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  #1  
Old 04-04-2022, 11:52 AM
shockwaveriderz shockwaveriderz is offline
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Smile Floating Head Piston Questions

Would it be safe and correct to say that the height that a traditional floating head will fly once it leaves the piston rod, with the rocket attached, would be determined by the engine used?

If this is so, what kind of heights are we looking at ? 5ft ? 10ft? More?

I'm specifically talking about 1/4A3, 1/2A3 and A3 13mm motors.

Different motors with different thru-time curves are going to pressurize the piston differently?

it also seems to me that wind speed would have a detrimental effect on the rocket/piston tube assembly. Anybody ever seen such a combination hit with a strong wing and noticed how much it tilts before separation of the two?
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Old 04-04-2022, 12:26 PM
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Quote:
Originally Posted by shockwaveriderz
Would it be safe and correct to say that the height that a traditional floating head will fly once it leaves the piston rod, with the rocket attached, would be determined by the engine used?


Sounds like a nice NARAM R&D project for you. Even though floating head pistons are kind of passť these days, a decent report might still get you more than flight points.
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Old 04-04-2022, 12:38 PM
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Quote:
Originally Posted by astronwolf
Even though floating head pistons are kind of passť these days
What is the current weapon of choice in national/international competition?
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Old 04-04-2022, 03:39 PM
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Originally Posted by tbzep
What is the current weapon of choice in national/international competition?

Floating head pistons have been banned from international competition. It's fixed pistons only. I think you can still use the floating head variant in US competition, but I haven't checked lately.
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Old 04-04-2022, 03:46 PM
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Quote:
Originally Posted by astronwolf
Floating head pistons have been banned from international competition. It's fixed pistons only. I think you can still use the floating head variant in US competition, but I haven't checked lately.

Are they using the typical zero volume piston that's been around since the 70's, or have they come up with something different in the fixed piston relm?
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  #6  
Old 04-04-2022, 04:41 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by tbzep
Are they using the typical zero volume piston that's been around since the 70's, or have they come up with something different in the fixed piston relm?


it's basically the same design, Except now they have design upgrades like grooved teflon piston heads, some had pull pins to release a piston collar clamp, although that seems to have petered out. I never used a grooved teflon piston head but I may have been the 1st person to use a teflon piston head back at the Flyoffs at NARAM-47. Some use springs to absorb the piston head stop shock. A new feature is to use 10mm diameter piston tubes with a 13mm on top to fit the engine. Apogee Newsletter #428 has a good look at some Bulgarian and Ukrainian pistons.
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Old 04-05-2022, 12:02 AM
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Quote:
Originally Posted by tbzep
Are they using the typical zero volume piston that's been around since the 70's, or have they come up with something different in the fixed piston relm?


Many of us now use a short tube (4"-6") on top of our piston tubes creating an air gap between the rocket motor and the piston head. With black powder motors this is less for performance than it is for ease of use with fixed head pistons. Added benefit is that most of the soot from the motor ends up in the buffer tubes making repeat use of the longer piston tubes more possible.

You can piston launch composite motors, like the Quest Q-Jets , or other Aerotech single use motors if you use a buffer tube to prevent chuffing. Without such a buffer tube composites have difficulty igniting in a zero volume piston.
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  #8  
Old 04-04-2022, 04:45 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by astronwolf
Floating head pistons have been banned from international competition. It's fixed pistons only. I think you can still use the floating head variant in US competition, but I haven't checked lately.

wolf, your correct on both counts. I'm not 100% sure but I think they were banned for safety reasons and perhaps they might have just been a little better than the USA's competitors.

the safety reason being, that the piston tube which might be made out of fiberglass, kevalr or carbon fiber that's 2-3 ft onlg might bounch off somebodies head.
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  #9  
Old 04-04-2022, 05:41 PM
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Floating Head pistons are still fine for NAR contest flying.
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  #10  
Old 04-05-2022, 12:10 AM
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Quote:
Originally Posted by astronwolf
Floating head pistons have been banned from international competition. It's fixed pistons only. I think you can still use the floating head variant in US competition, but I haven't checked lately.

The only nation to use floating head pistons was the U.S.

Floating head pistons were banned the year after the U.S. won altitude and scale altitude at the World Championships in Ukraine.

In all fairness, though, one of the objections to floating head pistons is that our piston tubes would fly 20 - 30 feet in the air and then come dropping down on the heads and rockets of our neighboring competitors. Unlike U.S. competiton, International events have each country launching from their own narrow lane. Having piston tubes raining down on your rocket sitting on the pad was pretty annoying. Don't recall that we ever knocked anyone's rocket down, or hit someone in the eye, but they did have a point.

Floating head piston are still allowed in NAR competiton and are definitely way easier to set up than fixed heads.
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