Are these temperatures viable?

[Altairsky]

This is a continuation of my old thread about fixing an old incubator.
https://www.backyardchickens.com/threads/help-fixing-an-old-incubator.1616174/#post-27640089
Sadly all the eggs died (last chick died during lockdown).
Now that the incubator is empty I could add a computer fan. I actually had to put it at 6 volts to get a decent air circulation though the temperatures are still different from area to area but I think they might be viable. Do you think I can try again or should I put the fan somewhere else? Any suggestion? Below I added a couple of pictures to show the previous and the current temperatures, and the fan placement. Any advice would be much appreciated! I really don't want to kill more chicks!

 

[Debbie292d]

@BantyChooks builds lots of incubators and maybe she can help you.

 

[BantyChooks]

Wow, fantastic diagrams and testing! Thanks for explaining the problem so well.
How many eggs do you want to put in there? The temperature distribution will most likely change somewhat after you put eggs in, given how small the incubator is. I like to put in infertile or fake eggs and then re-evaluate temperature after ~12 hours. I’d avoid the corners where the temperature seems uneven, and instead set just a few eggs at a time. Overall, I would say your temperature now is safe to incubate within as long as your thermometers have been calibrated. Nice job.

 

[Altairsky]

Hi! Thank you for the answer! I'm planning to only hatch 12 eggs at a time which is half the capacity of this incubator. I should be able to only use the space within the more stable area and move the egg turning grid within the stable area.
The analog thermometer is calibrated, the digital ones are coherent to the analog thermometer and with an error of +- 0.1°C
I'll let you know how it goes on my next incubation!

 

[Altairsky]

Just updating on my "fixed" incubator: on day 13, 9 eggs out of 10 are alive! Only one egg died on 3rd day but it was an odd and very small legbar egg so I knew it might be not viable so definitely not the incubator fault. There is another egg that has a cracked shell and I'm not sure if it will hatch. So far so good, but it has a larger airsac compared to the others so it might be slowly dehydrating.

 

[Altairsky]

60% hatch rate, most chicks were malpositioned and pipped on the side of the egg, 2 of them died in the shell because they couldn't find the air cell. Need to find out what happened and see if I can improve the hatch rate.
Temperature might have been too high because I had the first pip at day 18. At day 20 the last chick hatched. On day 21 I did the necropsies.