AeroTech Open Thread

[readytorock556]

Question, I’m putting together a Redline in a 480 case all is good except for a 1/8 gap in the end closure. Motor has been built properly and check 3 times. Everything seems to be seated well including Orings. I mean I cranked it down as best I could and it’s tight. Is it ok to fly with a little gap?

 

[Theory]

@readytorock556 yes, absolutely. Aerotech has been cutting the liners a little longer to ensure there is a tight positive seal.

Trust me, a little gap is 100,000.91 times better than the closures bottoming out with little resistance.

 

[mrwalsh85]

With the caveat that the gap should be on the aft closure,. The forward closure should be fully seated/threaded down.

 

[Theory]

Up close and personal with a G138 in my old school Loc Precision Minnie Magg. #MACHDIAMONDS



Love this motor!!!!

 

[cwbullet]

Up close and personal with a G138 in my old school Loc Precision Minnie Magg. #MACHDIAMONDS

View attachment 639166

Love this motor!!!!

Beautiful motor!

 

[4regt4]

Up close and personal with a G138 in my old school Loc Precision Minnie Magg. #MACHDIAMONDS

View attachment 639166

Love this motor!!!!

Nice Pic!

For some reason, I wasn't expecting a purple flame.

Hans.

 

[krislhull]

I was building up a few motors today for an upcoming launch, and while assembling a F24W into a 24/40 case, I had an issue where the nozzle would not fit past the threads on the case. I tried the other two nozzles in the package, and they fit, so it's just the one nozzle. I also got a liner stuck in the case, and tore it while trying to get it out, so I decided to order a EMK from the RCS website to replace these two components. However, from looking at the assembly drawing for the F24W motor, I need a P/N 01300-1 nozzle with a .125" drilled throat. However, the EMK for medium 24/40 loads has a P/N 01300 nozzle with a .104" throat. I am guessing I will have to drill the throat out to .125"? Or can I lightly sand the edges of the existing nozzle down to fit?

 

[AeroTech]

I was building up a few motors today for an upcoming launch, and while assembling a F24W into a 24/40 case, I had an issue where the nozzle would not fit past the threads on the case. I tried the other two nozzles in the package, and they fit, so it's just the one nozzle. I also got a liner stuck in the case, and tore it while trying to get it out, so I decided to order a EMK from the RCS website to replace these two components. However, from looking at the assembly drawing for the F24W motor, I need a P/N 01300-1 nozzle with a .125" drilled throat. However, the EMK for medium 24/40 loads has a P/N 01300 nozzle with a .104" throat. I am guessing I will have to drill the throat out to .125"? Or can I lightly sand the edges of the existing nozzle down to fit?

Please contact warranty and they will sort it out. But there may just be a little protrusion for the molding sprue that can be sanded off.

 

[AeroTech]

I have a question about the phenolic inserts that Aerotech is putting into certain motors to prevent nozzle erosion.

Can I assume these inserts are in the nozzle throat only?

If that's the case , then these inserts have to be pretty small in diameter.?

So the question becomes, where does one find very small diameter phenolic tubes to accomplish this?

Or do you just machine phenolic rod?

Paper,Linen or Canvas?

Tia

They are molded out of a glass-filled phenolic like our other nozzles. They are slightly smaller than the inside of the case and are sealed with an O-ring.
https://www.rocketmotorparts.com/product/18mm-nozzle-0-064"-throat

 

[Theory]

Nice Pic!

For some reason, I wasn't expecting a purple flame.

Hans.

Thanks! Have found that the “new blue thunder” propellant starts off more purple and then turns blue through the burn. Still not as blue as a traditional blue thunder

 

[kjhambrick]

All --

I tried opening RCS Store - RMS-38/1080 External Dimensions (70k) but I get an error ( screen shot below my sig ) so I can't look it up for myself ...

Anyhow ...

I've got an old, black Dr Rockets 38mm aft closure that I BELIEVE came with a Dr Rockets RMS 38/1080 complete motor from 1990-something.

The central port for the nozzle on the black Dr Rockets aft closure is 0.825 inch.

OTOH, the central nozzle port on my gold Aerotech aft closures is 0.632 inch.

Is the black Dr Rockets aft closure for the RMS 38/1080 motor or did I get that thing somewhere else ?

Thanks !

-- kjh

I see similar errors when I try to open any of the RCS .pdf files on the RCS RMS Motor External Dimension Drawings today:

 

[Art Upton]

I can open the PDFs just fine.

Generally the opening the AFT closures are for most motors, but as time goes by a larger nozzle may get created by Aerotech and they make a larger opening Aft closure. But lets let the experts Opine...

 

[prfesser]

Hmm... I clicked on both of your links and they popped right up. Then I clicked on the 38/1080 in the first link and got your error. Strange...

Anyway:

Opinion only: the radius of the aft closure opening appears to be slightly larger than the 0.368 dimension. A ruler against the image says that radius is about 1.2x larger. Suggests a diameter of roughly 0.88". Possibly the gold closure is for the 38/720 motor.

 

[kjhambrick]

Thanks @Art Upton and @prfesser ...

Must be me and my browser session.

I'll restart chromium and try again.

-- kjh

p.s. the dimension I am looking for is the ID of the nozzle orifice in the aft closure ...

 

[bad_idea]

I see similar errors when I try to open any of the RCS .pdf files on the RCS RMS Motor External Dimension Drawings today:

View attachment 639800

Same error here, running Firefox. EDIT: it's working now, a few minutes after I last tried. Problem is either intermittent or has been resolved.

I don't think it will answer your question, but I'm attaching a copy of the 38/1080 dimensions that I saved some time ago.

 

[tsmith1315]

The central port for the nozzle on the black Dr Rockets aft closure is 0.825 inch.

OTOH, the central nozzle port on my gold Aerotech aft closures is 0.632 inch.

My first 38mm motor was a 480, mid 90’s.

When the J350W was released, I had to have one, and found that it required an aft closure with a larger nozzle opening.

I don’t see any mention of the small-opening closure anymore, but I still have both.

 

[Art Upton]

My first 38mm motor was a 480, mid 90’s.

When the J350W was released, I had to have one, and found that it required an aft closure with a larger nozzle opening.

I don’t see any mention of the small-opening closure anymore, but I still have both.

Yea, I got like serial #127 of a 38/240 full motor kit when they came out; 1990? I had to get a larger opening closure some years later for some motors.

 

[prfesser]

Weird...I copied the links from the RCS page and from KJH's post, and pasted them into Word. They're identical. Clicking on KJH's post takes me to the drawing. Clicking on the link in RCS's page gives me the error.

 

[kjhambrick]

My first 38mm motor was a 480, mid 90’s.

When the J350W was released, I had to have one, and found that it required an aft closure with a larger nozzle opening.

I don’t see any mention of the small-opening closure anymore, but I still have both.

That must be it then.

I have a Dr Rockets RMS 38/720 complete motor as well so the Black aft closure with the large nozzle orifice must be for the J350.

I am certain I used the black aft closure with the big hole when I flew a J350 last fall.

I've got an old J570 on hand. I hate to open it but I think I can 'measure' the nozzle diameter thru the bag ...

Thanks all !

-- kjh

p.s. the links from the main RCS site are still broken for me, even after restarting my browser ... maybe a regional thing since it works for some folks ...

 

[SolarYellow]

Now for the question: If the hole in an older closure is opened up to the dimension of the certified newer closure, does that make it an EX-only part?

 

[Art Upton]

Now for the question: If the hole in an older closure is opened up to the dimension of the certified newer closure, does that make it an EX-only part?

You need to ask a Pink Book Lawyer

I'm sure AT's stance is it is not certified/warrantee if you milled a part up or down on their motors.

 

[tsmith1315]

That must be it then.

I have a Dr Rockets RMS 38/720 complete motor as well so the Black aft closure with the large nozzle orifice must be for the J350

I have vague recollection of the dealer saying the J350 needed the larger opening closure that the bigger motors used. Which would have been loads for the 38/600 case, at that time.

 

[Art Upton]

This is all making me wonder where my J570 Closure is, and the rubber maid bins the motor parts are in , is at the back of the storage shed that I need some help to move a couple of yard machines out of the way to get to them.

 

[kjhambrick]

I have vague recollection of the dealer saying the J350 needed the larger opening closure that the bigger motors used. Which would have been loads for the 38/600 case, at that time.

Yes, my Dr Rockets 38/720 case is S/N 221 from 08/96.

Why can't I remember 28 year-old details like that ?

At least I didn't do something dumb like use the Black Closure with the big hole on the I357T or the I161W that I flew this year !

-- kjh

 

[kjhambrick]

This is all making me wonder where my J570 Closure is, and the rubber maid bins the motor parts are in , is at the back of the storage shed that I need some help to move a couple of yard machines out of the way to get to them.

This !

I have old AltAcc data for three J570 flights so I KNOW I have that motor case ( I remember it being a red Dr Rockets case ).

I never found the case, but there are still a couple boxes in the attic that I couldn't get to easily -- the crew that blew in our insulation moved them 'over there'.

I recently bought a new AT 38/1080 case only to avoid that hazardous trek (*) which is what got me off on this tangent !!

-- kjh

(*) My wife Steph would be REALLY annoyed if I fell thru the kitchen ceiling while walking across the ceiling joists to fetch those boxes

 

[Art Upton]

This !

I have old AltAcc data for three J570 flights so I KNOW I have that motor case ( I remember it being a red Dr Rockets case ).

I never found the case, but there are still a couple boxes in the attic that I couldn't get to easily -- the crew that blew in our insulation moved them 'over there'.

I recently bought a new AT 38/1080 case only to avoid that hazardous trek (*) which is what got me off on this tangent !!

-- kjh

(*) My wife Steph would be REALLY annoyed if I fell thru the kitchen ceiling while walking across the ceiling joists to fetch those boxes

Here is the Pic of the J570 motor case & aft closure before I put it back in the motor tub. Yes it is sticking out the back of the 38mm LOC tube that has the ACME fin can on it. It was all A-OK. So that is Kraft Tubing plowed into the Playa, no glass except that the Acme fin can might be cast out of.

Edit: yes much of it was accordion crushed.

 

[kjhambrick]

Here is the Pic of the J570 motor case before I put it back in the motor tub:

Ouch ! B.T.D.T.

 

[tsmith1315]

Yes, my Dr Rockets 38/720 case is S/N 221 from 08/96.

My brother!

Why can't I remember 28 year-old details like that ?

Unlike me, you might have useful information taking their place.

 

[kjhambrick]

My brother!

<< snip a beautiful pic >>

Unlike me, you might have useful information taking their place.

I dunno about that ... my granddaughters are conspiring to fill my head with Peppa Pig and Paw Patrol and Bubble Guppies and such

-- kjh

 

[kjhambrick]

Same error here, running Firefox. EDIT: it's working now, a few minutes after I last tried. Problem is either intermittent or has been resolved.

I don't think it will answer your question, but I'm attaching a copy of the 38/1080 dimensions that I saved some time ago.

Thanks Stephen !

I used a decimal ruler on a hard copy to measure the OD and ID of the hole on the aft view:

I got 0.815 inch so the RMS 38/1080 appears to use the aft closure with the big hole -- same as the RMS 38/720 ...

-- kjh