Radar. You can never have too much radar...
The B9 radar section can be considered to have 3 parts: Lower section, Upper section
or "clutch pak", and the rotating ear sensors.
The lower radar section looks deceptively
simple, its just a low cylinder with a recess. I suppose one could find a solid hunk of wood/plastic and turn it on a lathe
and that would be it. But if this were left solid it would be quite heavy. Of course it could be hollowed out but that would
take a long time.
I did look for existing things like buckets
and food containers that were close, nothing found.
So make one from scratch. Simple, make
two circular disks, a narrow band and some reinforcing blocks for the ears and the seam where the band ends.
The disks are 1/4" thick and the band is 1/8" thick. Each disk has a groove routered
into it 1/4" wide and 1/8" deep. This allows the band to be placed accurately and also gives the 1/8" deep ribs along the
top and bottom edges.
Both the disk and band are made of a material called Sintra. This is an expanded
PVC material. Its very popular with the Star Wars crowd who make their Storm Troopers costumes from it. Sintra is very easy
to cut, form, glue and paint.
With the reinforcing blocks in place the band is glued and clamped in place. The glue is just normal
plastic pipe solvent weld.
The ears are actually one of the trickier
parts on the robot. The original builders had problems: one story is that the mechanism that drove the ears was too noisy
and Mr. May could not hear his directions so they turned them off. The other story is that they just broke. A few episodes
in the first season did have the ears working and the first episode in the second year they were working too but after that
not much was seen of the ears spinning again.
There are three typical ways to do ears.
It is quite common to use tiny gear motors installed in the ends. This works well but the motors are expensive.
Many builders do not animate the ears.
Thats ok, very tempting. But its such a nice effect when its working, a really must have.
Others use some sort of mechanical drive to get the ear sensors to turn using
a "non-tiny" motor.
So to make the” ears. It looks
like the original ears did not have the tiny electric motors but had a right angle gear system. A suitable, and small, right
angle gear set can be found in common dentist drills. I got a set on E-bay.
The supports were made from solid aluminum
round. The horizontal part was drilled out to accept one section of the drill and the vertical part is separate to allow the
rest of the gear set to be installed. These parts will be held together with loctite or a small set screw.
It was very helpful to have dentist drills that came apart (unscrewed). This design
would not have worked without this feature: The drill end is too big to fit in any possible hole you could drill within the
limits of the horizontal support. Look close and you can see one of the drill ends in the support. Vertical part is removed,
the drill end is inserted in the hole, the other part of the dentist drill is screwed into the drill end with a special tool
and the vertical part replaced.
Upper radar section
The upper radar section is a bit more
difficult to make then the lower. The most common way to make it is by stacking disks of varying diameters of acrylic to build
up a solid chunk of plastic. Ribs are added as well as a hub part. Fairly simple.
My intention had been to take a short
length of 7” dia acrylic tube and cut 1/8” grooves in it. Very simple. But to buy the tube and a few other pieces
could have cost close to $100.
Since I was temporarily low on funds
I had to make the upper radar section out of something else. Actually I had the material just laying around: Sintra. Last
year I tried to make knee bellows out of a sheet of 1/8” thick Sintra, utter failure. But that was a heat forming experiment
that did not have enough homework done. To use Sintra in place of acrylic or even wood seems to work well.
So the 1/8” thick Sintra would
work for the body of the upper radar and I had scraps around of some 1/4” thick Sintra as well. Only the hub remained
to find material for. An easy find: PVC pipe was the correct 4 1/2” diameter.
Sintra is much easier to work with then
acrylic. In a short time the 10 circles (5 disks 7 1/8” dia and 5 disks 6 7/8” dia) were done. A center hub made
of PVC pipe was cut and its end tapered. A little work on the lathe and milling machine and its done.
Here it is befor painting. It does look a little odd with the blue and black sintra
and the white PVC pipe. Having a taper on the center hub is a nice effect.