Motor Tubes and How to find them

[Orestes Mayo]

Hello everyone. I am a BAR as of a year ago. I have gotten back into rocketry with a bang, building 70 rocket in 1 year from Beginners level to Advanced. I had a lot of catching up to do. I have built LP, MP and my first HPR, the Loc4 which I will fly for cert 1 this month. So enough about me.

All my builds come with their own parts' which includes the motor mounting tube. My question is regarding those motor tubes. Is there a place to purchase them? I do the math, for example, and see that a 29mm would be 1.1242 inches for ID. Not a common BT size which would be something like a BT53. I have gone to the sites selling parts and accessories, eRockets, LaunchLab, etc. and I cannot find motor tubes. Not to mention greater then 29mm; 38mm, etc.

Any guidance and or advice or both is appreciated.

 

[tfish]

https://locprecision.com/collections/rocket-components/products/motor-mount-tubing

https://www.balsamachining.com/#

Tony

 

[Titan II]

LOC
Madcow

 

[tsmith1315]

29mm are normally listed as such.

Here's a site with great prices and service, and sizes are shown about as neatly as you can intermingle the different brand nomenclatures:

https://www.balsamachining.com/#

Notice the T-52H actually says 29mm Motor mount tube in the description.

 

[Scott_650]

29mm tubes are BT-52H
24mm tubes are BT-50 or BTH-50
18mm tubes are BT-20
13mm tubes are BT-5
6mm/Micromax tubes are T-MM

The “H” designates thicker walled tubes which can need different centering rings due to the increased diameter. eRockets can be a little confusing to navigate, the drop down menus under Parts For Rockets have all the tubes listed by size and type. Balsa Machining has motor tubes broken out separately - except 29mm which is in the body tube list. Aerospace Specialties has their motor tubes - except for Micromax motors - broken out on a separate page https://www.asp-rocketry.com/ecommerce/Engine-Mount-Tubes.cfm?cat_id=10.

 

[kuririn]

https://www.erockets.biz/bth-52-lt-115-29mm/https://www.erockets.biz/bth-38mm/https://www.erockets.biz/bt-50-24mm/https://www.erockets.biz/bth-50-24mm/https://www.erockets.biz/bt-20-18mm/

 

[lakeroadster]

My question is regarding those motor tubes. Is there a place to purchase them?

Balsa Machining Service

Fast friendly service, and they stock American Made tubes.

 

[prfesser]

Hello everyone. I am a BAR as of a year ago. I have gotten back into rocketry with a bang, building 70 rocket in 1 year from Beginners level to Advanced. I had a lot of catching up to do. I have built LP, MP and my first HPR, the Loc4 which I will fly for cert 1 this month. So enough about me.

All my builds come with their own parts' which includes the motor mounting tube. My question is regarding those motor tubes. Is there a place to purchase them? I do the math, for example, and see that a 29mm would be 1.1242 inches for ID. Not a common BT size which would be something like a BT53. I have gone to the sites selling parts and accessories, eRockets, LaunchLab, etc. and I cannot find motor tubes. Not to mention greater then 29mm; 38mm, etc.

Any guidance and or advice or both is appreciated.

I'm probably on the wrong track but it sounds as though you're assuming a level of precision that is greater than needed. A MMT for a 29mm motor must be 1 1/8" i.d. or slightly larger. It doesn't have to be 1.1242" precisely; anything around 1.13- 1.16" i.d. or thereabouts will work a treat., as long as the motor will slide in place.

The BT designation "belongs" to Estes tubes. Many, many other sizes are available today. Unfortunately, standardization of dimension units in the rocketry community is minimal. Some are listed as "T-something", some in Metric, some in Imperial units, etc.

As mentioned above, some vendors sell thicker-walled MMTs. The precise i.d. is not as important as "Will the MMT fit the centering rings?" In fact, a motor-mount tube may not be necessary at all. Last year I watched as a 12" diameter Sonotube rocket was launched and recovered successfully on an M motor. Centering rings were cut from 2x12. No MMT at all.

 

[OzHybrid]

Hello everyone. I am a BAR as of a year ago. I have gotten back into rocketry with a bang, building 70 rocket in 1 year from Beginners level to Advanced. I had a lot of catching up to do. I have built LP, MP and my first HPR, the Loc4 which I will fly for cert 1 this month. So enough about me.

All my builds come with their own parts' which includes the motor mounting tube. My question is regarding those motor tubes. Is there a place to purchase them? I do the math, for example, and see that a 29mm would be 1.1242 inches for ID. Not a common BT size which would be something like a BT53. I have gone to the sites selling parts and accessories, eRockets, LaunchLab, etc. and I cannot find motor tubes. Not to mention greater then 29mm; 38mm, etc.
Any guidance and or advice or both is appreciated.

29mm is REALLY a slide-fit tube on the OD of a 1 1/8 tube used for the manufacture of the motors. You can verify this from the manufacturing documents for the Aerotech motors. So the tube ID is 1.125" plus a tiny bit and has become called 29mm......

https://d11fdyfhxcs9cr.cloudfront.net/templates/170652/myimages/rms 29:40-120_1698854805136.pdf
Bottom Right.... View of Forward Closure dia = 1.125.........

General motor drawings can be found here
https://www.rocketmotorparts.com/page/rms-external-dimension-drawing
Similarly 38mm is a tube that fits a motor OD 1.5" designated as a 38mm motor.
And 54mm is a tube that fits a motor OD 2.125" designated as a 54mm motor

A bit like the White Rhino isn't white and in fact, was the wide-mouthed rhino where the name was misheard and the rest is history.
The sizes we use for motors, are in general, badly metricated versions of Imperial sizes..... However, if you search for tubing and use the motors metricated size it allows you in general to find a motor mount tube rather than an airframe tube. This only falls down as a rule of thumb where a manufacturer has used a motor mount tube as an airframe in a minimum diameter or another motor mount tube as an airframe.
Motor mount tube will usually be designated as that of the motor size in metric like 29mm tube 38mm 54mm etc. There are excel spread sheets on this forum with the different inside and outside tube dimensions from different tube manufacturers. Now you sort of understand why a motors imperial size has been metricated......

https://www.rocketryforum.com/threa...centering-ring-dimensions.183758/post-2525471
You can quite easily make your own tubes if they are difficult to get hold of by using a suitable tube to wind them on and gummed paper tape. I use my RattWorks I80 hybrid motor to make my 29mm mounts.(1.125") It's about 2 1/2 feet long which is long enough to produce plenty of motor mount tube for 29mm mmt
Here's a link to some work by @prfesser and others including me.

https://www.rocketryforum.com/threads/making-spiral-wound-paper-tubing.178953/
Good luck on your journey...
Norm

 

[teepot]

Balsa Machining Service. All the parts you need and at very good prices. I have bought most of the parts of my 200+ rockets using their parts. Of course it helps that they are 5 minutes away.

 

[Orestes Mayo]

29mm tubes are BT-52H
24mm tubes are BT-50 or BTH-50
18mm tubes are BT-20
13mm tubes are BT-5
6mm/Micromax tubes are T-MM

The “H” designates thicker walled tubes which can need different centering rings due to the increased diameter. eRockets can be a little confusing to navigate, the drop down menus under Parts For Rockets have all the tubes listed by size and type. Balsa Machining has motor tubes broken out separately - except 29mm which is in the body tube list. Aerospace Specialties has their motor tubes - except for Micromax motors - broken out on a separate page https://www.asp-rocketry.com/ecommerce/Engine-Mount-Tubes.cfm?cat_id=10.

Thank you. This is exactly what I was looking for.