jamesp
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Post by jamesp on Aug 4, 2020 6:20:09 GMT -5
Most vibes operate at about 3000 - 3450 vibrations per minute because AC motors don't normally operate at speeds above 3450 rpm. I found this 2900 to 5800 rpm DC motor on EBAY for $14. It has dual shaft outputs like the Lot-O motor and large ball bearings to handle counterbalance forces. Looks like an easy retrofit between the existing Lot-O structure with some large washers and M4 4mm bolts. Intent will be to increase vibration frequency but reduce vibration travel by using counterbalances closer to the motor shaft. Shorter vibration travel should reduce forces on springs and impacts on rocks. A small 110VAC to 12-24 VDC converter will be required. Preferably adjustable from 12 to 24 volts to have 2900 to 5800 rpm. Motor is 30 watts, close to the power usage of the stock Lot-O motor. Power usage should increase a bit due to the converter. The shafts are only 6mm as opposed to the 6.35mm(guessing) Lot-O motor so the stock counterweights will not fit. No problem, smaller diameter home made counterweights will be used for reduced amplitude. No mention of motor being continuos duty. It does have ball bearings and is a permanent magnet motor so it should run cool. Looks like a drill press alone will handle the retrofit. Step 1: Find 2 large washers to clad both ends of the new motor and drill relief holes for the motor end cap screw heads. Since the motor is about 3/16" shorter than the stock motor and smaller in diameter by what looks like an inch the large washers should mimic the new motor size to the stock motor size for an easy fit into the motor mount. And drill holes for the 4mm screws that bolt the washer to the new motor. Plenty of drilling. Shear luck finding this DC motor with 2 output shafts and and adjustable to doubled rpm. No way. End flange showing encapsulated ball bearing and 4mm mounting holes. Specifications
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jamesp
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Post by jamesp on Aug 4, 2020 6:51:38 GMT -5
Ultrasonic vibration is way up there. 20,000 vibrations per second. Inaudible... The stock Lot-o probably vibrates at 3000rpm/60 seconds = 50 vibrations per second. This modified machine should do near double that. 5800rpm/60 seconds = 97 vibrations per second. But, going with shorter less destructive vibrations by making counterweight lighter and/or closer to motor shaft. Goal is to hasten tumbling steps but reduce vibration travel for a more gentle tumble. Luck was on my side. Don't tell but I have 100's of pounds of washers collected from scrap steel resale centers. I believe these are actually shower flanges for the bath shower head. Anyway, this motor is now close to the exact size of the stock motor for hopefully an easy bolt in. Holes must be drilled in the washers to match the Lot-O mounting holes.
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Post by HankRocks on Aug 4, 2020 7:07:50 GMT -5
Luck was on my side. Don't tell but I have 100's of pounds of washers collected from scrap steel resale centers. I believe these are actually shower flanges for the bath shower head. Of course you had 100's of pounds of washers collected!!! I would have been disappointed if you didn't!!
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jamesp
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Post by jamesp on Aug 4, 2020 8:13:52 GMT -5
Luck was on my side. Don't tell but I have 100's of pounds of washers collected from scrap steel resale centers. I believe these are actually shower flanges for the bath shower head. Of course you had 100's of pounds of washers collected!!! I would have been disappointed if you didn't!! Gotta have washers. Handy for dozens of situations. Welder's delight.
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Post by orrum on Aug 4, 2020 9:18:33 GMT -5
LOL. Washers by the ton? Of course. Watching this one Jimm, veryyyy interesting project.
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jamesp
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Post by jamesp on Aug 4, 2020 11:06:00 GMT -5
LOL. Washers by the ton? Of course. Watching this one Jimm, veryyyy interesting project. why not try a bit of hot rodding Bill. It works for you moonshiners .
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Post by knave on Aug 4, 2020 11:16:05 GMT -5
I’m gonna go home and plug my loto into this.
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Post by aDave on Aug 4, 2020 12:50:55 GMT -5
This will be VERY interesting to see. I can't wait. (Note to self: Contact jamesp if I ever need a washer.)
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jamesp
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Post by jamesp on Aug 4, 2020 18:16:52 GMT -5
I’m gonna go home and plug my loto into this. So you get 110 x 1.15 = 126.5 VAC. Should increase rpm 15%. Might want to remove a bit off each counterweight knave.
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jamesp
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Post by jamesp on Aug 4, 2020 18:20:09 GMT -5
This will be VERY interesting to see. I can't wait. (Note to self: Contact jamesp if I ever need a washer.) 3000-3450 is a practical limitation for mass production using AC motors Dave. Let's see if a hobbyist can jazz things up a bit with some personalized mods.
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Post by knave on Aug 4, 2020 18:36:12 GMT -5
The stock Lot-o probably vibrates at 3000rpm/60 seconds = 50 vibrations per second. Wanna bet if the 50 vibrations per second has a relationship to 60 hz?
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Post by knave on Aug 4, 2020 18:38:30 GMT -5
My LOTO errs on the side of gentleness. For rough grind I could speed it up methinks. And my L1 here is 123 or so. 123 x 1.15 = 138 or so.
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jamesp
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Post by jamesp on Aug 5, 2020 6:06:30 GMT -5
The stock Lot-o probably vibrates at 3000rpm/60 seconds = 50 vibrations per second. Wanna bet if the 50 vibrations per second has a relationship to 60 hz? knave knows motors. I do know the rpm of an AC motor is directly rated to the 60hz alternating current. For some reason (is it the phase shift ??) they do not rotate in synch with the AC frequency(3600 is rotating like 3450 and 1800 is rotating like 1725). I think it has to do with developing torque. Not sure where the 150 rpm goes for a 3600rpm(3600-150=3450) and the 75rpm goes for the 1800rpm(1800-75=1725). I have never seen a 7200-300=6900rpm AC motor. Like Europe use 50Hz and things rotate 100% x (1 - 50/60) = 13.3% slower. Why do they make a step up transformer that increases AC voltage 15% ? I understand it makes your 123VAC raise to 1.15 x 123 = 138VAC. It should be a small enough increase to not damage the AC Lot-O motor.
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jamesp
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Post by jamesp on Aug 5, 2020 6:29:01 GMT -5
I did find a variable DC voltage supply. I believe it is adjustable from 0 to 30 VDC. It would not surprise if the EBAY DC motor could go past it's rated 24VDC(5800 rpm) to 30VDC(calculated 7250 rpm). Most permanent magnet DC motors can run off of higher voltage with no ill effects. Just check for overheating. I hope I specified the 0 to 30VDC DC power supply correctly: it has a 110VAC input. Sounds simple.
Both the Lot-O motor and the 30 watt EBAY DC motor are close to 30 watts(.746 x 30 watts) = like 1/22 horsepower. I believe the stock Lot-O motor is 1/20 horsepower. Amazing the the little $14 EBAY twin shaft DC motor is so similar to the Lot-O motor in so many ways. I ordered 2 of them at that price.
I think a square plate could be used for the mechanical adaptor instead of a washer. It just so happened the washer already had a ~1 inch hole in it to fit over the ball bearing shroud at the end plates of the motor. Drilling an accurate 1 inch hole in metal is beyond the realm of my tools. Not necessary to be accurate though, a square hole could work.
Specifications for DC power supply: The TekPower TP3005N is a professional DC regulated power supply from TekPower. This is a highly stable, high quality switching power supply with its output continuously adjustable at 0-30V DC and 0-5A. The unit comes with a large LED displays, providing accurate readout for the voltage and current values. The cooling air fan will automatically start when the heat accumulated inside the enclosure.
Specifications for DC power supply. No way I will be pulling 5 amps at 30vdc or 4.2 amps at 24vdc or 2.1 amps at 12vdc. I think it can be adjusted to 5 amps at 12vdc being that both amps and voltage is adjustable. Small at 9"x6"x3".
Output DC Voltage: 0.0 - 30.0V Output DC Current: 0.00 - 5.00 A Input Voltage: 110V/AC, 60Hz Voltage and Current adjustment Operating Temperature: 0 - 102 F (0 - 40 C), Relative Humidity: < 80% Size: 9 x 6.5 x 3.3 inches Weight: approx. 7 lbs
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jamesp
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Post by jamesp on Aug 5, 2020 6:44:31 GMT -5
$60 ppd on EBAY. Been needing on of these. Dad and I had one for tuning 12vdc slot car motors.
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jamesp
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Post by jamesp on Aug 5, 2020 7:10:43 GMT -5
In case anyone is curious. These are slot car dc motors. They run fast at 50,000+rpm. Much faster than that and the armature wires have to be coated with epoxy to prevent the centrifugal force from slinging the wrapped wires off. The more expensive ones do over 100,000 rpm. The hobbyist would pump up to 60vdc into one rated at 12vdc to increase speed for short run scale dragsters. Often resulting in melted copper explosions lol.
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Post by knave on Aug 5, 2020 11:49:01 GMT -5
The step up transformer is for areas with low voltage, to increase voltage on power sensitive equipment. Available for $8 from surplus center because it’s advantageous to the power companies to be over voltage, they can deliver more kw with a given wire that way.
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Post by knave on Aug 5, 2020 11:51:23 GMT -5
A 7k rpm AC motor would have to be 1 pole. Apparently motor poles exist in pairs, so the minimum number is 2.
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jamesp
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Post by jamesp on Aug 5, 2020 16:15:21 GMT -5
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jamesp
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Post by jamesp on Aug 10, 2020 5:34:09 GMT -5
Received adjustable DC power supply. Both amperage and voltage is adjustable. It also displays both voltage and amperage in real time. Looks to be a fine power supply.
Calculated/specified rpm's and real time no-load amp draw from motor as follows:
12 volts - .13 amps - 2900rpm(stock Lot-O speed) 18 volts - .19 amps - 4350rpm 24 volts - .25 amps - 5800rpm 30 volts - .29 amps - 7250rpm
Being a permanent magnet DC motor it is no surprise it has gobs of torque from 6 volts to 30 volts. Smooth and quiet, video camera is sound sensitive. At 24vdc/5800rpm it heats up more than desired even at no-load and could be a problem. At 18vdc/4350rpm it stays cool. No specifications were provided about the duty ratings but motor label says 12 vdc. EBAY seller mentions 12 to 24vdc rating. hmmm. Even 18vdc at 4350rpm would be a substantial speed increase over stock unit.
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