Scale model Economy hit & miss engine builders wanted

[Charles 2010Participant @charles2010]

What setting do you suggest Ronnie

 

I am a complete novice when it come to petrol engines ….

 

Anything you can help me with will be taken into consideration …

 

I would like it to run as a hit and miss !!!!

 

So what are the secrets ????

[JasonBModerator @jasonb]

You just need to play with the governor springs so it will fire once every 5-8 cycles without dying on you and will pick up the firing rate as load is applied. The latch position can also be altered so it catches with more or less governor arm movement.

 

Jason

 

PS Jonathan, your IHC is progressing well, will post an update soon.

Edited By JasonB on 14/11/2010 18:52:19

[Charles 2010Participant @charles2010]

Hi Jason

 

Thanks for the info..  I do have a selection of springs…  so nothing to do with the actual timing of the engine?

 

I have posted some more photos …

 

This is as far as I have reached with the carb.

 

It is modified from the drawings as I could not achieve and hole of the right size through the jet of M3 so I have made if M4.

 

Regards Charles

[Charles 2010Participant @charles2010]

Soon I shall be making up the “air filter ” part 208.

 

There is no indication as to what is used to filter the air entering through the 5 holes. They are large well 3.35mm which will not stop too much …

 

I think the use of a foam insert might be a idea.

 

Any other comments please ?

[ronnie barkerParticipant @ronniebarker18785]

charles

 

as jason says you will have to play with the gov springs to get it to hit and miss and keep the timing about 20 degrees before top dead centre.

 

i think the carb sdhould be changed from the drawings as on the full size the carb is alot different to the drawing.

the full size carb is very crude but works very well, i think the carb on the model is well over engineered and is not ideal for a hit and miss engine.

 

if the engine runs hit and miss and fires every 6 or 8 beats then you dont need much fuel.

 

jonathan

 

jason, i cant wait for a update

Edited By ronnie barker on 15/11/2010 08:00:00

[Charles 2010Participant @charles2010]

Has anyone any details of a full sized carb as it would be interesting to compare with that the one for the model.

 

Thanks for the info on 20 deg BTDC .

 

Regards Charles

[ronnie barkerParticipant @ronniebarker18785]

ive just had another thought, dont put the webster mag on the engine as the full size would NEVER of had one if run on a spark plug.

 

what you could do is to make a copy of the wico ek mag which is what would have been on the full size.

if you was to do this on this size of engine then it would be very handy as you could make it trip as the full size mag and hide the contact points inside so it would look as if it was running as it should, also it would be very easy to set the timing as you coud ajust the lengh of the square trip rod as on the big one.

 

ive said all this to LA services  they didnt want to know, for a little more work you could get it so much like the real thing

 

jonathan

[Ian S CParticipant @iansc]

Jonathan, full size hit and miss motors can be found with just about any ignition system ever made, theres a little museum about 100 yards from were I live, there are motors there with the Wiko type rocking armature others with various rotary mags, one with a low tension system using dry batteries. Some have been converted from low tension to high, about the only thing not there is a hot tube, but that could happen. Ian S C

[John OlsenParticipant @johnolsen79199]

Hi Ian,

 

We have a big one with a hot tube at Motat, currently under restoration.

 

regards

John

[ronnie barkerParticipant @ronniebarker18785]

ian

 i agree that full engines have alsorts of ignition systems ive had quite afew full size engines.

 

my point about the economy is that no full size engine  would ever have a webster low tension mag and a spark plug it just wont work!

 

if you made up a wico or sim type mag it would look correct and would be handy to hide the contact points

 

jonathan

[Ian S CParticipant @iansc]

One thing thats often done full size is leave the dud mag in place and use the points, and hide a coil and battery in a tool box. We got a motor and found it had a carb from a Model A Ford, I made a simple venturi out of a bit of steel from the scrap bin, think the bore was 1/2″, the intake pipe came up from the fuel tank and entered at the throat of the venturi, opposite that I  put a needle on the end of a screw to control the fuel flow, on the outer edn of the tube I put a moveable cap to act as a choke. Think I spent all of a couple of hours on it, bolted it on,  suck through some fuel, give it a swing and away it went, just needed to close the needle valve a whisker.Now that it has oil and a bit of muck, you would’nt know it was’nt original, unless you know the motor. No butterfly.

          Ian S C

[Charles 2010Participant @charles2010]

Well later today Saturday a few friends and I will be trying to start the engine …

 

Will it be hit and miss or all misses !!!

 

I will report on progress and what we used for ignition etc in due course .

 

 

Regards to all and thank you for all the helpful comments

 

Charles

 

[Sub MandrelParticipant @submandrel]

C’mon Charles,

 

We’re dying to hear a report…

 

Neil

[Charles 2010Participant @charles2010]

Well it was all a bit hit and miss.

 We all gathered at 11:00 and established that fuel was being drawn into the carb so the ignition was attached and on the first pull over it popped and smoked but nothing more than one fire.

 Then during the next 90 minutes everything was tried and we had a second firing of about 5 ignition strokes and then nothing.

After lunch one friend came back round and we fitted the third piston ring with careful attention to width and depth  AND the fact the the rings have a top and a bottom which I did not realise … was taken in to account and properly fitted.  This gave much more compression than when we left it before lunch.

Then on the first pull again engine did run for 12 revolutions and the stopped and then another pull and it fired and nearly got up to speed but finally petered to a stop.

That was a bit of luck as I then noticed that the crank shaft has moved …  The Loctite 603 had let go …  So the repair was made by reapplying 603 but the crank will need to come out and I will be pinning it in all 4 places to stop that ever happening again …

 We also found at that too much fuel was going into the engine …

 There is no disappointment on my part for had it run without problems one would not have to work out why will it not run and learn nothing …  Even motor engineer friend and all his experience is at a loss as to why is does fire but then does not continue to fire….

 We have spark, fuel, compression but that is it …

 

Any ideas …  may be a rebuild of the carb to a simplier design???

 

Regards Charles

[Ian S CParticipant @iansc]

I wonder if on that best run the govener was throughing out and not picking up again?

                                       Ian S C

[Charles 2010Participant @charles2010]

I did look at that particularly and saw that the govenor had not gone into miss action.

 

It is thought that it is a fuel problem …  The carb has an integral non return valve that I added to the basic construction so it was not a case of too little fuel we think it might have been too much fuel !!

 

As soon as I have more news I will let you all know ..

 

ragards   Charles.

[ronnie barkerParticipant @ronniebarker18785]

charles

 

well done on getting your engine to make a sound and dont be put off that everything didnt go right first time.

 

i think you are onto somthing with the fuel these engines had very crude carbs because when running hit and miss they dont need very much fuel, the carb for the model to me seems well over engineered, i havent yet seen a model economy that runs right on this carb.

 

the other thing to check is your non return valve as ive fitted these to models and the engine wont suck the fuel up but i alawys bed the rings in first now before i try and start up, the more compression the better they run.

 

the other thing i would check is the govnor spring that sits behind the speed lever make sure its the right tenion, ive failed on this trouble before

 

anyway i took up golf now as i found a far better engine builder than me!!!

 

jonathan

 

 

[Sub MandrelParticipant @submandrel]

Glad things are moving in the right direction!

 

Neil

[Charles 2010Participant @charles2010]

Hi All

 

Yes all going in the right direction .

 

I will check the non return vavle as it is integral with the jet tube.

 

I have been looking in Westbury’s book and he suggest a simple carb and I think I may try that …  I hope my sketch does justice to his idea

 

This does away with the throttle and  ..  A hand can act as the choke.

 

So I am working on that !!!

 

I have pinned the crank and all is well as it went back together easily .. the key ways do not alingn but that does not matter !!!!

 

I will check the tension  of the spring but at the momenthe engine has not reached speed to throw the MISS into gear…  it is fun waiting …

 

I wish i knew how to make a nice tapered jet screw !!!

 

Regards Charles

 

 

[Engine BuilderParticipant @enginebuilder]

Charles, have you read the earlier posts in this thead?

John Wood1 had the same problems as you and they are now resolved.

David

[Charles 2010Participant @charles2010]

I have been in close contact with John but his is a fully prepared kit unlike mine.

 

I have read the posted but I must have missed something saying that John has changed the carb.

 

I will back through then all and carefully digest the information.

 

Regards Charles

[Engine BuilderParticipant @enginebuilder]

Charles, I was refering to the general problems of getting it to run , not specificaly the carb.

David

[Charles 2010Participant @charles2010]

Hi David

 

Ok, yes I have tried to take into account all the tips but not yet tried it on Butane …

 

All I have read points to the carb and it has also been mentioned on here ..

 

I will keep working on it and repart in due coure ..

 

Regards Charles

[Ian S CParticipant @iansc]

Charles, that diagram of a carb , the design that I use, but I just made it up as I went along, did’nt  realise it was a published design, its really just a mixer valve and it works well on full size engines, and I’m going to use it on an engine that I’m building. Ian S C

[Charles 2010Participant @charles2010]

Hi Ian

 I wonder if you have any ideas on dimensions.

 I have been discussing this with other friends with engineering back grounds and they think the the original 4.75mm air entry hole is way too small to feed the engine with an air and fuel mix.

 They are of the opinion that the opening at the centre of the venturi should be say 50% that of the  outer bell which would be about 10mm for this engine.

 Any thoughts on what  you  have tried?

 I am just out to go and buy stock so that I could make up several mixer carbs  that sounds like over kill but a lot of engineering fun .. Thank goodness I am retired.

 Another friend is working on an electronic ignition system where the spark can be advanced and retarded by electronics. I know that gets away from the simplicity of the engine but again will be a lots of fun as I am also a Radio Amateur

   Regards Charles

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