Saturday, January 31, 2009

Planning the machining...

I spent a good part of the day double checking my motor design before I start machining the outside.I’m glad I did, because without some adjustments It would not have been possible to machine the cooling slots.I ended up making a 3D rendering of the motor, the slitting saw and the bottom eand of the mill spindle. Then I adjusted things until only the cutting surfaces contacted the motor.In the pictures below the tool and mill is represented via the Gold solid as it sweeps along its cutting path.




The last picture shows the general layout.

  • Blue is the slitting saw center line path.

  • Black is the chamber

  • Red is the cooling channel depth.

  • Purple is the outer jacket (made in three pieces then welded back together.

  • Green is the size of the raw stock that will form the outer jacket



Anonymous said...

Since you don't etch your own PCBs' why machine your own chambers?
Send it out to, Since the economy sucks, there are plenty of hungry machinists our there
Just don't put rocket in the part description
(that triples the price)

Habitat Hermit said...

Looking at the three green blocks for the outer jacket and the purple outline of the resulting three pieces of outer jacket I can see how you'll slide on and weld the biggest two but how will you get the third and smallest outer jacket piece on?

Just curious, I apologize if it's a really stupid question ^_^

Paul Breed said...

Saw it in half then weld it back up.

Thad Beier said...

I am eager to see how this rocket works. I recall that Armadillo used a similar idea at first to build a regen chamber -- they milled slots into a chamber, and then built a jacket around it -- but I don't remember why it failed. It seems to me that it will be a challenge to seal all of the channels completely -- and there will be little way to check that once you have the outer jacket in place.

I suppose that even if the channels leak somewhat, all the fuel will still get to the right place eventually.

I was wondering, too, how you ensure that all the tubes (channels) get the same amount of flow. If they are off by a substantial amount, you'll have to have to over-design your cooling by that same fraction to make sure it doesn't overheat. Is there some feedback that makes it all sort of work naturally? Like, tubes that are flowing more slowly, get hotter, and the fuel is less viscous when it's hotter, leading to more flow in that tube?

I was wondering if you only have a small number of channels (12 or 16) might it be easier to cover each of them with a strap of steel going longitudinally along the motor, then bind the straps to the chamber with something like hose clamps..

Anyway -- if you can't tell, I'm really impressed by the work you're doing. Keep it up!

Paul Breed said...

The Outer gets boiled and the inner gets packed with dry ice...
Then assembled it should be a shrink fit so the liner and outer should be tight. (At least for the parts that go on whole.

As a peroxide motor I can start in monoprop mode and monitor cooling channel temperatures as I add fuel till it gets hot. I believe that the peroxide should give me a lot of cooling margin.

David said...

Excellent and Thank you for sharing. I will be interested to see the outside with the milled cooling slots before the jacket gets placed and welded. Using the temperature expansion differentials to assist with forming a tight fit is a clever idea. I would assume you would also machine the outer chamber 1 thou undersized as well. It would be an interesting exercise assembling the unit with the heat differentials and then welding it all. Tig welding (I assume your going to use) is not something that I personally have mastered. Your a man of many skills - impressive. Keep up the updates.