A different opposed piston engine---

[Brian Rupnow]

That ought to keep my gas line from bouncing around!! Now if I can just find time to get everything out to the main garage for a try-out. I'm working on a design contract right now where I have to spend 8 hours a day "on-site" so it doesn't leave much time for playing with little engines. Oh well, its supposed to warm up to 0 degrees on the weekend.

 

[robcas631]

Brian,

Perhaps the exhaust needs to be "tuned?" Look at the muffler on my moped, aka now 50 MPH motorcycle.

Perhaps this helps?

 

[Brian Rupnow]

Well, the little mouse is ready to ROAR!!! Now it's just a matter of scraping together an hour of time to try it out. Working away from home certainly cuts into one's play time. This weekend is supposed to be a big birthday party for various grandchildren at my house, and I know I'm going to get press-ganged into a big house "slick-up" before everybody shows up.--Still an all--I think I can steal an hour to try this thing out. I soon have to finish with it because I'm starting to hear hints of disapproval about the number of hours I spend down in my workshop----which is not a good thing.

 

[Swifty]

Brian,

Perhaps the exhaust needs to be "tuned?" Look at the muffler on my moped, aka now 50 MPH motorcycle.

Perhaps this helps?

Brings back memories of racing 2 strokes in my 20's, we used expansion chamber exhausts, very noisy things. The neighbours certainly knew when I was tuning it up.

Paul.

 

[robcas631]

Brian,

I can relate regarding spending too much time in the shop. However, I am rehauling a steam engine for my father and must finish. I will post results at a later time.

I look forward to seeing the engine run! Also, I hope you have lots of fun with your grandkids!

 

[Brian Rupnow]

Tonight I took another kick at the can. The little engine is much happier with the new cam, but still refuses to settle in at a nice slow speed. It will run all day at mid range to high speeds, but it peters out and just quits at low speed. The internal friction and bearing friction has faded away to almost nothing with all of the running it has been doing, so its not dyeing out from frictional load. I'm running out of ideas here. I mix 2 cycle oil with my Coleman fuel to keep the Viton O-rings lubricated, and as I ran the engine tonight I'm getting a lot of oil dripping out of the cylinder on one side, very little out of the cylinder on the other side. I will pull the piston out of the leaky side on the weekend to see if perhaps the ring is damaged. (I do have a spare). I have good compression, but it does leak down if I turn it by hand and hold it on compression. I doubt very much that it is leaking at the valves, or I would be able to hear it hissing at the carb or exhaust pipe. There is so little that you can adjust on these engines. Basically it comes down to ignition timing or carb needle valve setting, and I have tweaked both of them in both directions with varying success, but still no nice idle. I am going to do a little research and see if I can find anything enlightening on ignition timing. I have always used about 15 to 20 degrees advanced timing on my hit and miss engines, but I'm not sure if that is right for an engine like this or not.

 

[Brian Rupnow]

I think this is as good as it gets for now. If I do add a bit more flywheel and it smooths out any more, I will post about it, but for now I think that the engine runs, it stays running and I can consider it a successful design.---Brian

 

[Brian Rupnow]

I discovered that my timing is far more extreme than I thought it would have to be. Turning it over by hand and stopping when the spark occurs, it is firing about 38 degrees before top dead center. I measured how far it was from the open end of the cylinder to the end of the piston skirt with my Vernier caliper/depth gauge at the point where the spark occurred, and then measured again when the piston was at top dead center, and there was exactly .125" difference. When I set up that distance on the CAD model, and measure the angle of the crankshaft, it still has to travel 38 degrees to rotate to bring the piston fully to top dead center.

 

[Philjoe5]

Brian,
That's fantastic. It runs great and without a massive flywheel to smooth out the ignition cycles!

Cheers,
Phil

 

[Brian Rupnow]

Philjoe--Looks are somewhat deceiving. There is a 4" diameter x 1.5" wide flywheel on the far end of the crankshaft---You just can't see it in the video. It sets directly below the gas tank.---Brian

 

[robcas631]

Brian,

I'm sure you will "fine" tune it! What you have created IMHO is a success!

 

[Brian Rupnow]

Thanks Robcas. Today I am doing some design work for a customer, getting a haircut, helping my wife clean house for a big grand-childrens birthday party, and in my spare time making an extra flywheel to add onto the back of the existing flywheel to see if it helps smooth things out a bit!!!

 

[Brian Rupnow]

So, just like the army when it goes to bed, this is the last post. It's been an interesting run, and although there has been some frustration, it has went pretty smooth for a 8 week long design, build, and run cycle. The only thing I would change on the drawings is to make the flywheel 1 1/2" thick, instead of what the drawing in the download package calls for. The carb I posted which was developed by Chuck Fellows will work, although it may require more fooling with to make it work properly than it is worth. Chuck has since abandoned that design and is moving forward on newer, better designs for carburation. I know that Gail in New Mexico is building this engine from my plans, only he is doing his at half of my original scale. Gail tells me that he has found no mistakes in the drawings, and he is adding a few of his own personal touches to it as he builds it. If you decide to build this engine, please let us hear about it, and please have fun.---Brian

 

[Brian Rupnow]

Youtube link to the final video.
[ame]http://www.youtube.com/watch?v=X82vlFazAuU[/ame]

 

[BaronJ]

Youtube link to the final video.
http://www.youtube.com/watch?v=X82vlFazAuU

Nice video Brian. Sure seems to run a little better.
I did notice that the points were sparking well. I thought the capacitor was supposed to suppress that.

 

[johnny1320]

Nice job Brian, I am thinking that with the engine being an oppossed piston engine that the compression ratio is higher than anticipated casuing you to need a heavier flywheel.

 

[Fluffy]

A great job Brian,
Thanks for the very interesting series. I have enjoyed it from start to finish, well done.
Regards,
Don.

 

[Brian Rupnow]

Liar Liar--Pants on fire---I did make one more video. I decided I couldn't spend the rest of my life demonstrating this engine with one hand hanging onto the throttle to keep it from running away with itself. So---This morning before all the birthday guests arrived I whittled out a brass bracket which attaches to the air intake side of my Traxxas carb (Loctite, as a matter of fact) with an idle adjusting screw and a tension spring to hold the throttle arm where I want it to be. Now I CAN make a video without my big ugly hand in the way. The engine is quite happy running at this speed, and if the gas tank wasn't so small I think it would set there and happily run all day.--The birthday party was enjoyed by all, our three kids, a daughter in law, a prospective son in law,and our three grandkids all managed to come home, much ice cream cake was eaten, candles blown out, and "Happy Birthdays" sang by all hands.

 

[Philjoe5]

Great job Brian. I can smell the exhaust fumes here. It was educational following along. When you post the plans I'll be sure to download a set for a future project

Cheers,
Phil

 

[Brian Rupnow]

Philjoe--You missed it--The plans are back at post #192. The only change to the posted drawings is the flywheel, which should be 3 times thicker than what is shown.