To develop the claws I literally scaled 50 or more photos to get the right dimensions from all angles. Once this was achieved the information was loaded into a CAD program and a template was created. This template was used to sculpt the masters from bass wood. The bass wood masters were then given to a pattern maker who created the pattern which is used to make the sand molds to cast the claws in aluminum. A real important point to keep in mind is that the pattern maker purposely made the claws slightly oversize to compensate for surface imperfections that are unavoidable in a sand casting process. This leaves plenty of room to sand the claws down and polish without reducing the original dimensions.
Polishing the Claws
First off, DON’T BE AFRAID OF ALUMINUM. Although it requires more “elbow grease” than resin it is actually quite easy to work with and the results are well worth the effort.
· Dust mask and safety goggles. Very important as it is not healthy to breath in metal dust particles or have them get in your eyes. Basically you need these items when working on any part of the robot. Fiberglass and resin dust is very bad stuff to breath in but with proper precautions there’s no problem.
· 2 packs of assorted grit emery paper (for sanding metal). It is usually black in color and can be used wet which is more desirable. It can be found at any automotive, hardware or home center.
· Sanding block (optional). This helps with sanding the flat surfaces.
· Dremel tool (optional) with the round sanding drums. This can be a great help when polishing the inside of the rounded part of the claws. You can also use a drill with the same type of round drums. Again these are easily found at a hardware or home center.
· Polishing wheel and polishing compound. Although polishing can be done by hand it is a whole lot easier with a polishing wheel. These are the 5" cloth buffing wheels you mount to your grinder (if you have one) or to a drill. The polishing compound is sold in sticks. Look on the packaging to find one suitable for aluminum or soft metals. These are also easily found in a hardware store or home center.
Now for the fun part. The first
thing you need is a stable work table and plenty of newspaper or plastic
as this is a little messy. You can sand the claws either wet or dry,
however, sanding them wet creates less dust and keeps the emery paper from
clogging. To wet sand just get a pail of water and dip the paper
in before sanding. Every so often dip again in the water to unclog
the paper. Start with the roughest grit paper for the initial sanding
to remove all lumps and pits. I use a sanding block on the flat surfaces
as it makes it easier on your hands. I wouldn’t try completing the
job in one evening. I took a couple of evenings each time using a
finer grit of paper. Also, after you are finished a sanding session
wash the claws off with dish soap and water to reveal what you’ve done
so you’ll know what has to be gone over again.
Once you get to the finest grit and have a nice satin finish you can start buffing. You can either buff the claws using a buffing wheel mounted to your table grinder or put the claws in a vice and use a hand drill with buffing wheel attached. While the buffing wheel is spinning you load it with the polishing compound by holding the stick against the wheel until it is covered. You then start buffing the claws using a back and forth motion with medium pressure. Don’t try to do too much at once. Start at one end and work your way down. I suggest keeping a clean rag on hand to clean off the black compound that is deposited so you can see how you are doing. Again, don’t try to do this all in one night. After a buffing session clean the claws with a mixture of ammonia, dish soap and warm water. This will remove all the polishing compound residue and reveal what still needs to be done.
They will be finished when they have the shine you desire. Some like them shinier than others. Some builders even polish them then sand with the finest emery to create a nice satin shine. The choice is yours !!
Painting the Claws
To prep the claws for painting is much the same as the above except that you don’t have to remove all of the pits or voids as these can be filled in with putty. I basically use automotive body filler like “Bondo” which can be purchased at any automotive store. Once the claws are sanded to a desired smoothness you can smear a coat of body filler on them and sand smooth again. Once you are satisfied with the finish prime the claws with a self etching primer that is used for aluminum. This can also be purchased at an automotive supply store. After priming any other minor flaws can be filled using a glazing or spot putty which is designed to be put on over primer. Again, readily available in an automotive store. Once the final coat of primer is on let it dry for at least 24 hours before painting red.
If anyone has any other questions I can reached via E-mail at JMKWWK@aol.com.
Thanks and have fun !!!