burning question - HSI?

[ruprecht]

I would love to see your ideas too Andy. I had designed it in my head and came up with the following (based on the F-16 HSI rather than the civvy one mentioned earlier in this thread, reposted from ViperPits):

- The project would need four geared steppers: One for the inner CRS/CDI plate, one for the compass card, one for the RMI needle and a fourth for the heading bug. Right there you need either four concentric axes or ring gears. Complex when constructing from hobbyist materials!
- The inner plate also needs a servo mounted on it for the CDI needle. This presents a further problem for power and signal wires that must come from the control circuitry through the hollow centre axis to the servo, in such a way that repeated rotation of the CRS needle will not twist up and wreck the wiring. You would have to look at something like a 4-signal brush contact (such as a stereo+mic miniplug). This is not counting the off flag and TO/FROM indicators on the CRS/CDI plate which would require either separate control wires (again wired through the hollow axis, needing yet more brush contacts) or you'd need to build a microprocessor-controlled circuit on the back of the CRS/CDI plate that could handle the servo and all 3 flags with only 4 input wires.

The remainder is fairly well understood with 7-segment LEDs for the miles and course indicators, solenoids for the outer off flag, rotary encoders for the HDG and CRS knobs and optical interrupters etc.

When you say 7 servos would be needed, do you think it could be built with servos? Wouldn't you need steppers for continuous rotation of the cards?

[cscotthendry]

Guys:
Get busy scribbling. Put your ideas on paper and let me see them. I have a lathe and milling machine and the tools to cut gears as needed. Also I have a copy of the faceplate (outer facia) of the artificial horizon that could be modified (slightly) to make them look like the real thing. I'd be prepared to have a go at making a few of these if we can come up with a workable design. But lets do this offline of the forum. Go to my website, get my email address and PM me directly and let's have a go at it.

[Michael Carter]

Please post any updates or breakthroughs on this project.

I'm very interested in following your progress.

[ruprecht]

I will get designing. I respectfully disagree with moving it to PM, isn't the whole point to let others get the benefit of our thoughts? In the end, this is a thread specific to an HSI, so why not discuss here?

However, understand that a forum is not necessarily the best way to collaborate; if I get some time later I might throw up a Wiki and a new project on my JIRA issue tracker which you can all access, would that work for everyone?

*EDIT* Wiki page is here: http://vaaf.net/wiki2/index.php5?title=HSI this is on the VAAF forum/wiki that I co-moderate.

Scott, I've come across your site before, very impressive mate! The design in my head needs ring gears, so I had hoped you and your gear cutters would throw into this discussion!

[cscotthendry]

Ruprecht:
I think the forums are a great place to get advice and solve problems, but not so great for brainstorming and just general comms.

If by ring gears you mean rings with teeth on the inside as well as the outside of the ring, then I can't do that. I can only cut teeth on the outside of things. To cut teeth on the insides requires something like a broaching machine. But if you mean a ring with smooth inside, yep, can do that!

BTW, I've bookmarked the wiki. I've never wiki'ed before so it'll be a bit of a learning curve for me. Bear with me.

[Michael Carter]

For the inside of a ring you can use a capstan roller like those used on tape machines. Hard rubber and lasts fairly long. I've only replaced one on the tape machines I have in nearly ten+ years.

You can mount a capstan rollor on the drive end of a servo or stepper motor.

[cscotthendry]

Hey, that's a good idea!

[AndyT]

Ok, I've never used Google Sketchup before so I'm trying to put my idea together in 3D. The scribbles I have on paper would only confuse you.

What is our time line on this project?

[cscotthendry]

Err Timeline? This is a hobby for me so.. whenever. BTW I'm retired so anytime's a good time for me and every day is Saturday

[AndyT]

Good answer! (ding ding ding!) LOL