fbfan64

Suction Gauge Got a few days off over Thanksgiving so working out a few more gauges. I started work on the altimeter, but I had to order some parts and decided to get the suction gauge working while waiting. Inside I find the familiar diaphragm driving a tiny spring loaded gear movement. The gear amplifies the small movement of the diaphragm enough to make the pointer rotate almost a full revolution (about 300 degrees). Turns out there was very little I could re-use. I ended up only using the original face plate, pointer shaft, and pointer.

Good ideas. I'll have to see if I get the time to follow up. Right now I'm so crazy with work I haven't even worked on the pit for I think a month.:cry:

I have some more coming. The temperature gauge is next. I'm temporarily side-tracked with work so it might be another week or two before I get back to it.

Thanks for the kind words. I took a look at your pit build page. The work you've done is impressive. I like the ingenuity where you combined the metal work with wood pieces and plastic (looks like 3d printed) to get the best of all worlds.

Repeater Compass The repeater compass was pretty easy. The course adjust is self contained in the front part of the gauge inside the bezel. I replaced the entire inner movement with some printed brackets and Bob's your uncle. The original movement was driven by an Autosyn motor. This is essentially a synchro system. This indicator is just a repeater or remote compass, driven by the source housed somewhere else in the aircraft. The rotors in an Autosyn system are two-pole electromagnets and the stators are delta connected three-phase, distributed-pole windings. The rotors in the transmitter and indicator are connected in parallel and are excited with 26v, 400Hz AC. The rotor in the indicator follows the movement of the rotor in the transmitter. Since I don't have any intention of generating 26v, 400Hz, I just removed the autosyn motor and mounted my stepper motor. All cleaned up and put back together...

Accelerometer (G-Meter) The accelerometer was interesting to see how it worked originally. Converting it to a simulated stepper driven gauge was mostly a challenge in designing a new shell that also housed all the little parts needed to make the reset function work. The accelerometer has 3 pointers on it. One shows the currrent g load while the other two show the maximum positive and negative g's that have been experienced since the pointer was last reset. The mechanism to handle the max pointers is self contained and I re-used it entirely as is. This way I only have to drive the center pointer with a stepper and the other pointers and reset function work the same as before. Each of the max pointers is driven when the main pointer moves in that direction. Then it is held in place by a ratchet mechanism. When the reset knob is turned, both the positive and negative pointer ratchet mechanisms are released and the two pointers are driven back by springs to the neutral position. The main pointer (current g load) is driven by a combination of weights acting against a set of springs. As the aircraft makes a maneuver, pulling g's, the weights swing around, moving the pointer. As the aircraft g load decreases, the springs pull the weights back in to neutral. The two weights can be seen at the bottom of the next picture. The return springs are about in the center, running across the gauge. The ratcheting mechanism is at the top, just under where the face plate attaches. The reset mechanism is relatively simple in design, but a bit of a pain to put into my own housing. It is essentially a pin on a spring loaded shaft. As you rotate the shaft, the pin turns and pulls on the reset arm of the ratchet mechanism. A couple of pins hold the spring in place and act as movement limits for the shaft. The next photo shows it all mounted in my new housing. Next I mounted the stepper motor using a 3D printed bracket mounted to some existing holes in the frame (where I removed the weights and springs). ...and all cleaned up and back together.

Yes, I find it quite interesting and a bit humbling how much they did without the use of stepper motors, integrated circuits or even transistors. They had to account for such details as the exact movement of things based on pressure and material properties and account for spring strength (which typically changes as a spring coils or compresses). And they did it without the use of PCs and CAD programs.

Vertical Speed Indicator This one is also known as variometer, climb and dive, rate of climb and probably a few other names. From my days working on the S-3 simulators for the Navy, it was known as the VSI and that's what stuck with me so that's what I call it. The VSI looks pretty much like the other pressure driven instruments except it has a gear attached to a shaft that can be turned to provide an offset to zero the pointer. For the simulated instrument that isn't needed so for my purposes it is ignored. In converting this to a simulated, stepper driven gauge, the only new challenge was the design of the housing to fit this particular movement frame. I had some lexan left over from other work and used the CNC to cut out a new lens to replace the broken glass from the original gauge.

Airspeed Indicator The airspeed indicator looks a lot inside like the manifold pressure. Makes sense because both gauges use pressure to drive the indicator. (The airspeed indicator uses the pressure from a pitot tube.) This airspeed indicator doesn't come apart at the back. This is the first one where I've had to remove the pointer and face plate. A bit nerve racking since I didn't know if the pointer was meant to be pulled off and replaced or pulled off and re-used. I only have the one so if it's a one time use I'd be stuck. Being a resourceful guy, I found an old sale on ehay of a technical order for this instrument. By zooming in on the sample photos I was able to see the instructions indicating to remove the pointer. I took the plunge and fortunately the pointer can be pressed back onto the shaft. Here you see the mechanism with face plate and pointer removed. There is a large copper colored diaphragm at the back of the gauge which expands based on the pressure coming into the gauge. The other movement hardware in between converts the diaphragm movement into a rotational movement, amplified by the large gear ratio. The gear ratio is so large they don't need the entire large gear, just a small arc as you can see in the photo. Because everything is mounted to the diaphragm and the back of the enclosure, about the only thing I could reuse was the face plate, pointer and the pointer shaft. Then from the outside, I was able to reuse the front half of the bezel and the glass. The rest of the internal movement and back half of the enclosure had to be designed and printed. So this one didn't present any new technical challenges to solve, but did involve a lot more designing of mounting brackets, housing, etc. All cleaned up and reassembled

Thanks! I've been watching your pit build for a while. You are doing some fantastic work. I think mine will not be as realistic as yours, but hopefully every bit as much fun! :joystick:

Tachometer The single pointer gauges are getting a bit easier to convert now that I have finished a couple and have some items to re-use, such as connector boards, stepper boards, printed brackets, etc. The main difference now is coming in how I attach the stepper to the original gauge movement. That varies depending on how the original gauge is designed. For example in the manifold pressure gauge, it was easier to use a small mini stepper motor connected through a gear set to drive the pointer. In the tachometer, I found a nice fat shaft attached to a beefy bearing and decided to run it with a regular stepper motor. Here's the tachometer: Removing the back half of the gauge revealed there is actually a small electric motor in there. You can see the coil and brushes in the half on the left. On the right, you can see magnets mounted on the shaft that turns. In the front half of the gauge, there is a mechanism that drives the pointer. I haven't figured out exactly how it works but the faster the motor turns, the more pointer deflection. (Makes sense! :doh:) Here's a look at the shaft with the nice bearing. This is why I chose to use a regular stepper motor and drive it directly. It's a bit too heavy for the mini stepper. This is the small stepper motor I used. I've attached it to a bracket I printed that will attach to the new gauge housing I printed. The coupler on the shaft will attach to the shaft in the gauge movement and it houses the magnet I use with the read switch to mark the home position. And finally, the completed gauge with new housing on the back half, mounted in the panel. Next up....Airspeed Indicator. :joystick:

Manifold Pressure Gauge Each gauge I convert seems to yield an interesting nugget of how things were engineered back in the day. :smartass: With the manifold pressure gauge, it's essentially a mechanical amplifier. Here's the gauge: There is a tube connection on the back of the gauge that brings in the pressure. The pressure causes a shaft to rotate against a spring. The more pressure, the further the shaft turns. The mechanism then uses a gear ratio to work as a mechanical amplifier. The movement due to the pressure is quite small but needs to cause a much larger swing of the gauge indicator needle. By attaching a large gear (or a segment of a large gear) to the pressure driven shaft and a much smaller gear to the indicator needle shaft, a very small movement of the pressure driving shaft causes a much larger rotation of the indicator needle. Here you see the parts removed from the gauge to make room for a stepper motor: And here after the stepper motor and related wiring installed: And the new 3-D printed end cap complete with connector:

Nice video. I love the cup holder with the remote control in it! I love the pit even more. Great to see it all working.

Thanks for making and sharing these. I haven't done much in the mission editor and it's a bit daunting to start from scratch. This will be a great help to me when I get started making my own missions. Thread subscribed.

Projectors Move As I expected, using the projectors and screen over the longer term is revealing issues to be dealt with. One thing I noticed is that fairly often I have to realign the image in Immersive DisplayPro. It seems the projectors move a little bit. I'm not sure what's the culprit but I have a few ideas. I decided to just started fixing them one at a time until I get it to stop moving over time. The first thing I tried is to stabilize the mount itself. The projector mounts I use have a safety mechanism that makes them easy to mount. There are two tabs so when you push the projector up into the mount, the tabs will hold it in place while you put two screws in from either side. The screws keep the projector from moving in that axis, but the axis with the tabs allows for some movement. In the picture below you can see where I've drilled a hole next to the tab and put a self tapping screw in. With this screw in place, it stops the movement in that axis. I'll use it this way for a while to see if it stops the movement. Otherwise, my next thought is that the wood frame may be flexing and need some re-enforcement. In an earlier post I mentioned that the velcro I used to attach the screen material came loose from the backer board. So I used super glue to reattach it. That didn't last very long. Now I'm considering to either use a staple gun to hold the velcro to the backer board, or just give up on it altogether and permanently attach the screen material to the backer board. More on that after I decide how to approach it.

Very nice!

Outstanding! It looks like real professional quality work, and a ton of it. :thumbup: Thanks for sharing your journey. Looking forward to your Hornet pit build. :music_whistling:

Directional Gyro Here's how I got the directional gyro working. As you may recall from an earlier post, I bought original (non-functioning) gauges from ebay and will modify each one for my simulator needs. I'm finding it interesting to see how the original gauges worked by taking them apart. (Before hacking them up to put in place stepper motors!) Here's the directional gyro: In the airplane, you would turn the knob to set the correct heading while on the ground. From then on, the gauge will show your heading as you fly around. The internal gyro is the key. The gyro is essentially a heavy spinning thing mounted on an axis. When spinning, the gyro wants to hold its position. Inside the gauge, the gyro has a strip mounted on it that shows the heading degrees. Once the gyro is up to speed it doesn't want to move so when you change the heading of the plane by initiating a turn, the case and the entire airplane move around the gyro. Since you are in the plane and your reference moves with the plane, it looks to you like the heading strip is the part that's moving. Here's the gyro, removed from the assembly. It spins by a stream of air fed through the gauge and blows across the gyro fins. Here you can see the frame that holds the gyro with the heading strip on it. The gear on the bottom is how it turns when you manually set the heading. The heading knob has a gear that when pushed in mates with the gear on the frame and allows you to manually rotate the heading/gyro assembly. My design is to have a stepper motor drive the gear and spin the heading gauge based on the heading of the simulated plane. I need the manual setting function to work so the design includes mounting a switch that will be activated when I push or pull the knob to rotate the heading manually. The switch will trigger a relay which will disengage the stepper motor allowing the heading strip to spin freely. (Much as the mechanical setup used to disengage (cage) the gyro when you wanted to manually spin the heading strip.) The picture below shows the completed assembly with the top half of the new back shell removed. If you look closely, you will see the motor mounted in the center geared to the gyro/heading assembly. To the right of that, the blue and black wire run to the cage switch on the front. To the left of the motor is a reed switch and you can just make out the magnet that triggers it glued to the bottom of the frame where the heading strip is mounted. This is the inside of the case. I've mounted a switch to the original knob/gear mechanism. Here is the knob mechanism removed so you get a clearer view of the switch and my fancy 3D printer work. It's a little difficult to see but when you pull the switch, the gear moves back towards theframe and causes the black plunger to push against the lever of the micro switch. And finally, the back of the gauge all closed up with the new backshell and circuit board for the relay, fly back diodes, connectors,etc.

Still not sure how I got that one approved. :music_whistling: I decided "if I don't ask, I won't get". So I asked and she said OK. The frame is a diameter of 8 feet and 7 feet tall. The screen is 64 inches tall. In retrospect, I would not mount the screen right at the top of the frame. I would mount it a few inches lower (maybe 6 or 8 inches). This would give a steeper down angle for the projectors, reducing shadows cause by the front of the pit. It is movable, but I wouldn't call it portable. It is constructed in three sections that are bolted together. Each section is about 48 inches wide by 7 feet tall. The screen material is a single piece, held on with Velcro. So it can be moved to another room by pulling off the screen and unbolting the three sections.

Thanks for the Updates A while back, there were a bunch of complaints on the forum about lack of information on work in progress. I'd like to thank ED as in recent weeks, I have noticed a significant improvement. The weekly newsletter now contains WIP in addition to information about sales and pre-purchases. Also I notice quite a few more posts from ED reps showing screen shots and work in progress. I now look forward again to the weekly newsletter to see the snippets of things to come. :thumbup:

Main Instrument Panel Mock-up I finished the MIP with yellow tape and some temporary stands. The yellow tape shrunk after I applied it so now there are gaps between the pieces. I may redo that but for now it's good enough. With this setup, I can begin to see how all the pieces should be in relation to each other. For example, the stick sits about 2 to 4 inches too high. Next step: start getting the gauges functional.

Sorry for a dumb question but what are speedtrees? Sent from my SAMSUNG-SM-G891A using Tapatalk

MIP Update This weekend, I cut the mounting plates for the artificial horizon and directional gyro. I cut the mounting plates out of 1/4” HDPE plastic. These cuts came out a lot cleaner than the MIP. Maybe my1/8” mill is sharper than my 1/4” mill that I used to cut out the MIP. The hole for the horizon is a bit big. I mixed up “inside left” and “outside right” on the CNC. It fits but I may cut another one with the proper size hole. I ran out of screws so the gauges aren't properly mounted yet. More screws on order, along with yellow tape to outline the primary flight instruments. Then I'll build some legs to temporarily mount it in front of my stick so I can fly as I start making the gauges work.

Progress on the Main Instrument Panel As you may remember, my pit will be loosely based around the P-51. I modeled the main instrument panel from aircraft drawings (shout out to http://www.aircorpslibrary.com ) then made a cut pattern for CNC. I started with a piece of 7/16” thick black plastic and ended up with this. The CNC left a few hairy bits. Maybe I don't have the right spindle speed for this material. I cleaned some of it up with a knife. Most of it will be covered by instrument bezels anyway so I'm not going to obsess over it. The next pic below is with the gauges installed for a test fit. Next I will make the mounting plates for the artificial horizon and directional gyro. Then the yellow outline for the primary flight instruments and it should be just about complete. (Except that none of the instruments work yet! :joystick:)

Screen Update Wow, work is keeping me crazy busy but here's a quick update on how the screen is working out for me now that I've used it a bit. As far as performance, it looks great and is quite immersive. Two areas I need to address though. The Velcro strips are coming loose from the back board. Although at first the self adhesive was quite sticky, after a few months it started to come loose. I glued a section of it using super glue gel and am watching to see how it holds up. The projector mounts move just very small amounts, but it is enough that from one session to another I often have to do small re-alignment in the Immersive Display warping software. It only takes a few minutes but I need to look for a way to make the mounts more stable.