burning question - HSI?

P1IC, I'd love to see pix of your design if you are willing to share them. 3D is better of course. It sounds like a novel solution but I have questions the Pix will answer.

No problem if you don't have the book, its not a requirement. But it is very close to the 'standard' way instruments are built and when done, you have a very high quality instrument that perfectly imitates the original. (Well, almost perfectly)

Once this design is finalised, it will be fairly easy to duplicate for nearly anyone since we are using off the shelf parts, with the possible exception of the gears which can be sourced fairly easily.

Thanks for posting and adding to our progress!

Ruprecht:
It would be better if the optos were all in line, then they could all be mounted on one piece of circuit board. Like Andy, I would prefer to keep the home sensors as optos. With the reed switches, I've found that you have to home them from either clockwise or anticlockwise. Also they're a bit inaccurate so there are some calibration issues as well as accurately placing the magnets on the gears. Not to mention them falling off (possibly).

Re: The RMI pointer?? I'm not familiar with the F16 gauge, but on the BK gauge the course pointer is just an extension of the CDI needle. It doesn't rotate independently of the CDI. Additionally, the CDI card rotates in sync with the compass card except when the course is being changed. Ditto for the heading bug.

P1IC: welcome to the thread. I didn't quite work out what you were suggesting, but I'd sure like to see some drawings of your ideas. Like Ruprecht, I'm a visual person. However I agree with the sentiment of making software do as much as possible. Having said that though, the whole thing could be done with a small color LCD but that's not really what we're trying to achieve.

Ruprecht: When we get down to cutting gears and bits of metal, we gotta get together. I'm sure there will be a thousand details to sort when we start making metal shavings. At that point your skill with the CAD package is really going to be crucial.

*EDIT*Ruprecht with respect to clearances in the optos, no problem, just make the gears thinner. 3mm at the sizes we're working is WAY overkill anyway. You could take them down to 1.4mm no problem.


Cheers

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Originally Posted by cscotthendry

Re: The RMI pointer?? I'm not familiar with the F16 gauge, but on the BK gauge the course pointer is just an extension of the CDI needle. It doesn't rotate independently of the CDI. Additionally, the CDI card rotates in sync with the compass card except when the course is being changed. Ditto for the heading bug.

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The CDI is on NAV1/ILS and the the CRS pointer is, as you say, affixed to the CDI card coaxial with the CDI indicator in its centre position.

The RMI flag is exactly that - an RMI. an independent pointer that points to the VOR tuned on NAV2 (with no course information other than direct bearing-to/from).

I suppose you could make it work as an ADF instead in software by using the NDB bearing tuned on ADF1 instead of the VOR bearing on NAV2. Could even include a VOR/ADF toggle on the instrument I guess! Maybe for version 2 :)

Ruprecht:
OK, I've got an RMI gauge that has a pointer that does that. But it only has the card and the pointer not all the other stuff as well. I guess then that modding your design to the BK will mean reducing some of the functionality (which is just fine by me :D)
Given what you say, it was inevitable then to have four gears involved. No matter though as you've done the hard stuff fitting it all in.
Just thinking on it though, I would rather have the GS bars than the extra VOR indication. VOR 2 could always be done on a "conventional" RMI (another project???)

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Originally Posted by cscotthendry

Ruprecht: When we get down to cutting gears and bits of metal, we gotta get together.

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No worries mate, that would be great. PM me if you're going to be in the city during the week, I can meet up for lunch and show you over the model.

I reckon we'll be able to make shavings pretty soon - if you wanted to get started cutting some of the 120-tooth gears I reckon they're pretty much set in stone now once we've settled on a width.

Re the gear width, the reason I went 3mm is to give it a little bit of wiggle room with hobbyist construction so even if they're off a bit they will line up with mating gears pretty well. Let's make a call on the width so a) I can finalise the CAD on the gears and b) you can get cutting. I vote 2.5mm if the material is available.

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Originally Posted by cscotthendry

Ruprecht:
OK, I've got an RMI gauge that has a pointer that does that. But it only has the card and the pointer not all the other stuff as well.

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Yup the only place I've seen a combined HSI/RMI is in military aircraft (or on civvy glass). One's initial aviation experiences tend to drive one's preferences for life - I still have trouble with the "pendulum" style VOR gauges and fixed-card ADF, but give me an HSI/RMI and I'll navigate head-down all day :) For the same reason I resist GPS, as I learned IFR doing NDB approaches! Old school!

On the BK, my intention is to proceed with the current design to finished stage to "prove the concept" and then branch it for the BK. I will build the F-16 style, if you guys build BK style (minus the RMI ring) it will be a good proof that the design can be adapted to most any HSI. If the firmware and circuit supports an RMI, it's a simple thing to just not connect that stepper.

Ruprecht:
Yep I agree. If we do the hard one first then it's easy to take stuff out. Also I agree with your sentiments about the D'Arsonval movement based VOR gauges. Never liked the look of them. When I first started working on airplanes they were the mainstay and I always thought they looked icky.

What's this "you guys" build the BK;) You're in too deep now. BTW are you interested in having a go on the mill and lathe? I could probably use some help when we start to make the parts. Besides as I mentioned before there will undoubtedly be changes needed for the practical construction and I sure would like to have you on tap to thrash out the design.

Anyway, If we do the military version that we're working on and then convert it to the BK style, we should have the market pretty well covered. We'll make millions ;) Have you picked out your new house yet? I've got my eye on the new Bugatti.

Money? Theres money involved?? Hmmm... I think I'll buy a new Cessna with the G1000 installed... Gotta go low and slow.

lol, the smiles on the faces of all the happy pitbuilders as they power up their HSI will be all the reward I need :D

of course, my own Bell 47 or Spitfire would be nice too. With an HSI.

Actually to be serious for a sec, I think if we pull this off we will be inundated with requests to supply detailed instructions, plans and cut gears for folks. We should start thinking in advance what our response to that is - personally I am happy to make plans in user-friendly format but have no interest in building complete units for sale. eMachineShop, Serv-o-link and the like should do a roaring trade in the gears. It would be nice to find someone with a CNC machine to cut the plates though - the thought of hand-milling them leaves me cold.

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Originally Posted by cscotthendry

What's this "you guys" build the BK;) You're in too deep now.

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OK let me rephrase: WE shall build an F-16 style for me and 2 BK style (or whatever you prefer) for your guys :)

And I'd love to have a crack at the milling if you're prepared for bits of the mill to go flying around the workshop :) I have 2 left thumbs when it comes to metalwork - to be fair I'm lucky to have any thumbs left at all!