A concept that is in my head for a year almost.
My main focus would still be the large upgrade of the 55cc four stroke engine.
But to tinker and give the idea a place. I made a quick concept design of an engine which I not common have seen.
Opposed Stepped Piston Twin Cylinder Two Stroke OSP-T2
- Two stroke cycle. Uniflow scavaging (Transfer ports one side. Exhaust port other side).
- Opposed, two pistons each cylinder. Asymmetric timing pistons, 15 degree advance of exhaust piston. For early opening exhaust and closing. Would reduce fresh fuel/air charge goes directly into exhaust and "free" supercharging of early closing exhaust.
- Stepped pistons. Both pistons compress air/fuel mixture for other cylinder, no need to have conventional crankcase charging. Pre compression rate 1.4-1.5 to swept volume combustion cylinder.
- Lubrication by conventional four stroke methode by oil sump, pump and spray nozzles to cool and lubricate pistons/cylinders. Only 200:1 two stroke oil added to fuel to lubricate piston rings and piston skirt above oil scraper ring.
- Inlet before charge enter pump chamber will be an membrane. Also between pump section cylinder A to combustion chamber cylinder B and otherwise. Each cylinder feed by a carburator.
- Modular simple crankshaft with housing connected with HTD belts or gears.
It would be nice to use standard available piston rings. For now designed with 39mm combustion chamber rings. 54mm pump chamber (common 125cc four stroke engine). Smaller would be better, it will be now a quit large engine.
Given bore 39 mm or 40 mm and 40 mm stroke each crankshaft total of 80 mm stroke. Result in 96-101 cc each cylinder. Which would be great for aiming for smooth, reliable, useful torque. Max 6000 rpm.
Smaller would be better, maybe reducing stroke. Given pictures showed the current dimensions. Pistons are quit heavy 138 gram. Other option is to shorten them with other porting inlet of pumping chambers. Like the Wolf 500.
I see not this engine come to reality in next year. An concept that need to be boiled and cooked in slow time. I had also idea of an diesel engine. But than I dive the depth of small injector and fuel pumps.
Feel free to give comments!
Stepped two stroke engine from Bernard Hooper.
http://www.bernardhooperengineering.co.uk/opads.htm
http://www.bernardhooperengineering.co.uk/mcycle.htm
After some modeling I created an animation of concept. (ignore the transfer port positioned to each other, they need to be routed to other cylinder pump chambers)
https://www.youtube.com/watch?v=OttQQxW6rVc
And here a video of hobby prototype opposed two stroke engine
https://www.youtube.com/watch?v=2cnoXsDFDHo&list=LL&index=2
