Valve timing

[peterl95124]

how do you know its not one of the other "usual suspects"
compression (rings and valves sealing) ?
valve timing ?
ignition (getting a hot spark) ?
ignition timing ?
carburation (needle valve, throttle, gas flow) ?

after going through "all the usual suspects" I recently solved a non-starting
problem with some automotive starting fluid (AKA ether), turns out my arm
is no longer strong enough to flip the prop fast enough !

FYI Atkinson Differential engines are notoriously hard to get running, that one's not your fault !!!

 

[Longboy]

Play with valve timing Gordon! Looks like your cam lobes are separate from the shaft and anchored by set screws to it. If so, you can retard the valve timing with the same or tighter overlap between in/ex lobes. This helped my engines from spit back thought the carb with marginal overlap, resulting in easier start-ups as well as late valve timing for low idle speeds.

 

[Sprocket]

Gordon,
For comparison, the Nash setup is
Intake opens 10 degrees after TDC
And closes at 10 after BDC (10-190)
Exhaust opens 40 before BDC and
closes at TDC (140-0)
Spark at 5 degrees before TDC.
So, cylinder 1
Int 10-190
Exh 140-0
Spark 355
Cylinder 2
Int 190-0
Exh 320-180
Spark 175
Probably similar speed range engines.
Hope this helps.
Doug

 

[Gordon]

OK Some things to try. I am thinking that Steve's remarks about needing a higher starting speed may be on point. I am not sure if more or less overlap would make it start at a lower RPM. I have noticed that I seem to come closer to starting at higher RPM but to increase the RPM I need a faster drill motor than I have been using.

The cams are indeed mounted to the shaft with set screws so I have a lot of latitude for changes. I have been using a lost spark ignition and the ignition seems to fire well. I basically used a lot of the design of the Upshur so I may have been too reluctant to make changes on a "proven" design.

 

[gbritnell]

Ok like Steve said here's my 2 cents worth. Everything Steve said I would have said. With all the components of I.C. engine operation correct, compression, fuel/air and ignition timing. then you should be good to go. Here's what I do when starting a new or unknown engine. Close the carb needle valve then open about a quarter to a half turn. Crank the engine over. If there is no response then tap you finger to the carb opening (choke) If everything is good it should try to start and run. If not open the needle a tiny bit more and repeat. At some point the engine should fire and run. My 302 V-8, Flathead Ford V-8 and V-twin are all set for 30 degrees timing. My Holt is about 15 but then again it idles very slowly. Starting off at anywhere from 10-15 degrees should get you in the ballpark.

 

[bluejets]

I have been using a lost spark ignition and the ignition seems to fire well

It may be firing well, (whatever that means) but all I see are two induction fully open at the same time, so your "wasted spark is up the creek without a paddle".
As earlier requested, a photo showing the internal crankshaft thanks.......

 

[minh-thanh]

Hi @Gordon .
Another silly question :
Have you checked the rotation direction of the camshaft and crankshaft?
Setting up the cam lobe will depend on it

 

[Jeffro]

As Bluejets stated, your picture shows both intake valves open at the same time.
I have seen a horizontal opposed twin "2 stroke" outboard firing as a single but wait to see your crank photo.

 

[Richard Hed]

I built an Atkinson differential and could not get that to run for more than about one minute, then I built the Upshur twin and could not get that to run so I tried the upscaled twin and whatever my problem was with the Upshur followed me. In the meantime I built three Perkins for someone else and a Corliss and several other side projects so all of my projects have not been a disaster.

You built a Corliss and you didn't show us? I'm shokt, I'm shokt!

 

[bluejets]

I built an Atkinson differential and could not get that to run for more than about one minute

That's pretty much like chalk and cheese ........Atkinson are difficult to get set up correctly as I have done it successfully.

 

[Gordon]

That's pretty much like chalk and cheese ........Atkinson are difficult to get set up correctly as I have done it successfully.

That is an Atkinson Cycle which is much different than the Atkinson Differential.

 

[Gordon]

FYI: I will not be replying to this for the next few days as I have gotten a new computer which worked for 4 days and then decided to lock me out by going into an endless repair loop so that has become the project of the day. The only way I can reply from the shop is with my Kindle which is clunky at best. I don't know how folks do all of this stuff on their phone.

 

[Richard Hed]

I have a question which I should know the answer to but I am not doing well. I am building a horizontal twin IC engine. My thinking is that the two cylinders should fire 180° apart. I have both cylinder set up for exhaust to open 40° BBDC and close 20° ATDC. Intake open 15° BTDC and close 45° ABDC with the other cylinder 180° after the first. I have good compression but I cannot get the engine to actually run or even fire well. The cylinders get warm but no actual firing. The engine turns over but the two cylinders seem to be fighting each other. The engine actually acts like it is backfiring. I have tried different ignition positions but I am not even close to having the engine running. Any idea what I am missing?

I've been thimpfking about this. It is true that an ICE engine fires once in 720 degrees? That is, in two revolutions of the crank. then You should be setting up your cylinders to fire at either 180 or 540 degs from each other. Is it possible to get it to fire at 360?

 

[GreenTwin]

I was surprised when I was working on my Yamaha 650 twin that the pistons both came up at the same time.

It seemed wrong, but when I thought about it, if a single cylinder fires every other revolution, then having both pistons travel together would allow either one cylinder or the other to fire every revolution, and thus giving two evenly spaced firing impulses around 360 degree revolution.

Not my image.

I do remember the vibration that this engine produced very well, but I would not consider it excessive vibration, and the engine ran like a champ.

.

 

[awake]

I've been thimpfking about this. It is true that an ICE engine fires once in 720 degrees? That is, in two revolutions of the crank. then You should be setting up your cylinders to fire at either 180 or 540 degs from each other. Is it possible to get it to fire at 360?

For a twin in which each piston moves to the top of the cylinder at the same time (one in compression and one in exhaust), the ignition timing would certainly be 360°. As I understand it, if the cylinders are in line, this can lead to greater vibration since all of the mass of the pistons is moving in the same direction at the same time (as in GreenTwin's post above). For a boxer configuration, however, this will result in less vibration, as the pistons are actually moving in opposite directions.

Part of the distinct sound of a "Johnny Popper" (the old two-cylinder John Deere design) was that the side-by-side pistons were set up to move in opposite directions, so the ignition was 180° / 540° apart - thus a "pop - pop - swish - swish" cadence. I read somewhere that this greatly reduced vibration - even though it sounded unbalanced in terms of the pops, it was actually much smoother than it would have been if the pistons had moved in tandem.

 

[bluejets]

That is an Atkinson Cycle which is much different than the Atkinson Differential.

Well if you must hang on small details, yes, but just as difficult to set up.(which, as you can see was successful)...that being the point afterall.
As far as I am aware there are very few, if any, successful "differential" engines that will actually run anyhow (well known).
Pos in that they have crap model design and buggerall compression along with spark plug being located incorrectly.

Photos of the crankcase required are not yet forthcoming so we may have to write to NASA or the FBI and get clearance as it appears to be a big secret.

 

[Richard Hed]

Is that true? about the big secret?

 

[ccolby]

For a twin in which each piston moves to the top of the cylinder at the same time (one in compression and one in exhaust), the ignition timing would certainly be 360°. As I understand it, if the cylinders are in line, this can lead to greater vibration since all of the mass of the pistons is moving in the same direction at the same time (as in GreenTwin's post above). For a boxer configuration, however, this will result in less vibration, as the pistons are actually moving in opposite directions.

Part of the distinct sound of a "Johnny Popper" (the old two-cylinder John Deere design) was that the side-by-side pistons were set up to move in opposite directions, so the ignition was 180° / 540° apart - thus a "pop - pop - swish - swish" cadence. I read somewhere that this greatly reduced vibration - even though it sounded unbalanced in terms of the pops, it was actually much smoother than it would have been if the pistons had moved in tandem.

The down sides of John Deere's famous 180-degree arrangement was "second order" side-to-side shaking of the tractor and that the second cylinder to fire drew it's fresh charge from an intake manifold that was already evacuated by the cylinder ahead of it. Deere finally rectified the second problem with a two-barrel carburetor where each barrel was dedicated to feeding just one cylinder. That eliminated some of the "clut-clut" exhaust noise caused by the "strong-weak" pattern of power strokes.

I have a 7 horsepower Ottawa twin-cylinder (side-by-side) open-crankcase stationary engine that has a 360-degree crankshaft. It runs surprisingly smoothly in spite of its huge reciprocating mass and crude counterbalancing. Its big design plus is its mechanically and electrically simple Wico "PR" magneto that fires both spark-plugs simultaneously. Of course, every other spark on each cylinder is "wasted", just like on any small one-cylinder Otto-cycle engine equipped with a flywheel magneto.

 

[Steamchick]

Different configurations of twins have been around (more or less successfully) since Old testament times, when " the sound of Moses Triumph could be heard throughout the land". Possibly the first record of a Motorcycle, as the Egypt ins have yet to unearth a Heiroglyph carved in stone showing such a machine. (DID you know they did have the first recorded use of steam? To operate the doors to the Temple when the Pharaoh approached, to make it appear to be "Godly magic"?).
Honda, in the 1960s, produced parallel twins (C72, 77, CB72, 77 etc.) where C was a single carb 3 60 degree crank, and CB72 a (necessary) twin- carb 180 degree crank. When using a 180 degree crank, (or as V-twins with 50degree, 75degree, 90 degree, etc. Configurations) it is common practice to have twin fuel and ignition systems. Otherwise the fuelling is really screwed-up as explained by others for the John Dere, etc.
K2

 

[Steamchick]

On the opinion of engines where the stroke of piston performs an intake, compression, combustion and exhaust, without the crank performing 2 revolutions is what we simpletons call a 2-stroke engine, as opposed to a 4- stroke engine where the crank conducts 2 revolutions to complete the cycle. As well as some weird and wonderful designs 100 plus years old (Atkinson & co.), Toyota have been pursuing the 2-stroke holy grail for a few decades.
All things are possible in the imagination....
K2