly sure you would not want to digress into the realms of MS&LR / GCR locos to further complicate your CAD work, but I couldn't help noticing that if matters such as cab-sides, leading sand-boxes and the small question of round-topped of Belpaire fireboxes are ignored, the leading dimensions and general features of the J9/J10/J13/N4/N5 family are very similar to the J21/J25/N8/N9/N10 group. I know that there are, or have been, various metal kits for J10s and N5s. but anybody who might be shy about working in metal (and especially shy about building a chassis) could perhaps consider adaptation of one of your prints, using plasticard, to change the style to a near-likeness of the MS&L / GC types. If you model an early enough period you don't even need a Belpaire firebox top.

[Paul_sterling]

Hi All,

Apologies for being somewhat quiet the last few days, I've been away on business.

So, with Graeme's findings in mind, I have made some changes, as well as some discussions between myself and Danby Wiske.

First is the Tender. Much to my frustration, whilst I've been modifying the CAD, I've had bl**dy Love me tender stuck in my head, not a bad some, but not by any means Elvis' best.

With space above the tender lip which rests on the C-class tender, I've added some ribs. One or two tenders have bowed slightly, which I think is partly to do with the resin used, which is not the same resin on all of the shells sent out. I caught one other slightly bowed tender, but thus far, haven't had any further issues raised. Nevertheless, I'd rather dial it out now than later.

In addition to the ribs which will be permanent to the tender, I've added to the sacrificial frame, which in the pics attached, is orange. These horizontal props will stay in until the tender is cured, and may even be left in until the tender reaches customers, which I sometimes do with the loco props as well. They are best SAWN out rather than snipped, as snips always generate a little bit of lateral displacement when cutting, and that could cause a crack.

The second change has been on the Cab, which I've increased the roof thickness from 0.75 to 0.8, and reduced the timber plank chamfer depth from 0.175 to 0.125.the two braces that run across the cab have been deepened by 0.15mm as well. These seemingly minor changes are to increase the cab roof strength, preferably without removing the slender appearance of the cab.
Thanks,
Paul.

[drmditch]

Good Afternoon Mr Sterling

I've just sent a PM for enquiry; if you are being deluged with requests feel free to put mine at the back of the queue!

It might be worthwhile including some pictures from my thread, if only to illustrate the arrangement the NER used when this class and others were re-built with piston valves:

The only model I have seen showing the valve chest beneath the cylinder block (and clearly visible below the buffer beam) is mine!

I do really need to take some better pictures, and correct some faults - like the 'dropped 5' on the front buffer beam, and that gap under the cab roof!

This locomotive has all the detail I could think of, including working inside valve gear (well, the top half of it anyway) and all the outside brake rodding. It may not be perfect, but it does demonstrate the challenge a relatively small locomotive can present.

[Atlantic 3279]

After a prolonged series of diversions to outdoor activities, I have put Paul's printed bodies onto the chassis units from the recommended Bachmann SECR C class this evening.

I did notice one or two things before I began: The previously splayed lower sides of the tender body, which appeared to have stayed straight for a couple of days after release from a week or more in my vice, had reverted to splayed form, although it has to be said that now fitted to the tender frames they don't look bad. It was also apparent that the loco running plate had not remained flat between the leading and middle splashers. I found that I could correct that in the short term by dribbling hot water over that part of the structure to soften the material, moulding it to the desired form and then quenching with cold water to "set" the shape. What I don't know is whether it will retain shape. The drag beam of the loco and the front beam of the tender were also out of true, "inboard" around the cut-outs for the drawbar, but that will be impossible to see when the completed items are coupled together.
I suspect Paul mentioned that various things have to be done in order to get the bodies to fit the underframes, but here's what I found:
1. About 3mm has to be trimmed from the front of the loco chassis.
2. The "mouse entrails" (capacitors?) on top of the motor have to be either very carefully re-arranged to sit down as snug as possible, or removed entirely, in order to clear the underside of the firebox top. The short stiff wires attaching these components don't allow a lot of manipulation. I trimmed a little bit from the plastic rear motor bracket to allow things to sit where I wanted them, although an alternative would have been to de-solder the wires and re-solder them in a very slightly revised position.
3. The bore in the chassis for the rear fixing screw needs to be cleaned out to a true 2mm or slightly more, if using Paul's supplied new screws, otherwise it can prove difficult or impossible to get the rear of the body to "nip down" onto the chassis as the screw is turned, since the screw rises in the tight bore in the chassis, jacking the chassis way from the body...
4. For the tender, the moulded plastic boss for the original rear fixing screw in the chassis needs to be trimmed off fully flush with the top of the plastic chassis plate in that area. Even with that done, I found the new rear mounting lug arrangement an uncomfortably tight fit, at risk I thought of distorting the rear of the tender body. I therefore trimmed away the central portion of the chassis plate that should fit above the new lug, leaving only the thin metal stretcher for the guard irons, which flexes enough to fit comfortably above the new mounting lug. It would of course, I now realise, have been better to simply thin down the plastic chassis plate on its rear edge and put the metal guard irons in the spares box, as guard irons of that sort are not required on a North Eastern tender
5. The fixing screw for the circuit board in the tender needed to be removed, so that the circuit board could move back a little, otherwise it fouled the inside of the tender front bulkhead.

Frankly, compared to scratch building or a major conversion, not a lot of work to do! Of course, I've done nothing to prepare, decorate and detail the bodies yet...

[Paul_sterling]

Hi Folks,

Assuredly, I've not gone into hiding, but I did start a new job a fortnight ago, and that has taken much of my efforts, as well as wrapping up my old job, housework, car work, and cleaning up my old Nuffield Tractor, 1958, and still original paint!

So the latest prints with the horizontal props counter the issue of the tender splaying, the idea is to print, strip the rest of the supports and leave these in place, post cure, and until customers get them, then the shells will have normalised and are unlikely to warp further.

The locos, I've seen a couple have buckled upwards on the running plate around the centre axle. I can't do a vast amount about it, without changing the outward appearance of the locos, other than to cure the shell, with the knife edge sacrificial frame in place. This in itself presents a risk of fracture when I go to remove it, but worth it to keep the loco straight, as deflection here is a pet hate of mine. The rest of my locos have been tank engines, and obviously, having a large box section here goes a long way towards countering the movement of thin running plates, in fact the N9, which is identical underneath to the J21 CAD 9as thats what it was created from) shows no movement whatsoever.I could have put more connections between boiler and running plate, but it would have moved the loco further from the look of the original, its a compromise at the end of the day, as we know, the experts (those that sell locos in red boxes), haven't been able to move flat running plates as of late either........

Paul.

[billbedford]

I had a lot of problems with printed wagons warping, so I cut one in half and found this:

This is a well-known phenomenon with plastic moulding and enclosures have to be designed carefully to avoid warping. It's also why enclosures tend to have rounded edges.

Remedies include:

• Ensuring that all faces have the same thickness
  
  Filleting all the inside corners
  
  Thickening all the faces
  
  And if all else fails, printing the top separately from the side.

The latter is what I've found to work with the wagons. I now print the floors as a separate item.