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Gimbal Project

542 bytes removed, 18:28, 17 January 2012
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made from a 7" long piece of 3/4" EMT that has had two holes and a notch cut in
the bottom.<br/>
<br/>A PDF file of the part drawing is available: [[:filemedia:stick_stub.pdf]] The completed stick
stub should look like this:<br/>
<br/>
[[file:stick_stub.png]]<br/>
<br/>The stick stub is just that - a stub.&nbsp; Your flight grip and lower stick or &quot;stick box&quot; will attach to this using another 3/4&quot; " EMT mating connector.&nbsp;
The stick stub also provides the mechanical interconnect for the roll and pitch
axes.<br/>
<br/>The next part is the roll axis actuator rod.&nbsp; This is just a fancy name
for a 6.75&quot; long bit of 1/4&quot; steel rod that you&#39;ve flatted on one end and
threaded on the other.&nbsp; It looks like this:<br/p> <pbr/><img alt="Roll axis actuator rod" src="[[file:roll_axis_acutator_rod.png" width="640" height="491" />]]<br/p><pbr/><a href="[[medial:roll_axis_actuator_rod.pdf">]]Here</a> is a PDF file that shows the
details of making the rod.&nbsp; The hole is sized for a #10 screw.&nbsp; When
installed, it looks like this:<br/p><pbr/><img alt="roll axis actuator in the installed position" src="[[file:roll_actuator_installed.png" width="640" height="491" />]]<br/p><pbr/>The screw is not shown.&nbsp; The attachment will take bit of experimenting
with to get it centered in the stick stub.&nbsp; You want a #10 screw that&#39;s
about 1-1/4&quot; long&nbsp; You&#39;ll use a &quot;stop-nut&quot; which is basically a regular nut
tighten the screw down enough to take the slop out, but not enough to bind up
the mechanism.&nbsp; Stop-nuts allow this - the nylon ring ensures that they
won&#39;t loosen over time.<br/p> <pbr/><img alt="Roll axis pushrod connection detail" src="[[file:roll_axis_pushrod_connection.jpg" width="640" height="426" />]]<br/p><pbr/>To center the rod in the stick stub, you&#39;ll need to get two #10 nylon washers
and a few #10 zinc washers.&nbsp; Place the nylon washers on the &quot;outside&quot; of
the stack.&nbsp; They&#39;ll be the washers that will rub on the inside of the stick
rubbing against the inside wall of the stick stub.&nbsp; Take the metal washers
and stack them on either side of the rod until you&#39;ve got the right number on
each side that gives the closest to center fit.<br/p>
<pbr/>The clevis fork is made by taking a 1/4&quot; extruded aluminum turnbuckle and
cutting off the left-hand threaded end.&nbsp; You then drill a hole that&#39;s the
appropriate size for the bolt you&#39;re going to use.&nbsp; In my case the holes
were drilled for 1/4&quot; and #10 bolts (not on the same clevis).<br/p><pbr/><img alt="Clevis fork made from a turnbuckle" src="[[file:clevis_fork.png" width="640" height="426" />]]<br/p><pbr/>Next up, making the wooden bearing blocks for the gimbal...<br/p><pbr/>First, you&#39;re going to need to download the drawing for the bearing parts.<br/p>
<pbr/><a href="[[media:pitch%20axis%20bearing%20drawing.dxf">]] pitch axis bearing drawing.dxf</a>
- This drawing was saved in AutoCAD 2004 DXF format.&nbsp; You shouldn&#39;t have
any problems reading it using any of the freely available CAD programs, you can
download a PDF of the plan<a target="_blank" href="[[media:pitch%20axis%20bearing%20drawing.pdf">here]]<br/a>.&nbsp; The drawing will print full size on a single 11x17 sheet.&nbsp; <br/p><pbr/>The blocks are made from 5/8&quot; Birch plywood.&nbsp; However, any good quality 5/8&quot; (or close) plywood will work.<br/p>
<pbr/>Please take your time cutting out the bearing blocks.&nbsp; <br/p><pbr/>Here are some recommendations that should help you get a more accurate result:<br/p><ulbr/> <li>* When drilling the three mounting holes in the bearing base, it would be
a good idea to drill both parts at the same time to ensure that the holes
are placed identically in both parts.&nbsp; The bearings must be square and
aligned to one another or the pitch axis bearing shaft will bind.</li> <li>* When creating the parts with the bearing holes in them, it is far safer
and more accurate to drill all the small holes and the two large holes&nbsp;
<em>before </em>you cut the parts to shape.&nbsp; Trust me, you don&#39;t want
to be boring a near 1&quot; diameter hole in a part with nearly no material to
hang on to while the drill does its job. :)</li>
<li>* The large bearing holes are specified at .95&quot;.&nbsp; The easiest way to
reach that size is to use a 7/8&quot; Forstner or Spade bit.&nbsp; This will get
you to .875&quot;&nbsp; The remainder can be sanded away with a small drum sander
to the point where they&#39;re just a little bit loose around the 3/4&quot; EMT
conduit that makes up the pitch axis bearing.&nbsp; Make sure that when
you&#39;re sanding the parts to shape, you do them in assembled pairs.</li>
<li>* If you&#39;d rather not sand the holes to size, you can still get good
results by boring a 1&quot; diameter hole instead of a .95&quot; hole.&nbsp; The fit
will only be a tiny bit looser than what I&#39;ve specified and it won&#39;t affect
how the gimbal operates.</li></ul><p>Here is an exploded illustration that shows you how the pitch axis bearings are assembled:</p><p><img alt="Exploded illustraition of the Pitch Axis Bearing" src="pab_exploded.jpg" width="677" height="486" /></p>
<pbr/>Here is an exploded illustration that shows you how the pitch axis bearings are assembled:<br/><br/>[[file:pab_exploded.jpg]]<br/> <br/>The bearing is assembled using three 1-3/4&quot; #10 pan head screws and three #10
nylon ringed stop-nuts.&nbsp; It&#39;s important that you don&#39;t use any washers on
this because the washers will actually rub on the bearing shaft when it&#39;s
your bearing block layout, you&#39;ll also want to mark out the space needed to
allow the gimbal box to protrude up through the cockpit floor.&nbsp; In my
version I&#39;m using a hole that&#39;s 5-1/2&quot; wide and 5-1/4&quot; high.<br/p>
<pbr/>You&#39;ll now want to make the pitch axis bearings.&nbsp; They consist of two
short lengths of 3/4&quot; EMT conduit cut to a length that will allow them to fully
seat in the EMT mating connectors on the gimbal box and extend at least two
inches on the pitch actuator side and about 1/2&quot; on the roll axis actuator side.&nbsp;
Below are examples that show you roughly how it should look.<br/p><pbr/>Pitch axis connection end:<br/p><pbr/><img src="[[file:pitch_axis_bearing_detail.jpg" width="640" height="426" />]]<br/p><pbr/>You&#39;ll note here how the centering rod for the pitch axis is mounted to the
bearing.&nbsp; I&#39;m using a #8 eye bolt that has a locknut on both sides to hold
it in place.&nbsp; I chose a #8 because the eye is perfectly sized for a 1/4&quot;
chose are threaded and have a long enough reach for them to be able to pass
through the side of the clevis fork.&nbsp; You can see the nut for the ball on
the inside.<br/p><pbr/>Roll axis connection end:<br/p><pbr/><img src="[[file:roll_axis_pushrod_and_center_interconnect.jpg" width="640" height="426" />]]<br/p><pbr/>Here you can see why the roll axis side of the pitch axis bearing needs to be
so short.&nbsp; When you move the stick to the far left, the back end of the
clevis fork can&#39;t come in contact with the bearing tube.<br/p>
<pbr/>You can also see the roll axis potentiometer connection.&nbsp; Just like on
the pitch axis, I&#39;m using a Du-Bro ball-link on the clevis end, and a Du-Bro E/Z
Connector on the potentiometer end.&nbsp; This is a very simple and very
reliable way to connect your axis pots to your stick gimbal.<br/p><pbr/>The last component I&#39;m going to cover is the centering mechanism.<br/p><pbr/>The centering mech is very simple.&nbsp; It consists of a 1/4&quot; steel rod
that&#39;s been threaded on one end, a clevis fork made from a turnbuckle, a pair of
springs and some locking collars.<br/p>
<pbr/>In my design the steel rod is 10&quot; long.&nbsp; Your application may and probably will vary.&nbsp; Here&#39;s a picture of the assembly:<br/p><pbr/><img alt="Roll axis centering mechanism and pot connection" src="[[file:roll_axis_centering_and_pot.jpg" width="640" height="426" />]]<br/p><pbr/>As you can see, the whole thing is very simple.&nbsp; A 1x1 L bracket is
bolted in place and has a 5/16&quot; hole to allow the rod to pass through it.&nbsp;
A collar on either end holds the spring in place.&nbsp; The springs are
compressed against the center bracket just slightly.&nbsp; This provides good
centering force for the gimbal. <br/p><pbr/>One option you may want to consider is using two spring pairs.&nbsp; If you
stack a lighter spring atop a heavier spring, your gimbal will have light force
around the center and it will increase as you move the controls.&nbsp; This
happens because small movements around the center only compress the light
spring, while movements toward the travel ranges compresses both the light and
heavy springs.<br/p><pbr/>That&#39;s really all there is to it!&nbsp; Below you&#39;ll find various pictures of
the assembly that will help out in building your own.&nbsp; If you&#39;ve got
questions please feel free to join the
<a href="http://www.simpits.org/mailman/listinfo/simpits-tech">simpits-tech</a>
mailing list!<br/p><p><img alt="Misc. Pictures" src="[[file:roll_axis_pushrod_and_center_interconnect-2.jpg">]]<br/p><pbr/><img src="[[file:pitch_axis_pushrod_and_pot.jpg">]]<br/p><pbr/><img src="[[file:pitch_axis_pushrod_and_pot-2.jpg">]]<br/p><pbr/><img src="[[file:pitch_axis_bearing_detail.jpg">]]<br/p><pbr/><img src="[[file:pitch_axis_bearing_detail-2.jpg">]]<br/p><pbr/><img src="[[file:gimbal_box_detail.jpg">]]<br/p><pbr/><img src="[[file:roll_axis_pushrod_connection-2.jpg"></p><p>&nbsp;]]<br/p>
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