Hallam Engine

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Hallam Engine

This topic has 62 replies, 11 voices, and was last updated 29 January 2014 at 13:59 by p j riordan.

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24 February 2010 at 21:37 #49132
Alan Worland 1
Participant
@alanworland1
I had passed down to me many years ago a single cylinder engine which I believe was made by a great uncle many years ago (early 50’s?)

Anyway it has been in a drawer ever since, and sometime ago I dismantled it, cleaned and oiled it up (with 2 stroke oil) put it back together and using the coil off my Morris managed to get it to run – please see video

http://www.youtube.com/watch?v=DCIcdRCUAyQ

My question is, does anyone recognise the engine and any idea why it wont operate at any other speed than what you see? Trying to alter the speed will cause it to stop! It was running a very oily mix of unleaded and 2 stroke oil – is it a petrol engine?
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24 February 2010 at 21:37 #2261
Alan Worland 1
Participant
@alanworland1
25 February 2010 at 15:50 #49162
Ramon Wilson
Participant
@ramonwilson3
Hi Alan,

Disappointingly the you tube video wont open for me – for some reason it says my java script is turned off or I need to down load the latest Flash Player. ??????

Though I have no experience with spark ignition I recognise the name of the engine which I believe was intended more for tethered car racing. When you say it will only run at one speed is this controlled by a throttle on the carb or are you varying it using the fuel needle. A pic or two would help

Good you’ve got it running though.

regards – Ramon
25 February 2010 at 17:50 #49164
Frank Dolman
Participant
@frankdolman72357
     I know v. little on this subject, so please understand that my questions

   are questions and not sly suggestions!

     a) Would it be an awful nuisance to arrange the ignition timing to be

   variable during running?

      b) Is the load in the right parish? The engine note strikes me as one

   that would tell a great deal on this score to a chap familiar with the engine!

     Great project! I much enjoyed watching the video. More power to your

   elbow, and please keep the experiments going.
25 February 2010 at 18:17 #49166
Ramon Wilson
Participant
@ramonwilson3
Hi again Alan, I’ve now managed to get the youtube open – good coverage of a lovely engine.

As I say I have no direct knowledge of sparkies but would say that this is running well below what you would expect. The rear view shows what looks to me like an extremely small venturi area. Couple this with the space taken up by the spray bar and the engine is going to be well choked – can you meaure this and see what the actual area is? An engine like this would need to ‘breathe’.

The engine is cracker though and sounds great – just wait till it peaks!
25 February 2010 at 19:08 #49171
mgj
Participant
@mgj
Well its a very long stroke engine so its never going to be a screamer, and changing the prop down a few pitches and dias might not be a great thing. If anything, as a 50s type longstroke with nowhere near square geometry, you’d want to go bigger rather than smaller and rely on torque -and the small intake area indicates that sort of design. But I agree it ought to be doing a bit better than that.

I suspect you could use rather less oil, which might be part of the problem – a good modern synthetic would get more fuel in there. Difficult to tell whether its running rich – or plug temperature is marginal, and you are running on a wettish plug. Probably its a bit rich – but it may not want to accelerate because:

You might also find that part of it is the ignition timing – I’d suggest getting it running as you have, and then advance or retard the timing till it runs at a maximum speed at that mixture setting. Then try leaning it a bit, because it sounds as if it is running a bit rich and uneven, and that often indicates retarded ignition. Work forwards like that. If its starting Ok then the ignition will probably be retarded, and as you try to accelerate spark timing is too late and it starts to slow you down, or even stop you. So advance the ignition by a small amount first.

If its a 50s design its probably designed to be run on leaded high octane – and possibly you are running on unleaded 95 octane pump fuel? If it is set up for that – with an advanced ignition, the faster flame front of the modern fuel would make any advance worse in effect. Can you get any super unleaded? That has the slower flame front of the higher octane fuel. Might just solve the problem in one.

Just fiddle with the ignition timing.

You might want to be a little careful about playing with the venturi area just at present. It looks like a piston port engine and therefore inlet timing and hence compression ratio and hence ignition requirements are controlled by the size and placing of that port. Secondly, the one great thing about tight chokes is that you get great tractability and good fuel atomisation. Both of which are highly desirable when you are not sure of your settings.

Those who advocate big ports, with all their many advantages, often overlook the fact that they are talking of higher revving modern oversquare designs with short port openings, where you need a large port. The old longstroke very often has plenty of time to get a full charge in despite port restriction – with the limitation that the long stroke does limit top end revs.

If you really want to increase airflow, you need only attach a tuned length inlet trumpet as a push fit, and you’ll increase airflow by a very great %age (~100%), and provide positive pressure at the port, assuming you do your maths right -which is also a very GOOD THING (particularly) with piston port 2 strokes. And without butchering an antique.
25 February 2010 at 20:15 #49177
Alan Worland 1
Participant
@alanworland1
Thanks for your response(s)! I enjoyed having it running. It would appear the speed is controlled by fuel flow valve, and virtually any attempt to move it from its setting will cause the engine to die – it is a one speed engine!

Ignition timing is adjusted by releasing a grubscrew on the cam, and moving it! a bit crude. Any guidance on what the timing might be? The Morris coil is ok then?

I did measure the bore and stroke, hence 10cc but can’t remember what it was but I think the stroke was longer than the bore.

It was running very oily as I believe the engine had never been run and I thought it might help to give it an easier time!

I don’t think it could be started at all by hand – I used the drill to get the engine to its ‘running speed’ whereby it seems able to maintain it itself, strange

It is a piston port engine, would the air intake benefit from a large radius to help air movement? Tuned inlet trumpet, how would I work out what’s needed?

If a larger prop was fitted would that help – I would like it to have a nice ‘slow’ tickover, it has a reasonable flywheel to help.
25 February 2010 at 22:29 #49183
mgj
Participant
@mgj
A coil is a coil – if it sparks that’s fine, and a big beefy spark during experiments might be useful!! There are more reliable ignition systems, like the modern hall effect triggered condenser discharge, and would probably suit better if its going into a car, but they are not vintage looking.

The stroke will certainly be longer than the bore – hence the comments about oversquare engines. Up to a point thats no disadvantage – it will be very torquey and will like a big prop. There is the old adage that revs sell engines and torque wins races!!

Tuned inlets and radii. I’m afraid, since I haven’t dabbled with tuned inlets for a while, my notes are all in a trunk upstairs awaiting unpacking after the last move.(15 years) The RACMSA karting section sold a very good pamphlet on inlet design and exhausts for 2 strokes. Alternately look up “organ pipe theory” on the internet, or tuned exhausts, and it will all be somewhere. Its not difficult, and the one formula you need is an easy one to crunch.

All you will need is RPM, and the speed of sound in exhaust and the speed of sound in the inlet flow. Freely available on the net. Measure the temp just in front of the inlet., and once you have the temp you will know Mach 1. (Not as good as IN the inlet, but it will be close enough to adjust to. IN being colder you know the final length will be shorter than calculated.

A round trumpet, so often left off modern aero engines carburettors will significantly improve airflow, without the complication of tuning the inlet

Timing depends on revs and the fuel and CR. Try 25-30 deg of advance for a fast setting . Hopefully someone with more knowledge of small 2 stroke timing will step in here because the distance the flame front has to travel (=flame front acceleration to detonation) also affects it, and I’m used to bigger engines. A 10cc engine could use more.

Can you not bodge some sort of adjustable grip, just to get a good position. Its just that with it starting so well, you have a known setting which you want to be able to get back to quickly .

Suggest you get it run in as is. Later get it started, warm it up and then advance to detonation under load (pinking in old money). when it just pinks and starts to run hard, you know you must back off a bit. (High speed detonation i mean, and for heavens sake back off immediately. Thats all we ever did for the racers to determine optimum before maps and all came in..

You’ll understand that for any prop/fuel combination timing will differ across the rev range. You can’t have a one size fits all timing setting. So if, with fixed timing if its to run well at speed, idle will be less good, or you’ll have to idle faster. Or you can compromise. If you can have variable timing then things improve dramatically. – and some of these electronic units nowadays will do that.

Still – get it running first, and have some fun.
25 February 2010 at 22:43 #49185
Alan Worland 1
Participant
@alanworland1
I think I had visions of it bursting into life and tearing itself off the bench!

I will, as suggested, run it in as is and go from there.

Thanks to everybody
25 February 2010 at 22:52 #49187
Ramon Wilson
Participant
@ramonwilson3
Hi Alan,
Meyrick has summed most of this up very well. However whilst I’m not advocating physically opening up the port at this stage checking that the area each side of the spray bar is sufficient to allow a reasonable amount of air through ought to be considered. It does sound as if it isn’t breathing properly but as Meyrick states this could be the result of the timing and the oil content as well. Indeed possibly a combination of all three

(Now that is hedge betting for you!)

By reducing his spraybar diameter to 2mm compared to my 3.2mm my friend Johns Nova engine ran the same 13 x 5 prop at 5100rpm to mine at 4000. The venturi diameter is the same on both engines at 5.5 mm dia. Quite a difference for such a small increase in area. I would have thought that the total open area needs to be around 14 sq mm minimum for an engine of this size. eg appx 6.5 dia with a 3.2 wide spray bar.

As said, knowledge of operating sparkies is non existant but as an I/C motor if it is as sensitive to the needle as you say then I feel this points more to

fuel/air mixture anomalies but the spark does need to be in the ‘right place’ for the relevant mixture condition.

Though this engine is no power house compared to front or rear intake types – the side porting as said will certainly limit its ability to rev – it should however be capable of more than appears – I would have thought that you should comfortably achieve around the 4- 5000 mark with the prop you are swinging even driving that flywheel as well.

‘I know someone who knows someone’ who is heavily into vintage tethered cars – If I can contact him I will see if I can get any further info or advice from him for you.

Regards – Ramon
25 February 2010 at 23:15 #49189
Alan Worland 1
Participant
@alanworland1
Thanks Ramon, I have no history of the engine, its just been in the family for years.

It would be great to get hold of some history and a copy of the original drawings – a quick pop out to the garage and I measured the venturi at 5mm. I am not sure what you mean by spray bar, the ‘throttle’ is basically a pointed needle valve which when unscrewed opens up fuel flow from its seat – is this what you mean?
26 February 2010 at 08:00 #49195
Ramon Wilson
Participant
@ramonwilson3
‘Morning Alan

I’m about to go off to a funeral – makes a change from the workshop I guess but when I get back I’ll take some photos of spray bars for you. There are several variations so depends what you have.

Glad to be of help, talk to you later

Ramon
26 February 2010 at 09:24 #49199
mgj
Participant
@mgj
Get it running nice and steady without all the hunting on the right fuel/oil mix, and be sure the timing is right (which the fuel/oil mix will affect of course)and then start to adjust. Would be wisest IMO.

On which note I will leave it to the experts. We’ve had a short video of an engine running, We have no idea what the timing should be, made no effort yet to optimise it, we know we are running on an inorrect mix, and we are already on about mods and spraybar thinning.

Get on with it boys.

Edited By meyrick griffith-jones on 26/02/2010 09:44:30
26 February 2010 at 13:03 #49207
Ramon Wilson
Participant
@ramonwilson3
You know theres nothing like “a boody good funeral” to put life into perspective.

On that note – spray bars. (Grannies please turn off now)

Alan this is the device by which the fuel is metered into the engine normally by a needle valve closing or opening. There are various make ups of these but the most commonest is one which passes diametrically through the venturi tube. One or sometimes two small holes are drilled though this tube which allows the fuel to be drawn through. If your engine has this type then it’s possible that it’s thickness is taking up most of the space available in the venturi. If this is the case then your engine is probably running in a semi choked state.

Another type, which from your description sounds as if you may have, is where the fuel inlet side screws into the intake tube just projecting through into the venturi. The needle held by a secondary part is screwed into the intake tube diametrically opposite and the needle passing thru the venturi and controlling the fuel mixture at the point of entry. Obviously the area each side of the needle in this type will be much larger than that using a more common spray bar.(for the same venturi dia.)

At this stage modification of anything is not something to consider – just ascertain as many parameters as you can.

I have got the contact number of the person I mentioned and have tried but no answer as yet.

There are several posibilities with this old engines problem. If it was home made then it’s possible that the port timing is not to print. The fuel you mixed may have been excessively oily. (I believe ratios vary engine to engine but there will be a ‘standard’ . I don’t know what that is at the moment – that’s one of the questions to ask Hugh). There may be a lack of aspiration and the ignition timing may be way off. All ‘may-be’s’ but picking them off one at a time you will get there.

It’s my intention to make a spark ignition ‘vintage style’ engine in the very near future. What you have is a really lovely vintage engine indicative of it’s age. If I can find out anything more to help you get it running as it should do for it’s type and period I will. It will also help me at the same time.

Regards for now – Ramon
26 February 2010 at 22:03 #49231
Alan Worland 1
Participant
@alanworland1
Thanks for your continued efforts, it is much appreciated!

It was running a very oily mix which virtually dripped from the exhaust! I seem to rmember mixing about a 30% oil mix.

I believe the engine is ‘home made’ possibly from a set of castings? and perhaps the port timing is not correct.

Initially I never gave it a thought that it could be for a car, but I suppose the flywheel gives it away! I fitted the prop to enable cooling.
26 February 2010 at 22:47 #49233
Ramon Wilson
Participant
@ramonwilson3
Further update Alan.

I have not been able to contact Hugh yet but have had some other luck which will hopefully prove enlightening.

I visited the friend who loaned me the Racer to copy this afternoon and we were discussing your engine. Turns out he has not one but three Hallams! Two were 29s – 5cc and the other was the same as yours.

I now have his ’60’ on extended loan plus a coil etc to have a play with and learn about the eccentricities of the ‘sparkie’!

The venturi is near the same diameter as yours – 4.8mm to be precise and surprisingly virtually the same as the 29’s! but the needle valve/spray bar set up is as I suspected and though quite small by most standards does leave a reasonable amount of choke area.

This evening I spoke with someone who has a great deal of experience with model engines of all types. He says the Hallam was produced around 1944-45. It was primarily designed for aircraft use and not cars as I surmised.

His general comments are:

Spark ignition can be more sensitive to needle settings than diesel or glow

Fuel is normally 4 to 1 but use a relatively thick oil – SAE70.

Timing bracket should be capable of movement through a range of about 10 degrees to establish optimum timing.

He considers that the flywheel is inhibiting the rpm so perhaps that’s the first item to remove and try. Suggested prop size is at least 14 dia x 4-5 pitch and it should produce around 4-5000 rpm as already thought.

So it looks as if you can begin with the fuel and reduce the oil content slightly. He also says that they are easy to flood and if as you say the ‘exhaust is dripping’ then that does point to an over rich state.

I didn’t ask about whether it was a commercial product or castings for home use. I have another call to make so will try to clear that one up for you.

I will need to set this engine up and get the electrics sorted which will take a day or two but will keep you posted on developments. I’m looking forward to this – it will be interesting to compare the two.

Hope this is of some further help

Regards – Ramon

Edited By Ramon Wilson on 26/02/2010 22:50:43
27 February 2010 at 00:09 #49237
Alan Worland 1
Participant
@alanworland1
Fantastic news! I have a Hallam 60! Wonder what the 60 refers to? Older than I thought.

Did your friend buy them/make them? If as you are suggesting it is an aircraft engine I guess the flywheel was put on to make it ‘complete’, seems strange as it is threaded onto the crank and I get the impression it keeps the cam in place (which is only secured by a small grubscrew) I take it his engines are not fitted with flywheels.

At present it has a 12 X 6 prop fitted

When I said the exhaust was dripping, I meant dripping with oil – it was a very oily mix. I used 2 stroke oil, are you suggesting that another oil type is used? Sounds like a thick engine oil.

How would you start this engine, could/should it start by hand?

An aircraft I have in the loft which hasn’t seen the light of day for many years has a spring starter, where the end of a coiled spring is wrapped round the blade and ‘wound up’ then released to give one or two compression cycles.

Enjoy your research! and thanks again.

Edited By Alan Worland on 27/02/2010 00:10:04
27 February 2010 at 07:57 #49238
Frank Dolman
Participant
@frankdolman72357
10cc is 0.6 cubic inch. Hallam 60 signifies the capacity.

Regards
27 February 2010 at 11:52 #49243
Ramon Wilson
Participant
@ramonwilson3
Hi Alan, Frank,

Yes ’59’ ’60’ ’61’ all signify a basic ten cc motor.

When you have the parameters right Alan you should be able to start this motor by hand though wearing a thick glove might be advisable. In the meantime until you do get the right settings carry on as you are, just be careful not to really flood it and possibly damage the conrod.

I’m not sure about the two stroke oil I will find this out for you later but I think Mike last night was refering to thick engine oil.

The spring starter you are refering to is probably on a small Davies Charlton motor. This was a feature on their maller engines for many years – ‘Quick Start’ as I recall. It worked well on the smaller of those it was fitted too especially the glow motors. I think Cox had a similar system too.

More good news Alan-

I have just spoken with Hugh who it transpires has obviously has quite some detailed knowledge of Hallam products.

He has a Hallam catalogue and is is going to call later to see if he can identify the example I have which I think is very similar to yours. Having described the engine to him he thinks it may be a ‘nine’ (cc)

Apparently many Hallams were produced as kits of parts for the home builder as well as ready built versions so that may explain the variation on capacity. Likewise the fitting of the flywheel – could have been for boating or car use or just to be able to run the engine on the bench.

Concensus now is definitely the 4-5000 rpm band and fitting that larger 14″ dia prop.

I have taken some pics of this one for you perhaps you can compare yours in detail.

As you can see there is no propellor driver fitted to this engine either. I will make one that fits to a split tapered brass collet which will have no effect on the original engines make up

These last two are for interest. The first shows the Hallam venturi against that for another engine of the same capacity, an OS Max 60 racing marine engine awaiting renovation. Rev band on this is just a tad higher of course!

The last shows the Hallam compared to another marine engine this time an OPS 65 which was reclaimed from a very salt encrusted and siezed state. The carburetter fitted is from a Super tigre engine bored to 9mm dia. but this really ought to be larger for this engine to operate ‘where it should’

I’m enjoying his Alan, now I’m off to get that engine prepped. Will let you know on further developments

Regards for now
27 February 2010 at 13:54 #49247
mgj
Participant
@mgj
Yes, oil is interesting stuff, and in the 40s and 50s all you could get was castor- good but gummy. or mineral, a lot less good but all there was. In particular it burned and contributed greatly to the ill manners and little stinker image of the 2 strokes. Carbon build up, fouled plugs, blocked exhaausts etc.

Fortunately we have come a long way. The modern 2 stroke oil is specifically formulated for low ash, so plugs and internals keep clean which contributes greatly to good manners and easy starting . It also removes fuel lacquer, which improves lubrication, though modern fuels are less prone to that.

Then along came the fully synthetic, which after some hesitant starts, demonstrated some very considerable advantages.Notably it doesn’t burn, which means that its ejected from the exhaust with all the heat its carrying. so its very good at getting rid of heat. It also, because of its formulation clings well to hot surfaces- far better than mineral – and thats a particular advantage in a 2 stroke firing every rotation, where temperatures tend to be much higher. And you don’t have to use so much, so its a lot less messy. Some of these high performance synthetics are running down to a couple of %, and not much more than that in the converted to petrol model aero 2 strokes such as the MVVS.which will be running much higher revs and much higher cylinder temperatures (especially when piped) than this sort of engine. Indeed so good are their lubricating qualities that engines can take quite a time to run in properly.

So if I was going to treat an engine kindly, and wanted it to really last, I think I’d run it in on a modern low ash oil and allow it to wear a bit. Then I’d switch to a synthetic – better lubrication and better heat rejection being all to the good.

It seems to me that to throw treacle into an engine and slow it down and reduce performance is possibly a slightly outdated way of lubricating it. It may well work, but there is a difference between working and working well. – and starting easily and not having to clean off plugs etc.

If the fits inside the engine permit sealing and the use of modern oils, that would, I suggest, be the sensible way to go, particularly when one is dealing possibly with poorer quality materials. If not, then you have to use the old. Unfortunate but needs must.

Just a thought.

BTW, I was wondering why a flywheel would inhibit revs? I can understand if a flywheel and a prop would be accused of reducing acceleration to max RPM. Its all to do with the radius of gyration. You don’t see a ballet dancer extending her arms to speed up a spin do you?(the mathematics being the same)

Basically the circle described by the CP of the blade where the aerodynamic forces act, is going to be greater in diameter of the flywheel. So its the load on the prop that is restricting revs – or the leverage exerted by the load.). The flywheel provides almost no load other than to resist acceleration to a speed, (inertia)until a load is applied. We know that’s true because by changing to a smaller prop and moving CP inwards revs go up other things being equal – or you can carry more pitch for the same revs.

So something is wrong with the logic somewhere.

Edited By meyrick griffith-jones on 27/02/2010 14:05:05

Edited By meyrick griffith-jones on 27/02/2010 14:07:34
27 February 2010 at 15:37 #49251
Ramon Wilson
Participant
@ramonwilson3
Hi again, I didn’t get far with that! – since my last and Meyricks post above some further developments – Meyrick, please, just remember for most of this I’m just the messenger here

Taking the oil first however, yes modern synthetics do have a good reputation for keeping the engine clean as well as lubricating in as efficient manner if not more so than ‘good old’ castor. The downside with using castor is that it will not burn as such and leaves a deposit on all surfaces, inside and out. Not so much a downside ‘inside’ but the outers are as you say ‘gummy’ to say the least and in most cases downright bloody terrible.

I have a new and as yet unrun Ukranian built (Stalker ST61 LS) ABC engine purely designed for (C/L) aerobatics and there is a gallon of ‘synthetic’ ready for it. My understanding to date is that if pure sythetics are used following castor on a reasonably well run engine then this will remove the varnish and lead to poor sealing and hence performance. Because of his fact some use a mixture. I would not use this oil in any of my other ‘stunt’ engines or others previously run on castor for that reason. Standing the risk of being accused of stating the obvious high performance engines need a high energy fuel and the less oil (given adequate lubrication) that contains the more that can be achieved. I’m thinking here more of diesels and glow ignition model motors. The more modern model engines are incredible pieces of the engineering art. The quality of machining ensures consistent good fits and tight tolerances – they’re precision instruments to say the least and I agree, good, quality lubrication is important and needs to match the requirement.

This engine however is what it is, side ported, made around 1950, possibly at home with no esoteric materials involved. The advice so far from those who have good knowledge of running and operating this engine and those of similar ilk is clear – use it at 4:1 and use a thick SAE70 oil. I don’t doubt your knowledge Meyrick and your sincerity to see Alans engine improve but is this sending someone down a road he doesn’t neccessarily need to take? On this engine, at this stage personally I think it would be.

Alan,

I have had another look at the video and it appears both engines are identical.

Unfortunately Hugh cannot get round today but we have had another long conversation

Further info is as —— quote

His Hallam catalogue states it is the 12th year of production – it doesn’t give a date.

Hallams ceased producing most of their line throughout the war as most were aimed at the model aircraft market the flying of which was banned for the period. Here it gets a bit confusing but apparently in 1944 they released and continued to produce the ‘Nine’ which was intended for tethered model cars.

The ‘Nine’ was also ‘stroked’ to give a ‘ten’ – the stroke was increased from .875 to 1.00 the bore remaining the same on both engines.

The catalogue states that the engine would turn the (recommended) 15 x 9 prop at 3,400 rpm. [To me that’s a big prop and pitch even for a 60!] It does not list any power outputs but does give a static thrust expected with that prop of 31/2 lbs. and strangely, even contradictory given the times, it states that it would power an aircraft of 5 – 8 lbs weight.

Now get this – it gives the Flywheel rpm as 15,000 Quite! however before Meyrick gets excited we both felt this is totally unrealistic not least because of the side port layout. I would think that the 1 in front is possibly a typo! but ??? it certainly has bearing on Meyricks thought on the flywheel ‘inhibition’ – BTW remember that was just a quote passed on – Mike called me back specifically to comment on that point.

The engine cost just £1-7/6d with a flywheel and £1-5/- as a prop version but whether this was for castings (probably) or the built engine I’m not sure. (You can always think of more questions to ask after the phone goes down)

Well that really is about it for now Alan. Like you I am now on the same learning curve, indeed somewhat behind as I have still to get this to run. I’m open to all thoughts though and will take note of all comments but , as I’m sure most would agree, it’s only natural at times to ‘follow ones nose’

Best regards – Ramon
27 February 2010 at 15:57 #49253
Ramon Wilson
Participant
@ramonwilson3
Alan I forgot something.

Hughs advice to me was to fit the engine with a glowplug -an adaptor will need to be made – and try running it on methanol (and oil – castor that is or commercial glow fuel) first. Not for long just to establish its abilty to run – you should achieve a more flexible run against needle valve settings.

The timing cam has to be set in relation to the piston and the timing bracket should be capable of movement and locking whilst running. He recommends a retarded spark for starting – just ATDC

There is also the fact that if yours was home made the porting/timing events may be restricting things.

Just thought – you do have the piston in the right way? Some side port pistons have a step on the top to one side – this has to go on the transfer side of the bore.

Now I really am off to the workshop!
27 February 2010 at 17:59 #49256
mgj
Participant
@mgj
Ramon – please don’t be obtuse.

Firstly the flywheel. Just think in control line speak – how to get a shaft run. Take the prop blades off. So the whole business of the flywheel is an ill considered red herring. I am surprised that someone as knowledgeable as you on the i/c engines considered letting that one through.

Secondly the oil. You wish to run your engine on SAE 70 treacle and gum and soot up the works unnecessarily – by all means. But why you should inflict that on a novice, when plainly it will be much easier to get an engine that’s being a bit feminine going well on modern oil, and then, if the vintage bit appeals, change back. As an added bonus it will also protect it better the while.

Running the engine on methanol – well that’s fine, but its been checked that it’s compressed correctly for methanol rather than petrol? Methanol likes a lower compression ratio than petrol, and so running it on methanol without changing CR may make life interesting. It also likes a rather different fuel air mixture, so this novice now has to find a different start settings entirely??

I don’t quite see the problem. He mixes a low ash 2 stroke fuel at 25%. The engine starts and runs already. All he has ro do is fire it up and move the timing plate a bit, till it runs best and probably stops being awkward. Then he can adjust his needle valve for optimum.

As for his piston being in the right way – well its a piston port engine. so there is a hole in the piston to allow the mix through. That is the inlet timing valve and primary compression seal. So, its quite possible that if the piston were in the wrong way round, we might know about it by now.

As for the port timing. It may or may not be perfect, but with a 2 stroke you have a choice. Lift port height and you lose torque and gain top end. Lower it and vice versa – in principle anyway. So if its not precise, it may not develop its full potential but it won’t be a disaster. However, since it runs, we can at this stage be reasonably sure they are not a mile out. If it were miles out the engine would be partway to being unrunnable. As long as the transfers open a bit before the exhaust reaches fully open and promote good scavenge, thats about as good as it gets. Since its not a boost ported engine, with open loop scavenge its unlikely to be very critical is it? I mean its hardly likely to have an oversize crankcase and early transfer timing suitable for piped operation with awkward starting thrown in for free?.

.

Thus far we have a page and a half of recommendations, some of which are plainly erroneous and others utterly inconsequential, on an engine that basically works but hasn’t yet been run in.

Nor is it fair to claim that you are simply the messenger – you are the one who has all this I/C knowledge and should be well able to filter for the benefit of a beginner. Or, if you are not, then it might be better to cease speaking authoritatively

Lets get off autobabble and start giving Alan steady, reasoned, one step at a time advice as he needs it – and preferably have it right and relevant , so he has the best chance of getting this motor going as is, and then later he can start doing whatever he wants in the vintage world – he can run it on paint thinners if he wants to, but at least he will have a known workable baseline for reference.
27 February 2010 at 19:00 #49257
MichaelR
Participant
@michaelr
I notice that your engine is fitted with a flywheel, if you are running the engine with a propeller I would remove the flywheel, then see how it runs.

Running with both could be loading the engine and not allowing the “Revs” to build.

Just a thought. !!
27 February 2010 at 19:11 #49258
chris stephens
Participant
@chrisstephens63393
Hi Guys,

Let me start by saying I know very little about model two strokes, but I have a little experience with the real thing. Are we really saying to run these toys on one quarter oil/ petrol ratio? Or are we confusing one quarter (25%) with 1:25 oil/petrol mix?

On road going two strokes, if memory serves, the ratio could be in the range of 1:25 or 1:40 even less with a decent modern synthetic oil.

I am willing to be corrected, on the mix issue, but I do find it very strange that little ones need so much more oil compared to their big brothers, considering that the engineering is so very similar.

If someone has the definitive answer can they quote from an instruction manual and not quote hearsay.

TIA

chriStephens
Author

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