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Old 01-12-2017, 12:11 PM   #11
lohring
 
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Thanks. For some reason I didn't realize that the seals were in the outer case. However, everything I said about an accurate and smooth surface is still true. It just needs to be on the inner element. It may be easier to get this finish and the seals may wear in well enough against say a cast iron inner element for a demonstration prototype. Production engines would need a better solution for long life. I'm looking forward to seeing your prototype. This could be a very promising design.

Lohring Miller


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Old 01-12-2017, 09:56 PM   #12
Buchanan
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EDM cutting leaves a porous hardened surface, if you propose to use an alloy steel this hardened surface will crack when bent. Do you have a miraculous post bend finishing process that will remove the cracks and produce the smooth non abrasive surface required for a long lasting oil and pressure seal?


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Old 01-13-2017, 02:15 PM   #13
manolis
 
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Hello Buchanan

You write:
“EDM cutting leaves a porous hardened surface, if you propose to use an alloy steel this hardened surface will crack when bent. Do you have a miraculous post bend finishing process that will remove the cracks and produce the smooth non abrasive surface required for a long lasting oil and pressure seal?”


The porous hardened surface is a good characteristic (it keeps lubricant etc).

There are some “miraculous” multi-axis wire EDM machines by which you can cut accurately an already bent sheet of metal, and so you bypass the problem mentioned.

Such EDM machines cut accurately bevel gears etc.

Thanks
Manolis Pattakos
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Old 01-13-2017, 02:15 PM   #14
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Hello Lohring

Talking for the seals of the Wankel, LiquidPiston and PatWankel, here are some interesting, I hope, details:

With their different arrangement of the seals, LiquidPiston creates new “sealing” problems (not existing in the Wankel engine).

According the following drawing (from the patent of LiquidPiston):



there is an immovable “peak” seal, 825, which abuts on the cylindrical working surface 202R of the inner body,

there is also a side seal, 801, in a groove of the inner body, which follows the motion of the inner body.


A LiquidPiston side seal, as the seals of the conventional Wankel, undergoes a substantially variable (in direction and in amplitude) acceleration around the seal and around the cycle.

Here is the inertia force an apex seal of a conventional Wankel applies to the epitrochoidal casing :



(at some angles the inertia vectors outwards, at some other angles it vectors inwards),



and here is the acceleration required in order a point at the top edge (the outmost edge) of the side seal of a LiquidPiston engine to follow the motion imposed by the spinning / orbiting rotor:



and here it is shown, for comparison, the acceleration required in order a point at the innermost edge of the side seal of a LiquidPiston engine to follow the motion imposed by the spinning / orbiting rotor:



The following drawing helps in understanding the previous plots (the red circles show the path the outmost edge of the side seal follows, the cyan circles show the path the innermost edge of the side seal follows) :



R1 is the "crank-arm" of the eccentric shaft, R2 is the distance of the specific point of the seal from the center of the rotor.


The gaps between the apex-seals /corner-seals / side-seals of the Wankel engine are gaps between bodies moving together (they are all inside grooves / holes of the rotor).


In the LiquidPiston, the side seal moves together with the inner body (the rotor), while the rest seals are stationary.
Any clearance of the synchronizing gear-wheels,
and any clearance in the bearings supporting the rotor (the bearing by which the rotor is rotatably mounted on the eccentric shaft and the bearings by which the eccentric shaft is rotatably mounted on the immovable casing),
and any “play” of the side seal inside its groove,
and any flexing of the eccentric shaft (or power shaft) due to inertia and/or combustion loads,
all are added to the required gap between the side seal and the “button seal”.
Note: around each chamber there are four such gaps.

The result is even more gas leakage than in the conventional Wankel.


Now think how the seals are arranged and are working in the PatWankel.

In the PatWankel with the working surface on the inner body, all the seals are inside grooves made on the outer body and perform a pure rotation (during a cycle, the inertia force remains constant in direction and constant in amplitude). Etc.


By the way, without an eccentric shaft, there is no flexing of the eccentric shaft.
Without inertia loads on the bearings, the clearance between the inner and the outer bodies is smaller.
Without eccentric shaft, no balance webs are required.

Thanks
Manolis Pattakos
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Old Yesterday, 09:21 AM   #15
manolis
 
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Hello all.

Here are the specifications of the XMv3 of LiquidPiston:



According the famous MIT university, the DARPA and the more than famous Shikorsky company, it is a promising engine design.


Here are a few calculations based on the above specifications and on the way the XMv3 operates.

They are required two only rotations of the eccentric shaft in order a combustion to take place in each working chamber (of the three existing). This means 1.5 combustion per eccentric shaft rotation.

In comparison, in a Wankel they are required three eccentric shaft rotations in order a combustion to take place in each working chamber (of the three existing). This means one only combustion per eccentric shaft rotation.

More combustions per shaft rotation sounds great.

However there is a significant side effect:
In the Liquid Piston the synchronizing gearing is heavily loaded by the combustion pressure.
Depending on the angle of the eccentric shaft, the teeth of the two gearwheels take a good percentage of the force acting on the “rotor” due to the high pressure gas.

In comparison the synchronizing gearing of a Wankel runs unloaded for as long as the engine runs at constant rpm.


At 10,000rpm the power output of the XMv3 is 3PS.

According the previous, 10,000rpm means 5,000combustions per working chamber of the XMv3.

Unless I am wrong, this is equivalent to a 70cc 4-stroke reciprocating piston engine operating at 10,000rpm (because it also burns 5,000 times per minute the mixture contained in a chamber of 70cc).

A good 4-stroke makes more than 100mN of torque per lit (1,000cc) of displacement (even at the peak power revs).
This way, a torque of 7mN from a 4-stroke 70cc reciprocating piston engine is reasonable.

7mN at 10,000rpm means a power output of 14*7mN*10= 10PS.

This is more than 300% of what the XMv3 makes.

Do I miss something?

Thanks
Manolis Pattakos
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Old Today, 05:46 AM   #16
manolis
 
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Hello all.

Here is the inner body of an unconventional rotary engine and the way to cut it in a lathe:



(instructions in how to see it stereoscopically at http://www.pattakon.com/pattakonStereoscopy.htm )


At operation it would be like:




It comprises two only parts, each spinning at constant speed about its own fixed axis (which means perfect balancing without any balance webs).
The eccentric shaft of the Wankel RX8 and of the LiquidPiston rotary engines is eliminated.
The power / torque is delivered by a shaft / extension of the inner body:



There are two combustions per shaft rotation (i.e. as much as in a Wankel with two rotors).

The big difference is in the sealing.

More about how this engine (PatWankel) operates are at http://www.pattakon.com/pattakonPatWankel.htm


Regarding the machining of the working surface shown in the first animation:

On the chock of a lathe it is secured eccentrically a shaft.
The red gearwheel is secured immovable on the lath bed.
The body with its gearwheel (white) is rotatably mounted on the shaft.
As the chock rotates, the body to be machined performs a combined motion (it spins about the shaft and it orbits together with the shaft).
Given the shape of the seals to be used (the simplest form? the circular), the cutting tool has to follow a specific “path” (like half circle, for instance) in order to create / form the working surface on the part (the working surface is whereon the seals will abut and slide during operation; the seals are mounted in grooves made on the outer body).

In case of seals having simple form, even a conventional (not CNC) lathe can be used.

Similarly for the honing / polishing.


Thoughts?

Objections?

Thanks
Manolis Pattakos


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