Rocket Size, Power and Cost

[OblivionFall]

Hi there, I'm trying to decide whether it would be more worth it to buy a whole arbor press and tooling.

 

How big of a BP is required to push about 500g? How much BP is packed into it?

 

Thanks I will then calculate the cost of an engine from that.

[mikeee]

It will vary depending on the quality of charcoal you use and the quality of BP you are able to make.

Most people will need to test each batch of BP or fuel to determine how "hot" the fuel is.

The other variable is the spindle design and nozzle or nozzleless design of the motor.

What works for one person does not work every time for another.

If you want reliable motors an arbor press or hydraulic press will duplicate fuel grain density.

Hand ramming will work but is hard to maintain fuel grain consistency.

[Col]

A hydraulic press and 1lb hybrid tooling would be my advice, fwiw. Arbor press will be a bit limited on power and height unless its a big `un

Edited November 27, 2015 by Col

[OblivionFall]

Ok I understand. I just want to know because I'm debating whether I should just stick with ROS-40 rocket engines for $1.00 each or if it is cheaper to make my own rockets. But I think cost and labor wise the ros-40 is the way to go.

[mabuse00]

If you want a good cost/payload ratio, whistle is the way to go (or maybe some hybrid...).

 

Especially if you can get cheap perchlorate.

 

 

Small tubes and small tool for whistle are cheaper than larger tubes/tool for BP with the same power.

 

 

How do you use ROS-40 engines, do you mod them somehow? IMHO the spin makes them unsuitable for pyro uses. I also read some reports about them beeing unreliable after some time of storage, do you have an opinion on that?

[schroedinger]

Mabuse, the spin holes on the ros-40 can be closed up with screws and the main hole needs slight enlargement. But like you allready pointed out the ros-40 is nit the most reliable engine.

 

Oblivion are you talking about 500g rocket header weight or whole rocket? If you talk just about the header you will need a 2 lb bp engine, or a 1 lb hybrid or pusher.

 

For the hybrid expect 10 g whistle and 50 g bp. Whith sali whistle 50 g whistle in the pusher. If you want a raspi sound a lws can be made to work.

 

If you only have benzoate, go for the hybrid rocket.

 

Also in you calculations remember that you will need a 3t arbor press and ptof gauge. A 1 t press won't give the reliable results you need. A hydraulic press is the better altantive. Take one allready fitted with a gauge and a real hydraulic cylinder, not a car jack. This way you can modify it later and e.g, use a electric fluid pump. It also enables you to make corned bp and use star plates reliable.

[mikeee]

An arbor press usually needs to be modified to handle the length of the tooling and motor.

They are fairly quick in producing smaller sized motors.

(Plenty of tutorials showing these modifications)

A standard bottle jack hydraulic press is cheap and handy to have in a shop.

They are very slow and tedious in producing motors.

An electric or air powered hydraulic press is the most expensive but is a very versatile tool.

This really speeds up the process of making motors, comets, stars etc.

[OblivionFall]

 

Especially if you can get cheap perchlorate.

 

 

How do you use ROS-40 engines, do you mod them somehow? IMHO the spin makes them unsuitable for pyro uses. I also read some reports about them beeing unreliable after some time of storage, do you have an opinion on that?

I unfortunately cannot legally get perchlorate where I live.

 

I just use the ROS-40 engine normally. I've used one before and haven't run into issues. What's the big deal with the spin?

Also yes I might just insert screws to plug the holes and stop it from spinning.

 

I've only have mine stored in a plastic bag for about a month now. Used one out of the five I bought about 10-15 days after it arrived. I assume these aren't brand new either and that they've been stored for a while.

 

I put on a rocket header that was at least 500g and it only flew about 100ft into the air. So I think I will use a much smaller header this time.

Also if storage is a concern it's no big deal. After all, they're only $1 each as apposed to the shitty $3 ESTES model rocket engines that are about 1/10th as powerful.

[OblivionFall]

I did the math

 

And a pound of BP costs me about $12.50 CAD to make (Cheapest KNO3 is $15 CAD per pound)

 

A pound of BP in the U.S. costs people usually about $2 CAD I think?

 

So that's why I think an ROS-40 Rocket engine is better for the price.

[Mumbles]

Being too lazy or not smart enough to find reasonably priced supplies is not our problem. Anyway, here's one example of KNO3 for $2/lb. You really need try harder. This took me less than 2 minutes to find.

 

http://www.earlysgarden.com/fertilizers/plant-prod-12-0-44

[OblivionFall]

Being too lazy or not smart enough to find reasonably priced supplies is not our problem. Anyway, here's one example of KNO3 for $2/lb. You really need try harder. This took me less than 2 minutes to find.

 

http://www.earlysgarden.com/fertilizers/plant-prod-12-0-44

Well if they ship to canada then gee golly I'll have to step up my pyro game!

 

EDIT: Holy crap they do. Can't believe I haven't found KNO3 for a good price with all of my google searches. I would like to thank you Mumbles. Things are looking up

The only reason I'm not really into pyro more is because of the $15/lb kno3 cost. Now I have no excuse

Edited December 1, 2015 by OblivionFall

[mikeee]

Some people actually make their own oxidizers which is cost effective if you have a hard time

getting them in your country. The way things are going it might be getting more difficult for many

people in the future with the current problems in the world. I put together a spreadsheet years

ago that broke down the cost of different sized motors and fuels. This allowed me to order bulk

chemicals depending on the quantity of items I intend to build each year. You can determine a

cost per gram/ounce/pound for your different fuels and then calculate by weight of your pressed

motors how much fuel is consolidated into the motor fuel grains. This calculation can also be used

for ball shells and cylinder shells when you build a list of materials that go into each product. Paper

by the square inch, square centimeter etc etc. Fuse by the inch, centimeter etc etc. You can even

determine how many stars go into a certain sized shell by the cubic inches/centimeters of shell and

the size of the stars and the area a round sphere of given size consumes inside a hemi.

[OblivionFall]

Some people actually make their own oxidizers which is cost effective if you have a hard time

getting them in your country. The way things are going it might be getting more difficult for many

people in the future with the current problems in the world. I put together a spreadsheet years

ago that broke down the cost of different sized motors and fuels. This allowed me to order bulk

chemicals depending on the quantity of items I intend to build each year. You can determine a

cost per gram/ounce/pound for your different fuels and then calculate by weight of your pressed

motors how much fuel is consolidated into the motor fuel grains. This calculation can also be used

for ball shells and cylinder shells when you build a list of materials that go into each product. Paper

by the square inch, square centimeter etc etc. Fuse by the inch, centimeter etc etc. You can even

determine how many stars go into a certain sized shell by the cubic inches/centimeters of shell and

the size of the stars and the area a round sphere of given size consumes inside a hemi.

That sounds like it would be very useful. I think I would have to make my own spreadsheet because of different costs of chems, fuse etc.

[Mumbles]

I find it better to for my own conscience to avoid thinking about costs. It helps me to avoid the mental conflict of thinking about how much money I am literally burning.

[schroedinger]

Oblivion the ros-40 engine can carry 250 - 300 g (whole rocket) up to 100 m. $

Maybe making your own engines is not as cheap as buying an ros, but you should also consider that the ros is a nc based engine, with no effect. In a bp rocket you will get a ro ket that is an effect it's own.

Your cost for one engine wil be about 0.5 $ for the tubes, the fuel and clai an other 0.5 $. So again 1 $ . + tooling + working time. But it is a whole different engine and it's hand crafted.

[nater]

I don't fret over the costs either. I know I could buy most product cheaper, but then I tend to make items that are not easily available commercially.

 

For rockets, I think the best balance between power and cost are 3/4" motors. I have a supply of extremely cheap K Benz and Na Benz, so whistles are the most economical for me.

 

For a 3/4" rocket with a ball shell, I have about $1 invested in the stick, tube and a hemi set before the propellant and heading materials. I don't know how much my cone headers or cylinder shells cost. I also never figured out how much a 1" motor costs to build.

Edited December 1, 2015 by nater

[schroedinger]

A 3 lb tube uses about 140 grams of bp, so you will end up with about 70 - 80 cents for fuel and clay (of course depending a lot on the charcoal and type of delay used, with an expensive delay like whistle with 20 % ti you will go up to 1 $) + 80 cents for a tube. Leaves with something close to 2 $. Not to bad i think. If you take commercial 2 FA with about 25 $ per kg and think of the fact that a 3 lb will lift a 6" which would require about 70 g 2 FA in a mortar, what would be 1.75$. Cost wise the same, attention wise the rocket catches the whole crowd.

[Arthur]

Remember that the propellant composition changes as the size changes, a smaller rocket will use hotter BP than a larger one.

[OblivionFall]

Ok so I think it is worth making my own rockets then

 

What tooling would you reccomend? I'll probably be making 2" canister and 3" ball shells. I will probably make an order of tubes, hemis, kraft tape etc from pyrocreations.com closer to the summer

Edited December 1, 2015 by OblivionFall

[nater]

I would use a 3/4" standard core burning BP set for 2" cylinder and 3" ball shells. Nozzled or nozzleless BP motors should lift those with ease. In fact an 8 oz or 5/8" motor would probably work too.

[OblivionFall]

Ok I gotcha. I'll probably go with 3/4" tooling. And I guess I'll have to buy an arbor press too?

[mikeee]

Not too hard to make basic rocket tooling for the smaller motors.

There are a number of tutorials on the process.

[OblivionFall]

Not too hard to make basic rocket tooling for the smaller motors.

There are a number of tutorials on the process.

How much would tooling cost? If it's pricey I could try nighthawkinlight's method

[OldMarine]

I find it better to for my own conscience to avoid thinking about costs. It helps me to avoid the mental conflict of thinking about how much money I am literally burning.

Doggone it Mumbles, I may snatch this for my signature! I'll give credit to the original author of course. Lol.

Edited December 2, 2015 by OldMarine

[mikeee]

How much would tooling cost? If it's pricey I could try nighthawkinlight's method

OblivionFall,

 

There are multiple ways to make different types of rocket tooling. You can purchase new tooling or post on the site that you are looking for a certain size of tooling. Many people sell off excess tooling when they need to finance other projects. A brass bolt and a solid base can be made into a basic tool. A drill press and metal file can be used to shape the brass bolt into a spindle. Some fuels can be carefully and slowly drilled with a drill bit to create a core. Some motors types don't even need a hollow core to fly. Visit several of the tool maker websites and study the types of motor tooling and you will quickly see the costs for the various types of tooling and supports. Most people will start with sugar rockets or black powder rockets, these types of rockets are the least expensive to get started with. Black Powder can be hand rammed and Sugar rockets can be poured or pressed. The website listed below has wealth of information on rocket tooling, fuels, and making basic tools.

 

http://wichitabuggywhip.com/fireworks/index.html