Adding Convection

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Orngrimm
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Re: Adding Convection

Post by Orngrimm »

Downunder35m wrote: Mon Oct 26, 2020 11:50 pm We seem to forget that a gas oven creates convection naturally anyway ;)
seattleuserfriendly wrote: Sat Oct 24, 2020 3:21 am It would seem to me that there might be an easy way to add convection to an existing electric oven.
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Re: Adding Convection

Post by seattleuserfriendly »

This reminds me of an old joke. A man is flying in a hot air balloon when he realizes he is lost. He reduces his altitude and spots a man in a field below. He lowers the balloon toward the man and shouts to him, “Excuse me, can you help me? I am late to meet a friend, but I don’t know where I am.”

The man below says, “I’m happy to help. You are in a hot air balloon, hovering approximately 30 feet above this field. You are between 40 and 42 degrees N. latitude, and between 58 and 60 degrees W. longitude.”

After a brief pause, the balloonist declares: “You must be a lawyer.”

“I am” replies the man. “How did you know?”

“Well,” says the balloonist, “everything you have told me I am sure is technically correct, but I have no idea what to make of your information, and the fact is I am still lost.”

I'm looking for a simple solution where a fan can be placed in an electric oven without drilling. I'm sure there is a way that it can be placed on the floor or shelf with current coming from the outside without drilling. But if that's impossible, just let me know. The details and the debates may be a way engineers communicate, but I'm looking for a simple answer.

There are a lot of answers here. I wish one addressed the question as placed. Information dumps, responding to more convenient questions, tangents do show people that you are intelligent. They just aren't really helpful.
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Orngrimm
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Re: Adding Convection

Post by Orngrimm »

The problem is that a motor and for that case also electronics and a LOT of plastics dont fare well in 200+°C environment.
So just placing a fan with a cable attached to an outside source is feasable up to like 70°C. No more for sure!It is simple physics: Everything you want to operate inside an oven has to withstand the temperature within said oven.
Cables need to be silicone or even PTFE, Plastics need to be Thermoset and not Thermoplast, Electronics need to be designed to withstand those hellish temps (Say goodbye to all electrolytic caps, Almost all chips will fail quite fast in this temperature), Bearings need to be designed to work with the thermal expansion expected, and so on and on... Physics.

But i gave you an option which would work without drilling and no melting. See viewtopic.php?p=358#p358

I converted my oven once temporarely to convection to dry my biltong at 50°C. I just placed a computer-fan in there and fed the 2 small wires thru the door-sealing to my PSU outside. But anything higher than 50° i wouldt really dare. Even the 50°C was higher then the spec of this fan (40°C ambient)

So to give an answer to your previous post: I gave you a perfectly viable answer as well as Jack at viewtopic.php?p=315#p315
If you dont even read those suggestions which would WORK then we cannot help you any further, sorry. But as we gave you the same idea and input multiple times, showed you the shortcomings of other solutions, yet you still dont see the options given to you in plain sight, it is a bit strange to indirectly tell us we only give you useless (yet correct) answers. We gave you solutions. Use them.
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Re: Adding Convection

Post by Emilly »

I love making cakes in the oven from time to time. However, it's not too hard to create a motor that would survive the oven temps but keeping it spinning at low noise levels will be a problem!
Last edited by Emilly on Sun Nov 20, 2022 3:49 pm, edited 1 time in total.
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Re: Adding Convection

Post by Orngrimm »

welcome, Emily! :)
Now, you tell it like this, i think one could make a magnetic coupled fan thru the glass door...
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Re: Adding Convection

Post by Downunder35m »

I had a look at my old (gas) oven and at the tiny electric one that is rotting in my garage.
Both come with the same problem: A lack of space inside to put a fan WITH an attached motor.
In terms of adding an EXTERNAL motor with a fan inside without drilling holes I could not find a solution either.

Having said that, I think what Orngrimm said might actually be feasable - just.
But only on this old gas oven as most modern ovens come with a double glass door, making it rather complex to get a magnetic connection.

Apart from using a steam engine to power the fan I think the options ARE limited here.
The really only option I was able to see as half worth checking would be where the light is mounted.
This is usually covered by a glass while the actual light is OUTSIDE the chamber.
If you could do without the light:
Aluminium exhaust ducts as used for these in-line Diesel car heaters could be coupled with an external fan.
Preferably though something even thinner in diameter - so you can fit two of these pipes through the light opening.
Inlet pipe is routed to the top into a corner, bottom one, well, low down....
For the fan you would ideally use something with a longer shaft (to keep the heat away from the motor) and an enclosed housing for the fan, all metal of course.
But maybe we are still thinking in the wrong direction....
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