low power rocket motor retainer

[Scott_mills]

From the various forums that i have read i am a bar primarily interested in 18 mm lpr flying, and cloning golden age kits using card stock conversions.


Now my question is this , in all the time this forum has been active has anyone come up with a reliable method for retaining motors with just a card stock device, or perhaps some other cheap alternative to the old reliable engine hook. I have a few ideas but have yet to try them out.

My first bar project is tons little Joe 2 with foam core centering rings triple wall bt on 65 #. I have a great idea for shock cord mounts using a bent paper clip , that I am trying out . i also came with a pretty decent and cheapcheap mylar card stock if anyone is interested.

 

[AstroNom]

Hi,

I was looking for the cheap and convenient motor mount myself, I was looking for 24mm retainer though. This is what I came up with - water/coke bottle necks and caps. There are a few diameters out there so not everyone fits, but coke for example fits almost perfect over the 24mm motor tube. You just cut the top off, put it on end of motor tube and drill the cap. It screwes on and I figure if it can hold the coke pressure, it will hold the force of motor ejection. I haven't tested it yet, this is my first rocket that am building with this thing.

So that's the idea I am looking for a bottle that will fit 18mm motor mount, but no success yet, Hydrogen Peroxide and rubbing alcohol bottles are a bit too small but I think can be sanded to fit. If you'll ever find one - post it

Whats with the paper clip and mylar?

 

[Scott_mills]

My reasoning for making this shock cord mount is that after 20 years the rockets i have all have dissolved cords which aren't easily replace with the reliable triple fold mount. This mount all you would need to do is tie a new one on as opposed to rocket surgery to get the old mount out.

To make some cheap metallized card stock, use a mylar emergency camping blanket cut into pieces about 1/4" larger than your cardstock. Fasten the piece to a smooth surface pulling it tight with tape, i would suggest the surface be glass. Apply spray adhesive to card stock, and to mylar then place the two pieces together. Press the two pieces together before removing from mirror , while on the mirror use a hobby knife to trim the excess mylar from around the card stock. This does work in a laser printer, I have yet to try it in an inkjet.

 

[Tiger]

Does it have to be non-metal? Or do you just want cheap/free? If you find a neighborhood that has street cleaners go by, you can just take a walk and keep a sharp eye out for the bristles that fall off. You could bend these into custom engine hooks. I've also heard you can pull little strips of thin metal out of used wiper blades, but I've never tried that myself.

 

[Scott_mills]

Yes i was looking for something free / cheap . I'm going to have to do some dumpster diving next time I'm at auto zone .

 

[Scott_mills]

I went through my fleet today and decided 6 birds weren't fixable so I retired them, keeping the nose cones and retainer. So I should be set for quite awhile for parts. By the way a does anyone out there know the body tube lengths on the old Estes 1284 space shuttle, I need to replace the fin set, and the instructions didn't have the lengths specified.

 

[Tiger]

The newest instructions for the shuttle at least have part numbers, so you might be able to call Estes and order a replacement part and/or ask them for lengths. https://www.estesrockets.com/media/instructions/001284_SPACE_SHUTTLE.pdf

 

[gpoehlein]

I have been toying with a cardstock motor retainer in my head for a while now, but haven't had the time to lay out the parts. With my impending layoff (this Friday is my last day of work), I will try to do the layout and upload it to the forum. Keep an eye out in the cardstock section, hopefully next week.

 

[TopRamen]

Does it have to be non-metal? Or do you just want cheap/free? If you find a neighborhood that has street cleaners go by, you can just take a walk and keep a sharp eye out for the bristles that fall off. You could bend these into custom engine hooks. I've also heard you can pull little strips of thin metal out of used wiper blades, but I've never tried that myself.

You've just solved one of my lifes Greatest Mysteries. When I lived in New Jersey as a Kid, I used to find these thin, flat Metal things about one foot in length on the side of the Street/Road. I always wondered where they came from. Was someone throwing them from a Vehicle? Had they fallen off of a Big Rig?
I never learned what they were, and even when I dealt with many types of Vehicles in the Army as a Mechanic, I never saw one.
Now, I realize they were from the Street Sweepers.

Thank You!
Dave

 

[hcmbanjo]

Here's a link to the article I co-wrote for the Apogee Peak Of Flight newsletter
about 18mm bottle cap engine retainers:

https://www.apogeerockets.com/education/downloads/Newsletter317.pdf

Just don't cut the round hole too large! It should overlap the casing slightly.

Some instructions on bending your own hooks from the steel in wiper blades:

https://modelrocketbuilding.blogspot.com/2010/07/make-your-own-engine-hooks-part-1.html
https://modelrocketbuilding.blogspot.com/2010/07/make-you-own-engine-hooks-part-2.html
https://modelrocketbuilding.blogspot.com/2010/07/make-your-own-engine-hooks-part-3.html
https://modelrocketbuilding.blogspot.com/2010/07/make-your-own-engine-hooks-part-4.html

On the forum, somebody had suggested finding the wiper blades the day after a rainy day.
I strip them right at the stores garbage can, just carry paper towels with you, they are dirty.
Not hard to find, they always stick straight up out of the top of the can.

The easiest way is just a masking tape wrap
From the blog:



"I don't like friction fitting engines, especially on a thin walled BT-5 or BT-20 tube.

The engine mount tube and engine both extend beyond the end of the body.
A simple wrap of masking tape will hold the engine in place throughout the entire flight.
Earlier, the extended tube got a coat of CA glue to keep it from peeling.
When the tape is pulled off there is less chance of the tube delaminating.
Be sure to press the tape down before launching."

 

[Micromeister]

There are an incredible number of great ways to retain Model Rocket motors.
One of the cheapest ways is using internal/external masking tape as hcmbanjo just described. Next cheapest is to bend your own Stainless steel motor retainers from the 3/32" strips on both sides of OLD discarded windshield wiper blades. All the material is FREE! you just need a pair of pliers and a hammer.
the attached pic & drawing may be helpful.

 

[Scott_mills]

Decent snowstorm bit, my wiper blade broke, so off to the auto store I go. Needless to say a lot of other people did the same, so I dove in the dumpster, for myself seven blades, and now I'm set for motor hooks for a few years to come. It wasn't even hard to pull the metal out, just a good tug with a paid off pliers will do it. Thanks for one of the awesomest tips ever.

 

[Rich Holmes]

So that's the idea I am looking for a bottle that will fit 18mm motor mount, but no success yet, Hydrogen Peroxide and rubbing alcohol bottles are a bit too small but I think can be sanded to fit. If you'll ever find one - post it

This thread turned up in the same google with this article: https://www.apogeerockets.com/education/downloads/Newsletter317.pdf

TLDR: Water bottle with short cap. Too large for 18mm mount, but he built up the end of the MM with cardstock strips to make a good fit.

I haven't tried it, of course.

 

[stantonjtroy]

.................. By the way a does anyone out there know the body tube lengths on the old Estes 1284 space shuttle, I need to replace the fin set, and the instructions didn't have the lengths specified.

1284 Space Shuttle BT-67GI 7.938" BT-46HI (2ea) 9.00" ST-76 (2ea) 6.50" 030332 BT-20DJ 4.00"
Got this from an ESTES Body tube reference list I have. Hope it helps.

View attachment Estes_Body_Tube_List.pdf