[speed33317]

My black sample weighs more than the sand.

For the size of mine being appox 131th of a cubic foot
and it weighing about a pound I guess easily over 100 pounds
per cubic foot.

The sand bag says .5 cubic foot at 50 pounds so might be pretty
close with my primtive math :-)

I havent broken them yet, waiting for 5 days to be sure they are totally
cured. BUt so far I wasnt able to snap them with my hands.

[max_imum2000]

can u also test its thermal properties ?
can it stand high temp
maybe we can cast aluminum in it ?

[romihs]

Walter,

I have not given up with the testing, just have not made too much progress, so I have not posted anything yet.

I made another batch of E/Q with 8% epoxy by weight and adjusted the ratios of the quartz sands. The result is a little better than what I got in the first round.
I rigged up a vibrating table and used a Dremel tool to produce the vibrations, it's pretty good at producing vibrations...



The left one was built up in layers, each layer compacted while vibrating, the middle one was filled in one go and also compacted while vibrating and the third was just vibrated, I did have to level the top surface as the E/Q would not do it itself with vibration only.

What I noticed:
1) When I started up the Dremel (as it accelerated), the E/Q was quite fluid for a short amount of time before the Demel reached its set speed.
The Dremel is rated with a RPM range of 10000 to 30000, I used it at it's lowest setting, higher RPM's had lesser effects on the E/Q.
This gets me to think that the 4000Hz (4000 VPS) discussed earlier, might be too high, and that 4000 VPM (or RPM) might actually be the sweet spot for liquefying the E/Q mix. I will think up a way to make myself an adjustable (amplitude and frequency) vibrating table.
2) 8% epoxy by weight is too dry, at least for now while I don't have a process in place. I'll try a 10% mix next (actually, it's made already, just waiting for it to cure).


Regards

Sandi

[romihs]

can u also test its thermal properties ?
can it stand high temp
maybe we can cast aluminum in it ?

Max,

Most epoxies are rated to withsdand temps of about 80C, some are available that withstand ~200C. The major problem with regular epoxies is that they get 'softer' as they are heated, so they should be kept cool.

You can cast almost anything you want to into E/C or E/Q, but keep in mind the CTE of those parts compared to E/Q or E/C. This was discussed somewhere in this tread already, try a search on this thread.

Regards

Sandi

[walter]

Guys,
Very nice samples. Thanks for posting.

btw, I had not done any stress testing. The original idea was to work on max density, reinforcements, and then do the testing.

My primary interest is in beams, structural members, gantry type stuff. So, it may take a while..

Thanks and keep up the good work!

[romihs]

Here are pics of my castings

10% Epoxy by volume ratio, granite paver base dust-fines-coarse mix

10% Epoxy by volume ratio, quartz filter sand, clean all fine

Mixture was rammed into mold.

They measure 3.5 X 5 by .750

I will use this to cast my lathe bed. Most likely using the filter sand.

I have ordered the material to build the spindle.

Machined to a A2-4 spindle. With ABEC7 matched bearings, ebay score
ground ball screws , 3phase motor and VFD ,all ebay scores.

Finally going to get use all my ebay parts I couldnt get rid of :-)

I had bid on a Mirac for $4,000 , i think I will end up with much
more machine and probably save $1000 or more off that price
building something myself.

Speed,

Thanks for the results, they both look good.

I'm curious to see how your lathe bed will turn out. I got into E/Q when I started designing a lathe too....
I'll be first implementing this on my mini-CNC mill though, which I've already started building with ALU.

Keep it up!

Regards

Sandi

[Mcgyver]

Sandi, thanks for the work and posts, good stuff!

[brunog]

Walter,

I have not given up with the testing, just have not made too much progress, so I have not posted anything yet.

I made another batch of E/Q with 8% epoxy by weight and adjusted the ratios of the quartz sands. The result is a little better than what I got in the first round.
I rigged up a vibrating table and used a Dremel tool to produce the vibrations, it's pretty good at producing vibrations...

2) 8% epoxy by weight is too dry, at least for now while I don't have a process in place. I'll try a 10% mix next (actually, it's made already, just waiting for it to cure).


Regards

Sandi

Nice work Sandi,

What aggregate ratios did you use?

I also agree with you, 10% should have less voids.

Keep us posted.

Best regards

Bruno

[romihs]

Hello all,

Thanks for all the support!

I have de-molded the third round of E/Q.

The ratios used where:
Epoxy: 12% (I thought I was making a 10% mix, but after checking my ratios, I discovered that I actually did it with 12%% epoxy)
Small aggregate (0.18mm): 15.85%
Medium aggregate (0.49mm): 26.06%
Large aggregate (1.52mm): 46.09%

I used the calculator that Bruno had posted several pages back.

Here are the results of this mix.



The left (larger) one I built up one layer at a time, compacting each layer by pounding on it while vibrating it. Each layer was about 10mm thick.
The right one I had done in one go, compacted it by ponding on it while vibrating it.

As can be seen the surface is almost completely filled, which looks really good. The bricks need more effort to remove from the mold than with the previous two rounds of tests.
I noticed that the top 1/4 of the brick "looks" dryer than the rest of it. This I assume is due to the epoxy oozing to the bottom during curing.
I believe that this mix could be be made to pool epoxy on the surface if one can compact the Quartz well enough.....

My conclusions:
1) The epoxy ratio should be between 8% and 12%. 12% while the process of compacting the Quarts into the mold is not optimal, once this process is refined, this ration can be reduced.
2) Waxing the mold is important! (I know it goes without saying...) I'm thinking of methods of doing this successfully.
3) I need to devise a method to vibrate the mix. It needs to be adjustable in amplitude and frequency.

I went out looking for some kind of colour pigment which I could add to the E/Q, and found a brand of pigments used to die cement and concrete. I chose red, just to be different...

I have also been hunting around for a reasonably priced electronic scale. I'm currently using a standard kitchen scale with a resolution of 2g to weigh 100g of epoxy and 30g of hardener. This leaves me with an accuracy of 6% for the hardener, and the specs for this epoxy specify an accuracy of 2% or better....(chair)

That's about all for now.
I think that I will invest some time now in building a vibrating table. Will let you know what happens.
But I might end up making one mix with the red pigment, just to see how it turns out....

Regards

Sandi

P.S. I weighed two bricks of similar sizes from different test rounds:
Round 1: 486g
Round 3: 606g
Thats 25% heavier! WOW!! :banana: :banana:

[speed33317]

Before I do my destructive testing :-)

Just remember easiest way to remove an old iron bath tub
is to bash it with a sledge hammer to break it up.

I was actually beating the two together tonight pretty hard
and no damage to either other than a little sufrace blemish but no dents.

Heres is something to think about , the coarser the material the weaker
the mix will be, my theory less surface area of gluing surface.

If you spread out the fines one grain thick compared to coarse, same total cube volume which is going to take up more surface area?

Also I believe with a very coarse mix there are going to be alot of voids
just being filled with epoxy , waist??

And one more thing , how about using carbon fiber kite rods for
building a internal support frame. or just laying carbon tow yarn
in the mold as you pour in the mix. Super strong.

[lgalla]

More reading

Question
: What will happen to my casting if I use a larger aggregate?
Answer:
Using a larger aggregate may cause more surface voids because air is entrapped under the irregular shapes of this material. There is also a larger volume of voids between larger aggregate pieces than smaller pieces. It is therefore recommended that a smaller aggregate be used or that a smaller
aggregate be mixed with the larger particles. The smaller aggregate will act as a "roller system" to assist in turning the larger pieces of aggregate during vibration. It is recommended to use aggregate that passes through a number 50, 100 or 200 sieve.
THIS question is about concrete casting.
Larry

[lgalla]

Sandi
"I noticed that the top 1/4 of the brick "looks" dryer than the rest of it. This I assume is due to the epoxy oozing to the bottom during curing.
I believe that this mix could be be made to pool epoxy on the surface if one can compact the Quartz well enough".....
Or maybe the air pockets rising?
Larry

[romihs]

Sandi
"I noticed that the top 1/4 of the brick "looks" dryer than the rest of it. This I assume is due to the epoxy oozing to the bottom during curing.
I believe that this mix could be be made to pool epoxy on the surface if one can compact the Quartz well enough".....
Or maybe the air pockets rising?
Larry

Larry,

Good point! Hmmm...

Will have to give this more thought.

Regards

Sandi

[lgalla]

Walter,Sandi,Speed,are locked in the laboratory testing and hopefully having good results to post this weekend.Check my post #891 PDF for a vibrating table.
Larry

[romihs]

Walter,Sandi,Speed,are locked in the laboratory testing and hopefully having good results to post this weekend.Check my post #891 PDF for a vibrating table.
Larry

Larry,

Yes, it kind of got a little quiet on the forum....

Thanks for the document you posted, just haven't looked though the whole thing yet... but it does look interesting.

Regards

Sandi

[brunog]

Check my post #891 PDF for a vibrating table.
Larry

Larry,
the pdf is very informative, thanks.

I have a 1hp 3450rpm motor I want to use for that purpose, It's too powerful for the purpose but it's doing nothing right now. I am working on the adjustable weights with a block of HDPE.

Best regards

Bruno

[WilliamD]

What wax are you guys using on your molds?

[romihs]

What wax are you guys using on your molds?

William,

Until now I have not used any wax.
I use plastic containers to which the epoxy does not stick to too well...

Regards

Sandi

[WilliamD]

Thanks for the info! I will be setting up some more samples tonight.

[speed33317]

Ok its been a week since I made my mad mix :-)

Tomorrow I will destroy my bricks. ANd they sound like bricks when you
tap them together.

Nothing scientific just going to bash the H*** out of them until
they break :-)

Will probably do a compressive test also by parking my car on them :-)

And today after work I stopped by McMaster Carr and picked up my
rear bearing and cast iron bars to start on the lathe spindle.
I already had a duplex matched set of bearings for the head of the spindle.

Oh well the house will never get done now :-)