Tag Archives: Miss Severn

Hispano-Suiza 8F (Part 8)

I’ve continued to push on with the two Hispano-Suiza engines, but the burgundy coloured one is going in a slightly different direction to the black.

After adding both cylinder banks to it was time to look at the induction manifold.

Previously it had been a single piece casting which worked quite well, especially in pewter. It was very awkward to remove the more delicate cold cast resin part from the mould though. The one installed on the black engine did suffer a little damage that had to be repaired. The arrangement also has no adjustment within it, so getting the cylinders exactly the same height and at 90° to each other becomes critical to a decent fit. I wanted something that was a little more tolerant of minor errors.

The obvious solution was to divide the casting up in to 5 parts, as it is on the real engine.  You quickly appreciate that the original designers must’ve done this to allow for manufacturing tolerances, amongst other reasons.

Hence a revised version was developed in CAD and sent off to be printed.

The revised parts fresh from the 3D print bureau with the print supports still attached.
The parts after a quick clean up. The manifold is symmetrical about the centre, so I only need one side printing to make the mould for both.

The link piece in the centre of the picture above is deliberately slightly over length so that it can be trimmed to a perfect fit on the engine, giving me the slight adjustment I wanted.

The cold cast components. The left hand part has yet to be polished.

The link pieces were glued to the central casting and the outer parts dry assembled on the engine using 1 mm bolts to locate them accurately. Then commenced the trial-fettle-trial sequence making sure I reduced each link piece equally in length. During the process I also filed off the locating pegs on the bases of the side pieces because they were more trouble than they were worth to be honest.

The result is shown below, and a it is definitely better fit than previously, though there’s no actual visual difference between the two arrangements.

The parts can’t be permanently fitted though until the carb has been attached as well as the plugs, ignition leads and their guide tubes in the V.

Speaking of ignition systems brings me on to the main change on this model. The black engine retains the magneto ignition system of the aircraft engine. The full Auto Engine Works marine conversion changed this to a coil/distributor version with dynamo. This makes more sense in a boat where swinging the prop is problematic to say the least, and a starter motor with charging system almost essential.

I wanted to model this arrangement on the burgundy engine, so it was back to CAD to develop…

Once again a set of .STL files were created and emailed to the 3D print bureau and 3 or 4 days later the printed parts arrived in the post.

STL = STereoLithographic which was the process used in the earliest 3D printers. The processes have changed, but the file type has stuck.

The parts with print support structure.
And cleaned up ready to make moulds from.

Moulds were taken and the parts cast in polyurethane resin. The dynamo and front face of the water pump were cold cast because they would have bare ‘metal’ areas I wanted to highlight. Incidentally,  exactly the same resin was used throughout. The only difference is that the cold cast items have 67%, by weight, aluminium powder added. The end housing was also cold cast simply because I had a little mixture left over after the other two, and it seemed a shame to waste it.

The parts cast in resin. The water pump has also been partially assembled in this picture and the bare metal part of the dynamo polished up.

The water pump faceplate came out quite well.

A quick bit of airbrushing later…

The black and silver components were sealed with a satin varnish.

The rest received a coat of burgundy gloss.

Once it had hardened I scraped back the faceplate of the water pump to highlight the company name.

The assembly also included a few photoetch components. The mask for them is shown on the right in the photo below. The large mask is for the exhaust system, including another drill template. I’ll come on to that saga in a future post.

The picture below shows it all assembled and mocked-up in-situ, but no plumbing or wiring has been installed yet. The pipe in the photo below is a trial fit, and I think it needs a smaller diameter one really. A bit inconvenient that, as the lugs are designed to take it. Guess which parts aren’t included in my CAD model…

The distributor assembly on the real engine includes a mechanical means of adjusting the timing advance. To replicate that it was back to CAD again. Then Photoshop to develop more etch masks. I cocked things up slightly on the latter. I forgot to add sprues to them and had to stop the etching process when it was 90% done and the components were still held together. Otherwise they would’ve fallen off the support and disappeared in to the bottom of the etch tank, never to be seen again. 

Two sets of advance and retard mechanism components. The top are fresh from the etch tank. The bottom ones are after clean up.

After the residual flash had been removed the parts were stained and assembled using 0.7 mm brass pins as pivots.

I couldn’t resist mocking the whole thing up again on the rear of the model. It won’t be fitted permanently until I have sorted out the cooling pipe size issue and have installed the spark plugs etc. in the V of the engine, which will be the next job.

The advance and retard mechanism assembled and in place at the rear of the engine.

As an aside: I mentioned last month that I might put some mild weathering on one of the two engines,  but wasn’t sure about the idea. To get an idea of how well it might work I carried out a trial on the scrap gearbox casting left over from when I dropped it.

Pre-weathering
Post weathering trial.

I’m reasonably happy with the result,  but need to include a bit more gloss black in the mix to give a more oily appearance. Other than that I think it’s on.

It’s been decided that the black engine will be the standalone desk curio and the burgundy one will go in the Miss Severn boat model. Based on that it’s the black one which will get the weathering treatment.

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 2)

Well hopes of the next post in this series coming along sooner than the last weren’t realised. It’s been quite a long time since the last post on the Miss Severn build. However, progress has been going on in the background albeit slowly, despite illness and such.

In order to make some progress while I wasn’t at my best I polished up some of the fittings that come with the kit. The improvement in them is quite marked. Hard work without being able to use power tools though.

Having completed the basic hull, the next step was to plank it with the mahogany strip provided in the kit. The operation is pretty standard stuff. the planks were fixed with medium grade (as opposed to thin or thick) super glue. It’s a messy job as the glue seeps through the pores in the mahogany so it is almost impossible to stop it getting on your fingers at some point.

Having completed the bottom of the hull the chine line was redrawn and the planks cut back to it.

Chine line

With the chine line re-established planking of the sides commenced.

When the first few layers had been completed the boat was finally freed from the baseboard. It was at this point that I realised I’d messed up a little.

I’d stuck the doublers LS3 and RS3 on the wrong side of deck. Obviously they should be on the underside of it to allow it to be planked on top. It’s not specified in the instructions, probably because it should be obvious, but not having built many boats before it wasn’t to me. Ho-hum. They weren’t that hard to remove anyway with a chisel.

Having cleaned the deck up it was possible to get on with the assembly of it and the associated hatches. This was all done as per the instructions.

I took the opportunity to coat the inside of the hull with some expoy resin prior to completimg the decking. It was finished in a coat of mid grey paint.

Completed hatches
Hatches installed with spacers to allow for the hinges later.

The decking was completed which in turn allowed the remainder of the side planking to be finished and sanded flush with it.

Looking more like a Gold Cup Racer now.

At this stage I decided to get on with making some of the cockpit internals for a bit of light relief from all of the sanding, which I struggle with.

First up was the gearbox cover.

The wood in the kit wasn’t especially attractive to be honest, and the fixing tabs were very visible, so I decided to cover the entire assembly, and the rest of the cockpit items, with some mahogany veneer I had to hand. The improvement in the appearance between the veneer and kit parts is shown below.

Kit ‘mahogany’ on the right. Mahogany veneer on the left.
Finished gearbox cover with mahogany veneer applied.

The model I’m building has the optional lighting kit included. In order to hide the switch I decided to adapt the gear lever by installing it on a small rotary switch. The switch I opted for was a 24V, 0.5A Lorlin MTL-21-10 part, which I actually got from Farnell (Order code 2797234). The switch is an 8 position rotary one so each throw is 45°.

The whole assembly was then stained and varnished.

Modified gear lever, adapted to switch the lights on and off.

Next up were the seats which went through the same process.

And the cockpit ceilings and sideboards.

The sideboards, as supplied, had some annoying voids in them which thankfully would be hidden by the veneer.
After a bit of staining and varnishing. Oh, and a new cutting mat.

It was onto the seat squabs and backs next. The squabs were quite straight forward. A little bit of sculpting to make them look like they had been sat on in real life and some piping added around the edges, made from 0.5mm solder wire secured with super glue, and they were ready for sealing and painting. The seat backs were a different story.

The kit parts come fully marked up and just require some careful cutting, carving and sculpting to achieve the desired shape. However, sculpting and carving are not my strong suits, and the final results of my efforts did not make the grade. At all.

So I decided to make them again in a different way. I made some half round balsa strips of the right diameter and glued these to a thin piece of plywood backing as shown below. That at least gave me a nice even shape to seat backs which were then coated with resin, which was allowed to pool a little in the valleys so that they became rounded at the bottom.

Patent tooling for the making of half round balsa strip. Take your oversize square piece and hammer it through the nut and splitter to get two half round strips.

The final result was much more even than I could carve.

The instrument panel was my next project. I started with the instruments themselves. You have to cut the ‘glass’ yourself from clear acetate. I cut out some circles as a guide in masking tape using my sharpened compass. Then stuck them to the acetate, chopped off the corners and then sanded it circular.

The kit tells you to fix the pictures of the instrument faces supplied directly to the acetate with super glue. This was not an unqualified success for me as my glue disolved the print.

Luckily I’d already scanned in the pictures in case I needed extra copies. Bitter experience has taught me to always do this. So I was able to remake them. The second time around I mounted the pictures on some white plasticard and glued that into the bezel, behind the clear acetate glass.

The whole project then took a bit of a lurch to the left…

I was mocking up the dashboard to get a feel for how it would look. In particular I was trying to come up with a more in scale switch assembly than the one supplied in the kit. I ended up with a stainless steel pin in a small eyelet which looked OK. You can see it below next to one of the machined switches supplied in the kit.

The one thing that does leap out at you is that the grain on the instrument panel is very out of scale itself.

The real instrument panel in Miss Severn.

I decided to try a few other woods to see which looked best.

Oh, and I ought to warn you at this point that the kit dash has a hole in it which isn’t used and shouldn’t be there. It’s at about 2 O’clock from the steering column hole.

The drawing of the instrument panel vs the pre-cut kit part. The latter had an extra unwanted hole in my kit.

Having made the samples the decision was made to go with the pear option. Then commenced the job of actually buying enough pear to remake all the parts I’d just finished in mahogany!

While quite a few people advertise that they sell pear veneer and structural veneer, I discovered that most seem to only buy it in when someone orders it, and they can get it. It took me quite some time to actually locate some satisfactory supplies. A couple of months in the end.

The gearbox housing remade in pear is shown below next to the original mahogany one below. The improvement in the scale of the grain is obvious.

A lot of work went into the picture below. Honest!

Cockpit components remade in pear wood.
SS316L 2mm stainless steel strip used as capping for the sideboards. The screws are from US Microscrew P/N M06-30-M-SST PAN. They also sell on Amazon. They are M0.6 x 3.

The cockpit floor was also covered with pear veneer. Simulated brass screws were made using 0.8mm brass rod sanded flush, then scored with a knife blade to simulate a slotted head.

The floor was airbrushed with mahogany stain.

Mocked up in the model prior to the airbrushed stain being removed from the brass screwheads with acetone.

After it had dried the stain was removed from the screw heads with acetone on a fine brush. Be careful if you try this. A slight excess of acetone on the brush and it will pool and strip the stain from the wood around the brass too. Go careful.

CAREFULLY removing the stain with acetone.

And here it is again after the stain has been removed.

The next question was what finish to do the cockpit in? I had assumed that it would be gloss, but the satin looked so good. The problem was how to manage the transition from a satin cockpit to the high gloss hull outer. The latter has to be gloss as it is such a key characteristic of these boats.

In order to help make the decision I’ve decided to make a mock up in both satin and gloss just to see how they compare.

Mock-up in satin to determine the best finish in the cockpit.

I’ll let you know how it goes…

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 1)

Having shelved the Chris Craft build for the time being until I can locate some acceptable fittings, or am well enough to make my own, I decided to move on to another boat build.

The model chosen was another 1/8th scale model. This time of a 1922 Gold Cup race boat derived design called Miss Severn. The kit is produced by Mack Products, and mine included the add-on lighting set. As the model will be built for static display, none of the radio control elements  will be fitted.

Continue reading ‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 1)