A work of pure genius! - Brilliant "Revetec" Engine

[revetec]

Pneumatic: We have used helical and spur gears previously. Nothing in the geartrain has changed in layout or design. We have not experienced any gear noise since our last gearset design and the efficiency losses through the geartrain are marginal compared with our gains.

Cheers

[pneumatic]

Ok. I had noticed spur and helical combination on the previous engines.

The only difficulty with that engine in a car is the center of gravity and engine height is quite high compared to the centreline of the output shaft.

So to take advantage of the engine shape you would really need a custom transmission with a low input shaft, and then run a small diameter multi-plate clutch flywheel combo?

Do you have any plans for this area?

[revetec]

The height is not a problem. The engine is actually shorter than conventional inline engines. The engine is only 470mm from the top of the engine to bottom of sump. Output shaft to bottom of sump is about a standard distance :-)

[pneumatic]

Ok, you must have a real deep relatively empty sump like a Subaru

When people stick the Subaru motors into VW's or rally cars they cut anything up to 85-100mm out of the sumps.

I think they have such a deep sump to stop the oil sloshing around behind the horizontal pistons when the car is cornering hard, or even when the car is parked on a side angle. VW's (older flat 4 VW's) have shallower sumps, after you park them on a side angle and then start them up they blow smoke (because the sump oil actually spills into behind the piston and seeps past the rings while the car is parked).

The X4 Revetec might notice a similar thing on the bottom 2 pistons, but not from sump oil, just the small amount in the cylinder at the time (which won't be much). I doubt it will be noticeable.

[revetec]

We are using total seal rings so any oil will be pushed back to sump from the cylinders on cranking. This engine is for an aircraft so it requires a deep sump. We have got this engine so compact....I'm very happy with it.
Cheers :-)

Revetec Latest News...the X4

[santostripoli]

Pneumatic

You make references to the packaging effeciencies of the engine in addition to its weight reduction and note that you can not see the mechanical effeciencies. This is obvious, given that we have not been given test results.

However, even if the engine is capable of offering the same power and torque as per a conventional engine, the X4 is still far more superior due to its weight advantage (power to weight ratio) in addition to its compactness; this all makes the X4 concept quite remarkable.

In todays day of age of making things smaller and weigh less this is a positive step.

If what Brad is saying is correct (whcih he will prove some time soon with official test results), this engine will offer
(1) torque and power delivery advanatges
(2) power to weight advantage
(3) packaging effeciencies

It ticks all the boxes for a new age engine.

Well done Brad, just keep us all up to date on the engine stats so that we can sit comfortable and watch this engine concept show its true merits.

Regards
Santos

[manolis]

A 500cc two stroke is not equivalent to a 1000c four stroke. That used to be a rule of thumb, and they used it for sizing the new capacity when motogp went from 500cc two-strokes to 1000cc four strokes. They were getting around 200HP from the two strokes, and 250HP from the four strokes which aren't tuned as hard. A 500cc two stroke is closer to a 800cc four stroke in practice (my observations).

......

If the exhaust reed or valve is oval like the port, then it cannot swing open on a pin. It simply won't open. The port needs a recess for the reed to open into. Draw it in 3D and you will see what I mean.

And if you change to traditional reeds, then you won't get the "zero volume" at TDC on the outer pistons. It will also make the engine a little bigger in width too. Again, this area needs to be detailed to see what problems will arise.



I think it needs a start motor and battery. Manual starting is not marketable.

Pneumatic,

The cover of the ‘scavenging pumps’ is so thin because the pressure is very low. A blade of 2.5 to 3 mm thick is more than necessary. Onto this blade there are the ‘holes’ than form, with additional thin blades like razors, the one way valves. These thin blades will be taken by reed valves of conventional two stroke motors, i.e. from the reed valves of a motorcycle only the blades will be used not the case.
There are countless ways to make a one way valve of very short height and still streamlined. Normally the one way valve blades shown in the Flyer1.exe animation have to be nailed at one side on the scavenging pump cover plate, being at their ‘restore’ or ‘idle’ position closed (their own material is the restoring spring). This way the dead volume can be as small as desirable.


’500 cc two stroke is comparable to 800 cc four stroke’ is not a bad relation for the Junkers-PRE, given the four stroke lubrication and reliability of the Junker-PRE, the lightweight, the absence of cylinder heads etc.
But the ‘four stroke like’ lubrication, the built-in scavenging pumps with the minimized dead volume, the through scavenging, the reduced thermal loss and friction at the eliminated cylinder heads and the increased thermal efficiency due to slow piston motion during high pressure make me think the 1000cc Junker-PRE can make more than the 2000cc four stroke.
The bad reputation of the conventional two stroke is because the disadvantages the PRE comes to eliminate.
Yes, practice has to show whether the theory about PRE and Junkers-PRE is wrong. A prototype Junkers-PRE has to be made.
The usefulness of the discussion is to reject the project in the case something looks wrong in the first place. For instance, if Brad’s argument that ‘a long con-rod engine can never breath efficiently’ was correct, the four stroke PRE had to be rejected. If premixed lubrication was necessary in the Junkers-PRE, again this version of PRE had also to be rejected too. If PRE’s thermal efficiency was theoretically less than four stroke, again PRE project had to be rejected. Etc. Until now neither theory, nor experience can kill PRE’s idea. Future will show.
A hopeful thing about PRE is that it needs no new technology to be manufactured. What I mean is that we cannot make rollers for the GRECO crankless engine. If the conventional rollers are not good enough for such an application, forget GRECO. But we can use the piston rings of the Honda Civic VTEC as the piston rings of the Junkers-PRE. Or the blades from two stroke reed valves as the one way valves of the PRE. Etc. ETC. So a PRE engine could be built and operate into days without having hidden problems to be solved: I know a well equipped machine shop can built it in a few days, not in weeks.


Wankel has specific disadvantages that were never cured:
The extreme consumption caused by the attenuated combustion chamber which leaves no chance for acceptable thermal efficiency (the last model of Wankel in RX-8 consumes 1.2 l/hour at idling, a great step ahead compared to the 1.6 l/hour of the previous model RX-7 but still more than double compared to the typical engines)
the piston/rotor pressure ‘rings’ leakage
the two stroke lubrication
the thermal and cold regions on the engine walls


With the alternator at the lower end of one crankshaft and the oil pump at the lower end of the other crankshaft, the imbalance of power on the two crankshaft is not worthy to mention.


Take a look at the last plot I sent to this forum, not at the animation. In the plot the centers of the four synchronizing gears form something like Z, not like I. Keeping each one of the three pairs of intermeshing gears (i.e. the two left, the two middle and the two right) in constant distance, the mechanism is not affected by the change of the distance of the two crankshafts. But such complication is more than necessary. The small distance of the two crankshaft keeps the absolute thermal expansion acceptable.
As for the starter, it is a luxury. To make easier the starting and the take-off for the rider, a pillar (column) on the ground can be used to secure, to check and to start (manually) the Flying Machine. Then the rider is secured to the Flying Machine and leaves the ground and the pillar.

Thanks
Manolis Pattakos

[revetec]

Pneumatic

You make references to the packaging effeciencies of the engine in addition to its weight reduction and note that you can not see the mechanical effeciencies. This is obvious, given that we have not been given test results.

We have given the results in the power/torque graph posted. We are producing almost the same torque as the Hayabusa engine at about half the RPMs which greatly saves fuel. Everone did notice that didn't they?

However, even if the engine is capable of offering the same power and torque as per a conventional engine, the X4 is still far more superior due to its weight advantage (power to weight ratio) in addition to its compactness; this all makes the X4 concept quite remarkable.

In todays day of age of making things smaller and weigh less this is a positive step.

If what Brad is saying is correct (whcih he will prove some time soon with official test results), this engine will offer
(1) torque and power delivery advanatges
(2) power to weight advantage
(3) packaging effeciencies

It ticks all the boxes for a new age engine.

Well done Brad, just keep us all up to date on the engine stats so that we can sit comfortable and watch this engine concept show its true merits.

Regards
Santos

Thanks Santos :-)

[revetec]

Manolis:

I don't know much about flying aircraft but I imagine that this flying machine would need to operate similar to a helicopter. You need to pitch the blades in a twin rotor helicopter in any direction to manuvre around. This makes things more complex...especially the controls on such an idea.

Plus with this design...If it stops you'll die.

Far better to strap an engine to your back with a parachute.

It's definitely one thing I wont be having a go of.

[pneumatic]

We have given the results in the power/torque graph posted.

Which power/torque graph was that, and which engine was it from?

The only graph I saw didn't seem to be comparing apples with apples.

Manolis, Rotaries do not use two-stroke lubrication, and have perfectly reliable apex seals these days.

I didn't follow what you were saying about adapting reed valves. Perhaps you will need to draw a diagram.

[revetec]

This one... Which is correct because it is running 2 strokes of the piston per 360 degrees of rotation of the output shaft.

Remember that these are two vastly different engines. Our one was setup for automotive use. But we were still delivering more power at our test RPMs. Higher revving engines will come in the future but currently they are not our target market.



We are producing almost the same peak torque as the Hayabusa engine at about half the RPMs which greatly saves fuel. Everone did notice that didn't they?

[pneumatic]

You can't compare those two, they are like chalk and cheese. I used that graph to show that you can't compare an engine that is essentially internally geared. That was when the revetec information was saying 6 strokes per 360 crank revolution, that is why I made that comparison, because if the revetec was doing that many strokes than it was compariable in piston and valve train speed to a hayabusa.

But as has been said, all that Revetec info has been superseded, so the discussion was no longer valid.

All that graph shows is the hayabusa is a far more high performance motor making huge amounts more power.

The Revetec needs to be compared to something of a similar state of tune. With the info available at the time that appeared to be a Hayabusa, but apparently it isn't.

[revetec]

I'll post some target market comparisons when I have time :-)

[santostripoli]

Pneumatic, one tick though, if the Revetec engine produces a significant torque value at a lower rpm, what does it matter what enegine it is compared to? Whether it is compared to a Hayabusa or a jet engine, the Revetec engine produces a high amount of torque and does so with an engine that weighs less and is smaller.

I have stated in the past that I am not an engineer, I have an interest in cars. My interpretation of this Revetec engine is that it has similar characteristics to a diesel engine (in the sense that it has low down torque) however unlike Diesel it can run on unleaded petrol therefore making it cleaner and friendlier to the environment.

Brad, you said you may have some results by Xmas, so for now all we have is the table that charts the power and torque of your prototype engine that was NOT developed for performance, just a proof of concept.

Pneumatic, do you not agree that the torque figure is somewhat impressive?

[pneumatic]

Pneumatic, one tick though, if the Revetec engine produces a significant torque value at a lower rpm, what does it matter what enegine it is compared to?

Yes it does matter. A lot of people don't understand horsepower and torque, and what it all means.

Where an engine makes it's peak torque is dependant on how it is tuned. If it is tuned for high performance it makes it's torque high in the rev range. If it is tuned for reliability and drivability then it makes the torque much lower.

The higher you can keep making the torque in the rev range, the more power you get.

The engine size and efficiency effects the torque. And as far as peak torque goes, the Hayabusa makes more (and it is a smaller motor).

You see there is a negative to making torque low in the rev range, and that is that you need to select a taller gear to run at the same speed. And torque is effected by gear ratio's, therefore the issue gets confused.