Hydrogen Generator

[ednisley]

round up a bunch of scrap aluminum

Yeah, but the lawn furniture was just sitting there...

[lem]

Jules wrote:
I know, but....remember the Hindenberg and all that..........

Hindenburg was 7 million cubic feet of gas, and a big volume of it was pre-mixed with oxygen at the tail due to a ripped gas cell. Even on that massive scale a lot of people still walked away from that disaster. An equivalent volume of propane or acetylene would have done a lot more damage.

But thanks to that damn video footage, Hindenburg spawn hydrogen phobia is a big mind virus that plagues hydrogen acceptance. If there was a video of a big propane production plant exploding, would anyone be more reluctant to turn on their grill?

Actually, the hydrogen was not the cause of the disaster. The hydrogen contributed to the fire, but was not the major player. The paint that they used on the Hindenburg was a reflective paint that contained powered aluminum.

For those that don't know, the solid rocket motors on the space shuttle were powered by, yep, powdered aluminum.

We use it in the model rocket motors that we build and test.

[Jules]

Well, don't blow yourself up with that either!

[pyronaught]

Actually, the hydrogen was not the cause of the disaster. The hydrogen contributed to the fire, but was not the major player. The paint that they used on the Hindenburg was a reflective paint that contained powered aluminum.

For those that don't know, the solid rocket motors on the space shuttle were powered by, yep, powdered aluminum.

We use it in the model rocket motors that we build and test.

Seven million cubic feet of hydrogen pre-mixed with oxygen was unquestionably the major player there. If the fabric dope was that explosive, the whole outer cover would have rapidly blown off first before the rest of it ignited, yet in the video you can see the cover just slowly burning away like the inert fabric that it was. Mythbusters also debunked the "thermite" fabric dope theory. Powdered aluminum is used in all sorts of auto paint, yet you don't see cars exploding from it. The Germans who designed and built zeppelins were some top notch engineers, they would have burn tested the fabric and rejected it if it were that explosive. If you are making rocket motors then you know you need an oxidizer in addition to metal fuel for it to burn-- a very high percentage of oxidizer for explosive burn rates.

[pyronaught]

I just had an idea is a bit unusual. Part of the problem that makes printing all these frames is that every hour you have to be changing out a part, which also makes it so you can't print over night so eight hours of machine time gets wasted each day. If the frames could be printed in a stack with break-away separation layer in between then you could print many in one session and also run it over night.

So I just made a model where there are two copies of the same gasket, one floating above the other with a tiny air space in between. S3D will actually fill the gap with the break-away support pattern, thus making it possible to print one above the other and still separate them. I haven't tried printing it yet, but I can't see why this wouldn't work. Since the top and bottom surfaces of all gaskets get glued together with ABS cement, these surfaces don't have to be particularly smooth. Because the gaskets are so thin, the entire stack of 30 could be printed in one session. If the print ever got hosed up by something, you would only lose the last part in the stack and still be able to salvage all those below it, unlike when a horizontal array of parts are printed and you lose the whole batch when something goes wrong.

Since these are flat and mostly long straight lines during the print, I've been getting away with print speeds of 6000mm/min and 80% of full speed on the first layer. What is the fastest speed you guys have ever tried?

[pyronaught]

round up a bunch of scrap aluminum

Yeah, but the lawn furniture was just sitting there...

My plan was actually to go to a machinist forum like cnczone.com and offer to beat whatever the scrap dealers are paying for lathe turnings and chips. Lathe turnings would have worked very well due to all the surface area exposed to the hydroxide solution. You'd really be able to generate a bunch of hydrogen fast with a rats nest of lathe turnings submerged in sodium hydroxide solution.

[Tim]

Since these are flat and mostly long straight lines during the print, I've been getting away with print speeds of 6000mm/min and 80% of full speed on the first layer. What is the fastest speed you guys have ever tried?

I generally keep mine set to 6000mm/min but I was able to double that without too much loss of quality. But that's with a Smoothieboard controller, which generally can get the same quality as the RAMBo with the speed about 50% higher (and that should be taken for the purely anecdotal evidence it is. . .). Also, I didn't shove a torture test at it for the 200mm/s run, just something fairly simple.

[pyronaught]

Here's something else interesting about this project that surprised me. The end plates on the cell are 5mm thick and printed with 100% infill at 265c nozzle temp. There is no visible gaps between the traces, it all looks very solid. When you fill the cell up with water, nothing leaks out. However, when you run the cell it is under a pressure of about 6 inches of water. That's a pretty low pressure, but believe it or not the internal solution will start sweating right through the 5mm plates in a few places! That's 25 layers of random infill orientation the liquid is managing to worm it's way through. It doesn't happen in very many spots, but I was pretty amazed it happens at all. Coating the entire cell with epoxy fixes that whole problem though. The edges where the plates are glued together leaked pretty bad anyway, even when not under pressure, but that part is understandable due to air pockets left in the glue holding them together. Pushing through 5mm of solid plate though, I could not believe that.

[lem]

. Mythbusters also debunked the "thermite" fabric dope theory.

Yep, looked it up again. Old information, sorry. While clearing up points, the powdered aluminum dope is not an explosive. Even many explosives will not explode if burned in open air. Depends on density and constraint. Water is not considered to be an explosive, but plug up a water heater and have the thermostat fail, no more house.

[pyronaught]

Since these are flat and mostly long straight lines during the print, I've been getting away with print speeds of 6000mm/min and 80% of full speed on the first layer. What is the fastest speed you guys have ever tried?

I generally keep mine set to 6000mm/min but I was able to double that without too much loss of quality. But that's with a Smoothieboard controller, which generally can get the same quality as the RAMBo with the speed about 50% higher (and that should be taken for the purely anecdotal evidence it is. . .). Also, I didn't shove a torture test at it for the 200mm/s run, just something fairly simple.

I always figured max speed was a mechanical limitation, such as mechanical ringing or the filament getting slung around at high speeds. How would one controller board allow higher speeds than another, are there some motion control algorithms at work there?