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#1 2015-11-06 17:13:46

jt
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From: Bermuda Triangle, NC USA
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TwiggyBoxGambit: Compact Convection Correction . . . Take II

I found a couple of inexpensive IR Heat Sensors online after I saw one on sale for $20 recently, so it's time to revisit an old hacks thread with missing pics: TwiggyBoxGambit

Also found a more succinct explanation of the concept that I posted here:

On the Subject of Classic Cooling: The only passive cooling mod for inside the case of the compacts that looked workable at all to me was a paper or plastic gasket mounted to the chassis underneath the drive cage that came with some of the Killy-Klip Radius upgrade cards. It appears to have partially mimicked (footprint only) the Twiggy drive's metal enclosure. That sheet metal box appears to me to have been a key component in the Power/Cooling budget of the seminal Mac with its ludicrous spec for passive cooling. IIRC the designer of the Twiggy/512k original Mac made the move to Radius with the other founding members.

When Apple dumbed it down to 128k and switched to the Sony drive with its smaller footprint and sheet metal cage, the cooling budget went right out the window. The revised design (miserable cost savings inspired kluge) failed to channel the side vent airflow across the bottom of the chassis and straight up the side of the built in MacChimney created by the side of the TwiggyBox and right across the hottest components of the A/B.

A couple of months later, I hacked (literally) a clear-sided Visible Plus case in the now picture-deprived ZipMacPLUS™ thread. The original parts are in an organized box, so I pulled out the case and used duct tape to implement a flip up lid. This way I can take controlled condition readings of the main transformer at stabilized operating temperature with and without the ersatz TwiggyBox installed.

Now, the question is: what's the approximate operating temp of the transformer? The inexpensive heat loss guns I've found have a max temp range somewhere between 428 and 716 degrees F.

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#2 2015-11-06 18:03:11

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I am still 100% sure the reason the Twiggy drive had that metal box over the top of it was to protect it from RFI (and possibly magnetic flux) generated by the TV yoke right over its head. (As I noted at the time the same sort of metal boxes can be found in all manner of old computers in which floppy drives are mounted in the same case as a monitor; if necessary I could spend hours googling up photos of old computer guts to support the case with.) Maybe the presence of a blocking chunk of something there might accidentally improve the thermal characteristics of the case, but I also 100% guarantee it wasn't designed that way. (As I recall, the ventilation slots that this would supposedly divert airflow to didn't even exist until very late in the design of the case bucket, when it became clear that S.J.'s desire for the top of the box to be completely solid and sealed just wasn't going to work.)

Also, regarding the idea that any plastic/paper "gaskets" included with upgrade boards were put there to "replicate" the Twiggy bucket to improve cooling: just a guess, but it would seem to me just as if not more likely the upgrade makers would include those so there would be some insulation in case the piggyback board were to come partially loose and touch the metal chassis right above their head. *ZAP*.


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#3 2015-11-06 19:10:45

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I'm certain you're spot on re the nature of the Twiggy Box in terms of its primary purpose and packaging. You may even be correct about the chimney effect being a happy coincidence. However, I'm just as certain Burrell Smith and the Radius Gang took more knowledge away from that project than possessed by those who remained at Apple in terms of getting the most out of the machine, including how NOT to burn up the AB while doing so. wink

Nope, the "baffle" mounted ABOVE the chassis and underneath the drive cage. The plexi prototype's Apple II FDD would have provided the same chimney effect.

102717968.01.01.lg.JPG
http://www.computerhistory.org/collecti … /102717968

Given the location and dearth of cooling slots, any chimney effect for cooling the main transformer and component heatsink farm surrounding it on the AB of that prototype would have been of utmost importance.

Meanwhile, does the operating temperature of those AB components fall within the the ranges I spec'd? The tale of the readouts will tell. wink





Ooh! HP_Mini sprang back to life when I plugged her in the other day! I't's a good bet the "baffle" pics are on the SSD! Bulged batteries evident. Could a 30" drop to concrete cause and immediate Battery poof or contact mismatch? I'm not if sure I tested HP_Mini without the battery installed when I prematurely announced its demise. :-/

Last edited by jt (2015-11-06 19:17:21)

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#4 2015-11-06 20:15:57

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

jt wrote:

Nope, the "baffle" mounted ABOVE the chassis and underneath the drive cage. The plexi prototype's Apple II FDD would have provided the same chimney effect.

Wait, what "baffle" are you talking about here again? The thing to said came with those upgrade kits, the metal box from the Twiggy, what? Color me confused.

Really, honestly, I can't even really fully wrap my head around what you're trying to say. Here's the guts of a compact mac:

Cathode_ray_tube_inside_a_Macintosh_Plus.jpg

Here's a better picture from flickr that shows the bracket area better relative to the board mounting, I'm looking at that as I type the below. I'm also looking at This picture of the Twiggy Mac's internals, featuring the chunky metal box.

Your idea seems to boil down to the idea that having an extra inch and a half of space filled up by the solid box around a 5.25" drive would radically change (and somehow improve) the airflow around the analog board? I'm sorry but I just don't see it. The "floor" to the right (looking from the rear) of the metal cage is already solid up to the edge of the hole that would have been occupied by the larger drive so the air flow coming up from the digital board area past the analog board will still be flowing primarily from the same slot. The metal box does restrict airflow from the digital board from *behind* the drive to a greater degree, so I guess your argument will be that more air heated by said board is going to go through those vents instead of "escaping uselessly" behind the 3.5 inch drive? Really... it sounds incredibly iffy to me; worst case if it *did* work to drive more *significantly warmer air past the analog board* it would come at the cost of increasing the temperature of the air around the digital board, an area that does already get hot enough to contribute to the failure of RAM chips, etc.

It really needs to be reiterated that the design basis for that case was essentially the same as that for the notoriously hot and failure-prone Apple III, IE, that it would to the greatest degree possible utilize radiative cooling, not airflow. Proper ventilation was an afterthought motivated in large part by the terrible failure rate *of the Twiggy-drive Macs* being used by developers. (Who resorted to things like drilling their own holes in the top of the case.) If there was *any* thermal consideration involved in that metal box at any point my jaded guess is some poor engineer shrugged his shoulders and hoped a little more metal would work as a bigger heat sink. tongue


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#5 2015-11-07 01:53:24

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

First, the Twiggy box had a back on it so it acted like a diving bell/candle snuffer. That effectively blocked the opening shown underneath tthe Sony Bracket in your pic and extended farther back, also covering a portion of the almost triangular opening behind it.

The side of the twiggy box ran up alongside the AB components creating a chimney as seen from the rear:
____
|___.| |

Rather than the chassis merely being a less useful choke point next to the Sony Bracket:

___
|__|_. |

The chimney effect would indeed pull air warmed by the LB up across the AB's hottest components, which would heat it further, pulling more air in and faster across the "cooking" RAM ICs. Hot and heated are relative terms, if the TwiggyBox or the Radius baffle helped to speed air across the transformer and heatsink farm as their heat transferred to it, overall airflow through the case would be enhanced.

The Radius baffle acted as a choke point as in the lower diagram, but covered approx. the same openings under and behind the Sony Bracket as the TwiggyBox IIRC. Dunno, I'll have to test that configuration too  .  .  .


"If we knew what we were doing, it wouldn't be called research." Albert Einstein



edit: WTF is the operating temperature range of those AB components anyway? roll

Last edited by jt (2015-11-07 02:00:56)

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#6 2015-11-07 02:34:03

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

Do you have a picture of this "radius baffle"? I still haven't the foggiest of what you're talking about there or how it would install in the case.

If you really want to test this theory remote probe meat thermometers are cheap, you could tape a few inside the case  and see if having your "candle snuffer" there makes a lick of difference. (Remember, you'll have to route the sensor wires out in a way that lets you fully reinstall the original bucket.) For your idea to hold water you'll need to record a *significant* drop of temperature near the most sensitive areas of the AB, which I suppose would include the flyback.)


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#7 2015-11-07 02:38:25

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

(I suggest meat thermometers because the have a useful temperature range between roughly freezing and boiling, which should cover the spread of what you should find in a working computer. )


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#8 2015-11-07 04:00:31

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I have a picture of the Radius dingus somewhere, more than likely on the platters in the HDD that died in the QS'02. I'll do a mock-up of it showing how I recall it working when I have a chance to pull the Drexel 128k/Plus apart and dig up the Twiggy bits.

I'd wanted to do remote sensing of some kind, "Smoke Testing" or IR photography through the clear side panel to figure out what was going on, but the pop-top of the VisibleMacPlus will let me keep it stupidly simple. I can run the Plus long enough for the temp to stabilize in all three configurations, pop the top and take a reading almost immediately of the area in question. I can even duct tape the pistol grip to a makeshift stand mounted to the Plus to keep the angle and distance of the samples identical.
k2-_91864999-4920-465b-b53b-f554455a2040.v1.jpg-7640faf77f5e0080fa67324cd659db9267a0f8bf-optim-450x450.jpg
http://www.etekcity.com/product/100022.html

I'm at least $16.88 curious about this after all these years! smile


I think I'll post a WTS(ee) a Piccie thread over at the barracks, maybe somebody has the Radius part to photograph?

Last edited by jt (2015-11-07 14:12:01)

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#9 2015-11-09 01:47:48

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

jt wrote:

I have a picture of the Radius dingus somewhere

Here's a page with pictures of a Mac Plus with a Radius accelerator installed and I don't see anything that looks like a "Baffle" that blocks any of the spaces that are open behind the floppy drive bracket or otherwise recreates the airflow conditions of a Mac with a twiggy drive installed. It does look to me like there's a fan added which would indeed increase airflow over the analog board (and inside the case in general) but it appears to be mounted on a simple bracket.


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#10 2015-11-09 03:47:30

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I pulled the Drexel128k/Plus down off the display unit and found the base of the TwiggyBox mockup still installed! smile

wIyVkk.jpg

The Radius Dingus was a piece of plastic roughly the size of the floorpan of the mockup. In that position, it would have channeled all the air to its side and back, up across only the AB on the side and CRT neck at the back, but would not have created the MacChimney effect of the walled sides of the TwiggyBox alongside the AB and perpendicular to it up the backside.

wveeCQ.jpg

Here you can see the height of the TwiggyBox with the top of the heatsink farm showing just above the edge.

bD3gpK.jpg

From behind you can see the heatsinks and the transformer in the chimney. Basically, any airflow leaking around and underneath the Sony FDD cage that headed out to the vents on the opposite side of the AB was absolutely wasted, cooling almost nothing. By redirecting all convection airflow into an L shaped plume directed up across the AB side and the CRT neck assembly at the back,  more heat would have been picked up more efficiently. Doing so, expanding in the process, drawing yet more air across the MoBo from the off side vents at the base and up into the L shaped chimney, spreading out across the top of the case to exit vents all around the top, the hottest parts would be directly cooled much more efficiently than appears to have been the case in the 128k-Plus as shipped.

It never ceases to amaze me that a supposedly high-tech company like Apple could miss lessons learned by every low tech manufacturer of Radios and TVs from the beginning of the tube era. It reminds me of POSV, maybe SJ should have hired the pencil protectored engineer who showed up for his interview in a suit instead of humiliating him for wasting his Steveness' precious time because he obviously wasn't "cool." The poor sonofabeyotch prolly' woulda set the story straight right quick on the need for proper cooling. Freakin' stuffed turtleneck. roll

9G3Umo.jpg

Here's the fillet of Mac I'll be using for testing. Pop the top and shoot one of those heatsinks with the gun and see what we see. wink

When I see pictures of the insides of the TwiggyMac, I can "see" the the air flowing under, up and around and then back overtop that Big@$$ Box. There's next to nothing above the thing that needs any cooling at all. Airflow seems like it has to work better at what it's for with the box there than without it to these eyes.

Last edited by jt (2015-11-09 04:18:40)

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#11 2015-11-09 05:36:49

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

But there's no "Radius Dingus" in that Mac Plus with a Radius upgrade. What products did the Dingus come with?

Last edited by Eudimorphodon (2015-11-09 05:37:35)


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#12 2015-11-09 13:06:22

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I don't remember if it was a VidCard or Accelerator. I've only ever seen a pic of it once and never heard of it at any other time. Maybe it shipped with the first gen TPD and they stopped including it at the time of the release of the Radius16 because it didn't really help. tongue

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#13 2015-11-09 13:44:29

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I just spotted the hot glue at the top of the AB and searched the melting temperature of hot glue. The high temperature variant's working range is in on the order oft 190 °C (374 °F) which is well under the 380℃ (716℉) max temp readout of the UV Gun at the top of my to buy list.

I've got the 5 days leading up to Thanksgiving off for some thermal experimentation while I work on a "built-in" storage surround for my 40" Roland CAMM-JET entertainment center. smile

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#14 2015-11-09 13:49:13

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

LOL! In regards the POSV comment above, I realized that SJ was stuck on the notion that the Mac team was designing a computer  .  .  .  the Mac was Apple's first stab at building a TV set! lol

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#15 2015-11-09 20:28:25

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

jt wrote:

When I see pictures of the insides of the TwiggyMac, I can "see" the the air flowing under, up and around and then back overtop that Big@$$ Box. There's next to nothing above the thing that needs any cooling at all. Airflow seems like it has to work better at what it's for with the box there than without it to these eyes.

Well, there's lots of things I can "see" in my head, but that doesn't mean any given one those things I'm seeing makes sense. wink

So, setting aside the whole question of design intent (Of which I think there was absolutely *zero*) with regard to that box providing any cooling function let's think for a moment scientifically about your theory, IE, that having that vertical surface in there would provide some sort of "chimney effect" that would, by itself, improve airflow. Here's a bunch of interesting math-heavy links regarding modeling convective heat flow; if we were smart enough we could probably use the information here to make some educated guesses about how likely that is. So far as I can tell there are two possible mechanisms that *could* provide the flow you're thinking of:

#1: Having the restriction over the transformer and the heat-sink'ed voltage regulators will cause the expansion of the air warmed by those components to "pull" more air than it would if it were simply allowed to "bloom" into the wider space, and/or:

#2: That the plate itself could be heated by those components and act like a more efficient vertical radiator than the surface of the analog board itself.

I sort of think we need to discard trying to do the math for #1; to really work that out we'd essentially have to model the fluid flow inside the 3D space inside the Macintosh and "minds eye guesses" do not count as a rigid model. There is a calculator here for modeling the natural draft achieved through a chimney of X size (height/diameter) with a temperature difference of Y between the drafted fluid and the outside, but trying to apply that here seems doomed to failure for a slew of reasons. We're not modeling a "chimney" that goes from a single warm space to a cooler outer space, we're talking about a passage only 3 inches high that itself is composed of heat producing components on one side and is overtopped with components producing even more heat, like the flyback transformer. We may actually be looking at a situation here where the "exhaust" side of the chimney is warmer than the input, which invalidates the whole model. Therefore to me it seems like the only thing we can even remotely try to model is how much convection having a heated vertical surface of X size might induce if it were the only source of heat in the case and see if that amount of airflow "looks" at all significant.

Here are the equations for ball-parking the amount of airflow you'll get off a heated vertical surface. Looking up the standards for the size of a full-height floppy drive (Which I assume the Twiggy was roughly the same size as) we get a maximum vertical surface area of 82x204mm. That pencils out to a mere 0.017 square meters. We do not know what the values will be for the input air (IE, how warm the air coming up from the area where the logic board resides) verses the temperature of that surface. Remember, the entire Mac consumes less than 60 watts of power and the power going into heating the plate is only coming from whatever radiant energy it absorbs from the components facing it, so in total I can't imagine it "sinking" more than a few BTU.  If you want to do the math and play with some numbers as to how many cubic meters per hour flow you'd get over a plate that size have at it, but I guarantee that the number is going to be pretty shockingly low, particularly in the light of the fact that since the plate isn't a direct source of heat its temperature is highly unlikely to be much different than ambient for that area. (It might actually work better as a "heat engine" if it *did* have the Twiggy drive in it, since all the heat from that would be soaking into it directly; it probably wouldn't be more than about 10-15 watts and only a fraction of it would be confined to the vertical surface rather than radiating off the top. It also might work slightly better if it were in direct contact with the metal heat sinks it faces on the analog board.) If the temperature of the plate is essentially ambient than it's not going to contribute to "accelerating"  at all and all we're left with is the "fluid-dynamic" possibility that the vertical surface there acts like some sort of venturi to constrain the expansion from the active components thereby making them "suck more" from those two holes directly in line with the bottom of the AB. I guess it's not absolutely impossible there could be some affect from that, but I can't imagine the contribution being anything but shockingly small. Maybe if the the "chimney" ran the full length of the case up to the ventilation slots... maybe? since such a panel would actually cause the AB to draw directly to the outside air. But there being any significant effect from that little stub down at the bottom? My tea leaves say no.

But, sure, I guess there's no harm to be done doing your experiment. I do wonder what exactly the target component for your laser will be. If you see anything at all I'll guess you'll see a small increase in temperature in the direct vicinity of the stuff shadowed by the plate (from it reflecting some of the radiated IR), the real question would be whether there's any significant compensatory change in the temperature of something higher up, like the flyback from your hypothetical "blow-dryer" affect. To really make this fair you're going to have to leave the Mac on for enough time for everything to get fully "heat-soaked" (which is probably a couple hours at least) and maintain the ambient room temperature the same between tests. Anything less than, I don't know, 5 degrees Fahrenheit will almost certainly be statistically insignificant.

Last edited by Eudimorphodon (2015-11-09 20:37:24)


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#16 2015-11-10 14:44:44

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

Eudimorphodon wrote:

Well, there's lots of things I can "see" in my head, but that doesn't mean any given one those things I'm seeing makes sense. wink

Actually, that begs the fact that some of them do make sense, which might be a stretch in my case. roll

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#17 2015-11-11 14:07:13

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I was thinking about the Radius Dingus this morning and came up with another notion. Take a look at the pics of the floorpan of my TwiggyBox mockup. Even if there's no appreciable reduction in AB temps, it seems fairly obvious that the dingus/baffle would cause the air entering the case through the offside vents to move across expansion card and MoBo in order to pass through that cramped cubic and escape up through my theoretical L shaped chimney. It's seems obvious that Radius planned something like that with considerable aforethought  .  .  .

.  .  .  of course there's no way to test that theory without resorting to your meat thermometer suggestion or remote sensors as considered in the original thread. :-/

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#18 2015-11-11 19:00:41

ScutBoy
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

This is where Hap uses one of his clear machines - put in the baffle, seal the machine up and let it warm up, and then blow smoke in the bottom vents and watch it move through the machine and where it exits.

Easy smile

Last edited by ScutBoy (2015-11-11 19:01:32)

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#19 2015-11-11 22:20:50

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

Does hap have a clear Plus or minus? Incense in the temple of Macintosh. That's what I thought about using, but decided it wasn't scientific enough. My Plus can be clear on side and back, IR photography also came to mind. The pop-top probably won't work unless I put a black body of some sort into the air stream for measurements. Maybe a vertical piece of steel that will stay stable for long enough to take a good shot or six each time I pop the top? Won't work for the MoBo/Accelerator I have though.

If I were competent to use remote sensors/DIO that would be great  .  .  .  :-/

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#20 2015-11-11 23:21:32

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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I'm not sure if this is what you're looking for, but this is the sheet that came with my Radius 020+FPD upgrade for the Plus:

IMG_3699.jpg

The bit under the floppy drive is solid all the way to the front of the machine. There's a fan that goes with it too, which isn't installed in this picture.

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#21 2015-11-12 02:43:59

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

AHA! Different than I remembered though. Where did the fan go and from where to where did it move air? Did the upgrade come with a replacement wiring harness with that factory lookin' PTO? Curiouser and curiouser.

Radius 16 AND FPD Cards in one Plus? Niiiiiice! smile

Last edited by jt (2015-11-12 02:47:36)

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#22 2015-11-12 16:17:09

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I've been fumbling my way through folklore.org again***** and ran across mention of Hartmut Esslinger and his work on the Apple//c. I've been enamored of this concept rendering from the moment first I saw it  .  .  .
30thafrogdesignprotomac.jpg

.  .  .  it just occurred to me that the decision was made at some point that the Twiggy Drive had to be moved off center for a several reasons:

From a practical standpoint space for and convection cooling of the large components of the A/B would be first and second on that list. I wonder when this decision took place and how difficult it was to get it done.

< almost entirely tangent mode >

Asymmetry seems most decidedly unStevelike, though moving the Twiggy Drive to the off side might be ascribed to aesthetic consideration. The switch from the Apple][ floppy drive to the Lisa's Twiggy Drive with its lopsided grin of a finger access well likely caused an averse reaction by the Steve. He insisted on its use almost up to the end of the Mac's development. Intentionally moving the Twiggy's design "features" off center likely helped. Counterbalanced by the singular Apple Logo, uncharacteristically recessed in its square field greatly improved appearance of the new configuration.

0c3.jpg

mac3ju.jpg

In the switchover to the Sony MicroFloppy, the drive opening wasn't nudged back toward the center as it might have been. To my eye, the constellation like troika of CRT/Logo/FDD access seems right. Note that the KBD port is recessed with Keyboard/KeyPad text in column with the FDD access well and sized to match. The well is also spaced away from the lower right corner in tune with the one unit up and over square recessed @ in the lower left corner. At some point in development, the raised icon (matching the @ logo) for the in-column brightness knob appears to have been added.

With intro of the Apple//c in April 1984 and its two displays, the @apple][ trademark/name/model convention had morphed into a monolithic, recessed @. Later the  @  Plus and @  IIgs with intentional aof logo and text appeared. Interestingly enough, in development, the Lisa2's Logo had waxed monolithic and become recessed in column with (needlessly in terms of function) offset MicroFloppy's finger access well.

AppleLisaFront.jpg
computermuseum pic

The Lisa 2 made its debut the same month as the Mac, the Apple//c appeared three months later. How curious that of three computers in packaging development simultaneously, only the Macintosh retained a nod to the recessed of @apple][ nameplate heritage. neutral

< /drivel >






*****I've been trying (unsuccessfully) to find mention of a four pin grayscale info header's removal from the prototype series that I'd ran across recently. Any help on that front?

Last edited by jt (2015-11-12 16:19:58)

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#23 2015-11-12 17:31:05

jt
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I wonder how the eye pleasing symmetry of the icons panel/asymmetry mix of  logo FDD/KBD connector wells' realignment for the Mac Plus aligned with reorganization/combination of Lisa/Mac divisions and the impending departure of the Steve after his May '85 marginalization by Scully.

msnap1.jpg

I suddenly much prefer the look of the 128k's front bezel to that of the Plus, released eight months after the start of the SJ ruckus.

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#24 2015-11-13 18:57:15

Eudimorphodon
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Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

apm wrote:

The bit under the floppy drive is solid all the way to the front of the machine. There's a fan that goes with it too, which isn't installed in this picture.

Blocking off the natural airflow makes a *lot* more sense if they did so in an attempt to draw an increased quantity of inlet air through a fan. (The logic probably went that if they didn't block the holes the fan might just create a "cyclone" in which the exhaust air was pulled back down to the inlet instead of the fan helping to draw more air through the relatively restrictive ventilation slots in the bottom part of the case.) I remain skeptical that having that in there *without* a fan would improve anything, however. It might increase the airflow through the space where the hole in the baffle is, since the heated air warmed by the logic board wouldn't have anywhere else to go, but said air is going to be significantly hotter than it would be otherwise. And since the degree by which something is cooled by a fluid/gas is in part a function of the temperature difference between the heated body and the fluid it's supposed to be transferring energy to it follows that the higher inlet temperature could well cancel out any gain from increased *local* flow. (I say local because I also doubt channeling convection *alone* like that would increase the total draw from the base inlets. If anything it's possible the local pressure from heating the air trapped under the baffle would reduce natural draw.)


Flap Different.

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#25 2015-11-13 22:43:21

jt
Member
From: Bermuda Triangle, NC USA
Registered: 2014-05-21
Posts: 1,470

Re: TwiggyBoxGambit: Compact Convection Correction . . . Take II

I'm waiting to see position, orientation and hopefully the intention of whoever put the fan in there with that baffle before passing judgement. Middle lil' bro's an ME who does computer packaging (blade servers) once told me that whenever a fan is added into a case, all convection cooling goes out the window  .  .  .  so to speak.

"Stupid is as stupid does." For a brilliant man, SJ pulled some REALLY stupid stunts. roll

I'd like to think the gang at Radius designing a VID/Accelerator Card Combo for the Mac knew a whole lot more about cooling than anyone still complying with the (by then) departed Steve's dictates at Apple  .  .  .

.  .  .  but you never know. :-/

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