2 cycle rotary valve engine

[nx06563]

Got my Owen Mate done. Waiting for a propeller to put on it and will build a test stand so I can try it out outside. Didn't realize at the start I was going to have to become an alchemist to mix fuel for it. Hope I don't gas myself or blow myself up.
It was a fun build and not too tough. I do understand the porting far better now so it was worth it. I will never put it on an airplane so maybe I can retrofit it for a friends tether car.
Ill do a video when and if I get it running.

 

[tornitore45]

Nice job.
Mixing you own fuel is not a problem. Finding the ingredient is where you start pulling your hairs.
Try a commercial product, is most likely cheaper than the mismatched quantity of ingredients you need to buy, if you can find them at all.

 

[lohring]

More than you wanted to know about fuel for model diesel engines.
https://adriansmodelaeroengines.com/catalog/main.php?cat_id=72
Lohring Miller

 

[awake]

You're right, Lohring, that is a lengthy article.

Can we just get the (ahem) compressed version?

 

[ALEX1952]

I aggree with tornitore4,5 back in the day the go faster control line or U control flyers, depending on which side of the pond you are, used Amyl nitrate as an additive to there diesel engines, which you could at that time buy over the counter at the pharmacy, I believe it is now a controlled substance and will get you locked up. It may also explain why my brain is not so sharp in my dotage, maybe due to passive sniffing.

 

[nx06563]

OK here I am, I have build the Owen Mate and am waiting for a prop to try and test start it. The whole process was to get familiar with two stroke design so I could design one for myself. I don't think I will ever fly an airplane so I want to build a stationary low rpm 2 cycle model.

I have started design of just such an engine with a 1" bore, 1.25" stroke. I am to the port timing portion. I intend on a front rotary disk valve.
After all my study I have a design with 120deg intake duration, 120 deg. exhaust port duration, and 100 deg. transfer port duration.

Question for the pros out there is are these port timing numbers proper for such an engine?

Also is there some formula for calculating port area.

Any guidance would be appreciated

 

[WOB]

IMHO, your valve timing is conservative and won't develop max power. This site Model Engine Tests
has a multitude of engine tests. Some of the tests contain specs of the valve/port timing.

WOB

 

[nx06563]

Checked the web site and the tests are all for Model airplane engines turning lots of RPM. I am looking for around 6000 RPM and easy starting. I guess power output is not the greatest concern. Still conservative with those considerations in mind?

 

[WOB]

It is easy to limit RPM. Just throttle the engine with an undersized carb. It will also aid starting.

WOB

 

[nx06563]

Do you have any suggestions for port timing since I a placing ports in the design right now?
Any guidance would be appreciated since this is the first 2 cycle I have designed.
Thanks for the help.

 

[Peter Twissell]

message deleted - posted to wrong thread.

 

[nx06563]

OK, I've got the Owen Mate built and running after making a tighter fitting piston and have progressed on with designing a simple 2 cycle one cylinder with a rotary disk intake valve.
I have things pretty well figured out but need confirmation on port timing. There is not a whole lot if info out there on 2 cycle port timing but I have settled on the following numbers. If anyone has advice to give I would love to hear it. This engine will be a stationary (not airplane) engine with a flywheel. I am hoping for a top rpm of 6 to 8 thousand and the ability to idle at a reasonable rpm.

Transfer port duration of 124 degrees
Exhaust port duration of 174 degrees
This gives a blow down of 26 degrees
The rotary disk valve will open at 100 degrees before TDC and close at 25 degrees after TDC.
1" Bore
1.25" Stroke
2.350" long rod

What do you think?

 

[nx06563]

I have finished building an Owen Mate and have it running after making a new tighter fitting piston. I have moved on to designing a simple 2 cycle stationary (not airplane) engine with a rotary disk intake valve.
I have it designed and have made a few pieces but am not sure of proper port timing for an engine with a flywheel that I want to run at a max of 6 to 8 thousand rpm and able to idle down . There is not a lot of info out there on port timing so I am looking for someone to critique what I currently am planning.
Here are the numbers
Exhaust port duration 174 deg.
Transfer port duration 124 deg.
for a blowdown of 25 deg.
1" bore
1.25" stroke

What do you think?

 

[WOB]

Some info on port timing of commercial engines can be found here: Ron's Model Engineering and Model IC Engines Index
On the left side scroll down and click on "resources". open up "design center" and scroll down to "discussions". The 3rd, 4th, and 5th topics will provide some info. The topic concerning FRV is equally applicable to RRV as far as timing is concerned.

I wonder about your design approach. You are wanting to use what is usually considered a high performance induction system on a relatively low RPM 2-stroke. The flywheel will provide no load, so you must be planning to drive some kind of load with the engine. Otherwise, limiting peak RPM will require running with the throttle mostly closed, so port timing can be very conservative.

 

[Steamchick]

I have no experience of disc valve 2-strokes, but I seem to remember (from >50 years ago?) of disc valves being a means of getting more power rather than anything else, when compared to simple ported engines. But I recall a test of a road bike - possibly a Grieves or Cotton? Possibly Rotax? - that I think had a disc valve, and had very good low throttle stability, without 4-stroking? Must do some research....!
Of course, the 2-stroke has always been a commercial success as a high-powered engine, rather than clean, fuel efficient, or low revving...
Please tell us me about your project?
Thanks,
K

 

[Steamchick]

Try this for some background?
https://www.cycleworld.com/exploring-two-stroke-motorcycle-engine-design/k

 

[Steamchick]

Also Kawasaki made lots of production bikes with disc valves, until Yamaha out-performed them with reed valves and clever tweaks to their 2-stroke engines. Rotax made disc valve engines into the 1990s... before pollution (exhaust emissions) from total loss oil systems was banned.

 

[nx06563]

The whole purpose of the rotary valve is for the design challenge not huge power. Plus it will be easier to change intake timing. My design is a direct drive off the crank.
This is my first design that hasn't partially copied someone else's concept, and a first step to a twingle. I like different stuff and ease of construction.
Thanks for the input

 

[Peter Twissell]

Ooh - twingle (split single). Now I'm watching carefully.

 

[Steamchick]

One engine that fascinated me, as it didn't use the crankcase for gas flow, was the 180 degree cranked twin, with 2 diameters of piston, so the lower chamber could induct then charge the opposite upper chamber - tried by Suzuki for clean combustion 2-stoke operation. But it didn't take off due to cost and difficulties of the assembly of pistion rings to bores!
K