Monday, November 19, 2018

Wasp Stripes: An Experiment

I hate the idea of wasps. Not only do I not like the variety that sting, but the idea of trying to mask up a locomotive to paint on wasp stripes fills me with dread, especially given the smaller scales I usually model in. One of the K12 diesel locomotives was fitted with extra plating that was painted with wasp stripes and while I wanted to be able to model that I didn't think it was going to be possible to mask the parts for painting on wasp stripes, so as a bit of an experiment I included a stencil on the test etch.

I spent a few minutes (spread over a few hours) this morning trying it out. The steps were easy enough; spray the part with primer, spray with yellow paint, stick the part to the back of the stencil using masking tape, spray with black paint, and finally remove the stencil. In theory there is only about five minutes of modelling there but you need to wait for the paint to dry (enough) at each step. The process was frustrated slightly as the can of yellow paint I had seems to have gone off so it didn't cover very well, but I think this proves that I can paint wasp stripes that are good enough.

I'll admit that it's not perfect (I didn't let the yellow full harden so it's bunched up a little around the rivet detail, and it may need a touch more black) but I'm more than happy with how it looks. Don't forget the picture is many times life size, and to the naked eye it looks spot on.

Sunday, November 11, 2018

Alan Keef K12 Diesel: Part 1

Having built the peat wagon I had a go at assembling the parts on the other etch, which turned into.......

You can probably see in the photo that the etch and 3D printed chassis are just slotted together, but hopefully some of you will recognise the loco as a K12 diesel built by Alan Keef Ltd. While I've managed to assemble all the parts around a KATO Centram chassis, I need to make changes to both the etch and the 3D print; there are a few niggling issues but more importantly I managed to mess up the design of the bonnet side panels by misinterpreting the drawings I was working from.

Even though there are issues with the model I think it looks the part, and I'm really happy with the fact that all the complex folds on the etch worked perfectly. It might be a while before I have more progress to show, so while you wait here's a short video of it circling my tiny test track:

Monday, November 5, 2018

Peat Wagon

This mornings post saw the arrival of test etches for a couple of potential kits.

I've hidden the labels in the photograph so as not to completely give the game away, but it wasn't long before I made a start on a quick test build of the simpler of the two etches.

As you can see the etch builds up in to what I think is a fair representation of a peat wagon. It's based on an example preserved at Amberley (from where I've shamelessly "borrowed" the photo). I've worked solely from the photos on that page, with all measurements based on the fact I know the track is 2ft gauge. The etch sits on a 3D printed chassis, based on the Hudson rugga chassis, to produce a 6.5mm gauge model.

A bit of paint and weathering and I'm really rather happy with how it turned out. Mind you the photo hides the fact that it was awkward to assemble, so there will be a slight redesign of the etch before I build any more or before it becomes a kit.

Tuesday, August 14, 2018

Insulated Driving Wheels: An Experiment

While the build of Ivor might be on hiatus, I now have four wheels which are effectively scrap (given that they are no no longer the same size) on which it is safe to experiment. The final two pieces of the wheel design I needed to finalise were the insulation from the axle and the crank pin.

Let's start with the insulation first. It's difficult to see in the photos but what I've done is to simply take the test axle from a few posts back and fit this to one of the wheels. This involved opening out the axle hole in the wheel to 2.8mm which is a nice tight fit for the insulating bush I took from a pair of hornby disc wheels. I'm not sure this is the final way I'll go (I might try turning my own insulating bushes) but it is nice and straightforward and seems to adequately insulate the wheels from the axle at little effort or expense. Obviously on the real wheel I'd trim the axle back to the face of the wheel.

When I was originally working on the 3D model for the wheels my plan was to use a 14BA screw as the crankpin with a hole through the wheel tapped for 14BA so the screw would actually screw into the wheel. I had wanted to cast a recess into the back of the wheel to seat the cheesehead bolt but the wall thickness requirements meant that wasn't possible. So my plan was to screw the bolt into the wheel and then cut the head flush with the back. A little drop of loctite helping to hold the bolt in place. Unfortunately while I managed to open out the hole big enough to tap, I then broke one of my 14BA taps and stripped the cutting threads from another. With no taps left I opened the hole up slightly further so that the bolt was a tight sliding fit. Rather than holding it in place just with loctite on the body of the bolt I decided to drill a recess for the bolt head anyway as there seemed to be enough material. With that done the bolt sits nicely in the back of the wheel and the bolt head helps to keep the bolt perpendicular to the wheel while also providing more surface area for loctite to hold it in place. Once the loctite had set I did try pushing the crankpin out and couldn't do it by hand. Even with a set of pliers it took a lot of force to break the seal, so this definitely looks like a workable solution.

Friday, August 10, 2018

Ivor is Going on Hiatus

So unfortunately work on Ivor is going on indefinite hiatus.

After doing the maths this morning I thought I'd go ahead and turn the wheels down to 20mm from their original 21mm diameter. If you remember when I originally turned the wheels I said it was hard work to get them down to 21mm, well getting down to 20mm seemed nigh on impossible. I continued to take it very very slowly but the work involved looked like being too much for my lathe without substantial extra work to the wheel (thinning the depth and reducing the width with a normal cutting tool first etc.) but with perseverance I got the first wheel to 20.5mm and so decided to split the difference and stop there. All (reasonably) good so far.

Having let the wheel cool (they get quite hot during profiling) I went to undo the wheel holding fixture only to find it was quite tight. I gently used a pair of pliers to start loosening it (I did this last time when it was too hot to touch) only for the threaded rod to snap in half! This means that the wheel holding fixture is now useless. More to the point I now have one 20.5mm diameter wheel and three 21mm diameter wheels so Ivor is going nowhere anytime soon.

I think the best thing to do is simply put the kit away for a while and focus on something else. This will give me time to rethink the wheels (I'll redo the 3D model for a smaller diameter and to make them easier to profile) and probably to save up to replace the wheel holding fixture. I could continue on with the body, but I think I'd just get frustrated knowing I couldn't fit it to a working chassis (plus it might need modifying to fit the gearbox etc.) so will probably turn to something else entirely. Not sure what yet, but I'll be sure to post when I've done something new.

Determining the Wheel Diameter

I've been having a bit more of a think about the wheels for Ivor after yesterdays discovery that they are probably too big to both fit inside the splashers and next to each other. It's also been pointed out to me that, normally the centre line of the buffer on standard gauge stock sits 3' 6" above rail height, which would be 14mm in 4mm to the foot scale. While Ivor isn't exactly based on a real loco, it would still be useful to have him sit at roughly the right height if I don't want him to look daft against standard 4mm wagon kits etc. The upshot of this is that I've been doing some maths...

The upshot of all that is summarised in the bottom right hand corner. My original 21mm diameter wheels would put the centre line of the buffer at 14.5875mm above rail head, so about 0.6mm (or almost 2" in real life) too high. To get it to sit at exactly 14mm I need the wheels to be 19.825mm in diameter (excluding the flanges).

I think given this bit of maths (and if anyone fancies checking my working it would be most appreciated) that I would be better off reducing the wheels to 20mm (or 5' in real life rather than the suggested 5'3") which would give a total diameter including the flange of 21.27mm which given the wheelbase of 22.5mm should leave a gap of 1.23mm between the flanges of the two wheels.

Does that seem sensible to everyone?

Thursday, August 9, 2018

Is It Just Me?

I'm beginning to wonder if either I'm drawn to kits with design issues, or if I'm just not very good at building kits accurately.

Having finally battled all that was weird and wonderful with the Canopus kit I thought the kit for Ivor the Engine looked quite a bit easier. Okay I made life more complex for myself by deciding to make my own wheels, but in itself that shouldn't affect the design of the kit. Having built up the chassis (fairly easily I may add) I've now made a start on the body, which in turn has led me to discover a couple of, potentially, catastrophic issues.

So far I've formed the splashers and attached them to the footplate, which also includes the front buffer beam. What you can see, in the photo above, is the chassis slotted into the footplate containing one of my wheels on the test axle I turned.

The first problem was that the chassis wouldn't fit into the footplate as it was slightly two long. After a lot of careful filing I've made it fit and the fixing holes appear to line up pretty well. The second problem though is that the chassis wouldn't fit with the wheels attached. In the photos you can see that I've bent the front of the splashers that are inside the model to get the wheel to fit, and it still feels like it's catching when I turn the wheel. I think the solution to this will be to cut away the extra metal, as it can't be seen once the model is assembled, and isn't needed to keep the chassis central once the screws are in place. Before doing that though I wanted to figure out why the wheels didn't fit.

Looking again at the instructions, which are just a sequence of photos with no textual description, I think all the photos show the 7mm version of the kit and not the 4mm version. It's difficult to be sure as most of the photos don't include anything to give a sense of scale, but they all seem to have previously appeared in this RMWeb thread discussing the build of the 7mm kit. The one page that is clearly for 4mm gives the size of the finished model and is the place where it suggests to use Ultrscale OR Markits 5'3" 16 spoke wheels with 8 spokes removed. As I was making my own wheels I took the 5'3" as a starting point and produced 21mm wheels (5.25*4). As I made the wheels to RP25-110 the flange depth is 0.025" or 0.635 giving a total wheel diameter of 22.27mm. The instruction page also states that the wheelbase is 22.50mm which as far as I'm concerned is just a bit too close to 22.27mm for comfort. In fact placing two wheels against the chassis I'm not sure they will fit without the flanges touching!

Reading through the thread on RMWeb I did notice that the suggested wheels in 7mm scale are actually 5'2" diameter not 5'3". I know that would only change their diameter by a small amount (they would be 21.94mm over the flanges) but that extra clearance would probably be great for both the splashers and between the wheels.

I can't be sure that the flanges will touch until I turn up a second axle (I've just the test axle so far) but if they do then I guess I'm going to have to try and reduce them in size slightly which is a real pain, although it might mean I can remove the slight flats on the flange from removing the wheels from the sprue. Mind you that isn't really the point; if I'm following the instructions for a kit am I just picking kits with issues, or am I just not assembling them accurately enough?