Heat Treatment of I/C Cylinders

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Heat Treatment of I/C Cylinders

This topic has 20 replies, 8 voices, and was last updated 18 February 2010 at 23:06 by Ramon Wilson.

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14 February 2010 at 19:00 #2258
Ramon Wilson
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@ramonwilson3
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14 February 2010 at 19:00 #48654
Ramon Wilson
Participant
@ramonwilson3
Hi,

I’ve just begun milling the crankcase on my new I/C project, a scaled up (twice capacity) version of a model aircraft diesel engine of my youth.

Whilst doing so I have been musing on whether or not to harden the cylinder.

I have, under controlled conditions at work, heat treated literaly hundreds of small parts though none were cylindrical – that is ‘tubular’.

Well aware of the distortion that can take place if parts are not quenched carefully I wonder if anyone has experience of this application in a home workshop environment.

I was thinking of using tool steel, specifically B01Arne and tempering well back. I have no means to grind this but suppose I could make a spindle that would allow this op to be done on the lathe though I really don’t want to go down this road because of potential contamination. I was thinking more that I may be able to lap any distortion out providing this could be kept to a minimum.

The other option is carburising but I have little experience of this. I do have plenty of Casenite but am put off by the amount of time under heat this requires for a good depth of hardness and the distortion prospects when this is quenched in clear cold water.

I could of course just use a piece of tough-ish tool steel and leave it unhardened.

Anyone have any thoughts on this – would appreciate it if you have .

Regards – Ramon

PS This got ate once – apologies if it posts twice.
14 February 2010 at 19:25 #48655
Jens Eirik Skogstad 1
Participant
@jenseirikskogstad1
Hi, use high tensile steel, chrome steel or cast iron as sleeve. Not neccesary to harden the cylinder, the high tensile steel are hard enough. If you want to harden the cylinder, then the cylinder need grinding to right size by tool post grinder both outside and inside since the cylinder are oversized by hardening and are not very true after hardening hence tool post grinding are neccesary.

I has builded model engines with cylinder made of annealed drive shaft from front wheel drive car, the steel are hard enough against wearing with piston of cast iron.

Lap the cylinder a bit tapered. To test the cylinder fit are correct: The piston are loose in BDC and tight a bit before TDC, the piston are running easy in the cylinder with oil and running tight in the cylinder without oil.

When the engine are cold, it will keep compression while the engine are starting by operator and will expand to parallel sleeve when the engine are warm. If the cylinder was parallel, it will lose compression soon when the engine are warm and will lost power and can not run more. Also an unuseful engine with parallel cylinder.

Edited By Jens Eirik Skogstad on 14/02/2010 19:32:57

Edited By Jens Eirik Skogstad on 14/02/2010 19:38:58
14 February 2010 at 21:33 #48660
Windy
Participant
@windy30762
Hello Ramon, a slightly different type of 2-stroke piston engine my flash steamer revs to 15000 with no load 10,000 under load.

I use an unhardened cylinder liner of en24t and use a cast iron dykes ring on a cast iron piston.

The wear is minimal after 2 seasons of competitions.

Windy
14 February 2010 at 22:30 #48665
mgj
Participant
@mgj
Certainly with 100 kart engines they ran meehanite cylinders and rings with no hardening. Cast iron will harden and polish with wear of course, but these did wear, but then they were pulling in excess of 18000rpm and deliberately running minimal oil.

As far as heat goes, the cylinder had to be shrink into an ali fin assy, and heated to get it out. What would happen was the perforated area around the crankcase ports would”bend” inwards. Having shrunk the thing back into position having turned it naked to the next piston/ring size, we sent then to a honing wizard near Ringwood. They came back parallel and needed more or less no running in – just as well because they weren’t going to get any!

Some model aero engines are finished tapered, notably the ABC engines, but that’s because of the mass of ali at the top of the piston, and differential expansion compared to the chromed brass liner. It eases running in particularly in non-ringed versions. I believe, without being sure that ringed ABC setups are made parallel The trick might be to heat up a piston an measure its shape hot and see whether you need to hone to a taper or not.

Taper is measured in tenths of a thou by the way!

Edited By meyrick griffith-jones on 14/02/2010 22:31:28
15 February 2010 at 00:05 #48669
Ramon Wilson
Participant
@ramonwilson3
Thank you for your replies, your interest is much appreciated

Can I just say – as I don’t want to mislead anyone – that I have ‘messed’ around with model engines – mainly aircraft, a few marine – since the age of fourteen so am quite conversant with their attributes and make up – within those environments. Having said that I count myself as no expert, just reasonably knowledgeable about the basics.

Over the latter years of this period various ‘bits and pieces’ for many engines have been made – rebores, new pistons, crank bearings, changed the timing etc. mainly for control line aerobatic use and to a minor extent, lower level racing.

Until the Nova engine though I had never made a complete engine so that’s a ”first’ and as this has proved reasonably successful I thought it would be good to continue on the same road.

The engine is based on the 2.46 cc ED Racer, but ‘scaled’ to 5cc capacity and whilst there is no intention to get the absolute maximum revs and power out of it, I would hopefully expect that it will turn say a 9 x 6 prop around the 10,000 mark. It certainly won’t be used ‘in anger’ so to speak so given that it will only get the occasional run I can see from your advice that there will be little point in going down the heat treatment route. I was looking at this possiblity purely as an ‘extension’ to the building process.

Jens advice on using high tensile steel and Windy’s confirmation of it’s durability under competition use is recommendation enough and that is what I shall use in conjunction with a cast iron piston. Somewhere in the depths of my metal box there are two lengths of very high tensile steel, turned from foot long studs, ‘surplus to requirements’ from offshore days. After near half a lifetime under the bench I guess it’s time to actually use some of it!

I believe the taper In ABC engines is there to allow the piston and liner to reach optimum fit at the top end when running, the brass liner expanding more than the aluminium piston. One reason why ABC engines should never be run-in in the same manner as lapped pistons in a cast iron or steel bore ie slow rich runs- much better for these to be of short duration but high reving – taking care not to let the engine overheat. To my knowledge I don’t think ABC (model) engines are fitted with rings – may be wrong but never heard of it in the sizes I’m used to.

Thanks again for your input, I would still like to hear from anyone who may have heat treated a liner, but for this build, I shall certainly be following the advice offered

Regards – Ramon

PS Jens, What is the engine in your avatar please?

Edited By Ramon Wilson on 15/02/2010 00:10:05

Edited By Ramon Wilson on 15/02/2010 00:12:27
15 February 2010 at 10:48 #48679
jomac
Participant
@jomac
Hi, just a few thoughts I might pass on. First why not use a chrome/moly cylinder and a cast iron piston, unhardened, apparentley the expansion rate is minimal, so the piston should not jam up,also wear is acceptable, anything over 5cc you could use an aluminium piston and make your own cast iron rings, (modelenginenews has lots of articles and info on this subject), in all cases the piston fit is very important, so lapping carefuly is a must.

See Dave Fenner’s articles on building the Sugden special in last years MEW and the problems he had with piston fitting and lapping, Geometer and modelenginenews, has lots of info on this subject.

I am in middle of making the Boll-aero 18, useing crome/moly cylinder and cast iron piston, The chrome 22mm rod I got out of scrap bin at the metal suppliers and the cast iron????? I will cut off an old V8 oil pump. If the oil pump is cast iron thats good !!!!! (I will still use it even if it’s not) because some of the holes through the pump are up to 100mm long with diameters varying from 1/2″ to 5/8″, these were ground for a good fit of the shafts,(make good cylinders), Jens said he uses front wheel drive shafts, a cheaper alternative is rear half shafts, especially trucks, these are some times much thicker, E.Westbury and L.E. Sparey used these for making collets, but they were heat treated before and after, I think with modern cutting tools, machening these as is, should not be a problem.

Its been 3 months since I finished the crankcase out of Al and main shaft out of a high tensile bolt (old engine) and nearly completed the cylinder, but it got hot down here, up to 40 degrees C in the shade, but much hotter inside the 2 car garage, so I have been insulating the walls and roof of my large metal built workshop, I am about to start finishing this engine, let you know how ends up. Sorry for rabbiting on, I hope this topic is a help.

John Holloway.
15 February 2010 at 20:13 #48700
Jens Eirik Skogstad 1
Participant
@jenseirikskogstad1
Posted by Ramon Wilson on 15/02/2010 00:05:54:

PS Jens, What is the engine in your avatar please?

The engine are an “Alpha” 0,5 cc diesel engine. This engine has piston made of cast iron from brake disc and the cylinder are made of torsion spring rod from rear suspension in Peugeot 405. The torsion spring rod was annealed before i machined the sleeve and never been hardened after the cylinder was ready to use. The engine has still good compression.

Some are changed in the engine, the crankcase are whole machined of aluminium with bronze bearing (not in two parts of crankcase and front house who are locktided to crankcase). The crankcase are sandblasted to make tooling marks unvisible. The wristpin are not pressed into the piston, also the wrist pin are prevented to fall out of piston when i drilled the two holes for transfer port and induction port instead the whole rectangle milled ports as in the drawning of “Alpha” by Richard Gordon. Crankshaft are of torsion spring steel.

I maked the engine with a worned and unprecision (much play) lathe Myford ML10, important: my hands are made to make a precision works with lapping tools and sandpaper to make surface nice.

Edited By Jens Eirik Skogstad on 15/02/2010 20:19:57
15 February 2010 at 21:02 #48703
mgj
Participant
@mgj
Run in one or two ABC motors over the years myself Ramon.

A lot of small ringed 2 strokes use chromed bores of various types – often directly on the ali of the fin casting. Its a matt chrome, electrically flash deposited rather like an old flashbulb, and the setup lasts well, with particularly good heat transfer properties.

What sort of piston velocities are you working to? Without doing any sums, it seemed that, on the face of it, with a relatively vintage design and low stresses, that HT steel for liners seems a bit like overkill, especially as you are not planning it run it to death. Unless you just want to?

I always thought that the benefit of HT steel was mainly strength under very high sidethrusts, (particularly in big diesels? ) and as wet liners commonly? Even then iron remains a very popular choice, even in some long and unsupported liners because of its very low friction, once run in and glazed.
15 February 2010 at 21:48 #48705
Ramon Wilson
Participant
@ramonwilson3
Thanks Jens, literally sat down to post and yours listed up.

The Alpha turns out to be much smaller than it looks – is this your interpretation of Richard Gordons ‘Alpha’ so to have a ‘vintage look? If so you have captured it very well indeed.

All input so far points clearly to success with high tensile steel for the liner so that is what I shall use – probably the stud material as already said. I have no idea what specification this was but as it was oilfield equipment I would guess it’s fairly high one.

As I recall though it was very tough to machine the threads down to the root diameter but that was in my early days as a novice model engineer. Anyway I have dug it out and will see what it machines like before I make a final decision. I do have ‘one or two’ bits of tough tool steels to choose from as well as some nice ‘continuous cast’ cast iron lumps to make pistons from. All scrounged and squirrelled away for that ‘rainy’ day!! I guess one day I really will miss going to work!

I have made a quite few pistons in the past and lapped and fitted them to the cylinders of worn engines. I don’t know if anyone else has done this but a cast iron piston can be made to ‘grow’ if heated to a ‘cherry red’ and left to cool. Several well worn diesels and glows have been reclaimed this way, the average model aircraft engine piston growing about a thou/thou and a half depending on diameter. More than enough to re-size using an external lap and then lapping to fit the bore. it dosn’t seem to affect the properties of the iron and the engines done like this appear to last just as before. Unfortunately though you can only do this just the once, so if you over do the lapping it its ‘make a new piston’ time!

John I can only sympathise with your plight as I simply cannot begin to imagine what trying to endure 40 degrees on a daily basis must be like let alone try to enjoy some time in the workshop. I hope you solve your shade problems and get back in there as soon as you are able. Tomorrow when my feet are a bit cold ishall remind myself that it could be a lot worse!.

The milling progresses on the crankcases – more a bit later – if they turn out okay that is!

Thanks again, regards – Ramon

Edited By Ramon Wilson on 15/02/2010 22:15:43
16 February 2010 at 16:37 #48719
Mike
Participant
@mike89748
I am just starting on an IC project (my first) and had considered making the liner out of as-supplied silver steel, with a cast iron piston. Any thoughts from the experts on that?

Also, does anyone have experience of using the small internal hones which are sold for restoring worn hydraulic brake cylinders on cars? Would they give a satisfactory internal finish to the liner?

Any advice will be much welcomed.
16 February 2010 at 17:09 #48720
Ramon Wilson
Participant
@ramonwilson3
Hi Mike,

Welcome to the (first) I/C build club.

First thing I guess to ask is what kind of engine are you building and it’s capacity and secondly what you intend to do with it once it’s finished – that is how much are you likely to run it and in what fashion?

Silver steel in it’s ‘raw’ state can be a ‘bitty’ material to machine particularly if your liner needs a thread cut on it but of course for most people it’s the most readily available and accesible form of tool steel. Wear wise depends on the running ahead but with a cast iron piston it should make a reasonable combination.

As you can see from the previous posts the opinion is to leave it unhardened.

Regarding the internal hones I have used these to great effect but they will not true an out of round or tapered bore – for that you will need to lap it. Again it depends on the initial machining how good a bore is but I would always lap it after machining before using the hone to ‘break the surface’ and apply those microscopic scratches that honing gives if it needs it. For a really good piston/liner fit then lapping the piston is also essential finally lapping it to the bore itself. The two stone variety are no where as effective as the three stone hones for trueness so that in itself limits their use depending on engine bore size my three stone goes down to 3/4″ – I don’t know of any others (3 stone) that go smaller.

I have had good success with just lapping over the years so If you need any further info just shout.

Hope this helps – Ramon
16 February 2010 at 22:07 #48735
mgj
Participant
@mgj
If I may deliberately keep this unpersonal?

If you look at the vast majority of automotive, aero engines, small 2 strokes, racing engines etc of the last years, almost all have liners made of iron and for very good reasons. Surely, more recently, flash deposition techniques have become reliable, and contribute greatly to reductions in cost, but even so, vast numbers of liners continue to be made in iron.

Not any iron of course, but close grained cast iron commonly known as Meehanite – freely purchasable in stick form buy us modellers. (LSM – no connection)

Now why is this stuff so good?

1. It’s cheap and easily available.

2. It’s soft in its basic state, so its very easy to machine.

3. Thermally it is very stable. That’s not to say it won’t go walkabout, but having been thermally cycled a few times it stops moving unless greatly abused. So, having been run/worn in, it stays runned in.

4. As made it is soft – as stated above, which means it beds in very easily, and without taking half the piston with it.

Then- oh lovely stuff, it performs a very useful little trick. The soft iron wears away leaving a very fine polished surface of iron carbide. Now iron carbide is the stuff that abrades our HSS tools, so that surface layer is bloody hard. Harder than HSS.

5. So in its glazed state it is about as anti wear as you can get.

It gets better though – because the carbides in any cast iron are in effect nodules separated by iron . So the surface is open grained, and that makes it:

6 Very good at keeping a film of oil in place.

AND –

it happens its thermal expansion can be matched to that of certain grades of aluminium. Not the bar of drawn HE30 that everyone seems to like making pistons out of – God knows why, but proper matt grey piston ali from an old diesel or car engine.

Its a touch lumpy to machine, but its modified with … with ummmmmm (memory????) silica (don’t quote me), and that alters the coefficient of expansion which gives you a nice light piston (light reciprocating parts – GOOD THING in an engine) with the right thermal expansion to allow a close and consistent fit to prevent rock/tilt

Now almost no other material does all that – So dear old iron, unexotic as it is, is probably the BEST choice for a liner before you go to some of the clever vacuum/inert gas flash deposited surfaces, which do perhaps have excellent wear qualities and, because of the lack of a change in medium, a very good thermal transfer. But that’s not the kind of technology available to us as modellers – and it has taken even the professionals many years to get the surfaces to stick really well.

Having said that iron is (amongst) the best because of its wear, rapid bedding in, age hardening and open grain properties, it has to be said that steels are amongst the worst because they just don’t have that combination of properties or the right metalurgical structure.

Thats not to say that you can’t get an engine with a liner of other materials to work, but its just going about it the hard way. Hell even these people with very long unsupported liners will often either cast in support, or spin iron onto a substrate or backing, just to get those lovely wearing and lubrication qualities in contact with the piston.

So all those thinking of using something amazing – you may be right, but it would probably be best to take the hint and not re-invent the wheel.

So what do I think of making a liner of silver steel – not much. Sorry,

————-

Hones – yes absolute MUST. Nothing to do with dimension – its about creating a fine scratched (OK nearly polished) oil retaining surface. You don’t want it shiny – you want it covered in very fine cross scratches. Most important.

Edited By meyrick griffith-jones on 16/02/2010 22:12:33

Edited By meyrick griffith-jones on 16/02/2010 22:17:09
16 February 2010 at 23:59 #48742
Ramon Wilson
Participant
@ramonwilson3
Nice post Merrick,

I had just written to your previous one and yes once again the blessed thing timed out and despite having saved it I ‘moved’ to get a pic and lost the bl—dy lot – again !!!! God that is tiresome – and now you’ve upped the ante.

Cast iron – you paint a very good picture – you are obviously much more technically aware of these matters than myself -my fall down I guess – I’m much more a practical person. I suppose it would be fair to say my interests lay more with the actual ‘doing’ – the machining processes themselves (and the results) than perhaps any specific subject.

My closing line in my lost post was to say that there may be two (of the current project) and that I would fit one with a cast liner. (I’m doing two crank cases – if there’s a booboo I won’t have to go all the way back to the start again!)

One has to agree, that making a liner from iron would probably be a lot easier machining wise than a toughish piece of tool steel but it begs the question why have so many gone the other route – I don’t recall any model aero engine (I assume we are not straying outside of this area at the moment) with a cast liner and piston though looking back to some early diesels I grant you that’s possible – all the ringed engines I have had however, have been fitted with a steel liner – normally hardened and ground of course. Perhaps because of this – I don’t think its a matter of trying to re-invent the wheel – that for most, without being able to carry out cylindrical grinding, that tough steel is generally considered as the next best option.

I’m not disputing your description of the glazing/skin hardness properties but what kind of wear is involved before this becomes ‘serviceable’ – with a cast piston enough to lose the original lapped fit possibly? I don’t know? Small diesels need very good piston/liner seals to start easily and function well so that soft iron/iron could- may– be detrimental to that end. I appreciate the ‘cast rings in a cast liner’ situation but the compression and piston seal required for such engines is much less than for a small diesel

There’s only one way to find out – you pays yer money etc – but I shall hedge my bets and make one of each and see how they stand up to each other. I think it will all come down to the lapping – we shall see.

Ramon

Edited By Ramon Wilson on 16/02/2010 23:59:36
17 February 2010 at 11:09 #48752
Les Jones 1
Participant
@lesjones1
Hi Ramon and Meyrick,

If my memory is correct when I was in my teens I had an ED Hornet engine (1.5 cc I think) I swapped this for an ED Bee (1 cc) I think this had a cast iron cylinder liner. As this engine was worn my father made a new cylinder for it. This was made out of cast iron. The mention of the ED racer earlier in this topic made me remember this. There was also a mention on this forum of “Keil Kraft” model aircraft kits. I used to build these when I was in my teens. I’m glad I’m not the only one that finds that they have been logged out while typing a reply. I am convinced the time out time is shorter while typing a message than when doing nothing. I sometimes resort to copying the reply I have typed to notepad before clicking on the post button.

Les
17 February 2010 at 11:55 #48754
jomac
Participant
@jomac
Les, Hi, go to the modelenginenews site, note, there is no spacing between the words. There is a full description of all the ED engines, that is quite detailed, on construction , history, and re-assembly, Iv’e just had a quick look, not the indepth articles even so its comprehensive.

Ramon, Hi, its a bit cooler after the record rains we have had in the SE of OZ. Now that Iv’e cleaned most of the junk and rubbish out I can start making swarf.

Anyway I seem to have read articles by E Westbury and others on the use of various metal combinations, for IC engines, I also think MEN has similar articles, This site, especial if you are a member is absolutley massive, you can read for a week solid and still see everthing that is written and photographed.

The article on making contra pistons, that fit and work straight of the lathe is an eyeopener, I think that it also refers to cast iron and steel as a contra piston and what the ramifications are.

PS I dont have problems on timeing/logging out (yet !!!!!). thats brobably because I use OPERA as a browser and mail recipient, its also the fastest browser around, I can read, write, make coffey, read links, check spelling and go back to Windows explorer to do other checks. Maybe Im’e just lucky so far.

John Holloway.
17 February 2010 at 13:00 #48757
chris stephens
Participant
@chrisstephens63393
Hi Les,

Re your logging on/off when you log in click the small square that says something like “remember me” , since doing this I have not noticed being “timed out”! I don’t have to log in when I open ME site, either. It is because of this I don’t get the message about “remember me” so I can’t give exact wording.

Hope this helps you and any others.

chriStephens
17 February 2010 at 13:54 #48758
Ramon Wilson
Participant
@ramonwilson3
Hi all, the timing out only seems to be if too much time is taken writing a post. Last night after writing I scrolled up, checked I was still logged in (yes) (this was the frustrating bit) and opened a file to copy a pic – opened ‘insert image’ and got ‘you need to be logged in to use this function’ Back up to log in and of course the text previously duly copied had been replacd by said pic – Aaaaggghhhhh!

So in future it’s copy text first, log out (to be sure) login again – paste text and then get pic. Well that’s the theory any way.!

Les, as I recall certainly the early Bee had a propensity to lose it’s seal fairly quickly – only a thought, based on what Merrick is saying, and thoughts on possibly losing that fit through the wearing process but could this have been why. Others – Mills actually advertised the fact – used hardened and ground cylinders. If cast is an acceptable alternative to steel it does raise the question why they would go to such lengths on a production basis. I guess we may hear more on this one.

KeilKraft hmmmm! Love ’em – My first kit too at age 11 – totally the wrong thing – Sopwith Camel- didn’t even fly like a brick but it set me out on a modelling adventure that has lasted a lifetime. Great memories.

Had a good morning in the workshop but the sun is finally shining – oh dear – that means garden – I sense a degree of conflict on the horizon

Regards for now – Ramon

Hi John glad to hear you’ve cooled down a bit, I have ‘found’ the ModelEngineNews site – early December and it is exactly as you say – spent far too much, but very enjoyable, time going through it’s seemingly endless pages.
17 February 2010 at 18:25 #48764
mgj
Participant
@mgj
My first engine was a DC Super Merlin. (KK Phantom Mite?)The EDs were a bit deluxe. But I always loved Super Tigres and I always used them once I went RC. Starting with a G21/29, various G21/40s, and finally the recent ABC 40s and 51s. And the best plane of them all – a Loaded Dice with a G90 and Purple Pipe.

Steel or iron in small engines. Here my specific knowledge runs out because my experience is with ringed engines and slightly bigger than model aero engines. My guess would be production and tooling costs rather than practical metallurgical advantage. (At production rates, tooling doesn’t last long in cast. ) The purchaser is left to pick up the problems of slow running in, and most of us have experienced the pitfalls of being over enthusiastic with the mixture needle early in an engines life!!! OTJ training in deadsticks.

Whats for sure is that its pretty difficult to go wrong with iron. (meehanite)

How long does it take for glaze to form – not long, the running in process really. Make it fine, lap it in as close as possible keep a nice matt surface to retain oil and run in carefully with a high grade oil. It’s the thermal cycling that generates the glaze and the final shape. Without better knowledge That is the way I’d go, and I’m sure that Ramon has it right there, but I wouldn’t trouble with a steel liner. I’m sure I’d do better with iron – unless there is some very esoteric reason lurking unseen round the corner.

Pistons – several have talked of using iron for pistons. Of course if you are restoring an engine. But if one is making a new one then for any sort of performance its very important to keep the reciprocating mass down so ali is the way to go if possible. Otherwise you are using power to push this heavy weight up and down, more to sustain the vibration it generates, and more to turn the balance weights required to cancel the vibration out. (and keep the prop light too!!) Racing engines for example often use an ali flywheel, with a steel insert for the clutch face. That allows much more rapid acceleration to reduce inertia in the reciprocating/rotating train. Not very good at idle of course, and very difficult to get the car moving without stalling, but excellent for performance. .

Edited By meyrick griffith-jones on 17/02/2010 18:46:09
17 February 2010 at 20:26 #48766
mgj
Participant
@mgj
Ramon – sorry, I should have said about the glazed finish – you shouldn’t lose dimension in any practical sense. It is literally just the top layer once the bumps have got worn off. And of course one is talking at the crystalline level.So the bumps are pretty small.

Are we talking of a a tenth of a thou? Its tiny, especially if you get a reasonably good finish to start with. Good being smooth as in CLA rather than shiny as such.

Edited By meyrick griffith-jones on 17/02/2010 20:27:53
18 February 2010 at 23:06 #48808
Ramon Wilson
Participant
@ramonwilson3
Meyrick, just noticed my error For someone who can get (mildly) irritated by a Y or D being added to my name I’m a little annoyed with myself! My apologies for spelling yours wrong in previous posts.

Had a look on the MEN site regarding materials for piston and liners. I think it would be fair to say that as far as cast/cast and cast /steel goes there seems to be two schools of thought fairly equally divided. There is a reference to Westbury recommending carburising cast liners though it doesn’t say for which engines – whether this was his normal recommendation for all his engines I have no idea. I have a couple of his articles so will check them out.

Thinking about the production side a bit more possibly the non of use of cast was down to it’s fragility in thin sections in machining – particulary when cutting the ports ??

The cases grow slowly- lots of rotary milling today but, still on course for two (so far!!)

It will be interesting to compare both types of liner both in the machining and in the running – will take plenty of pics and keep it posted!

At this stage though I will keep to cast iron for the pistons, outside of ABC set ups for the size concerned many are made from this material – Perhaps ali on the next one? chromed bore and all

‘Super Merlin’ – Funnily enough just done a bore on one for a friend – and you began with R-C I see – Real Control that is – “fly by wire” – and my constant ‘achilles heel’ over the years. Never really was attracted to R/C power apart from the odd assisted free-flight but did fly a lot of glider for five or six years.

Engines – well I suppose you could say I have had quite a few!!!!!. Like yourself Super Tigres figure highly along with OS – particulary the 35S. The most consistant running engine ever was a ST40(S?) – blue ‘dished’ cylinder head. Unfortunately it wasn’t really suited to the demands of the aerobatic (C/L) mode of flying but it was a lovely engine. A few years back I rebuilt a ST-21/46 bought for 12 quid at a swap meet. It was in a really sorry state but had sound internals. After a fair bit of work however it proved to be the best aerobatic motor I have used. Haven’t flown it since 2006 though – it still resides in the Thunderbird hanging in the garage!

Snow forecast for tomorrow, I shall think of ‘Jomac’ and get an early start ‘a fettlin’

Regards – Ramon
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