Hi Lasse here again, Its nice to see you adapt comments from youtube and aktivly improve your work. About working with graphite: slow and steady wins the race. I know it is tedious work but having your CNC spin slower (and your manual drill as well) will give you better results and less dust. Also, you have used some rather grainy graphite. If the graphite is finer you can have more refined edges and surfaces and the nozzle will also have greater strength. Since your construction is very solid and your nozzle is incased inside the tube, you dont need that higher strength but the clearer surfaces might make a slight difference. Anyways, great video like always and I hope you will reach the desired thrust values with the new and improved nozzles!
@@ExcitingCrapo you are doing stuff that we can only dream to have the time or resources to do!! Amazing work One question though... how is the nozzle permenantly fixed on the tip of the rocket?
@@FirstLast-tx3yj thanks for commenting it means a lot that you enjoy watching. I’m very lucky to have the time and resources every day is exciting for me in the workshop. The nozzle’s only have the two O rings sealing against the stainless chambers. They can’t come out because they are trapped in place with the large metal end plate. The same is going on at the injector end. Threaded rod keeps the plates under the correct compression 👍
@@ExcitingCrapo @@ExcitingCrapo what is the plan for these rockets? What will be the application? I have to mention that I believe hybrid rockets are the best for a "Budget project but the change in O/F ratio as it burns and inability to increase the amount of fuel without affecting the whole design of the chamber is complicated Although i have tried to work out some solutions but yet to experiment on them By the way tech ingredients had a great series on injector choice to increase burn efficiency did you watch that or do you have a different injector??
@@FirstLast-tx3yj I’m trying to get the engine under control and optimised for max thrust. Then I will build a 7m rocket. I realise a triple is not necessary but it will look amazing and that’s reason enough for me. I asked for help from a university rocket team in Germany who worked out the required surface area for 1000 psi oxygen injectors. Astra Bremen is their channel. I have completely redesigned the injectors and rebuilt my oxygen tanks and optimised my throttle’s. Should be ready to test at the end of the month. 👍
Hey there.. You really need a fully enclosed dust extraction system for machining graphite, otherwise the fine graphite dust will float through your whole shop coating everything and make its way into your electric motors causing them to burnout. Good luck with your upcoming test.
Good to hear from you Jamie. I haven’t seen any problems developing using a sacrificial O ring and my burn times at best would be not greater than eight seconds so very good to hear you managed twenty seconds. I definitely underestimated the mess caused by machining graphite. My shop floor still has black patches that appear after many scrubs. Next time will be a very different approach to the serious dust problem. Thanks for commenting👍
Having O-Rings in Graphit pets isn’t the best solution, the Graphit gets really hot and conducts the heat quite well, that will demolish the o-rings quite fast and create a potential leak. In hybrids it’s common to place the Graphit part into a Pertinax (phenolic paper) as a insulation material to hold onto the hot Graphit.
This is very useful and interesting information thanks for that. I have another test coming up in a week and will add that to my nervous pile as I’m somewhat committed.
There is nothing wrong with using o-rings to seal the external shaft of graphite nozzles, you just use several and assume the front end one will be sacrificial. I have sealed nozzles using NBR/Buna, EPDM & Silicone o-rings in hybrid motors past 20 seconds of burn time without issues.
Hi Lasse here again,
Its nice to see you adapt comments from youtube and aktivly improve your work.
About working with graphite:
slow and steady wins the race. I know it is tedious work but having your CNC spin slower (and your manual drill as well) will give you better results and less dust. Also, you have used some rather grainy graphite. If the graphite is finer you can have more refined edges and surfaces and the nozzle will also have greater strength. Since your construction is very solid and your nozzle is incased inside the tube, you dont need that higher strength but the clearer surfaces might make a slight difference.
Anyways, great video like always and I hope you will reach the desired thrust values with the new and improved nozzles!
Everything noted Lasse, thanks for the help.
We should be ready to test in approximately two weeks weather permitting 👍
Keep up the good work! Really enjoy watching.
It makes a big difference to read that you enjoy watching thank you for letting us know 😀
@@ExcitingCrapo you are doing stuff that we can only dream to have the time or resources to do!! Amazing work
One question though... how is the nozzle permenantly fixed on the tip of the rocket?
@@FirstLast-tx3yj thanks for commenting it means a lot that you enjoy watching.
I’m very lucky to have the time and resources every day is exciting for me in the workshop.
The nozzle’s only have the two O rings sealing against the stainless chambers.
They can’t come out because they are trapped in place with the large metal end plate.
The same is going on at the injector end.
Threaded rod keeps the plates under the correct compression 👍
@@ExcitingCrapo @@ExcitingCrapo what is the plan for these rockets? What will be the application?
I have to mention that I believe hybrid rockets are the best for a "Budget project but the change in O/F ratio as it burns and inability to increase the amount of fuel without affecting the whole design of the chamber is complicated
Although i have tried to work out some solutions but yet to experiment on them
By the way tech ingredients had a great series on injector choice to increase burn efficiency did you watch that or do you have a different injector??
@@FirstLast-tx3yj I’m trying to get the engine under control and optimised for max thrust.
Then I will build a 7m rocket.
I realise a triple is not necessary but it will look amazing and that’s reason enough for me.
I asked for help from a university rocket team in Germany who worked out the required surface area for 1000 psi oxygen injectors.
Astra Bremen is their channel.
I have completely redesigned the injectors and rebuilt my oxygen tanks and optimised my throttle’s.
Should be ready to test at the end of the month. 👍
Hey there.. You really need a fully enclosed dust extraction system for machining graphite, otherwise the fine graphite dust will float through your whole shop coating everything and make its way into your electric motors causing them to burnout. Good luck with your upcoming test.
Good to hear from you Jamie.
I haven’t seen any problems developing using a sacrificial O ring and my burn times at best would be not greater than eight seconds so very good to hear you managed twenty seconds.
I definitely underestimated the mess caused by machining graphite.
My shop floor still has black patches that appear after many scrubs.
Next time will be a very different approach to the serious dust problem.
Thanks for commenting👍
That is how you keep them in by rubber seals?
Having O-Rings in Graphit pets isn’t the best solution, the Graphit gets really hot and conducts the heat quite well, that will demolish the o-rings quite fast and create a potential leak. In hybrids it’s common to place the Graphit part into a Pertinax (phenolic paper) as a insulation material to hold onto the hot Graphit.
This is very useful and interesting information thanks for that.
I have another test coming up in a week and will add that to my nervous pile as I’m somewhat committed.
There is nothing wrong with using o-rings to seal the external shaft of graphite nozzles, you just use several and assume the front end one will be sacrificial. I have sealed nozzles using NBR/Buna, EPDM & Silicone o-rings in hybrid motors past 20 seconds of burn time without issues.
There is video by techingredients on hybrid rockets maybe that could help you
Thanks I did watch it and I picked up some good pointers.
It’s a very good channel thanks again for your input it all help’s 👍