new to spark ignition help please

An open forum to ask members questions about old time spark ignition engines.

Moderators: Frank Klenk, SteveM

new to spark ignition help please

Postby jim paton » Fri Jul 14, 2006 12:32 am

I have just bought an O&R spark ignition engine.I think it is a 19.I am totally new to this, so I have a few questions.I am in England.What fuel should I use.Is 3 parts petrol to 1 part oil correct.Other listings mention 70 grade oil.Is this SAE 70.The nearest I can think of here is Hypoid gear oil .What about using 2 stroke oil as for my strimmer and lawn mower.They normally run on a 25/1 mix. The engine came with a cylindrical coil and lead to the spark plug.What else do I need.Is there a commercial transistorised set up I can buy? Where would I get a new spark plug if I needed it? What do I do with the advance /retard lever for staring and running.Thanks in anticipation, Jim.
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england

Postby loucrane » Fri Jul 14, 2006 12:46 pm

Jim,

You should be able to run your engine on glow engine fuel, with 25% (preferably all) castor, and no or little (say, 5%) nitromethane. FAI fuel (80% methanol, 20% oil) likely needs added castor to bring total oil fraction to at least 25%.

Gear lubes are very different from the types used for high speed sliding contact as in piston on sleeve, shaft in bearing, crank and gudgeon pins in connecting rod. There may be vintage motorcycle shops around which carry heavy, single grade motor oils. And, yes, 70 Weight is the SAE 70 spec. 3 to 1 (petrol to SAE70) should work. For early attempts, perhaps a bit more than 25% oil? the spark engines were designed to run on the heavy motor oil and petrol, and in these proportions. Modern oils and pre-blended 2-cycle fuels for lawn mowers, etc., are more likely to cause early and severe damage to an O&R engine.

I hope you have an understandable wiring diagram for a typical spark setup. Key adjustments are spark plug and breaker point gaps. About 0.010" to 0.012" should be close. Make sure the breaker points are fully open when you check and set the gap.

I'd suggest that you set up for initial running on a test bench, and with the battery not installed, work through reaching and adjusting the controls.

All wiring should be cleanly connected for minimal losses. By the way, you will likely short (earth?) yourself across the high voltage wiring at some time in the near future. The voltage may be 9,000V or more, but at very negligible amperage. A surprising jolt, yes, but usually not damaging. Wouldn't recommend doing that if you rely on a pacemaker...

With a glow fuel, mixture settings are far more tolerant, as the methanol will burn under quite unfavorable conditions. If you do start with glow fuel, expect to need to close the mixture needle considerably when you switch to petrol/SAE70 fuel.

The lever just behind the propellor is the spark advance/retard control. Turning the lever in the same direction the prop turns 'retards' the spark, and against prop rotation 'advances' it. For first starts, be sure this lever is well 'retarded'.

You can check that the circuit is functioning correctly by removing the spark plug and laying it against the cylinder head. Switch the circuit on and rotate the propellor. At about top dead center, the spark should fire audibly, perhaps visibly. ...Every time. It may not fire at fully retarded lever position, so 'advance' from that end a bit, until it does.

Don't leave the circuit 'on' any longer than necessary. While the engine runs, the breaker points are opened and closed - of course. At rest, the breaker points are more likely 'closed' - which can drain your battery quickly, and overheat the coil.

When the engine starts, it will likely run roughly. Bring the spark lever up a bit, which should smooth things a bit. Particularly on glow fuel, the exhaust should be quite smoky (vapor, actually, of oil and some unburnt fuel.) Lean the engine a bit, but not so that the exhaust vapor is severely reduced. The oil that is in the exhaust gases shows that it has passed through the running parts and remains unburnt.

In a way, a spark engine can be tuned similarly as a diesel. The spark lever directly controls ignition point; a diesel's compression screw has the same effect. The mixture adjustment works the same in both cases. Unlike in the case of a diesel, a spark engine will run quite 'rich' safely. Ignition is from the spark, not compression in a very small combustion chamber. And, as often the case with model diesels, load, RPM and spark point can be coordinated for relatively low vibration. Also, over-advancing spark is not kind to the engine, nor to fingers at the next start (should you omit retarding it a bit.).

The sounds are different, of course - spark is usually quite a bit louder! If that is a problem in your area, I have no suggestions...
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

Postby gossie » Sat Jul 15, 2006 12:51 am

And what ever you do if you run it on glo fuel, do not, repeat do not put that into the plastic tank on the back of it---if it has one.
It will be melted in a flash by the methanol. Gas will be okay though.

Good post Lou, and 'right on the money', felt it wise to do the fuel in tank warning though.

I had an O&R 23 about 30 years ago in a Goldberg Interceptor on spark, and it was quite happy on either gas or methanol fuels.
Great old engine, and from memory the 19 is far more rare than the 23.
gossie
 
Posts: 138
Joined: Tue Nov 30, 2004 7:47 pm
Location: Gold Coast Australia

getting started

Postby jim paton » Mon Jul 17, 2006 12:08 am

Thanks for that. Are there any links to wiring diagrams.I have a coil that has come with it.
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england

Postby loucrane » Mon Jul 17, 2006 2:58 pm

Jim,

Unless someone else comes up with a source for a standard wiring diagram, perhaps you could check among acquaintances...

If no joy, I may be able to scan in and post such a diagram I have around here, somewhere...
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

O&R 19 Wiring Diagram

Postby Matt » Mon Jul 17, 2006 4:51 pm

This should help:


Image
Matt
 
Posts: 41
Joined: Tue Jan 07, 2003 4:28 pm
Location: New England

spark ignition engines

Postby jim paton » Tue Jul 18, 2006 2:19 am

Thats great. Its even my engine.Do you know what capacity the condenser should be?
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england

Postby loucrane » Tue Jul 18, 2006 1:55 pm

Well, thanks Matt!

Jim, I don't recall the capacity for the condensor, but recall seeing a test in a 1948 book that tested a range and found little significant difference within that range. As the wiring diagram shows, most used a small metal cased condensor with a mounting lug built on.

I'd also suggest building a good quality switch into the circuit. The diagram shows a pneumatic shutoff timer, as used 'in the day' to limit run duration for free flight models. These 'timers' functioned similarly to a pneumatic door closer - small air bleed to slow the motion of the piston in the casing. Note that when the plunger shown is fully down, it opens the connection.
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

Postby propwobble » Tue Jul 18, 2006 5:00 pm

for typical 3v coil
nominal capacitance: 120v dc .1 mfd



cheers
propwobble
 
Posts: 101
Joined: Tue Aug 26, 2003 4:53 pm
Location: Pacific Northwest

Postby loucrane » Tue Jul 18, 2006 7:31 pm

Jim and Propw,

That 0.1MF capacitance falls smack in the middle of the range tested in the book I mentioned above.

The book is the 1947 edition of the Model Motor Manual from Air Age,Inc., (still, I think, publisher of Model Airplane News). Authors were Louis Garami and Howard McEntee - no lightweights in those days.

Air Age, Inc., hired a test to determine the effects on time to saturate the coil due to different capacitances. Test covered from 0.05MF to 0.2MF. Least lag was with the 0.05MF and most with the 0.2MF.

More importantly, at 7000 RPM, the longest delay (0.2MF condensor) represented less than 1/2 degree of shaft rotation. The 0.05MF condensor took about 1/4 degree...

I found, among my spark goody-bin stuff a few metal can, mount-tabbed condensors marked 0.05MF 450V. I trust they'll serve...
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

o and r 23

Postby jim paton » Tue Jul 25, 2006 2:44 am

Any info on the "booster terminals" in the wiring diagram would be helpful.On my engine the tube carrying the fuel mix into the case is a bit loose.Should I be thinking of soldering it or using araldite. I have looked at the points.One is worn away more than the other. Do I use the advance / retard lever to set their opening to about top dead centre. The lever seems to move through a very large arc.The general state of the engine seems exellent.i just need time to get on with it.
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england

Postby loucrane » Fri Jul 28, 2006 11:04 am

Jim,

The base of the timer housing should be bolted to the front of the crankcase. You need not worry about where to set it, it's preset.

With the spark plug removed so that you are not fighting compression, you can observe when the points are open - go for a position about the middle of the shaft rotation between where they open and where they close.

It would be nice to have clean fresh points, if at all possible. ...and to heve them meet square and flush over their full surface. The engine should still run with used points, though.

Luck!
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

spark ignition engines

Postby jim paton » Sun Jul 30, 2006 11:54 pm

thanks for that. nearly there. the fuel mixture intake tube into the crankcase is loose, so I guess I am going to have to rectify that before I start.I am not sure how. More news soon.
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england

O&R23

Postby jim paton » Thu Jan 31, 2008 11:05 am

I was browsing through this again.I bought a transistorised ignition unit frm Texas timers.it runs really well
jim paton
 
Posts: 17
Joined: Thu Jul 13, 2006 10:19 am
Location: england


Return to Spark Ignition Engines

Who is online

Users browsing this forum: No registered users and 8 guests

cron