Continuing on the stand build.
Before embarking on construction I needed to get a geardrive motor and plan the gearing. What size? I needed the torque required to turn the crank on a jack under the expected loading.
To empirically get this number I drove to the local building material store that has a truck scale. The readout is on the wall. I backed up so my bumper was hanging two feet over the truck scale. I placed a jack under the square tube steel bumper on my one ton diesel pickup truck so jacking up my truck would press down on the truck scale. Meanwhile I could read the actual weight I was lifting directly from the scale.
I jacked until I had 1/4 of the aquarium weight reading on the scale. Then I positioned the jack handle so it was at the 5 o'clock position. Using a spring hand scale I pressed upward on the jack handle until I got smooth motion going. Then as the handle passed thru 3 o'clock I read the spring scale number. That number multiplied by the crank handle length gave the actual torque value needed to crank a single jack in my future setup. (Theoretically)
Here it is assembled and painted.
Painted... Let me tell you about that. I went to the local industrial/automotive paint supplier. I like bright things, (or I would go fresh water -
), so I picked International Orange. I love the color. It's DuPont two part polyurethane.
The paint was $60 for a quart. I have bare metal.. So I'm told I need primer.. Primer costs $190 for a quart! That was a non-starter. So I asked what else might work as primer. The counter man told me metal etching sub primer and a primer that goes over that. Each can was about $10 bucks, 4 cans.
I cleaned all the metal with lacquer thinner and set up my airless sprayer. Then I etched and primed. Waited as instructed and then painted everything.. and I mean EVERYTHING.
My whole shop was over-sprayed. My phone, my hand tools, my.. everything.
Once the paint had hardened and cured I discovered that it chipped off of the primer with great ease!!! :furious:
What really hacks me off is that the over-spray that landed on bare uncleaned metal is permanently bonded to whatever it hit. Unused tube that it landed on has to have it GROUND off if you want it off.
So now I must treat my stand with kid gloves BECAUSE I listened to that idiot and did $40 of priming with incompatible primer. Live and learn. If you use the DuPont Polyurethane DO NOT bother priming. It is awesome by itself on any metal.
Let me point out some highlights. This is the view from the back as that's where all the action is.
B) Is the control panel. I will eventually need to extend it some. It has the VFD and a breaker for the geardrive motor mounted on the front side.
A) Is the three phase gearmotor (SEW). It's 1/3 hp with a 158RPM output. It's a metric motor so the shaft was 20mm(?). Anyway I was using American chain and sprockets as they are more common and cost less. So I machined out the hole of a smaller ID sprocket to fit the shaft. When I was done I'd gone too far. So with the keyway and set screws the sprocket went around in an oval. NOT GOOD as that implies de-acceleration and acceleration. 3000 lbs? Bad. So I had to get a new sprocket and do it better.
J) Is the aforementioned sprocket.
K) Is the primary chain. It drives two single sprockets on the left. Then the second sprocket drives an identical sprocket on the right side. This provides the same ratio so no hanky panky ensues.
D) Is the secondary chain that drives the right side. To get the chain right I had to use a half-link.
C) Are the diagonals for anti racking. Note no front anything. The front side of the feet are only constrained by the indexed top where it drops into the tops of the jacks. (F)
E) Are the front-back anti-racking.
A very important point to note is that this stand and its racking are backed up by the aquarium being constrained inside of the fireplace chase. The tank can only move backwards about 2 inches and sideways only about a 1/2". So an earthquake hopefully won't result in a BIG problem.
L) Is the outside jack tube. M) Is the inside sliding tube. N) Is the static height adjust that lets you permanently offset the stand in 3" increments. H) Are the pins for that height adjustment.
I) A concern brought up by many of you is the lash-up or binding of the four jacks working in concert. That will occur if the stand is NOT on the level when resting. With that much dead weight sitting on it, if one leg is short, then the entire stand will distort as the load is placed on it. That distortion GREATLY increases the lifting load by binding and increasing sliding friction. You can't see the distortion but its there.. Hence the little piece of steel under that foot on my looks-level-but-it's-not shop floor.
Here's an oblique close up of the drive mechanism. Note the added zerk fitting.
Here's looking down thru the top of the stand. You can see the VFD and the breaker.
OK crunch time. Time to test this thing before loading it up with a tank.
The only thing at hand was clay. Lots and lots of clay. 3,250 lbs of it. I brought it over on a forklift and set on the stand perfectly centered - which took a long time. Any bowing you can see in this picture is lens fiction. There is bowing but it is in no way visible from this point of view.
Here is what each box weighs. But that is net! There is actually more weight from the boxes and the pallet. It should be noted that THIS IS NOT A UNIFORM DISTRIBUTED LOAD. It is a point load. This makes all sorts of things worse. It makes the stand feet want to bow outward at the bottom. This increases binding and friction. It will cause the top to deflect much more than a distributed load would.
The test:
Raising the load was painful and potentially destructive. A wattmeter showed that the gear drive was drawing 1900 watts!! Keep in mind that this is a 250W gearmotor. I was astounded that that cheap TECO FM50 dished that out for minutes!!! The load crept up ever-so-slowly whining and making a frightful keening tortured sound.
After a while things sped up! Wow. WHOA!! I noticed the secondary gear was spinning on the shaft! This meant the right side was rising and the left side was not.
This was the solution. I welded the two gears together.
But this didn't help with the massive overloading being experienced by the gearmotor.
This test meant that the actual torque value needed to raise this structure far exceeded my original empirical jack test numbers. (The binding and the sliding.)
To find the new ACTUAL numbers I used that bad gear I made. I welded a large nut on it and installed it on the end of the motor shaft in front of the primary gear. (you can see it in the fourth picture up.)
I then took a deflecting bar torque wrench and turned the shaft lifting the clay. This gave me the actual torque needed. It was about 4 times my original number!!
I asked all over for solutions. No one had one. I stared at it for a few weeks before figuring one out..
