Handy jig I use for placing wheels and for one way to get the shaft in
exactly the center of a tube for a hydraulics cylinder below. Of course
this is easy to make in a similar way that you can use an 8 track flywheel
or similar to mount the piece of angle rod in epoxy at an accurate 90 deg
angle,
I can think of lots of ways to try making hydraulic cylinders
and one of the more obvious problems is on how to get your shafting be exactly
placed down its middle, otherwise it could bind up and cause other problems
. This is one type of part where testing at lest one of your finished
pieces , might be an especially good idea because of the dangers of high
pressures, especially if you are planing for high performance uses . After
all you can make more and improve as you go. If you do consider testing you
will need to consider doing this underwater and or behind a protective
wall to protect from fragmentation , and it is especially bad with
carbon fiber because of how it splinters . This would not be necessary if
you do not plan for anything over light duty work
This is at least one way you can try to align shafting to make hydraulic
cylinders , by placing the above jig on both sides of a shafting with
triangular wedges all made from the same pattern , mold or even old plastic
geometry triangles and for this it might be advisable to at least use clay
to help hold them in place . For this to work your cylinder liner
tubing ,will need to be cut or molded very evenly at its ends and inner edge
. Metal liners are advisable for wear resistance but may not need much thickness
with the carbon fiber wrapped around the outside . . Other materials might
also be worth considering such as Teflon if you don't mind its poor wear
resistance .Another way to get the shafting to accurately go down the middle
of the tubing is to just wrap both ends with tape till its a snug fit . After
this is done you can experiment with molding the piston with polyurethane
and by doing this inside the same type of tubing you plan to use , it can
be easily made to fit precisely., perhaps with a composite core to hold the
piston on to the rod and give the piston some strength , or try
whatever else you might think of. It could prove useful to line the inside
surface with aluminum foil so that later when removed would allow the molded
piston to be a little less snug , that is if you plan to mold a solid epoxy
piston and or use seals somehow. Do take a look at some old hydraulic cylinders
to get an idea how they are built. Ends plates could be considered and be
held on by long bolts so that they are easy to repair but it should be noticed
about how a flat plate might be more likely to flex slightly or allow
small leaks to occur and you may decide to build a rim up on
either inside or outside of your cylinder . I t can also help to remember
how pressure tends to force outwards so it is probably always best to put
any seals on the inside against any shafting or outside openings .
You may decide to try putting your seals onto the shaft first and then wrap
your fibers over it all and you also might decide to leave only the
one end so it can be opened for repairs .Sometimes it is possible to file
the ends of tubing and rod to get it reasonable precise by a making a jig
from an end of a precision cut angle rod , placing your rod or tube in it
and using its end to guide your filing .I have herd that composite carbon
fiber hydraulics cylinders weigh considerably less and I think it was 6 times
less but don't quote me on it as I'm not really sure now, hope I can find
the information on this again as someone is selling them for their
weight saving advantages.
4 angle rods can be used as a simple mold that can be adjusted to any dimensions
needed and is often a good way to make to mold , for the silicone molds that
are so useful for making epoxy and fiberglass parts.
A home made set up I often use for quickly saturating lots of fiberglass
strands , is a simple block of lead that I molded myself , having a well
in its middle . The smaller block attached to where the fibers come out is
based on a small block of rubber with a slit in it , is to wipe off much
of the excess resin , I got this from an old washing machine shock absorber
.
I have at least partly finished a universal joint by these methods and can
see other ways to do this but felt it should be included here to give at
least a reasonable start on ideas for you to make your own if you should
need these. Below is a suggestion for creating the yoke or middle piece or
our universal joint , it probably would not need bearings in this piece and
would probably only need to hold short pieces of shafting at right angles
. You would need to wrap its center with fibers and might be a bit difficult
getting in and out of much as would be the case with threading a needle
repeatedly.
The top drawing looks like a washer
and that is what I used , however its a very large one . It dose seam a little
difficult to get the 2 separate shafting to line up exactly, an example
method might be with a few pieces of angle rod or other square pieces that
can be pressed against the two smaller rods so that they are now high enough
to use another straight rod along the top . Of course a carpenters square
or other accurate square can be also used to finish . After using lots of
clay to hold everything in place I just used the middle to wrap a ball of
fiberglass strand to form my spider or middle piece of my universal joint
. The ends and middle of your rods should be greased to aid in removal .
The bottom drawing is a jig to mount the bearings on the spider , the outside
structure for the universal joint . On mine I made the jig by
molding the angled end onto a piece of pipe with epoxy . But getting this
at the proper angle required a lot of different pieces all at once with each
piece having an accurate 90 deg angle and finishing with a small piece
of angle rod to form the angled end for the shafting to lay into . The one
side open where I poured in the epoxy I had to turn it over to mold over
this open end so it would become level on at least one side but you got different
ways of doing this so its probably a waste of time describing them all except
for the need to keep and find various pieces of precision angle rod etc.
that is very common as scrap. Also realized that this piece may be best made
so you can best use washers or strips of metal to widen as needed because
for larger universal joints you will need to place the bearings farther apart
, while you can its still not so easy to mount our bearings closer together
in this jig for smaller universal joints . Extra care may be needed for the
woven part to be easily removed and with the large tubing you may need a
way to reduce . After its done just remove the shafting and put in the spider
and then put back in short pieces of the same shafting and don't forget to
make sure all the bearings and shafting you use in the jigs are all the same
type you intend to use
.
Of course washers and small clamps to hold them in place forming small spools
around your bearings is the same as for weaving gearboxes etc.
These two pieces require pre made models and I do have these made for
my own use and am willing to sell copies fairly cheaply so you can avoid
the inconvenience of making these models yourself to make molds from
or get molds from me but I can only guess at a price
This first drawing shows a lab clamp that I had originally hoped would require
a wax core that could be molded and then melted away after the piece was
finished as a way to demonstrate the idea of using removable wax jigs , this
however seamed not to be necessary . I have had to remake the model a few
times because its easy to forget where you need to provide strength or room
for the fiberglass strands so they will not take away room for the shaft
to be clamped etc. The top shows just the one piece because you need
2 of these glued top to bottom for the clamp . Molding these in 2 half's
also allows easy access to putting in the reinforcement fibers . To finish
it you must wrap your strands over the nut that will hold the screw used
to tighten onto the shaft to be clamped . Use an old piece of tubing or piece
of metal to hold the nut, up and in place . Because composites are
stronger in tension a curved piece being pulled is at a disadvantage so it
may be best to make your clamps so that the fibers go straight to the edges
of your nut or sides of the washer making it so the edges of the washer or
nut are in compression to keep the strand in pure tension . The side
with the high edge to hold the fiber on when weaving has no reinforcement
under it depending of the other half to have its reinforcement to give it
strength . These two pieces are designed to be pulled together when
used so as not to depend on any glue bond for strength If you should
want these ,I speculate that 1.00 would be enough for single epoxy castings
of these so you cam make your own molds and it is the only hard to make part.
This drawing is of a component I am presently using to attach scrap
lawn chair and tv antenna tubing's into shelving and all sorts of tables
and etc. . It dose tend to use a quite a bit of material as you need 8 of
these just for one cube and 4 more for each extra level so its
not long before you use a gallon of resin . Id recommend making a smaller
core in fiberglass that would serve as a skeleton and cut down
on the use of epoxy. using it to mold just the outside surface . On
mine I always provide a screw hole on the flat side , after all what is shelving
without a way to attach widows or etceteras , but 4 holes may in some ways
be better . I did this by greasing a machine screw and placing it over the
hole in its mold with a greased washer so it doesn't fall in . So keep this
in mind when you place your reinforcement or make a skeleton to allow room
for any screw mounts you might want to add later. I have made most of mine
in just plain fiberglass resins but this has the nasty tendency to cause
the silicone molds used to make it in , to distort and fiberglass also tends
to shrink and distort on its own as well , adding even more to the problem
. Despite this I have still gotten quite a few usable connectors made
before the silicone started to distort too much , fortunately the silicone
will recover to at least a modest extent after time . Fiberglass is almost
never as good as epoxy and because its usable it's not necessarily of very
good quality . The original pieces for this were made by filling the ends
of lawn chair tubing placed precisely vertically with just a tinny overflow
hole to keep the depth within reason of what I wanted . The square piece
in the middle was made by a similar way but by using square tubing
and taking my time to cut the unfinished end as square as I could . It might
be preferable to put the less perfect side so that in the finished mold this
end will be where you pour in the resin .
This illustration shows how a 4 part mold could be made , areas shaded in
gray is for clay, and paper or thin cardboard is shown with its ends
curled up to make it more noticeable , but it could just as easily go completely
around . The first part of this process is putting the clay into the places
shown with the paper to hold the silicone mold making material . Later when
the clay is removed and the exposed silicone is covered with a mold release
you can then wrap the whole thing with a strip of paper forming a tube around
the whole thing , then pour in more silicone where the clay was to
give you your 4 part mold that will come apart much more easily than a 2
part mold for this type of a model . Don't worry about the separate parts
of your mold being uneven as it is actually better to have a reasonable amount
of unevenness to assure that the pieces of the mold fit together correctly
and you can consider using pins placed into the clay and become part of the
mold to aid even more. I prefer to make a mold of this type round to
avoid uneven stresses that might distort the mold when I wrap it with elastic
bands to hold it together . The obvious advantage of a 4 part mold for this
type of model , is a mold that you will not need to pull epoxy
castings out of a deep hole , easier if both sides of a such a hole
comes apart. .Should anyone not want to bother making their own original
model , might want to get one of mine to make your mold from. This
part is larger so if I was to sell any models ,expect a price of something
like 5.00 US I am hoping it would be less but would rather error on
the side of asking to much .
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