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2 and 4 Stroke

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jhauck(at)elmore.rr.com
Guest

Posted: Tue Jan 03, 2006 7:53 pm Post subject: 2 and 4 Stroke



Hi Gang:

Been a lot of discussion about 2 and 4 stroke engines for our little

airplanes.

I had the opportunity to build and fly three 2 stroke powered Kolbs,

and am still flying the third one, but not with 2 stroke any more.

Did some serious cross country flying with a 447 point ign engine and

an original Firestar. Had a ball doing them all. Had some

disappointments, but survived them. Like an engine failure over the

Niagara River, just north of Buffalo, NY. Broke the airplane in the

process of getting me back on the ground. Got it repaired in about 4

days and flew a very bent FS back to Alabama. That engine out and

bent airplane was the decision point to rebuild the FS to do serious

cross country flying a little better than the first time around. BTW

the engine failure was caused by the NGK fine wire plugs I was using.

One of them let go of the tiny center electrode which lodged between

the ground strap and the base of the spark plug, effectively shutting

it down. Won't fly on one cylinder.

Don't ask me how I got off on that tangent, but what I wanted to share

was a very short description of what I see as the major difference

between the 2 and 4 stroke light aircraft engines. Primarily,

lubrication. The 4 stroke uses a dedicated, precision type, pressure

lube system. The 2 stroke uses a fuel/oil/air mix that relies on air

flow and chance to get things lubricated correctly.

As far as reliability is concerned, the area the 4 stroke is hands

down over the 2 stroke is piston to cylinder wall lubrication. Here

the 2 stroke does a good job as long as that microscopic film of oil

is kept in place between the piston and cylinder wall metal. If, at

anytime, it is broken, just a little bit, the piston is going to scuff

and probably seize in the cylinder. We don't have that problem with

the 4 stroke unless we loose oil pressure, and then the crank and rod

bearings are going to go first.

There are a lot of ways to break the oil film in a 2 stroke:

1-broken ring

2-stuck ring and a little blow by

3-produces a lot of carbon that might have a bearing on creating a

break in the oil film

4-acts of God

5-unnatural, mysterious, unexplainable acts

Can't think of any more at this time, but maybe you all can.

Correct me if I am wrong, but I don't know of any problems we have

suffered with the 4 stroke Rotax in the area of piston and cylinder

scuffing and seizing. In fact, the factory tolerance for piston to

cylinder wall clearance when new is 0.000 to 0.001". Not a whole lot

of clearance. However, another advantage of the 912 is the use of

plated aluminum cylinders and not cast iron or steel sleeves as used

in the 2 strokes.

Not looking for arguments. Thinking out loud tonight and wanted to

share my thoughts.

Most engine failures are operator induced on both 2 and 4 stroke

engines. I believe the critical difference is the all important oil

film on the cylinder wall.

john h

mkIII

hauck's holler, alabama

jlbaker(at)telepath.com
Guest

Posted: Tue Jan 03, 2006 8:55 pm Post subject: 2 and 4 Stroke



 	  Quote: 	
		  However, another advantage of the 912 is the use of

plated aluminum cylinders and not cast iron or steel sleeves as

used 	


 	  Quote: 	
		   in the 2 strokes.

	


Aaaakkkk! Heresy! My Hirth has the same Nikasil as your 912. So

there!

; )

Jim Baker

580.788.2779

'71 SV, 492TC

Elmore City, OK

jhauck(at)elmore.rr.com
Guest

Posted: Tue Jan 03, 2006 9:13 pm Post subject: 2 and 4 Stroke



| Aaaakkkk! Heresy! My Hirth has the same Nikasil as your 912. So

| there!

|

| ; )

|

|

| Jim Baker

Sorry Jim:

Was talking about Rotax (or is it Rotaxen?) Should have spelled that

out in my original post.

Rotax calls it something else, and my Suzuki DRZ400E 4 stroke thumper

calls it something else again, and Yamaha thumpers call their plating

something difference. Amazing technology. There is a plant in

Auburn, Alabama, that will replate a single cylinder for about

$150.00. When they finish with it, it is ready to go back together.

Send the new piston along with the cylinder so they can hone it to

specs. Will be a new cylinder no matter how bad you screw it up.

I imagine your Hirth still survives as long as that microscopic film

of oil is in place between piston and cylinder.

john h

Titus, Alabama

link(at)cdc.net
Guest

Posted: Tue Jan 03, 2006 10:56 pm Post subject: 2 and 4 Stroke



Gentlemen,

This has been the most interesting post session of the year. I guess I

have been very interested in this very subject. I have a pressure

washing business and use these little industrial engines and from what I

have seen would have no problem putting one behind me as a power plant.

I have used the briggs 18hp L-head engines at close to maximum power and

regularly get 3000 plus hours of service out of them. I have not used

the v-twins yet but plan on replacing both of my engines with them soon.

The question that I have is if you can get the engine to run slow enough

to run the prop with out a reduction drive. I truly believe that These

engines will bring about a new chapter in ultralight aircraft. I Thank

Don and all who have contributed to this post .

Steve Garvelink

lstavenhagen(at)hotmail.c
Guest

Posted: Wed Jan 04, 2006 5:10 am Post subject: 2 and 4 Stroke



 	  Quote: 	
		  As far as reliability is concerned, the area the 4 stroke is hands

down over the 2 stroke is piston to cylinder wall lubrication. Here

the 2 stroke does a good job as long as that microscopic film of oil

is kept in place between the piston and cylinder wall metal. If, at

anytime, it is broken, just a little bit, the piston is going to scuff

and probably seize in the cylinder. We don't have that problem with

the 4 stroke unless we loose oil pressure, and then the crank and rod

bearings are going to go first.

	


I'm not arguing either, but I do have an observation. I think the 2 and 4

stroke both have the same constraint here. I don't see this as a significant

difference between the two designs. 4-strokes also depend on a film of oil

keeping the piston and cylinder apart and if the film breaks down the

results are similar.

For example, one way the film of oil can be broken down on the 4-stroke is

excessively rich running. Too much raw gas in the cylinder can wash the oil

film away leading to piston/cylinder contact with the you-know-what result.

Don't ask me how I know this...

The main operative difference when it comes to the piston/cylinder

reliablity issue is probably thermal shocking and not lubrication. The

4-stroke has it all over the 2-stroke here. Because the 2-stroke fires on

every stroke, heat buildup is much more intense and rapid. Also, for

durability reasons, a steel liner is used in the Rotaxen - very very tough

and long wearing design, but susceptible to thermal shocking especially due

to it being a 2-stroke. A long period of idling followed by sudden sustained

full-throttle is a recipe for disaster in the 2-stroke (especially the water

cooled motors). The piston heats up much faster than the liner and expands

faster as well. In extreme cases, siezure is the result as the

piston/cylinder gap closes. Don't ask me how I know this either.

This is much less of a problem with the 4-stroke. The piston heats up a

somewhat less rapidly there, due to the extra intake/compression stroke

which helps slow down the heating of the piston. Generally, then, you can

hammer away with the throttle on a 4-stroke with much less danger of

siezure.

And yes the aluminum/nickasil liners also help with this since they tend to

expand at closer to the same rate as the piston.

If there is one single reason I would ever switch to a 4-stroke, this would

have to be it. They're so much more durable regarding thermal shocking than

the 2-stroke it's not even funny.

Then of course there's the fact that the 912 has a TBO 4x longer than the

2-stroke rotax and is just much beefier in general for the power output,

etc.....

All I need now is just to win the lottery and I can get my kolbra and 912

.....

Anyway, just my thoughts while drinking my morning coffee.....

LS

N646F

jrjungjr(at)yahoo.com
Guest

Posted: Wed Jan 04, 2006 5:34 am Post subject: 2 and 4 Stroke



Group,

All this talk about a 35 hp Vanguard engine, with the torque of a 503

got my attention. So, I Googled it. It weighs 153 pounds.

Source: http://www.commercialpower.com/display/router.asp?docid=78080

John Jung

Firestar II N6163J

Surprise, AZ

slyck(at)frontiernet.net
Guest

Posted: Wed Jan 04, 2006 6:04 am Post subject: 2 and 4 Stroke

Ack! 153 lbs? that's more than my suzuki G10. Now I will admit that it IS physically more bulky than a rotax 2 stroke but after fuel load considerations you aren't talking more weight. There are both a gear type and cog belt drive with good reps available. What is the reluctance to use them, other than the undeniably excellent 912 series? The brain cell taxing labor? Skill isn't a big factor. -BB, 4 stroke suzie, about $3000 invested including total overhaul and redrive. do not archive On 4, Jan 2006, at 8:34 AM, John Jung wrote: Group, All this talk about a 35 hp Vanguard engine, with the torque of a 503 got my attention. So, I Googled it. It weighs 153 pounds. Source: http://www.commercialpower.com/display/router.asp?docid=78080 John Jung Firestar II N6163J Surprise, AZ

donghe(at)one-eleven.net
Guest

Posted: Wed Jan 04, 2006 6:40 am Post subject: 2 and 4 Stroke



John,

The Liquid cooled 35 is a real brute...but a tad heavy I think. It has a

double wide clevite bearing on the PTO end of the crank..makes it look like

a lycoming crankshaft.

Anyway...they have an aircooled 35 also...same size...just under 1 litre but

28 lbs less at 125...of which alot is a hugh commercial aircleaner.

another thing I might add,..is the 25 horse engines out there have the

torque of a 503....the 31/33/35 class of engines is a whole lot more, no

matter who the nmanufacturer...

Take the Vanguard 35 aircooled at 52.2 ft lbs torque vs the 582 blue head at

51 ft lbs

and you have a closer comparison

The Vanguard LC 35 is rated at 55 ft lbs...now we are gonna run these thru a

reduction unit and get the speed down to ...say 2500....lets see...1.44 to 1

ratio...what is the torque now?....(where's Topher when ya need him!)

anyway...you fellas see what I mean..these thoughts have been working on me

for awhile..I certainly dont know for sure just how it would be..but the

numbers sure seem favorable.

Some of you know , or remember a year or 2 ago I was fooling around with a

24 hp vtwin and a 60 inch ivo 3 blade. I was able to turn the ivo at a hub

speed of 2200, pitched at the same degree that it was on my cuyuna. At 2200

hub speed..the firefly would run 60 mph.

now..how can that be?...Cuyuna ULII-02 rated at 38 hp and the Vtwin rated at

24hp...both close performance when bolted to a reduction drive with a prop

for the load?....pretty obvious that the torque was about the same.

....just some thinkin as I am competeing to drain the coffee pot this morn!

http://www.commercialpower.com/display/router.asp?docid=78069

Don Gherardini

OEM.Sales / Engineering dept.

American Honda Engines

Power Equipment Company

CortLand, Illinois

800-626-7326

jhauck(at)elmore.rr.com
Guest

Posted: Wed Jan 04, 2006 6:41 am Post subject: 2 and 4 Stroke



| The main operative difference when it comes to the piston/cylinder

| reliablity issue is probably thermal shocking and not lubrication.

Lucien, are you sure lubrication is not an issue??? 

|Generally, then, you can

| hammer away with the throttle on a 4-stroke with much less danger of

| siezure.

Not in the "real world". Try it in an old Continental or Lycoming

aircraft engine. ;-(

| And yes the aluminum/nickasil liners also help with this since they

tend to

| expand at closer to the same rate as the piston.

Not actually a liner, but a coating. Aluminum coated cyls and pistons

expand at the same rate, thus the "zero to 0.001" clearance on 912

engines.

| Then of course there's the fact that the 912 has a TBO 4x longer

than the

| 2-stroke rotax and is just much beefier in general for the power

output,

| etc.....

Not necessarily "beefier" but a better proven design.

john h

DO NOT ARCHIVE

lstavenhagen(at)hotmail.c
Guest

Posted: Wed Jan 04, 2006 7:03 am Post subject: 2 and 4 Stroke



 	  Quote: 	
		   | The main operative difference when it comes to the piston/cylinder

| reliablity issue is probably thermal shocking and not lubrication.

Lucien, are you sure lubrication is not an issue??? 

	


It doesn't seem to be, no. Thermal shock is far and away the more prevalent

cause of scuffing and siezure in the 2-strokes I've run or seen run to

destruction than any design problem with cylinder wall lubrication. The

basic principle is the same in both motor types, though the source of the

oil is different in each case.

When not thermal shocked leading to seizure, 2-stroke piston/cylinder

lubrication appears to work pretty well. The liners actually wear very

little; frequently new pistons can be put in liners at 400 some odd hours

and the clearances obtained are close to new limits...

Putting it another way, 2-strokes tend to blow up and rot away from

neglect/abuse much more than they actually simply wear out through normal

operation.

Don't ask me why I know this....

 	  Quote: 	
		  Not in the "real world". Try it in an old Continental or Lycoming

aircraft engine. ;-(

	


I did for a number of years - the Continentals and Lycomings I learned

behind and rented took FAR more throttle abuse that I would ever dare to

attempt to put over on my 2-strokes, with nary a problem. To my knowledge,

all those motors ran right out to TBO......

Those motors are much more durable regarding thermal shocking than even the

air cooled 2-strokes, trust me .

 	  Quote: 	
		  Not actually a liner, but a coating. Aluminum coated cyls and pistons

expand at the same rate, thus the "zero to 0.001" clearance on 912

engines.

	


You're right - tnx for the correction....

 	  Quote: 	
		  Not necessarily "beefier" but a better proven design.

	


Well, for example, take a 582 crank and set it beside a 912 crank. The delta

in terms of power output asked of them is only about 15 hp, but the

difference in size and strength is pretty substantial.......... That's what

I mean by beefy....

And yes it is a better proven design, IMO, probably the best 4-stroke on the

market.....

LS

N646F

do not archive

 	  Quote: 	
		  john h

DO NOT ARCHIVE

tophera(at)centurytel.net
Guest

Posted: Wed Jan 04, 2006 8:28 am Post subject: 2 and 4 Stroke



The Vanguard LC 35 is rated at 55 ft lbs...now we are gonna run these thru a

reduction unit and get the speed down to ...say 2500....lets see...1.44 to 1

ratio...what is the torque now?....(where's Topher when ya need him!)

anyway...you fellas see what I mean..these thoughts have been working on me

for awhile..I certainly dont know for sure just how it would be..but the

numbers sure seem favorable.

Some of you know , or remember a year or 2 ago I was fooling around with a

24 hp vtwin and a 60 inch ivo 3 blade. I was able to turn the ivo at a hub

speed of 2200, pitched at the same degree that it was on my cuyuna. At 2200

hub speed..the firefly would run 60 mph.

now..how can that be?...Cuyuna ULII-02 rated at 38 hp and the Vtwin rated at

24hp...both close performance when bolted to a reduction drive with a prop

for the load?...

How can that be? Because the rating for the two strokes is at 6500 rpm and

the rating for the little industrial engines is at 3500.

Relationship between torque and HP is really simple: power in units of "hp",

torque is in "lb-ft", and rotation rate is in "rpm", then

power = torque dralle.txt gigi.txt grant.txt matt.txt save.txt rotation rate / 5252

(This means that the hp and torque curves always cross(they are equal) at

5252 rpm.)

So an engine with a hp rating given at a lower rpm will make more torque

then an engine with the same hp rating at a higher rpm.

Example:

Engine A makes 100 hp at 6000 rpm --> torque = 100*5252/6000= 87.5

Engine B makes 100 hp at 3000 rpm --> torque = 100*5252/3000= 157

Half the rpm twice the torque.

Put them both through a reduction drive to get them to the same rpm say 2200

so you can turn a nice big prop and they will both have the same torque.

Torque at 2200 = 100*5252/2200=238.7

100 hp at a given rpm is always the same torque... don't care where it comes

from.

Comparing the little industrial motors which would be perfect except for

having a poor power to weight ratio with the lighter 2-strokes you get

Rotax 503 makes 50 hp (at) 6800 rpm --> torque = 50*5252/6800= 38.6

Brigss ns600 makes 24 hp at 3600 rpm --> torque = 24*5252/3600= 35.01

So yes the torque is about the same at the engine output shaft... but that

isn't what matters, we need torque at the prop shaft

When you put both engines through a redrive to get to a usable prop rpm

Then you see the real usable torque:

Rotax 503 makes 50 hp (at) 2500 prop rpm --> torque = 50*5252/2500= 105.0

Brigss ns600 makes 24 hp (at) 2500 prop rpm --> torque = 24*5252/2500= 50.4

Wow, half the power = half the torque... imagine that.

Sure the fuel burns are better( mostly cause your not making any power!),

but half the performance and it weights much more, especially after you add

the redrive.

I don't think these engines are ever going to make a high performance

aircraft engines. Low performance perhaps... but nobody wants low

performance.

Topher

jhauck(at)elmore.rr.com
Guest

Posted: Wed Jan 04, 2006 12:30 pm Post subject: 2 and 4 Stroke



|

| How can that be? Because the rating for the two strokes is at 6500

rpm and

| the rating for the little industrial engines is at 3500.

| I don't think these engines are ever going to make a high

performance

| aircraft engines. Low performance perhaps... but nobody wants low

| performance.

|

| Topher

Topher/Gang:

Thank you for presenting a very understandable explanation of hp and

torque. I also got a lot out of your comparison of the two

"different" engines' performance. Nice to have someone explain

something mathematical to us old guys that are not mathematically

inclined.

Take care,

john h

PS: Got a good dose of aviating today. First flight since I flew

back from Texas a month ago. Had some airplane parts to deliver to my

buddy, Ted Cowan, over on the other side of the Tallapoosa River.

Didn't get to log quite two hours, but what I got was first class.

The old 912ULS is clocking 1,099.8 hours and still keeps on ticking.

Amazed that it would even fly with all the dirt we picked up on the

flight out to Texas and back, but it did.

eugenezimmerman(at)dejazz
Guest

Posted: Wed Jan 04, 2006 2:24 pm Post subject: 2 and 4 Stroke



On Jan 4, 2006, at 3:34 PM, John Hauck wrote:

 	  Quote: 	
		   The old 912ULS is clocking 1,099.8 hours and still keeps on ticking.

	


WOW!

What is that?

More than $10,000.00 worth of hydrocarbons blown out the pipe?

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Jan 04, 2006 7:00 pm Post subject: 2 and 4 Stroke



Kolbers,

Just viewed a program on the History Channel, that described a two stroke

engine that drives a container ship. I wrote down the model number

"12K98MC" and Googled it. The engine is designed by MAN B&W Diesel,

Denmark. It has 12 cylinders, with a total output of 101,645 bhp or 8,470

bhp per cylinder. Bore of 3 feet, 2.58 inches and a stroke of 8 feet 8.72

inches and develops full power at 97 rpm. Burns 0.281 pounds of oil per

horsepower hour or 14.27 tons of oil per hour at rated hp. This is quite

efficient in that if one computes fuel burn for a 40 hp engine at this rate

it comes out to be less than two gallons per hour. The engine weighs 2,157

"tonnes". This works out to 42 pounds per hp. This engine is expected to

run about 8,000 hours per year for the life of the ship.

At rated hp, the engine uses 165 pounds of cylinder oil per hour or 0.00162

pounds of lub oil per hp hour. The ratio of piston lube oil to fuel is 173

to one.

Now if we could just improve the weight to hp ratio and shrink it down to 40

hp ........

Jack B. Hart FF004

Winchester, IN

do not archive

tombrandon(at)mac.com
Guest

Posted: Wed Jan 04, 2006 8:29 pm Post subject: 2 and 4 Stroke

This is what you want. http://www.bath.ac.uk/~ccsshb/12cyl/ do not archive On Jan 4, 2006, at 9:06 PM, Jack B. Hart wrote: <jbhart(at)onlyinternet.net> Kolbers, Just viewed a program on the History Channel, that described a two stroke engine that drives a container ship. I wrote down the model number "12K98MC" and Googled it. The engine is designed by MAN B&W Diesel, Denmark. It has 12 cylinders, with a total output of 101,645 bhp or 8,470 bhp per cylinder. Bore of 3 feet, 2.58 inches and a stroke of 8 feet 8.72 inches and develops full power at 97 rpm. Burns 0.281 pounds of oil per horsepower hour or 14.27 tons of oil per hour at rated hp. This is quite efficient in that if one computes fuel burn for a 40 hp engine at this rate it comes out to be less than two gallons per hour. The engine weighs 2,157 "tonnes". This works out to 42 pounds per hp. This engine is expected to run about 8,000 hours per year for the life of the ship. At rated hp, the engine uses 165 pounds of cylinder oil per hour or 0.00162 pounds of lub oil per hp hour. The ratio of piston lube oil to fuel is 173 to one. Now if we could just improve the weight to hp ratio and shrink it down to 40 hp ........ Jack B. Hart FF004 Winchester, IN

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