Motor Adapter: B/C in a D Motored BT Rocket

[lakeroadster]

Last week I received some great advice on this thread Using A D Engine Casing As A B/C Engine Motor Mount.

I modified the design of the motor mount, please see drawing below.

Feel free to critique the design, your tutelage is most welcome.

Question: I'm thinking that wrapping some tape around the cardboard mount tube to secure the engine hook as shown in the "ISO View". What tape would you recommend?



View attachment X-Wing Alpha Rev 01 Dwg Sheet 5 of.pdf

 

[Rainmaker]

I use regular masking tape when I do this, sometimes coated with wood glue and sometimes not.

 

[jimzcatz]

Throw the hook away, you don't need it

 

[kuririn]

Nicely thought out. It reminds me of the US Rockets adapter. I assume you would use a wrap of masking tape at the adapter end to secure it from the ejection charge? Or, if your rocket has a larger diameter than 24mm (BT-50) you can use a second engine hook on the 24mm motor tube to secure the 18mm engine and adapter.The US Rockets adapter uses two centering rings, but spaced together at the end of the motor tube. They also do not believe in using engine hooks, preferring masking tape instead. The first ring goes into the end of the 24mm tube, the second ring lies outside and is wrapped by masking tape. The 18mm engine is wrapped with a narrow strip of masking tape acting as a thrust ring, and secured from ejection with another wrap covering the thrust ring and end of the 18mm tube. Whew. Or you can just glue thrust rings and use engine hooks for both motor tubes, which is what I usually do for the convenience. I use the long "E" engine hook and use a spacer if I'm flying with 24mm C or D engines. Faster field prep than wrapping everything with masking tape, and you can fly the full range of motors. BTW I use vinyl electrician's tape to secure the engine hooks. It'll last the life of the rocket. Masking tape can get brittle and dry out, especially with the heat of the motor tube.

P.S. Forgot to mention, if using an engine hook with this design, you would use split centering rings and secure the hook with either a tape wrap or mylar retaining ring:

https://www.erockets.biz/semroc-centering-ring-adapter-ring-bt-20-to-bt-50-slitted-6pk-sem-ar-2050s/

https://www.erockets.biz/semroc-mylar-retaining-ring-bt-20-6pk-sem-hr-20/

 

[lakeroadster]

BTW I use vinyl electrician's tape to secure the engine hooks. It'll last the life of the rocket. Masking tape can get brittle and dry out, especially with the heat of the motor tube.

Sage advice. I was curious about the masking tape eventually being an issue, mostly due to the heat of many motors.

Thanks.

 

[hcmbanjo]

Nice work on that drawing!
Yep, masking tape will break down over time.
This link is probably not the greatest example, it was a model that sat unfinished for years. The tape was old and flaked off.

https://modelrocketbuilding.blogspot.com/2014/04/estes-nike-apache-old-unfinished-build_30.html

In your drawing - The BMS engine hooks don't have a finger tab on them. The nozzle end bend is like the top bend.
The BMS hooks are great, made of spring steel.
In the newest runs of Estes kits, the engine hooks aren't spring steel. You bend them and they don't flex back.
They stay bent!

 

[hcmbanjo]

Looking again at your drawing,
Sometimes you can simply put a centering ring (your part 2) even with both ends of the engine tube.
If you model has a engine hook already on it, you simply have that hook latch over the rear centering ring.

 

[Mr Rocket]

The Estes version works well also.

EDIT: Picture won't post, so here is a link.
https://www.estesrockets.com/rockets/accessories/engine-mounting/302317-engine-adapters-standard-to-d



EDIT 2: So now they post

They even work with the Aerotech reloadables (RMS). Note: I don't have the 18mm casing, but the design looks the same as the 24mm-29mm adapter, and I use my RMS 24/40 in that adapter frequently with the ProSeriesII rockets. So I assume the 18mm is compatible also.

 

[lakeroadster]

Nice work on that drawing!
Yep, masking tape will break down over time.
This link is probably not the greatest example, it was a model that sat unfinished for years. The tape was old and flaked off.

https://modelrocketbuilding.blogspot.com/2014/04/estes-nike-apache-old-unfinished-build_30.html

In your drawing - The BMS engine hooks don't have a finger tab on them. The nozzle end bend is like the top bend.
The BMS hooks are great, made of spring steel.
In the newest runs of Estes kits, the engine hooks aren't spring steel. You bend them and they don't flex back.
They stay bent!

I literally read your post minutes after pulling the BMS engine hook out of the bag... Yep no finger tab, no worries.

Sounds like Estes has some issues.. mild steel engine hooks and exploding D9 engines...

Thanks for the advice sir, much appreciated.

The Estes version works well also.....
View attachment 345729View attachment 345738

If I wasn't such a penny pincher I'd just buy those. But since I have all the pieces parts... scratch build it is.

Thanks for the info.

 

[lakeroadster]

Here's some photo's of the adapter...