Jump to content

[WIP] The REAL Nav Ball Project Thread


NeoMorph
 Share

Recommended Posts

6 minutes ago, NeoMorph said:

The reason the screws wouldn't be visible is that there is a cover that goes over them on the real 8-Ball. In fact you have probably seen it multiple times and never realised.

Can you spot the end cap cover in this image (hint: red marks the spot heh)?

Ah, yeah - I see it. Found a pic where the pin is a lot clearer: (from this site) and would be just something easily aquired from a hardware store. awesome! I've been doing my head it trying to find a solution to that all day. (I added a few other options in the post above. And yes, the original FDAI is an insane piece on engineering that I'm jealous that you have one.

fdai12_300.jpg1317_appli1.jpg

 

As an aside, in my search, I also came across this gorgeous piece of 3d printing.

 

 

Link to comment
Share on other sites

6 hours ago, wile1411 said:

Ah, yeah - I see it. Found a pic where the pin is a lot clearer: (from this site) and would be just something easily aquired from a hardware store. awesome! I've been doing my head it trying to find a solution to that all day. (I added a few other options in the post above. And yes, the original FDAI is an insane piece on engineering that I'm jealous that you have one.

Actually that centre bit pops out, leaving a hole that you can then pop out the entire red area. The screws are hidden underneath.

... oh and I don't have one... I just have done an insane amount of research and hours of lying in bed thinking about how to do it. Doing 3d manipulation in my head is something that used to help me a lot during maths and the only thing that stops it is the morphine I have to take... so I've gritted my teeth and taken my dose late so that I can have a couple of hours of mental exercise... problem is that when I do that I get hyper... and if I answer on here I end up doing damned monologues lol. Old girlfriend called it my "Verbal Diarrhea" mode.

The only thing that was problematic was designing the the axle and hubs that connect with the three screws and then gluing them to the sphere itself. It's easy to epoxy it but metal to plastic ends up with a weak joint. That is why I finally decided on using an acrylic disc with the screw holes in would be cut by the CNC for a perfect fit and acrylic welded to the sphere so they in essence become a single piece. I even planned on using casting acrylic to make the disk support but found that when you cast in a mould the darn thing shrinks too much. So I cut the disc out of 6mm of solid acrylic. If it ends up not being strong enough I will use 10mm.

But it's going to be cramped in there as it is. Two steppers, hall effect sensors, Slip ring wiring connectors and bearing mounts... Going to be hard. So I'm still going to try and make a larger version first (I had a bunch of larger spheres arrive from an ebay order I had forgotten... must have taken 8 months lol).

Link to comment
Share on other sites

  • 3 months later...
On 2/4/2018 at 12:59 PM, NeoMorph said:

Actually that centre bit pops out, leaving a hole that you can then pop out the entire red area. The screws are hidden underneath.

... oh and I don't have one... I just have done an insane amount of research and hours of lying in bed thinking about how to do it. Doing 3d manipulation in my head is something that used to help me a lot during maths and the only thing that stops it is the morphine I have to take... so I've gritted my teeth and taken my dose late so that I can have a couple of hours of mental exercise... problem is that when I do that I get hyper... and if I answer on here I end up doing damned monologues lol. Old girlfriend called it my "Verbal Diarrhea" mode.

The only thing that was problematic was designing the the axle and hubs that connect with the three screws and then gluing them to the sphere itself. It's easy to epoxy it but metal to plastic ends up with a weak joint. That is why I finally decided on using an acrylic disc with the screw holes in would be cut by the CNC for a perfect fit and acrylic welded to the sphere so they in essence become a single piece. I even planned on using casting acrylic to make the disk support but found that when you cast in a mould the darn thing shrinks too much. So I cut the disc out of 6mm of solid acrylic. If it ends up not being strong enough I will use 10mm.

But it's going to be cramped in there as it is. Two steppers, hall effect sensors, Slip ring wiring connectors and bearing mounts... Going to be hard. So I'm still going to try and make a larger version first (I had a bunch of larger spheres arrive from an ebay order I had forgotten... must have taken 8 months lol).

I wish you the best of luck, @NeoMorph

Spoiler

If we want one, but lack the skill to put one together, would you sell a USB panel mount one?

 

Link to comment
Share on other sites

  • 1 year later...

Some of you oldtimers here will know that I have been working on building a working FDAI (Flight Director/Attitude Indicator - the Apollo 8-Ball) system since 2013... As I can only work during the summer months when my disability isn't playing up the progress has been sloooooooooow... but I'm actually getting closer to a prototype that is actually closer to the original Apollo Navball/8-Ball that I expected.

You see I started out trying to use stepper motors... they worked, sort of, but the sheer bulk of them meant the damn ball was unbalanced. You also have a problem in that they draw a bunch of power too and I burned out a slip ring doing it that way.

For those not knowing anything about robotics, a slip ring is used to transfer electrical signal from a stationary part into a rotating part without twisting up wires. The Apollo slip ring is actually easily visible in the opened up original FDAI.

c4AB9AT.png

 

37KleVS.png

 

There is also a slip ring at the back of the unit... this image is taken from the 8-ball used on the shuttle. You can see the contact whiskers clearly here as they have been moved out of the rotating part.

ADI_717868_in7_300.jpg

(Note: All images are from the Historic Space Systems website - http://www.space1.com/Artifacts/Apollo_Artifacts/FDAI/fdai.html )

 

Making  slip rings for my model was out of the question (I just don't have the skill)... but luckily, thanks to robotics and even wind power (yeah, they use them on rotating windmills) I found small slip ring modules on ebay cheap enough and small enough to fit my model.

The reason my slip ring burned out is that the contracts were only rated for for 2 amps and the steppers I used actually peaked higher than that when I was seeing how fast I could go.

Then I went to motors and incremental angle sensors. The problem with that version was that you had to calibrate the thing every time you turned it on... and it also tended to lose position after a while so it would need to get updated often. So that version was a fail

Then I worked on 360 servo driven with a differrent incremental rotation sensor... and it worked... but the big breakthrough was when I found a little sensor package that actually knew the ABSOLUTE angle all the time... so you could turn off the thing and turn it back on and it would instantly know what angle the ball is at. With an incremental sensor you could have the Roll axis at 40 degrees but when you turned the thing off and on again the angle would now read 0 degrees. With the Absolute sensor it would say 40 degrees right away. Makes this sooooooooooo much simpler. 

The test version of a single axis worked great but the roll axis burned out the servo... It was also too slow when I put the capsule in a roll so im going with a proper geared DC motor instead and making my own servo system.

So that's this years task... buid a full scale version of the 8- ball, engrave the ball itself and make and laser engrave the front bezel. I'm also using 6 servos to drive the rate and "Fly to" needles so that's a simple enough task. I just need to design a stepped housing for them.

Currently I'm working on updating my CNC machine to do laser engraving work as well as doing the part cutting. I'm also raising the gantry (which I've been putting off for over a year now) to allow my to cut taller parts..

Edited by NeoMorph
Link to comment
Share on other sites

7 hours ago, magnemoe said:

That was an insane amount of connectors as in 14, its already dual redundancy but assume 2-4 is used for ground it should still get 9-11 channels. 
 

I think a lot of the duplication was to make sure the contacts actually kept in contact (as is the fact that while the ball is in motion and the spacecraft itself moving meant the connectors actually bounce leading to possible intermittent breaks in signal. Inside the ball are two motors and two angular resolvers (as in sensors that detect what angle the ball is at. I found that my incremental sensors were occasionally resetting to zero when the movement was rapid. The Block I command module only had a single 8-Ball and the astronauts weren't confident about the build quality of the hardware (which was sadly what led to the Apollo 1 fire and the loss in life of Grissom, White and Chaffee) so the Block II command module and LEM both had dual 8-Balls for this very reason. In fact they called the Block I command module a "Lemon" and Grissom actually attatched a lemon to the NASA logo to point this out. Not a single Block I manned mission was flown.

Was the Apollo 1 fire a tragedy... yes, but I truly think the redundancy they included in the Block II flight hardware is what meant they succeeded in getting to the moon, and more importantly, safely BACK from the the moon.

Link to comment
Share on other sites

Regarding the absolute angle sensor... it all works on a custom hall-effect chip. Use a diametrically magnetised magnet on the end of the axle and you can tell what angle the axle is at. Because the axle is actually going to have the two sides of the spheres attatched for the pitch access, the yaw access is going to be blocked by the motor on one side and the wires through the slip ring on the other and the final axle is just blocked by the slip ring on the one end and not having access to the other as it's going to be rotating... well the fix for it is... gears. Just take a pair of gears of the same size and make a second axle... then you can attatch the magnet to the second axle and you can read the angle from that. As it's a mirror of the primary axle you just have to put the sensor on opposite the direction to what you would if you were reading direct from the primary (that's a bit of a mouthful lol).

Oh and can someone tell me why diametrically magnetised magnets are a load more expensive than normal magnets?

This little breakout board works great with an arduino and only requires VCC, GND, SDA an SEN to read it. There are two of these inside the ball and one on the outside. As each one needs a separate address so the correct one can be read you need to be able to do some microsoldering

TWp0waX.jpg

Here are the two zero ohm resistors (basically a wire but in an 0805 package... look for the little grey rectangle with the 0 on top) that are basically hardwired switches. The I2C switches are in the correct place but for the ADDR SEL I have to change two of the the boards by moving the resistor so that board one is as below, board two has the lower resistor moved and for board three the upper resistor is moved. You need a steady hand and good eyes... or cheat like me and have a kickass microscope for microelectronics work. It even has a port to output to a camera so I can look at what I'm seeing on a large monitor.

yDjNqD0.pngmiE96IB.png

 

So yeah, it's taken me since 2013 to find a suitable solution to what was done back in the 1960's. Granted they had millions of dollars behind them but were held back by the technology of the time. Oh and before I found this little chip for £11 the cheapest absolute sensor I could find was over £600 (which was why I was having problems)... and I need to use three of them... plus extras in case of failure and/or me breaking them. I always thought flight sim hardware was a rip-off but I can honestly say I understand it now.

Link to comment
Share on other sites

I just noticed something... I was looking for a reference shot of the original FDAI case when I spotted the original's tag...

kUB4pzn.png

Wouldn't that make it an IAFD and not an FDAI... I wonder who changed the name... and were Honeywell peed off that they changed the name lol.

Link to comment
Share on other sites

  • 3 months later...

Really awesome and ambitious project!

I had a thought, looking at it, that a purely practical way to go might be to put a wireless micro module and accelerometers (ESP32 + MMA8451 or similar) inside the ball -- then you could dispense with the slip rings entirely and just deliver power over the pivots.

Of course, this is much less mechanically and conceptually beautiful than the slip ring solution...

Link to comment
Share on other sites

On 6/21/2019 at 5:29 AM, NeoMorph said:

Wouldn't that make it an IAFD and not an FDAI... I wonder who changed the name... and were Honeywell peed off that they changed the name lol.

Nah... Military nomenclature is generally listed as general/category, to moar specific description of an item... rather than the reverse, as in common English usage.
ie first and foremost, its an "indicator"... type of, "attitude"... specifically for "flight direction"... versus, say, an indicator for attitude, for a specific weapons system... or if it were an indicator for altitude for a radar altimeter system, or an indicator for altitude for a bomb sight system... etc...
Like, in someone saying "hey, whats the Radar Altimeter Altitude Indicator say?..." or "Whats the reading on the <gun turret> Attitude Indicator read?..."

Edited by Stone Blue
Link to comment
Share on other sites

  • 1 year later...
On 6/21/2019 at 3:44 AM, NeoMorph said:

Regarding the absolute angle sensor... it all works on a custom hall-effect chip. Use a diametrically magnetised magnet on the end of the axle and you can tell what angle the axle is at. Because the axle is actually going to have the two sides of the spheres attatched for the pitch access, the yaw access is going to be blocked by the motor on one side and the wires through the slip ring on the other and the final axle is just blocked by the slip ring on the one end and not having access to the other as it's going to be rotating... well the fix for it is... gears. Just take a pair of gears of the same size and make a second axle... then you can attatch the magnet to the second axle and you can read the angle from that. As it's a mirror of the primary axle you just have to put the sensor on opposite the direction to what you would if you were reading direct from the primary (that's a bit of a mouthful lol).

Those hall effect absolute position sensors really are a game changer! I used one on my Radar Altimeter tape meter.
I have a motor driving two timing pulleys, one to the 6 turn tape meter input shaft, and the other to a 1:6 ratio pulley attached the the sensor.
I'd lost track of this thread a while back, so coming across it again, I'm very happy to see you're still working at this, bit by bit.
Man, I kinda wish I'd have kept track... I didn't discover those absolute position sensors till early this year...
I could have had a half year head start on this... When the Covid hit, getting parts shipped became an absolute nightmare!

I realize that the security camera gimbals I have could easily have their 128 step encoders swapped out with Absolute Position Sensor units.
That would leave the only part requiring manufacturing to be the ball and plate itself, and the yaw and pitch motors to drive it. 
I never looked into developing that, since I had the ARU 11/A FDAI I bought back in 2015.

Good luck with the project! 

Link to comment
Share on other sites

  • 11 months later...
  • 1 month later...
On 6/21/2019 at 3:44 AM, NeoMorph said:

Regarding the absolute angle sensor...

I spent a little more for entirely enclosed absolute position sensors with a bearing mounted shaft and a fully assembled and closed housing. These are exactly what you have, but with a digitally derived analog output, instead of a serial interface. 0-360° outputs 0-5 volts. Three axes absolute positions can be driven by just 3 signal wires and 2 power wires. They are light weight, have an integrated bearing and shaft, and could be utilized to potentially simplify the overall design, vs trying to mount an open PC board and a loose magnet. I do love these Absolute Position Sensors. They really are a game changer!

I do certainly hope you are still pursuing this project. It has great potential, and I feel like you were getting much closer to a working solution for the project. Shortcuts like preassembled absolute position sensors and using PC boards as mounting plates could very much streamline the project. I wish you good luck and good progress. Also hope you're doing well... You've not logged in since last summer.

MV5LOmH.jpg

Edited by richfiles
Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...