My little J

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Re: My little J

Postby matt walker » Sun Mar 29, 2015 5:32 pm

Yep, saw 'em all. And you on top of a Bucky Ball. Love it! Really man, both this and your batch that I saw in person are some of the better castings I've seen out there. I appreciate that you take the time to attend the details that I can't be bothered with. I'm thinking this thing is going to sound like a tiny freight train. Have you seen this, from when Peter was developing those details you have there:

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Re: My little J

Postby matt walker » Sun Mar 29, 2015 5:34 pm

Oh, your other photos just have double IMG code tags. Photobucket puts them on already if you use their IMG link and then if you use the button here on the forum it puts them on again. That's why your photos aren't showing here.
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Re: My little J

Postby Bobwieser » Tue Mar 31, 2015 10:44 am

Matt, thanks for the complement on my castings. It' all new for me and I'm learning a lot along the way.

That Bucky ball (geodesic dome) came as a result of Thickstrings and you in one of his posts. I had lots of short scraps of 1/2" EMT and wanted a shed, greenhouse, jungle jim for the grandkids.

I fired up the new core with the riser sitting on top. It started nice and went smoke free quickly. After a while I could hear occasional pinging from inside.
I think it was from trapped moisture in the refractory.

There is a specific heating curve for proper firing of the material. I just mixed the feed tube with green twigs and damp sticks that were starting to poke out of the snow.
That stopped the pinging so I continued to burn with a mix of dry and wet wood to keep it hot for 4 or 5 hours. Nothing impressive since I didn't want to ruin it.
I looked inside the next day and see only ashes and a nice white surface in the core.

I did see that pulse mode video of Peters, I'll put a drum on mine to see if it will do the same. I think Peter likened it to an expansion chamber for a 2 cycle engine exhaust system and it needs a drum for it to happen.
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Re: My little J

Postby matt walker » Tue Mar 31, 2015 2:59 pm

That's 1/2 EMT conduit? Dang, I am surprised how strong it is. I shouldn't be surprised, but still...

Yeah, I always dry the castings the same way Bob, seems to work out fine. It is a bit nerve wracking when they really start letting out the moisture audibly like that though. Was it steaming off of the outer surfaces? I usually back off and let it get through that stage completely. Now that I think about it, it's a lot like cooking pancakes!
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Re: My little J

Postby Bobwieser » Tue Mar 31, 2015 3:22 pm

It's 1/2", I have to stand on or near the hubs or the pipe will bend. It held a deep snow load this winter with just a plastic sheet for a cover. Nice and warm inside it when the sun shines.

My refractory material is not porous at all. Because of that there is a greater chance of spalling or exploding during the initial heat up.
I did stand the 2 halves up on end and had an electric heater aiming into the feed with a cover over it for a day after demolding.
I didn't see any steam while burning and all seems good for now. I'll do a better inspection when I open it up.
I hope I don't regret not using needles. Maybe I'll get some for an 8" Id like to cast.
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Re: My little J

Postby rjdudley » Mon Apr 06, 2015 2:45 pm

Holy Crap Bob! And I thought your batch mold was impressive. Looks like the wife and I need to take a field trip and see these things in action.
Nice job, really, nice job.
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Re: My little J

Postby Bobwieser » Tue Apr 07, 2015 12:40 am

Thanks Ray. I am still experimenting with it outside. Your welcome to come see it or I'd be glad to bring it to a meeting of fellow rocketieres if your planning one. Let me know.
I sure did enjoy the one you invited me to.
Call, text, e-mail how to do it.
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