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[[Category:Hardware|Gimbal Build a simple pitch & roll gimbal]]
Back in May 2009 I had spent some time tossing ideas back and forth with a nice gent by the name of Jentron on the #flightgear [[IRC|IRC channel]] (irc.flightgear.org). We were discussing the various methods that could be used to create a very inexpensive gimbal assembly for pitch & roll control in a home built flight simulator [[cockpit]].
[[Category:Howto|Gimbal Build a simple pitch & roll gimbal]]
 
This is what Jentron developed:
 
[[File:jentron_original.jpg|400px]]
 
As you can see, it's very simple and uses easily obtainable off the shelf hardware. In fact, this particular example was built entirely from the resources of his local Ace Hardware.
 
I've named his original gimbal design the "Mark I" to differentiate it from the design I'm using - but they're both built from essentially the same components.
 
Here is what I call the Jentron Gimbal, Mk II:
 
[[File:jentron_mk2-1.jpg|400px]]
 
As you can see, the design elements from the Mk I design are present here with a couple notable changes:
* The pitch axis bearings are two separate components.
* Simpler interconnect for the pitch axis centering arm - no need for a hand-fabricated pitch arm.
* Reduced part count
 
Jentron's design is perfectly usable in it's configuration, but I needed to modify it for use with the DIY Cockpit Project.<br>Besides, I'm a geek and no self respecting geek can resist fiddling with things. :)
 
Below is instructions on how you can construct this gimbal for use in your cockpit!
 
== Building instructions ==
 
Here's information on how my version of the Jentron Gimbal Mk II was built and how you can build your own.
 
One important thing to note - the gimbal is designed to be mounted underneath the cockpit floor. This is what it looks like from above, in the "operating" position:
 
[[file:jentron_mk2-3.jpg|400px]]
 
This article will only cover the ins and outs of the gimbal itself. The reason for this is that your application may be a bit different and you'll need to adjust other parts of the design to fit your situation.
 
Two "fancy" tools are going to be required to build this project.
* 1 Step Drill. This is used to enlarge the end holes in the single-gang extender box.
* 1/4" Die. This is used for threading the ends of the centering push-rods.
 
A cheap 1" Step Drill can be had for less than $30. In case you're not sure, a step drill looks like this:
 
[[file:step_drill.jpg]]
 
Here's a list of some other common tools you're going to need:
* Hacksaw -or- a pipe cutter. Pipe cutters work better for cutting EMT.
* Drill
* Drill Bits - 1/4" and 13/64"
* Pop-Rivet gun
* Jig Saw, Band Saw or a Scroll Saw
* Two 7/16" open end wrenches
* 3/8" open end wrench
* Philips screwdriver
* Vice Grips (2 pair if you can)
* Vice or vice-like device
 
Materials needed to build the gimbal box:
* 1 each single-gang electrical extension box
[[file:single-gang_box.jpg]]
* 2 each 3/4" EMT connectors
[[file:emt_connector.jpg]]
* 2 each 3" "T" Brackets
[[file:t-bracket.jpg]]
* 4 each 3/16" Pop-Rivets
[[file:pop-rivet.jpg]]
 
Now the first thing you're going to need to do is pop out all the knock-outs in the electrical box and then drill out the ends using the 1" Step Drill. The hole needs to be large enough to accept the threaded portion of the 3/4" EMT connector. When you're done, the box should look like this:
 
[[file:prepped_box.jpg]]
 
Next up, you're going to have to use your vice grips (2 pair if you have them!) to position the 3" "T" bracket on the side of the extension box. The best way to do this is to measure 1-1/2" in from the end of the "top" of the T brace and draw a centering line. Measure the electrical box along its long axis and mark the center of it. The centering lines ensure that you'll correctly position the "T" bracket on the side of the box.
 
Position the box and T-Bracket like this:
 
[[file:t-bracket_position.jpg]]
 
With the vice grip(s) holding the t-bracket in place, put the box in a vice to hold it down. You're going to use a 1/4" drill bit to drill holes in the extension box, using the bracket as a guide. Do this for both brackets. When you've got all four holes drilled, go ahead and pop-rivet them in place - please be careful to make sure that both brackets are lined up with one another. The portion of the bracket that sticks out will be the support for the stick stub. It's got to be as close perfect as you can make it. In the end, you should have something that looks like this:
 
[[file:both_brackets_mounted.jpg]]
 
You'll notice in my drawing that I'm using screws to hold the brackets in. This was done because I didn't want to take the time to draw a reasonable looking pop rivet. :)
 
The last step is to mount the 3/4" EMT fittings. These hold 3" sections of 3/4" EMT conduit that act as the pitch bearings for the box. It's important to get these as tight as you can. They'll take all the force of the stick moving fore and aft. I recommend using a pair of Channel-Lock pliers and a vice to make sure those fittings are as tight as you can make them.
 
If you're paranoid and have a welder, it couldn't hurt it to weld them in place.
 
With it all assembled, it should look like this:
 
[[file:complete_gimbal_box.jpg]]
 
I didn't include the nuts that go to the EMT connectors on purpose. They MUST be used. :)
 
Here's an exploded diagram that shows you how it all goes together:
 
[[file:gimbal_box_exploded.jpg]]
 
The last part of this assembly is the stick stub. The stick stub is made from a 7" long piece of 3/4" EMT that has had two holes and a notch cut in the bottom. A PDF file of the part drawing is available: [[media:stick_stub.pdf]]
 
The completed stick stub should look like this:
 
[[file:stick_stub.png|400px]]
 
The stick stub is just that - a stub. Your flight grip and lower stick or "stick box" will attach to this using another 3/4" EMT mating connector. The stick stub also provides the mechanical interconnect for the roll and pitch axes.


<p>Back in May 2009 I had spent some time tossing ideas back and forth with a nice
The next part is the roll axis actuator rod. This is just a fancy name for a 6.75" long bit of 1/4" steel rod that you've flatted on one end and threaded on the other. It looks like this:
gent by the name of Jentron on the #flightgear IRC channel (<a href="irc://irc.flightgear.org">irc.flightgear.org</a>).&nbsp;
We were discussing the various methods that could be used to create a very
inexpensive gimbal assembly for pitch &amp; roll control in a home built flight
simulator cockpit.


This is what Jentron developed:
[[file:roll_axis_acutator_rod.png|400px]]


[[file:jentron_original.jpg]]
[[medial:roll_axis_actuator_rod.pdf]]Here is a PDF file that shows the details of making the rod. The hole is sized for a #10 screw. When installed, it looks like this:
<p>
As you can see, it&#39;s very simple and uses easily obtainable off the shelf
hardware.&nbsp; In fact, this particular example was built entirely from the
resources of his local Ace Hardware.


<p>I&#39;ve named his original gimbal design the &quot;Mark I&quot; to differentiate it from
[[file:roll_actuator_installed.png|400px]]
the design I&#39;m using - but they&#39;re both built from essentially the same
components.</p>
<p>Here is what I call the Jentron Gimbal, Mk II:</p>
<p>
<img alt="Jentron Gimbal, Mark II" src="jentron_mk2-1.jpg" width="640" height="426" /></p>
<p>As you can see, the design elements from the Mk I design are present here
with a couple notable changes.</p>
<ul>
<li>The pitch axis bearings are two separate components.</li>


<li>Simpler interconnect for the pitch axis centering arm - no need for a  
The screw is not shown. The attachment will take bit of experimenting with to get it centered in the stick stub. You want a #10 screw that's about 1-1/4" long You'll use a "stop-nut" which is basically a regular nut with a nylon ring pressed into the top. The idea is to allow you to tighten the screw down enough to take the slop out, but not enough to bind up the mechanism. Stop-nuts allow this - the nylon ring ensures that they won't loosen over time.
hand-fabricated pitch arm.</li>
<li>Reduced part count</li>
</ul>
<p>Jentron&#39;s design is perfectly usable in it&#39;s configuration, but I needed
to modify it for use with the DIY Cockpit Project.<br>Besides, I&#39;m a geek and
no self respecting geek can resist fiddling with things. :)</p>
<p>Below is instructions on how you can construct this gimbal for use in your
cockpit!</p>


<p>&nbsp;</p>
[[file:roll_axis_pushrod_connection.jpg|400px]]


<hr>
To center the rod in the stick stub, you'll need to get two #10 nylon washers and a few #10 zinc washers. Place the nylon washers on the "outside" of the stack. They'll be the washers that will rub on the inside of the stick stub. The nylon won't produce the noise that a metal washer would when rubbing against the inside wall of the stick stub. Take the metal washers and stack them on either side of the rod until you've got the right number on each side that gives the closest to center fit.
Here&#39;s information on how my version of the Jentron Gimbal Mk II was built
and how you can build your own.</p>


<p>One important thing to note - the gimbal is designed to be mounted underneath
The clevis fork is made by taking a 1/4" extruded aluminum turnbuckle and cutting off the left-hand threaded end. You then drill a hole that's the appropriate size for the bolt you're going to use. In my case the holes were drilled for 1/4" and #10 bolts (not on the same clevis).
the cockpit floor.&nbsp; This is what it looks like from above, in the
&quot;operating&quot; position:</p>
<p>
<img alt="Jentron Gimbal Mk2 - Operating Position" src="jentron_mk2-3.jpg" width="640" height="426" /></p>
<p>&nbsp;</p>
<p>This article will only cover the ins and outs of the gimbal itself.&nbsp; The
reason for this is that your application may be a bit different and you&#39;ll need
to adjust other parts of the design to fit your situation.</p>


<p>Two &quot;fancy&quot; tools are going to be required to build this project.&nbsp; </p>
[[file:clevis_fork.png|400px]]
<ul>
<li>1&quot; Step Drill.&nbsp; This is used to enlarge the end holes in the
single-gang extender box.</li>
<li>1/4&quot; Die.&nbsp; This is used for threading the ends of the centering
pushrods</li>


</ul>
Next up, making the wooden bearing blocks for the gimbal... First, you're going to need to download the drawing for the bearing parts.
<p>A cheap 1&quot; Step Drill can be had for less than $30.&nbsp; In case you&#39;re not
sure, a step drill looks like this:</p>
<p>
<img alt="Representative example of a Step Drill" src="step_drill.jpg" width="127" height="95" /></p>
<p>Here&#39;s a list of some other common tools you&#39;re going to need:</p>
<ul>
<li>Hacksaw -or- a pipe cutter.&nbsp; Pipe cutters work better for cutting
EMT.</li>


<li>Drill </li>
[[media:pitch%20axis%20bearing%20drawing.dxf]] pitch axis bearing drawing.dxf
<li>Drill Bits - 1/4&quot; and 13/64&quot;</li>
<li>Pop-Rivet gun</li>
<li>Jig Saw, Band Saw or a Scroll Saw</li>
<li>Two 7/16&quot; open end wrenches</li>


<li>3/8&quot; open end wrench</li>
- This drawing was saved in AutoCAD 2004 DXF format. You shouldn't have any problems reading it using any of the freely available CAD programs, you can download a PDF of the plan [[media:pitch%20axis%20bearing%20drawing.pdf]]. The drawing will print full size on a single 11x17 sheet. The blocks are made from 5/8" Birch plywood. However, any good quality 5/8" (or close) plywood will work.
<li>Philips screwdriver</li>
<li>Vice Grips (2 pair if you can)</li>
<li>Vice or vice-like device</li>
</ul>
<p>Materials needed to build the gimbal box:</p>


<table style="width: 65%">
Please take your time cutting out the bearing blocks. Here are some recommendations that should help you get a more accurate
<tr>
result:
<td style="width: 202px">1ea single-gang electrical extension box</td>
<td>
<img alt="Single-Gang Extention Box" src="single-gang_box.jpg" width="200" height="133" /></td>
</tr>
<tr>
<td style="width: 202px">2ea 3/4&quot; EMT connectors</td>


<td>
* 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. The bearings must be square and aligned to one another or the pitch axis bearing shaft will bind.
<img alt="3/4&quot; EMT Connector" src="emt_connector.jpg" width="200" height="133" /></td>
* 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<em>before </em>you cut the parts to shape. Trust me, you don't want to be boring a near 1" diameter hole in a part with nearly no material to hang on to while the drill does its job. :)
</tr>
* The large bearing holes are specified at .95". The easiest way to reach that size is to use a 7/8" Forstner or Spade bit. This will get you to .875" The remainder can be sanded away with a small drum sander in a drill or a drill press. The idea is to get the size of the holes to the point where they're just a little bit loose around the 3/4" EMT conduit that makes up the pitch axis bearing. Make sure that when you're sanding the parts to shape, you do them in assembled pairs.
<tr>
* If you'd rather not sand the holes to size, you can still get good results by boring a 1" diameter hole instead of a .95" hole. The fit will only be a tiny bit looser than what I've specified and it won't affect how the gimbal operates.
<td style="width: 202px">2ea 3&quot; &quot;T&quot; Brackets</td>
<td>


<img alt="3&quot; T-Bracket" src="t-bracket.jpg" width="200" height="133" /></td>
Here is an exploded illustration that shows you how the pitch axis bearings are assembled:
</tr>
<tr>
<td style="width: 202px"><br />
4ea 3/16&quot; Pop-Rivets</td>
<td>
<img alt="3/16&quot; Pop-Rivets" src="pop-rivet.jpg" width="200" height="200" /></td>


</tr>
[[file:pab_exploded.jpg|400px]]
</table>
<p>Now the first thing you&#39;re going to need to do is pop out all the knock-outs
in the electrical box and then drill out the ends using the 1&quot; Step Drill.&nbsp;
The hole needs to be large enough to accept the threaded portion of the 3/4&quot; EMT
connector.&nbsp; When you&#39;re done, the box should look like this:</p>
<p>
<img alt="Prepped gimbal box" src="prepped_box.jpg" width="400" height="307" /></p>


<p>Next up, you&#39;re going to have to use your vice grips (2 pair if you have
The bearing is assembled using three 1-3/4" #10 pan head screws and three #10 nylon ringed stop-nuts. It's important that you don't use any washers on this because the washers will actually rub on the bearing shaft when it's installed. The base is attached using two 1-1/2" #8 flat head wood screws. You should countersink the holes for them as shown in the model above.
them!) to position the 3&quot; &quot;T&quot; bracket on the side of the extension box.&nbsp;
The best way to do this is to measure 1-1/2&quot; in from the end of the &quot;top&quot; of the
T brace and draw a centering line.&nbsp; Measure the electrical box along its
long axis and mark the center of it.&nbsp; The centering lines ensure that
you&#39;ll correctly position the &quot;T&quot; bracket on the side of the box.</p>


<p>Position the box and T-Bracket like this:</p>
Now that you've got the bearing blocks made, you're going to need to lay out the position of them on the base plate. This spacing will vary, but generally a distance of about 6-1/4" should be sufficient. When you do your bearing block layout, you'll also want to mark out the space needed to allow the gimbal box to protrude up through the cockpit floor. In my version I'm using a hole that's 5-1/2" wide and 5-1/4" high.
<p>
<img alt="Illustration showing the correct placement of the T-Bracket" src="t-bracket_position.jpg" width="400" height="307" /></p>
<p>With the vice grip(s) holding the t-bracket in place, put the box in a vice
to hold it down.&nbsp; You&#39;re going to use a 1/4&quot; drill bit to drill holes in
the extension box, using the bracket as a guide.&nbsp; Do this for both
brackets.&nbsp; When you&#39;ve got all four holes drilled, go ahead and pop-rivet
them in place - please be careful to make sure that both brackets are lined up
with one another.&nbsp; The portion of the bracket that sticks out will be the  
support for the stick stub.&nbsp; It&#39;s got to be as close perfect as you can
make it.&nbsp; In the end, you should have something that looks like this:</p>


<p>
You'll now want to make the pitch axis bearings. They consist of two short lengths of 3/4" 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" on the roll axis actuator side. Below are examples that show you roughly how it should look. Pitch axis connection end:
<img alt="Illustration showing both &quot;T&quot; brackets in place" src="both_brackets_mounted.jpg" width="400" height="307" /></p>
<p>You&#39;ll notice in my drawing that I&#39;m using screws to hold the brackets in.&nbsp;
This was done because I didn&#39;t want to take the time to draw a reasonable
looking pop rivet. :)</p>
<p>The last step is to mount the 3/4&quot; EMT fittings.&nbsp; These hold 3&quot; sections
of 3/4&quot; EMT conduit that act as the pitch bearings for the box.&nbsp; It&#39;s
important to get these as tight as you can.&nbsp; They&#39;ll take all the force of
the stick moving fore and aft.&nbsp; I recommend using a pair of Channel-Lock
pliers and a vice to make sure those fittings are as tight as you can make them.&nbsp;


If you&#39;re paranoid and have a welder, it couldn&#39;t hurt it to weld them in place.&nbsp;
[[file:pitch_axis_bearing_detail.jpg|400px]]
With it all assembled, it should look like this:</p>
<p>
<img alt="Completed gimbal box" src="complete_gimbal_box.jpg" width="400" height="307" /></p>
<p>I didn&#39;t include the nuts that go to the EMT connectors on purpose.&nbsp;
They MUST be used. :)</p>
<p>Here&#39;s an exploded diagram that shows you how it all goes together:</p>
<p>


<img alt="Exploded illustration of the gimbal box" src="gimbal_box_exploded.jpg" width="400" height="307" /></p>
You'll note here how the centering rod for the pitch axis is mounted to the bearing. I'm using a #8 eye bolt that has a locknut on both sides to hold it in place. I chose a #8 because the eye is perfectly sized for a 1/4" bolt. You can also just barely see the Du-Bro ball-link that I'm using to connect the pitch axis to the potentiometer that connects to the computer. The ball-links are very inexpensive and very handy to use. The ones I chose are threaded and have a long enough reach for them to be able to pass through the side of the clevis fork. You can see the nut for the ball on the inside.
<p>The last part of this assembly is the stick stub.&nbsp; The stick stub is
made from a 7&quot; long piece of 3/4&quot; EMT that has had two holes and a notch cut in  
the bottom.</p>
<p>A PDF file of the part drawing is available
<a target="_blank" href="stick_stub.pdf">here</a>.&nbsp; The completed stick
stub should look like this:</p>
<p>
<img alt="Completed stick stub" src="stick_stub.png" width="640" height="491" /></p>


<p>The stick stub is just that - a stub.&nbsp; Your flight grip and lower stick
Roll axis connection end:
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.</p>
<p>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:</p>


<p>
[[file:roll_axis_pushrod_and_center_interconnect.jpg|400px]]
<img alt="Roll axis actuator rod" src="roll_axis_acutator_rod.png" width="640" height="491" /></p>
<p><a href="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:</p>
<p>
<img alt="roll axis actuator in the installed position" src="roll_actuator_installed.png" width="640" height="491" /></p>
<p>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
with a nylon ring pressed into the top.&nbsp; The idea is to allow you to
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.</p>


<p>
Here you can see why the roll axis side of the pitch axis bearing needs to be so short. When you move the stick to the far left, the back end of the clevis fork can't come in contact with the bearing tube.
<img alt="Roll axis pushrod connection detail" src="roll_axis_pushrod_connection.jpg" width="640" height="426" /></p>
<p>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  
stub.&nbsp; The nylon won&#39;t produce the noise that a metal washer would when
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.</p>


<p>The clevis fork is made by taking a 1/4&quot; extruded aluminum turnbuckle and
You can also see the roll axis potentiometer connection. Just like on the pitch axis, I'm using a Du-Bro ball-link on the clevis end, and a Du-Bro E/Z Connector on the potentiometer end. This is a very simple and very reliable way to connect your axis pots to your stick gimbal. The last component I'm going to cover is the centering mechanism. The centering mech is very simple. It consists of a 1/4" steel rod that's been threaded on one end, a clevis fork made from a turnbuckle, a pair of springs and some locking collars.
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).</p>
<p>
<img alt="Clevis fork made from a turnbuckle" src="clevis_fork.png" width="640" height="426" /></p>
<p>Next up, making the wooden bearing blocks for the gimbal...</p>
<p>First, you&#39;re going to need to download the drawing for the bearing parts.</p>


<p><a href="pitch%20axis%20bearing%20drawing.dxf">pitch axis bearing drawing.dxf</a>
In my design the steel rod is 10" long. Your application may and probably will vary. Here's a picture of the assembly:
- 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="pitch%20axis%20bearing%20drawing.pdf">here</a>.&nbsp;
The drawing will print full size on a single 11x17 sheet.&nbsp; </p>
<p>The blocks are made from 5/8&quot; Birch plywood.&nbsp; However, any good quality
5/8&quot; (or close) plywood will work.</p>


<p>Please take your time cutting out the bearing blocks.&nbsp; </p>
[[file:roll_axis_centering_and_pot.jpg|400px]]
<p>Here are some recommendations that should help you get a more accurate
result:</p>
<ul>
<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
As you can see, the whole thing is very simple. A 1x1 L bracket is bolted in place and has a 5/16" hole to allow the rod to pass through it.  
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
in a drill or a drill press.&nbsp; The idea is to get the size of the holes
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
A collar on either end holds the spring in place. The springs are compressed against the center bracket just slightly. This provides good centering force for the gimbal.
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>


<p>The bearing is assembled using three 1-3/4&quot; #10 pan head screws and three #10
One option you may want to consider is using two spring pairs. 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. 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.
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
installed.&nbsp; The base is attached using two 1-1/2&quot; #8 flat head wood screws.&nbsp;
You should countersink the holes for them as shown in the model above.</p>
<p>Now that you&#39;ve got the bearing blocks made, you&#39;re going to need to lay out
the position of them on the base plate.&nbsp; This spacing will vary, but
generally a distance of about 6-1/4&quot; should be sufficient.&nbsp; When you do
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.</p>


<p>You&#39;ll now want to make the pitch axis bearings.&nbsp; They consist of two
That's really all there is to it! Below you'll find various pictures of the assembly that will help out in building your own.  
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.</p>
<p>Pitch axis connection end:</p>
<p><img src="pitch_axis_bearing_detail.jpg" width="640" height="426" /></p>
<p>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;


bolt.&nbsp; You can also just barely see the Du-Bro ball-link that I&#39;m using to
[[file:roll_axis_pushrod_and_center_interconnect-2.jpg|400px]] [[file:pitch_axis_pushrod_and_pot.jpg|400px]]
connect the pitch axis to the potentiometer that connects to the computer.&nbsp;
The ball-links are very inexpensive and very handy to use.&nbsp; The ones I
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.</p>
<p>Roll axis connection end:</p>
<p>
<img src="roll_axis_pushrod_and_center_interconnect.jpg" width="640" height="426" /></p>
<p>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.</p>


<p>You can also see the roll axis potentiometer connection.&nbsp; Just like on
[[file:pitch_axis_pushrod_and_pot-2.jpg|400px]] [[file:pitch_axis_bearing_detail.jpg|400px]]
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.</p>
<p>The last component I&#39;m going to cover is the centering mechanism.</p>
<p>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.</p>


<p>In my design the steel rod is 10&quot; long.&nbsp; Your application may and
[[file:pitch_axis_bearing_detail-2.jpg|400px]] [[file:gimbal_box_detail.jpg|400px]]
probably will vary.&nbsp; Here&#39;s a picture of the assembly:</p>
<p>
<img alt="Roll axis centering mechanism and pot connection" src="roll_axis_centering_and_pot.jpg" width="640" height="426" /></p>
<p>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
[[file:roll_axis_pushrod_connection-2.jpg|400px]]
compressed against the center bracket just slightly.&nbsp; This provides good
centering force for the gimbal. </p>
<p>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.</p>
<p>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>
[[Category:Hardware|Gimbal Build a simple pitch & roll gimbal]]
mailing list!</p>
[[Category:Howto|Gimbal Build a simple pitch & roll gimbal]]
<p>
[[Category:Joysticks and Yokes]]
<img alt="Misc. Pictures" src="roll_axis_pushrod_and_center_interconnect-2.jpg"></p>
<p><img src="pitch_axis_pushrod_and_pot.jpg"></p>
<p><img src="pitch_axis_pushrod_and_pot-2.jpg"></p>
<p><img src="pitch_axis_bearing_detail.jpg"></p>
<p><img src="pitch_axis_bearing_detail-2.jpg"></p>
<p><img src="gimbal_box_detail.jpg"></p>
<p><img src="roll_axis_pushrod_connection-2.jpg"></p>
<p>&nbsp;</p>

Revision as of 12:26, 29 July 2016

Back in May 2009 I had spent some time tossing ideas back and forth with a nice gent by the name of Jentron on the #flightgear IRC channel (irc.flightgear.org). We were discussing the various methods that could be used to create a very inexpensive gimbal assembly for pitch & roll control in a home built flight simulator cockpit.

This is what Jentron developed:

Jentron original.jpg

As you can see, it's very simple and uses easily obtainable off the shelf hardware. In fact, this particular example was built entirely from the resources of his local Ace Hardware.

I've named his original gimbal design the "Mark I" to differentiate it from the design I'm using - but they're both built from essentially the same components.

Here is what I call the Jentron Gimbal, Mk II:

Jentron mk2-1.jpg

As you can see, the design elements from the Mk I design are present here with a couple notable changes:

  • The pitch axis bearings are two separate components.
  • Simpler interconnect for the pitch axis centering arm - no need for a hand-fabricated pitch arm.
  • Reduced part count

Jentron's design is perfectly usable in it's configuration, but I needed to modify it for use with the DIY Cockpit Project.
Besides, I'm a geek and no self respecting geek can resist fiddling with things. :)

Below is instructions on how you can construct this gimbal for use in your cockpit!

Building instructions

Here's information on how my version of the Jentron Gimbal Mk II was built and how you can build your own.

One important thing to note - the gimbal is designed to be mounted underneath the cockpit floor. This is what it looks like from above, in the "operating" position:

Jentron mk2-3.jpg

This article will only cover the ins and outs of the gimbal itself. The reason for this is that your application may be a bit different and you'll need to adjust other parts of the design to fit your situation.

Two "fancy" tools are going to be required to build this project.

  • 1 Step Drill. This is used to enlarge the end holes in the single-gang extender box.
  • 1/4" Die. This is used for threading the ends of the centering push-rods.

A cheap 1" Step Drill can be had for less than $30. In case you're not sure, a step drill looks like this:

Step drill.jpg

Here's a list of some other common tools you're going to need:

  • Hacksaw -or- a pipe cutter. Pipe cutters work better for cutting EMT.
  • Drill
  • Drill Bits - 1/4" and 13/64"
  • Pop-Rivet gun
  • Jig Saw, Band Saw or a Scroll Saw
  • Two 7/16" open end wrenches
  • 3/8" open end wrench
  • Philips screwdriver
  • Vice Grips (2 pair if you can)
  • Vice or vice-like device

Materials needed to build the gimbal box:

  • 1 each single-gang electrical extension box

Single-gang box.jpg

  • 2 each 3/4" EMT connectors

Emt connector.jpg

  • 2 each 3" "T" Brackets

T-bracket.jpg

  • 4 each 3/16" Pop-Rivets

Pop-rivet.jpg

Now the first thing you're going to need to do is pop out all the knock-outs in the electrical box and then drill out the ends using the 1" Step Drill. The hole needs to be large enough to accept the threaded portion of the 3/4" EMT connector. When you're done, the box should look like this:

Prepped box.jpg

Next up, you're going to have to use your vice grips (2 pair if you have them!) to position the 3" "T" bracket on the side of the extension box. The best way to do this is to measure 1-1/2" in from the end of the "top" of the T brace and draw a centering line. Measure the electrical box along its long axis and mark the center of it. The centering lines ensure that you'll correctly position the "T" bracket on the side of the box.

Position the box and T-Bracket like this:

T-bracket position.jpg

With the vice grip(s) holding the t-bracket in place, put the box in a vice to hold it down. You're going to use a 1/4" drill bit to drill holes in the extension box, using the bracket as a guide. Do this for both brackets. When you've got all four holes drilled, go ahead and pop-rivet them in place - please be careful to make sure that both brackets are lined up with one another. The portion of the bracket that sticks out will be the support for the stick stub. It's got to be as close perfect as you can make it. In the end, you should have something that looks like this:

Both brackets mounted.jpg

You'll notice in my drawing that I'm using screws to hold the brackets in. This was done because I didn't want to take the time to draw a reasonable looking pop rivet. :)

The last step is to mount the 3/4" EMT fittings. These hold 3" sections of 3/4" EMT conduit that act as the pitch bearings for the box. It's important to get these as tight as you can. They'll take all the force of the stick moving fore and aft. I recommend using a pair of Channel-Lock pliers and a vice to make sure those fittings are as tight as you can make them.

If you're paranoid and have a welder, it couldn't hurt it to weld them in place.

With it all assembled, it should look like this:

Complete gimbal box.jpg

I didn't include the nuts that go to the EMT connectors on purpose. They MUST be used. :)

Here's an exploded diagram that shows you how it all goes together:

Gimbal box exploded.jpg

The last part of this assembly is the stick stub. The stick stub is made from a 7" long piece of 3/4" EMT that has had two holes and a notch cut in the bottom. A PDF file of the part drawing is available: media:stick_stub.pdf

The completed stick stub should look like this:

Stick stub.png

The stick stub is just that - a stub. Your flight grip and lower stick or "stick box" will attach to this using another 3/4" EMT mating connector. The stick stub also provides the mechanical interconnect for the roll and pitch axes.

The next part is the roll axis actuator rod. This is just a fancy name for a 6.75" long bit of 1/4" steel rod that you've flatted on one end and threaded on the other. It looks like this:

Roll axis acutator rod.png

medial:roll_axis_actuator_rod.pdfHere is a PDF file that shows the details of making the rod. The hole is sized for a #10 screw. When installed, it looks like this:

Roll actuator installed.png

The screw is not shown. The attachment will take bit of experimenting with to get it centered in the stick stub. You want a #10 screw that's about 1-1/4" long You'll use a "stop-nut" which is basically a regular nut with a nylon ring pressed into the top. The idea is to allow you to tighten the screw down enough to take the slop out, but not enough to bind up the mechanism. Stop-nuts allow this - the nylon ring ensures that they won't loosen over time.

Roll axis pushrod connection.jpg

To center the rod in the stick stub, you'll need to get two #10 nylon washers and a few #10 zinc washers. Place the nylon washers on the "outside" of the stack. They'll be the washers that will rub on the inside of the stick stub. The nylon won't produce the noise that a metal washer would when rubbing against the inside wall of the stick stub. Take the metal washers and stack them on either side of the rod until you've got the right number on each side that gives the closest to center fit.

The clevis fork is made by taking a 1/4" extruded aluminum turnbuckle and cutting off the left-hand threaded end. You then drill a hole that's the appropriate size for the bolt you're going to use. In my case the holes were drilled for 1/4" and #10 bolts (not on the same clevis).

Clevis fork.png

Next up, making the wooden bearing blocks for the gimbal... First, you're going to need to download the drawing for the bearing parts.

media:pitch axis bearing drawing.dxf pitch axis bearing drawing.dxf

- This drawing was saved in AutoCAD 2004 DXF format. You shouldn't have any problems reading it using any of the freely available CAD programs, you can download a PDF of the plan media:pitch axis bearing drawing.pdf. The drawing will print full size on a single 11x17 sheet. The blocks are made from 5/8" Birch plywood. However, any good quality 5/8" (or close) plywood will work.

Please take your time cutting out the bearing blocks. Here are some recommendations that should help you get a more accurate result:

  • 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. The bearings must be square and aligned to one another or the pitch axis bearing shaft will bind.
  • 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 holesbefore you cut the parts to shape. Trust me, you don't want to be boring a near 1" diameter hole in a part with nearly no material to hang on to while the drill does its job. :)
  • The large bearing holes are specified at .95". The easiest way to reach that size is to use a 7/8" Forstner or Spade bit. This will get you to .875" The remainder can be sanded away with a small drum sander in a drill or a drill press. The idea is to get the size of the holes to the point where they're just a little bit loose around the 3/4" EMT conduit that makes up the pitch axis bearing. Make sure that when you're sanding the parts to shape, you do them in assembled pairs.
  • If you'd rather not sand the holes to size, you can still get good results by boring a 1" diameter hole instead of a .95" hole. The fit will only be a tiny bit looser than what I've specified and it won't affect how the gimbal operates.

Here is an exploded illustration that shows you how the pitch axis bearings are assembled:

Pab exploded.jpg

The bearing is assembled using three 1-3/4" #10 pan head screws and three #10 nylon ringed stop-nuts. It's important that you don't use any washers on this because the washers will actually rub on the bearing shaft when it's installed. The base is attached using two 1-1/2" #8 flat head wood screws. You should countersink the holes for them as shown in the model above.

Now that you've got the bearing blocks made, you're going to need to lay out the position of them on the base plate. This spacing will vary, but generally a distance of about 6-1/4" should be sufficient. When you do your bearing block layout, you'll also want to mark out the space needed to allow the gimbal box to protrude up through the cockpit floor. In my version I'm using a hole that's 5-1/2" wide and 5-1/4" high.

You'll now want to make the pitch axis bearings. They consist of two short lengths of 3/4" 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" on the roll axis actuator side. Below are examples that show you roughly how it should look. Pitch axis connection end:

Pitch axis bearing detail.jpg

You'll note here how the centering rod for the pitch axis is mounted to the bearing. I'm using a #8 eye bolt that has a locknut on both sides to hold it in place. I chose a #8 because the eye is perfectly sized for a 1/4" bolt. You can also just barely see the Du-Bro ball-link that I'm using to connect the pitch axis to the potentiometer that connects to the computer. The ball-links are very inexpensive and very handy to use. The ones I chose are threaded and have a long enough reach for them to be able to pass through the side of the clevis fork. You can see the nut for the ball on the inside.

Roll axis connection end:

Roll axis pushrod and center interconnect.jpg

Here you can see why the roll axis side of the pitch axis bearing needs to be so short. When you move the stick to the far left, the back end of the clevis fork can't come in contact with the bearing tube.

You can also see the roll axis potentiometer connection. Just like on the pitch axis, I'm using a Du-Bro ball-link on the clevis end, and a Du-Bro E/Z Connector on the potentiometer end. This is a very simple and very reliable way to connect your axis pots to your stick gimbal. The last component I'm going to cover is the centering mechanism. The centering mech is very simple. It consists of a 1/4" steel rod that's been threaded on one end, a clevis fork made from a turnbuckle, a pair of springs and some locking collars.

In my design the steel rod is 10" long. Your application may and probably will vary. Here's a picture of the assembly:

Roll axis centering and pot.jpg

As you can see, the whole thing is very simple. A 1x1 L bracket is bolted in place and has a 5/16" hole to allow the rod to pass through it.

A collar on either end holds the spring in place. The springs are compressed against the center bracket just slightly. This provides good centering force for the gimbal.

One option you may want to consider is using two spring pairs. 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. 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.

That's really all there is to it! Below you'll find various pictures of the assembly that will help out in building your own.

Roll axis pushrod and center interconnect-2.jpg Pitch axis pushrod and pot.jpg

Pitch axis pushrod and pot-2.jpg Pitch axis bearing detail.jpg

Pitch axis bearing detail-2.jpg Gimbal box detail.jpg

Roll axis pushrod connection-2.jpg