Kerzel a'la Tel

[tel]

And now the 'fun' begins. Had a session with it today - lashed up a rough ignition 'system' with a Briggs coil and a few odds and ends. No luck so far, but it was interesting nevertheless. I think I've got the timing pretty close, it is getting fuel and I seem to have enough compression, certainly have enough vacuum. Tried for quite a while but couldn't get it to cough. Methinks I'll have to do a better ignition set-up before anything happens.

Got some proper 1/8" spark plug wire on order - that might help.

In the meantime I might make a start on the bits for the governor.

 

[gbritnell]

Hi Tel,
Have you actually checked for spark? I have tried to use magneto type coils in the past, running them on 6 or 12 volts without much luck. It seems like the magneto puts out a lot more voltage to operate the coils properly.
gbritnell

 

[tel]

Well yes George, in a way. I've tested the set-up with another plug (external) and there is spark to it, but whether it is happening inside the engine is another matter. I'm using a car battery charger as the power source at the moment, and can see no real change in the spark by switching from 12v to 6v, and the amp meter is showing the cut-off when the switch circuit opens.

Truth is, I haven't really given a lot of thought to the ignition as I've been focused on the engine build, but it is now to the point where I will have to decide on what to use for the finished product - 'fraid it's an area I don't know much about. Any advice/words of wisdom appreciated!

 

[arnoldb]

...car battery charger as the power source...

Can you try a real battery Tel ? - maybe borrow the ute's for a couple of minutes...

98% of car battery chargers I've encountered only rectifies incoming AC, with no "smoothing" at all. Without going into the techie details, you're at a severe disadvantage by just using the battery charger, as it does not necessarily have the instantaneous oomph required to fire the coil for a good spark, especially in a higher pressure environment such as inside the cylinder.

Kind regards, Arnold

 

[putputman]

Tel, is there any chance you can get your hands on an old Model T Ford buzz coil. They work very well on these old hit & miss engines. I use a 6V battery on mine. I think some people use 8V for more zapp.

 

[swilliams]

Here's a couple of thoughts on how things work as I understand them. I'm not suggesting any direct practical action that should be taken as a consequence of this. Just having a basic idea of how it works can be very helpful when trouble shooting.

The function of the capacitor (often called a condenser in the automotive business) is to prolong the life of the points, not to improve the spark. It stops the points from arcing.

From a black box point of view the coil works like this. The voltage induced across the secondary winding is proportional to how fast the current changes in the primary. When the points open the current in the primary drops very rapidly, inducing a large voltage across the secondary. That large voltage makes the spark. The spark comes solely from the energy which has been stored in the coil. The energy in the coil is proportional to the square of the current through the primary just before opening the points.

It is quite correct to discuss the coil in terms of a collapsing magnetic field. That involves more detail about what is happening inside the coil and is more advanced than the black box description given above.

As to whether the capacitor could effectively smooth out the rough power supply, as suggested by Pat, and thus improve things, I have no idea.

my 2c

Steve

 

[RICHARDDV]

http://www.lindsaybks.com/arch/spark/index.html

try this for a buzz box unit. it is a 6 volt model t type coil made from a phelon magneto coil from a tecumseh engine ignition. looks good and also works very well . richard valentine

 

[bearcar1]

A coil is not a storage device of energy, a capacitor is. The only two influences upon a coil that will increase its 'firepower', is either an increase of input voltage on the primary side of the circuit, and/or, by altering the number of winding turns of the secondary side of the device itself. The condenser (capacitor) in the circuit is for reducing any arcing across the points when they transition from closed to open.

BC1
Jim

 

[Brian Rupnow]

Tel--There are many ignition systems out there, and they have some marvelous small electronic packages now. These are however relatively expensive---and if they don't work, there is almost no way to test or repair them. I stuck with an automobile points, condenser, coil, and 12 volt battery because thats what I know. I made my own sparkplug, just to see if I could, and it worked---some of the time. Trouble was, I was never shure if my problems getting my engine to run were caused by my sparkplug, or something else. Thats why I finally bought a "factory made" sparkplug. My theory about building an I.C. engine was that the more "unknowns" that I had to deal with, the less chance I had of getting the engine to run.----Brian

 

[doc1955]

I believe Pat is spot on with his description of the condenser function.

 

[swilliams]

Pat: I largely agree with what you say and don't wish to quibble.

I think you will find that in the Kettering ignition, things are arranged such that all the energy that ends up in the spark comes from the coil. I also think you will find that increasing the capacitance will increase the sustain of the spark, without changing it's energy significantly. The capacitor doesn't speed up the collapse, it slows it down, see http://www.jetav8r.com/Vision/Ignition/CDI.html
Of course these statements are made by ignoring the detrimental effect on the spark due to arcing. It's probably fair to assume that arcing slows the collapse and it certainly reduces the energy going to the spark plug. In this way the capacitor may indirectly speed up the collapse.

Sorry for getting off topic. I sincerely don't wish to quibble, Tel I promise not to pollute your fine thread with anymore inane theoretical nonsense.

Steve

 

[tel]

Thanks for the input everyone, plenty of food for though there while I rummage through my vast collection of junque looking for components.

 

[kustomkb]

Your engine looks fantastic Tel, I hope you get it sorted in short order.

 

[tel]

Thanks Kevin, so do I, but it will be a case of 'hasten slowly' I think, while I get me 'ead around the ignition.

 

[doc1955]

I have confidence in you. I'm sure you'll get it sorted out and going. It is a nice looking piece of work!

 

[Brian Rupnow]

Tel--Here is a helpfull suggestion for you that has nothing to do with ignition points. I found this engine was such a touchy beastie to get running smoothly, that I must have had that damned "Kerzel lever" on and off about a hundred times. That lever is normally held in place by a .094" diameter pin. I took a peice of .125 steel rod about 3" long and turned 3/4" on the end of it down to .094" dia. with a slight angled lead to make insertion easy. The 3/4" is long enough to keep the pin from jumping out of place when the engine does start to run. This way it was very quick and easy to remove the pin and the "Kerzel arm" to get the engine running smoothly in non hit and miss mode. I liked it so much that this morning I took one of my old brass governor balls and threaded it onto the end of the rod as a permanent fixture. Now I can easily run the engine in conventional mode or in "hit and miss" mode. You will also see that I cut that extended "thumb" off the "Kerzel lever"---It served no practical purpose, and I found that the face of the thumb would ride against the cam follower support and create a "feed back drag" on the brass sliding spool. If you don't fully understand that bit, you will when you get your governors functioning.---Brian

 

[Brian Rupnow]

I may be singing to the choir here, as I don't know how much experience you have with i.c. engines, but---a good place to start with the valve timing is to rotate the engine in the direction it would normally run untill its almost at bottom dead center coming off the power stroke. At 15 degrees before bottom dead center, the valve cam-lobe should just be starting to contact the roller bearing that is attached to the end of the push rod assembly. The ignition timing should be set up so that the points open to generate a spark at the sparkplug about 10 degrees before the piston reaches top dead center on the compression stroke. These are "starting points" only, but assuming everything else is kosher, your engine should start and run at those settings.---Brian

 

[tel]

Thanks Brian, I might have to advance the spark a little bit then as I have it 'firing' (or set to) almost right on TDC. Think the exhaust is about right tho'.

I like the idea of the slop oin in the kerzel arm - I'll be doing that for sure.

 

[tel]

OK, just an update. Still held up for some ignition parts - might 'ave to bite the bullet an b.. b.... b... buy some! Meanwhile some more bits n pieces have been added

1. Flyweights - one spring very obviously had a mishap and has to be redone.



2. The bobbin and yoke from the inside



3. Muffler



4. Wasn't real happy with the original oiler I did, with the plastic 'glass', so got hold of some of these 2ml perfume sample bottles



5. And turned one into a bit of oiler



6. New oiler



7. And had a play with decals for the tank



Watch this space.

 

[metalmad]

Hi Tel
looking good now
love the trendy decal ;D
Pete