29 mm forward closure

[Bkdoubleu]

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]

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

 

[jimzcatz]

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]

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

 

[kclo4]

Just bumping this thread. Is there no 29mm threaded closure?

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

 

[Lowpuller]

Are the 29 mm closures the same for both high power and hobby loads?

 

[kclo4]

Negative, the 40-120 closures are different.

 

[rharshberger]

Are the 29 mm closures the same for both high power and hobby loads?

No the 29/40-120 case uses a different closure forward and aft than the RMS Casings.

 

[Steve Shannon]

Just bumping this thread. Is there no 29mm threaded closure?

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

Have you contacted Aerotech? They should be able to answer both questions.

 

[mikec]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

 

[Kruegon]

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]

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]

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.