Making a fast response Drop Checker - The Planted Tank Forum
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post #1 of 26 (permalink) Old 03-16-2011, 07:03 PM Thread Starter
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Making a fast response Drop Checker

https://www.plantedtank.net/forums/fe...ml#post1326942 shows a one hour response time drop checker I made. Here is how to duplicate it.

First, you need to go to Ebay and buy an acrylic dome. Search Ebay for "acrylic domes", and look for the 3" diameter ones, which are first on the list today. The minimum order is for 6 of them for less than $10 shipped.

You need a slice of one of the domes, about 3/4 inch thick, running from the top of the dome to the opening at the bottom of the dome. I'll add a photo when I make another one.

I made this cut by first making a miter box out of some scrap wood, that let me jam the flat end of the dome against the bottom, and the side of the dome against the end, and one side of the box, with a front side attached so the dome just fit inside. I used a hacksaw with a fine blade to first cut a slot in the miterbox to guide the blade, then cut the dome.


The "left over" part is: It's big enough to cut another piece from it.


For the remaining parts, you need some 1/16 to 1/8" thick clear acrylic, which is sold as glass replacement for picture frames, at most hardware stores. If you can find white acrylic, of about the same thickness, that is best for the tray that holds the drop checker fluids, but you can also paint the back of some clear acrylic with white fingernail polish to make your own white acrylic. I can get the tiny amounts of acrylic I need from Tap Plastics free.

And, Tap Plastics also sells suction cups. I use the 1 3/4 inch size that comes with a steel "S" hook attached in a groove in the stem of the suction cup. These are perfect for this project. As I recall they sell for 50 cents each.

So, I'm off to make a few more of these, take some photos, and continue this.

Hoppy

Last edited by Hoppy; 03-16-2011 at 09:56 PM.
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post #2 of 26 (permalink) Old 03-16-2011, 11:37 PM Thread Starter
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Next, cutting and drilling the front "glass" of the DC, which also holds the suction cup.



I made a scale drawing of an ellipse that was 3 inches wide and 6 inches long, and used half of it as a pattern. To cut it out, I sandwitched it between two pieces of 1/4" hardboard, and used the pattern to mark the ellipse cut path. (Actually I sandwitched 5 pieces of acrylic because I'm making 5 of these at a time.) I used a fine blade in a hand jig saw to cut the sandwitch out. Some sanding was needed to clean up the cut.

To hold the suction cup, I drilled two 13/32 diameter holes about 3/8 inch apart, first drilling with a 1/16" drill, then a 1/8" drill, then a 1/4" drill, and finally the 13/32 " drill. This makes the drill cut only with the outer part of the drill to avoid melting the acrylic from friction. I used a small file to file the double hole down to a elongated slot.

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post #3 of 26 (permalink) Old 03-16-2011, 11:41 PM
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You guys have no idea how spoiled you are to have Tap Plastics...

Jim (who lived near Sacto from '94 - '03)


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post #4 of 26 (permalink) Old 03-17-2011, 12:52 AM Thread Starter
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You guys have no idea how spoiled you are to have Tap Plastics...

Jim (who lived near Sacto from '94 - '03)
I know exactly how spoiled I am! My last visit, I only needed one little 9" x 9" piece of clear acrylic. They gave it to me. No charge. It is a treasure. But, most of what they have you can buy online too. Not the suction cups, as far as I know.

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post #5 of 26 (permalink) Old 03-17-2011, 01:01 AM
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I used to go in there for one thing and come out with a bag full. My wife and daughter always like to go there with me. Also loved ABCSupply on R Street. Love working in aluminum. See aluminum/composite scope structure I built at www.jtmiller.com.

Jim


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post #6 of 26 (permalink) Old 03-17-2011, 03:27 AM
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Nice idea, I like how you used a jig to cut the ball.
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post #7 of 26 (permalink) Old 03-17-2011, 07:43 PM Thread Starter
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These are the 5 pieces of white acrylic to make the "tray" the standard KH fluids are in. The bottom piece is about 7/8" x 1 1/8 inch, the sides are 5/16" x 7/8", the back is 5/16" x 1 3/8", and the divider in the middle is 5/16" x 7/8". Cutting these is a little bit hard to do. I cut a long strip 7/8" wide by using a utility knife and straight edge, actually a small machinist's square, to score the acrylic. To get it to break along the line I find it takes 5-7 passes with the knife to get a deep enough score mark. Then I turn the acrylic piece over and score the other side the same way. To break it I clamp the 7/8" wide strip part between the jaws of my Shopmate workstand, right at the score marks. Then rock the top part back and forth a few times, and finally hold my breath and rock it all the way til it snaps. Sometimes the bread deviates from the score, and I have to start over, but most of the time it breaks cleanly.

Then repeat that to cut the strip to get 3 pieces that are 7/8" long x 5/16" and one that is 7/8" x 1 1/8". The final piece I get by cutting a strip that is 5/16" wide, and cutting off a 1 3/8" length of that.

There will be unevenness in the break lines, so every part that will be glued to another has to be sanded flat and smooth, by laying a sheet of fine sandpaper, 150 grit or so, on a flat piece of hardboard, and rubbing the piece of acrylic back and forth on it to sand the edge. To make eveything fit right, just sand the part or parts for the first glue joint, then after the glue dries, sand the assembly flat for the next joint. Etc.

Hoppy
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post #8 of 26 (permalink) Old 03-17-2011, 09:26 PM Thread Starter
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The two sides of the tray are glued in place with the glue shown. First sand the ends of the tray bottom flat and smooth, then use a strip of masking tape to hold the 3 pieces together as they should be. Then bend down one side piece, run a bead of glue along the end of the bottom piece and fold the side piece back in place and slide it to the right position. Repeat for the other side piece. Let the glue dry for about 45 minutes to an hour. It will be dry enough to handle much sooner, but the assembly has to be sanded, so you need more strength in the joint.

With the back of the tray glued on. You can see that a lot of sanding will be needed before doing much more. But, next will be the divider.

Hoppy

Last edited by Hoppy; 03-17-2011 at 11:33 PM.
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post #9 of 26 (permalink) Old 03-18-2011, 12:59 AM Thread Starter
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Glue dried enough for rough handling, and the face of the tray that is to be glued to the window/front/suction cup holder sanded smooth and at right angle to the bottom of the tray. The unimportant edges aren't carefully sanded, just a touch.

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post #10 of 26 (permalink) Old 03-18-2011, 05:26 PM Thread Starter
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The tray is now glued to the window/front/suction cup holder. I put a strip of masking tape on the back side of the window as a guide for where to position this. And, the location I figured out by laying the parts together to see where the tray needed to be to clear the dome part. To be sure this doesn't leak, I ran a fillet of extra glue along the outside of the joint after the glue had set for 15 minutes.

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post #11 of 26 (permalink) Old 03-18-2011, 06:46 PM Thread Starter
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Completely assembled, except for the suction cup. Installing that puts some stress on the assembly, so you need to wait a couple of hours for the glue to be nearly completely cured.



I made 4 of these, actually 5, but the last one needs some more work. I'm offering them for sale on the swap n shop forum.

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post #12 of 26 (permalink) Old 03-18-2011, 09:18 PM
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why two trays? is one going to be sealed to use a comparison of some sort?


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post #13 of 26 (permalink) Old 03-18-2011, 09:51 PM
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Two trays allows for two different drop checker reference fluids making for a differential aka bracket checker for more accuracy.

jim


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post #14 of 26 (permalink) Old 03-19-2011, 11:55 AM
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Quote:
Originally Posted by Hoppy View Post
Cutting these is a little bit hard to do. I cut a long strip 7/8" wide by using a utility knife and straight edge, actually a small machinist's square, to score the acrylic.
Have you tried cutting with a compound miter saw. I cut thick and thin plexi glass no problem with a 10" 64 tooth blade.
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post #15 of 26 (permalink) Old 03-20-2011, 12:50 AM Thread Starter
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Have you tried cutting with a compound miter saw. I cut thick and thin plexi glass no problem with a 10" 64 tooth blade.
I don't have a compound miter saw, just an inexpensive miter saw. I have in the past used power saws on acrylic and was never satisfied - the acrylic tends to melt and gum up the sawblade, causing still more melting. Probably because I only had wood working blades.

The hard and time consuming part of this was making the tray that the solutions go into. That takes 5 very small pieces of acrylic and about 3 gluing steps, each followed by hand sanding the ends of the pieces flush. So, I decided to try sections of acrylic tube instead. I have some 5/8 x 1/16 wall tube, so I tried that. First I made a jig to let me accurately cut off a length of tube, then cut it in half:
http://i573.photobucket.com/albums/s...f/DSC03337.jpg

I just poke the tube in the hole, cut off flush with the top of the jig with a hacksaw. Then cut that piece in half using the "miter" slot, with the hacksaw. It worked very well. The result is:


The two halves are glued to a small strip of white acrylic, by coating the face of that piece with glue then carefully placing the half tubes on that to glue them in place. Very easy. Finally, I painted the outside of the tubes with two coats of white fingernail polish.

Another laborious part was making the "window" pieces. This time I made a pattern out of 3/4 MDF, and clamped that on the squared pieces of acrylic (Lexan this time), and used a laminate trimmer bit and trimming router to cut them to match the pattern. I can cut the curve on a 8 inch long strip of Lexan, at both ends, then score and break off two "windows". Very much easier than the jigsaw method I used before.

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