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[QUOTE=manolis;675046]"Mathematics cannot lie.” [/QUOTE]Who told you this? Mathematics can say anything you want it to. Math is a simplification of the "real thing" it is NOT the real thing. Lets say I did a proof using Newtonian physics for the orbit of mercury. Then when data showed my predictions wrong I said "mathematis cannot lie." Well the math itself is not wrong but rather the assumptions under it. Relativity is necessary to calculate some things.
Similarly, when you claim to determine the dimensions of someone else's engine by assuming its the simplest possible design, you make a fool of yourself. When you try to "prove" that your engine is perfectly balanced without taking the second or higher order vibrations into account and without using any kind of real modeling, you make a fool of youself.
Sure your math is good. Congratulations on passing 8th grade geometry.
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Compression ratio is calculated by (we use this formula when buildng our Type 1 engines with flat top pistons):
(Head cc + Deck cc + 1 Cylinder volume) ÷ (Head cc + Deck cc) = Compression Ratio
Total Displacement:
BORE (mm) X BORE (mm) X STROKE (mm) X 0.0031416 = Engine Displacement in CC's
Your calculation is nothing more than a GUESS (I know what the stroke & bore is).
What did you work out the head cc is?
What did you work out the deck cc is?
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[quote=shane_trikes;675515](I know what the stroke & bore is)?[/quote]damn you !!! THe rest of us only know 50% of that .....
...... the BORE ( in this thread ) :D
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[QUOTE=Bob;675418]Who told you this? Mathematics can say anything you want it to. Math is a simplification of the "real thing" it is NOT the real thing. Lets say I did a proof using Newtonian physics for the orbit of mercury. Then when data showed my predictions wrong I said "mathematis cannot lie." Well the math itself is not wrong but rather the assumptions under it. Relativity is necessary to calculate some things.[/QUOTE]
a great example of maths lying is taylor series, its an approximation not exact. much of engineering is simplification and moddeling of an ideal situation. Funny thing is maths is usefull when it lies.
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[QUOTE=jediali;675537]a great example of maths lying is taylor series, its an approximation not exact. [b]much[/b] of engineering is simplification and moddeling of an ideal situation. Funny thing is maths is usefull when it lies.[/QUOTE]
I would argue that should read: [quote][b]all[/b] of engineering is simplification...[/quote]
I think you would be hard pressed to find any model of a real system that is [U]perfectly[/U] accurate, much less a highly complex system with dependency across multiple physics disciplines.
My friend once told me “the real world never lies” and that is possibly the best engineering advice I have ever gotten.
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According Revetec’s X4 specifications:
“Some of the X4 Engine Features:
. . .
9:1 compression ratio (1.6mm head gskt) Current;
9.5:1 compression ratio (1.2mm head gskt);”
There is no mention for piston replacement / different pistons.
For any other engine these specifications just say that reducing the head gasket height from 1.6mm to 1.2mm, the compression ratio changes from 9:1 to 9.5:1.
Revetec wrote:
“I'll give you an example:
If I had an engine with 9:1 compression ratio, and put a high top piston in it and changed the compression ratio to 10:1. The engine capacity is the same, the head gasket is the same thickness. So you cant work it out.”
When the “high top piston” of Revetec’s example replaces the normal piston of X4, the compression ratio becomes 10:1.
In order to reduce the compression ratio back to the initial 9:1 we can:
either use a thicker head gasket, with gasket height (1.6+x)mm,
or remove some material from the cylinder head keeping the 1.6mm head gasket unchanged.
With the “high top piston” in the X4 / 9:1 compression ratio engine, the reduction of the height of the head gasket for 0.4mm gives a new compression ratio of 9.5:1, in both cases.
In the first case the gasket will have a new height of (1.6+x-0.4)mm.
In the second case the head gasket will have a height of 1.2mm.
I.e. neither the shape of the piston crown nor the shape of the combustion chamber play any role in the calculations.
Thanks
Manolis Pattakos
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Shane Trike wrote:
“Compression ratio is calculated by (we use this formula when buildng our Type 1 engines with flat top pistons):
(Head cc + Deck cc + 1 Cylinder volume) ÷ (Head cc + Deck cc) = Compression Ratio
Total Displacement:
BORE (mm) X BORE (mm) X STROKE (mm) X 0.0031416 = Engine Displacement in CC's
Your calculation is nothing more than a GUESS (I know what the stroke & bore is).
What did you work out the head cc is?
What did you work out the deck cc is?”
The “Total Displacement” formula is correct only for 4 cylinder engines.
In the rest cases the correct Total Displacement formula is :
(number of cylinders/4) x BORE (mm) X BORE (mm) X STROKE (mm) X 0.0031416 = Engine Displacement in CC's
In the “Compression Ratio” formula, the ( Deck cc + Head cc ) is called the Dead_Volume cc.
Changing the head gasket from 1.6mm to 1.2mm:
The 1 Cylinder volume remains unchanged.
The Dead_Volume is reduced by the Dead_Volume_Diff cc quantity.
The Dead_Volume_Diff cc equals to :
Dead_Volume_Diff cc = BORE (mm) X BORE (mm) X 0.4 (mm) X 0.0031416 / 4
(1.6mm –1.2mm = 0.4, and the dead volume decreases – with the new 1.2mm head gasket – as much is the volume of a cylinder with diameter the gasket hole diameter – which equals to the Bore - and height the reduction of the gasket height).
1 Cylinder volume = BORE (mm) X BORE (mm) X STROKE (mm) X 0.0031416 /4
So, the ratio of the (DEAD_Volume_Diff cc) to the (1 Cylinder volume) is:
Dead_Volume_Diff cc / 1 Cylinder volume = 0.4 (mm) / STROKE (mm),
i.e. 1 Cylinder volume = Dead_Volume_Diff cc * ( STROKE / 0.4 (mm) )
and so STROKE = 0.4 mm * 1 Cylinder volume / Dead_Volume_Diff cc
9:1 is the initial compression ratio (with the 1.6mm head gasket), according X4 Revetec specifications, so:
(Dead_Volume cc + 1 Cylinder volume) ÷ (Dead_Volume cc) = Compression Ratio = 9.0
This is equivalent to:
9.0*(Dead_Volume cc)=(Dead_Volume cc + 1 Cylinder volume)
which is equivalent to:
1 Cylinder volume = 8.0*(Dead_Volume cc), i.e. the volume of the cylinder is eight times the Dead_Volume.
But 1 Cylinder volume is 2400 cc / 4 = 600 cc, so Dead_Volume = 75 cc.
Replacing the 1.6mm head gasket with the thinner one of 1.2mm, the compression ratio goes from 9:1 to 9.5:1 according Revetec’s X4 specifications. The dead volume is now ( Dead_Volume cc – Dead_Volume_Diff cc ), so, according the Compression Ratio formula we have:
(Dead_Volume cc – Dead_Volume_Diff cc + 1 Cylinder volume) ÷ (Dead_Volume cc – Dead_Volume_Diff cc) = New Compression Ratio = 9.5
This is equivalent to:
9.5*(Dead_Volume cc – Dead_Volume_Diff cc)=(Dead_Volumecc –Dead_Volume_Diff cc + 1 Cylinder volume)
and replacing the (1 Cylinder volume) quantity by the 8.0*(Dead_Volume cc) as calculated previously, the last equation becomes:
9.5*(Dead_Volume cc – Dead_Volume_Diff cc)=(Dead_Volume cc –Dead_Volume_Diff cc + 8.0*(Dead_Volume cc))
which is equivalent to:
0.5*Dead_Volume cc = 8.5*Dead_Volume_Diff cc
which is equivalent to:
Dead_Volume_Diff cc =(1/17)*Dead_Volume cc =(1/17)*75 cc = 4.41 cc
The stroke was calculated previously as
STROKE = 0.4 mm * 1 Cylinder volume / Dead_Volume_Diff cc
so
STROKE = 0.4 mm * 600 cc / 4.41 cc = 54.4 mm
The Total Displacement formula gives :
(number of cylinders/4)*BORE (mm) X BORE (mm) X STROKE (mm) X 0.0031416 = Engine Displacement in CC's, i.e.
(4/4)*BORE (mm) x BORE (mm) X 54.4 (mm) x 0.0031416 = 2400 cc,
i.e. BORE *BORE =14043.05, so the bore is : BORE = 118.5 mm
As you see, there is no “GUESS” in the above simple calculations.
Do you know a third part to pay to prove me wrong?
As you see, the third party was not necessary to verify the absolute balancing (as absolute as the Wankel Rotary engine) of the GRECOi3.
What I wrote and repeat here is:
Either the bore x stroke is 118.5mm x 54.4 mm or the specifications of X4 are not correct as given.
It seems that what I had to go through, until to convince for the absolute balance of the GRECOi3, I have to go through again to prove the obvious (interrelation of gasket height and compression ratio).
Looking back, it is more funny.
I had to use the most stupid argument, ever : the divided balance webs covering less than 180 degrees around the shaft.
Where mathematics, physics, geometry and trigonometry failed, this stupid argument finally worked.
In any case, what counts is that now the GRECOi3 has the “certificate” of being the only three cylinder reciprocating engine as perfectly balanced as the Wankel rotary and the best conventional V12.
Thanks
Manolis Pattakos
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It was written:
“When you try to "prove" that your engine is perfectly balanced without taking the second or higher order vibrations into account and without using any kind of real modeling, you make a fool of youself.
Sure your math is good. Congratulations on passing 8th grade geometry.”
It is as wrong as it gets.
The inertia forces, inertia rocking couples and inertia torques of the GRECOi3 have been calculated taking into consideration EVERY order of vibrations and not only the first order.
As shown in the relevant excel, the cams on the two counter-rotating shafts have profiles that provide pure sinusoidal (of first order) piston travel versus shaft angle. The formula for the geometric construction of such cam lobes is in the pattakon web site (when I add links or plots they are deleted, so search).
We start with cam-lobes providing pure sinusoidal piston motion.
Then the excel spread sheet, based on the piston travel and the revs, calculates the piston speed (which is also pure sinusoidal of first order).
Then the excel spread sheet, based on the piston speed calculates the piston acceleration (which is also pure sinusoidal of first order).
Then the excel spread sheet, based on the piston acceleration, calculates the inertia force necessary to be applied on the piston to cause the calculated piston acceleration (again pure sinusoidal of first order).
Then it is calculated the sum of the inertia forces from the three reciprocating pistons (120 deg phase difference from piston to piston). Sum: absolutely zero.
Then it is calculated the inertia rocking couple due to the offset of the pistons. It is again a pure sinusoidal of first order.
Then it is calculated the inertia rocking couple from four balance webs secured on the counter-rotating shafts. It is also a pure sinusoidal of first order.
Then the sum of the rocking couples is calculated and is absolutely ZERO.
The higher order vibrations are not “simplified”.
In the balance calculation of the GRECOi3 any order of inertia vibration is taken into consideration.
The higher (than first order) vibrations do not exist.
The architecture of the GRECOi3 does not generate such vibrations.
This is why I keep saying that only Wankel rotary and some good conventional V-12 can compare to the perfect balancing of the GRECOi3.
All the GRECOi3 vibration analysis is based on simpler than 8th grade geometry.
I try to understand why everybody is so much confused with so simple things.
You have the posts, you have the links, you have the plots. Read again and again. The balance program is invaluable for such study.
Thanks
Manolis Pattakos
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Manolis , as was said before ... stop kidding yourself with the excel simplifications. Get a decent analysis done and you'll perhaps realise why rotating and reciprocating REAL WORLD objects cannot be "based on simpler than 8th grade geometry".
You've read too many books and think the world is that simple :(
Nobody here is confused. You are as you lack engineering background to realise how inane your comments are.
You're simple math is not considering tolerances - nothing can be a perfect fit - nor material twists.
So you are 100% wrong in claiming that the higher order have been considered and don't exist.
It's THAT simple... so hence none of your other "facts" can be relied on. Sorry, go back to school.
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[QUOTE=manolis;675919]
What I wrote and repeat here is:
Either the bore x stroke is 118.5mm x 54.4 mm or the specifications of X4 are not correct as given.
[/QUOTE]
for everybody else following this thread, Manolis's calculation of the X4's bore & stroke is wrong.
I looked through your calculations and I immediately picked out one of YOUR incorrect assumptions.
Hey Matra, I hope Brad can spice up this thread and break the boredom with some new data shortly. We have a new trike waiting for the X4 once it has finished its dyno testing phase.
We are looking forward to the duration testing phase, Cairns to Alice Springs (Ayers Rock) upto Darwin, back through Mt Isa back to Cairns (just one leg). This will see long periods of wide open throttle and extreme conditions. This sort of trip would be around 10,000km. Unfortunately (unconfirmed yet) that the Northern Territory Government have now imposed a speed limit on all highway's so we will have to ride at a reasonable speed (this highway was used for one of the Cannonball Run race series).
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[QUOTE][QUOTE=shane_trikes;676253]for everybody else following this thread, Manolis's answer for the bore & stroke of the X4 is wrong.
I looked through your calculations and I immediately picked out one of YOUR incorrect assumptions.
Hey Matra, I hope Brad can spice up this thread and break the boredom with some new data shortly. We have a new trike waiting for the X4 once it has finished its dyno testing phase.
We are looking forward to the duration testing phase, Cairns to Alice Springs (Ayers Rock) upto Darwin, back through Mt Isa back to Cairns (just one leg). This will see long periods of wide open throttle and extreme conditions. This sort of trip would be around 10,000km. Unfortunately (unconfirmed yet) that the Northern Territory Government have now imposed a speed limit on all highway's so we will have to ride at a reasonable speed (this highway was used for one of the Cannonball Run race series).[/QUOTE][/QUOTE]
Brad
Although we are all anxious for results, there is no rush. Take your time & get it right; I am sure we are all able to wait a little longer for the results. You have impressed us all on your delivery timing for this X4 engine however the next steps are key and critical... if it takes 3-4 months so be it.
Manolis etc will just have to wait... without wanting to sound too corny ... keep the eye on the prize...
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[QUOTE=santostripoli;676277]if it takes 3-4 months so be it.[/QUOTE]
And that should give Manolis heaps of time to get the proper software and provide everyone with decent modern day data for his engine rather than relying on Pythagoras, Archimedes and Aristotle for his flawless mathematical theories.
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CHeers Shane .... needing a rider for that test run ? I'll pay my flight :D
Even better ..... the world's biggest road race bike event. Bring it over to the Isle of Man. UNRESTRICTED speed limits on roads out of towns. I can put you and the trike up for the duration fo the TT -- guaranteed LOTS of media coverage if you came :)
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Manolis: You don't know what my bore and stroke is. So you don't know the volume of the head gasket. You don't even know if the head gasket is the same size as the bore. You know nothing...so stop guessing with excel, or keep guessing and make yourself look more foolish. Shane knows the bore and stroke of the X4 and knows you are wrong.
Everyone: I will release details on the X4 over the coming months. A representative of GTM trikes will be coming to see the X4 in about a weeks time. At that point they may comment more on our X4.
I will post a video soon on our website.
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So, the new information is that the head gasket hole is not equal to the bore.
Let us calculate the effect of the gasket hole diameter to the BORE and STROKE of the Revetec X4 .
Let call R the ratio of the GasketHoleDiameter to the BORE, i.e. GasketHoleDiameter=R*BORE.
The volume of a cylinder with height 0.4 mm and diameter the GasketHoleDiameter is (this is actually the decrement of the Dead Volume when the 1.6mm head gasket is replaced by the 1.2mm one):
DeadVolumeDecr=0.4mm*pi*(GasketHoleDiameter^2)/4
i.e.
DeadVolumeDecr=0.4mm*pi*R^2*(BORE^2)/4
i.e.
BORE=(1/R)*SquareRoot(4*DeadVolumeDecr/(0.4mm*pi)) (A)
STROKE=600cc/(pi*(BORE^2)/4) (B)
9:1 compression and 600cc per cylinder means that:
DeadVolume=600cc/8=75cc (see previous posts)
With a head gasket thinner for 0.4mm the compression ratio goes to 9.5:1, so:
9.5=(600cc+75cc-DeadVolumeDecr)/(75-DeadVolumeDecr), i.e.
9.5*75cc-9.5*DeadVolumeDecr=600cc+75cc-DeadVolumeDecr, i.e.
DeadVolumeDecr=37.5cc/8.5=4.412cc=4412 cubic mm.
With R=1, i.e. with GasketHoleDiameter=BORE, the (A) and (B) formulas give:
BORE=118.5mm STROKE=54.4mm STROKE/BORE=46%, as originally calculated.
The formulas (A) and (B) are applied, for various values of R, to calculate the BORE and STROKE of the Revetec X4:
With R=1.01, i.e. with GasketHoleDiameter 1% larger than the BORE:
Bore=117.9mm STROKE=54.94mm STROKE/BORE=46.6%
Groove Section: Height 1.2mm and Radial Depth of 0.59mm.
With R=1.02, i.e. with GasketHoleDiameter 2% larger than the BORE:
Bore=117.34mm STROKE=55.49mm STROKE/BORE=47.3%
Groove Section: Height 1.2mm and Radial Depth of 1.17mm.
With R=1.03, i.e. with GasketHoleDiameter 3% larger than the BORE:
Bore=116.77mm STROKE=56.03mm STROKE/BORE=48.0%
Groove Section: Height 1.2mm and Radial Depth of 1.75mm.
With R=1.04, i.e. with GasketHoleDiameter 4% larger than the BORE:
Bore=116.21mm STROKE=56.57mm STROKE/BORE=48.68%
Groove Section: Height 1.2mm and Radial Depth of 2.32mm.
With R=1.05, i.e. with GasketHoleDiameter 5% larger than the BORE:
Bore=115.65mm STROKE=57.12mm STROKE/BORE=49.38%
Groove Section: Height 1.2mm and Radial Depth of 2.89mm.
The more the Radial Depth of the groove (like a ring around the combustion chamber) the more HC remain unburned. This is why car makers try to move upwards the top compression ring of the piston.
With R=0.99, i.e. with GasketHoleDiameter 1% shorter than the BORE:
Bore=119.10mm STROKE=53.85mm STROKE/BORE=45.21%
Gasket Extension Section: Height 1.2mm and Radial Width of 0.59mm
With R=0.98, i.e. with GasketHoleDiameter 2% shorter than the BORE:
Bore=119.71mm STROKE=53.31mm STROKE/BORE=44.53%
Gasket Extension Section: Height 1.2mm and Radial Width of 1.17mm
With R=0.97, i.e. with GasketHoleDiameter 3% shorter than the BORE:
Bore=120.33mm STROKE=52.77mm STROKE/BORE=43.8%
Gasket Extension Section: Height 1.2mm and Radial Width of 1.75mm
With R=0.96, i.e. with GasketHoleDiameter 4% shorter then the BORE:
Bore=120.95mm STROKE=52.22mm STROKE/BORE=43.18%
Gasket Extension Section: Height 1.2mm and Radial Width of 2.32mm
With R=0.95, i.e. with GasketHoleDiameter 5% shorter then the BORE:
Bore=121.58mm STROKE=51.68mm STROKE/BORE=42.50%
Gasket Extension Section: Height 1.2mm and Radial Width of 3.04mm
But a gasket extended into the combustion chamber cannot live for long.
The above numbers show that a different gasket hole diameter cannot change significantly the BORE and the STROKE of the Revetec X4.
For reasonable dimensions of the head gasket, the BORE of the Revetec X4 is more than double its stroke, making the surface to volume ratio of the combustion chamber not ideal, at least compared to conventional engines of similar capacity and purpose.
For instance, if the dead volume had pure cylindrical shape, with 118.5mm bore and 54.4mm stroke the surface of the combustion chamber at TDC is:
2*pi*((118.5mm)^2)/4 + pi*118.5mm*(54.4mm/8)=24589 mm^2
Applying the same in case of a “square” 600cc cylinder (i.e. bore=stroke=91.42mm) we have for the surface of the combustion chamber at TDC:
2*pi*((91.42mm)^2)/4+pi*91.42mm*(91.42mm/8)=16413 mm^2
So if the cylinder had equal bore and stroke, its combustion chamber surface at TDC is only 66.7% of the surface of the combustion chamber of a cylinder with 118.5 bore and 54.4 stroke.
Applying the above for a square cylinder of capacity 1100.5cc (bore=stroke=111.9mm), the combustion chamber surface is 24589 mm^2, i.e. the same with the over-square design above.
In other words, a square (i.e. bore=stroke) 4400cc engine has the same combustion chamber surface with the above over-square of only 2400cc capacity. To have a 2400 cc engine with the thermal loss of a “square” 4400cc sounds not good.
The high bore to stroke ratio is necessary when the objective is the high revving and the improved breathing (like sport cars, F1, GP etc). For normal use what is necessary is a small bore to stroke ratio that improves the thermal efficiency and reduces the emissions.
I hope you agree that without using anything more than pure geometry coming from ancient Greece, many interesting things revealed. To snob those great minds, lived 2500 year ago, is at least not clever.
Thanks
Manolis Pattakos