Heavy impact James is absolutely correct. I’ve been involved in duct design for the HVAC industry for years and air flow (pressurized air flow) is best using radius fittings vs cornered fittings
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Tuning FX Impact Mk2/M3 - reducing valve opening effort
- Thread starter Seeker
- Start date
I'm being too lazy to draw you a picture, but if you angle the surface at 45 degrees then the length of the surface will increase by the square root of 2 (approx 1.4) therefore the total force acting on that surface will be 1.4 times the original (say x). Hence the force acting parallel to the rod will be x * 1.4 / 1.4 which is back to the original value x. The correct math for a cone would be a bit different, but the principle still applies.
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The surface will be 1.4 times bigger but only 0.5 of the force will act in parallel direction to the rod. Still a slight improvement.
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I don't think knocking the poppet off the seat is the problem, it's achieving the desired dwell once the poppet is in the air stream... so we're back to aerodynamic drag on the poppet. If we can't measure the real world drag we can't do the math. Manufacturers like to put the valve down a narrow well for convenience but this causes much more drag on the poppet.
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Sorry, my bad - 70% of the force will work along the rod axis.
Here you go:
In our case phi is 45* and cos45*=0.707
Assuming that original area was 1cm2 and pressure was 300 bar: F=3000N
Assuming that new area is 1.4cm2: F=4200N
Force working along the rod prior to the modification was 3000N - there was only one component Fx.
After the modification we can calculate Fx=F*cos45*=4200N*0.707=2969N which is lower than 3000N by a tiny margin. But it is lower.
Here you go:
In our case phi is 45* and cos45*=0.707
Assuming that original area was 1cm2 and pressure was 300 bar: F=3000N
Assuming that new area is 1.4cm2: F=4200N
Force working along the rod prior to the modification was 3000N - there was only one component Fx.
After the modification we can calculate Fx=F*cos45*=4200N*0.707=2969N which is lower than 3000N by a tiny margin. But it is lower.
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An earlier figure rounded down. The "1.4 times bigger" is more like 1.414 times bigger. Use this figure in the calculation and they both come out to 3000N.
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I modeled it using a cone...many moons ago.....
So the increase in surface area will remove any perceived advantages using force vectors.
I only calculate to 2 decimal places....... the seating force on the valve are essentially the same..
Sorry
Stuart
So the increase in surface area will remove any perceived advantages using force vectors.
I only calculate to 2 decimal places....... the seating force on the valve are essentially the same..
Sorry
Stuart
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Easy way to visualise this without doing maths is to imagine holding the cone between you finger & thumb & squeezing hard.
The cone will want to move / slide out of your grip.
Like if you squeeze an orange pip, it launches across the room.
If you want to reduce the force, make the step smaller by enlarging the diameter of the rod furthest from the poppet (& the hole that in runs in).
The cone will want to move / slide out of your grip.
Like if you squeeze an orange pip, it launches across the room.
If you want to reduce the force, make the step smaller by enlarging the diameter of the rod furthest from the poppet (& the hole that in runs in).
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