manolis wrote:With the proper balance webs on the crankshaft and the proper first-order counter-rotating balance shaft the balancing of the inertia moment of the even firing 2-stroke parallel twin is perfect along all crankshaft angles (i.e. the unbalanced inertia moment is zero for every crankshaft angle).
I.e. the first order counter-balance shaft is the absolute cure for the unbalanced inertia moment of an even firing parallel-twin 2-stroke. If there is interest, I can further explain it.
What is left unbalanced is a second order inertia force and a second order inertia torque. They are half (because there are only two pistons) as compared to the inertia force and inertia torque of a four-in-line even firing 4-stroke.
Manolis Pattakos
@ Manolis (and uniflow)
thanks, and yes, I can now see this
and remember the Yamaha XS 500 has it first, around 1972 - but was a failure in sales
(also their very different 750 twin which had very different counterbalance shafts)
ie Yamaha offered a lesson to the other manufacturers, they started their various counterbalancer systems around 1977
If you want to describe the “vibration-free quality” of a parallel-twin even firing 2-stroke with a first-order counter-rotating balance shaft, you can say that it vibrates** as the in-line-four even-firing 4-stroke (same bore and stroke, same effective con-rod length).
** “vibrates” is described by the frequency and the amplitude of the oscillations of the “free” engine.
Hello Uniflow.
You write:
“Make no mistake the 582 vibrates it's just that we have learnt to live with it. The difference in my 700 twin is night and day.”
With the additional balance shaft,
your 700 twin engine gets rid of the inertia moment achieving a running smoothness (vibration-free) that, as compared with the Rotax 582, is the “day and night”,
in expense of additional cost / weight / complication,
and in expense of slightly increased friction and fuel consumption.
The added weight (balance shaft, gearing, additional fuel required to cover the added friction and to lift the added weight) is not a big deal for most applications, but for an aero engine?
However, your engine / gyro still suffers from strong unbalanced inertia and combustion loads:
There is a free second order inertia force.
There is a free second order inertia torque.
There is a strong combustion torque during compression / expansion that requires a reaction torque from the frame of the gyro.
and think their difference from the conventional aero engines (like the Rotax 582, for instance, or like the Rotax 912/ 914 / 915 boxer 4-strokes).
They do not need balance shafts (and the crankshafts balance webs are substantially more lightweight because they don’t need to balance the reciprocating masses).
Their balancing is no less than perfect, including all inertia and combustion loads.
The frame of the airplane or gyro or helicopter or flyer they are mounted on, is rid of any reaction torque (which make the flight a lot more safer) and of any kind of vibrations.
The frame wherein they are mounted on, gets more lightweight.
The two opposed pistons share the same combustion chamber (and instant pressure).
Manolis, you seem to forget, I've built three uniflow engines now and run them, one for many hours in a jet boat, so I do know a little about their behaviour, vibration free, low fuel consumption and in the case of my engine simple crank case pumping. Also I designed a prop system that mimmics the Kaman (helicopter) rotors utilising two main idler gears in the crank joining gearbox, angled intermeshing props. Loads on to the engine frame would be minimised.
BUT, I don't have the money (or time) to put into serious development for production and there seemed to be real lack of enthusium for somthing so different. The 700 twin uses standard tech (but modern compared to the Rotax), looks "normal" and out performs a Rotax in terms of vibration, power, weight and with semi direct EFI will out perform on fuel consumption. The gyro needs a separate shaft anyway running up the engine to opperate the pre rotator, so it's weight that will be there anyway. Part of the reason the 700 shakes so bad is that the crank centers are far appart so as to not compromise on the transfer port shapes and sizes.
I appreciate and applause your efforts, work, skills and persistence.
Having said that,
are there presented somewhere (say in a web site) your various designs, projects and prototypes, drawings, patents and published patent applications?
If not, why don’t you present here, in this Forum, your projects and ask for the opinions / objections / remarks of the rest members?
In case you want to create your own web site, I can help you for free.
HCCI sort of running, first attemt, running on CRC (light oil). No spark plug or ignition sorce at all. Relies on a small piston in the head ( running at twice crank speed, only 8mm stroke) raising compression at just the right time to create combustion ( pre mixed fuel air, HCCI, unlike a Diesel). Test rig is just a bit too rough, since this run I've managed to have an engine runaway uncontroled and crack the Yamaha main piston due to excess oil in the crank case being flicked up into the combustion space causing hydraulic lock. I have a better idea I'll try in the next few weeks, real work starts for me tomorrow so that will slow play time down.
Manolis I sort of do have a platform, Kiwi Biker forum, Foundry thread, I post most stuff there. You are a member keep an eye on it.
I see you “apply” all existing (and future) safety rules and regulations during the test: necked hands, no gloves, room full of flammable fumes etc.
What I am saying is: be more careful in safety matters to reduce the possibility of accident / injury.
What if you replace the auxiliary piston by the smallest Diesel injector? With the diesel fuel (less than, say, 5% of the total fuel) used to create a big number of sparks into the compressed mixture, are things too different?
It looks that if the conditions just before the injection of the small quantity of Diesel Fuel are close enough to those required for HCCI combsution, a part of the combustion will be HCCI.
Whether it is HCCI, or not, what counts is the thermal efficiency and the emissions.
I see you “apply” all existing (and future) safety rules and regulations during the test: necked hands, no gloves, room full of flammable fumes etc.
What I am saying is: be more careful in safety matters to reduce the possibility of accident / injury.
What if you replace the auxiliary piston by the smallest Diesel injector? With the diesel fuel (less than, say, 5% of the total fuel) used to create a big number of sparks into the compressed mixture, are things too different?
Thanks
Manolis Pattakos
Thankyou for your concern, yes I could be a little less blase on safety. I was at least wearing safety glasses
I want to run this test engine with only compression for ignition, nothing else. This test run was very crude (as you can see) but I have some more refinements to make to get some control. I'm just testing out some possibilies.
According the Internet, the Ryger 125 REVO has square design (bore: 54mm, stroke: 54mm), with a peak power of 70bhp delivered at 17,500rpm (which means 28Nm / 38 Lb-Ft torque at 17,500rpm), and the ability to rev reliably till 30,000rpm.
The OPRE-Tilting design:
is an over-over-square Opposed-Piston Pulling-Rod engine.
With 60mm bore and a combined stroke of 2x22=44mm (same “bore to stroke” ratio with the first OPRE-Tilting prototype at http://www.pattakon.com/pattakonTilting.htm ) the single-cylinder OPRE-Tilting engine has 125cc capacity.
At 17,500rpm its mean piston speed is only 12.8m/sec (Ryger’s REVO: 31.5m/sec).
At 30,000rpm its mean piston speed is 22m/sec (Ryger’s REVO: 54m/sec).
With only 22m/sec mean piston, the OPRE-Tilting 125cc can rev at 30,000rpm “for ever” and it can breath there efficiently.
Besides, the Pulling-Rod architecture increases for some 35% the piston dwell at the Top Dead Center, enabling a more efficient burn of the mixture (more at http://www.pattakon.com/pattakonOPRE2.htm )
According the previous, and supposing the Tilting has the same torque with the Ryger REVO, the OPRE-Tilting will provide at 30,000rpm 120bhp (i.e. about 70% more).
Do I miss something?
PS. Are the Opposed Piston engines OK with the existing Kart regulations?
