Jason's Firefly .46 Build

Thats comming together wonderfully well Jason:- great build log

Stew

Thanks Stew.

Just a few decent shots rather than phone pictures of the assorted parts and assembled engine

J

It's looking great Jason, nice job. Are you planning a muffler / silencer for it later?

If designed correctly, a muffler can increase power, lower the combustion chamber temperature, and reduces noise of course. There are lots of references for this if you google "expansion chamber design for two stroke engines" and/or look at pipes for race two stroke motorbikes.

Thanks for the build log.

JD

Well I managed to find a bit of time between the F1 qualifying and the Olympic road race to start it up.

Just knocked up a simple stand, bodged a tank from a film canister hence the bubbles in the fuel line and fitted the only silencer I had which is probably a bit restrictive as its off a 0.25 engine. Oh and the fuel is at least 20yrs old!!

Edited By JasonB on 28/07/2012 16:52:50

Hi Jason

Fantastic job!

The question I would like to ask is.. looking at your machining photos I assume that the machine you are using is a Warco 280V-F with varispeed drive(it looks like it to me from the colouring & leadscrew knobs), as I am awaiting a 250V-F I am wondering what size Dickson type QC toolpost you have fitted on your machine. I have a 0 size clone (Bison) from a previous machine, that I intend to use instead of the 4 way post as supplied with machine (together with a total of 10 toolholders), & with it being hardened, therfore unable to machine counterbore on the underside to fit, it looks like I will need to make a new toolpost spindle, you wouldn't happen to have a drawing/sketch of the post/spindle dimensions,or suggest a suitable tool to enable boring out the QC block (which I am loath to do at the best of times).'solid carbide' perhaps?

Hope you can understand my question. perhaps other members can help?

Regards

George

Edited By mechman48 on 28/07/2012 20:53:16

Hi George, yes it is the 280v-f and I have the smaller 00 original Dickson which like you I was loath to part with as I have about 20 holders.

First issue was height so I just cut a square from some 3 x 1/4 flat stock to fit over the stud. You can see it in this photo

Second was as you say getting teh post onto the spindle, there is a larger cast spigot that comes out of teh topslide and the threaded spindle out of that. My solution was to use a boring head to reduce the OD of the spigot until the toolpost fitted over it. I have a simple sleeve I can drop on when I want to use the supplied 4-way post which is handy for large dia boring bars etc.

Hope that is clear, let me know if not and I'll take some pics in the morning.

The other thing I have done ever since I bought the toolpost is I use an extended "nut" which is cross drilled to take the tommy bar of the chuck key rather than need a spanner, its one less item to misplace.

J

Jason

Fantastic job. Its great to see it running

I rigged up a better fuel tank and set the engine up outside on the workmate so it sounds a bit better now though the exhaust still needs sorting.

You can see the barb barrel opening and closing as I move the camera around to the front but had to stop the video before the other clamp came loose allowing the engine to take off

Well done Jason,

Another fine build - and pretty quick too!

Neil

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

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

Thanks Ramon, The suggested prop is an 11x6 or 11x7 but I went for a 10x7. 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

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.

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

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

Ramon the only other prop I have is a 9x6, 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

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

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

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

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