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Old Sep 25, 2010, 03:13 AM
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Sri Lanka
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Home Made 2.5 g resolution micro scale

The use of a weighing scale is crucial for the building of a lightweight model.

There are some DIY scales at these sites

http://sci-toys.com/scitoys/scitoys/...e/balance.html

http://riceball.com/d/content/diy-postal-scale

I have developed a 'penny scale' that seems to be quite accurate. This is just a Proof of Concept and has to be developed further



What do you think? Is it accurate?
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Old Sep 25, 2010, 03:30 AM
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.1g resolution scales are less than $10 shipped on E-bay or from Deal extreme. That seems like a not a lot of acuracy and not a very productive use of time.
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Old Sep 25, 2010, 01:47 PM
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Might want to take a look at where he is from before making such a post. His access to some of these materials might be limited.
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Old Sep 25, 2010, 01:57 PM
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A zillion years ago there was a balance in the Scientific American, in the Amateur Scientist column that could weigh the graphite in a pencil dot on a paper that had been weighed before and after.

I made one in my office and it would also measure air currents that were way to small to feel. The more sensitive you make something the more it has to be protected from measuring everything.

Personally I would go with a balance. Measuring in the gram range is easy with balance.

A friend made a very fine caliper that is damn near as good as one that I paid $135 for. His is made of wood and uses rubberbands to pull it closed and the scale is written on paper after measuring a few samples. Mine has a larger range but his is pretty good for something thrown together in a half an hour or so.

Pete
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Old Sep 25, 2010, 03:08 PM
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Originally Posted by Aeroengineer1 View Post
Might want to take a look at where he is from before making such a post. His access to some of these materials might be limited.
Same with most of Africa right... it is called doumenteries, aka TV. If you have an internet connection and build small models, it wouldn't be hard at all to just get ytt another part from the internet.
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Old Sep 25, 2010, 05:26 PM
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Originally Posted by Aeroengineer1 View Post
Might want to take a look at where he is from before making such a post. His access to some of these materials might be limited.
The premise that all pennies weigh the same is a faulty one. I just pulled three random pennies from my pocket. Two weighed 2.5g the other weighed 3.1g.
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Old Sep 25, 2010, 06:23 PM
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The original pennies are ~3.1, the recent one weigh ~2.5, the newest ones (shield or building with guy for tails) that just came out weigh ?. It is because the original have more copper.
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Old Sep 25, 2010, 08:34 PM
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I've always used nickels as they weigh 5 grams.

Jay
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Old Sep 26, 2010, 12:12 AM
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Sri Lanka
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I have ordered stuff from e-bay before however it always makes business sense to cut costs when you can. For example $ 10 can buy me a new Li-po or a motor, even a plane. The small scales are available here in this country at Hobby Tech for about $ 12.

I really do want to avoid spiraling costs in this hobby, I know I have spent money elsewhere and not wisely.

The other consideration is that low cost scales or models or power sources will make the hobby more accessible for more people, especially young children. Once they get into it they will anyway start spending the big money. Maybe the better thing is not to get them started at all, and price these things out of range.

Anyway the scale was a lot of fun, and is helping me build a lighter wing. I am working on an improved model.
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Old Oct 27, 2010, 08:56 PM
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Sri Lanka
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Improved Version gram scale

My 2.5 gram scale is working fine, used it to weigh my wing designs for the free flight plane. Needs to be calibrated often, however.

Its main disadvantage is that it is inconvenient to use, which I plan to fix with the improved model, a proof of concept which was tested in cardboard

The design is pretty simple- a stand and a long arm at the top. The secret is that at the base of the arm a springy material is fixed, this deflects under a load.

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Description: Design for a gram scale
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Old Nov 02, 2011, 09:09 PM
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Sri Lanka
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http://www.rcgroups.com/forums/showthread.php?t=904951

Nice Harlan scale, I am building a new version of my own rubber powered one.
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Old Nov 03, 2011, 09:27 AM
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knlever,

I applaud your efforts. Back in 1988 I published an article in Flying Models magazine for a beam balance that used an American nickel (5 grams) as a weight standard. The balance worked fine, but I used a wooden beam, which changed balance when the relative humidity changed.

I recommend that you avoid using wood, so you won't have a change in balance when humidity changes.

Jim R.
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Old Nov 03, 2011, 09:45 PM
Just shut up and build!
Sri Lanka
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Hi Jim

Thanks!. What was the resolution of your scale? And Humidity - newer thought of that.
I would love to see your article or the gist of it.
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Old Nov 03, 2011, 10:51 PM
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Originally Posted by JRuggiero View Post
knlever,

I applaud your efforts. Back in 1988 I published an article in Flying Models magazine for a beam balance that used an American nickel (5 grams) as a weight standard. The balance worked fine, but I used a wooden beam, which changed balance when the relative humidity changed.

I recommend that you avoid using wood, so you won't have a change in balance when humidity changes.

Jim R.
Ever thought of putting a coat of dope or paint on the wood beam? Wood is a simple, cheap and durable material. Make the most of it.
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Old Nov 17, 2011, 07:07 PM
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Sri Lanka
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http://en.wikipedia.org/wiki/Weighing_scale

Some good stuff on scales, errors, etc
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