Winter Build 2019-2020: Top Flite P-51 (0.60 size)

[willsonman]

I read all of your stuff. I usually dont comment as my questions are not so real world friendly as I don't think like others. For the most part what you do and put out is detailed enough not many questions arise other then ones on the unusual stuff or me thinking of a possibly different way to do it.

Bottom line is if you want interaction build in lures and lead people to ask them. Specially on important things you want to high light in a particular build / video / thread. That or be far less detailed so others have to ask to see the magic behind the curtain hehe.

The world needs more folks who do not think like the rest of us. My son is very much this way but unfortunately far to many folks like him do not fully think through the ideas before getting involved. They waste time and effort on a pursuit and end up feeling like failures but never learn too much from that experience. The ideas are great but the end result is what matters. If you can't get there, make a plan to do so or work with others to WORK THE PROBLEM. That's why we have a community. This is exactly how I got my pressure sensor done. I had an idea and thought through the problem but I did not have the skill set to complete it. I worked with two very skilled people to get ADVICE and GUIDANCE but I DID THE WORK.

Lures and leading people on is straight up manipulation for self-aggrandizement. Look, I'm an open book. If you want to question me about something I do just ask. I'm not here to play into the psychology of people, I'm here to openly share my skillset for others to "up their game." This is how the hobby has been passed down for over one hundred years now. If I'm not fully transparent then that does the onlooker a disservice by not being allowed to think for themselves and ask a more intelligent question than what could have been asked if they were "behind the curtain." That being said, there are times when I have not covered something in as much detail as I could have. That's totally fine and I am HAPPY to go back and cover it in more detail. Back to 2015 Flite Fest on the Sikorsky: Many times I was interrupted in the build by onlookers wanting me to show them how to do a hot wire cut with a bow. NOT ONCE did I refuse that moment of sharing and teaching. Seriously, just ask.

 

[TooJung2Die]

Good explanation of Sbus. I got interested in it because many Sbus output receivers are TINY and I like to build small. I'm always looking for ways to save weight (grams). The problem I see for my builds would be converting the Sbus to PWM to drive the servos. As I understand it that requires an Sbus to PWM convertor or flight controller board. There goes any weight saving and it actually complicates the electronics and wiring. Is my understanding flawed?

 

[willsonman]

As someone who admittedly usually just "jumps in" to projects, at least with less prep than you're describing, I take ZERO offense at your assertion that that method "sucks".

The monster B-52 was actually a really good experience for me in that respect: even though it was a SUPER compressed timeline - completed in 3 days - it never would have happened had it not been for almost a year of planning and prep, to say nothing of all the teamwork required to actually execute in the time required!

I love following you Josh. I know I don't interact a lot on the forums anymore, but I love following you because I learn something new just about every time. Keep it up dude.

That's really what it's about. The learning and iterative process. I'm having such a blast learning on this project and I think we have only just scratched the surface of the motor setup. Once it is mounted on an aircraft and we can start getting some real power and thrust numbers, things are going to get very interesting. This is sort of my point.

I've come to a point where I plan to build a particular subject I really don't have any feeling for. Everyone and their dog has a Mustang and quite frankly, the history is not all that interesting either. No drama, no major teething issues once in service. It was just build and did it's job and it's job never really evolved that much. It's pretty-ish but not in an interesting way. Sure women who model a attractive on the surface but not in a way that makes me want to start a conversation. Maybe that's just me.

At any rate, the subject is a facilitator of an aspect of flight that is complicated, new to me, exciting to me, and frankly the wow factor to everyone else is just a bonus. Like I've said, the intent of this model is from 6 feet away to have it be a very understated model. It is a strong focus that will become very evident as the time comes. It will no-doubt be a conversation piece to facilitate talking shop at events, but something else is intended to be the focal point and I will not upstage that. I'm not at liberty to say more. Needless to say this has been in planning mode for some time.

Ben, your ability in this hobby is amazing. There is no question of that. I have no doubt that the hobby will take you and your son down some amazing roads that will lead to some spectacular memories. Keep that in mind... your ability will make, and has made, memories. The things we learn are making memories. I hope a lot more people can make that connection.

 

[willsonman]

Good explanation of Sbus. I got interested in it because many Sbus output receivers are TINY and I like to build small. I'm always looking for ways to save weight (grams). The problem I see for my builds would be converting the Sbus to PWM to drive the servos. As I understand it that requires an Sbus to PWM convertor or flight controller board. There goes any weight saving and it actually complicates the electronics and wiring. Is my understanding flawed?

No, you just need to get the right servos to save that weight. Just keep in mind that the SBus accessories and servos and such are NOT CHEAP. Saving weight does not save cost. However, there are items out there that may be of interest. The Futaba SBus decoder (SBD-1) can use a long SBus line and decode for 3 PWM servos. There are also DIY options out there too for SBus but that's a bit beyond my skill set. Still, if you are interested, it may be a rabbit hole worth going down.

 

[TooJung2Die]

Your airplanes are at the opposite end of the spectrum from what I build, size-wise. Sbus servos all seem to be large. I think the smallest Sbus servos are approaching the 9 gram size. 9 gram servos go in my big airplanes where weight is not the issue. You're correct, building small does not always mean building cheap! The really light weight stuff is pricey but worth it if your goal is shaving grams.

 

[Chuppster]

For some builders, their plan is to just dive right in and get to work. That plan sucks.

The thing with these kinds of massive projects is unforeseen roadblocks as well as the inevitable "burnout" that happens. road blocks can be a simple as not finding something you know you have or not knowing you need something and it takes 6 weeks to ship to you. During those 6 weeks you are stuck with no progress being made and your project then gets stalled because you get used to NOT working on it... even just a little bit. Burnout just happens when it happens and you have to dig deep to know yourself, your limitations, and when/how to step away to recharge.

I've been making build plans ever since my 2015 Sikorsky S-39 build. I built a scale 72+ span airplane from scratch to flying in 51 hours over 3 .5 days. How? a year's worth of planning. I had every part, every tool, every sequence of the build planned and ready to execute. It was a great lesson and one that I now keep to. This time last year I was in that planning mode. I did not want to start the actual build until I had a functional prototype of the constant speed/ variable pitch prop. The Mustang, as a subject itself, is really not that appealing or interesting to me. It's not a challenge to build either. I've done these Top Flite kits before. The idea was that I'd get the base challenge off the ground and primed for a fun end-goal. The other minor projects, like the above pressure sensor as well as other current background items, were to be small side projects to combat burnout.

So, what's the plan now? Well, the same as before but I've taken time to refresh it. I have a few other airplanes I've acquired over the course of the last 6 months that need painting details completed and frankly those will be a welcome distraction when burnout happens. I'll stay productive but see a new subject, different materials, and be able to take a break and be able to come back to the Mustang with fresh eyes and renewed motivation. Plan for items with easy and tangible gratification. The Fokker D.VI needs crosses and nose art. The Durafly ME-163 Komet needs paint and minor details... maybe a rocket ignition system. My MXS-R70 needs landing gear re-build (again). The FW-190 needs panel lines and paint. There are plenty of things for me to do and chose from as I see a need to recharge.

As for the plan itself, some additional parts are arriving as I have evolved the project from its original intent. To be fair, the objective of this build is to NOT be showy or flashy. I want it to be a bit understated so I'm not going crazy with sliding canopy or animated cockpit controls. There are no cowl flaps to move. There is ONE vent flap that I will do and gear doors. Cockpit will be detailed of course and a pilot, for sure.

Parts already on-hand:
Servos: had some help here from Horizon Hobby (more on that later)
Pneumatic retracts: Includes associated hardware required to function
Oleos and wheels
Tail electronic retract
Motor: includes some spare parts for the complex design
ESC
Receiver
hinges
glues/epoxy
fiberglass cloth
shop supplies: razor blades, towels, screws, nuts, specialty hardware like offset hinges

Parts due to arrive at this point are as follows:
FrSky Neuron 8A SBEC: I want the safety of a dedicated BEC separate from the ESC that will be doing work to govern the motor speed. The telemetry will be nice too.
RPM and dual temperature sensor: I need to be able to accurately measure and monitor the RPM for when it comes time to set the ESC governor as well as make changes to this based on testing results. Temperature sensor for the ESC and battery bay as all of this will be quite complex. Remember, this is essentially a helicopter setup in the nose of an airplane. Helis ususally have VERY open canopies to allow things to cool.
S.Bus to PWM converter: I have used these before. I like them for simplicity. The FrSky full-range receivers carry al 16 channels along with Smart Port data (telemetry) but unfortunately they have anywhere from 4 to 8 PWM outputs. This leaves at least 8 but up to 12 channels on the table. Those who tuned into my Top Flite Corsair build know that I used all 16 channels on that airplane. Let's cover that plan now.
Throttle
Aileron (X2 for differential if needed)
Elevator
Rudder/tail gear
Flaps
Main gear retract
Tail gear retract: needed due to endpoint adjustment differences between electric and pneumatic systems; doors to use mechanical closure
Main gear doors
Exhaust flap (may be able to slave to throttle position, needs more reading and research)
Lights (easy addition that does add depth to the model)
Ordinance drop (maybe, easy addition but may not bother)

That adds up to at least 12 channels. The converter takes all 16 digital channels and breaks them out to a PWM signal with pins for each channel output. It saves a little bit of $ as well as they are generally $10 cheaper than a receiver. Yes, I still try to stick to a budget on these big builds. As it is, I've already got about $600 into this project for those who would like a sense of cost.

So there you have it. Disagree if you want to but you can't argue with the efficiency of this extensive planning. Of course life happens. Like my move that stalled this project, which is why I stalled it the way I did. I did not want to come back to it until I had an adjusted plan for the new shop. My point here is to again reiterate that big winter builds can be just that, winter builds... not multi-year endeavors with multiple stop-starts that kill momentum. Make a plan and fully commit.

I'm with @rockyboy on the plan-as-you-go thing. I really don't enjoy sitting down and thinking too much about a build, so I typically wing it. However, I usually have a project list about 10 airplanes long. If something stalls, order what you need and push it back on the list until the part shows up (or you find it at a swap meet). Then again, I rarely hyper-focus on a scratch build. Most of my "building" is restoring old and forgotten airplanes. However, if you are in a time crunch for a project to get done, I can see the value of in-depth planning.

 

[willsonman]

I'm with @rockyboy on the plan-as-you-go thing. I really don't enjoy sitting down and thinking too much about a build, so I typically wing it. However, I usually have a project list about 10 airplanes long. If something stalls, order what you need and push it back on the list until the part shows up (or you find it at a swap meet). Then again, I rarely hyper-focus on a scratch build. Most of my "building" is restoring old and forgotten airplanes. However, if you are in a time crunch for a project to get done, I can see the value of in-depth planning.

That's all well and good. A restoration, I recently found, requires a bit of a different approach. The 1/4 scale Tripacer restoration I did this year was fraught with all sorts of unexpected shoddy construction under the tattered covering. In that project, I took the stance of tearing everything apart and knowing what was going to be problematic and plan from there. The biggest delay there was actually with shipping of the new plastic for the windscreen. It was shipped out of a place just north of Philadelphia, just a short 3-hour drive away, with 2-day shipping. It took two weeks to arrive. You just cannot plan for that.

I also will say that restorations are highly underrated! There is so much instant gratification to be had there along with not having to do the majority of the initial work. There are certainly headaches and moments of "why on earth would you have built it that way" but overcoming those moments are also gratifying. It is certainly a process I would highly recommend for those with shorter attention spans or those who are less prone to stick building.

 

[tamuct01]

Josh,
Which SBUS to PWM converter are you using? I've used a couple purchased from Amazon that came from China, and they work well, but I found that the signal is "compressed," for lack of a better term. The issue I've seen is this: A servo connected directly to the PWM output of the receiver (I use FrSky) gets the full -100/100 travel. The same servo connected to the same channel, but via the SBUS converter only yields about -80/80 travel. Have you seen this as well? What is your workaround?

I love the builds! Keep them coming!
--Brian

 

[Chuppster]

That's all well and good. A restoration, I recently found, requires a bit of a different approach. The 1/4 scale Tripacer restoration I did this year was fraught with all sorts of unexpected shoddy construction under the tattered covering. In that project, I took the stance of tearing everything apart and knowing what was going to be problematic and plan from there. The biggest delay there was actually with shipping of the new plastic for the windscreen. It was shipped out of a place just north of Philadelphia, just a short 3-hour drive away, with 2-day shipping. It took two weeks to arrive. You just cannot plan for that.

I also will say that restorations are highly underrated! There is so much instant gratification to be had there along with not having to do the majority of the initial work. There are certainly headaches and moments of "why on earth would you have built it that way" but overcoming those moments are also gratifying. It is certainly a process I would highly recommend for those with shorter attention spans or those who are less prone to stick building.

I love restorations because they are quick and cheap way to get in the air. The only time I really get frustrated is when someone fixes crash damage crooked. I don't think there's any excuse for that, and I have to do a ton of work to cut their "repair" out and make it right.

 

[willsonman]

Josh,
Which SBUS to PWM converter are you using? I've used a couple purchased from Amazon that came from China, and they work well, but I found that the signal is "compressed," for lack of a better term. The issue I've seen is this: A servo connected directly to the PWM output of the receiver (I use FrSky) gets the full -100/100 travel. The same servo connected to the same channel, but via the SBUS converter only yields about -80/80 travel. Have you seen this as well? What is your workaround?

I love the builds! Keep them coming!
--Brian

In the past I have used the RMILEC one but I've recently decided to try the QwinOut one for this project. I've not noticed any limitations to travel using the RMILEC version in the past.

 

[PsyBorg]

The world needs more folks who do not think like the rest of us. My son is very much this way but unfortunately far to many folks like him do not fully think through the ideas before getting involved. They waste time and effort on a pursuit and end up feeling like failures but never learn too much from that experience. The ideas are great but the end result is what matters. If you can't get there, make a plan to do so or work with others to WORK THE PROBLEM. That's why we have a community. This is exactly how I got my pressure sensor done. I had an idea and thought through the problem but I did not have the skill set to complete it. I worked with two very skilled people to get ADVICE and GUIDANCE but I DID THE WORK.

Lures and leading people on is straight up manipulation for self-aggrandizement. Look, I'm an open book. If you want to question me about something I do just ask. I'm not here to play into the psychology of people, I'm here to openly share my skillset for others to "up their game." This is how the hobby has been passed down for over one hundred years now. If I'm not fully transparent then that does the onlooker a disservice by not being allowed to think for themselves and ask a more intelligent question than what could have been asked if they were "behind the curtain." That being said, there are times when I have not covered something in as much detail as I could have. That's totally fine and I am HAPPY to go back and cover it in more detail. Back to 2015 Flite Fest on the Sikorsky: Many times I was interrupted in the build by onlookers wanting me to show them how to do a hot wire cut with a bow. NOT ONCE did I refuse that moment of sharing and teaching. Seriously, just ask.

This is what I mean by I dont think like others... I must not speak English er some . This was meant to be a compliment on how well you teach and show things. I did not mean YOU lead people in anyway. I am just saying if you wanna get todays cookies cutter kiddiots to learn you have to have bells and whistles and contests and giveaways before they actually participate in something. Other then that it boils down to Monkey see Monkey do. The goal is something for nothing. No money, no effort, no thinking. If something fails they get someone else to do the work or give up for the most part. Here most people are different as they come here to participate in the social aspect as this is one of the few places on the internet where things actually ARE social.

Even with my dumb newb questions or thoughts you have never not answered them. Honestly there has only been one time in what 6 years here now I have felt put out by you and that was over something not worth worrying about.

 

[willsonman]

we all disagree at some time or another. All good.

 

[tamuct01]

In the past I have used the RMILEC one but I've recently decided to try the QwinOut one for this project. I've not noticed any limitations to travel using the RMILEC version in the past.

The converter that I have looks just like that QwinOut version. Let me know if you see the same servo output difference that I did.

 

[willsonman]

Looking forward to more details on that sensor implementation! I've seen that open source sensor project before, but haven't fallen down the rabbit hole yet and would love to hear how it's like over there

I want to go into a bit more detail on this just for those who are curious. While I believe a video will be far more efficient and better to understand, I'll try to lay the groundwork for those so inclined to tinker.

The openXsensor project has been going on since at least 2013 over at the OpenRC Forums. Essentially these folks, primarily user mstrens, have compiled the sensor libraries and integrated the code for Arduino use. The linked website has the download of the latest version that you simply open in Arduino IDE software and navigate to the oXs.config.h part of the sketch. For those ENTIRELY unfamiliar with Arduino... You can open the entire sketch by navigating to the folder and open the openXsensor.ino file with Arduino IDE. Then the oXs.config.h tab will be at the top and you will likely need to use the drop down tool to navigate there.

A little bit more information here so we know what and why we are making changes to the code. I'll not cover basic connection and uploading of sketches as there are lots of tutorials out there for that.

The arduino will operate off the 5V receiver supply voltage however the Smart Port (FrSky) for telemetry is a 3.3V signal. Therefore you need a 5.6K resistor in line with the signal wire. Picked up a set of 5 at the LHS for $2. This signal wire will be solder to a digital signal pad that we will define in the sketch. There are a few of these on an arduino nano and I used D2. For those electrically disinclined, there is no polarity for resistors so just solder it in line with the wire any way you want. Your + wire will be soldered to the VCC pad and - to GND or ground. This is just to get the arduino powered and potentially talking to your receiver. The digital pad you solder to must now be selected in the sketch under oXs.config.h. Line titled "2 - Serial data pin choice" is pretty close to the top and I used pin #2 as it was closer to the end of the board for my purpose but you can use whatever you want as long is it does not conflict with other default signals from the sketch. I believe D2 and D4 are available by default and it seems that D2 is the default that comes with the download. Save your selection and then write the sketch to the arduino board.

So, now you can connect the arduino to the receiver, turn on your transmitter, power up your receiver, and you should be able to navigate to the telemetry page in your transmitter and discover the new sensor. It should automatically be detected.

For the pressure sensor I had a few constraints to consider when selecting what sensor I wanted to actually buy. I'm working within a 5V system so an operating voltage (nominal) is one. I need a pretty high operating pressure but to what point? Normal operating pressure of a retract system is around 100psi. To factor environmental conditions I figured a max of 120psi. This means, that should I charge the system with air and the airplane sits in the hot sun, the air may expand due to heat which will increase the pressure in the system. Now I need an overhead and based off of higher pressures available from manufacturers 150psi was selected as those were the only option. That said, I selected this sensor. That's right, $38 for one little sensor. By comparison, I got my entire arduino board for $6. The data sheet is critical here as it provides information for you to figure out what pin to solder where. I'll note that while there are 8 pins on this sensor, only 3 are active and used. There is a ground, power, and output pin. The output is in voltage between 0 and 5V that correlates with pressure. There is also a transfer function sheet that includes the math associated with the expected output.

From here we wire the ground and positive wires from the arduino... same ones that are powering it... to the sensor itself. Then wire the output pin to an analog pad on the arduino. I used analog pad 7 (A7) because again, it was close to the one end of the arduino so it made the package a bit neater for the final assembly.

Back to oXs.config.h but now line titled "6 - Voltages & Current sensor settings" where we start with assigning pad 7 under section 6.2, PIN_VOLTAGE. Each number there is associated with different pins available separated by a comma. I changed the first number to 7. Now, each subsequent row I will only be changing the first number. RESISTOR_TO_GROUND and RESISTOR_TO_VOLTAGE should both be 0 as we have no further resistance to account for. OFFSET_VOLTAGE I set to 0 and SCALE_VOLTAGE I set to 1.0. These numbers we can and will play with in the transmitter. The last part to edit is is under section 6.1. This is the part I had to learn a bit about from @Craftydan. The voltage that is passed through is either referenced to the internal regulated voltage from the arduino or the VCC voltage coming from the receiver. You can use either one. Save and upload to your arduino board.

I did create a spreadsheet where I could use the equation from the sensor data sheet to spit out the expected voltage on the output given the pressure and input voltage. This is where things went a bit sideways as the raw voltage measurements from the sensor using a voltmeter were pretty much dead on +/- 0.02V which is within the precision of the sensor. However, no matter which way I used the reference voltage, I never saw on my transmitter what I saw on the voltmeter. Regardless, we can now move to the next step.

We should now be seeing some sort of reading on the transmitter with everything powered up. In the transmitter telemetry settings, make sure that no units are selected as there is no option for psi. We can not try to change the offset to get a zero reading with no pressure. Now, while applying pressure with a pump that has a gauge, we can modify the scale so that the pressure on the transmitter matches what is observed on the gauge. I used 40 and 60 psi as references. By the time I got to 100psi I was off by about 3psi but I figured that was acceptable since I'm just trying to get a rough idea of how "full" the tank is at that point. I only really need it to be accurate at around 60psi.

It's long, it's a bit dirty, but there you go.

 

[Chuppster]

I want to go into a bit more detail on this just for those who are curious. While I believe a video will be far more efficient and better to understand, I'll try to lay the groundwork for those so inclined to tinker.

The openXsensor project has been going on since at least 2013 over at the OpenRC Forums. Essentially these folks, primarily user mstrens, have compiled the sensor libraries and integrated the code for Arduino use. The linked website has the download of the latest version that you simply open in Arduino IDE software and navigate to the oXs.config.h part of the sketch. For those ENTIRELY unfamiliar with Arduino... You can open the entire sketch by navigating to the folder and open the openXsensor.ino file with Arduino IDE. Then the oXs.config.h tab will be at the top and you will likely need to use the drop down tool to navigate there.

A little bit more information here so we know what and why we are making changes to the code. I'll not cover basic connection and uploading of sketches as there are lots of tutorials out there for that.

The arduino will operate off the 5V receiver supply voltage however the Smart Port (FrSky) for telemetry is a 3.3V signal. Therefore you need a 5.6K resistor in line with the signal wire. Picked up a set of 5 at the LHS for $2. This signal wire will be solder to a digital signal pad that we will define in the sketch. There are a few of these on an arduino nano and I used D2. For those electrically disinclined, there is no polarity for resistors so just solder it in line with the wire any way you want. Your + wire will be soldered to the VCC pad and - to GND or ground. This is just to get the arduino powered and potentially talking to your receiver. The digital pad you solder to must now be selected in the sketch under oXs.config.h. Line titled "2 - Serial data pin choice" is pretty close to the top and I used pin #2 as it was closer to the end of the board for my purpose but you can use whatever you want as long is it does not conflict with other default signals from the sketch. I believe D2 and D4 are available by default and it seems that D2 is the default that comes with the download. Save your selection and then write the sketch to the arduino board.

So, now you can connect the arduino to the receiver, turn on your transmitter, power up your receiver, and you should be able to navigate to the telemetry page in your transmitter and discover the new sensor. It should automatically be detected.

For the pressure sensor I had a few constraints to consider when selecting what sensor I wanted to actually buy. I'm working within a 5V system so an operating voltage (nominal) is one. I need a pretty high operating pressure but to what point? Normal operating pressure of a retract system is around 100psi. To factor environmental conditions I figured a max of 120psi. This means, that should I charge the system with air and the airplane sits in the hot sun, the air may expand due to heat which will increase the pressure in the system. Now I need an overhead and based off of higher pressures available from manufacturers 150psi was selected as those were the only option. That said, I selected this sensor. That's right, $38 for one little sensor. By comparison, I got my entire arduino board for $6. The data sheet is critical here as it provides information for you to figure out what pin to solder where. I'll note that while there are 8 pins on this sensor, only 3 are active and used. There is a ground, power, and output pin. The output is in voltage between 0 and 5V that correlates with pressure. There is also a transfer function sheet that includes the math associated with the expected output.

From here we wire the ground and positive wires from the arduino... same ones that are powering it... to the sensor itself. Then wire the output pin to an analog pad on the arduino. I used analog pad 7 (A7) because again, it was close to the one end of the arduino so it made the package a bit neater for the final assembly.

Back to oXs.config.h but now line titled "6 - Voltages & Current sensor settings" where we start with assigning pad 7 under section 6.2, PIN_VOLTAGE. Each number there is associated with different pins available separated by a comma. I changed the first number to 7. Now, each subsequent row I will only be changing the first number. RESISTOR_TO_GROUND and RESISTOR_TO_VOLTAGE should both be 0 as we have no further resistance to account for. OFFSET_VOLTAGE I set to 0 and SCALE_VOLTAGE I set to 1.0. These numbers we can and will play with in the transmitter. The last part to edit is is under section 6.1. This is the part I had to learn a bit about from @Craftydan. The voltage that is passed through is either referenced to the internal regulated voltage from the arduino or the VCC voltage coming from the receiver. You can use either one. Save and upload to your arduino board.

I did create a spreadsheet where I could use the equation from the sensor data sheet to spit out the expected voltage on the output given the pressure and input voltage. This is where things went a bit sideways as the raw voltage measurements from the sensor using a voltmeter were pretty much dead on +/- 0.02V which is within the precision of the sensor. However, no matter which way I used the reference voltage, I never saw on my transmitter what I saw on the voltmeter. Regardless, we can now move to the next step.

We should now be seeing some sort of reading on the transmitter with everything powered up. In the transmitter telemetry settings, make sure that no units are selected as there is no option for psi. We can not try to change the offset to get a zero reading with no pressure. Now, while applying pressure with a pump that has a gauge, we can modify the scale so that the pressure on the transmitter matches what is observed on the gauge. I used 40 and 60 psi as references. By the time I got to 100psi I was off by about 3psi but I figured that was acceptable since I'm just trying to get a rough idea of how "full" the tank is at that point. I only really need it to be accurate at around 60psi.

It's long, it's a bit dirty, but there you go.

I love that they compiled an arduino library for FrSky telemetry. So many possibilities! I'd consider hacking one up for my Mustang if the sensor wasn't so darn expensive.

 

[willsonman]

Yep, that was the real downside. Being able to accurately measure pressure that high in such a small package drives up the cost as that is a lot of force you have to overcome. Still, all parts spent for the thing were $50 and that is insurance well-spent if it keeps me from ever having to make a belly landing on this model. Keep in mind that a belly landing on this would likely rip off and damage the lower air scoop and well as do a number on the custom prop assembly. It's also possible that the inner gear doors and main gear doors would get damaged on the bottom of the wing. It would be a pretty extensive repair. Worth the $50 IMO for that insurance but certainly worth it for the fun I had and the skills I learned in the process.

 

[Chuppster]

Yep, that was the real downside. Being able to accurately measure pressure that high in such a small package drives up the cost as that is a lot of force you have to overcome. Still, all parts spent for the thing were $50 and that is insurance well-spent if it keeps me from ever having to make a belly landing on this model. Keep in mind that a belly landing on this would likely rip off and damage the lower air scoop and well as do a number on the custom prop assembly. It's also possible that the inner gear doors and main gear doors would get damaged on the bottom of the wing. It would be a pretty extensive repair. Worth the $50 IMO for that insurance but certainly worth it for the fun I had and the skills I learned in the process.

Speaking from experience, I had a flight where I had air pressure but one gear was stuck up, so I was forced to do a belly landing. Somehow the only damage was the prop. So unfortunately there are a plethora of other factors that can lead to a belly landing, but the insurance should prove useful in the event of an air leak.

I'm glad I've got Spring Air in my B-25.

 

[rockyboy]

"However, no matter which way I used the reference voltage, I never saw on my transmitter what I saw on the voltmeter. Regardless, we can now move to the next step."

Help me out with this part a little more - are you saying the voltage data doesn't need to be sent to the transmitter because the sensor is sending some other data element to measure the pressure? Is the transmitter doing the logic of determining when the pressure hits the trip level, or is that in the sensor code?

Apologies for being dense - trying to follow this on a cell phone and might have missed something obvious.

Thanks!

 

[willsonman]

"However, no matter which way I used the reference voltage, I never saw on my transmitter what I saw on the voltmeter. Regardless, we can now move to the next step."

Help me out with this part a little more - are you saying the voltage data doesn't need to be sent to the transmitter because the sensor is sending some other data element to measure the pressure? Is the transmitter doing the logic of determining when the pressure hits the trip level, or is that in the sensor code?

Apologies for being dense - trying to follow this on a cell phone and might have missed something obvious.

Thanks!

So, in an ideal world I’d be seeing exactly what I would expect from the transfer function equation. If I did, I could re-arrange it and have the arduino do the match for me. It doesn’t so I can’t. Without scaling I’d see anything between -.05 - 4.75 or so volts. So, in messing around I just settled for now because it’s good enough. The voltage data is being sent but the voltage data sent has to have a reference... either from the arduino or the VCC which is power from the receiver.

The transmitter uses a logic switch to override the physical toggle switch of the landing gear but it has to know the right value from the telemetry data. I did something similar way back with my Corsair. The airspeed sensor logged data my first flight and I was able to roughly determine the stall speed. So I set an audio warning to sound when my speed gets too low for when I land. More on this programming later. I wanted to just cover the arduino and sensor first in one comprehensive post.

 

[willsonman]

Speaking from experience, I had a flight where I had air pressure but one gear was stuck up, so I was forced to do a belly landing. Somehow the only damage was the prop. So unfortunately there are a plethora of other factors that can lead to a belly landing, but the insurance should prove useful in the event of an air leak.

I'm glad I've got Spring Air in my B-25.

Yeah, something to worry about for sure. The “scale size” wheel is closer to 3.75-4” diameter but the oleos this size go to a max of 3.5” so I’m not too worried about tight fitment in my wheel well.