Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Building Techniques
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #31  
Old 04-12-2022, 12:40 AM
georgegassaway's Avatar
georgegassaway georgegassaway is offline
Contest, Sport, it's all good......
 
Join Date: Jul 2008
Location: West of Minneapolis, MN
Posts: 641
Default

Quote:
Originally Posted by rocket.aero
Our friends from overseas are experienced flyers, and most of the top-tier S7 competitors are already using Aerotech motors.

Yeah. The 10mm motors got all the glory for the lower power events.

But some countries' scale teams were hampered at times trying to use European made D, E, & F type black powder motors that often went "ka-boom". Or had very poor performance, not enough thrust. Things started to shift when at some WSMC, a couple of spare Aerotech E or F engines suitable for scale were given or traded to another country's team (possibly Poland), for their scale fliers to use. I think perhaps the next time, some were arranged in advance by request, but am not sure.

And the other countries saw how well the Aerotech engines worked, so finally some of them started to get their own...somehow (Sierra Fox Hobbies is in Italy and ships all over the place. So maybe thru them, maybe more directly. They also sell Estes engines). And I know there have been Aerotech and Estes engines sold in the UK.
__________________
Contest flying, Sport flying, it's all good.....
NAR# 18723 NAR.org
GeorgesRockets.com

Last edited by georgegassaway : 04-12-2022 at 01:02 AM.
Reply With Quote
  #32  
Old 04-12-2022, 07:13 AM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 11,130
Default

I enjoyed the videos. What material are the piston tubes made of? The B6 Egglofter flight put a lot of side force on it. It bowed like a spring but came right back.
__________________
I love sanding.
Reply With Quote
  #33  
Old 04-12-2022, 10:57 AM
Ez2cDave's Avatar
Ez2cDave Ez2cDave is offline
Master Modeler
 
Join Date: Mar 2005
Posts: 1,115
Default

Quote:
Originally Posted by tbzep
I enjoyed the videos. What material are the piston tubes made of? The B6 Egglofter flight put a lot of side force on it. It bowed like a spring but came right back.


My theory is that they are fiberglass, because of the length. I think a paper tube might crimp, at that length.

Dave F.
__________________
"Failure Is Not An Option . . . Adapt & Overcome ! "

NAR # 26128 L2
TRIPOLI # 517 L2 ( inactive, at present )

Last edited by Ez2cDave : 04-12-2022 at 06:01 PM.
Reply With Quote
  #34  
Old 04-12-2022, 11:33 AM
georgegassaway's Avatar
georgegassaway georgegassaway is offline
Contest, Sport, it's all good......
 
Join Date: Jul 2008
Location: West of Minneapolis, MN
Posts: 641
Default

Quote:
Originally Posted by tbzep
I enjoyed the videos. What material are the piston tubes made of? The B6 Egglofter flight put a lot of side force on it. It bowed like a spring but came right back.

18mm paper body tubes from BMS. That is why they look white.

That B6 eggloft piston was 68" long (two 34" tubes, with a 19mm external coupler. And the inside edges sanded with a cone of sandpaper to round the lips so the piston head slides thru as though there is no joint at all).

It seems as it sepped, the exhuast helped to deflect the top sideways, acting upon the flat face of the top ring. The mass of the top centering ring helped it "twang" like that (plus the initial deflection cause), as I have not noticed that effect on any other 68" pistons that did not have those centering rings. Indeed that's the most extreme "twang" I've seen in flight test videos. Also, there is a chance that the piston tube also bowed some from the vertical acceleration, given the mass it was pushing and possibly the egglofter not being dead center.
__________________
Contest flying, Sport flying, it's all good.....
NAR# 18723 NAR.org
GeorgesRockets.com

Last edited by georgegassaway : 04-12-2022 at 11:53 AM.
Reply With Quote
  #35  
Old 04-12-2022, 06:06 PM
Ez2cDave's Avatar
Ez2cDave Ez2cDave is offline
Master Modeler
 
Join Date: Mar 2005
Posts: 1,115
Default

Quote:
Originally Posted by georgegassaway
18mm paper body tubes from BMS. That is why they look white.

That B6 eggloft piston was 68" long (two 34" tubes, with a 19mm external coupler. And the inside edges sanded with a cone of sandpaper to round the lips so the piston head slides thru as though there is no joint at all).

It seems as it sepped, the exhuast helped to deflect the top sideways, acting upon the flat face of the top ring. The mass of the top centering ring helped it "twang" like that (plus the initial deflection cause), as I have not noticed that effect on any other 68" pistons that did not have those centering rings. Indeed that's the most extreme "twang" I've seen in flight test videos. Also, there is a chance that the piston tube also bowed some from the vertical acceleration, given the mass it was pushing and possibly the egglofter not being dead center.


George,

So, what was the performance gain with a piston tube of that length ?

I believe there is a point of "diminishing returns", at some point, right ?

Dave F.
__________________
"Failure Is Not An Option . . . Adapt & Overcome ! "

NAR # 26128 L2
TRIPOLI # 517 L2 ( inactive, at present )

Last edited by Ez2cDave : 04-12-2022 at 06:27 PM.
Reply With Quote
  #36  
Old 04-13-2022, 03:39 PM
georgegassaway's Avatar
georgegassaway georgegassaway is offline
Contest, Sport, it's all good......
 
Join Date: Jul 2008
Location: West of Minneapolis, MN
Posts: 641
Default

A couple of more piston videos. I think this was B6 powered. It is a superroc. The tower had a V-shaped "wind shield" added to the top, to hlep keep the exposed upper section of the superroc form bending in the wind. After launch, you can see how the smoke is swirling downwind of the shield.

https://m.youtube.com/watch?v=9rcwE...eature=youtu.be

And this is a test of some 1/2A gliders, to be sure they did not shred due to the higher speed. And a test of an A Streamer model to be sure it flew OK.

https://www.youtube.com/shorts/0UoayOgUt9I
__________________
Contest flying, Sport flying, it's all good.....
NAR# 18723 NAR.org
GeorgesRockets.com
Reply With Quote
  #37  
Old 04-13-2022, 06:29 PM
shockwaveriderz shockwaveriderz is offline
rocket dinosaur
 
Join Date: Mar 2005
Location: My Old Kentucky Home
Posts: 1,130
Smile

Quote:
Originally Posted by Ez2cDave
George,

So, what was the performance gain with a piston tube of that length ?

I believe there is a point of "diminishing returns", at some point, right ?

Dave F.


Dave it depends on a number of factors:

Piston length
Piston diameter
Model weight
Engine used and it's thrust characteristics

For example for 13mm motors of type A3 and A10, smaller diameter piston tubes(10mm) produce more pressure than 13mm tubes do.

Higher thrust motors produce more pressure than low thrust at the same length

Egglofters due to their incresed weight benefit from longer piston tubes than lighter models do.

I have a thread over on TRF with some pressure info based upon several R&D reports.

https://www.rocketryforum.com/threa...pressor.172117/

Basically there is an optimized piston tube more or less for a particular model rocket motor.

Hth
__________________
"Old Rocketeer's don't die; they just go OOP".....unless you 3D print them.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 02:47 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe 1998-2022