nozzel mix formulas

[fred815]

It has been recommended to me to use hawthorne bond, wax and graphite?? Are the mix ratios critical. I imagine they are important? So what's a good place to start or whatever??

[WSM]

It has been recommended to me to use hawthorne bond, wax and graphite?? Are the mix ratios critical. I imagine they are important? So what's a good place to start or whatever??

 

I don't think the mix ratios are really critical until your end product's performance is critical. You can try a conservative mix to start:

 

80 Hawthorne Bond

12 graphite powder

08 wax

 

This is a hybrid of the boiled linseed nozzle mix from page 269 of the PGI Anthology, formula #1. By dissolving the wax and boiled linseed oil in liquid stove fuel (white gas or Coleman fuel) with a few drops of Japan drier, the linseed oil will polymerize much faster and the nozzle mix will be ready for use within a week. Boiled linseed oil takes about a month to air polymerize, otherwise.

 

WSM

[fred815]

Thanks, and that's just where I'm going to start!!

[dagabu]

I don't think the mix ratios are really critical until your end product's performance is critical. You can try a conservative mix to start:

 

80 Hawthorne Bond

12 graphite powder

08 wax

 

This is a hybrid of the boiled linseed nozzle mix from page 269 of the PGI Anthology, formula #1. By dissolving the wax and boiled linseed oil in liquid stove fuel (white gas or Coleman fuel) with a few drops of Japan drier, the linseed oil will polymerize much faster and the nozzle mix will be ready for use within a week. Boiled linseed oil takes about a month to air polymerize, otherwise.

 

WSM

 

12 graphite? WOW!!

 

-dag

[dangerousamateur]

12 graphite? WOW!!

What do you mean by that?

 

I'm using 10% and I feel that it helps a lot with lubrication.

 

And it's supposed to be very erosion resistant, amateur roketrists use it to.

[dagabu]

What do you mean by that?

 

I'm using 10% and I feel that it helps a lot with lubrication.

 

And it's supposed to be very erosion resistant, amateur roketrists use it to.

 

LOL! What I mean is that I buy #100 bags of clay and mix it all up at once so I have around #300 of nozzle clay all mixed and ready for wax. There is no way I am buying #30 of graphite to mix into the clay, it's just not that beneficial IMHO and adds a LOT to the price per pound to the nozzle clay cost.

 

Amateur Rocketeers use solid graphite nozzles and it has nothing to do with lubrication, it is very light weight and easily formed. It is OK for erosion resistance and is prone to pressure cracks but as before is easily formed to take advantage of the fuel you are using. Ceramic nozzles are harder, less prone to crack, don't erode and are light weight. Forget cutting them though.

 

I can understand those that use #10 of nozzle clay in a year but when making a flight of #3 rockets, you can easily go through #10 in a weekend (8 rockets per pound, 80 rockets in #10 of mix) and i certainly do at PGI. I do like the look but I think the wax adds more to the lubrication then the graphite.

 

-dag

[nater]

I have been rubbing a thin film of vasoline to the spindle, then dunking the lubed spindle into some graphite and using whatever sticks to the spindle. My nozzle mix is just hawthorn clay with wax. I think the small amount of graphite on the spindle helps the motors release much easier. I will mix up 100g of nozzle mix with graphite and wax and see if that is any better.

[WSM]

I have been rubbing a thin film of vasoline to the spindle, then dunking the lubed spindle into some graphite and using whatever sticks to the spindle. My nozzle mix is just hawthorn clay with wax. I think the small amount of graphite on the spindle helps the motors release much easier. I will mix up 100g of nozzle mix with graphite and wax and see if that is any better.

 

The quote from the PGI Anthology is:

 

55 "powdered clay"

35 graphite

10 boiled linseed oil

 

A friend of mine used this mix in fiberglass tubes (because regular nozzles slid out under pressure) and even when one CATO'd, parts of the nozzle were still stuck to the casing fragments! I believe the polymerized linseed oil goes plastic under pressure and flows around the nozzle grains and between the fibers of the casing, locking it all together. Another thing is the graphite which isn't affected by the exhaust gasses which sometimes have a (chemically) reducing effect on the oxides in the clay (depending on what's used for oxidizer and fuel).

 

Try it and see if it works for you. Don't forget to let the linseed oil polymerize or it won't hold together properly.

 

WSM

[WSM]

12 graphite? WOW!!

-dag

 

Hey, Dag;

 

You can use less if you want to.

 

Yeah, it costs more; but if it helps beyond just being a lubricant, it may just be worth it .

 

WSM

[nater]

I don't have any boiled linseed oil right now. I will get some and try the exact method from the anthology. What I ended up mixing up tonight was:

 

250g hawthorn bond clay

25g graphite powder

25g paraffin wax

 

heated at 200 for an hour, stirred the melted wax through the warmed mix, then screened through a 30 mesh screen.

 

I already have a tub plain hawthorn clay with 10 percent wax that works just fine for my nozzles.

 

Next day off work, I plan on milling a new batch of fuel and see which nozzle mix releases off the spindle the easiest.

[WSM]

I don't have any boiled linseed oil right now. I will get some and try the exact method from the anthology. What I ended up mixing up tonight was:

250g hawthorn bond clay

25g graphite powder

25g paraffin wax

heated at 200 for an hour, stirred the melted wax through the warmed mix, then screened through a 30 mesh screen.

I already have a tub plain hawthorn clay with 10 percent wax that works just fine for my nozzles.

Next day off work, I plan on milling a new batch of fuel and see which nozzle mix releases off the spindle the easiest.

 

The next time you make it, try sieving the clay and graphite together in a stainless bowl and heating it in an oven for 1/2 hour. Then with gloved hands remove the bowl and slowly pour the melted wax over the hot clay mixture and stir or mix till it's uniformly mixed. I believe this technique will work well and less of the wax will vaporize out of the nozzle mix while it heats.

 

Let us know how everything works out.

 

WSM

[dagabu]

I tried it that way once and had a real mess on my hands. The wax was melted and pourable, the clay was nice and hot, right out of the oven. When I poured the wax onto the clay, white, voluminous thick smoke immediately filled the entire area and boiled over in the pan leaving a sandy/waxy coating all over the sidewalk.

 

I am sure the the clay was way too hot and that is what caused the volcano but it spooked me enough to not try it again.

 

-dag

[WSM]

I tried it that way once and had a real mess on my hands. The wax was melted and pourable, the clay was nice and hot, right out of the oven. When I poured the wax onto the clay, white, voluminous thick smoke immediately filled the entire area and boiled over in the pan leaving a sandy/waxy coating all over the sidewalk.

I am sure the the clay was way too hot and that is what caused the volcano but it spooked me enough to not try it again.

-dag

 

I think you're right, dag. If you get the nerve to try it again, go easier with the heating and see if it works better.

 

WSM

[dagabu]

I am only using clay for endburners now, I have gone over to nozzleless rockets for BP and whistle now due to the ease on tooling and more fuel. Its really cool to top light a rocket with whistle fuel, if you only use 4-5 increments of whistle to start then mild BP on top, you can top light the rocket and it leaps off the rack just like a sali fueled rocket but only uses cheap benny whistle.

 

-dag

[nater]

I rammed a few nozzles using the mix I posted above. With the nozzles only, I can't tell a difference between the clay with graphite or using clay only when you twist the motor off the spindle. So far, the only difference is cosmetic.

[dangerousamateur]

LOL! What I mean is that I buy #100 bags of clay and mix it all up at once so I have around #300 of nozzle clay all mixed and ready for wax. There is no way I am buying #30 of graphite to mix into the clay, it's just not that beneficial IMHO and adds a LOT to the price per pound to the nozzle clay cost.

 

OK, I wasn't aware that youre working on such a large scale. For my perhaps 2 small rockets per week it does not matter.

 

I rammed a few nozzles using the mix I posted above. With the nozzles only, I can't tell a difference between the clay with graphite or using clay only when you twist the motor off the spindle. So far, the only difference is cosmetic.

Now please fire them and tell me the difference in erosion. Is there any?