Horizontal Air Cooled Engine

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johwen

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Well Brian, The area I differ with you is in the heat treatment and I put two ring in each groove that are half the thickness of the ring groove less the appropriate clearances gaps are 180 degrees apart. They are encased in an outer sleeve and brought up to red hot temperature for around 15 minutes then let to cool naturally and when opened the treatment jig is opened up I only have the dress the width on an flat service plate to suit the groove. The rings have full tension I've never had a failure for sealing. They only need washing in kerosene after adjusting the thickness as the sealing surface comes out basically dark blue with no oxidation
Being an Auto engineer back in the 50-70's re ringing 4 cylinder car engine was a weekly occurrence many with tapered worn bores .005" out of round they still sealed. Today modern car engines the piston relies the ring to do all the sealing via the ring grooves as their is very little skirt on the gudgeon pin axis. When reboring cylinders the piston back in those days had full skirts and were ground oval to give more clearance on the gudgeon axis to prevent seizure.
John
 
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Brian Rupnow

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After more trials and tribulations than you want to hear about, this is my 7/8" horizontal engine running with cast iron rings. This was much more of a struggle than I anticipated, but the fault was mostly that the grub screws holding the bottom timing gear had slipped enough that the engine was out of "correct valve timing". To me, this is wonderful. This is the first 7/8" bore engine that I have installed cast iron rings in. In this video my engine is running on Coleman fuel.---Brian
 

awake

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Congrats, Brian!

I'm pretty sure I remember a previous engine that you struggled with, only to find that a timing gear or cam had slipped. With that in mind, it might be worth designing your next engine with the timing secured by a key. You could still make the valve timing variable, by having the timing gear on a boss; the gear could adjust on the boss, and the boss is keyed to the shaft.

Just thinking aloud ... and shouldn't be, since you have made, what, 187 running engines now? I'll go see if my grandmother would like to suck eggs ...
 

Brian Rupnow

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Awake--it's a nice thought---but---if the boss was keyed to the shaft, then the gear would slip on the boss. Setting and maintaining valve timing is a very delicate thing---and it's not really visible to the naked eye.
 

awake

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I was thinking of the sort of variable timing gear arrangement that is found in some high-end cars. "Boss" is not the right term ... gear carrier, maybe? Where the gear has slotted holes through which it bolts into the carrier.
 

awake

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Yes, a couple. This is something I have thought about doing on the next one. But see my disclaimer above - I realize I am coming from a place of great relative ignorance!

In my defense, this is not my idea; I have seen it somewhere in this forum. If I could point to the post, I would, since I am no doubt doing a poor job of describing it.

Also, FWIW, the engines I have built have the timing gear and cams keyed to the camshaft. That of course means that the keying has to be correct ... or else one has to have a way to adjust the rotation of the gear with respect to the key.
 

Brian Rupnow

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Engines are simple to build, but a tricky thing to set up and run. Most of the things that have to be "set up" are right there in your face, and it's hard to overlook them. Some of the things (like valve timing) are not really visible, and require a timing disc to really see whether it's right or not. My question wasn't a "put down". I do get a lot of "why didn't you do it this way?" from people who have never built an engine in their life. A lot of what I do is something that you have to have successfully done yourself, to even understand what is going on. No harm--No foul.---Brian
 

awake

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No harm--No foul.---Brian

Agreed - I took it as an honest question. No problem.

require a timing disc to really see whether it's right or not

This is the point of potential disagreement. I have seen in many of your write ups that you use a timing disc to set the valve timing - which depends, of course, on being able to adjust the cams. I would suggest that it is possible to "hard code" the valve timing by locking together the relationship of the camshaft, cams, and timing gear via keys. If adjustment is still needed, the idea that I tried to describe above would provide the ability to make small adjustments; move a gear tooth to make large adjustments.

BUT - this is the point at which Brian's question is most pertinent. I can suggest that this is possible all day long. But I have not yet built one that works exactly that way. I have locked timing gear and exhaust cam together via keys (in an atmospheric intake valve engine), so the suggestion is partially demonstrated, but not yet the full scope of setting up both cams and getting everything right. That is a work in progress ... we shall see!
 

Gordon

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I think that a problem many new model engine builders have is comparing it to their experience with large engines. An adjustment on a full size engine may translate into a .001 adjustment on a model engine. Sheer mass and power may overcome some misalignment or friction in a V8 but will prevent a small engine from running.
 

minh-thanh

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I think that a problem many new model engine builders have is comparing it to their experience with large engines. An adjustment on a full size engine may translate into a .001 adjustment on a model engine. Sheer mass and power may overcome some misalignment or friction in a V8 but will prevent a small engine from running.
I usually adjust all my engines the way my dad taught me when he works with a big engine and it always runs.
 

Gordon

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I usually adjust all my engines the way my dad taught me when he works with a big engine and it always runs.
You have better luck than I do then. I used to be able to tune a car by turning the distributor until it sounded right and adjust the carburetor until it sounded right. On model engines I have had engines which would not run with timing +/- 2° or needle valve 1/32 turn off.
 

Brian Rupnow

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Minh-thanh---I am happy for you that your engines always run. Mine do too---eventually. The key word there is eventually. I spent a lifetime building and racing hot-rods with big V8 engines in them, and it was much easier to get them to run than these small single cylinder engines.
 

minh-thanh

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Gordon !
I think, With big engine: + / - 2 degrees will affect the performance....which we need.
With small engine - homemade : + / - 2 degrees does not have much effect on whether it runs or not .
 

Brian Rupnow

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Today I'm going to call this engine "finished". It is doing everything I set out to accomplish, and is running with cast iron rings. There is a bit of a write up with the video. Thank you all for watching the build and for the helpful hints and suggestions. ---Brian
 

Brian Rupnow

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Andy--Your idea of having the relationship between the two cams "fixed" and the cams "fixed" in some rotational relationship to the cam gear is not a bad suggestion. If a person always uses the same cam (which I do) then it does make sense. I have almost always pinned my exhaust cam to the camshaft, but left the cam shaft to cam gear adjustable. The intake cam is not "fixed" to the camshaft. It is positioned rotationally by grub screws. What this gives me is infinite adjustability for both the intake and exhaust cams. However, it does introduce more chance of something get out of adjustment. Minh tranh--a V8 auto engine has 4 cylinders firing each revolution. A single cylinder engine has one power pulse every second revolution. On a v8 engine these other power pulses during one revolution provides enough impetus to keep the engine running even if the timing is off a bit. On a single cylinder engine, which only fires once every second stroke, if the timing is not perfectly correct, then the engine runs down and stalls before it gets to the next power pulse.
 

minh-thanh

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Brian Rupnow !
Minh tranh--a V8 auto engine has 4 cylinders firing each revolution. A single cylinder engine has one power pulse every second revolution. On a v8 engine these other power pulses during one revolution provides enough impetus to keep the engine running even if the timing is off a bit. On a single cylinder engine, which only fires once every second stroke, if the timing is not perfectly correct, then the engine runs down and stalls before it gets to the next power pulse.

Yes, you are right!
So when I do my small engines I usually try to make everything smooth : crankshaft - bearing, camshaft - bearing, gears - gears....
And when I assemble, I check each part to make sure everything is smooth and they are smooth with the others.
The engine is assembled (no spark plugs installed): I have to be able to turn the flywheel by hand with light force - For V4 or I4, for 1 cylinder the force is lighter (with engines more than 4 cylinders I don't know. because I haven't done it yet)
When the engine is assembled with spark plugs : The engine must have good compression
And lastly : Adjust the timing and the amount of fuel (adjusting the amount of fuel seems to be the hardest part for me )
With me: not smooth and friction is a factor that will destroy all efforts to have the engine run and it will contribute to incorrect ignition timing, cam timing...
 

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