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