[RocketsNW] Parachute protection options

[Simpsonclark at aol.com]

Graphite or glass composite pistons molded to match the inside of the glass  
body tube and then sealed with an O-ring in a simple sawn and filed groove can 
 maintain 3 or 4 thousandths radial clearance, which is the recommended  
clearance.  That won't grab a rolled and shroud-wrapped chute. The pistons  can be 
molded by draping a cylinder with wet glass and pushing it to the bottom  of 
a release-coated short piece of body tube and then setting it on a  
release-coated surface, ideally a convexly curved surface.  I have no  standard 
preference respecting the installation orientation.  Lube the body  tube with silicone 
grease.
-Robert
 
 
In a message dated 11/11/2008 12:35:04 P.M. Pacific Daylight Time,  
steven.e.bloom at boeing.com writes:

You have  cardboard pistons in your vehicle and compressor?!?!???

Seriously  :>),  The tolerances, surface smoothness, and lack of a rag  
(parachute) laying on top of the piston make comparison.....  incomparable.

steve 

-----Original Message-----
From: Bryan  Young [mailto:foreveryoung at inlandnet.com] 
Sent: Tuesday, November 11, 2008  11:26 AM
To: kmcgoffin at worldaccessnet.com; Mfreptiles at aol.com
Cc:  rockets at rocketsnw.com
Subject: Re: [RocketsNW] Parachute protection  options

It sounds like I need to learn how pistons are designed -- they  seem to work 
well enough in my air compressor and vehicles. Are there any  references that 
contain piston design that I could look  into?
-B

-----Original Message-----
From:  rockets-bounces at rocketsnw.com [mailto:rockets-bounces at rocketsnw.com]
On  Behalf Of kmcgoffin at worldaccessnet.com
Sent: Tuesday, November 11, 2008  2:19 AM
To: Mfreptiles at aol.com
Cc: rockets at rocketsnw.com
Subject: Re:  [RocketsNW] Parachute protection options

Yes, it seems to be a delicate  balance between having enough clearance to 
avoid binding, and having too much  clearance that can catch the parachute or 
allow the piston to tilt enough to  'catch'.  It's a rather fault-intolerant 
design. Best suited for rockets  made with high grade materials and given lots of 
TLC before launch.  Not  good for "stuff another motor in and fly 'er" type 
hobby rockets.

That  may have something to do with why I was never a regular user of piston  
ejection.  :-)
+McG+


> In a message dated 11/9/2008  2:50:17 A.M. Pacific Standard Time, 
> kmcgoffin at worldaccessnet.com  writes:
> (I always wondered why the parachute didn't bind between the  piston 
> and body tube.)  I dunno.
>  
> It  sometimes does, especially with overzealous sanding of the piston 
>  skirt.  The larger the airframe diameter, the more likely this can  
> happen since tolerances are usually greater.
>  
>  Mike F.
> AOL Search: Your one stop for directions, recipes and all  other 
> Holiday  needs.
>
http://pr.atwola.com/promoclk/100000075x1212792382x1200798498/aol?redir=http
://searchblog.aol.com/2008/11/04/happy-holidays-from-aol-search/?ncid=emlcnt
ussear00000001
>  Search Now
> .
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>  http://mx1.blastzone.com/mailman/listinfo/rockets
>


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Graphite or glass composite pistons molded to match the inside of the glass body tube and then sealed with an O-ring in a simple sawn and filed groove can maintain 3 or 4 thousandths radial clearance, which is the recommended clearance.  That won't grab a rolled and shroud-wrapped chute. The pistons can be molded by draping a cylinder with wet glass and pushing it to the bottom of a release-coated short piece of body tube and then setting it on a release-coated surface, ideally a convexly curved surface.  I have no standard preference respecting the installation orientation.  Lube the body tube with silicone grease.
-Robert
 
In a message dated 11/11/2008 12:35:04 P.M. Pacific Daylight Time, steven.e.bloom at boeing.com writes:
You have cardboard pistons in your vehicle and compressor?!?!???
Seriously :>),  The tolerances, surface smoothness, and lack of a rag (parachute) laying on top of the piston make comparison..... incomparable.
steve
-----Original Message-----
From: Bryan Young [mailto:foreveryoung at inlandnet.com]
Sent: Tuesday, November 11, 2008 11:26 AM
To: kmcgoffin at worldaccessnet.com; Mfreptiles at aol.com
Cc: rockets at rocketsnw.com
Subject: Re: [RocketsNW] Parachute protection options
It sounds like I need to learn how pistons are designed -- they seem to work well enough in my air compressor and vehicles. Are there any references that contain piston design that I could look into?
-B
-----Original Message-----
From: rockets-bounces at rocketsnw.com [mailto:rockets-bounces at rocketsnw.com]
On Behalf Of kmcgoffin at worldaccessnet.com
Sent: Tuesday, November 11, 2008 2:19 AM
To: Mfreptiles at aol.com
Cc: rockets at rocketsnw.com
Subject: Re: [RocketsNW] Parachute protection options
Yes, it seems to be a delicate balance between having enough clearance to avoid binding, and having too much clearance that can catch the parachute or allow the piston to tilt enough to 'catch'.  It's a rather fault-intolerant design. Best suited for rockets made with high grade materials and given lots of TLC before launch.  Not good for "stuff another motor in and fly 'er" type hobby rockets.
That may have something to do with why I was never a regular user of piston ejection.  :-)
+McG+
> In a message dated 11/9/2008 2:50:17 A.M. Pacific Standard Time,
> kmcgoffin at worldaccessnet.com writes:
> (I always wondered why the parachute didn't bind between the piston
> and body tube.)  I dunno.
>  
> It sometimes does, especially with overzealous sanding of the piston
> skirt.  The larger the airframe diameter, the more likely this can
> happen since tolerances are usually greater.
>  
> Mike F.
> AOL Search: Your one stop for directions, recipes and all other
> Holiday needs.
>
http://pr.atwola.com/promoclk/100000075x1212792382x1200798498/aol?redir=http
://searchblog.aol.com/2008/11/04/happy-holidays-from-aol-search/?ncid=emlcnt
ussear00000001
> Search Now
> .
> _______________________________________________
> Rockets mailing list
> Rockets at rocketsnw.com
> http://mx1.blastzone.com/mailman/listinfo/rockets
>
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