In answer to your question,  you will note that Mamiya had no fewer than 
three different 16mm film cassette styles. They are:

A. The original metal drums, identical for use on left or right, no
bridge connecting them.

B. The 2nd generation cassette was very similar in style to the Minolta
in that it had two drums connected by a plastic bridge and each drum
had a cap type cover.

C. The 3rd generation of cassettes had two drums connected by a plastic
bridge and the entire outside shell of the drum lifted off. These shells
were then nearly the height of the cassette (less the height of the
bridge of course).

I will assume that you have style "B".

In the "B" style, if you don't use the spool on the supply side then the
cassette will not be light tight since the spool hole in the cap will allow
light to enter the chamber. Because of this design, you should use the spool
on both the supply and take-up sides. (Same holds true for style "A" drums.
Style "C" requires no spool on the supply side at all.)

To load the cassette in either darkroom or changing bag:

1. If you have the length of film preslit to width and precut to length,
stored in a light tight container, have it handy. Do step 2 and skip
step 3. If you need to slit the film and then load it in the same session.
Do step 2 and then step 3.

2. Lay out the film cassette, spools and caps so that they are in
front of you and looking down at the cassette your arrangement looks like
this:

Caps       0   0
Cassette   0...0  = (supply)....(take-up)
Spools     o   o
Film         O

TURN OFF THE LIGHTS. If you're using a changing bag, arrange the items as
above in the bag.

3. If you need to slit some film to load into the Mamiya cassette, slit
film now to 16mm width and no longer than 20" in lenth.

4. Some of the Mamiya cassette spools came with metal snap on clamps
to secure the film ends to the spools, some cassettes came without them.
If you have the clamps, just slip the end of the film onto the supply
spool under the clamp. If not, tape the end to the supply spool.

5. Roll the film tightly around the spool, leaving about 3" of leader
at the end. Be sure to wind the film clockwise on the spool
so the film path on the spool looks like this "Q..."

5. Place the spool and film in the supply side, the left drum as you're
looking down at the cassette, ie Q....Q, bridge towards you. Make sure
the film leader slips down through the film gate on the drum.

6. Place the cap on top of the supply side.

7. Tape the cap onto the drum to secure it.

You can do the rest of the procedure in dim light:

8. Tape the end of the exposed film leader to the take-up spool. Wind one
turn counter-clockwise. Insert the spool into the take-up chamber, feeding
the film down through the film gate of the drum. Place cap on drum and
tape shut.

9. Using a std screwdriver, turn the X drive in the take-up spool 2
turns, making sure that the film is feeding from the supply to the
take-up side.

The Mamiya 16 should hold a length of about 20" of film, regardless of
base thickness, just like the Minoltas. I have never seen the specs for
exactly how many exposures this yields on the Mamiya but I will try and
find out for you. In the meantime, load up a cassette, put it in the
camera and shoot away. 

Written by Bob Christopher                         Littleton, Colorado USA
email:bob@palmtop.com 

I have prepared several of these "step-by-step" instructions for 
the loading of various film cassettes. Here is one for the Minolta 16.
It assumes only that you will be doing this in the dark, be that in a 
darkroom proper or utilizing a changing bag.

The Minolta 16 cassette consists of 4 parts: 
  1. The body of the cassette which has two drum chambers connected by 
     a plastic bridge.
  2. The cap for the smaller chamber which is the film supply side 
  3. The winding, or take-up spool which fits into the large chamber. 
  4. The cover for the large chamber which is the take-up side of the 
     cassette.

INTO THE LIGHT:

To facilitate fool-proof handling of the cassette in the dark,
assemble the cassette pieces fully so that the cassette is intact. 
Remember, the open end of the take-up spool fits into the bottom 
of the large cap. Now place the cassette upside down in front of 
you, bridge down, film gates close to you, with the small chamber 
on your left. 

Take a small strip of masking tape, about 1/4" x 1" and put it on 
the top center of the cap of the small chamber. Run the tape back 
away from you and about 1/4" passed the back of the cap, now comes 
the trick. Run the tape loosely as if you were creating a handle for
a teacup, just to the lower part of the back of the small film chamber. 
No tape should be touching the backside of the cap.

Turning the cassette 45 degrees clockwise you should see that the 
tape strip looks like a number 7. Turn the cassette 45 degrees
counter clockwise to its original position.

Repeat this for the large chamber. You now have created a simple 
tape hinge that will allow you to flip the caps up and off when 
you are loading the film and then easily flip them back into proper
position once you have the film loaded. This tape hinge, because
it is loose in the back, also prevents any stress to the thin walls
of the cap and prevents any deformation or breakage of the plastic.
 
As you will see, these tape strips will also serve as the seal 
for the caps to the body of the cassette after the film is loaded.
Now, flip the small chamber's cap back, exposing the empty supply 
drum of the Minolta 16 cassette. The large cap can stay closed for
now. 

The only really tedious part of loading film into a cassette
is getting the end of the film to protrude through the film
gate. It took me several feeble attempts before ingenuity took
over and I found a really easy way to accomplish this. Just
take a small strip of paper, about 1" X 1", fold in half
so that you have a V shape. Gently place the folded edge of
the paper into the film gate so that half the paper is inside
the chamber and half of it is outside, then slip the paper
straight down to the bottom of the gate. Be very careful not 
to deform the felt. I've found that by pressing slightly with 
my thumb into the chamber that the film gate will open just
enough to allow the paper to drop easily into place. Fold 
the top, exposed edges of the paper outwards to create a
V shape at the top. The film can then just be slipped 
effortlessly into the V, and slip into the film gate.


INTO THE DARK:

Successful film loading only relies upon two skills:
  1. Don't get your fingers all over the film, and
  2. Make sure the film you are handling lays on a scratch-proof 
     surface.
  
The first skill comes with practice. The second is easy. Here's 
how to make a cheap (free) work surface for film strip handling.
Get a clean cardboard box from which you can cutout a solid piece
about 8x11 inches. If you are going to use a changing bag for the
film loading and not a darkroom, just size the cardboard to fit
the bottom of the bag leaving 3 or 4 inches on either side. Now
take 3 spools of paper backing from 120 rollfilm and tape them
side by side on the yellow (or printed on) side. Turn the strips
over and you have the black paper backing of 120 rollfilm as your
work surface. Just fold it over the edges of the cardboard and
tape to the underside of the cardboard.

Since we already have a cassette that is now easy to handle and simple 
to orient in the dark (remember bridge down, film gates close to you, 
open drum on your left, same as in the light), take a 20-22" length of 
film that has been slit to 16mm (or slightly less) in width. Find the 
the natural curl of the film and begin winding it up into a roll, 
starting with the end closest to you. Make sure the film is laying
on a scratch-proof surface like the one described in the previous
paragraph.

Wind the film into a tight roll whose diameter is smaller than the
supply side chamber you will be putting the film into. At intervals
during the rolling up of the film, pull any slack out of the roll
by holding the roll between your thumb and index finger of one hand
and pulling at the very end of the strip with your other hand. This
takes some practice in order to successfully roll the film without
touching its surfaces.

Note:
If you have difficulty handling the film safely or find that your
hands just sweat too much in the changing bag, just be patient. I
had the same problems when I first started so I just decided to
forfeit a 20" length of film and practiced in the light until
I had the knack. In a few minutes you'll have the feel for it
and your anxiety and apprehension will go away.

Once you have the film wound up into a nice tight roll, leave
about 2" of film free at the end. Since the cassette is there
in front of you with the film gates closest to you, you should
be able to take the film roll and drop it into both the supply
chamber and through the film gate in one step. Once the film is
in place, pull the paper guide out and flip the cap of the supply
side over the top of the cassette and gently seat it in place.
Holding the cap firmly onto the cassette, remove the tape hinge
and use it as a seal around the edge of the cap where it meets
the cassette. The remaining step can be done in the light.

LIGHTS ON...

In dimmed but adequate light you can now take the exposed length
of film from the film gate and draw out another inch or two. Tape
this end of the film to the take-up spool making sure that the
open end of the spool is facing up. I like to tape the take-up
using a 2" length of masking tape. Nearly fold the tape in two
making an elongated U shape. Place the spool in the seat of the U
and tape the film on both the emulsion side and lower side with
the two exposed lengths of tape. slip the film into the film
gate on the take-up side and place the take-up spool, open end up,
into the chamber. Close the cap and seal it with the hinge tape.

Load the film cassette into the camera, fire off two or three 
exposures to advance the film much as you would with a 35mm
camera when advancing the leader.

Remember: You won't always know when your last shot has been made
due to the fact that the end of the supply side of the film roll 
isn't taped or attached to anything. I always cut 22" lengths of
film and fire 18 to 20 shots maximum. After 20 exposures, I 
fire off five or six dead shots and advance the film fully into
the take-up chamber.

BACK TO DARKNESS:

I never, repeat never, send my film for processing in its original
cassette. I unload the film in total darkness, untape the take-up
spool from the end and then roll the strip up just enough so that 
it fits into a light-tight, black plastic film can lined with
120 rollfilm paper backing - black paper side facing the film.
My local film processor has been very successful at developing
my 16mm color neg strips just as if they were 110 film. The prints
are machine processed as well. 

If you have any questions or need clarification on any of these 
steps please feel free to contact me.



  Bob

Bob Christopher                         Littleton, Colorado USA
email:bob@palmtop.com