One of the ways shown above that I have used to align shafting
requires that the shafting be wrapped with tape and or oil less bearings
to equal the diameter of the larger shafting but I do plan to try making
permanent and reusable shaft diameter increasing sleeves sometimes in the
future but haven't done any experiments on it yet .This is how I prefer to
wrap shafting to get the
most precision and it may be overly fussy but it probably
doesn't hurt to try for the best accuracy , the drawing shows how I mark
with a small piece of tape where I first start wrapping so that my last cut
will not overlap this area as it might create a slight bulge . When
doing this and using electrical tape remember to not stretch this type of
tape as it can cause problems , and as with all tapes be careful to avoid
bubbles and the first wrap can be difficult to get aligned up with the shafting
correctly . I have really tried to find oil less bearings that will match
up correctly one inside the other and sometime do but they don't always seam
to match up all the time and when they do they sometimes don't give the needed
diameter , however they do sometimes and even more often do help to lessen
the amount of wrapping to get to the needed diameter .
If you need to permanently increase the diameter of a
shafting , wrapping with fiberglass can work and on this you can try various
cloths in epoxy but I often find that old fiberglass curtains will work
reasonably well providing you use epoxy with them, fiberglass resin gives
pitiful results with this type of fiberglass as it doesn't have the type
of treated surface that makes using fiberglass resin bond well to it
. On shrinking shafting I have found acids such as nitric and nitric plus
hydrochloric for stainless do quite a good job. nitric plus hydrofluoric
will even eat tungsten carbide but this one also eats glass . Tried cutting
holes in metal with these but they always tended to peal off whatever I could
find to protect the rest of the metal but will still gave good etchings
and some interesting results sharpening files and blades before the protecting
material on the opposite side gave out , mine had some accidental dirty
grease protecting one side of the tinny cutting teeth
.really sharpens well however with different results different
ways of course and may suggest some worthwhile experimenting if you have
old files to salvage .
I only just had a chance to roughly test the method below
for getting the ends of shaft to accurately match up at the time I
got this booklet ready but here it is any ways , I hope it might be helpful
.
Usually to secure the ends of shafting and I have most
trouble with really small shafting as it is so flexible that even in a good
jig it can still be off by quite an amount and because of this it can be
extra difficult to get accurately aligned , you can consider wrapping
the tip of the smaller shaft with a thin strip of tape to build up its
diameter to match the larger shaft and then use an extra layer of tape
to hold both ends together , You could then perhaps add an temporary,
extra small layer or pieces of fiberglass to make it stronger and more
secure ,just till it can be built up wit the heavier layers without moving
around. The use of crazy glue could make sense here because the usage is
so small and fast. Then place this into your jig and from this create your
shaft adapter .
An extra way that I have tested as a way to get this extra precision
when placing the ends of shafting together requires more work but might
be worth considering as it seam to be fairly simple to make but must be left
in the shaft adapters after the piece is finished . You can make these from
a mold that makes them all as one piece with epoxy and fiberglass strands
along what
will be lengthwise when cut into thin strips as shown in the middle drawing
. The drawing also shows in the lower left how I made the original mold out
of small precision metal plates with a little modeling clay pinched at the
end of the middle plate . It being all the same thickness and the plate used
to pinch it with is also at the same angle along if full length give reasonably
good precision . Try some soap solution or even a little water on this upper
movable plate and on the edge of the middle plate so it dose a smother job
molding the clay . When you remove both plates you should have a nice strip
of angled clay that you can now make your mold from When you use these you
might decide to trim them into a shorter length to give more room for you
set screw to be attached , but after you have wrapped the part closer to
the ends of the shaft with fiber to hold it securely in place . While it
may not be really necessary you also might consider after wrapping
with a strong fiber to keep these small pieces stable you might trim
these to a shorter length to make more room for your nut to be mounted ,
not shown .
This drawing shows how I should have made my molds but
because I never got a chance to even slightly test this type , thought I
should mention it separately . This should give an improvement because it
will handle even greater shaft size differences and only requires that the
mold be made higher on one edge . For this one you only remove the two plates
b and c but leave the 2 lower ones in place. I have marked with an a and
a small circle the tip where you can cut away extra material so these will
fit on smaller diameter shafts if needed because its really only most important
that they are all the same in the angles that mater . For most precision
it is important that the shafting is cut flat on its ends , sometimes I am
forced to try and get this by using a file and small blocks of metal that
I know to be precision square by clamping them together to make
a jig . A piece of precision cut angle rod would also be good as a jig for
filing the ends flat by simply laying the rod into the piece of angle rod
and using the precision cut ends of the angle rod to guide your file over
the end of the rod Of course what you use to make the walls of your mold
doesn't really mater I sometimes even use Legos myself , but for small blocks
like these it may help to use extra tape or clay to seal up all the small
cracks.
This is an illustration of the first type of bearing mount
I ever made and is especially easy but might not be so good if you have to
match it up with the other side of a gearbox or what have you , however its
great for spotlights and robots heads etc. .On mine I didn't even use a ball
bearing and just substituted with a piece of large diameter and thickness
Teflon tubing on a stainless bolt with the nut soldered on “ yes you
can solder stainless if you soak it in hydrochloric acid first and just apply
solder and soldering flux before it has a chance to dry .The drawing is rather
self explaining , just drill some holes put washers on the screws , spacers
maybe and just wrap the strands to hold the bearing in place .This design
makes a display of how it takes advantage of fibers directional strength
. I found some old selenium TV rectifiers sometimes have excellent small
aluminum spools just right for small mounts of this type. Yes it should work
well to mount these on short pieces of angle rod as mountings similar to
the use below .
On making bearing mounts , I have tried making these by weaving the strands
from the inside of the angle rod because by doing so would eliminate the
need for spacers so that it will mount level on a plate because the
inside of the angle rod would assure this . But it turned out not to work
well because of how it got really difficult to continue adding the strands
, much to soon . The drawing shows how I make mine . You will need to always
pull down on the bearings so that the screw that holds the bearing in place
will be at its lowest point and keep this the same for making more of these
, for all the same size shafting .If you plan to make more than one of the
same type at a time you may find it more accurate to take a piece of angle
rod and drill where you want your holes to be and use it as a stencil to
drill more , but be careful to plan where your holes should be , you have
to figure both where the bearing will be when its pulled down onto the sides
of the screw as well as if you plan to use this stencil from the outside
or inside of the angle rod that you plan to use it on , as it will place
holes in different places due to the thickness of the metal the angle rod
is made from. Its best to drill where you want your holes to be , then use
this to drill your stencil from to avoid confusion . One problem with this
type of bearing mount is that you will still need a putty of epoxy to fill
in the curved part this mounting when it is removed from the jig ,
this is easy to do however , just place it on the inside of a piece of angle
rod treated with mold release and filled with an epoxy putty mix , you might
consider here if you might be able to add some more fiberglass for a little
extra strength . My preference here again is to just use some grease to hold
a layer of aluminum foil in place as a mold release , and then maybe remove
the foil from the piece if needed , .On the bottom where the bolts
that hold it down will be , you will need standoffs that serve as spacers
and hold the washers level , these need to be all of the same height and
of course be greased or treated with mold release so they can be reused
This shows one type of set up , that use these type of mountings with pieces
of angle rod and standoffs on a plate , And yes I have tried molding carbon
fiber angle rod with good results by using 2 angle rods as a mold each with
a thin layer of grease to hold a layer of aluminum foil as a mold release
. I have tried other mold releases but seam to still prefer this method .Don't
forget to try placing your 2 pieces of molded angle rod together to form
square tubing . This would probably be best in some cases to just mold the
angle rod pieces with all the fiber going the length of the mold so that
when the extra fiber is added can add strength the other way as it must be
used any ways when wrapped around them to hold the 2 half's together. It
should also work to make round tubing this way. It is a point to mention
that I have read that composite tubing has been made by wrapping the fibers
around a piece of aluminum tubing and then dissolving it away in acid
This illustration is of how I replaced the bearings of an electric motor
with stainless steel ball bearings .This is simple to do even with the metal
shell missing from the magnets , all you have to do is wrap the rotor with
a thin layer of cardboard to be removed later . The metal shell dose increase
the strength of your magnets but you can easily substitute if needed with
some wrappings of very thin iron sheet .Do keep in mind that carbon fiber
conducts electricity so you can't use it where ever it might short out your
electric brushes
This is a sideways view of the type of silicone mold I use for molding gears
, knobs and rollers and I usually make my gear molds by laying the gear on
to a sheet of glass or some other flat smooth surface . Its important to
remember to always place the shafting onto the gear when the mold is made
so that any castings will fit the shafting at its proper angle . Then when
you chose to use a different shaft diameter use tape and or oil less
bearings to build up or down the shaft diameter to fit the mold or casting
,You will note that my drawing shows a smaller shaft wrapped with tape so
that it will fit the mold . If you plan to place set screws into the
casting , I prefer to first put in small pre made fiberglass sticks against
the shafting into to freshly poured resin and then later mold on the set
screw similar to how I do for shaft adapters and couplings . Do remember
lots of grease and sometimes also aluminum foil for mold release . To get
out all the small bubbles that otherwise will certainly be a problem especially
with small gear teeth , I get good results using a small brush or other tool
but maybe try vacuuming. In low complexity molds you sometimes can get away
with very slowly filling your mold by letting your resin slowly flow onto
the mold surfaces . The silicone resins I buy to do this are very viscous
rather like cool molasses ,need to be mixed by weight and for best results
also needs to be vacuumed to get out all the air bubbles . Addresses to get
it are included elsewhere and the suppliers supply a good amount of information
on how to use it. Do remember to test or find out if the type of modeling
clay you intend to use can inhibit curing because there is more than one
type of silicone you may need to chose depending on what properties are best
for your needs . Polyurethane's can also be considered but as of now I only
have experience using it to make rollers and kevlar reinforced belts .
If you do chose to make a mold from gears it may make sense to chose
a gear that will allow you to make many of the one and they will all match
together with the smaller inner gear fitting with its outside of the
next . This can be a real advantage sometimes as it allows you to get by
with fewer molds.
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