Jason’s Firefly .46 Build

[Glenn RoydsParticipant @glennroyds12911]

Well Done Jason a top job, Alex will be over the moon with another baby.

Many thanks for taking the time to post the excellent photographs and informative build.

The finish of you engine is very impressive it just looks like it dropped off the production line.

I think all the Firefly's made take a bit of running in as its a plain bearing engine so they run a bit tight (hot) at first, also Alex also swears by quite high percentage of nitro in his to get the performance.

I know Alex has other engines in the pipeline very soon.

Cheers

Glenn

[Ramon WilsonParticipant @ramonwilson3]

Hi Jason, Yes my thoughts exactly. Very nice coverage of the build and an excellent result.

Great to see it running, what prop are you using there and any idea of initial rpms on it?

Haven't been up to much lately so only just caught up – it's good to see another engine finished even if it isn't a diesel

Well done indeed

Regards – Ramon

[JasonBModerator @jasonb]

Thanks Ramon, The suggested prop is an 11×6 or 11×7 but I went for a 10×7. Not really sure of RPM and don't have a means of testing. May have a look to see if I can find a cheap tacho on the web.

It did not seem to scream as much as the 0.20 size buggy engines I used to play with, don't know if thats the prop loading, restrictive exhaust or the fuel which must be a bit duff after 20yrs storage – the fumes certainly did not sting my eyes like I seem to remember so maybe the 5% nitro is long gone.

Now who's going to be first to make an opposed twin version

J

[Sub MandrelParticipant @submandrel]

Ramon, Jason – While you are paying attention, a question!

My shunter is essentially complete so looking fo another cheap project.

I have a basket-case half complete Seal*, but would like to cut my teeth on a smaller engine first.

I have delved into the scrap bin and found a length of 1" (bare) cast iron and I have plenty of 1 1/2" EN1A – Ramon suggests this is a good combination.

I have been tepmted by Nova, but it's a 2-stroke and lacking any lumps of ally, and having various 'interesting' bits of old vice etc. that would make a good base for an open-frame horizontal engine does a low revving over-square four-stroke of about 7/8" bore and 1" stroke sound feasible as a beginner (to IC engines) project?

Neil

*The original maker appears to have given up after making crank and cam shafts and most opther big parts on realising their over-size con-rods wouldn't allow teh ccrankshaft to turn in the machined from solid crankcase.

[JasonBModerator @jasonb]

Yes the iron and EN1A should be fine, infact this engine could probably be done with an EN1A liner if its not going to be flown, spend some time getting a good bore and lap the piston to it. Think I would up the stroke a little bit though.

J

[Ramon WilsonParticipant @ramonwilson3]

Hi Jason,

I would say the 7" pitch is a bit coarse for initial bench run's – it's always better to lightly load an engine – 4 or 5" pitch – keeping the revs up on a rich-ish mixture (for the cast in steel piston liner set up) but not allowing the head to get too hot – just about bearable with the bare fingers.

I've never used 'twenty year old fuel' but have used quite old stock for running in purposes. I have no idea whether the nitro would leach out but usually, if kept well stoppered it's okay. Sometimes the castor will precipitate into small white 'floaty' bits – not sure what causes this but it can play havoc with fuel settings and is best ditched. Methanol will absorb water too and that will affect performance but thats only really noticeable when you are looking for really consistent runs – eg in competition.

I recently bought a very cheap tacho off ebay – paid around a fiver including postage from Hong Kong and it appears to work okay though how accurate it is I have no idea. It was reasonably accurate to my bench drill at 4200 rpm and of course does give a good comparison prop to prop though. Only drawback is it reads both blades so the readings have to be divided.

Neil, it's only since doing the Eta engines that I have become aware that cast iron running in a leaded steel – En1a – liner is a very beneficial combination for piston and liner. Not wishing to contradict Jason but apparently many commercial engines have used this combination and obviously these are aimed directly at the flying model. I say apparently because the more I read on this the more this fact materialises

I know I go on about him but the writer of the article I found – George Aldrich – was a highly respected engineer who had much to do with engines used in world class control line speed events over many years. He wrote many articles on engines in the American model press and specialised in the piston/liner set up, indeed he later made a living from setting up engines for people world wide both for speed and control line aerobatic events. It the article he recommends the 'CIS' system – Cast In (leaded)Steel – as the better way to go up to a 1" bore, after which the weight of the piston becomes too much. For me it was all the confirmation needed to be sure it was the right way to go. Although written some time back I would say it still stands outside of access to some pretty esoteric kit and materials so I certainly see no reason now to step outside of using these two materials for any future 'home made' engines.

Good luck with your project whatever form it takes – don't forget the pics

Regards – Ramon

[JasonBModerator @jasonb]

Ramon the only other prop I have is a 9×6, would the smaller dia go some way to compensate for the 6" pitch?

I'll bow to your superior knowledge on the liner for flying and will have a look on the bay for a tacho.

Jason

PS see you got POM again

[Ramon WilsonParticipant @ramonwilson3]

Hi Jason – personally I wouldn't run a 46 on a 9 x 6 to begin with. It's not a high performance engine after all and at this stage your piston/liner set up is not run in (nor indeed the bottom end) and would benefit from being lightly loaded. A 12 x 4 or a 11 x 4 and preferably wood as opposed to the heavier glass filled nylon type would be a much better option though the latter will do.

I have no experience of using 46 sized engines in the more conventional R/C guise so have no idea of what size of prop would be used for general flying. For control line (aerobatics) however this would range around the 11 to 12" diameter and 5 or 6" pitch. On the bench there's only the prop-wash to keep things cool unlike in the air.

When I began with these things so many years ago it was the norm to fit a relatively large (diameter) prop and run them slobberingly rich to run them in. It was much later that the method of lighter loads, run fairly fast on a slightly rich setting, and, most importantly, not allowing things to get hot became the accepted method. Short runs of 2-3mins gradually increasing the duration but allowing the engine to cool between runs is preferable too. As the running in progresses the needle setting can be slowly decreased letting the revs increase gradually run to run.

What's POM?

Regards Ramon

[JasonBModerator @jasonb]

Project of the month over on HMEM, its not on the header but here

I'll order in a larger prop though as It smore the making and just proving it will run that I get the enjoyment out of, it will spend the rest of its life on the shelf its not that critical to have it run in for that

J

[Ramon WilsonParticipant @ramonwilson3]

I see. I haven't been on there for a couple of weeks now – since the engines were finished in fact – I'll respond a bit later

I know exactly what you mean there, mine live in boxes not seeing light of day until the opportunity to run them brings them out. I was going to the Old Warden do this weekend gone with the intention of giving them all a good run but not feeling too good decided against it – next for me will probably be the Forncett ME day in October but as you say it is the making that's the important bit after all

I'm having a break from machining at the moment but have another nice engine to scale – the Taifun Orkan – later in the year.

Are you going to the Midlands show? All being well I shall be there on the Wednesday.

Regards – Ramon

 

PS I see the dreaded post under the adverts is up to it's old tricks again – what a pain

Edited By Ramon Wilson on 01/08/2012 08:49:13

[JasonBModerator @jasonb]

If I get the Half scale domestic done in time then I may drop it off to its owner there but not sure yet.

I'll have a google for that engine sounds a bit exotic.

J

[Allan Roberts 1Participant @allanroberts1]

Hi jason

I have jt finished my Firefly and it started first go.

I will run it in and let you know what RPM I can get out of it on a 10/6 prop.

Regards

Allan

[JasonBModerator @jasonb]

Well I bought one of these from e-bay and fired up the engine yesterday, still with the 10×7 prop.

Result was 7,100rpm which I was quite happy with considering teh fuel and its still a new engine

Jason

PS Ramon if you are looking in, there is a diesel version on you tube that is basically the same engine with a contra piston and screw so come on lets see a Firefly 0.92

**LINK**

[Allan Roberts 1Participant @allanroberts1]

Hi Jason

I have my Firefly running now with a home made muffler and it is running at 9,500 after about 30 minutes.

Tried to attach some picture with no luck.

Regards

• Allan

[JasonBModerator @jasonb]

Well I just saw a note on Model Engine News that 60 sets of materials have been sold for this engine, yet only a hand full of builders have put their heads above parapet and I've only seen pictures of one other being built in Singapore.

So how about a thread with your builds in it?

Jason

PS David can you confirm if Alan is giving any talks and if so what days?

[David Clark 13Participant @davidclark13]

Alex is giving talks and will be on the SMEE stand.

Don't know who alan is.

regards David

[David Clark 13Participant @davidclark13]

Hi There

I have forwarded 20 requests for the Firefly material pack.

John is running out of material so it will be a while before any more packs will be available depending on demand.

regards David

[WolfieParticipant @wolfie]

Excellent tutorial. Cheers

[Nick Prescott 1Participant @nickprescott1]

Jason, hope you don't mind, but I've printed your advice and pictures off as a sort of 'how to do it' to help me making this, my first engine (my workshop and computer are a long way apart!) Your clear pictures and helpful explanation have inspired me to make a start and I have flycut the body and bored the crankcase front and back – doesn't sound a lot to someone with lots of experience, but it's all a new learning curve for me and your notes have given me the confidence to make a start. Many thanks for taking the time to record your efforts and experiences for those of us with little or no experience.

Just hope I don't make too many mistakes I can't dig myself out of – if it runs that would be a bonus too!!

Thanks again, Nick

[JasonBModerator @jasonb]

Good to know it was of use, just ask if you have any queries.

J

[mechman48Participant @mechman48]

Jason

Fantastic build. As an aside can you, or other members, tell / clarify how you set out a thread as you have, with paragraphs & pics interspersed with decriptions in between. I am assuming that you are writing text then inserting photo from album via the camera icon in the reply box, I'll give it a try with this post & see if it pans out.

Rear toolpost project fitted & given a trial run.

[mechman48Participant @mechman48]

Well, Well! seems as though I have answered my own question, seems the old grey matter hasn't given up the logical process just yet then .

Cheers

George

[geoff walker 1Participant @geoffwalker1]

Hi All

This engine looks interesting and a superb set of photos and build details from Jason, well done sir!

I notice that the cylinder head with it's integral cooling fins sits on top of the the cylinder liner.

Hope this is not a dumb question but does that still provide efficient cooling for the engine?

I've seen engines where the head and fins are separate, the fins are lower down and wrapped around the upper half of the liner which to me would seem to give more efficient cooling of the engine. Is this just for larger engines generating more power and heat?

Just curious guys that's all, I quite like this engine, bought the 2012 rcm and e with the free plan so am very tempted to have a go and make one. I'll give it a lot more thought and research before I do!!!

cheers geoff

[JasonBModerator @jasonb]

Geoff, the cooling fins were just a bit of "tarting up" on my part. Alex's original design just had a solid top to the head and fewer but thicker fins around the perimeter and that seems to work OK actually flying in his planes.

It is said that most of the heat is generated at the top of the cylinder and head area so the fins are usually concentrated in this area but it does vary quite a bit from one design to another. Take these 5cc ones of mine where there are more fins around the cylinder and none on the top of the head.

Also worth bearing in mind that a lot of the cast crankcase engines will have more in the way of fins than those cut from solid as its easier to produce them and that the modern ABC engines will be reving a lot higher than these engines with the resultant amount of heat generated needing to be dissipated. Engines destined for use in cars and helicopters will have considerably more cooling fins than ones for planes as they tend to be out of the airflow.

There are also drawings of the individual parts on Alex's site shoule you need them. Hope you do go ahead and make one and always here if you have any queries

 

Edited By JasonB on 26/08/2016 08:17:52

[geoff walker 1Participant @geoffwalker1]

Jason, thank you for your reply, informative and appreciated.

I do intend to make a firefly and will make a start with some of the peripheral parts like the carb and needle valve body for which I currently have materials. In the meantime I can research materials for the "big bits".

I recently made a carb for a Jones .605 and although untested it turned out quite well. The Jones was a considered build but I decided against it as I felt I needed a stepping stone. The firefly may well be that stone.

The drawings are no longer available FREE online, now £17.50 from my hobbystore. The links on aw's site draw a blank. I got my copies through a back copy of RCM and E march 2012.

If I may one more question for now. From your experience of making and running a firefly could you say that a marine option is feasible? e.g. marine flywheel and water cooled head. I intend to make an aero version first but a marine option would be of interest. I have a small 3ft. r/c launch currently electric powered, so maybe next year?

cheers geoff

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