Tuesday, 28 June 2011


The thing i had to do today took longer than expected. I had hoped to be home by 1 but i only got back at 4. I worked on the new chamber till 10:30. I bought a new center lathe lathe to replace my small hobby bench one about two months ago and this is the first solid work out it has gotten. There always comes a time when your dragged out of the "honeymoon" phase with a new bit of machinery and today i was definitely dragged. I had quite a few issues with it in particular centring with the 3 jaw chuck. In a 3 jaw chuck the jaws move together when you spin any one of three keys. I was finding the work would be off centre sometimes by a few millimetres. I spent at least an hour trying to figure out what the problem was. The chuck itself was true so i knew nothing major was wrong but nothing seemed to make it better. Turns out that you have to tighten each key incrementally bit by bit, which makes no sense as they are all connected and turn together, but i think it would get jamed slightly when tightening. I have to say for the price i am not entirely happy with the quality of the lathe, and I  wont be buying any chinese machinery soon. Stil its a major improvement over the previous lathe, which was really too small for the size work i was doing.

Anyway so i got the new chamber nearly finished. All I need to do is cut the o-ring groves and dill and tap the threads to hold on the cooling jacket and injector assembly which will only take an an hour or so. I didn't bother putting in the groves and channels in  as they don't really do that much accept from look cool and there is more than enough cooling surface as it is. For the last couple of days I have felt anxious over the amount of work that needs to be done, finishing the chamber made me feel a bit more confident. The new chamber is identical to the old design but it has a big extra flange at the top for the injector to bolt on to. I didn't feel particularly confident with the last design as there is a lot of force on the injector and previously there was only 10mm of thread which i was afraid was going to shear. Unfortunately i couldn't get the broken drill bit out of the chamber i made last night so I had to start again. This one is much more centred also.

I am a bit worried about the extra flange melting as it is away from the cooling jacket. It also makes the chamber 3cm's longer. It will be near the injector so it shouldn't get too hot. Also i realised today after looking at another design that the oxidiser injector is on the outside. In most designs i have seen the fuel injectors are on the outside to film cool the wall. I am not so worried about cooling as the oxidiser oxidising the chamber wall. Space was really the drive to placement of injectors. There is one fuel and five oxidiser injectors. Since i am using spray injectors of the same size there isnt really a good way of  positioning them so the fiel is on the outsice without using diferernt sizes. I am already using close to the smallest spray injector i can find. So i guess i will keep the design as it is. I might do some more research into the issue.

I also ordered the type 30 fitting for the nitrous bottle, and it should be here tomorrow. For the next two days I will be away so i am not expecting to get a huge amount done but I will ahve a play with the xbees and try to get some of the test stand software done. I am having some troubles with python where it will freeze when i paste any code in to idle. It can pen and run saved code fine but pasting makes it freeze. Its really quite odd, i have found a few people talking about the problem and i think its a bug. I am just not sure how to uninstall/downgrade it (on a mac).

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