The FORD Lounge

[ArdWrknTrk]

I was thinking the same thing, Gary.
Apologies as this has NOTHING to do with Blue Mule and is even tangential to photography.

Yes, you can hear the crack.
If you were directly under it (next to the pad) you wouldn't.
But the shock wave travels out as a cone.

And as RSO I felt this little 'experimental' propellant was enough of a risk to warrant 200' distance.

You may have seen some *schlieren photography if you are old enough for that sort of thing.


**** ah hahaha. Damn autocorrect again!

[ArdWrknTrk]

I DID get it back -numerous times- though I tagged it "Losing Proposition" because I thought I had NO chance of recovery.
Hard to imagine as you really don't see it as it leaves, but you do see smoke from the ejection delay while it's coasting.

It's sitting in a tote, along with the "fastest flight" trophy from that meet.

[Gary Lewis]

Moved.

Interesting on the "crack".  Wouldn't have thought about where you can and can't hear it, but that makes sense.

As for schlieren photography, I had to look that one up.  Interesting!  I've seen the results, but had no clue how it was done.

[ArdWrknTrk]

Ah!
Here we are.
I changed the title back for you...

It's the same phenomenon that you can see heat waves in the shadow of a flame.
Because the density of air changes (and therefore refraction) where molecules collide because it's too fast for them to slip out of the way.

[Gary Lewis]

That's cool!  I've never been around rockets, so can only imagine.  

[ArdWrknTrk]

Sure you have!
You just talked about your popcan rockets from 4th July.

There are rockets that work on explosive propulsion.

[Gary Lewis]

True.  Sometimes they go out of sight.  (And sometimes they split down the side and go almost nowhere.)  But they are fun and the kids and grandkids love them.

[ArdWrknTrk]

They'll be there before you know it, Gary.  😃

I guess I've got my inner geek on full display today!  
To me it's really cool how easy it is to visualize sound.
Like I said, above, my mind 'sees' and understands this stuff innately.

[Gary Lewis]

In the vein of the drag strip commercials of yore, Saturday!  BE THERE!

Yep, they hope to get here this Saturday and stay two weeks or so.  Given that, they won't be here for the 4th of July.  So maybe no "rockets" this year.

Over the years I've experimented with several approaches.  Rattle cans work ok, as do any other pressurized can.  But they are heavy and while they'll stand up to about anything short of a cherry bomb, they won't go as high.  And, there's a myriad of different sizes, making the launcher more difficult to design/find.

But the pop can/tennis ball combo works nicely as both are standardized.  And they fit together nicely, with just enough tension to contain the blast but not so much as to impede movement.

However, you are on the edge, as opposed to eve, of destruction.  Just a bit more explosive or a flaw in the material and it'll open up like a clam shell.  And, some of the extra oomph I've tried includes WD40 or propane in the tennis ball.  

[ArdWrknTrk]

PVC potato cannons!
Try ether. It works great.  🤔

Gary have a look at soda bottle water rockets.
All you need is a good bicycle pump and there's no danger of shrapnel or getting burned.

Find a way to have fun, just for fun, with the children.
Of course there's a physics lesson backloaded in there, so they might learn something.

[Gary Lewis]

Jim - There are BUNCHES of different ways to make those rockets!!! I'm gobsmacked with the variations.

But this one seems quite interesting. I've not yet figured out exactly how the release works, although I can see that the zip ties and coupler form a collet that holds the bottle until the coupler is pulled down. But how the coupler is pulled down isn't apparent to me, although in the still at the very start it looks like it may go under the central cross piece and then up.

[85lebaront2]

I had a water rocket as a kid in Norfolk, it had a pump that you actually launched it with. My brother was into the model rockets like you showed, we fired a bunch of the off when we lived in Virginia Beach. We used dad's WWII Navy binoculars to track them and once the parachute charge popped to figure out where it was coming down. We would launch them weekends and summers from the Shelton Park elementary school athletic field.

This is a story will interest you, one of my classmates at Norview was a very brilliant girl named Mary Edith Gress. Her dad fought with the school over the stereotypes that women should know how to cook and sew. During our 40th reunion she and I went and toured the labs, and found that some of the test tube wooden racks had been there at least 40 years. During this we were talking about the "test tube rocket", the experiment where you heat Manganese Dioxide (I believe) to generate oxygen. Everyone was warned to not let the tube cool until the line was removed from the collection bottle and to be careful not to set the rubber stopper on fire. Two girls who probably would have been better in Home Ec managed to draw water up the tube until it broke at which point they started heating again and set the rubber stopper on fire. End result, test tube with flaming rubber, came out of the clamp and disappeared through the open window with a nice whoosh.

[ArdWrknTrk]

And this (like shop class) is why we have dumbed down education in this country.

I've said before that some lessons SHOULD be painful.


Bill, the transparent red nosed one with a white base and canted fins, so the thrust was not vectored by a moulded defect and it was spin stabilized like a rifled barrel?
I LOVED those things!

Lemme see if I can find one....

[ArdWrknTrk]

I knew it had to be Wham-O

Probably gone the same place as lawn darts 'Jarts' .... because of idiots.

[85lebaront2]

Jim that is it, the game was to see (a) how much water you could get in and (b) how much pressure you could pump it up to. Fun because the "launch control" got soaked when it was released.

People wonder why we have a nation of wimps, lawyers are the problem with the "somebody ought to pay" ads on the boob tube.

[Dorsai]

ArdWrknTrk wrote

Yes, you can hear the crack.
If you were directly under it (next to the pad) you wouldn't.
But the shock wave travels out as a cone.

Ah, I remember the first time I got a rocket to break the sound barrier....I think it was a G motor on the lightest rocket I could build that would remain aerodynamically stable.  It shattered as soon as it hit Mach 1, I think I recovered a single fin.

Also...

And this (like shop class) is why we have dumbed down education in this country.

Shop class may be making a comeback, of sorts.  My son has an 'engineering' class that looks for all the world like what shop ought to be in the 21st century.  SolidWorks, 3-D printers, CNC mills, all the cool stuff.  He and another kid were building a leaf blower-powered hovercraft as a special project before Bat Soup Fever put a stop to it.

[grumpin]

We called them Polish cannons. Five pop cans, when they were tin, top and bottom cut out of four, a hole in the bottom side of the bottom one. Taped together, lighter fluid and a tennis ball as Gary mentioned.

Squirt fluid in it, shake it a bit, stuff the tennis ball in the top and light it in the little hole at the bottom.

It would shoot that tennis ball out of sight!

I was in the sixth or seventh grade and my teacher heard me talking about it. Asked me to bring in in and demonstrate it.

We went out to the football field and I lit it off. He had me explain what and why I was doing. Lit it off one more time. Got an A for that!

Cant imagine what they would say now if I brought one to school.

[Dorsai]

grumpin wrote

Cant imagine what they would say now if I brought one to school.

"Welcome to Guantanamo."

[grumpin]

Dorsai wrote

grumpin wrote

Cant imagine what they would say now if I brought one to school.

"Welcome to Guantanamo."

[ArdWrknTrk]

We used to bring our 22's to school, for riflery in the tunnel under the gym.

Ammo too!
Put them in our lockers until gym or after school.

And no one looked twice!
The riflery team were all responsible, and it wasn't viewed as a risk.

I really don't know what's happened to society, but everyone is scared.
Youth aren't even allowed to prove they can act responsibly anymore.

I'm going to stop now, before it gets to politics and ideology