I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

Ignoramus10114 fired this volley in
:

, I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

What's the application? The 8-32 would be a stronger bolt, with more
thread cross-section. But it may not be necessary for whatever you wish to
hold.

L

Ignoramus10114 fired this volley in
:

6-32

PS... a lot of heat-sink _component_ mounting hardware comes in M2.5x.45
size, for mounting things like TO-3 and TO-220 packages. That's smaller
than 6-32.

L

On 2015-04-05, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus10114 fired this volley in
:

, I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

What's the application? The 8-32 would be a stronger bolt, with more
thread cross-section. But it may not be necessary for whatever you wish to
hold.

L

strength not an issue

Ignoramus10114 fired this volley in
:

strength not an issue


Then one sizes it according to what you want to mount.

I mentioned 2.5x.45 metric... some also use 3 x 0.5mm, but even that's
smaller than 6-32.

If you need to mount through screw insulators (like for mounting a
transistor or a floating-case regulator like an LM-317, you may be hard-
put to find any insulators that will fit even 6-32... metric has more-or-
less filled that market.

Lloyd

On Sunday, April 5, 2015 at 10:34:56 AM UTC-4, Lloyd E. Sponenburgh wrote:
Ignoramus10114 fired this volley in
:

strength not an issue


Then one sizes it according to what you want to mount.

I mentioned 2.5x.45 metric... some also use 3 x 0.5mm, but even
that's smaller than 6-32.

If you need to mount through screw insulators (like for mounting
a transistor or a floating-case regulator like an LM-317, you may
be hard-put to find any insulators that will fit even 6-32... metric
has more-or-less filled that market.

With a rapidly expanding international market where demand for metric outstrips demand for trade (in everyplace but the US), its not surprising.

On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

Always tap aluminum that will be stressed ..as course as possible.

Particularly in thing sections or places where you will not be using
more than 2x/diameter.. of depth

On Sunday, April 5, 2015 at 5:47:16 AM UTC-7, Ignoramus10114 wrote:
I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

Either would work, assuming the aluminum is thicker than 1/16 inch..
you never want less than two threads.
Be sure to check/flatten the machined surface (I sometimes rub it down
with a whetstone) if there's any deformation, or the flat-to-flat
heat transfer interface will be compromised.

On Sun, 5 Apr 2015 09:30:11 -0700 (PDT),
wrote:

On Sunday, April 5, 2015 at 10:34:56 AM UTC-4, Lloyd E. Sponenburgh wrote:
Ignoramus10114 fired this volley in
:

strength not an issue


Then one sizes it according to what you want to mount.

I mentioned 2.5x.45 metric... some also use 3 x 0.5mm, but even
that's smaller than 6-32.

If you need to mount through screw insulators (like for mounting
a transistor or a floating-case regulator like an LM-317, you may
be hard-put to find any insulators that will fit even 6-32... metric
has more-or-less filled that market.

With a rapidly expanding international market where demand for metric outstrips demand for trade (in everyplace but the US), its not surprising.

That has little to do with it. Except for construction and
transportation equipment, it's mostly a matter of whether the industry
is heavily involved with science, in which case US fasteners are
metric fasteners, just as they are everywhere else, or if it has an
international supply chain.

It's useful to look at three markets: the market for off-road
equipment (mining, construction, etc.); the market for automobiles;
and the market for electronic devices.

In the first case, the issues are that the market is truly global and
that the equipment has to be repairable around the world. Thus,
Caterpillar was the first large US company to go 100% metric, beck in
the '70s.

In the case of automobiles, US-built cars have never had much of a
global market but they are now the end of a global *supply chain*. It
is cheaper, and more flexible, to use metric fasteners for US-built
cars, when they may be built from parts supplied by 20 different
countries.

Electronic devices are designed and built in an environment that is
close to the underlying science, where metrics have been the lingua
france in the US for most of a century. Metrics are followed in the
engineering and in the assembly; repair is a miniscule economic issue.
Also, the supply chain is not only multinational, but also ad hoc; you
may not know this week where your parts will be coming from next week.

The upshot is that, with 70% of our economy based on domestic
consumption, there is little or no economic advantage to making
sweeping changes to metrics in other industries. Thus, change is slow.
And it has little advantage for anyone other than those industries
described above.

--
Ed Huntress

On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?
Both are 32 threads per inch, so how is one "less course"?

On 4/5/2015 1:40 PM, Ed Huntress wrote:
SNIP


The upshot is that, with 70% of our economy based on domestic
consumption,

SNIP

70% of every product purchased in the U.S. is made in the U.S.? Wow, I
didn't think it was that high.

whit3rd fired this volley in news:07594162-52db-470a-
:

Be sure to check/flatten the machined surface (I sometimes rub it down
with a whetstone) if there's any deformation, or the flat-to-flat
heat transfer interface will be compromised.

That would truly be a sin on a nicely anodized heat sink!

If it's not flat, it's junk anyway, I guess.

Lloyd

On Sun, 05 Apr 2015 15:25:46 -0400, Steve Walker
wrote:

On 4/5/2015 1:40 PM, Ed Huntress wrote:
SNIP


The upshot is that, with 70% of our economy based on domestic
consumption,

SNIP

70% of every product purchased in the U.S. is made in the U.S.? Wow, I
didn't think it was that high.

70% of our GDP is domestic consumption. That's net of imports and
exports.

--
Ed Huntress

Ignoramus10114 wrote:

I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?
6-32 works fine. I do these often. A good, sharp tap (not the horrors from
the local hardware store) work quite well. I use "Alum-Tap" from Wibro as a
tapping fluid, it is incredible stuff. Makes the tap go in like it was
already threaded.

Jon

Jon Elson fired this volley in
:

A good, sharp tap (not the horrors from
the local hardware store) work quite well.

Oh, I don't know... if I want a 'standard' straight-fluted tap without
having to wait, Hansons are pretty good quality. 'Never got a dull one,
nor one not accurately-cut. They cut freely and don't leave any more
burrs than any other reasonably well-made tap.

I prefer spiral-flute taps for most work, because about 3/4 of my stuff
is blind holes; but there's nothing wrong with a Hanson tap. That's what
ACE carries - carded, one per. I don't know about your local hardware
store.

LLoyd

LLoyd

On Sun, 05 Apr 2015 15:25:46 -0400, Steve Walker
wrote:

On 4/5/2015 1:40 PM, Ed Huntress wrote:
SNIP


The upshot is that, with 70% of our economy based on domestic
consumption,

SNIP

70% of every product purchased in the U.S. is made in the U.S.? Wow, I
didn't think it was that high.

On durable goods..I doubt its 25%

Gunner

On Sun, 05 Apr 2015 14:31:14 -0700, Gunner Asch
wrote:

On Sun, 05 Apr 2015 15:25:46 -0400, Steve Walker
wrote:

On 4/5/2015 1:40 PM, Ed Huntress wrote:
SNIP


The upshot is that, with 70% of our economy based on domestic
consumption,

SNIP

70% of every product purchased in the U.S. is made in the U.S.? Wow, I
didn't think it was that high.

On durable goods..I doubt its 25%

Gunner

The dollar percentage of durable goods sold in the US and made in the
US was 66.6% in 2010. The overall percentage of dollar value of
consumer imports, in all categories including oil, was 11.5%, of which
the actual cost was 7.3%. The remaining 4.2% goes to US
transportation, wholesaling, and retailing markups.

If you follow US manufacturing and trade for a decade or more, you'll
realize that almost every popular conception about our manufacturing
and trade is wrong.

http://www.frbsf.org/economic-resear...made-in-china/

--
Ed Huntress

On Sun, 05 Apr 2015 07:59:56 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ignoramus10114 fired this volley in
:

, I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

Both are the same pitch, 32tpi, Ig. So what's your real question?


What's the application? The 8-32 would be a stronger bolt, with more
thread cross-section. But it may not be necessary for whatever you wish to
hold.

Yeah, original posters, please don't say what it's _for_. sigh

--
When a quiet man is moved to passion, it seems the very earth will shake.
-- Stephanie Barron
(Something for the Powers That Be to remember, eh?)

6-32 is a course, ie nc, thread. 8-32 is a fine thread, ie nf. The fine
threads do less cutting relative to the screw's major diameter.
The 8-32 will be less likely to break than the 6-32 which, in steel, is
a consideration. In aluminum probably either one would free of worry.
Maybe the 8-32 would be a little freeer.

Hul


Ignoramus10114 wrote:
On 2015-04-05, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus10114 fired this volley in
:

, I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?

What's the application? The 8-32 would be a stronger bolt, with more
thread cross-section. But it may not be necessary for whatever you wish to
hold.

L

strength not an issue

"Ignoramus10114" wrote in
message ...
I have an aluminum heatsink that I need to tap , I wanted to know if
I
should use 6-32 or some less coarse thread like 8-32 would be
better?

I've never had a breakage problem with good-quality 6-32 taps in
aluminum, if that's your worry. If possible I use two flute spiral
point (gun) taps in through holes and kerosine etc for the lubricant,
and I don't start the tap without some sort of squareness guide,
either the mill or a hand-held fixture like this:
http://www.spaco.org/Blacksmithing/TapDrillBlock.htm

Some people prefer cubical ones.

-jsw

I learned something cool, I do not need to tap anything! If I drill a
1/8" hole, a 6-32 screw taps it for itself very nicely.

i

Ignoramus10114 fired this volley in
:

If I drill a
1/8" hole, a 6-32 screw taps it for itself very nicely.

Not really, Ig. If your 1/8" drill made an accurately-sized hole, it would
be a VERY slight threadform.... .1380 in a .1250 hole only leaves about 7-
thou of thread engagement. Unless it's only decorative AND the 1/8" drill
is tuned up and used right, that's a 'barely holds' situation.

The called-out tap drill is #36 (0.1065), meaning about 16-thou of thread
engagement, when done right.

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley
in . 4.170:

The called-out tap drill is #36 (0.1065), meaning about 16-thou of
thread engagement, when done right.

ps... that's all at the 'imaginary' fit of 100% threadform. It's less in
practice.

Lloyd

On Sun, 05 Apr 2015 19:56:51 -0500, Ignoramus10114
wrote:

I learned something cool, I do not need to tap anything! If I drill a
1/8" hole, a 6-32 screw taps it for itself very nicely.

i

In Waspalloy?

On Sun, 05 Apr 2015 20:21:40 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley
in . 4.170:

The called-out tap drill is #36 (0.1065), meaning about 16-thou of
thread engagement, when done right.

ps... that's all at the 'imaginary' fit of 100% threadform. It's less in
practice.

Lloyd

Youd be lucky to get 75%

On Sun, 05 Apr 2015 09:30:13 -0500, Ignoramus10114
wrote:

snip
strength not an issue
Have you considered adhesive, even hot melt? Another
possibility is drive screws typically used to mount labels
on machines. http://tinyurl.com/ov9n6d4 Self tapping?
http://tinyurl.com/njbqope suggest rollform [no
chips/flakes] square or torx drive.

--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"

On 4/6/2015 11:20 AM, Lloyd E. Sponenburgh wrote:

Not really, Ig. If your 1/8" drill made an accurately-sized hole, it would
be a VERY slight threadform.... .1380 in a .1250 hole only leaves about 7-
thou of thread engagement. Unless it's only decorative AND the 1/8" drill
is tuned up and used right, that's a 'barely holds' situation.

The called-out tap drill is #36 (0.1065), meaning about 16-thou of thread
engagement, when done right.

1/8" is the specified hole diameter for roll tapping a 6-32. Admittedly,
running a screw in, is not exactly proper thread forming, but in some
situations, should work OK, if loads are low and servicing not likely.
Just as much a factor I'd think, is the probability that the screw crest
will deform due to not being hardened, and I believe this more than the
hole size would reduce the strength.

Jon

On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus10114 fired this volley in
:

If I drill a
1/8" hole, a 6-32 screw taps it for itself very nicely.

Not really, Ig. If your 1/8" drill made an accurately-sized hole, it would
be a VERY slight threadform.... .1380 in a .1250 hole only leaves about 7-
thou of thread engagement. Unless it's only decorative AND the 1/8" drill
is tuned up and used right, that's a 'barely holds' situation.

The called-out tap drill is #36 (0.1065), meaning about 16-thou of thread
engagement, when done right.

Lloyd

Lloyd, I used those holes to mount TO-220 voltage regulator chips, not
for anything structural. worked great!

Ignoramus32423 fired this volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips, not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every sort of
failure you could count -- from taking shortcuts. Shortcuts just never
work in a temperature-cycling environment.

Lloyd

On 2015-04-05, wrote:
On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?
Both are 32 threads per inch, so how is one "less course"?

Because of bigger diameter.

i

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 4.170...
Ignoramus32423 fired this
volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips,
not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and
lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every
sort of
failure you could count -- from taking shortcuts. Shortcuts just
never
work in a temperature-cycling environment.

Lloyd

How careful you need to be depends on how close to the rating you are
operating. TO-220s aren't fussy at a few Watts but need thermal
analysis as you approach 20W.

http://www.diyparadiso.com/component...pnotes0899.pdf
"Belleville washers, or compression washers are generally considered
the
preferred method of attachment to a heat sink."

-jsw

On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus32423 fired this volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips, not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every sort of
failure you could count -- from taking shortcuts. Shortcuts just never
work in a temperature-cycling environment.

Hm, this is a good point, I did not think about it.

The story is as follows.

My son and I made a robot for a kids homemade robot competition called
"robocross". He won his local competitions and we will be going to the
Illinois state competition.

Since the state competition is so important and there is a chance for
him to become semi-famous if he wins it, we decided to make another
robot.

Here's a picture of it, more or less completed:

http://www.machinerymoverschicago.com/blog/Robocross/

I will hopefully add more pictures and documentation soon.

Anyway, if you look at the controller, you see that there is a
rechargeable battery attached on the bottom, and a black heatsink
attached to the top.

There is a hole in the plastic box where the heatsink attaches, and in
that hole, there is three positive voltage regulators. One for 10v to
drive the lifting arm, and two 5v regulators to drive tracks. The
reason for using different voltages is that 10v is too much for the
tracks, the robot becomes not controllable.

The robot itself is intentionally made to work like a skid steer
loader like Bobcat T300. (I have a S300 myself).

The competition itself allows only 3 minutes driving time.However, he
will spend hours preparing for the competition, and so, the robot
needs to be heavy duty enough not to fall apart or burn out during
practice.

The regulators are KA7810 3-Terminal 1A 10V Positive Voltage
Regulator, and two 1.5A 5V L7805CV Postive Voltage Regulators.

The good news is that, as they run, even after a while, the heatsink
is only barely warm. I had an undersized heatsink (a small copper bar
inside) before and it would get very hot. But with this aluminum
heatsink, everything is nice and cool.

i

On Mon, 06 Apr 2015 08:13:53 -0500, Ignoramus32423
wrote:

On 2015-04-05, wrote:
On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

I have an aluminum heatsink that I need to tap , I wanted to know if I
should use 6-32 or some less coarse thread like 8-32 would be better?
Both are 32 threads per inch, so how is one "less course"?

Because of bigger diameter.

i

A couple of minor points: You can tap aluminum to a higher thread
percentage than steel, because it takes so much less force to cut. But
there's little advantage to cutting deeper than 70% depth in any
material.

And two, if you have any old Tapmagic lying around (we who have it
hoard it like it's fine whiskey), don't use it on aluminum unless it's
the version that says "aluminum." It will boil and form a foul, black
gummy mess as it eats your aluminum for lunch.

Oh, and one more thing: "coarse" is not "course." d8-)

--
Ed Huntress

On Mon, 06 Apr 2015 08:40:51 -0500, Ignoramus32423
wrote:

On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus32423 fired this volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips, not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every sort of
failure you could count -- from taking shortcuts. Shortcuts just never
work in a temperature-cycling environment.

Hm, this is a good point, I did not think about it.

The story is as follows.

My son and I made a robot for a kids homemade robot competition called
"robocross". He won his local competitions and we will be going to the
Illinois state competition.

Since the state competition is so important and there is a chance for
him to become semi-famous if he wins it, we decided to make another
robot.

Here's a picture of it, more or less completed:

http://www.machinerymoverschicago.com/blog/Robocross/

I will hopefully add more pictures and documentation soon.

That's cool! (Shades of my old Erector set, but many generations
ahead.)


Anyway, if you look at the controller, you see that there is a
rechargeable battery attached on the bottom, and a black heatsink
attached to the top.

There is a hole in the plastic box where the heatsink attaches, and in
that hole, there is three positive voltage regulators. One for 10v to
drive the lifting arm, and two 5v regulators to drive tracks. The
reason for using different voltages is that 10v is too much for the
tracks, the robot becomes not controllable.

The robot itself is intentionally made to work like a skid steer
loader like Bobcat T300. (I have a S300 myself).

I like it! (What, no paint on the tubafore?)


The competition itself allows only 3 minutes driving time.However, he
will spend hours preparing for the competition, and so, the robot
needs to be heavy duty enough not to fall apart or burn out during
practice.

The regulators are KA7810 3-Terminal 1A 10V Positive Voltage
Regulator, and two 1.5A 5V L7805CV Postive Voltage Regulators.

The good news is that, as they run, even after a while, the heatsink
is only barely warm. I had an undersized heatsink (a small copper bar
inside) before and it would get very hot. But with this aluminum
heatsink, everything is nice and cool.

Great. Good luck to your son.

--
When a quiet man is moved to passion, it seems the very earth will shake.
-- Stephanie Barron
(Something for the Powers That Be to remember, eh?)

"Ignoramus32423" wrote in
message ...
On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com
wrote:
Ignoramus32423 fired this
volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips,
not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and
lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every
sort of
failure you could count -- from taking shortcuts. Shortcuts just
never
work in a temperature-cycling environment.

Hm, this is a good point, I did not think about it.

The story is as follows.

My son and I made a robot for a kids homemade robot competition
called
"robocross". He won his local competitions and we will be going to
the
Illinois state competition.

Since the state competition is so important and there is a chance
for
him to become semi-famous if he wins it, we decided to make another
robot.

Here's a picture of it, more or less completed:

http://www.machinerymoverschicago.com/blog/Robocross/

I will hopefully add more pictures and documentation soon.

Anyway, if you look at the controller, you see that there is a
rechargeable battery attached on the bottom, and a black heatsink
attached to the top.

There is a hole in the plastic box where the heatsink attaches, and
in
that hole, there is three positive voltage regulators. One for 10v
to
drive the lifting arm, and two 5v regulators to drive tracks. The
reason for using different voltages is that 10v is too much for the
tracks, the robot becomes not controllable.

The robot itself is intentionally made to work like a skid steer
loader like Bobcat T300. (I have a S300 myself).

The competition itself allows only 3 minutes driving time.However,
he
will spend hours preparing for the competition, and so, the robot
needs to be heavy duty enough not to fall apart or burn out during
practice.

The regulators are KA7810 3-Terminal 1A 10V Positive Voltage
Regulator, and two 1.5A 5V L7805CV Postive Voltage Regulators.

The good news is that, as they run, even after a while, the heatsink
is only barely warm. I had an undersized heatsink (a small copper
bar
inside) before and it would get very hot. But with this aluminum
heatsink, everything is nice and cool.

i

If you used an LM317 adjustable regulator for the tracks you could
tune the voltage for best performance while retaining control, and
waste less of the battery's energy as heat. You could put a knob on
the voltage adjustment pot so you have a throttle instead of just
on/off control.

-jsw

On 2015-04-06, Jim Wilkins wrote:
"Ignoramus32423" wrote in
message ...
On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com
wrote:
Ignoramus32423 fired this
volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips,
not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and
lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every
sort of
failure you could count -- from taking shortcuts. Shortcuts just
never
work in a temperature-cycling environment.

Hm, this is a good point, I did not think about it.

The story is as follows.

My son and I made a robot for a kids homemade robot competition
called
"robocross". He won his local competitions and we will be going to
the
Illinois state competition.

Since the state competition is so important and there is a chance
for
him to become semi-famous if he wins it, we decided to make another
robot.

Here's a picture of it, more or less completed:

http://www.machinerymoverschicago.com/blog/Robocross/

I will hopefully add more pictures and documentation soon.

Anyway, if you look at the controller, you see that there is a
rechargeable battery attached on the bottom, and a black heatsink
attached to the top.

There is a hole in the plastic box where the heatsink attaches, and
in
that hole, there is three positive voltage regulators. One for 10v
to
drive the lifting arm, and two 5v regulators to drive tracks. The
reason for using different voltages is that 10v is too much for the
tracks, the robot becomes not controllable.

The robot itself is intentionally made to work like a skid steer
loader like Bobcat T300. (I have a S300 myself).

The competition itself allows only 3 minutes driving time.However,
he
will spend hours preparing for the competition, and so, the robot
needs to be heavy duty enough not to fall apart or burn out during
practice.

The regulators are KA7810 3-Terminal 1A 10V Positive Voltage
Regulator, and two 1.5A 5V L7805CV Postive Voltage Regulators.

The good news is that, as they run, even after a while, the heatsink
is only barely warm. I had an undersized heatsink (a small copper
bar
inside) before and it would get very hot. But with this aluminum
heatsink, everything is nice and cool.

i

If you used an LM317 adjustable regulator for the tracks you could
tune the voltage for best performance while retaining control, and
waste less of the battery's energy as heat. You could put a knob on
the voltage adjustment pot so you have a throttle instead of just
on/off control.

-jsw



Jim, you are right. I actually have several LM317T regulators. I just
wanted to take the easy route. I wish that I could somehow have a
ramp-up of speed, though, not go from zero to full throttle in an
instant.

i

On 2015-04-06, Jim Wilkins wrote:
If you used an LM317 adjustable regulator for the tracks you could
tune the voltage for best performance while retaining control, and
waste less of the battery's energy as heat. You could put a knob on
the voltage adjustment pot so you have a throttle instead of just
on/off control.


Oh, and why would LM317 waste less energy as heat?

Ignoramus32423 fired this volley in
:

The good news is that, as they run, even after a while, the heatsink
is only barely warm.

What you did not say was 1) the raw battery voltage, 2) the current (both
peak and average) for the arm 3) the current(ibid) for the tracks.

Like Jim said, at only a few watts, nothing's in particular danger here.

A star washer works ALMOST as well as a Bellville spring, so long as you
don't torque it down flat.

Lloyd

Ignoramus32423 fired this volley in
:

Oh, and why would LM317 waste less energy as heat?

It would not. It's a linear regulator, also, and disspates exactly
whatever is the drop*current across itself.

But it's darned handy for 'tuning' stuff.

There is a way, with an LM317 to get a 'soft start'. National Semi shows
a circuit or two that does that.

Having that constant-current output on the reference lead can give you
interesting possibilities.

LLoyd

On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus32423 fired this volley in
:

The good news is that, as they run, even after a while, the heatsink
is only barely warm.

What you did not say was 1) the raw battery voltage,

12v nominal

2) the current (both peak and average) for the arm

Not sure, not a lot. The arm operates very intermittently.

3) the current(ibid) for the tracks.

Not sure what is the current for the 5v tracks, but my best guess is 1.2
amps when driving in a straight line, and about 3A when turning on a
dime.

Like Jim said, at only a few watts, nothing's in particular danger here.

A star washer works ALMOST as well as a Bellville spring, so long as you
don't torque it down flat.

OK, I will add something. I will also add heatsink paste, I will
receive it on Tuesday. I could not find my old one.

i