Quantcast

29 mm forward closure

The Rocketry Forum

Help Support The Rocketry Forum:

Bkdoubleu

Well-Known Member
Joined
Jan 25, 2016
Messages
69
Reaction score
0
I have searched for two weeks for a 1/4" center threaded AT forward closure. I've struck out. I'd like to cut the baffle out of a AT Strong arm to fly I reloads. If I could put an eye bolt in the fwd closure I could slide a 29/360 in it. Think it's possible to just buy a plugged fwd. closure and drill/tap it myself?
The airframe flies just fine on an DMS AT I205 now. I just have to friction fit the motor.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,610
Reaction score
3,432
Location
Butte, Montana
If you modify a forward closure in a way that hasn't been approved by the manufacturer, you're no longer flying using certified hardware, meaning you are only allowed to fly it at a Research Launch.
I don't know if threaded closures for the 29mm were produced by AT or any of their licensees. Have you contacted Aerotech?


Steve Shannon
 
Last edited:

jimzcatz

Boss, Carolina Rocket Mafia
Joined
Jan 22, 2009
Messages
4,099
Reaction score
297
Location
Hurdle Mills NC
Steve, that's misinformation. If a manufacturer tells you it's, ok, it's ok. I have enlarged the holes on older 38mm rear closures (under Gary's advice) to accommodate the newer nozzles. This is still a certified configuration.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,610
Reaction score
3,432
Location
Butte, Montana
Steve, that's misinformation. If a manufacturer tells you it's, ok, it's ok. I have enlarged the holes on older 38mm rear closures (under Gary's advice) to accommodate the newer nozzles. This is still a certified configuration.
You're correct Jim. Manufacturer approved modifications are allowed, but my understanding is that they must also be approved by the certifying body (NAR or TRA or CAR). I should have said so.
Thank you for the clarification. I'll edit my post above.

Here's the section from NFPA 1127:
4.5.3 A reloadable high power rocket motor shall not be altered except as allowed by the manufacturer and certified by a recognized testing organization acceptable to the authority having jurisdiction to meet the certification requirements set forth in NFPA 1125, Code for the Manufacture of Model Rocket and High Power Rocket Motors.

Steve Shannon
 
Last edited:

kclo4

Well-Known Member
Joined
Feb 3, 2010
Messages
150
Reaction score
0
Just bumping this thread. Is there no 29mm threaded closure?

Is it an approved mod to drill and tap a regular plugged closure?
 

Lowpuller

Well-Known Member
Joined
Nov 23, 2013
Messages
2,230
Reaction score
12
Are the 29 mm closures the same for both high power and hobby loads?
 

kclo4

Well-Known Member
Joined
Feb 3, 2010
Messages
150
Reaction score
0
Negative, the 40-120 closures are different.
 

mikec

Well-Known Member
Joined
May 9, 2009
Messages
2,504
Reaction score
384
Just bumping this thread. Is there no 29mm threaded closure?
No. There's a plugged closure but not a threaded one in the Aerotech catalog.

There are many other ways to do what you're asking without using a threaded closure. For example, attach a shock cord Estes-style ahead of where the baffle was, or add a new baffle, etc.
 

kclo4

Well-Known Member
Joined
Feb 3, 2010
Messages
150
Reaction score
0
Even if flying on a EX day, is the web thickness of the plugged 29mm closures enough to drill and tap?

I am planning for a minimum diameter bird and it turns my brain to think of friction fit being the only option.
 

kclo4

Well-Known Member
Joined
Feb 3, 2010
Messages
150
Reaction score
0
No. There's a plugged closure but not a threaded one in the Aerotech catalog.

There are many other ways to do what you're asking without using a threaded closure. For example, attach a shock cord Estes-style ahead of where the baffle was, or add a new baffle, etc.
I am not the OP, but thought this would be a good thread to continue the discussion.

My project would just be a minimum diameter fiberglass rocket that would likely turn into the sustainer for a 2 stage bird.

I want positive motor retention, but I also think I would be running thin speaker wire down the side of the motor for ignition and I am not sure how well that would play with friction fit.
 

rharshberger

Well-Known Member
Joined
Oct 13, 2014
Messages
9,791
Reaction score
1,762
Location
Pasco, WA
I am not the OP, but thought this would be a good thread to continue the discussion.

My project would just be a minimum diameter fiberglass rocket that would likely turn into the sustainer for a 2 stage bird.

I want positive motor retention, but I also think I would be running thin speaker wire down the side of the motor for ignition and I am not sure how well that would play with friction fit.
How about using this type of wire https://www.cableorganizer.com/p/ta...10-WT&ef_id=WT4eIgAABX4-9yYZ:20170612045250:s
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
6,985
Reaction score
1,436
A lot of the 29mm forwards I have look like they would easily take a C-clip. I haven't tried it, but it's been on my mind.
 

Onebadhawk

Sponsor
TRF Sponsor
Joined
Jan 11, 2013
Messages
6,119
Reaction score
409
Aerotech absolutely does not make a 29 mm high power plugged / threaded forward enclosure...
Nor does anyone else for them,, there never has been one..

A friend made one for me..
He took a standard 29 forward,,
either mig or tig ( not sure which ) welded on a 1/2" or 3/4"
of aluminum bar stock,, drilled it and tapped it for 1/4" X 20 threads...
Works perfectly,, no probs at all..
I'd love to post a pic,,
but my motor box is buried in my truck...
It's actually really cool...

Teddy
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
They do make a closure for the RAS that takes an eyebolt, but you couldn't use a full
motor, has to be at least one spacer in...
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,610
Reaction score
3,432
Location
Butte, Montana
They do make a closure for the RAS that takes an eyebolt, but you couldn't use a full
motor, has to be at least one spacer in...
That's nice in other ways also. I use a threaded rod in a 98 mm minimum diameter rocket, but I either have to have multiple lengths of threaded rods (which would be cheaper if you already have every case length) or I'm limited to one length of motor case. With the RAS I can use one case for three different lengths of reloads as well as a single length of threaded rod for retention.


Steve Shannon
 

1tree

Well-Known Member
Joined
Dec 28, 2011
Messages
297
Reaction score
0
While I don't have the plugged closure, I did pull my AT casing out to look. I would assume the plugged is very similar minus the small hole for lighting the ejection charge.

At any rate, I am certain that someone could make a sleeve that would snugly fit over the knurl and yet thin enough to fit up inside your rocket. Assuming that can be done, then epoxy said sleeve to the closure then make your attachment to the sleeve.

I would guess a machine shop could make a small metal cap that could be held in place with a pin or snap ring.
 

tfish

Well-Known Member
Joined
Dec 8, 2009
Messages
2,655
Reaction score
695
I used to attach shock cords right to the AT FC by...tie a loop into the shock cord...place a larks foot around the thin part of the FC...add a half hitch and use electrical tape over the top of everything. Never had it fail.

Tony
 

DavidMcCann

Well-Known Member
Joined
May 15, 2016
Messages
2,656
Reaction score
166
I used to attach shock cords right to the AT FC by...tie a loop into the shock cord...place a larks foot around the thin part of the FC...add a half hitch and use electrical tape over the top of everything. Never had it fail.

Tony
genius.
 

kclo4

Well-Known Member
Joined
Feb 3, 2010
Messages
150
Reaction score
0
I like the ideas from tfish and 1tree. I over think stuff but I think either would get r dun.

All or most of my club launches fly under research rules so I think I could just cross drill holes in the ejection well area and run some kevlar cord through it. The closures I have now are the adapter system version so I don't think they have the same lip as the normal ones. Or I could just buy a normal one and not modify it. Many ways to skin this cat it seems.
 
Last edited:

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
I've actually spoken to Charlie about a tapped 29mm closure. He told me it's on the idea board but not in planning yet. That was at NSL2016. A year later and no mention. Maybe we should tap his shoulder and ask again.
 

Bkdoubleu

Well-Known Member
Joined
Jan 25, 2016
Messages
69
Reaction score
0
I'm the OP.
I guess I could always just use a DMS and just epoxy the eye bolt in the fwd delay grain hole. Thanks everyone for the comments.
 

KevinM

Well-Known Member
Joined
Sep 4, 2009
Messages
127
Reaction score
36
Here's a longshot idea: what about using an old 29mm EFC forward closure? You could punch some holes in the section that would thread into the electronics portion, or you could even turn an end-cap that threads onto the end of the closure which has your eye bolt in it... I admit it's a lot of parts, but the last one certainly gets 'round any hint of motor modification.
 
Top