Any advice for egg turner motor?

[gpop1]

Hi gpop1

As I haven't bought the 0,6rpm motor yet, I will certainly take your advice. I presume the furtherest from the centre the motor is the less strain it will take and hence last longer. One of the challenges in building this unit is that it will be a long way away, so I am really going for tried and tested (and was thinking that I would build redundancy into it for stuff that fails). If it was here with me, I'd be testing how cheaply and efficiently I could build it, but I like tinkering. I had even thought that all I needed was a tiny aquarium pump, and two big tanks suspended from each side of the trays, and that by simply pumping water from one side to the other , the trays would tilt.

So on a 300mm shelf (12") a 40 degree either side tilt moves the shelf edges through 193mm (7,6") a 150 (6") travel will be 117mm from the centre, while the 100mm (4") is close to halfway at 78mm(3"). In this situation 6" (150mm) actuator, makes sense, unless I was to use wider than 12" shelves. The load on the actuator will be light, unless the eggs are really badly packed. I see a 150mm actuator is rated for 500Newtons so it should lift a mass of 50kg or 110 pounds (about 720 Jumbo eggs or 1000 medium eggs). so even if I went for 24" deep shelves it can handle it. I looked at the 0,6rpm motor, it has a torque of 25kg/cm so at our 78mm arm (ie 100mm travel) it can lift a mass of 320 grams (or 5 eggs ) If my calculation is right.

I had been wondering what the best way to heat it is.. I presume you are suggesting 100w Peltiers? What are the advantages of the Peltiers over the alternatives?

I once ran my home built telescope with a tiny motor, it always amazed me how such a small stepper could move something so big.

The real challenge is knowing whats easy for a motor, as thats really the sweet spot. How does one handle jams.. can it be programmed to stop or reverse if it hits an obstacle ? or does it just stop without damage?

I have kept chickens for about 8 years now, but have relied on skilful hens to hatch the necessary offspring, I am hoping this incubator can create a successful business. I am in South Africa, but this incubator is going to do service in a rural area in Malawi.

I could never work out the torque of the 0.6rpm motor as its listed as kg-cm. I know from personal experience that it can tear a aluminum 6mm flex coupler in half if you jam the tilt table.

I wouldn't see a problem turning 50-100 eggs with the 0.6 motor but when you start looking at 150 and more then you may need a larger motor. The trouble with tilt tables is that you need a motor that will not free wheel when it stops. Also how do you plan to hatch unless the turners can be removed?

In 12vdc you are limited to a few types of heaters. The ptc is the cheapest and you can get a 250w that can be unwired so you end up with 3 @ 83w that can be controlled independently. I like the peltier but it has its draw backs especially due to the aluminum heat sink which can make temperature control difficult. I do like the fact that the peltier can be reversed and the temperature can be brought down inside the incubator. Ive no idea if that would be a useful option. In a hot country when the incubator is not kept inside a climate controlled home I could see it being useful. My incubator about 14"x 24"x 18" internal uses one 72w peltier and that is constantly adjusting between 9 to 100% power (haven't ever bothered to work out the average power usage over 24hrs but it probably averages around 35w).

 

[PaulM2]

Hi gpop1

Here is a good conversion http://www.convert-me.com/en/convert/torque/?u=kgfcm&v=25

I looked at the torque of the 0,6rpm motor and realised I had missed a zero out somewhere. The force of 25kg/cm, means that at one centimeter a force of 25kg is needed to stop the motor. In analysing the weight it can take I am presuming we take the centre of the tilt so at 7,5cm (3 ") the weight there will be 25/7,5 = 3,3 kg ( 7, 25 pounds). or in our jumbo egg scale , 50 eggs or more usually 67 eggs. Again in balanced trays the trays are balanced so one is only moving the inertia, so this motor may be good enough.

I was thinking about the motors that lift garage doors.. often they are supported by springs and weights so that they are really only overcoming the inertia of the door. However the tilt design is a balanced design so I don't see any way to reduce the load on a motor.
Perhaps a dc motor with a pawl and ratchet might be the answer, as the motor is only required to run in one direction.

Do you know anything on the reliability of the heating elements. I presume its fairly common to have disastrous side effects of a heating element failure. Do you use the peltier reversal to precipitate extra humidity out when needed?

The climate where the incubator is being installed looks very favourable as it doesn't have major swings in temperature.

 

[gpop1]

Hi gpop1

Here is a good conversion http://www.convert-me.com/en/convert/torque/?u=kgfcm&v=25

I looked at the torque of the 0,6rpm motor and realised I had missed a zero out somewhere. The force of 25kg/cm, means that at one centimeter a force of 25kg is needed to stop the motor. In analysing the weight it can take I am presuming we take the centre of the tilt so at 7,5cm (3 ") the weight there will be 25/7,5 = 3,3 kg ( 7, 25 pounds). or in our jumbo egg scale , 50 eggs or more usually 67 eggs. Again in balanced trays the trays are balanced so one is only moving the inertia, so this motor may be good enough.

I was thinking about the motors that lift garage doors.. often they are supported by springs and weights so that they are really only overcoming the inertia of the door. However the tilt design is a balanced design so I don't see any way to reduce the load on a motor.
Perhaps a dc motor with a pawl and ratchet might be the answer, as the motor is only required to run in one direction.

Do you know anything on the reliability of the heating elements. I presume its fairly common to have disastrous side effects of a heating element failure. Do you use the peltier reversal to precipitate extra humidity out when needed?

The climate where the incubator is being installed looks very favourable as it doesn't have major swings in temperature.

I don't reverse the peltier as I keep the incubator in a air conditioned home but I had a plan to keep the incubator in the workshop and during the day the temp will exceed 110 degrees so ive always planned this as a option. The peltier is rated at 10,000 hours but ive had 2 burn out (one was my fault as I didn't use heat sink paste) and the other was original so it may have been 3-4 years old already.
Another thing I liked about the peltier is it could be controlled with pwm (pulse width modulation) so I could allow the arduino to control the power level from 0-100% instead of off and on. As with any type of heater when it fails it can be bad news. If the incubator was trying to reduce the temperature then it would be a complete wipe as eggs can be chilled for a long period where over heating above 104 is normally fatal.

With out doing a little r&d I can not tell you what will work best. Ptc is the cheapest and easiest but ive had rotten luck using them so im slightly biased.

 

[PaulM2]

Thanks again, very interesting, I will do a bit more finding out. Id like something with 100 000 hours as that will last a long time. I built my own windturbine so know the advantage of overdesign. What hassles have you had with ptc.

I was looking at the table pivots, and will either put self lubricating bushes or a small bearing in. I know its overkill, but I think if its tilts easily it will be a lot easier on the motor, as well as less likely to jam.

I am thinking to have dual systems where possible and considering possibly redundancy. I like the concept of a wafer thermostat as it seems very robust and sufficiently accurate. finer adjustment could then be done digitally with two independant systems

 

[PaulM2]

I have been thinking about motor sizes, and thought I should try some calculations, despite my physics being very rusty. I think with a good bearing at the pivot, the effort to move the mass will be very small. So all one has to account for is the loading of the one side of the tray and not the other. I have attached a sketch in mm (25mm equals 1") showing a three tiered egg tray

I then calculated the torque of the situation where one side is loaded and the other is not, if the motor has greater torque then it will move the mass and not burn itself out trying.

Case 1. A single 60 egg tray Total 30 eggs

Distance Mass eggs in row Torque
1st egg 2,5 0,07 5 0,875
2nd egg 7,5 0,07 5 2,625
3rd egg 12,5 0,07 5 4,375

Total torque 7,875 cm/kg

Case 2. A 3 layer 30 egg tray .Total 90 eggs
Torque
1 layer 7,875
2 layer 7,875
3 layer 7,875

Total torque 23,625 cm/kg

Case 3. A single layer 60 egg tray Total 60 eggs

Distance Mass eggs in row Torque
1st egg 2,5 0,07 10 1,75
2nd egg 7,5 0,07 10 5,25
3rd egg 12,5 0,07 10 8,75

Total torque 15,75 cm/kg

Case 4 A triple layer 60 egg tray Total 180 eggs
Torque
1 layer 15,75
2 layer 15,75
3 layer 15,75

Total torque 47,25 cm/kg

Case 5. A single layer 120 egg tray Total 120 eggs

Distance Mass eggs in row Torque
1st egg 2,5 0,07 20 3,5
2nd egg 7,5 0,07 20 10,5
3rd egg 12,5 0,07 20 17,5

Total torque 31,5 cm/kg

Case 6 A triple layer 120 egg tray Total 360 eggs
Torque
1 layer 31,5
2 layer 31,5
3 layer 31,5

Total torque 94,5 cm/kg

Case 7. A single layer 120 egg Tray Total 120 Eggs

Distance Mass eggs in row Torque
1st egg 2,5 0,07 10 1,75
2nd egg 7,5 0,07 10 5,25
3rd egg 12,5 0,07 10 8,75
4th egg 17,5 0,07 10 12,25
5th egg 22,5 0,07 10 15,75
6th egg 27,5 0,07 10 19,25

Total torque 63 cm/kg

Case 8. Triple layer 120 eggs Total 360 eggs
Torque
1 layer 63
2 layer 63
3 layer 63

Total torque 189 cm/kg
So the worn gear motor which has a torque of 20kg/cm can cope with only with case 1, 2 and 3 safely but would need a 1:5 gear to drive Case 6,
I wondered if a chain and two bicycle gears might be the answer, as this would still be cheaper than a linear actuator. Case 7 and 8 show how its better to keep the incubator trays thinner as its easier to move as in case 5 and 6.

I am trying to save on the big jump in price 8 times) to a Linear Actuator, I wonder if they use bigger motors or just more gears.

I calculate if I use a linear actuator of 150mm travel in case 6 it will be required to overcome a force of 80N. The linear actuators on ebay have 500N ratings, so are 7 times the worst case scenario. I think 2x is more reasonable.

 

[gpop1]

May be a different motor like a electric window motor could work but its hard to find the rpm on these.

 

[PaulM2]

Yes gpop1 , I find the info on ebay very basic, and not clear. Here are some options in each division..

12 volt Motors
Cost Torque Amps Link
0,6 rpm worm gear motor US$ 11 25 kg.cm 0.1 http://www.ebay.com/itm/DC-12V-0-6R...444591?hash=item2356763c2f:g:h0gAAOSwARZXl4Ew
3 rpm worm gear motor US$ 43 92kg.cm 0.46 http://www.ebay.com/itm/3-RPM-Elect...69ac5d0&pid=100033&rk=3&rkt=8&sd=282035559456
150mm linear actuator US$ 44 500N 3.0 http://www.ebay.com/itm/DC12-24V-20...hash=item2119f4701c:m:m8A2_v8uRxAVA0Rha7qdLZA
25 rpm geared motor US$ 11 2.33kg.cm 1.0 http://www.ebay.com/itm/High-Torque...380766?hash=item258f71a95e:g:ebQAAOSw5cNYgZTC
3rpm motor US$ 20 3.0 http://http://www.ebay.com/itm/3RPM...951002?hash=item4d380e6bda:g:ZZ0AAOSwCU1YuJAL


The last two have the drawback of not holding the tray! so practically are less suited to the application. One can easily fabricate an actuator with some 6mm threaded rod and a nut. I wonder if this would be self locking?

I see the linear actuator has a speed of 20mm second so will take 7 seconds to tilt the trays. I am presuming this is satisfactorily.

I looked at electric window motors but they are more expensive! (and I guess I have an aversion to electric windows)

 

[gpop1]

I don't see a problem turning the trays in 7 seconds.

You can fabricate your own actuator or use any lever type assembly with a screw drive as it would be self locking. Basic leverage means you can increased torque by sacrificing speed.

Or you could look at ball screws which would probably be more reliable than a threaded rod and a nut