Dual 18mm?

[James Pierson]

Is there a rocket design or kit that has uses dual ST-7 (side by side) motor mount tubes inside an ST-16 body tube? I have simmed it in Rocksim and it seems to fit, but barely. My concern is the centerings rings strength. There is not much of the ring left over at the sides.

Can anyone offer me a direction to head concerning this? :confused:

James Pierson
NAR# 77907

[Bazookadale]

If you glue the 2 ST-7 together, then glue them both to the ID of the ST-16 (might have to shim a little )this forms a strong motor mount on it's own , the centering rings would serve as a gas seal but don't need to be real strong as the tubes themselves will hold the load.

[tbzep]

Is there a rocket design or kit that has uses dual ST-7 (side by side) motor mount tubes inside an ST-16 body tube? I have simmed it in Rocksim and it seems to fit, but barely. My concern is the centerings rings strength. There is not much of the ring left over at the sides.

Can anyone offer me a direction to head concerning this? :confused:

James Pierson
NAR# 77907

There was one. The RX-16 from the Centuri Power System Outfit. It is a tight fit, but it will work as you can see in the photo. The motor tubes fit into the tube coupler to make a removable motor mount.

http://www.ninfinger.org/~sven/rockets/nostalgia/79cen008.jpg

[Doug Sams]

My concern is the centerings rings strength. There is not much of the ring left over at the sides.

Can anyone offer me a direction to head concerning this? :confused:
James,

A couple of strategically placed gussets will provide ample strength for the rings. In the pic below, you can see where I re-inforced the rings around the holes (thru which the retaining 2-56 all thread passes). These were rough cut from popsicle sticks, then sanded to fit. Even then, they're fairly crude, but more than up to the task. They don't have to be pretty, just strong. The key is adding the 2nd round of glue. Once in place, the force required to loosen them will likely wreck the rocket. IOW, if you break one of these rings, you'll have a lot more to worry about than just the motor mount :)

Doug

http://home.flash.net/~samily/better-bertha/YB_mmts4.JPG

[Intruder]

Is there a rocket design or kit that has uses dual ST-7 (side by side) motor mount tubes inside an ST-16 body tube? I have simmed it in Rocksim and it seems to fit, but barely. My concern is the centerings rings strength. There is not much of the ring left over at the sides.

Can anyone offer me a direction to head concerning this? :confused:

James Pierson
NAR# 77907

The biggest problem you'd have is getting them cut out and on the ST-7s without tearing. You could let the ring buldge out until you glue it to the ST-7s, then you can sand them till it fits. It'll have plenty of strength. Just ask tbzeb. He did it on his BT-60 (which is *VERY* close to ST-16) camera rocket.

[James Pierson]

Thanks for the great ideas guys. I have not decided which technique I am going to try yet.
I love all the photo's as well, good stuff!

James Pierson
NAR# 77907

[tbzep]

The biggest problem you'd have is getting them cut out and on the ST-7s without tearing. You could let the ring buldge out until you glue it to the ST-7s, then you can sand them till it fits. It'll have plenty of strength. Just ask tbzeb. He did it on his BT-60 (which is *VERY* close to ST-16) camera rocket.

My own son can't spell my screen name. :rolleyes:

[Intruder]

Leave me alone. :p

[garmtn]

Nice photos! Not sure what size motor fits an ST 7 though? I'm trying to build my own engine mounts without a body tube. Have an idea but, looking for more. Anyone find an off the shelf product, that uses a 24MM card board tube? my idea is to use a "pringles can" for the exterior housing. It must couple to 3, BT 20 clustered body tubes on one end and hold a "D" engine mount on the other. You may be wondering why bother? No $$ for a bunch of parts and want to try "recycling" garbage into rocket components. Will welcome all ideas for bother housing and engine mount. :confused:

[STRMan]

You better do a really good job cleaning up that Pringles tube. If the ejection charge sets off that oily residue, you may have one big, bright fireball on your hands.

[Thruster]

You may be wondering why bother? No $$ for a bunch of parts and want to try "recycling" garbage into rocket components. Will welcome all ideas for bother housing and engine mount. :confused:
Dude these parts are like around $1 a piece, your time and the engines are the most expensive part of this hobby so you might as well do it right. :)

[tbzep]

Nice photos! Not sure what size motor fits an ST 7 though? I'm trying to build my own engine mounts without a body tube. Have an idea but, looking for more. Anyone find an off the shelf product, that uses a 24MM card board tube? my idea is to use a "pringles can" for the exterior housing. It must couple to 3, BT 20 clustered body tubes on one end and hold a "D" engine mount on the other. You may be wondering why bother? No $$ for a bunch of parts and want to try "recycling" garbage into rocket components. Will welcome all ideas for bother housing and engine mount. :confused:

I buy tubes, but I make my own centering rings and turn most of my nosecones and bulkheads for scratch built models. I have some pringles cans and other cylindrical containers saved up for their odd sizes to help with scale projects, but I haven't gotten around to using them yet.

I know of several people who have plenty of money, but still enjoy coming up with ways to make models out of things that most people would throw away. If you enjoy doing it, keep it up.

[garmtn]

Hi Starman: Just so happens a "toilet paer tube," fit my needs exactly. Now I'm going to use the pringles can as a circular fin. Hot gases from motor won't be anywhere near it, except on bottom. I'll heed your advice though with a layer of shelac on inside of ring. Thanks for the concern. :rolleyes:

[Green Dragon]

The biggest problem you'd have is getting them cut out and on the ST-7s without tearing. You could let the ring buldge out until you glue it to the ST-7s, then you can sand them till it fits. It'll have plenty of strength. Just ask tbzeb. He did it on his BT-60 (which is *VERY* close to ST-16) camera rocket.

Semroc has the laser cut dual ST7 into ST16 rings right on the site.

In fact ( Carl, if you;re listening, lol ) I ordered them my mistake off the 'rings' page - it just lists 'pair of ST7 to ST16 rings', if you click the 'view' before you add to cart, THEN it specifies it's a cluster ring. ( but not from the main 'rings' page, hence my error.

Now I will HAVE TO add this power system RX-16 bird tot he build que ... anyone have more info, plans ?
maybe Centurious fins ? ( or entire bird ? )

~ AL

[James Pierson]

I looked for a half an hour Al and had no luck finding an #7 to #16 dual 18mm ring set :( . I found an dual, tripple, and quad 24mm but no dual 18mm. I see that the Defender is a tripple 18mm though, but no daul.

Thanks for looking, JP

James Pierson
NAR# 77907

[Green Dragon]

James,

looked again right now, and yes, they might be overlooked .. only reason I know they have em, is I ordered by mistake from the main 'rings' page.
here is the direct link to the rings,

http://www.semroc.com/Store/scripts/prodView.asp?idproduct=1432

I did send a note to Sheryl, so hopefully the main page will have a note these are CLUSTER rings, so they can both be found easier, and not mixed up as I did . ( and yes, she already promised to send my the 'correct' single ST7 to 16 rings, and it was MY fault... no wonder I see posts a lot re: how good these guys ( gal ) are :)

have fun building

~ AL

ps: is it me, or is Ninfinger down today ? I tried direct to get info on this bird / system and the pics ( above )isn;t there ( assume it might've direct linked to ninfinger ? ).

[James Pierson]

Thanks Al, your are my hero ;) .
They are listed as (CR-716X2) and I just added them to my cart.

Happy New Year, JP.

PS. Ninfinger works fer me on my end.

James Pierson
NAR# 77907

[Mark II]

Nice photos! Not sure what size motor fits an ST 7 though?...:confused:
ST-7 has the same ID as BT-20, but a slightly larger OD (IOW, it has a heavier wall thickness). So a conventional 18mm motor will fit it just fine.

Mark

[Solomoriah]

I built a two-cluster Baby Bertha a while back, and yeah, the centering rings aren't much on the sides; in fact, I just went ahead and cut them into halves and glued them on separately. After gluing into the main BT they were pretty sturdy.

I've collected parts for a rocket I'm calling my New Centurion. It will have interchangeable engine mounts (1x18mm, 2x18mm, 1x24mm D/E), a bypass-tube baffle, and a "midline break" just above the baffle. The standard Centurion paint job was dark on the upper end, light on the lower; I plan to paint mine just so, but the only seam on the entire sustainer will be right where the colors change. I'm always looking for ways to eliminate the Visible Nose Cone Line (VNCL).

I may start assembly tonight, actually...

Also... on my website is a centering ring generator that might be of some assistance:

http://rocketry.newcenturycomputers.net/cluster.html

Here's what the dual #7 to #16 rings look like:
http://rocketry.newcenturycomputers.net/cluster.cgi/s16.n.2.s7.png