Great puzzle.
To be honest I did not see the stupidity.
I have no excuse, I did see it, but thought it was pretty clever. Actually it is all wrong, the transistors are mounted at the worst place, regardless of the high conductivity of aluminum.
Indeed it is not the best place to mount them. 
But I bet it works. Especially if the builder ensures that the heat sink can adequately dissipate the heat into the air.
Note that the function of the rather thick base on most heat sinks is to ensure that rapid changes in heat production by the attached device(s) can be absorbed and "buffered" before conducting to the fins and being dissipated. For devices that see spikes in heat production a lot (like CPUs, for example) a thick base (and one made of copper is even better) provides this necessary buffer.
This is far less important for devices that produce a steady, continuous amount of heat. As long as the heat sink can adequately dissipate the produced heat, all is well.
But I bet it works. Especially if the builder ensures that the heat sink can adequately dissipate the heat into the air.
Note that the function of the rather thick base on most heat sinks is to ensure that rapid changes in heat production by the attached device(s) can be absorbed and "buffered" before conducting to the fins and being dissipated. For devices that see spikes in heat production a lot (like CPUs, for example) a thick base (and one made of copper is even better) provides this necessary buffer.
This is far less important for devices that produce a steady, continuous amount of heat. As long as the heat sink can adequately dissipate the produced heat, all is well.
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The time constant from the dissipative junction to the copper package back is in the roughly 1 to 100 milliseconds. From package case to heatsink is roughly a second. To the dissipative surfaces, 10 seconds or longer. That heatsink won't work well if high power transients last more than 5 or 10 seconds.
Aluminum isn't as good as copper w/r to heat capacity, so heat does travel faster (higher diffusivity). But copper as you mention, is much better.
I saw mention of fan reliability. As an antique clock repair instructor, I shy away from bearing solutions, as they never last as long as bushings. I use brass or bronze, and after broaching to ID, use smoothing broaches.
At work, we have thousands of fans, and over the years (roughly 10), we are replacing many units because the bearings are seizing up.
We are now replacing some with bushings, and find in the literature that bushings that are oilite and well designed are supposed to be the ultra reliable ones. Apparently even with oilite bushings, it is possible to mess them up if you do the machining steps either out of order or incorrectly. I suspect (and hope) that Mr. Hoyt will chip in with some of his (intimidating to me) lubrication expertise
My gas fired house heat used bushings, but the previous owner's maintenance people did not oil them to schedule (I suspect never in 20 years), and it eventually made me cold.. I knew I was "peeved" when I popped the top off and found that the shipping tie wraps had never been removed from the fan motor brackets!!!
I replaced the motor with one that has sealed bearings... We'll see how many decades that lasts..
Jn
Aluminum isn't as good as copper w/r to heat capacity, so heat does travel faster (higher diffusivity). But copper as you mention, is much better.
I saw mention of fan reliability. As an antique clock repair instructor, I shy away from bearing solutions, as they never last as long as bushings. I use brass or bronze, and after broaching to ID, use smoothing broaches.
At work, we have thousands of fans, and over the years (roughly 10), we are replacing many units because the bearings are seizing up.
We are now replacing some with bushings, and find in the literature that bushings that are oilite and well designed are supposed to be the ultra reliable ones. Apparently even with oilite bushings, it is possible to mess them up if you do the machining steps either out of order or incorrectly. I suspect (and hope) that Mr. Hoyt will chip in with some of his (intimidating to me) lubrication expertise
My gas fired house heat used bushings, but the previous owner's maintenance people did not oil them to schedule (I suspect never in 20 years), and it eventually made me cold.. I knew I was "peeved" when I popped the top off and found that the shipping tie wraps had never been removed from the fan motor brackets!!!
I replaced the motor with one that has sealed bearings... We'll see how many decades that lasts..
Jn
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Hello,
Whatever you buy these days most products arent made with the intention to work properly for a nice lifespan. In the past you would know that spending a little more would give you a product that will be cheaper in the end because it will serve you for a lobnger time.
Now even the salesman will tell me that a 3500 $ TV wont last longer than a 2000 $ one. I tell him 3500$ is ok for a better image quality but it should come with a bigger lifespan. But he will just confess that he wants me to replace the 3500$ one every 5 years. My first colour TV cost me one month salary 4 decades ago and after 17 years the tuner inside stopped working. Now if i spend one month salary on a TV maybe it will work 5 years but probably it wont. I told the salesman i will pay 300$ if it will work 10 years without repair. Theoretically with LED technology it would be easy to do. BUT they dont wanna make one like that.
Greetings, Eduard
Whatever you buy these days most products arent made with the intention to work properly for a nice lifespan. In the past you would know that spending a little more would give you a product that will be cheaper in the end because it will serve you for a lobnger time.
Now even the salesman will tell me that a 3500 $ TV wont last longer than a 2000 $ one. I tell him 3500$ is ok for a better image quality but it should come with a bigger lifespan. But he will just confess that he wants me to replace the 3500$ one every 5 years. My first colour TV cost me one month salary 4 decades ago and after 17 years the tuner inside stopped working. Now if i spend one month salary on a TV maybe it will work 5 years but probably it wont. I told the salesman i will pay 300$ if it will work 10 years without repair. Theoretically with LED technology it would be easy to do. BUT they dont wanna make one like that.
Greetings, Eduard
I've only ever bought one TV, I still have it, it's my only TV, I watch it occasionally, I like to see democracy at work lately.
PS ESP - Heatsink design and transistor mounting
PS ESP - Heatsink design and transistor mounting
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The story is the same for many things.
The rule of thumb (in North America, anyway) now for any major appliance is "6 years, you're lucky". Doesn't matter if you spend $400 or $1500 on that new dishwasher or washing machine. 6 years is all you can expect.
Then it all goes to the landfill.
I bet if you just slid the transistors up a bit, so as to get their HS contact pad a bit more centered with the thick edge, rather than further down along the outside fin...
I wonder what it'd look like under the Flir thermal camera, oriented horizontally, as each side dissipated 25W in still air? That's the measurement which would tell the story truthfully.
A FLIR ONE Gen 3 is <$200, for all we know the designer has one (hobbiest affordable) and checked it out -
I wonder what it'd look like under the Flir thermal camera, oriented horizontally, as each side dissipated 25W in still air? That's the measurement which would tell the story truthfully.
A FLIR ONE Gen 3 is <$200, for all we know the designer has one (hobbiest affordable) and checked it out -
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Hello,
Generalizing is ok for products is my opinion.
England, the country which gave us Sturmey- Archer the ones that could be repaired. I had bicycles which served me twice the length of the equator with S.A 3 speed gear. Now you will get 7 speed "" gearbox ". That will break down pretty soon. The 18 year old who just started working in the bicycle shop is told just to replace the complete gear because he probably cant repair it in an hour.
One needs to generalize to make things easy.
Irish people have red hair, always drunk and are pro life. English tourist always drunk too, their food is horrible but there are many great English writers, their pop music used to be good but for good classical music you need to go the continent.
Greetings,Eduard
IMHO, there' none greater than the revered Dr. Amar Gopal Bose, of MIT fame.
After realizing in a classical concert hall, the audience hears mostly reflected sound, the holy man went on to design the famed 901 which recreated 10% direct and 90% reflected sound in your living room.
Assuming you had a properly miked recording, already capturing the ambiance sound, can somebody please help me with the math of the combination? Is 810% reflected sound close enough?
After realizing in a classical concert hall, the audience hears mostly reflected sound, the holy man went on to design the famed 901 which recreated 10% direct and 90% reflected sound in your living room.
Assuming you had a properly miked recording, already capturing the ambiance sound, can somebody please help me with the math of the combination? Is 810% reflected sound close enough?
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