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brian Rupnow
02-05-2016, 09:21 AM
After building 10 four stroke i.c. engines, I would kind of like to try my hand at a two stroke. I have seen the Jan Ridder plans, and I know that people have problems getting these engines to run. In fact, the people who did get them to run had to modify them to do so. I have also seen the Rudy Kahoupt "Pioneer" two stroke with valves. The tiny engines similar to the Val are not what I want either. I have not been successful in my search for a conventional two stroke that can be built from bar stock with no castings. something with a 7/8" or 1" bore, preferably. Does anyone have a recommendation for a two stroke that can be built with conventional mill and lathe?----Brian brupnow@rogers.com

RichR
02-05-2016, 09:40 AM
Anything of interest here?:
http://www.john-tom.com/html/ICEngines.html

tlfamm
02-05-2016, 09:52 AM
Remember this (Popular Science 1946)? - I think it's two-stroke:



Part 1, June 1946 (scroll down 2 pages):
https://books.google.com/books?id=7SADAAAAMBAJ&pg=PA144#v=onepage&q&f=false

Part 2, July 1946:
https://books.google.com/books?id=TCEDAAAAMBAJ&pg=PA176#v=onepage&q&f=false

Part 3:, Aug 1946:
https://books.google.com/books?id=LiEDAAAAMBAJ&pg=PA176#v=onepage&q&f=false

brian Rupnow
02-05-2016, 11:35 AM
Remember this (Popular Science 1946)? - I think it's two-stroke:



Part 1, June 1946 (scroll down 2 pages):
https://books.google.com/books?id=7S...page&q&f=false

Part 2, July 1946:
https://books.google.com/books?id=TC...page&q&f=false

Part 3:, Aug 1946:
https://books.google.com/books?id=Li...page&q&f=false

Tifamm--Your links don't work.---Brian

tlfamm
02-05-2016, 12:20 PM
Sorry, I foolishly saw no need to check the links in the text I pasted - duh. Guaranteed to work now ...

flylo
02-05-2016, 01:00 PM
You might copy a Ohlsson & Rice 1HP with a bore & stroke 1.250" x 1.096" = 1.34CID 1hp @ 6300rpm. I have one on a Tiny Tiger genset like this
http://www.gasenginemagazine.com/gas-engines/ohlsson-and-rice-tiny-tiger-model-350-generators.aspx?SlideShow=4

RWO
02-05-2016, 01:01 PM
This one is nice. Hemingway sells the rough castings individually. You can get by with the crankcase only and make the rest from barstock. However, the front end would be a real PIA to duplicate. http://www.hemingwaykits.com/acatalog/Jones_605___Colin_Jones.html

RWO

brian Rupnow
02-05-2016, 01:01 PM
My working knowledge of two strokes?--Well, they have piston, rings, connecting rod and crankshaft similar to 4 cycle engines. They do not have a camshaft nor valves. The crankcase is closed and will hold pressure. They combine the strokes--When the piston is moving up on compression, it creates a vacuum in the sealed crankcase. The carburetor feeds into the crankcase thru a one way valve, most commonly a piece of very thin spring steel called a reed valve. The lubricating oil is mixed with the fuel, so as the fuel enters the crankcase it lubricates the crankshaft bearings and both ends of the connecting rod, and the cylinder wall. The engine is fired by a sparkplug at or slightly in advance of top dead center and the piston begins to move down in the cylinder on the power stroke. As the piston moves down in the cylinder, this raises the pressure in the crankcase, and the reed valve under the carburetor snaps shut so the pressure in the crankcase can not escape. At some point in it's downward travel, after most of the burning fuel charge has expended it's energy but the piston is still moving down, the piston uncovers a port in the side of the cylinder which is connected to the pressurized crankcase. The fact that the fuel charge in the crankcase is pressurized makes it flow from the crankcase, thru the port in the side of the cylinder, and into the cylinder itself. At this point, the piston bottoms out and begins it's upward travel on the compression stroke. The side of the piston first closes off the port in the side in the side of the cylinder so that the charge of fuel which is now in the cylinder can not escape back into the crankcase. The piston then continues towards top dead center compressing the fuel charge and once again creating a vacuum in the crankcase to draw in more air/fuel mixture. Then the cycle repeats itself. The two cycle engine fires every time the piston reaches top dead center. From what I remember, the top of the piston is not flat, but has a "shape" to it which has something to do with keeping the burning fuel charge from blowing back thru the port into the crankcase---(I could be wrong on that reason.) ----So much for the theory behind two cycle engines.---Like everything else in life, the devil is in the details. If the piston has rings on it, how does it pass a port in the side of the cylinder without breaking the rings? How far down the stroke of the cylinder is the port so that it optimizes the power from the expanding fuel charge and still allows some time for the pressurized charge to flow upward from the crankcase into the cylinder. Would a model engine require seals on the crankshaft where it exits the crankcase, similar to 2 cycle snowmobile engines. (I once had a Yamaha snowmobile that had bad crankscase seals--it would go like stink at high speed but stall every time you slowed to an idle.) I know that there are many variations to what I have described. I know that the Jan Ridders design pressurizes the fuel charge in a separate compartment. I also know that two cycle chainsaws and weedeaters have flat top pistons, and I'm not sure how they get away with that. So you see, I know a great deal about 2 cycle engines. that is the good news. However, there is a great deal more that I don't know about 2 cycle engines, and that is what keeps me from boldly jumping into the design and fabrication of an engine which is doomed to failure because of the things I don't know. If I do this at all, I would much rather follow in someone else's footsteps.---Brian

ironmonger
02-05-2016, 01:23 PM
How about a 1:10 scale Lister CS. I often wondered how well real scale diesels operate... The engine might not be too bad but I bet the injectors would be a bugger

brian Rupnow
02-05-2016, 02:43 PM
No, I don't want diesel, glow, nor compression ignition engine plans. The old single cylinder Maytag engine would be just about perfect . The right speed and simplicity and a minimum of moving parts.

hitnmiss
02-05-2016, 03:36 PM
Hi Brian,

I know a little about 2-strokes from my model airplane days.

Pistons have a vertical dam machined in to direct the intake charge upward and not directly into the exhaust port. Some engines are flat top and they have Schnuerle porting which are typically higher performance engines.

https://en.wikipedia.org/wiki/Schnuerle_porting

I'd go with a machined damn in the piston because our engines are fairly low performance and I think it would be easier to get right.

2-strokes do have valves, in r/c airplane motors they usually use a ported hollow crankcase that communicates to the carb at the right time. Some use a rear crankcase rotary valve driven with the crank pin. Some use a reed valve which is a simple 1-way valve (like a cox .049 engine) These run backwards almost as well as forward.

Lot's of r/c engines have rings, they slide right past the ports. Usually a ringed engine will have the port divided into smaller segments to help the ring.

Yow Ling
02-05-2016, 03:59 PM
Brian, you seem to have missed the exhaust in your description, on the power stroke as the piston decends the exhaust port is uncovered and allows the highpressure burnt mixture to leave the cylinder before the transfer ports are uncovered, the period between the exhaust opening and the transfers opening is called the blowdown period if it is too short the ezhaust will travel down the transfer ports contaminating the mixture.
The timing of the ports is critical to the operation of the engine. If you want maximum power from the engine you will need to design an expansion chamber, which if operatig correctly will destroy your understanding of 2 strokes as you knew them. What you described was a pre ww2 twostroke similar to a villiers lawnmower engine. Which would be an excelent engine to copy and scale as a model.

Pistin rings are held in position with a peg in the ring groove to stop them snagging an end in a large port like the exhaust. they can be pinned so the ring gap is constantly in contact with the cylinder wall , but if pinned over a small port they work fine.

The best ever 2 stroke engine is the Aprilia RSA125 making around 53 hp from 125cc, this technical marvel was created by Mr Jan Thiel , widley recognised as the worlds greatest 2 stroke tuner, worth looking up

Here is a 98cc villiers with an overhung crank (easy to align) http://www.tanygraig.force9.co.uk/John/villjdl.htm

Norman Bain
02-05-2016, 04:03 PM
... If the piston has rings on it, how does it pass a port in the side of the cylinder without breaking the rings? How far down the stroke of the cylinder is the port so that it optimizes the power from the expanding fuel charge and still allows some time for the pressurized charge to flow upward from the crankcase into the cylinder.---Brian

The rings do expand into the port space when the rings pass over the port. The port top, side and bottom edges are given a slight chamfer on the bore side to allow the ring to survive the experience.

The lower edge of the port is exactly at the top of piston at BDC. The top edge of the port is as high as you want to make it; the general theory is the higher the top of the port is (and the motor still runs) the more power produced ... s**t I am going to get fried for saying that. That said, I doubt you are targeting racing outputs per cube so make top edge of port low ... it is easier to raise it than lower it.

Cheers,
Norman

Yow Ling
02-05-2016, 04:11 PM
Another great engine to copy/scale would be the Trojan Mini Motor , which is designed as a clip on bicycle assist motor, I have one on a bike

https://cyclemaster.wordpress.com/page-13-the-minimotor/

The crank case is 2 simple castings, easy to make on a mill, no reed valve as it is a piston ported engine , and with the factory exhaust , oozes with character

brian Rupnow
02-05-2016, 04:13 PM
Yow Ling--You are right. In my burst of enthusiastic writing, I just plain forgot the exhaust stroke, which coincides with the compression stroke. I like to run Viton rings, and since they are a type of heat resistant rubber o-ring, I don't think they would survive sliding past intake or exhaust ports.

Norman Bain
02-05-2016, 04:21 PM
From what I remember, the top of the piston is not flat, but has a "shape" to it which has something to do with keeping the burning fuel charge from blowing back thru the port into the crankcase---Brian

The tops of the pistons can (and probably will) be flat in your chosen design. The fancy tops on the pistons assist keeping the outer edge low (often so the port is opened sooner and longer), compression up and assist the air flows within the upper cylinder generally. Lots of theory out there about keeping the fresh and spent charge working in tandem with the incoming fresh charge and the exhaust.

The air (sound wave) mechanisms of the exhaust pipe (the tapered ones) do make the big power in that they extract spent gasses (over extract actually) then ram back the over extracted fresh charge in a "just in time" style before exhaust port is closed by the piston.

I suggest ignore all the fancy piston top styles and the fancy exhaust styles. Lawnmowers run just fine with flat pistons and non-fancy exhaust systems.

Cheers,
Norman

Yow Ling
02-05-2016, 04:26 PM
Yow Ling--You are right. In my burst of enthusiastic writing, I just plain forgot the exhaust stroke, which coincides with the compression stroke. I like to run Viton rings, and since they are a type of heat resistant rubber o-ring, I don't think they would survive sliding past intake or exhaust ports.

Brian there are only 2 strokes up and down, up does the compression and intake into the crankcase, down does the power stroke, ehhaust stroke and alows the transfer phase to occur near bdc. I think you are right about the viton rings getting munched, worth a try though, do you have a chainsaw to try it on, cant do any harm if it doesnt work

Yow Ling
02-05-2016, 04:28 PM
The shaped pistons are called deflector pistons , they went out of fashon in the 1950s when schurnle loop scavenging became popular

Norman Bain
02-05-2016, 04:30 PM
The reed valve style is the more modern approach. I figure a strip of material from a thickness gauge would work just fine. Just make sure that when the reed blows inwards it has a curved surface to roll onto. If that curved surface is not there the reed will break off and work its way thru your engine. Reed must be light enough to "open" in the vacuum.

There is also the "piston port" approach. The piston has a small hole in it that exposes the carb hole when the piston is high enough to be causing crankcase vacuum. This design allows carb to be closer to the cylinder. Piston is normally longer in this design; which may well be a good thing.

Cheers,
Norman

Yow Ling
02-05-2016, 04:38 PM
maybe this link will work

Piston port 2t vs 4t
Victa mower engine
https://www.outdoorking.com/forum/uploads/usergals/2015/08/full-7392-23385-victa_engine_09.jpg

another simple popular engine is Iron Horse , it has reeds

brian Rupnow
02-05-2016, 05:08 PM
I have been revisiting the Jan Ridders "Two Stroke Puppy" design, and though I have heard of problems with it, (This is not my experience talking---It is based on threads from other builders about their difficulties in getting this engine to run) his approach of having a separate "expansion chamber" which does the job that the crankcase normally does solves a lot of problems. It does however call for a piston which is lapped into the bore of the cylinder, thus eliminating the rings completely to solve the issue of getting rings past the ports. His engine is designed in metric, with a 14 mm (.552") bore and a 15 mm (.591") stroke. I would probably scale that up to a 1" bore with a 1.07" stroke. This is a scale factor of 1.814:1---- The volume of the expansion chamber is not a linear calculation, so I might have to make the expansion chamber with one "adjustable" end so I could tweak the volume to it's most suitable size. Air cooled cylinders are much simpler to build than water cooled ones, but I understand this engine runs very hot so would benefit from water cooling.-One of my Australian friends built the "Puppy", and the only way he could get it to run was by increasing the piston head height to give it a higher compression ratio.--I will have to research this a little.

dp
02-05-2016, 05:50 PM
Very small two-stroke engines have lapped pistons and no rings. Power plants will have rings, often just a single 'L' section (Dykes) ring but also plain rings. They're very thin vs 4-stroke engines, but these are not worth screwing with at your scale.

The intake can be piston port or a valve. Reed valves are probably more trouble than they're worth and not needed. A very thin piece of shim plate the diameter of a Looney free floating will work. See the Cox glow engines where the carb, intake "valve" and fuel tank are integrated. These is a very reproducible design. Two lines of thought on the cylinder - a pressed iron sleeve, or an iron cylinder. If a sleeve is used it allows you to use a Dremel to create the ports in the aluminum cylinder then grind the ports in sleeve. Cox uses a single piece and the ports are machined into it. That works really well. No rings as no rings are needed.

The base of the Cox cylinder is threaded but can be flanged. Same with the cylinder head. No bearings are needed but you need to hold tolerances very tight. Any air leak in the intake will create a shelf queen.

Strongly advise using over the counter glow plugs, and the Cox glow heads are a one-piece threaded cylnder head with integral glow element.

There's just about no chance in hell of getting one of these engines to idle, but even a home-made engine should be able to hum loudly along at 10,000 rpm. Engines build for model motor boats use a flywheel with a built-in string groove for pull-starting them. The flywheels are very light weight relative to the 4-stroke engines because there's no coasting cycles in the two-stroke.

Background: http://www.craftsmanshipmuseum.com/Cox.htm

https://upload.wikimedia.org/wikipedia/commons/d/d6/Old_Cox_Babe_Bee_engine_dissasembled.JPG (http://www.craftsmanshipmuseum.com/Cox.htm)

Norman Bain
02-05-2016, 06:14 PM
How about considering giving the Viton a go? Perhaps with a bit more "stretch" in the fit than in the 4-stroke configuration.

Worst that can happen is you need to make a new piston.

Suggestions re the no-ring approach also have merit.

Norman

brian Rupnow
02-05-2016, 06:28 PM
One of the companies I worked for during my career made hot chamber die-casting machines. The "gooseneck" or injection cylinder was made from H13 steel and was totally immersed in molten zinc all day. The injector piston was 1/2" diameter, and I think it too was H13 steel. The "goosenecks" were honed to fit the pistons using a Sunnen honing machine. I don't know if I have the ability in my home shop to hone a 1" cast iron piston to a close enough fit in a 1" cast iron cylinder or not. I have read a couple of posts where people who built the "two stroke puppy" with very close fitting pistons found that after a couple of days on the shelf the pistons would "seize" into the cylinders and they would have to dismantle the engines and press the pistons out.

dp
02-05-2016, 06:51 PM
The fuel has castor oil in it and will gum up if you don't clean them after running. That's the nature of close tolerances. There is also the possibility they were just too tight. Thinned tooth paste is an adequate slurry for the lapping. You can use multiple cylinders to lap in the piston, then lap the piston to the final cylinder if turning to lappable dimensions is iffy. It is probably the same process for making air bearings which a lot of HSM types do.

brian Rupnow
02-06-2016, 09:53 AM
Apparently E.T. Westbury designed a 2 cycle spark ignition engine called the "Wombat" but I can not find anything about who has the plans or where I could buy them. Can anyone help?---Brian

RichR
02-06-2016, 12:33 PM
Hi Brian
According to this chart:
http://modelenginenews.org/etw/etw_engines.html
it appeared in Model Engineer volume 134 issue 3350. That is incorrect. It appears in issue 3351, part of which is online here:
http://modelenginenews.altervista.org/mecd/3351.img.html#781
and continues here:
http://modelenginenews.altervista.org/mecd/3352.img.html#i835
http://modelenginenews.altervista.org/mecd/3353.img.html#i887
OK, I don't know how long this goes on, so here is the index page with links:
http://modelenginenews.altervista.org/map.html
Scroll down to "ME Vol 134 Issue 3351 Index" and you can work your way through. These are scans of the original magazine pages
so you can't search for text. Hope this helps.

RWO
02-06-2016, 01:05 PM
See http://modelenginenews.org/index.html for ET Westbury's engines including Wombat. Lot's of 2-stroke sparkers there.

RWO

dp
02-06-2016, 01:26 PM
Here is a general subject index for the archived magazines.

http://modelenginenews.altervista.org/mecd/subject.index.html

(http://modelenginenews.altervista.org/mecd/subject.index.html)Tubal Cain (version 1, not Lyle Peterson) provides a nice write up on making piston rings.
http://modelenginenews.altervista.org/mecd/3961.img.html#85

Here's Part II
http://modelenginenews.altervista.org/mecd/3963.img.html

The series continues with odd numbered volumes to
http://modelenginenews.altervista.org/mecd/3977.img.html

brian Rupnow
02-06-2016, 01:47 PM
Thank you very kindly gentlemen. I have secured a set of the 'Wombat" drawings, and they are printing out as I type this.---I appreciate the info on making piston rings.---Brian

thaiguzzi
02-07-2016, 09:29 AM
Bloke in Australia has just finished building a supercharged (!!) V12 two stroke from bar stock. From scratch and his plans. There's a build thread in the M.E website on the net under IC engines. There's a video of it finally running, and boy, does it run!

old mart
02-08-2016, 03:04 PM
Don't use caster oil as a lubricant, modern synthetic two stroke oils are a far superior option. Bel Ray is one of the best. I mentioned piston rings made out of steel in your flat twin thread. In the late sixty's in the UK, AMC Motorcycles made some two stroke engines which had the transfer ports cast just as deep grooves in the cylinder. The piston itself made the grooves function as ports. They were not very good but they worked.

steve45
02-08-2016, 08:00 PM
My 150 HP JetSki uses flat top pistons, composite reeds, and so many ports that you wonder how the cylinder stays together. The ports are beveled ever so slightly to prevent the rings from hanging up.

Keep in mind that there are iron rings and chrome rings used in the small 2-strokes. The iron rings are thicker and require a lot more lubrication. The manufacturers shifted toward chrome in an effort to reduce smoke.

The inside arc of the ring is often beveled so that compression pressure pushes outward on the ring for better sealing.

I haven't even gotten into the LARGE 2-strokes. These engines are natural gas fired and they have camshafts to operate the gas admission valves. The air doesn't go though the crankcase on them, rather they have separate cylinders called scavenging cylinders that compress the air that is pumped to the cylinders.

Granted, these engines are a little larger than what you have in mind, in the thousands of horsepower. The Cooper Bessemer Z-330 is one of the largest at 10,000 HP. There were 4 in existence when I worked with one about 12 years ago. https://www.geoilandgas.com/sites/geog.dev.local/files/GEA31211_Cooper-Bessemer_W-330C3_Flyer_R3.pdf

Now, if you really want to get fancy, you might look at something like the Cooper Bessemer H-22 horizontal engine to model. These monsters were about 60 feet long, With the power cylinders on one end, the gas compressor cylinders on the other. There were two rows of cylinders with a crankshaft and flywheel in the middle. I believe that these are actually 4 stroke engines however because this video shows the fuel valve opening every other stroke. This engine has two pistons mounted on each rod. They are amazing engines to watch! https://www.youtube.com/watch?v=HEP93ac0In8

RichR
02-08-2016, 10:36 PM
Hi Brian
Here's a Jan Ridder 2 stroke someone built and got running:
http://start-model-engineering.co.uk/category/jan-ridders-simple-two-stroke/
More info and additional notes at bottom of page:
http://ridders.nu/Webpaginas/pagina_tweetakt_motor/tweetakt_frameset.htm
You can request a free set of plans here:
http://ridders.nu/Webpaginas/aanvraag_tweetakt.htm

old mart
02-09-2016, 09:29 AM
If you want a complicated two stroke engine, look no further than the Napier Deltic.

brian Rupnow
02-09-2016, 12:13 PM
Old Mart--Your post is like a drink of water to a drowning man----Here I am, posting a request for a simple 2 stroke engine that I can possibly machine in my shop, and you come up with this?---Brian

brian Rupnow
02-10-2016, 09:05 AM
When I was a kid, I had an old Evinrude 2 cycle boat engine. It ran slow, idled slow, and started easily. This is far more in line with what I want t build. I can't believe that there are no engine plans for model versions of that type of engine out there somewhere.---Brian.

J Tiers
02-10-2016, 11:38 AM
When I was a kid, I had an old Evinrude 2 cycle boat engine. It ran slow, idled slow, and started easily. This is far more in line with what I want t build. I can't believe that there are no engine plans for model versions of that type of engine out there somewhere.---Brian.

So, here is your chance to do a set of plans for one!

dave_r
02-10-2016, 03:05 PM
Old Mart--Your post is like a drink of water to a drowning man----Here I am, posting a request for a simple 2 stroke engine that I can possibly machine in my shop, and you come up with this?---Brian

But wouldn't it be AWESOME to see that running on your workbench!

brian Rupnow
02-10-2016, 08:14 PM
I am curious about what the size limitations are on lapped pistons with no rings on them. I know it is commonly done on 1/2" cylinder/piston combinations. If I used a cast iron piston in a cast iron liner, life would be so much simpler in terms of the rings catching on the ports. I would like to do it with a 1" diameter cylinder. I don't have access to a Sunnen honing machine--just my lathe and mill. Bitter experience has shown me that I really suck at making cast iron rings. That is why, when I build an i.c. engine I always go with Viton rings. They are cheap, they seal perfectly, and they give instant compression. Trouble is, they wouldn't slide past a port without expanding into it and failing immediately. If it is possible to go with a lapped, ringless piston in a 1" diameter cylinder, what would be the downside of doing that?----Brian

bob_s
02-10-2016, 08:56 PM
The main downside is the large surface area of the contact, which is prone to corrosion.

ironmonger
02-10-2016, 09:27 PM
As an experiment, I ran my 100cc Bridgestone 100R engine with out any rings. It was a little harder to start but ran strong and idled. The Bridgestone used the same high silicon aluminium alloy for both the piston and the cylinder. The cylinder was hard chrome directly on the aluminium and the idea was that the piston and cylinder expanded and contracted at the same rate. Donít know why that would be different with a cast iron cylinder and pistons. Pretty durable... it's a 1967 engine that still ran 3 years ago when I pulled the bike apart to build a new frame.

Not much corrosion with 2 strokes, what with the oil gas mix. Many two cycle engines use aluminium pistons in cast iron cylinders... no rust, you just have to allow for expansion.

The Bridgestone used a rotary valve on the crankcase inlet for the carburetor instead of piston porting or reed valves. This allowed for asymmetrical timing of the intake system relative to piston position.

This brochure (http://www.bridgestonemotorcycle.com/documents/BSTuning6_low.pdf) is overload, but there are some good drawing that show how the valves worked.

RichR
02-10-2016, 09:52 PM
I am curious about what the size limitations are on lapped pistons with no rings on them. I know it is commonly done on 1/2" cylinder/piston combinations. If I used a cast iron piston in a cast iron liner, life would be so much simpler in terms of the rings catching on the ports. I would like to do it with a 1" diameter cylinder. I don't have access to a Sunnen honing machine--just my lathe and mill. Bitter experience has shown me that I really suck at making cast iron rings. That is why, when I build an i.c. engine I always go with Viton rings. They are cheap, they seal perfectly, and they give instant compression. Trouble is, they wouldn't slide past a port without expanding into it and failing immediately. If it is possible to go with a lapped, ringless piston in a 1" diameter cylinder, what would be the downside of doing that?----Brian

If you check the links to the "Simple Two Stroke Engine" in my reply #34 you'll see it doesn't use rings. Bore and stroke are 24 mm.

Willy
02-10-2016, 10:30 PM
.........................
...................Bitter experience has shown me that I really suck at making cast iron rings. That is why, when I build an i.c. engine I always go with Viton rings. They are cheap, they seal perfectly, and they give instant compression. Trouble is, they wouldn't slide past a port without expanding into it and failing immediately. If it is possible to go with a lapped, ringless piston in a 1" diameter cylinder, what would be the downside of doing that?----Brian

Another option would be to use a cast iron, bar stock cylinder, using an aluminum piston that you build to accept replacement cast iron piston ring/rings from an 18cc weedeater engine. I believe the bore is just slightly over 1".
The cylinder can be honed using a brake cylinder hone.
That set of rings may be as close as your nearest lawn and garden parts and repair shop.

brian Rupnow
02-11-2016, 09:07 AM
Willy--I can buy cast iron rings in the common small diameters. They are not really cheap, but I know they are available.---thank you.--Brian

10KPete
02-11-2016, 09:45 AM
You guys may not know it but you are providing one heck of an education on the subject of materials and availability for
pistons, liners and rings!! At least for this pilgrim.

Pete

brian Rupnow
02-11-2016, 10:14 AM
10KPete--Sometimes I am absolutely amazed by how much I know about so many things. I am even more amazed about the number of things about which I am absolutely ignorant. I'm 69 years old. Sex, drugs, and rock and roll just don't do it for me anymore. But learning new stuff---That's the most powerful stimulant in my life now, and I love it!!!---Brian

Seastar
02-11-2016, 10:52 AM
Brian
I just sold a 72' boat with two 2 stroke Detroit Diesel 16-92 engines of 1950 HP each.
That's 16 cylinders with 92 cubic inch displacement in each engine.
I ran them to almost 3000 hours and they are still going.
The porting system on these engine was unique and could be adapted to a spark fired gas engine.
It would be a lot of work but you would have a model engine like no other.
Here is a brief history of the development of this series of engine by GM and others.
http://www.dieselduck.info/historical/01%20diesel%20engine/detroit%20diesel/#.Vryr7_A8KrV
Brief explanation of the operating system here
https://www.youtube.com/watch?v=lcBiCyX9lnk
Bill

brian Rupnow
02-11-2016, 11:21 AM
I have been studying on both Edgar Westbury's two cycle timing diagram for 2 strokes and on Malcolm stride's diagram on page 132 of "Miniature internal combustion engines". When I add angular values to Westbury's diagram they come within one or two degrees of Malcolm stride's diagram which is given in degrees as opposed to Westbury's diagram which is given in fractions of piston travel. These dimensions are not to the center of the ports, but are to the point on the port closest to the direction of piston travel, so just at the point when the port begins to be uncovered by the piston. If anybody disagrees with what I have shown, please speak up. You will see that the piston travel I used is 3/4", which corresponds exactly with the piston travel in the Wombat engine. I should now be able to transpose these angular values to the Wombat, to see where the ports should be placed.---(I think)----Brian
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow030/WESTBURY%202%20STROKE%20TIMING%20CYCLE_zpslk0bflha .jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow030/WESTBURY%202%20STROKE%20TIMING%20CYCLE_zpslk0bflha .jpg.html)

10KPete
02-11-2016, 02:18 PM
10KPete--Sometimes I am absolutely amazed by how much I know about so many things. I am even more amazed about the number of things about which I am absolutely ignorant. I'm 69 years old. Sex, drugs, and rock and roll just don't do it for me anymore. But learning new stuff---That's the most powerful stimulant in my life now, and I love it!!!---Brian

Now that is just beyond amazing. You have just described, exactly, my own condition in life including age. I swear I've forgotten
more than I currently know and I just keep looking for more. And the more I find the more ignorant I become! Life and
Learning are the ultimate trip.

Pete

brian Rupnow
02-11-2016, 02:22 PM
I think I'll go upstairs now and soak my head!! I haven't felt this damned dumb since I took long division in school 60 years ago!!!

brian Rupnow
02-11-2016, 08:18 PM
My Goodness---What a huge can of worms I have opened. I've never really given a lot of thought to two stroke engines. My world of hot-rods and drag racing only ever involved four cycle engines. My engineering career really never had much to do with any kind of engine. Specialty "one of" machines and automation, but no engines. I never played with two cycle model airplanes (I did get one as a birthday gift when I was about 13, but never could get it to run.) My "hands on" experience with two cycle engines was limited to outboard motors, chainsaws, weed-eaters, and lawn mowers---and I never really repaired any of them, other than to change a sparkplug or blow out a plugged fuel line. I have learned more about two cycle engines in the last 5 days than I knew in my entire lifetime. The "simple little engine" that has no cams, no gears, no valves, no rocker arms, no pushrods, no lifters----has taken on a whole new mystery and mathematical complexity than I never had imagined. I still hope to build one--but the more I find out, the more I realize I have to find out even more, before committing time and energy to a project doomed to failure because I entered it blindly without fully understanding what I was doing. Thank you so much to all of you who are helping to educate me.---Brian

Willy
02-11-2016, 09:20 PM
Brian I know you've already got more brain pain now than after eating way too much ice cream, way too fast, but...

Please accept this gift. Below is a link to a 171 page PDF file book entitled Two Stroke Tuners Handbook by Gordon Jennings.
It covers, in an easy to digest fashion, the subjects of crank train, cylinder head, expansion chambers, cylinder scavenging, port timing, crankcase pumping, carburetion, ignition, etc.

I first bought this book in 1973 when it first came out and I can't recommend a better book at this point to give you a better understanding and insight into the subject that you have thrust upon yourself.:)
Please take the time to at least download it and look it over as I'm sure that it will answer more than a handful of questions as they arise.

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiV9JbOkPHKAhUY92MKHTIcBokQFggcMAA&url=http%3A%2F%2Fwww.amrca.com%2Ftech%2Ftuners.pdf&usg=AFQjCNFwMFuZ2ja58wF9ozRZ9VqG6aC7UQ&sig2=TuLh7PlvOg5Yvvf51YsW7A

brian Rupnow
02-12-2016, 07:39 AM
Thank you Willy--I will print that out and read thru it.---Brian

Willy
02-12-2016, 09:53 AM
Brian, I still have that little book in excellent shape in my bookcase. Good info by Gordon Jennings who was originally the editor of the now defunct Cycle magazine and later on at Car and Driver. He is a good technical writer so I'm hoping you get some good info from it.
I was very surprised to see that it I was able to find it for free online, as it is listed at $495usd on Amazon.com, although I have seen it elsewhere for as "little" as $175.

Looks like I'm going to have to research the value of my library a bit more. I may have to take the guns out of the safe and put my books there instead.:)

brian Rupnow
02-12-2016, 05:44 PM
There is so much information out there, and so much conflicting information, that I am lost in space!! I know what I want--a slow and simple two stroke. I want to be able to make it on my lathe and mill. I would like to copy a tried and proven design so that I don't have to "experiment" with port spacing and positions. I know my most severe limitation---I suck at making cast iron rings. Much research has shown me that lapped pistons with no rings have a practical upper limit of about 1" diameter. If I make it air cooled then I have to press or shrink fit the liner into an aluminum cylinder for proper heat transfer. If I make it water cooled, then I just have to bore the aluminum cylinder "size on size" with the outer diameter of the liner and let Loctite do my sealing--I won't have to worry about heat transfer.---Don't worry--I'm going somewhere with this. The 1912 Hubbard marine engine is a slow, simple two stroke with a 24 mm diameter lapped piston, and no rings. I have a drawing here from the model engine fairy that shows what size the ports are, where they are located, and enough "general" information that I can replicate a clone of it using Solidworks. I called my local machine shop this afternoon and they do have a Sunnen Hone, and 1" is well within their range of work (in case I have to cheat). I have downloaded reams of information from the internet and printed it out to the point where my printer is screaming for a new ink cartridge. I have talked about it to my wife until she doesn't want to hear "Another thing about those stupid little engines I build!!" My head is in flames from thinking about two stroke engines.---I'm off to do some more research----Brian

woodenbird
02-12-2016, 06:14 PM
Good for you, Brian! Keep plugging away. We all are looking forward to your new design.

brian Rupnow
02-14-2016, 04:11 PM
I have abandoned this thread because of inconsistencies in the original drawings I worked from, and the realization that I don't really understand two stroke engines well enough to embark on building this sophisticated a model. I have instead turned my efforts to the design of an engine who's full size counterpart was built over a hundred years ago. If you wish to follow my efforts to make a working two stroke engine, then go to this link.---Brian
http://bbs.homeshopmachinist.net/threads/69627-Old-School-Barstock-2-Stroke