# Do a lot of people build their own engines?

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#### Japheth

##### Member
How do you design a engine? I can't find what the Isp of zinc and sulfur either...

#### Antares JS

##### Well-Known Member
I don't build my own motors but I have heard good things about this book, written by @prfesser right here on this forum.

#### Japheth

##### Member
Thanks, just ordered it.

#### 0011001100

##### A Person
There is a research section dedicated to experimental motors. But ZnS isn't allowed at Tripoli launches.

#### Japheth

##### Member
Do I need to be part of an organization to fly Class 2 or 3 Rockets? FAA Form 7711-2 requires an organization name.

#### dhbarr

##### Amateur Professional
Do I need to be part of an organization to fly Class 2 or 3 Rockets? FAA Form 7711-2 requires an organization name.
https://www.tripoli.org/Prefectures , recommend contacting a couple of local clubs to find out who does EX relatively close to you.

#### Japheth

##### Member
The closest is about 6 hours away.

#### Titan II

##### Well-Known Member
Do I need to be part of an organization to fly Class 2 or 3 Rockets? FAA Form 7711-2 requires an organization name.

#### dhbarr

##### Amateur Professional
The closest is about 6 hours away.
That's where the club is, but that's not necessarily where they fly or live

#### shockie

##### High Plains Drifter
How do you design a engine? I can't find what the Isp of zinc and sulfur either...
I think the very last thing you want to mess with is Zinc-Sulfur aka Micrograin propellant. It;s a very sensitive propellant. the Isp is poor too, 35 to 55. I would recommend sugar rockets aka Rocket Candy if you are starting out. Richard Nakka's site is great.

#### Japheth

##### Member
Sugar Rockets are good but its very mild propulsion, trying to avoid expensive fuels for now. Oh well, sugar will have to work. Any fuel work better with Potassium Nitrate?

#### cbrarick

##### Wildman CT
we can't discuss that question, but I can definitely state that the isp of sugar is very poor.
the other problem is that the difference between melting and ignition is low, so make it outside, away from anything you really want to keep.
It's really hard trying to explain it to your SO how you burnt down the house making rcandy.

where are you? Perhaps there's a club closer then you think, or at least a mentor.

#### 0011001100

##### A Person
ZnS has a lower ISP than sugar motors. Also be aware that sucrose can not be used for sugar motors.

As others have suggested you should fine a local club and at least get your L2.

#### Japheth

##### Member
I live in Northern Minnesota. There's a few down by the twin cities. So far I have been building E45 engines like the ones The King of Random made.

#### OverTheTop

##### Well-Known Member
TRF Supporter
I don't build my own motors but I have heard good things about this book, written by @prfesser right here on this forum.

I have the book and it seems to be quite a good intro into the safe making of solid motors with decent performance. A good starting point . Reading it right now!

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#### Titan II

##### Well-Known Member
Also be aware that sucrose can not be used for sugar motors.
At a Tripoli research launch.

#### GalantVR41062

##### Celebrate Recovery
TRF Supporter
I live on Plymouth on the west side of the twin cities. I am a member of Tripoli MN, and fly in North Branch MN at the sod farm.

They do have experimental launches, but I have not heard when they hold them, and I have not seen a Ex motor fly at the launch. I have seen a static test firing from a long way off.

You can work on getting access to the research section here on TRF.

~John

#### jbr

##### Well-Known Member
making motors is fun

M and N 98mm

#### ksaves2

Ummm, You need to find a local mentor who knows what they are doing mixing motors. If you expect to save money on propellant, as a small mixer, forget it. The hardware/single use casings, nozzles (phenolic or graphite), closures, chems and a mixer cost a fair amount of money. Oh, once a mixer or manual mixing bowl touches rocket fuel, it SHOULD NEVER EVER be used for food mixing ever again no matter how much one tries to clean it. It becomes a dedicated fuel "mixer" from there on out. Don't get any ideas of using your mothers electric mixer. She'll be pissed from the smell!

You seem to be new at this so I recommend you fly commercial motors, get experience with electronic deployment, obtain your Tripoli L1, L2 and mix with someone or a group that knows what they are doing, period! Like CBrarick mentions above in post #12 it is not allowed to discuss specific formulas on the open forum for a very good reason I agree whole-heartedly with. Don't bother trying to ask about specific mixes as you will get some very caustic responses. Zn/S is not allowed by NAR/Tripoli so you did expose some of your naivete on this matter.

As I mention above you WILL NOT save money by mixing your own propellant! Now yes, there are those that will argue that point and indeed if the investment in equipment is spread out over many club members OR if a person ends up mixing motors for YEARS, they will probably save some money in the long run but it will take a long time and a lot of flying to eventually realize some savings. At that point they are purchasing chems (chemicals/reagents) and consumables like liners only. I've noticed the price of these things have been going up lately.

The only reason to mix is to be able to fly a motor you've made and see that it performs well and accept the satisfaction that you've achieved something that not as many fliers obtain as long as you get the rocket back in one piece!

Oh another thing. If one mixes they're going to blow cases. Propellant runs hot, O rings fail, too many bubbles in the cured propellant that inadvertently increases the burn rate unexpectedly, a propellant jet melts out the side of the case or the motor just over pressurizes and pops out a closure. A lot can go wrong.

There are mixers who have had case failures and there are those who are GOING to have case failures so one needs an isolated area to ground test some of their motors before trying to fly them in rockets. Otherwise you'll blow or incinerate some of your flying creations. Oh some snap ring cases can get pretty pricey if you destroy them during testing.

It's not as simple as you think.

Kurt

#### ksaves2

Come on JBR. Surely you jest! Pretty stiff investment there in materials and skills I might add. Our now deceased prefect had two lathes, one for casings (with a 16 inch chuck!) and a smaller one for graphite nozzles. He had to get hardware for the big lathe so he could do smaller diameter snap ring motors but it worked. Said the big lathe came off a Navy ship. Had a plate on it that said, "Paint approved by War Department February 1941".
Members just had to give him the materials and he turned it for us. He learned from a retired machinist that lived next store to him. So sad when he passed. Kurt

#### HHaase

##### Siegecraft Electronics
There's also an NAR chapter in Grand Forks if you're ok with flying high power with commercial motors. Don't know if they have a field or not but worth at least checking with them.

#### beeblebrox

##### 8 C6-0, 12 D11-9, 20 D20-0, 20 E5-0, 3 Cinerocs
ZnS has a lower ISP than sugar motors. Also be aware that sucrose can not be used for sugar motors.

As others have suggested you should fine a local club and at least get your L2.
Sorbitol is better than sugar... ZnS is simply dangerous, best left for the amateur guys at Smoke Creek desert if they even do anything there anymore...

#### jbr

##### Well-Known Member
I used to sell casings commercially so all the machinery and building is paid for by profits
And about if it is cheaper, that all depends on when/what you bought your materials for
AP 200 used to be $3/pound and I have 600 pounds of that, it is now$10-12
HTPB used to be $20/gallon, it is now around$100, I have 4 gallons left

current prices of materials makes it a luxury to make motors
as to blowing up cases, well that is all about how hard you want to stress them
personally I can replace any I blow up and the only one I did manage to damage was a 38mm 48" motor

some that never sold

#### jbr

##### Well-Known Member
In a full M 98mm there is 10 pounds of propellant
you do the math based on my costs
AT M1939 is $670 my cost in AP is$30, liner is around that also, $10 orings, extra chems puts my price around$100

current day material costs puts it around $500+ so you save a little prove me wrong #### prfesser ##### Lifetime Supporter TRF Lifetime Supporter In a full M 98mm there is 10 pounds of propellant you do the math based on my costs AT M1939 is$670

my cost in AP is $30, liner is around that also,$10 orings, extra chems puts my price around $100 current day material costs puts it around$500+ so you save a little

prove me wrong
That's materials cost, not the total expense.

Nozzles and casings can be made...if one buys a large enough lathe. Otherwise one must buy those parts. And there is often a minimum purchase for chemicals, graphite, and aluminum casing stock. Lots of other odds and ends such as a large mixer (if one is making M-class motors), scale(s), personal safety equipment. And a proper place to work (no, the garage won't do, even with the door up; positive ventilation is required, i.e. blower or chemical hood).

How many casings, nozzles, or test stand parts have had a RUD---rapid unscheduled disassembly ---during testing?

Finally, most (all?) of my friends who have gotten into research motors actually spend more on rockets and rocketry than they would have if they had not made motors. One does not save money by spending more of it.

Best -- Terry

#### prfesser

Sorbitol is better than sugar... ZnS is simply dangerous, best left for the amateur guys at Smoke Creek desert if they even do anything there anymore...
Yes. Isp of Zn-S is somewhere between 30 and 60 seconds. Blackpowder, about 80 s. Sorbitol "sugar propellant", 130-150 s. Amateur APCP, 160-230.

So they're all lower than APCP but sorbitol propellants aren't that much lower. A 29-240 casing with APCP is a mid H-motor. Well-made sorbitol propellant in that size is likely to be nearly a full G motor, but could possibly be a baby H.

Best -- Terry

#### jbr

##### Well-Known Member
That's materials cost, not the total expense.

Nozzles and casings can be made...if one buys a large enough lathe. Otherwise one must buy those parts. And there is often a minimum purchase for chemicals, graphite, and aluminum casing stock. Lots of other odds and ends such as a large mixer (if one is making M-class motors), scale(s), personal safety equipment. And a proper place to work (no, the garage won't do, even with the door up; positive ventilation is required, i.e. blower or chemical hood).

How many casings, nozzles, or test stand parts have had a RUD---rapid unscheduled disassembly ---during testing?

Finally, most (all?) of my friends who have gotten into research motors actually spend more on rockets and rocketry than they would have if they had not made motors. One does not save money by spending more of it.

Best -- Terry
you need to look at my previous posts in this
I have all the equipment and it's not hard to buy cases from others if you go that route
cases you have to buy for commercial motors also, so we really can't compare that cost

garage is fine, my work buildings are fine, I have made over 400 pounds of propellant

#### Wayco

##### Desert Rat Rocketeer
Old argument that no one is going to win.
The original post has a question that is easy to answer.
No, most people fly commercial motors, some of which require some assembly, but nothing like what is being discussed here and now.
Come on guys, the OP is a beginner, we lost him 15 post ago.....

#### pbahorich

##### Active Member
TRF Supporter
Japheth,
Learn rocketry first, at least to TRA/NAR level 2. That way you can get your rocket back in one piece.
There are thousands of things to learn and this forum is a good place to start. Then move on to research motors. Yes, it's a hike to the North Branch, MN launch site but well worth it.

Also, from the posts above it should now be clear to you that Sorbitol "sugar propellant" is about 3X more powerful than Zinc-Sulphur, and about 10X less dangerous.

#### jbr

##### Well-Known Member
My point is that yes there are quite a few that make their own propellant and even fewer that make their own casings
Some of us are really deep into this part of rocketry but it is not for everyone and if you happen to save some coin great, just don't expect that to happen

my estimate is 1% to 5% make their own propellant, guessing less than 50 make their own casings/nozzles/end closures

the options become endless when you do as you can make almost any color in the rainbow plus black or white