Help: Ideas for weight in conical

[Facinerous]

Didn't really know how to phrase the topic title, but since you made it here maybe you can help me figure out a best method.

I've been working on creating a fermentation monitor, much like the Beer Bug. The concept I have put together involves having a weighted object submerged in the beer during fermentation. I have been searching for a material/method of producing this weight, but many of my ideas have drawbacks.

Why do I need to produce my own object you may be asking yourself. I have spent hours scouring the net looking for something that would be suitable for this purpose, without success.

The specifics:
- The object must weight 120 grams. This is not an absolute. It could be a little more or a little less, but this is my desired weight.
- The object must have a volume of 100 grams. Once again this is not absolute. It could be a little more or a little less, but this is my desired volume.

Why the specifics:
I plan on using an arduino to calculate the specific gravity and temperature of the beer during fermentation. The desired weight and volume will give me the appropriate change in weight that is measurable by the arduino. I was going to utilize a solid object, but finding a solid material of suitable density is very difficult. If anyone know where I can get 1" solid extrusions of CPVC please let me know.

I'm looking for a solid material that is food safe, that has a relative density of 1.2, that can hold up to being in direct contact with beer for an extended time.

Or I'm looking for a material that is not solid, that is food safe, that I can machine/manipulate to have the desired volume and fill with something to achieve the desired weight.

Things I am considering:
I have already created one object which may prove the simplest and best. It is simply a 1" CPVC pipe capped on each end. It is filled with a material to get my desired weight. My calculations were no perfect in making this though, and I ended up with an object that weighs 121 grams, and displaces 95ml of water. Very close, but not perfect. Why am I writing all this when I have already created this object? I do not like having to use a CPVC glue. Unless someone more educated about this product can clue me in. I am currently hesitant about using this simply because of the glue.

The other possibility is glass. It has a density of 2.6, or there a bouts. The unfortunate thing about glass is I do not have the tooling to work with glass. I can not use a solid piece of glass because it does have the change in weight that I need when the beers specific gravity changes to work with the arduino. I have tried to get in touch with many glass workers, but there are a fickle bunch it seems. I may pursue this further, but I don't have my hopes up.

Finally, the question:
I know this is a bit of a long winded post.

My hope in writing all this out is to see if anyone out there has a good idea for me to create this weighted object.

Thanks for taking the time to read through this.

PS: All ideas will be carefully considered. Let me just say that I don't believe stainless steel will work, because its density is so ridiculous. Also I don't want to use copper, or really any metal for that matter, because of the potential corrosion factor.

 

[wbarber69]

The calibration weights for digital scales come in specific weight sizes and a 100-120g weight would probably be round about an inch in diameter.

 

[wbarber69]

http://www.amazon.com/gp/product/B002SVUBYE/?tag=skimlinks_replacement-20

 

[gstrawn]

Perhaps a pourable polyurethane? I'm assuming this is food safe and you could use cpvc and fill it with the appropriate weight of poly, even embedding the string/wire in it. You could seal each end with poly by allowing one end to dry. Obviously there some problems with this but you can control volume and weight.


Sent from my iPhone using Home Brew

 

[nebulous]

search for "solid rod" of what ever plastic you want. you might have to buy a pretty big piece, but then you can cut a variety of sizes for testing.

www.professionalplastics.com - HDPE
^ one of the first results when i put in "PVC solid rod" into google and then i poked around in the food handling section, HDPE is food safe just pick your size.




and "solid rod" jokes in 3, 2, . . .

 

[Facinerous]

Thanks for the replies everyone.

I had considered the calibration weight. They typically come in stainless steel. The unfortunate thing about this is it would not displace enough water to get a readable result with the arduino. The density of stainless steel is roughly 8.03 g/cm3 depending on the grade of the material. So in order to reduce the density of that material I would have to increase the mass proportionally. So for every gram of steel, I would need about 6.8 cm3 of volume. That would create a very large object, almost the size of a water bottle at 120 grams. Thank you for the idea though.

Pourable polyurethane is a fantastic idea. I will most certainly be looking into pourable materials that are food grade. Thank you.

Nebulous. Your link proved very helpful. The list of food grade materials is readably available and include all the information I would need. It also brought to light something I hadn't thought of originally. Simply the moisture absorption rate of the material. Something more I will need to investigate.

I did end up getting in touch with a glass person today. Actually turned out to be an old buddy from high school. I got a few glass samples from the guy and am going to run a few tests on the glass, along with the CPVC that I assembled yesterday.

My goal is to create a very easy way to create this weight, so I can create a DIY project for anyone to be able to easily create a specific gravity monitor. Or at least those interested.

Through the ideas supplied, and my own ideas I have a bit of work to do. Thank you.

If anyone else has an idea please post it up so I can keep the ol brain turning on this project.