I was playing around with my hybrid, trying to fine tune the optimum mix pressure for my volumetric meter setup and I noticed I got three failure modes when using milk jug burst disks. My union is 1" and I was at 4X. For correct mixtures (at least according to my calcs) and slightly rich mixtures I ...

I got a chance to test my numbers and I found out that I was leaving out a Patm in there. I fueled up my hybrid as per the original equation above and no ignition. Then I tried the version that accounts for the additional atmoshpere of air already in the chamber and it worked! I just couldn't wrap m...

Oh yeah, I think you are on the right track there. Try checking out you locals dealers, you never know if you have something good in your backyard. I would throw a safety factor on top of those working pressures though because of the repeated shock loads. To do that, you gotta learn a bit more about...

I tried plugging is some test numbers into your Pm equation (the second one down) and I was getting slightly different results. It might be hard to figure out this discrepancy because we took different approaches. I used partial pressures and did not account for atmospheric pressure because it was o...

Mark - What you said about "air through meter" designs got me thinking! What I like about that idea is that I need only one ball valve and the procedure of operation would be shorter. One drawback I can think of is that there is more wasted fuel. But after calculating it, it's really not that much. ...

The reason why I provided that chart is because you can see how much of a drop in working pressure results from fastening pipes with threads. The chart you linked to on engineering toolbox is assuming the the pipe has no threads which greatly weaken the pipe. Yes seamless, stainless will be stronger...

First off I encourage you to look at this working pressure guide: http://www.wheatland.com/images/standard-steel-pipe/Working_Pressure_Ratings_081114.pdf If you use HDGT http://www.thehalls-in-bfe.com/HGDT/ you'll see that the pressure of a 10x hybrid will actually exceed the working pressure of sch...

Thanks for that advice D_Hall. I think you're right, afterall if I'm accounting for the itty bitty stuff, the altitude is a significant factor as well. I just gotta figure out how to work that into the equation... The most obvious effect that altitude will have is there is less concentration of oxyg...

I tried using the uploader, but I got this message in red text that it does not support .xlsx files. I'm glad you mentioned that about your shock pump! It makes me feel the value of what I put my energy into.

I admit I hadn't thought of that! I made one just now very easily, but I was thinking it would be great to have a calculator that also works for manometric metering and syringe metering too. Also with different fuels as well. I'm not sure how to attach my quick Excel calculator here though. Before m...

Hi Hybrid Spudders, I have been dissatisfied with the current approaches to calculating the correct amount of fuel for hybrids using volumetric metering. One, because they don't account for the volume of the meter itself, and two because they don't account for the volume of the dead space between th...

That looks mad powerful! What kind of velocity did you record on the chrono in your video with a golf ball?

There isn't any play in the barrel when locked because of the two points of contact. It is a similar sealing system to my most recent combustion cannon "The Jackal" where the wedge of the bolt slide forces the seal against both surfaces. For the laminating process I just used the standard brush-in-c...

I put the videos back up for your enjoyment!

Awesome looking launcher! I'm excited to see you're video. I looked through the thread you referred, but didn't see the big reveal on the lift-off valve mechanism. What are the trigger linkages made out of? What has been the most successful sealing material for the mechanical finger? Does the trigge...