Is this a failure mechanism for the molded fuel grains as well, or just something that is distinctive of the wound fuel?

I guess the molded ones have their own foibles for CATOs?

To be honest it wasnt that scary it was more I was pretty miffed haha But basically the CATO was caused because there was no adhesive on the fuel grain save the small strip. I guess you learn from mistakes right?

So I will be getting myself a can of spray adhesive before I next try to ignite it. aI am also planning on trying to put some aluminium filings in there too for extra sparks? The manufacturer told me about that one, he uses newspaper and spray adhesive with his paper grains, I am also going to be looking for a better way of ignition than the fuse.

My initial idea was to get myself a bottle of GOX and inject the gas directly into the combustion chamber, then placing a normal igniter at the nozzle opening, and ignition should hopefully provide instant ignition due to the heat and intense flame produced from an oxygen engriched environment.

Any thoughts?

Do you guys think it would it be possible to make a microhybrid "sparky" motor by spray painting one side of the paper with metallic fleck spray paint before rolling it up into the fuel grain?

Maybe. The chunks or particles would need to be large enough to stay together all the way through to the exhaust. Preferably metals like titanium are chosen for sparks for various reasons (high combustion temp and high melting point to list 2), but being a much smaller motor probably allows a large range of metals additives to achieve a noticeable sparky trail (maybe). I wouldn't expect a vivid shower of sparks from this though.
I've done a similar thing with much larger hybrid grains ie. laid up a roll of paper with a goo of resin (HTPB) & metals (Al, Mg & Ti) coated on one side as opposed to casting. It kinda worked ok, although I wasn't particularly after sparks for that.

TP

Hey all, I was thinking today, having watched some HHO Generator video's on youtube the other week simply while flicking through the related video boxes after click after click I was let to these HHO video's and if got me thinking, would it be possible to use the Hydrogen gas as a means of ignition?

http://www.youtube.com/watch?v=XVPUWvsim0g

I felt this would apply particularly to Hybrids due to the similar means of ignition from using GOX injected directly into the combustion chamber, was wondering if anyone else has any thoughts on this method, particularly because of the size of the Micro Hybrid you would not even need that much gas, and all the GSE consists of is a little glass jar, some water and a 9v battery with 2 stainless steel wires for the electrolyte plates so its extremely simple.

Nathan

I don't think it would work personally, I think it would burn off too quickly and not transfer much heat into the grain. Also I would wonder how much pressure wouldbe generated in the combustion chamber by burning gaseous oxygen and hydrogen in there.

Without running any numbers, I tend to agree with you Chris. The amount of gaseous H2 you could fit into that chamber will be SFA^SFA/SHLDs and it will burn too fast to transfer enough heat into the fuel grain and injected nitrous. The chamber pressure could potentially be reasonably high (I would guess) due to the incredible speed of reaction, but nah, it's not an avenue I'd be promoting with much confidence.

TP

Hmmm was worth a try

Just a tip for anybody who has a misfire with their microhybrid... be absolutely certain that the n2o bulb has vented before you attempt to remove the forward circlip... it goes off like a gun ! I'm not sure how far the bulb went, it was too fast to see, and there was no sign of it. Fortunately I did find my forward closure and was able to launch.

If you just back the grub screw out then it should vent?
I flew mine today testing out some last minute changes to the MAD code...
PK

It was venting but extreeemely slowly even after Chris had backed out the screw all the way and tapped the thing to try to get the bulb disengaged. It was my idea to just rip the forward closure off

Not sure how that would have happened, perhaps the burst disk O-ring had swollen up so much that the bulb was pushing onto the forward closure and couldn't lift up off the piercer assembly much (the O-ring pulled out from a previous attempt was very swollen, did go back down to its normal size after a few minutes though).

I had backed off the grub screw, but the o-ring had swollen up so much that it kept it sealed. No harm done apart from it frightening the bejesus out of me. I flew the MAD and it worked a charm!

I'm guessing that the forward edge of the burst disk/o-ring/piercer well isn't chamfered or rounded enough.

If it has no chamfer on it then the gas in the space between the piercer and burst disk will keep the piercer pressed into the bulb. You have to be able to back it all out to the point where the o-ring can blow out the increasing gap between the OD of the piercer and the well in the piston that's generated by that chamfer.

Which MAD did you fly Chris?

PK

It's only very slightly chamfered, when I made the part I didn't bother radiusing it, as I didn't think it was important. I'll go back and do it propperly I think. It's strange, I have never had that happen before.

The MAD I flew was your design, I like it a lot. Much better than the original MAD.

How do you think I figured it out Scared the bejesus out of me!

Tops!
PK