Incubator Mk III

29 11 2013

Having dispatched all the eggs  from incubator MkII, I set about reconfiguring the whole affair to make it more energy efficient, and available to more eggs in one hit.  Over the past month as I eagerly awaited the birth of our ducklings, I put a lot of thought into how I could improve it.

The first thing I decided to do was improve the insulation, so I cut up another polystyrene box and inserted new walls on the inside.  This also decreased the volume of air to heat, but also decreased the floor area for eggs.  Can’t have everything I guess….  To improve the top, I simply used two lids, and did away with the glass window altogether.  The hatching process is so slow, you hardly need a window to see what’s going on!  I tried using glue between the two lids only to discover it dissolved the polystyrene, but it doesn’t need it anyway, the lamp batten holds it all together.

Halogen light bulb

The next thing I decided was that having the light at one end and the eggs at the other wasn’t so clever (so much for copying youtube makers of incubators – I can show them a trick or two now…!)  As an aside, I had already replaced the original incandescent bulb after it blew within two weeks, something I had sort of predicted would happen due to the frequent cycling it was subjected to in the MkI version.  The bulb in service now has a halogen lamp inside the glass bulb, which they reckon makes 40W of light with only 28W of electricity.  It works.  They have a two year warranty, so if they blow early because of how I’m using them…..  I’ll test the waters!

IMG_0542

Rewired in the double lid

Because the heat received from the bulb is proportional to the square of the distance from the bulb, any eggs half the distance from the lamp as compared to those furthest away actually cop four times the heat, potentially either cooking the close ones, or underdoing the far ones.  So I moved the bulb to the middle of the lid.  That meant the control unit also had to be in the lid, needing just a quick rewire……  which caused me to spectacularly blow the lamp and trip the circuit breaker and safety switch!  The connectors on the back of the control unit are very close together, and I hadn’t pushed the active wires in far enough before tightening up the screws, and they must’ve touched the neutral wires, causing a dead short.  Ah well…. at least I proved all the safety devices in the meter box work!  And no one got hurt.  Second time around I used my multimeter to make sure it wouldn’t happen again.  Once bitten and all that…….

IMG_0544IMG_0543Now that the bulb is in the middle of the box, the water bottle I had put there for thermal mass could not stay there, so I replaced it with four 700mL glass bottles, and placed one in each corner, equidistant from the bulb, with no lids, allowing for evaporation to maintain humidity levels.  Doing it this way means I actually have a fair bit more control, because I can now adjust humidity by adding/removing lids to suit……

With sawdust in the bottom of the box instead of hay, I made a slight hollow in the middle such that the eggs at the bottom in the middle are closer to being the same distance from the lamp as the eggs that are at the far ends.

This new configuration allows for some twenty eggs to be in the box (twice as many as last time), and all things being equal and assuming that roughly the same proportion of eggs are fertile, we should have another six ducklings for Christmas.

Once the temperature of all the box’s contents had settled down, I timed the cycling of the lamp, and was utterly gobsmacked at the improvement.  The MkII box took around one minute to reheat from 37.3°C to 37.6°C, but the MkIII version does it in…… NINE SECONDS!  In fact, so much thermal momentum is built into the system now, that after the lamp goes off at 37.6°C, it actually momentarily builds up to 37.8°C before cooling back down to 37.3°C in about two minutes and forty seconds.  The new incubator should therefore use less than 20% of the energy the last one did.

ducklings2

Very cute…… AND delicious!

The newbies are now out on the front lawn in their protective cage, enjoying the 36°C scorching the BOM have forecast for today….. boy am I glad I don’t live in an incubator!  They’re eating and crapping just fine, and should make a nice dinner in three or four months time………