MM MachineScrew,Nut & Washer/Stud,Nuts&Washer Micro Odd-Rocs

[Micromeister]

Over the weekend I started two new Micro Odd-rocs. One a full size 3/8-16" x 6" Machine Cap Screw, the other a fully threaded 3/8-16" x 6" stud. both with Hex nuts and Fender washers Drag fin.
First thing I had to do was determain if I'd be able to find a material to produce or hold the Threads needed.
a short piece of 3/8 thin wall Polycarbonate tubing proved to fill the bill perfectly.
Hex Nuts and Hex Head will all be made with 22lb High density foam.
1-1/2" diameter Fender Washers will be either .063" Polycarbonate or paper laminated Basswood. We'll see what the mass of each end up.

The Cap Screw body and stuffer tube/motor mount will be standard T2+ & T3 (.375") craft tubing. I rolled a custom computer paper stuffer for the Polycarbonate stud do aid adhearing the motor stop/shockline mount and to help with the heat.
both have 3/8-16" x 1.0" Threaded Polycarbonate "Nosecones" with T2 Full length shoulders. this give me plenty of area for any noseweight that might be needed tho I do not believe any will be required.
.052" holes in the Nuts and washers will serve as Launch lugs.

The plan is to prime and paint both with Testors ModelMaster Stainless steel, buffed than future coated. Hope to get a few more of the pics out of the camera soon. Both models are almost ready for primers.

 

[Scotty Dog]

What kind of washed up,nut case,screw ball,stud would come up with that for a rocket?

 

[Rocketjunkie]

Something doesn't quite add up. You say you're using a T3 stuffer/motor mount tube. In a 3/8-16 bolt, the minor (root of thread) diameter is .300". I would think the ID of a tube thick enough to thread would me no more than 1/4", the motor size. Are you sure you're not making 1/2" bolts? Then I could see a 3/8" ID of the tube. (A 3/8-24 UNF bolt has a minor diameter of .325".)

Ahh, I see. The bolt has a paper unthreaded portion. That's the T3. There is no T3 in the threaded parts.

 

[MarkII]

Will the wonders ever cease? I half-expect that the next thing that you show will be something like a flying thumbtack! :wink:

Amazing job cutting the threads on that PC tube. The end result is astonishingly realistic.

 

[Micromeister]

Something doesn't quite add up. You say you're using a T3 stuffer/motor mount tube. In a 3/8-16 bolt, the minor (root of thread) diameter is .300". I would think the ID of a tube thick enough to thread would me no more than 1/4", the motor size. Are you sure you're not making 1/2" bolts? Then I could see a 3/8" ID of the tube. (A 3/8-24 UNF bolt has a minor diameter of .325".)

Ahh, I see. The bolt has a paper unthreaded portion. That's the T3. There is no T3 in the threaded parts.

Yes:
I'm actually building two verisons. a 3/8-16 x 6" Cap Screw (T3/T2+) body, and a 3/8-16 x 6" Threaded Stud (.375" od with an interior wall filed out to approx 1/32". A custom single wrap computer paper insert (CA Soaked) tube helps sheild the polycarb tube interior form ejection heat and give a surface for attaching the motorstop/shockline anchor.
As soon as I can caption a few of the additional pics It should become a little clearer

Thanks Mark:
These have been rolling around in my head for awhile, wasn't sure if the Polycarb tubing would hold up, very pleasently surprised Now to adjust the mass just a bit.
LOL! you do remember we already have a flying thumbtack don't you...Well; it is a 3X upscale but still a thumbtack. LOL!!!!!

 

[Micromeister]

here are a few more photos of both Machine Screw & Stud Odd-Rocs in the works.

Basic work on the flat polycarbonate Fender Washers, Threaded Nosecaps, and internal parts have been worked out.
Hope they look a little better after I get some paint or primer on them.

 

[Micromeister]

Working on the Stud interior, I want something other then Polycarbonate to glue the motor stop/shockline anchor to. A very thin 2-wrap computer paper (about .010" thick/wrap) was pre-curled around a 3/16" down then inserted and expanded to fill the void inside the 5" long Stud body after taking about 1/32" off the interior tube walls with around file. Once lined up the computer paper has been soaked with Med CA the full length hardening the interior against ejection heat and adhearing the tube to the inside surface of the polycarbonate tube. Carefully checking the fit for both MMX motor casings and T2 (.246") NC shoulder tubing. All seem good to go. I'll be adding the Motor stop/Shockline anchor this evening.

 

[Micromeister]

Fabrication of the Hex head & nuts is from 22lb High density closed cell foam.
cut from a 1" thick slab into a 5/8" x 5/8" block a razor saw and mitre box fashioned the necessary pieces and spare of each just in case

Wood glue was applied to the base of each piece then adheared to a piece of light cardstock. These pieces are cut apart and a printed Hex pattern wood glued to the face surfaces

The Hex Head and one of the Nuts for the Machine Screw will have .281" center holes dremel routed the cleaned up with a round file for a nice snug fit on the MS stuffer T2+ tubing. at some point these parts will be wood glued to the tubing.

All three Hex Nuts used on the Threaded stud will first be cutout and shaped then drilled to accept a 3/8-16 tap.
all 5 pieces will have .052" Launch lug holes drilled, these will be aligned, enlarged if necessary and fixed in place on both bodies after the Washer issue is decided.
I'm still debating the mass savings of laminating 1/16" Basswood over use of the polycarbonate discs already cut.

Shockline/motor mounts are about all that's left before primer & paint.

 

[Micromeister]

Finished both up. They're both just needed adding a Teflon streamer and taking the Upright stat's Photo's. Hope to fly both this weekend if the Wet Weather lets up

Odd-Rocs away!!!

 

[Micromeister]

Both Stud and Machine Screw are complete, swing tested and ready for their first flights next Saturday at our sport launch.

Hope to get at least liftoff shots of them. should be fun..... Odd-Rocs away!

 

[Micromeister]

Never got around to adding a couple Launch pics of these two Odd Rocs.
thought I'd update just a bit.

Both needed a tad more nose weight then originally expected but both are now flying quite well in light wind conditions, They do weathercock in breezed over 12mph.

 

[Daddyisabar]

Why is it always more nose weight needed than originally expected? I have never heard "oh that odd looking rocket needs less nose weight," or, "oh that odd looking rocket could use less power."

 

[Micromeister]

Very Simple:
We always want to keep the inital mass as low as possible. In calculating Cp-Cg most Scratch builders go for the minimum 1 caliber seperation as a starting point. Some designs sim fine at this point but in Free flight things ARE NOT Always as cut and dry. Other Aero factors come into play that often require tweeking the fin area or adding additional nose weight.
Genenerally the stranger the Odd-Roc the more likely the CP-CG relationship will be larger then the minimum. That is Way you can NEVER rely on simulations and Calculations only to guarantee stability in real world flight. Test flying is the ONLY absolute way to prove a design flight worthyness. Which is also why first flights are NEVER to be flown at Public Launches. They must be flown in as close to absolute isolation, with as few people on the range as practical. This is way "test Ranges" are alway Closed to the public

 

[Daddyisabar]

Golly geeeepers! I think must now be on triple secret probation with a cherry on top!

It is back to the back alley fer me. I hand my nose cones to the certified level three dudes and they just laugh.

 

[Micromeister]

thought you were asking a question about something you wanted to better understand. Sorry if giving the answer somehow made you feel uneasy.

 

[fyrwrxz]

Just dropping in to give props to two of my rocket heros! John, I really think you are a re-incarnated Swiss watch-maker and Daddy was Orville Wright.