burning question - HSI?

[cscotthendry]

Hi all:
Here's the latest. Ruprecht and I are going to get together over lunch and discuss the developments so far. I have his 3dsmax model in DXF form and will be translating that into a more precise CAD package. 3dsmax seems to be great for visualization, but doesn't do the things needed for manufacturing. So this topic will go quiet from my end for a while, while I translate ruprecht's model (with a few improvements) into Solid Edge.

I'll keep you all posted on the news as I progress this gauge.

[ruprecht]

And to add to Scott's comment above, I'm trying to keep my head above water with work atm and the HSI is slipping down the list. The situation should be smoother in a week or so. Progress is occurring, never fear.

[ruprecht]

Scott and I had a great catchup the other day and, amongst many other things related to the HSI, had a think about our influences with this project.
We should really acknowledge the work of Mr Felipe Lopez Gerola from Bilbao Spain. He put together some amazing 2d drawings of a hobbyist HSI which, when I came across them on Viperpit, inspired me to visualise the instrument in 3d from hobbyist materials.
There are many people we would not be at this place in the design without; Felipe, Mike Powell, and all the amazing and talented builders out there. Here's hoping we can get this instrument done and give something back to you all.

[cscotthendry]

Well I've started to transfer the design into a CAM friendly package called Solid Edge. Along the way, I've started to think about the jigs and machining fixtures we'll need to make the parts. As a proof of concept and to help me learn Solid Edge, I designed a machining fixture to make the gear for the heading bug.

[cscotthendry]

I've started modelling standard parts for the construction. One of the things we'll need is servos. I've settled on the Hitec HS-55 as the modelled standard servo and created a model for it.

[AndyT]

Nice work guys. I'm working on the driver circuits that go inside the housing. Just block schems for now till I get some more precise measurements from Scott.

[cscotthendry]

Modelling, modelling modelling
I needed a reference for the positions of the control knobs etc so I modelled the BK facia

[AndyT]

Looks good. I like the 'FlightSim Avionics'. What is DG? Directional Gyro?

[cscotthendry]

Flightsim Avionics is my company name. I've registered a .com with Planet Domain for it too. So that's ready when the time comes.

It's actually DC for Direct Current vs AIR for air In the pic it also looked a bit like BC to me, but it's not that either. If you look closely at the lettering it is actually extruded from the front surface.

I have an RFQ in with a local plastics company for getting moulds made and a production run of about 100. Just to see what it would cost.

[P1IC]

Hello again guys. Probably way too late, as I suspected, but it has taken toooo long to get Internet access here at my new address. Satellite, unfortunately.

Anyway, I said I would post my thoughts on a system which avoids the need for brushes in the CDI section. Four pics. Pic A shows the arrangement for moving the CDI indicator across the back panel (where all the TO, FROM etc stuff is, not shown here for clarity). This is a back view looking behind the CDI backing panel. You can see the white CDI needle strung between the two lines of cord.

When the red cog is spun, the green shaft through it also spins, driving the cords and moving the needle. Here I am assuming the green bits are fixed to the frame, ie. the CDI doesn't rotate (yet).

Pic B shows the drive arrangement in red for the CD needle. The stepper applies torque through the worm gear to the red shaft which turns the original little cog.

Pic C shows the arrangement for turning the CDI, through the green shaft. What you don't see in this pic is that the green shaft is fixed at its front end to the CDI assembly. Running the green stepper turns the whole CDI assembly including the little red cog - and this is where the problem lies.

If the green motor runs, the red cog will spin around the red drive system, making it turn and causing the needle to move. We don't want that, so whenever we turn the green drive we also need to turn the red drive the same amount in the same direction, so that the needle stays in the same position on the CDI face. So no brushes are needed. It's all done in the PIC software.

Pic D shows a bit more clearly how the assembly looks with the CDI drive cage mostly fleshed out. Of course, the rollers for the cord are grooved pulleys (I didn't draw them like that for simplicity) and the wrap of the cord around the driving shaft is more involved than shown here, but not difficult.