Shaky or not, excellent work. Your detailing is second to non.

Mark

Yet another masterclass from you Robin super skills.

Al

Great scratch building on the engine superb work regards Phil

Grateful thanks as always to Mark, Alan, Al, May, Phil and Ian! The re-arrangement of my workroom is continuing (slowly), how on earth did I acquire so much rubbish up there? That, along with waiting for an item to arrive to complete the engine (which I couldn't resist) is delaying the completion of this section. Its coming along nicely though and I've been doing some work on the undercarriage of No.2 in between trying to cast a certain part (not the best designed mould apparently!) Anyway, here's a part of the engine...

Hopefully, as you can see from Photo 21, the all in one casting mould did in fact work. I didn’t actually take any photos during the process but I’ve since taken a few to fill in the gaps as you’ll see below. The three examples shown here are ‘rejects’, they have some small details missing or some other defect (one of them has a complete set of air bubbles on the rear of the cylinders) but for this purpose – a trial of different painting techniques, they are perfectly adequate. In the first photo all three have been given a spray of Poundshop grey primer. The top and right hand ones have some missing bolt heads on the hub, the left hand one has a perfect hub but is ‘Backside Bubbles’ as I’m come to call him!
Photo 22 illustrates the basic undercoats applied over the grey primer. As the captions show, the top one was painted with Humbrol Steel Metalcote, the left engine was given a coat of Citadel Mithril Silver acrylic whilst the last one on the right had a coat of Humbrol Matt Black Enamel. Despite being a relatively new tinlet, the Matt Black was so thick it took longer to paint in all the nooks and crannies on No.3 than the other two combined. (The following day I found my Matt Black aerosol tin I was searching for! ) In Photo 23 the next stage or layer was applied. The Metalcote engine was given a polish with cotton buds and a duster cloth, the shine was actually greater than the effect shown here – probably the lighting has toned it down. The black one was given a dusting with Uschi van der Rosten Steel Polishing powder, again applied with cotton buds, this brought it up to look almost the same as the Metal Cote version as you can see here. The Mithril Silver one was given a wash of Citadel Skaven Brown Ink (water-based), this produced the most realistic effect I think but this is mainly due to the fact that the actual engine isn’t a dark steel in appearance, but a lighter aluminium so the two steel treatments were at a disadvantage to begin with. Finally in Photo 24, I’ve given the two steel engines a light dry brushing of the Mithril Silver to bring out the highlights. This made quite a difference to the Metalcote version, increasing the shine and lightening the overall finish. The Uschi powdered engine was also lightened a little and improved around the raised details. After staring at the three for some time I’ve decided to go with the acrylic Mithril and wash technique for two main reasons – firstly and most importantly, it’s the closest in ‘metallic’ tone to the original and secondly, because this method doesn’t require any polishing to bring out the lustre, I can add on the fiddly little rocker arms and push rods before the painting begins, the other two techniques would have meant adding them on after the main body of the engine was painted or polished. Never mind though, I’ve got that Uschi powder lined up for the undercarriage struts down the line!
As for the casting of the entire engine body in resin, that has gone quite well. I began with the usual box of lego bricks with a bed of plasticene into which the made up resin engine was lightly pushed – I’ve learnt a little trick with this stuff now, when I’m ready to make up a mould during the evening, I leave the plasticene block on top of the power supply for the Rotacraft rotary tool. Its always warm to the touch and by the time I need the plasticene the block is all nice and soft and much easier to work with! Photo 25 shows the front part of the silicon mould which is in fact the bottom of the mould. If you compare this with the other half which is illustrated in Photo 26, along with a resin casting, you can see that the other half of the mould is not as deep as the first. By pushing the engine only lightly into the softened plasticene rather than half way, the join line (if any) appears around the back of the cylinders not down the middle. You might also notice that the top half of the mould has a hole down the middle, this is to allow the trapped air to escape during the moulding process. You might also notice that the engine casting is white instead of the buff colour my resin castings have been up till now. This is another of DWR Plastics products – the same kind of epoxy resin but this one has a much longer set or cure time – ten to fifteen minutes instead of the three minutes for the buff coloured one. I thought I’d try this one because some of the moulds require some ‘help’ to spread the resin into the nooks and crannies during the pouring. This mould is one of those but since I bought the new resin I’ve managed to speed up my techniques a bit and I can now get the same results from the old resin as well!
The technique for casting the engine is as follows – mix up the resin with equal weights of Part A and B using a coffee shop wooden stirrer to do the mixing. Pour enough resin into just the central hub of the deep mould and then use the tip of the stirrer to rub all around the ring of bolts – this solves the problem I had earlier of air bubbles in the ring. Fill the rest of the mould up until every cylinder is filled in and poke a blunt cocktail stick into the top of each cylinder, removing any air bubbles in the top details. Drip a little resin into the hub on the other mould and again rub the mixing stick around for the same reason then pour enough resin into that mould to fill in the cylinders too. Then, as quickly as possible, pick up the second mould and place it down securely onto the first, squeeze it slightly to expel any air in the middle and then carefully pour the resin down the air hole in the centre. One more gentle squeeze and then leave the resin to set. This isn’t too bad with the longer setting resin but as you can imagine, you have to move pretty smartly with the three minute one!
Once the casting is set and removed, the first task is to remove the unwanted ‘axle’ from the rear (which was the air escape and is now full of resin) and drill a tiny pilot hole in the centre of the disk. There is a rear section of the engine (which you haven’t seen yet), which will be cast with a 4mm shaft to join it to the main body. To allow for that, the centre of the engine has to have a 4mm diameter hole drilled into the resin. The thing is, in order for the flat ended shaft to fit in properly, the hole has to be flat bottomed too! Not having had an engineering background it took me ages to find out how the heck you get a flat bottomed hole – the answer (as I expect many on here will know instantly) – is an End Mill Cutter. If you’re like me, you’ve never heard of it either! Photo 27 shows that white casting now drilled and milled together with the 4mm drill bit and an End Mill Cutter (though not the one used here I hasten to add!) I bought a 4mm EMC from UK suppliers and then for about two pound more bought an entire set of ten from China (1mm to 10mm) this is the 10mm shown here just for clarity. The end result is far easier to see on the buff coloured casting so in Photo 28 we have the rear face of the earlier Mithril Silvered engine after drilling and milling the shaft.
Finally for this installment, in Photo 29 we have the first stage of that rear section. This is the High Tension pick-up disk which will eventually have an HT lead going to each cylinder’s spark plug. It begins with two plasticard disks of 6mm and 8mm, both punched out of the sheet and glued together with a 4mm diameter hole in the centre. It is illustrated here with the 4mm aluminium tube which will later form the central shaft, and sat on the card template showing the nine cylinder alignments. In the next installment I will carry on with this section whilst hoping an essential part to complete the engine arrives soon. Oh, and I spend an entire evening shaping a piece of copper tube about half an inch long!

Until then, Happy Modelling to you All!

Robin.

The tube at the rear of the engine could be a single tube in early aircraft that exited into the cockpit to draw air into the carburetta to mix it with the fuel, later Le Rhone engines had an additional 'T ' bar added that exited on either side of the fuselage to give an improved air supply. It must also be noted that any throttle control was severely limited in these engines once started they literally run themselves, yes there was the 'Burpe' switch/lever that gave a short power boost but that was it until the German manufacturer noted below enabled a crude engine throttle.

The downfall of the rotary engine was the fuel/air supply as it was an atmospheric supply and not boosted by a turbine to force the air/fuel mixture into the cylinders. Adding another bank of cylinders as was tried and even a third just resulted in a fuel/air starvation because of this. The standard explanation of the demise of the rotary engine usually blamed on the lubricant used in these engines IE 'castor oil' was nothing to do with it just a simple air/fuel supply.

A German engine producer did give a step forward on controlling the torque produced by these engines as follows:- 'The powerplant for the Siemens-schuckert D.111 was a Siemens-Halske Sh III 160 hp, 11-cylinder counter rotary engine. A standard rotary turned cylinders and propeller on a stationary crankshaft, turning in one direction at 1800 rpm, but on the Seimens-Schuckert, the propeller and the cylinders turned at 900 rpm in one direction, while and the crankshaft turned 900 rpm in the opposite direction. This counteracted the torque inherent in the standard rotary and produced a maximum of 210hp.'

The picture's below give examples of the carburetta tubes although this only shows the later 'T' bar configuration the earlyer type just having the carburreta attached to the end of the intake tube.

Incredible work, and a great insight into casting.

Mark

Brilliant work Robin love your scratch building well done so far regards Phil

Always an interesting and information packed update from you Robin lovely work.

Al

Grateful thanks as always to Phil, Tony, Al and Mark! This installment finalises the scratch-built Le Rhone 9C Rotary Engine. As I mention at the end, I can quite understand how much satisfaction Kev gets out of his upgraded racing car engines now. This little one is quite basic compared to his and the miniscule size of the PE add ons Kev is putting in is amazing! To me, real engines are still dirty oily things to be avoided at all costs - but I'll make an exception for this little one!

So carrying on from last week, Photo 42 illustrates the first attempt at creating the mould for the copper intake tubes. As you can see here I’ve added a plastic square rod at each end with the joint filed down to marry up with the ‘flange’ on the copper tubing itself to form a ‘sprue’. The actual mould box in Lego with the base of plasticene is shown in Photo 43. The liquid silicon rubber was poured in to this box and when set, the plasticene was removed, the exposed face of the first silicon block was given three coats of liquid wax mould release and the second half of the mould poured on top. Once set and pulled apart, the lower sprue was extended to the edge of the mould to form an air hole (or bubble release). Unfortunately this design was not a great success, for some reason the two sprues seemed to suck out the resin whilst it was still liquid leaving me with a pair of perfect sprues and either nothing at all in the centre or at best a hollow resin bubble in the shape of the intake (actually about as realistic as you could get but so fragile it just broke up on removal from the mould) . After half a dozen failures I decided to re-make the mould. This time I only used the bottom sprue which was butted up against the Lego box. Again a two part mould with most of the depth of the piece in the first half and a mere ‘impression’ in the second. This one worked well however. Instead of trying to pour the liquid resin down the hole in the mould I simply mixed the resin up and used the mixing stick to dribble some resin into the deeper mould (whilst leaning it on a slight incline to stop the liquid resin running out the end) and also applied a dribble over the impression half as well. I then quickly placed the two halves of the mould together leaving them standing upright. The edge channels I’d cut into the deeper half (filled with silicon on the second half pouring) provided enough of a seal that the rubber mould didn’t require any rubber bands to keep it together as the silicon set. As you can see in Photo 44, the new mould gave almost consistently good results – I used both the standard 3 minute resin and the longer 15 minute type (white castings) and both came out fine so most of the nine intakes were made with the cheaper 3 minute mix! I’d already managed to get three good casts from the first mould before these pics were taken so Photo 45 shows the remaining six during the painting process, previously undercoated with Poundshop grey primer and then painted in acrylic copper. I was going to do the main shaft in Admiralty Copper and the top section in Vallejo Copper but the Admiralty one didn’t come out very well so in the end the whole thing was done with the Vallejo. With the pull rods and rocker arms all fitted, the engine, together with the rear HT disk assembly was given a good coat of Citadel Mithril Silver as shown in Photo 46. The next evening the two components were given the Citadel Skaven Brown ink wash treatment as per the trial version seen earlier. The resultant ‘dirtied’ engine can be seen alongside the little item I couldn’t resist in Photo 47 – a set of amazingly detailed 1/32 scale resin sparkplugs! You’d think in this scale a sparkplug would be a sparkplug, but no! Taurus Models from Poland produce a whole range of ridiculously tiny resin doo-dahs for just about any WW1 aircraft from separate cylinders and those rocker arms through sets of nuts and bolts to these beautiful sparkplugs (which are available in British, German and French designs and also early and late war versions!) Curiously the packaging says twenty pieces although the set here is only ten plugs in total. Photo 48 shows the first two sparkplugs glued on with a drop of super glue, you can also just make out two of those first three copper intakes I made earlier (they’re also visible in the preceding photo too.) During the ‘sparkplugging’ sessions I also made up the HT disk wiring. In one of my reference photos the HT leads were clearly shown wearing some kind of insulation sheaving (probably that cotton or some other material insulation found on early electrical wiring before the advent of pvc (anyone else remember the old black rubber house mains wire?) Anyhow, that EZ Line Rope I bought by mistake wasn’t a total waste after all! In Photo 49 lengths of the EZ Line has been super glued to the HT connectors around the disk and once all the sparkplugs and intakes had been fitted to the cylinders as shown in Photo 50, the shaft through the HT disk was finally glued into the milled hole in the engine hub as shown in Photo 51. In this shot the HT leads are in the process of being glued to the sparkplugs. This was achieved by attaching a miniature metal clip to the end of the EZ Line, adding a tiny blob of Roket Card Glue to the end of the plug and stretching the line over the plug where the weight of the clip keeps the line taut. Another drop of Roket was applied on the tip of the plug and left to dry. The final result of the HT harness is shown in Photo 52 after the excess EZ was snipped off. The completed engine is illustrated in the double Photo 53, attached to the aluminium tube fitted into the engine firewall by a brass rod, this forms both the axle for the engine and the fixing point for the airscrew which follows later.
Well, that’s my very first attempt at a completely scratch built engine – and I can understand now why Kev enjoys making the things so much! There’s something very satisfying in turning out a tiny object, which, at the end of all the work actually looks as if it might start up and run! At least now, if I find the front cowling too difficult to get right I can make a separate cowling, have it laying on the deck and have Dunning’s Pup undergoing engine maintenance!
In the next installment it’s back to Pup No.1 and the undercarriage!

Until then, Happy Modelling to you All!

Robin.

Hi Robin.
fantastic work on the Engines. they look very realistic. enjoying watching this one come together. Ian