29mm to 38mm adapters alternatives to cardboard

[WizardOfBoz]

So I've put together a cardboard tube and ring adapter to be used in my Super DX3 with a LOC precision 38mm retainer. I'm looking at it, and it's just one glued ring (green, in the pic below) holding the whole thrust of the motor. Is this adequate? Or am I right to be nervous?

Is there a better adapter to be used with a screw-on retainer like the LOC?

 

[David_Stack]

https://aeropack.net/pages/motor-adapters in the event you don't have faith in your 'homebuilt'...

Member StreuB1 made some based on the motor adapter that Loc offers: https://www.rocketryforum.com/threads/wildman-mach-2-with-aeropac-retainer.185385/#post-2563082

 

[DragonRocketry]

https://dragonrocketry.com/products/2938-motor-adapter

 

[Art Upton]

So I've put together a cardboard tube and ring adapter to be used in my Super DX3 with a LOC precision 38mm retainer. I'm looking at it, and it's just one glued ring (green, in the pic below) holding the whole thrust of the motor. Is this adequate? Or am I right to be nervous?

Is there a better adapter to be used with a screw-on retainer like the LOC?

View attachment 644571

Are you using a K1000 or a Single use 29mm motor?

Many adapters are just a glued on HD ring. If you want to buy metal hardware Aeropack makes good stuff but you need to use their base retainer to get them all to work right.

So you would need to install the AeroPack 38mm screw on retainer, then you can use their 29/38 adapter.
If you lucked out and LOC's new retainer is close to AeroPack's then it can work for you.

I have a tub that has many of the LOC adapters in it. I even have a 98mm to 54mm cardboard adapter that has been used.

 

[tsmith1315]

and it's just one glued ring (green, in the pic below) holding the whole thrust of the motor. Is this adequate?

After all these years, they wouldn’t still be produced if they weren’t adequate.

Two of mine turn 30 years old next year.

 

[-Slick-Ice]

The only issue I have had with the cardboard ones is you need to friction fit the motor into the adapter tube which wasn't allowed on high-power launches here. If it was shortened you could probably tape it to the motor which would be fine. You could probably print an adapter washer similar to the Aeropack one.

If you are looking for "better" but functionally the same, Aeropack makes a really nice anodized A2938 adapter (although I keep losing that back washer) for $25-30.

I also have confidence in my 3D printed 29-38 clam shell adapter that I found on thingiverse with any 29/180mm load.

 

[tsmith1315]

The only issue I have had with the cardboard ones is you need to friction fit the motor into the adapter tube which wasn't allowed on high-power launches here

LOC 54-38 with J-clips

 

[-Slick-Ice]

I don't even like the Z clips on my Athena. More tools to lose.

 

[-Slick-Ice]

So you would need to install the AeroPack 38mm screw on retainer, then you can use their 29/38 adapter.
If you lucked out and LOC's new retainer is close to AeroPack's then it can work for you.

The Aeropack 38/54 in the LOC 54mm retainer did NOT work without sticking the A3854 in the lathe. I can't confirm whether this would be an issue for the A2938/LOC 38mm

 

[WizardOfBoz]

Are you using a K1000 or a Single use 29mm motor?

Many adapters are just a glued on HD ring. If you want to buy metal hardware Aeropack makes good stuff but you need to use their base retainer to get them all to work right.

So you would need to install the AeroPack 38mm screw on retainer, then you can use their 29/38 adapter.
If you lucked out and LOC's new retainer is close to AeroPack's then it can work for you.

I have a tub that has many of the LOC adapters in it. I even have a 98mm to 54mm cardboard adapter that has been used.

Are you using a K1000 or a Single use 29mm motor?
For my L1 Cert, an H180 in the RMS-29/360 tube with spacer.

Many adapters are just a glued on HD ring. If you want to buy metal hardware Aeropack makes good stuff but you need to use their base retainer to get them all to work right.
I saw that on the Apogee site. In an video from a while back, Tim Milligan used a cardboard tube adapter with tape as the retainer. The dragon product above looks interesting, but I just checked and both that product and the adapter I made has the 1/2 wide HD ring that keeps the motor from sliding forward, and so in both cases, it's too wide to allow the LOC retainer to engage. I guess I can use my cardboard adapter and use tape to retain, or could buy the Aerotech aluminum retainer. If the flange on the Aerotech is too large I could reduce it (I have a lathe but in this case a Dremel tool might work to reduce the diameter, if that's the issue).

So you would need to install the AeroPack 38mm screw on retainer, then you can use their 29/38 adapter.
If you lucked out and LOC's new retainer is close to AeroPack's then it can work for you.
I think that the aluminum "HD ring" looks to be only about 1/8" wide as opposed the 1/2" cardboard ring, and so I suspect that the LOC product will work. And gee, what's another $32 expense....

I have a tub that has many of the LOC adapters in it. I even have a 98mm to 54mm cardboard adapter that has been used.
I can see that I will have to "Harden the Flip Up*" if I want to continue in the hobby. But you and the other posters have reassured me that the cardboard adapter would work. I guess I can ask if tape retention is ok.

The other solution would be a LOC retaining nut that was 1/4 or 3/8 longer than their standard one.

*If you are not offended by crude language, google "HTFU Ronnie Johns Chopper"

 

[-Slick-Ice]

Although the H180 "only" has 51.37 lbs of peak thrust. I'd rather take the emotional hit asking if is going to work than send a motor casing flying by itself.

The first launch success rate for L1s this year has been well under 50%

 

[kramer714]

Simple 3D printed adapter, copies of the STL files on my previous posting.

https://www.rocketryforum.com/threads/disposable-motor-adapter-dma.179262/

Mike K

 

[thequick]

After all these years, they wouldn’t still be produced if they weren’t adequate.

Two of mine turn 30 years old next year.

+1
The cardboard will be fine. Use it and put the savings towards some 38mm hardware instead of a fancy adapter

 

[Aeva]

All I gotta say is make sure whatever you purchase fits all of the adapter parts. I got a 38mm to 54mm from apogee for my L1 motor to fit in my EZI. However, the nozzle design of the I-175 DMS is wide and flat, and the adapter seems to anticipate the nozzle protruding from the aft of the motor... so obviously it didn't fit. I didn't know until I was at the cert table prepping the motor... and ended up friction fitting the motor to the 38mm adapter and LOC retainer fit that perfectly fine.

Make sure you check your motor is compatible with what motor mount you're using.


The adapter I used, plus the ring that didn't fit and I left out. It's just a cardboard tube with plywood centering rings and I think I used wood glue to bond the centering rings to it.

 

[kjhambrick]

+1 for cardboard adapters.

They work GREAT !

This is one of my 25 +year old, homemade, cardboard 38 -to- 29 mm adapters with a ready-to-fly RMS 29/240 H180W with the forward closure 'plugged' with dog barf and masking tape.

Note the shortish adapter and the forward tape ring to retain the motor in the adapter.

It only adds 26 grams to the motor mass.

I'll fly this Rube Goldberg contraption in T'Pring's P'Toy to about 3500 ft tomorrow at the Tripoli Houston Hearne Launch if the 8 -to- 10 mph easterly wind and the 13.8 KV power line 1000 ft west of the pads don't scare me away

-- kjh

 

[Titan II]

Is this adequate?

yes

 

[WizardOfBoz]

+1 for cardboard adapters.

They work GREAT !

This is one of my 25 +year old, homemade, cardboard 38 -to- 29 mm adapters with a ready-to-fly RMS 29/240 H180W with the forward closure 'plugged' with dog barf and masking tape.

Note the shortish adapter and the forward tape ring to retain the motor in the adapter.

It only adds 26 grams to the motor mass.

I'll fly this Rube Goldberg contraption in T'Pring's P'Toy to about 3500 ft tomorrow at the Tripoli Houston Hearne Launch if the 8 -to- 10 mph easterly wind and the 13.8 KV power line 1000 ft west of the pads don't scare me away

-- kjh

The tape on the forward side of the adapter is brilliant. This allows one to just use the 38mm cap on the aft. Very clean.

Good luck in your flight.

 

[kjhambrick]

Thanks, @WizardOfBoz.

I don't remember who showed me that trick but it does work very well.

-- kjh

 

[Art Upton]

In Defense of Masking Tape*, Dr. Kosden used masking tape to hold an O motor in at Balls launch a few decades ago...

* That was a title of an article in NAR's Model Rocketeer in 1974 or maybe 75 at the most.

 

[tsmith1315]

In Defense of Masking Tape*, Dr. Kosden used masking tape to hold an O motor in at Balls launch a few decades ago

And…

The older motor adapters didn’t even have the cardboard thrust ring, which was the main question in the first post.

The flyer made that thrust ring by wrapping masking tape around the aft end to the thickness of the motor tube.



It works fine.

 

[kjhambrick]

Nice ones, Tim !

And ... And ... "In Defense of Masking Tape" ...

I made the centering rings for the ID of that 38mm coupler tube from masking tape and epoxy but the thrust ring is a short piece of 38mm motor mount tube

-- kjh

 

[cwbullet]

And…

The older motor adapters didn’t even have the cardboard thrust ring, which was the main question in the first post.

The flyer made that thrust ring by wrapping masking tape around the aft end to the thickness of the motor tube.

View attachment 644703

It works fine.

Tape is a great thrust rings. Cheap and low tech, but it works.