# John Builds Kerzel Hit & Miss



## simister (Jun 1, 2016)

HI Guys.

Well after all these months after building the Webster, I have finally made a start on the Kerzell Hit & Miss. I have finished the base, which seems to have gone well. Next is the complicated cylinder body.

Brian, I have been following your post on this engine and following the changes in dimensions that you have made. Is there any other variation other than your posts that I should be aware of.

John


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## Brian Rupnow (Jun 2, 2016)

Simister--It`s been a long time since I built the Kerzel. I have it here on a shelf, but I don't really remember what changes I made. If I can help with anything specific I will.--One word of advice though----on all of my hit and miss engines, I used a Viton ring on the piston.-It is quicker and easier, and my cast iron ring making skills really suck!!--But---I never got any of my hit and miss engines to work as good as the other builds I have seen posted. They work, but there is so much drag from the Viton ring that the engine would never coast as long between "hits" as they should have. I never realized how much drag there was, because I never had a good running engine with a cast iron ring to compare it to. After building my most recent two cycle engine with the piston lapped into the cylinder, I was absolutely amazed at how little "drag' there was compared to my engines with Viton rings. I am certain that pistons with a cast iron ring would also have a much lower drag co-efficient. So---I recommend that you use a cast iron ring or lap the piston into the cylinder and don't use any ring.---Brian


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## simister (Jul 23, 2020)

Well, it has been a few years since I started the Kerzel Hit and Miss. However, now that we are in lockdown due to the virus it is a good time to get back into this project.  I have started on the Base Sides. I turned the curved profile by tapping a 8 mm thread in a plate which held the blank. I was then able to put it in the 3 draw chuck.  This seemed to work well.  I had tried doing it in the 4 draw chuck but was not happy with the result. Also, there was very little material for the jaws to lock on to.  Next is the angle cut. I think I will use Brian's method and scribe a line on the face and mill to the line.   John


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## simister (Jul 24, 2020)

Brian, I have seen a lot of your posts on lapping the piston to the bore. What success did you have with it and what method proved the most successful? I have been looking at buying an Acro Lapping tool for the job. However, I am still looking for as much advice as I can get before I go ahead with Acro.

Any help on this would be great.

John


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## Brian Rupnow (Jul 24, 2020)

Having tried many different ways, I finally bought a set of brass laps and use them with 600 grit aluminum oxide paste. Something that works extremely well but is rather dangerous, is to bore the cylinder to nominal size, then use a 3 stone brake hone to take out  most of the machining marks. When making the piston, turn it very carefully to a point where it will just begin to enter the cylinder, but will not slide fully into place. Then put the cylinder into the 3 jaw chuck and have it turning slowly. Coat the piston with diamond paste or 600 grit aluminum oxide. Make a temporary "handle" for the piston, and work it slowly in and out of the bore, going a little deeper each time. This way the piston becomes the lap. THIS IS EXTREMELY DANGEROUS!! You have to be prepared to immediately let go of the piston if it "grabs". It will wrap you up in the lathe in micro-seconds. Sometimes it grabs so tightly that I have to take the cylinder and piston together out to my arbor press and using a piece of wooden broom handle for my "presser" separate the piston and cylinder. If you do this correctly, you won't even need any rings.--- or---You can put the piston into the lathe chuck and hold onto the cylinder with your hands.  If you plan on using Viton rings or cast iron rings, then you can lightly hone and lap the cylinder with an Acro lap and turn the piston to .002" undersize. The rings will expand to take out any possible compression leakage.


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## simister (Jul 25, 2020)

Thanks Brian for sharing that.   OK, did you use the brass laps at all or only used the piston to lap the bore?  I am happy to purchase an Acro Lap if you think that may be a better option. 

I understand that you used Viton rings (I used these in the Webster) in the Kerzel and was not entirely happy with them. Has the running of the Kerzel engine improved over the years  with the Viton rings or would you still prefer to  lap the piston to the bore?  John


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## BaronJ (Jul 25, 2020)

Hi Guys,

A method I've used to lap and polish bores, is to use a piece of wood dowel with a slit in the end and fine emery cloth.  Put the work in the chuck and the dowel in the tool post.  This way you have full control over both the work and the depth of the lapping. 

I've even turned a wood plug and done the same with emery paste on occasion.


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## Brian Rupnow (Jul 25, 2020)

No, the Kerzel has not improved over the years. There is simply too much drag from the Viton ring. Either make it using the dangerous method I outlined and use no ring at all, or use the Acro lap and 600 grit aluminum oxide paste  to smooth out the bore. Then turn the piston for a "sliding fit" into the bore. The piston will be about .002" less than the bore diameter.


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## Misterg (Jul 25, 2020)

simister said:


> I understand that you used Viton rings (I used these in the Webster) in the Kerzel and was not entirely happy with them.



I don't know if you've read this thread:






						O-ring for piston ring
					

Decided to try starting my Jerry Howell Farm Boy.  I used the recommended vinyl o-ring in place of a cast iron ring.  Almost no compression.  Has anyone had success with these o-rings?




					www.homemodelenginemachinist.com
				




It seems Brian advocates a tighter fit for the O ring than some other responses on that thread (0.058" deep groove for a 0.070" section ring = 0.010" / side compression after allowing 0.002" piston-cylinder clearance vs 0.005" / side or even 0.005" total from others). It would be interesting to see if the Kerzel was happier with the lighter contact between ring and cylinder - I hope so, as I'm building a similar engine and have used the 0.005" total compression for the O ring.

It is interesting (to me at least!) that the Farm Boy design has no compression between the O ring and the cylinder at all (it has a 0.110 deep groove for a 0.094 section O ring) yet still seems to run well.


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## simister (Jul 25, 2020)

Thanks Brian,  I will order a .750 Acro lap from the US and use the method you suggested of lapping the bore and machining the piston to fit. I was also going to make the  cylinder and piston in cast.

If I turn the piston to the bore, do I still need to put some grooves in the piston for oil lubrication or leave the piston as is?


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## doc1955 (Jul 25, 2020)

I'd say the best thing is to make the cast iron rings as per plans. But then again I don't like using -O- rings and find that cast iron rings are pretty simple to make. I just finished 2 Kerzels that I posted a build to on my youtube channel. They both run very well and I can hand start them now after running a few times. Anyway thay is my 2 cents worth just make the rings.









						Kerzel build
					

Video on building a Kerzel hit mis engine.




					www.youtube.com


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## Brian Rupnow (Jul 25, 2020)

Look at it this way--One or two oil grooves aren't going to hurt anything, and they won't cost anything.


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## simister (Jul 26, 2020)

Brian Rupnow said:


> Look at it this way--One or two oil grooves aren't going to hurt anything, and they won't cost anything.


Sounds good Brian, I thought it may be beneficial for little effort.


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## simister (Jul 26, 2020)

doc1955 said:


> I'd say the best thing is to make the cast iron rings as per plans. But then again I don't like using -O- rings and find that cast iron rings are pretty simple to make. I just finished 2 Kerzels that I posted a build to on my youtube channel. They both run very well and I can hand start them now after running a few times. Anyway thay is my 2 cents worth just make the rings.
> 
> 
> 
> ...


Thanks for your input, I will have a look at your video on ring making. At this stage I will go for lapping the piston to the cylinder. However, I thought that when I machine the Piston I would cut some rings and have a try anyway. I have a lot to learn in model engineering and trying to keep it simple whilst I gain experience. John


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## simister (Jul 31, 2020)

Finished making the bearing caps today. I should of finished them earlier in the week, however, I got to the last part of the operation and cut on the wrong side.  Frustrating as I had nearly finished them. It was a good lesson as I had been in the shop all day and was getting tired. I should of left it until the next day.


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## simister (Aug 12, 2020)

I am about to start the crankshaft. I notice that some people have made it as per the plans from 1 piece and others made it from multiple pieces.  I notice that Brian made it from 1 piece and also made it up from steel rod. Any suggestions on the best method for this part?

John


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## Brian Rupnow (Aug 12, 2020)

Either way will work fine. One piece crankshafts are scary, because you have to offset them so far to turn the con-rod journal, and that means machining with a rather amazing amount of "stick out" on your turning tool.


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## minh-thanh (Aug 12, 2020)

I made  crankshaft for my first engine from multiple pieces ( and a few more after that ), made of brass, and it had been running for many hours and still not broken.
if you make a steel crankshaft from multiple pieces, it will be very difficult to damage


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## simister (Aug 12, 2020)

Brian, I am leaning towards multiple pieces as it concerns me of getting accuracy from one piece.  How did you avoid distortion when you silver soldered the rods? John


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## simister (Aug 12, 2020)

Minh-thanh,

What method did you use to join the pieces together. I have oxy gear but I am concerned about distorting the shaft.


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## Brian Rupnow (Aug 12, 2020)

Based on experience, I do not recommend silver soldering or brazing the crankshaft. Too much heat distortion. On a built up steel crankshaft, I put a bit of mig weld on both ends of the crank throws to hold them together, then drill and ream them both at the same time so you absolutely know that the holes are aligned. use an "on size" reamer. Cold rolled steel shafting is actually about 0.0005" undersize (drill rod is not). I do not recommend using drill rod. Cut two pieces of cold rolled crankshaft material. One piece is cut to the total length of the crankshaft, and one is cut to the overall dimension outside to outside of the crankthrows. Assemble with loctite #638. Let it set for 24 hours. Then cross-drill and ream .094" in four places and use 3/32" steel cold rolled steel for cross pins. Let set for 24 hours. Next step is very very important---Cut out the bit of shaft between the crank throws. You can hacksaw, band-saw or mill it away.  BE SURE TO CUT THE CORRECT SHAFT.


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## simister (Aug 12, 2020)

OK, what you say makes good sense.  Do you think I could use Bright Mild Steel for the shafts instead of Cold Rolled Steel?


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## Brian Rupnow (Aug 12, 2020)

I'm not sure where you are in the world, but Bright Mild steel is (I think} a United Kingdom designation. I don't know what it's properties are, but I kind of think it is similar to out 01 steel which is drill rod.


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## minh-thanh (Aug 13, 2020)

simister said:


> Minh-thanh,
> 
> What method did you use to join the pieces together. I have oxy gear but I am concerned about distorting the shaft.



*simister !*

With several times I welded the pieces together, I couldn't make an almost straight crankshaft
So, I solve the problem:
when I need a 10mm diameter crankshaft, I will make an 11 mm shaft ( I just need exact tolerances around the  crank - the rest of the shaft I normally make the diameter smaller - which makes it easier to bring the crank into the shaft )
, then assemble it all together and fix them with pins, then I solder the silver.
Then I mounted the crankshaft on the lathe and turned out on both sides to 10 mm
then cut the bit of shaft between the crank


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## simister (Aug 13, 2020)

Ok, thanks Brian. I have decided to go with the multiple piece crankshaft.


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## simister (Aug 13, 2020)

minh-thanh,   that sounds like a good idea. However, I am going to go with the multiple piece crankshaft and see how that goes.  I have already ordered the cold rolled steel.  thanks John


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## simister (Aug 13, 2020)

I have finished the main bearings in sintered bronze and the cylinder liner.  All I have to do now is lap the cylinder to size. The Acro Laps arrived today so I can get started on that.  The main bearings need to be machined to a fine finish but I will do that when I have finished the crankshaft and ready to assemble. 

The cylinder liner is a tight fit but I can slide it in and out without much effort.


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## johwen (Aug 13, 2020)

simister said:


> I am about to start the crankshaft. I notice that some people have made it as per the plans from 1 piece and others made it from multiple pieces.  I notice that Brian made it from 1 piece and also made it up from steel rod. Any suggestions on the best method for this part?
> 
> John


Johwen here I have made many shafts using both methods Machining from the solid one piece is tricky as distortion is usually the problem and can be slow in machining compared with a built up shaft. For single cylinder long stroke engines I use the built up shaft method. Machine the two crank plates locktite together drill and ream the crank pin and main shaft holes, separate the plates and locate them on the full length main shaft and place the crank pin cut to correct over all length. You need a good flat surface to avoid any slight twist. When you are happy with this separate and clean all joints and use locktite 620 High strength. Leave set for a couple of hours and the drill through each joint and ream with a tapered reamer to a set depth and press in a tapered pin with some locktite and when set machine of the extra length leave for twenty four hours and then mill, saw and file the piece of main shat away and you now have a strait and true crankshaft.  I've never had one fail nor any alignment problems using this method and is very time saving. On larger engines I have lightened the big end by drilling it and you can use a harder material. You can also do all your drilling before assembly of the big end an then case harden sme then locktite pin and assemble your big end. Hope this gives you some ideas that have worked for me John.


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## L98fiero (Aug 13, 2020)

Brian Rupnow said:


> Cold rolled steel shafting is actually about 0.0005" undersize (drill rod is not).


Based on 40 years of machining, cold rolled steel _may_ be .0005 undersize or not but it also may not be round either, depending on how the draw dies wore. Take the piece you want to use and indicate it as you roll it in a vee block, you might be surprised how far out of round they are.  Ryerson in Canada lists tolerances of -.002 up to 1.625 diameter and KV Steel in  the UK says -.07mm to 18mm diameter. Experience has shown it's usually closer to -.0005 but I'd check before making an assumption on size.

According to the Atlas Steel (Australia) site "Bright steel bar is usually a carbon steel alloy which has had the surface condition improved by drawing, peeling or grinding over the hot rolled finish supplied by the steel mill." I think our "drill rod" is their "silver steel" or it used to be in the old Model Engineer magazines that got me into the hobby.


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## awake (Aug 13, 2020)

Brian Rupnow said:


> I'm not sure where you are in the world, but Bright Mild steel is (I think} a United Kingdom designation. I don't know what it's properties are, but I kind of think it is similar to out 01 steel which is drill rod.



Hmm, I wouldn't think anything labeled "mild steel" is likely to be a high-carbon steel - ?? I'd guess "Bright Mild steel" is equivalent to our "cold rolled steel" - bright as opposed to the dark color of hot-rolled steel.


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## simister (Aug 13, 2020)

John,

Thanks for your help. Yes, that is basically the method I will use to make the crankshaft. Brian, has also used a similar method. I was originally going to make it as per the Kerzel plans but I was concerned of trying to keep it true on the lathe. Making the crankshaft by not silver soldering thereby "no heat distortion" seems to be the way to go.  John


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## simister (Aug 16, 2020)

I have just finished machining the piston for a slide fit into the cylinder liner.  I had originally intended to use Viton rings of which I have now received.  

The piston is still in the lathe ready for the grooves to be cut for the Viton rings.  However, the slide fit of the cylinder onto to piston seems to have compression without rings. If I slide the cylinder liner onto the piston - block the other end, then pull the cylinder liner off quickly it "pops" from the suction.  

I am not sure if the compression that is there without any rings,  is sufficient to not go ahead with the grooves for the Viton rings. I understand if the compression is good enough then I am better without any rings for this hit and miss engine. 

My question is: should I still go ahead and cut the grooves for the Viton rings just in case it does not have sufficient compression or would that compromise the piston if it is grooved without any rings?

John


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## xpylonracer (Aug 16, 2020)

With such a close fitting piston you may find with heat from running it expands and seizes in the bore, I would add the grooves whilst set up in the lathe.

xpylonracer


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## Brian Rupnow (Aug 16, 2020)

If you have that good a fit, then don't use rings. This is a "try it and see" world. If it doesn't have enough compression to run, then add the groove and the ring later.


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## simister (Aug 16, 2020)

OK, thanks for the advice. I will try first and see how it goes.


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## L98fiero (Aug 16, 2020)

Brian Rupnow said:


> If you have that good a fit, then don't use rings. This is a "try it and see" world. If it doesn't have enough compression to run, then add the groove and the ring later.


I'm not speaking from experience, just asking, if you have a good fit anyway, would the grooves not act as a labyrinth seal and be of benefit even if there are no rings installed?


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## Brian Rupnow (Aug 17, 2020)

The grooves, as originally shown on the drawings, are oil retention grooves. The engine using a piston like this must have an external oiler fitted to the cylinder which drips oil directly into the cylinder. The grooves in the piston pick this oil up, and distributes it along the i.d. of the cylinder. It helps the piston to hold compression and lubricates the piston and cylinder.


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## simister (Aug 17, 2020)

With regards to the Wrist Pin for piston. What is meant by Teflon end caps?

John


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## Sprocket (Aug 17, 2020)

Like this but in Teflon.
If I remember correctly, this one is 3/16" diameter. The end caps are "t" shaped, or I should say, have a small peg in the middle which goes into a hole in the wrist pin.

Doug


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## simister (Aug 17, 2020)

OK,  What type of supplier sells Teflon caps?


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## Sprocket (Aug 17, 2020)

simister said:


> OK,  What type of supplier sells Teflon caps?


You could probably substitute brass or some other plastic. You make the caps. Probably could get Teflon rod from a plastic supplier or maybe McMaster-Carr. 
Doug


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## simister (Aug 18, 2020)

OK, that's fine, thanks Doug,

John


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## doc1955 (Aug 18, 2020)

Just turn up some plugs they don't need to be pressed on. They are there to keep wrist pin in place and keep wrist pin from making contact with cylinder wall. Usingwrist pin plugs is  so you don't need any other means of keeping them in place. Just put a small plug on both sides and no need to drill hole through wrist pin.


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## simister (Aug 18, 2020)

doc1955 said:


> Just turn up some plugs they don't need to be pressed on. They are there to keep wrist pin in place and keep wrist pin from making contact with cylinder wall. Usingwrist pin plugs is  so you don't need any other means of keeping them in place. Just put a small plug on both sides and no need to drill hole through wrist pin.



Ok, that makes sense - thanks,

John


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## simister (Sep 20, 2020)

Brian,
I notice that you used a similar setup with the contact points as the Webster.  I am thinking of doing the same thing and wondered if you found any problems with the change from the original plans?

Also, I am having trouble getting the Chrysler contact points that I used with the Webster. Do you see any issue with using any other contact points that can be obtained locally? Of course, I understand that the bracketing would need to suit.

John


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## Brian Rupnow (Sep 23, 2020)

Use any points that you can get. Also get a 12 volt condenser to go with the points.


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## simister (Sep 24, 2020)

Thanks Brian,


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## a41capt (Sep 24, 2020)

Brian Rupnow said:


> Use any points that you can get. Also get a 12 volt condenser to go with the points.


Brian, and any other knowledgeable folks, I was gifted a brand new 6 volt automotive coil, but I’m going to run my newest Engine (a Webster) on 12 volts. Does anyone have an opinion on running 12v through a new 6v coil?  I’d rather not see the magic smoke appear!

thanks in advance,
John


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## BaronJ (Sep 24, 2020)

a41capt said:


> Brian, and any other knowledgeable folks, I was gifted a brand new 6 volt automotive coil, but I’m going to run my newest Engine (a Webster) on 12 volts. Does anyone have an opinion on running 12v through a new 6v coil?  I’d rather not see the magic smoke appear!
> 
> thanks in advance,
> John



No you don't want to put much more than about 7.5 volts into a 6 volt coil.  You have two options, well maybe three,  use a resistor in series or use a voltage regulator to get your 6 volts.  If you can get at the half voltage point of a 12 volt battery that would work as well. As far as the condenser across the points is concerned the voltage isn't too important as long as its greater than what ever voltage you are supplying the coil.  A 0.1 uf at 100 v will work and should only cost pennies !

A visit to a car scrap yard will get you a suitable coil, though you may have to take it off the car yourself.


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## doc1955 (Sep 24, 2020)

Put together a voltage divider. you only need 1k,1.5k and a 4k resistor to divide the voltage to 6.25v


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## BaronJ (Sep 25, 2020)

doc1955 said:


> Put together a voltage divider. you only need 1k,1.5k and a 4k resistor to divide the voltage to 6.25v



Unfortunately doing it this way you wont have enough current to drive a conventional coil !


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## Jules (Sep 25, 2020)

doc1955 said:


> Put together a voltage divider. you only need 1k,1.5k and a 4k resistor to divide the voltage to 6.25v


You would need to measure the current when running on 6v and then calculate the value and power requirement of a series resistor. 

R=V/I


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## a41capt (Sep 25, 2020)

Thanks for all the info guys!  I don’t want to hijack this very excellent thread any longer, so I’ll take your input and experiment.

John


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## Steamchick (Sep 26, 2020)

Because of the current demand from ignition coil (much more than 4A. Rms... The peak current can be 3 times that!), I suggest 2 x 6V batteries in series for the 12 V. DC Supply.  Lead-acid sealed batteries for alarm systems are small and can hande the current delivery for good sparks. Then tap-off 6V for the ignition system from 1 battery. Possibly cheaper than a resistive voltage divider that can handle 4A rms?
Or get a 12V motorcycle coil...? 
K


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## Steamchick (Sep 26, 2020)

Because of the current demand from ignition coil (much more than 4A. Rms... The peak current can be 3 times that!), I suggest 2 x 6V batteries in series for the 12 V. DC Supply.  Lead-acid sealed batteries for alarm systems are small and can hande the current delivery for good sparks. Then tap-off 6V for the ignition system from 1 battery. Possibly cheaper than a resistive voltage divider that can handle 4A rms?
Or get a 12V motorcycle coil...? 
K


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## Steamchick (Sep 26, 2020)

Because of the current demand from ignition coil (much more than 4A. Rms... The peak current can be 3 times that!), I suggest 2 x 6V batteries in series for the 12 V. DC Supply.  Lead-acid sealed batteries for alarm systems are small and can hande the current delivery for good sparks. Then tap-off 6V for the ignition system from 1 battery. Possibly cheaper than a resistive voltage divider that can handle 4A rms?
Or get a 12V motorcycle coil...? 
K


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## Steamchick (Sep 26, 2020)

Because of the current demand from ignition coil (much more than 4A. Rms... The peak current can be 3 times that!), I suggest 2 x 6V batteries in series for the 12 V. DC Supply.  Lead-acid sealed batteries for alarm systems are small and can hande the current delivery for good sparks. Then tap-off 6V for the ignition system from 1 battery. Possibly cheaper than a resistive voltage divider that can handle 4A rms?
Or get a 12V motorcycle coil...? 
K


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## doc1955 (Sep 26, 2020)

I use a coil pack from an auto and run on 6v with no problem. I use a resistor to bring the resistance to around 2 ohms and run with a hall with ignition boards that I made. You can also use a tm6 board as long as you use a ballist to bring the resistance to around 2ohms.  I've ran it on current as low as 4v without an issue (on hit miss engines).


PS on some of my engines I put a plugin and use a USB charger (wall wart) for power.


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## Steamchick (Sep 26, 2020)

Hi doc1955: Just curiosity.... (I worked on engine design for a car manufacturer) what plug-gap are you working with? - What compression ratio is there on your engine? - Of course, I was thinking of typically 10:1 compression with plug gaps of 0.025 ~ 0.040 inch. But maybe you simply don't have that much compression on the models, nor full sized plugs with such large gaps?
Hence you'll manage with lower voltages and the current will be lower as well. - My smallest engine experience is with 50cc Honda engines at around 9:1. Using 0.5mm spark plug gap.
Cheers!
Ken


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## Steamchick (Sep 26, 2020)

A41capt: Is that a James Captain in your photo? - I guess that's why you have a 6V coil?
K


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## Steamchick (Sep 26, 2020)

NOTE: The piston pin end-caps need to be DOMED the same radius as half the bore diameter. - It was common practice 60 or more years ago with racing 2-strokes (Villiers engines, BSA Bantam engines, etc.) - to eliminate circlip breakage (By eliminating the circlips).
K


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## doc1955 (Sep 26, 2020)

Steamchick said:


> Hi doc1955: Just curiosity.... (I worked on engine design for a car manufacturer) what plug-gap are you working with? - What compression ratio is there on your engine? - Of course, I was thinking of typically 10:1 compression with plug gaps of 0.025 ~ 0.040 inch. But maybe you simply don't have that much compression on the models, nor full sized plugs with such large gaps?
> Hence you'll manage with lower voltages and the current will be lower as well. - My smallest engine experience is with 50cc Honda engines at around 9:1. Using 0.5mm spark plug gap.
> Cheers!
> Ken


Motors have pretty decent compression never checked any or know what they are I run a .020 plug gap on a home made plug and also have run the same on I think a cm-6.


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