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Discussion in 'Metals' started by BronxFigs, Apr 23, 2013.
Thank you all for the responses and recommendations. Now, it will be easier.
Estes rockets where one of the great blasts from my childhood. I never had a lot of money growing up so each flight was a carefully planned expense. After a bit the whole neighborhood (well two residents in driving range) wanted to watch to the extent the old retired guy actually purchased a few engines for me. Since my rockets where on the small size it was easy to over engine them. More than a couple flew completely out of sight one of which I found years later, still high up in a tree, while hunting.
Model rocketry is a different sort of hobby with a different sort of engine that leads to lots of excitement for a young kid.
I agree with others. If you figure out the cost per hour of the steel that may go into making a part, even high-cost material comes out pretty cheap. What other hobby lets you take $20 worth of raw material and spend 40 hours carefully machining it before you ruin it? It may work out to 50 cents an hour for that expensive steel.
You can go above the "D" engines provided by Estes. Once you get into the "E" and above they are usually empty reusable shells that you can use and reload. I loaded up to an "F" engine. I also witnessed a "J" launch where they had to call the local air traffic control for clearance. It is a whole 'nother hobby from making model engines.
Rocket engines are a form of internal combustion engines. The big difference being the fuel also supplies the oxygen.
In any event I'd did my rocket flying as a kid. Never had the money to do the big rockets though they are indeed very interesting.
I buy most of my metals at the metal mart where commercial and industrial customers buy there metal, they are crops or pieces left over from these orders that are too small for commercial sale EG: CR steel bar 1" dia 16" long and I pay 50% of new price, your local metal guys may do the same, I buy steel various grades, aluminum various grades, brass, bronze, copper, stainless. yes they don't always have exactly the piece I want but it really works pretty well and you then know exactly what you are getting, buying 1440 you get 1440... Make chips not more work
Brian, et al.
Thanks for the engine parts listing, and material choices for those parts. It helped. Now, I can start looking around for the correct materials, and hopefully make something that spins and pollutes the air.
I see nobody addressed the warping side of your question.
Metal parts warp because the metal removed upset the equilibrium of internal stresses frozen inside when the billet is made.
Cold rolled steel has more internal stresses that hot rolled steel.
The proper way to make a part is to rough all the cuts leaving oversize and then finish.
The more asimmetrical is a part the higher the chance that it warps considerably.
All metals warp not just steel.
If you really want to recycle keep in mind original use. And use for the same similar purpose. an old shaft from a printer can be used as a shaft for an engine.
Cast aluminum can be recast to a different shape.
if a piece was machined chances are it can be machined again. But beware hardened parts may tear up your tooling and cause frustration.
tornitore45 ...... warping issues.... thanks. Never gave it a thought except for steel.
@ all who posted..... Thanks for all the information, caveats, and suggestions.
McKinnon Metals in Toronto does this. Not sure I got 50% off but $20 got me a lot of CR steel and 6061 Al off cuts.
Someone stated that they recently built an engine from plastic and just thought I would add that some Honda copies coming from china actually have a nylon crankshaft in them..never thought that nylon could handle that much pressure even on a 6 hp engine.
Although I am a relative newbie, here are two things that I think I can pass along safely.
I am just starting to get into machining. But I have had a shop of sorts for years, and that shop has often been frustrating, particularly finding stuff. Now that I am a little older--and hopefully wiser--I am organizing everything, and it is time well spent. A paint-stick marker is worth its weight in gold. When I start buying materials, I will label each piece, so that a roughly-milled square block of hot rolled will not get picked for a piece needing a mirror finish.
Second--borrowed knowledge--I knew an old craftsman in a rural town who scrounged most everything. (He has no access to industrial remnants.) His machinery looked like the warehouse of a museum. But he did beautiful work. When he got ready to build something, he'd grab several possible candidates of scrap stock and head over to the grinder. He could feel how hard the material was and usually get pretty close to the chemical composition by studying the sparks coming of the grinding wheel. All the old blacksmith and machinist books had charts that showed what spark patterns various materials produced. I won't guarantee that new alloys wouldn't create some surprises, but his procedures are a starting point to eliminate at least some potential problems. And most of us have occasions when we have little choice but hit the scrap bin. How many suppliers are open at 3:30 Saturday afternoon?
That said, no doubt a good inventory of material of labeled, known composition is by far the preferable route for most folks.
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