2 Cycle Engine from Bar Stock

[canadianhorsepower]

Rod is 1.563" stroke 0.75"

still only give 133.74 transfer and 154.7 exhaust
I would be satisfied with this is a torque porting
but considering the size It should be good:hDe:

 

[Brian Rupnow]

Okay, that's it!! There are enough anomalies in the original design, combined with the fact that as near as I can tell there are no records of anyone having built and ran this engine, that I am abandoning it. Not really a big deal, as it gave me a Sunday's worth of entertainment and did contribute somewhat to my knowledge of two cycle engines. Now it is time for me to ask for help. I was hoping to get by without laying out any money for plans, but that hasn't worked out. I have searched the internet for plans that I could buy, and that search came up dry as well. I even went to Chapters Bookstore in Barrie and to the Hobby Store in Barrie and they couldn't help me. So--This is what I want. Plans for a single cylinder, spark ignition, two cycle model engine that runs on gasoline or Coleman fuel, and has been actually built and ran by someone. I do not want plans for a glow engine nor a diesel engine. I do not want plans that have been made by someone but never "proven" by being built and ran. If you have a set of plans for what I want, and wish to help, please send them to [email protected] . If you know of a book that has these plans, please tell me the name of it, and possibly where I can purchase it. There is a lot of work in building a model engine, and as much as I enjoy it, I do not want to build a prototype of an engine which I don't as yet fully understand.---Thank You---Brian Rupnow

 

[canadianhorsepower]

http://www.myhobbystore.co.uk/product/17485/busy-bee-pe23


http://www.myhobbystore.co.uk/product/17486/phoenix-pe24

those 2 are not bad
I just upload a book on 2 strokes engine



good luck

 

[Brian Rupnow]

I have had my suspicions confirmed by a knowledgeable gentleman in the U.K.

The Wombat was the last of Westbury's engines which he designed in the last few years of his life when he was not well. It is arguably a 1940's design built in the 1960's at a time when commercially built engines were more capable that this engine was ever likely to be, so there was never a lot of interest in it.

We know that there have been a number of attempts to make this engine, we even know of the location of a set of patterns for it :-\ But as you have found there are numerous mistakes in the drawings. It is believed that it could be made to go if you put together a timing diagram for it and redesigned accordingly.

If it was built and made to run it would be a very collectable/valuable engine.

 

[canadianhorsepower]

It is believed that it could be made to go if you put together a timing diagram for it and redesigned accordingly.
If it was built and made to run it would be a very collectable/valuable engine. [/I]

I would be interested in giving it a try,
were can I get a copy of the plans.

did you check the book on 2 stroke engine ??

 

[kf2qd]

http://www.homemodelenginemachinist.com/downloads/60-model-airplane-engine-as-dwg-114.html

A link to the cad file for a .60 2-stroke bar stock engine. The one in may avatar picture.

And you might want to look at Schnuerle porting. Simpler, lighter piston and simpler head.

 

[Brian Rupnow]

kf2qd---A few questions, if I may. Is that engine spark ignition, glow plug, or diesel? Did anyone actually build it? Are there any pictures or video of the engine running? What was the compression ratio?---Brian

 

[Brian Rupnow]

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

 

[petertha]

Brian, you might not want to dismiss bar stock glow engine designs just because glow was their original configuration. Looks like there are kits to convert methanol glow plug engines to spark ignition using CDI & replacement plugs that match the same glow plug thread. I have not delved into this myself but maybe these links will get you started or others have experience with conversions on commercial engines.

http://www.justengines.co.uk/acatalog/Customer_Feedback__and_Our_Experience.html
http://www.justengines.co.uk/acatalog/Ignition_Systems_for_Glow_Engines.html
http://www.ch-ignitions.com/index.php

 

[GailInNM]

Brian,
Lapped piston/cylinders were very common in the 1950- 1960 era glow plug model airplane engines with bores of 0.8 to 0.9 inches. A few were made with bores up to 1-1/8 inches that I know of. As I recall the chief limitation was the weight of the piston in cast-iron as these were relatively high speed engines and were difficult to balance with the large cast-iron piston. Most of these engines used a steel liner with the cast-iron piston because steel has a slightly greater coefficient of expansion than the cast-iron. As the piston crown generally runs hotter than the cylinder this gave a fairly uniform fit over the temperature range.
Gail in NM

 

[Charles Lamont]

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.

You can buy iron piston rings, down to about 3/4".

 

[Brian Rupnow]

Thank You, Petertha, Gail, and Charles.---Petertha brings up a very good point about using gasoline and a conventional spark ignition in the glow type engines. I had thought of that myself, and the only thing I thought might have to be done was to lower the compression a bit to prevent pre-ignition. I wasn't sure if the porting would still be compatible with running gasoline fuel and a spark ignition, but according to those links Petertha sent me it doesn't seem to be a problem.---Brian

 

[canadianhorsepower]

I had thought of that myself, and the only thing I thought might have to be done was to lower the compression a bit to prevent pre-ignition.

Brian,
you don't even have to worry about the compression If you are talking methanol and gas the difference is so small, on the other hand if the engine was design to use nitro and you want to go gas then you will need to increase it

I wasn't sure if the porting would still be compatible with running gasoline fuel and a spark ignition,

porting is only to maximize your volumetric efficiency at your desired RPM
When I was doing lumberjack event I had a Husky 272 ported at 166 int 132 trans and 200 ex 12/1 trap comp ratio. And had made an adapter to replace the plug and used Glow plug and ran fine

 

[Brian Rupnow]

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

 

[canadianhorsepower]

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

Brian
it's wrong you MUST use the rod dimension
with the same stroke and same exhaust opening in degree
if your rod is longer by 200 thousand your piston will need to be lower by80 thousand check the book or free program I posted

 

[Brian Rupnow]

Luc--Color me confused!! Did you post a formulae or just give me the number of degrees as in post #13. if you gave me a formulae, please give it again.---Brian

 

[canadianhorsepower]

Luc--Color me confused!! Did you post a formulae or just give me the number of degrees as in post #13. if you gave me a formulae, please give it again.---Brian

I didn't post the formula I just gave the numbers
from this site
http://www.csgnetwork.com/directporttimingcalc.html
and input
stroke .750
rod 1.563
before dead center ( leave empty)
duration degree 120 (that's for transfer)
and hit the button
calculate height it will give you .1534
that is the distance from bdc that your ports will close

if you change the 120 for you 160 then it will give you .2656
and thats the distance from bdc where your port exhaust will close

that gives you 110 thou both open not bad assuming there is a lot of port area

I hope I didn't confuse you more

 

[GailInNM]

Brian,
The timing diagram that ETW shows is the general timing diagram that is further used to calculate the rotational diagram that is shown for most engines. The rotational diagram has to take into account the rod length.

I attach a quick sketch to show what is meant.

 

[Brian Rupnow]

Luc--where did you get the figure of 160?--also, if that calculation gives the distance from bottom dead center to the point where the ports will close, then does it follow that from the top of the liner it would be stroke, minus the resultant figure of .1534 minus the height of the port opening?

 

[Niels Abildgaard]

You can buy iron piston rings, down to about 3/4".

Where please?