lead weights
 

I was reading in 'Projects' about the Mars Snooper and using lead weight. They can be bought but I make my own. Cheap and easy.

Your local hardware,Lowes,Home Depot will have a flat washer with either a 1/2, 5/8, or 3/4 size hole, clamp the washer down on a thick piece of steel plate. Get some wheel weights and use a propane torch to 'melt' the wheel weight into the washer. Let it cool then drill a hole for the screw eye. Get the used wheel weights at any tire center, usually for free.

Semroc used to sell the "old-school Estes" style lead weights with the little center hole, but I believe they have switched to steel washers. Maybe you can still get from them if you ask.
Beware that most wheel weights are now not made of Lead. They are now zinc.
Seems the EPA is pushing everyone to be a lead-free WEENIE whether they want to be or not.
That gubmint organization is about as useful as a pogo-stik in a bathtub.

I remember back in the 1970s when I was a wee lad in the Cub Scouts a lot of us used fishing weights, tire ballancing weights, or Estes lead weights (these were easier to use due to the cylindrical shape) in Pinewood Derby cars to bring it to the regulation 5oz weight.

Speaking of which... info on weights for Pinewood derby cars.
http://www.abc-pinewood-derby.com/weights.php

I used to bite my lead sinkers to lock them onto my fishin line. It ain't affected me none...nope...not one little bit. :D

Most lead poisoning is actually not by contacting lead. Ask any stained glass window guy. It's lead added to motor fuels seeping into ground water and lead in paint being eaten by children. Solve those two known sources and we can reintroduce a valuable commodity back into society.

Tech Jerry

I still bite the split shot sinkers on to the line. That's how I was taught!

You can make the disks easily out of lead flashing. The only problem is that a whole roll is a little pricey and is more than you'd ever use in multiple lifetimes. Make friends with a roofer or mason. All you need is the scraps.

Elemental lead produces little toxicity unless inhaling finely powdered lead as it has little reactivity. Soluble lead salts and metallo-organic lead compounds (such as Tetraethyl Lead added to fuels) PRIOR TO BURNING are highly toxic. Once Tetraethyl is burned, the vast majority is left on valves/pistons as elemental Lead. Personally I do not think Lead should have ever been banned from regular motor fuel. It should be a PERSONAL choice.

I bought a sheet of lead from McMaster-Carr many years ago, plus a set of punches.

Once in a while I get bored and punch out a dozen or so circular disks. They are about half the weight of the old Estes lead weights.

The sheet lives on the floor of my storage closet. I handle it with gloves and wash my hands after I'm done punching out the weight.

I'd say that's an effective technique -- works better than biting the wax tadpole.


Hrm... speaking of dense material... has anybody considered using depeted uranium? ;)

I suppose the ultimate ballast material would be neutronium.

Nobody on this forum uses Neutronium anymore....those are old-school and passe'....we switched to Stinkonium and Unobtainium years ago. The results have naturally been Stellar !

Why not sand in a small plastic baggie? Leave it unzipped and let it spill out at ejection.

Sand is a far too cheap and plentiful material to have any business being used for rocketry.

http://www.youtube.com/watch?v=CD-E-LDc384

Sounds like a plan to me.

Hardee Harr Harr....

Jackie Gleason, right?

Anyway, I'm in the process of scratch building a 3" OD x 63" long rocket and it looks like I may need about 3-4 ounces nose weight to obain one caliber on the static CP. So I'm planning on the sandbag trick. I'll probably use a small paper parts bag as it will disintegrate soon after the first rain.

Or, maybe I could use dog scat? What do you think, GH?

How about lead shot mixed with epoxy ?

Dog poop belongs in flaming bags used for pranks.
I leave my ridiculous ideers/comments in the free-for-all section where they belong.
For True rocketry questions, I try to provide legitimate viable answers.

OK. Then dog poop it is!

Be my guest in flying Dawg-Krapp. Sounds like a real stinka of a flight.

Can dried dog $hit smell any worse than black powder residue?

In all seriousness, what I'm looking for is additional mass in order to shift the center of mass forward. By filling the nose cone with epoxy and lead shot, have I not created a solid mass capable of inficting significant damage to any object that it might impact should something go wrong? Additionally, I wouldn't be able to remove this mass should I use a lighter motor.

Why is lead, zinc or other dense material the only option? It seems to me that sand, dry clay or any other natural material either in the nose cone or in a bag would be a viable option. And cheap too!

Because it is dense and can be put at the very tip of the nose cone, allowing you to use less weight overall. If you use material that is less dense, it can't be placed as far forward (fills much more volume, including back toward the CP), requiring you to use much more weight than necessary. Due to it's increased weight and inertia, it could be more dangerous. A nosecone full of sand will rip you a new one just as fast as a nosecone with a little bird shot and epoxy.

The denser the weight, the less will have to be used due to the further fwd. position.
Osmium would be great, but it is not readliy available and would be cost prohibitive due to a cost of about $77/gram.

Ted,

You will probably want to wrap your ballast in a sheet of paper or plastic so that it scatters upon ejection. A bag of sand will hurt when it hits.


Bill

Understood. But I doubt that the entire nose would need to be filled to accomplish the shift of mass necessary in my particular case. Dry sand weighs about 100 lbs/cubic foot, cast lead about 708 lbs/cubic foot. A small quantity of dry sand in a baggie would strike me as less lethal than a hard slug of lead and epoxy at the point of a nose cone.

Now if GH is willing to be a test subject.....

Yes, it would. My idea was to place the sand bag on top of the laundry, leaving the bag folded over only once so that the sand would spill out into the air upon ejection. Were I to have an ejection failure and a ballistic lawn dart, all bets are off anyway and spectators should take cover. I know I sure will!

BTW, I've been testing my idea for ballast with powdered dried clay from my land. Really just fine dust. A small ZipLock sandwich bag 1/3 full weighs about four ounces.

Noseweight
 

Re: Noseweight

Here's some stuff I put together on noseweight.

http://www.doug79.com/noseweight/

It presents several methods for having adjustable weight. I prefer the weight to be nearer the aft end of the cone, for safety, but some of my older stuff shown here has it all the way forward.

Nowadays, I prefer to err on the side of safety - ie, to make the nosecones unstable - rather than trying to get minimal mass.

YMMV.

Doug

.

Thanks Doug. Those are some pretty nifty solutions to the problem but I'm pretty keen on my sandbag idea. What I really want to do is fill a payload bay with a litter of kittens just to see if they really do come down on their feet. Of course, that might be overkill.

You are planning to put the ballast in the body tube in front of the chute. That's way down the body, meaning you are going to need a boatload of sand (much more weight) to do the same job as a tiny bit of lead in the tip of the nose. The rocket will be very heavy in comparison. I'll take my chances with a few ounces of lead over a bucket of sand. All safety aside, you're getting into the land of diminishing returns if you add weight somewhere other than the nose. You need more weight....which means you need a bigger motor....which means you need more weight....which means you need a bigger motor. :eek:

Of course, if anybody has any sense, they will just take one step to the side and let the rocket hit the ground harmlessly, whether it has lead or sand as ballast. It's worked for 50 years, and even with very large and dangerous rocket ships. ;)

I'm willing to test-fire the rocket horizontally toward a cinder-block wall to test the penetration of sand vs. lead/epoxy. That's test-subject A-PLENTY !

During moments of non Safety Code compliant rocket activity decades ago I have seen them used to target humans on the other team. All they do on a direct hit is leave a welt. Model rockets are even pretty safe when intentionally misused.

Jerry

Back in the early 80's I knew of several TOY shoulder-fired simulated-bazookas with a "flour payload" using model rockets with D12 motors. Some had stick-stabilization (lousy on a horizontal plane), some had fold-out fins, and some had stubby fins. The folding-fin ones flew fairly straight. NONE of the launches were anywhere near vertical nor did they resemble anything close to the safety code other than most were electrically launched.

Thanks to all for your input.

After thinking things over in greater detail I've come to the conclusion that my sand bag idea is a bad one. Any object not secured into a fixed position within the airframe would surely slide rearward under acceleration and forward on deceleration. Not good.

I did experiment by placing exactly 2 ounces (57 grams) of loose clay powder within the nose cone and noting the shift in overall center of mass when the clay was all the way forward versus all the way aft. The nose cone is approximately 14" in length, tip to base, and the shift in CM was about 1/4" in favor of the forward weight. (I did place a spent AT G80 motor containing sand fill to represent liftoff weight in the motor mount.)

It looks like this bird will need about 3 ounces of something in or on the nosecone to acheive one caliber CM/CP, and it won't be in a bag.

Maybe I should stick to my political posts? ;)

Do you have any particular wall in mind? And, if we're going to waste a perfectly good nosecone, why not try one of your famous fecal tricks? :eek:

I will let you pick the wall. Build one specific for the test ?
Not sure how a 'fecal trick' plays into this though.
Dog Turd filled nose cone perhaps ?
YOU FILL it, and I will launch it toward the wall.

Seriously though, lead shot mixed with epoxy pours well into nose cones and is about the best material for adding noseweight.

Duly noted and this is the probable route I'll pursue. I'm not nearly as concerned about an ejection failure scenario as I am about improper CM/CP relationship.

Agree.
An ejection failure is an unlikely, but possible event.
An improper CP/CG relationship GUARANTEES an unstable and often disasterous flight.

Sometimes, it's not the lead in the nose but the rocks in my head that cause the problems!

Yesterday was a beautiful day here in North Tejas. Deep blue skies, light winds and temperatures in the upper fifties. So we loaded up my latest bird and headed up to a friends 15 acre flat pasture for a test flight of the unpainted airframe. I re-checked the CM/CP relationship and discovered that even without adding nose ballast I was good to go.

Empty weight was 816 grams sans motor. Installed G80-7T Estes/AT motor. Perfect flight, straight as an arrow. Ejection event....no chute! Then the sickening thud.

For some unknown reason I had placed the chute under the recovery harness and although the nose and harness ejected the chute hung up just inside the end of the body tube.

I shall rebuild. And next time, NO DRINKIN!

Ouch !