Yaw Axis Assembly Results

Lots of progress this weekend, with lots of lessons learned!  We manufactured the base and the yaw yoke axis bearing, and mounted the yaw axis on the floor in the basement.  We also installed the yaw yoke drive system to test backlash and rigidity.

Yake yoke drive shaft, below:

The drive shaft itself was fairly easy to cut, taking about two hours on the first attempt.  The shaft is 1.5″ in diameter at the base and steps down to a 1-3/8″ – 12 thread, then to a 30mm diameter step for the slipring, and finally to a 1-1/8″ diameter for the drive pulley.

The drive shaft attaches on its base to a half inch steel plate, which then bolts on the the frame (the base, in the case of the yaw yoke).

This is the mounted base with the yaw yoke drive shaft attached.  The mounting plate is actually welded to the drive shaft.  That build process ended up taking a long time, and I think that we’ll need to revisit how to attach the shaft to the mounting plate.

Here is the yaw yoke mounted to the base, with the drive assembly attached.  The bearings are almost rigid enough, but not quite.  We have some ideas about how to fix that.

The frame itself is also really rigid.  There is no noticeable deflection on the base assembly, and deflection on the yaw yoke is minimal.

As always, Hobbes was around to help.

Now on to the biggest problem: the drive chain stretches!  A lot.  I expected some stretch, of course, but not nearly as much as we are getting.  You can grab the yoke arm and push, moving the assembly 5 to 10 degrees with very little effort.  Turns out that this is just how chains tend to behave.  It’s looking like we are going to have to do a significant redesign of the drive system.

That’s a little disappointing, of course.  I at least was feeling fairly confident that we were on the right track with this design.  Modifying the drive assembly is going to involve either rebuilding new yoke arms or cutting them apart .  Either way, it’s going to take a lot of time… [sigh]


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Outer Yoke Assembled for Stress Tests

Last night we mostly finishing welding the yaw, pitch, and roll gimbal arms, and then we bolted them together.

The axis bearings aren’t finished, so we can’t really build the complete assembly yet.  But bolting the arms together directly allows us to test the frame’s rigidity.

Above: laying out the roll yoke arm.

More work on the roll yoke.

Roll yoke side plates attached.

Pitch yoke assembly.

Almost there, just need to weld the inner ribs.

Above: Yaw, pitch, and roll yokes together.  Roll yoke was almost finished before we ran out of wire.

Above: A highly technical, sophisticated, scientific stress test…

Well touch this up with a grinder, have it sandblasted, and then powder coat it.  It’ll have a nice look, IO think.

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Almost Ready!

We’ve made a lot of progress on the design for the three degree-of-freedom simulator, and are hoping to order parts to start the build early next week.

This new design allows for continuous rotation on every axis, although it will require a lot of space to do so.

Three degree-of-freedom motion simulator prototype
This design allows for continuous rotation on every axis.

Rigidity might be tricky on this one.  After running the numbers on some worst-case scenarios, we think that the frame itself will deflect less than 0.16″ on the inner axis.  The axis bearings may cause more than that, though.  And it’s difficult to know how the new drive train is going to perform in terms of backlash and rigidity.

But we’ll find out!  The build process will start next week.

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