I'm getting closer to gathering all the components for the 140C, but am hitting a budget wall. If you'd like to support the show/USA trip, I've put some of the remaining items I need for "sale" on my website, or really a way to donate/support the trip.
I have to emphasize, I'm offering it as an opportunity if you'd like to help. We're still friends if you can't or don't want to : )
Direct link to Help Raptor 140C: http://store.mygeekshow.com/category-s/1819.htm
Learn more about the Raptor 140C: https://www.youtube.com/watch?v=lRGbDmPCoeQ
Watch the most recent USA Trip Update: https://www.youtube.com/watch?v=DIF1J4VfY9s
If you don't want to pick something specific, you can go to: http://mygeekshow.com/donate/
Thank you for your 2+ years of support! We're getting closer...
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The Raptor 140C funding project is completed! You donated over $600 in 24 hours! I've ordered all the components for the 140C, and will keep you updated often on it's progress. Thank you! Thank you! Thank you!
If you couldn't or didn't want to donate, THAT IS FINE. we are still friends! Thank you for watching and supporting through your comments. They are what keeps the show alive. Thank you.
Hugues: Sorry for any confusion! I'll make sure my wife doesn't read your comment : )
As of right now, everything has been taken care of except 9 NCR18650B batteries: http://store.mygeekshow.com/product-p/140c-li-ion-cell.htm
Thank you for your support and patience!
Justin: That is a great idea! I've considered doing that, and in a way, I do a bit of that today as I fly about 300-400km a week, and am doing more and more cross country flights. So far, all the components have held up nicely. I will be replacing some of the parts each day and as needed. I plan on taking 3 airplanes, just in case. What would be cool would be to load a tlog into the APM and "trick" the apm into flying that course with everything connected. Essentially, you be flying that path (would need a fan to keep cool/simulate airflow) and would be a good tool to test durability.
Marius: That would be great! Give me some time to do some testing for what Kv/voltage/prop pitch works, and then we can pick up a nice motor.
Andrew: I need to show the analysis I do for each flight, its pretty in depth. Unfortunately, I've purchased two airpseed sensors, but each of them are just way off, one of them shows at least 20-40kph over (its not consistent) and the other just goes all over the place. I spent a good many hours trying to get them working, but as I can essentially get the same result (not perfect of course) by just flying a lot, then I can come to some conclusions. (aka, it draws about 12A to cruise at 80kph) I'm hoping that this new digital airspeed sensor (I haven't seen it on the 3DR store yet?) will provide accurate airspeed info, that would be awesome for sure.
Hi Trent, so what equipment do you need still? (Items you need You do not have but are for sale and out of stock is a little too complicated for my brain tonight). you must have a woman's brain to not say what you need but that we should understand, lol.
So make an explicit list, hoping I can help you in an humble way.
Marius - Efficiency in this case is thrust power / electrical power.
Electrical power is relatively easy to measure - DC volts x amps in this case.
Thrust power is more difficult and changes with airspeed, but fundamentally it is a product of motor efficiency and propeller efficiency. Zero airspeed thrust (i.e. bench testing) is completely irrelevant as this is never used and it bears little relation to total efficiency in cruise - where Trent is most interested.
Note though, for the quadcopter guys, the story is completely different because zero airspeed thrust is where they need to be most efficient, so bench testing makes sense.
The most accurate way Trent has to measure propulsion efficiency is to monitor his electrical power w.r.t. true airspeed at standard atmospheric conditions - or data corrected to these conditions. If Trent were being rigorously scientific, he could do this flight testing logging data with the APM. Perhaps there's a couple more MGS episodes to be had here before he leaves for the West Coast?
Of course airplane efficiency is different from the individual motor efficiency. But since most characteristics of the raptors flight are locked in (design, weight, and cruising speed). There are 2 mayor things left to increase efficiency. One is centre of gravity, but Trent has already optimised this. And secondly the motor/prop combination.
A tiger motor can be less efficient than a Turnigy motor depending on the setup of both. Most efficiency curves are bell curved shaped, meaning you need to "hit the sweet spot". If all motors would be designed the same there would not be such a price and weight and Kv range.
Andrew, what would you consider to be a scientific measure of efficiency?
Efficiency in layman's term is "bang for bucks". There is no more scientific way express efficiency as grams (bang) per watt (buck) in this situation in my opinion.
Efficiency in any motor is a bell curve with an optimum performance range for each motor. Turnigy does not publish its efficiency range (wonder why :), but when people test it they find it to be around 5 gr/W
http://www.rcuniverse.com/forum/brushed-brushless-motors-speed-cont...
If you compare that with a more expensive motor (not really specific to tiger) you will see that efficiency is much better (especially in the lower rpm range). The reason why I need to know how much thrust he needs in cruising speed, is because this will affect which motor runs more efficient.
4x more efficient is outside the practical range (as this is for very slow rpm), but 2x more efficient is doable.
Marius, Are you really saying your Tiger motors are four times as efficient as a Turnigy? If so, I wonder why the Turnigy's are not melting during use, because that's a lot of power going nowhere!
(apart from the fact that g/W isn't a very scientific measure of efficiency...)
I can sponsor you a motor, but you can almost double your range with a more efficient motor. Turnigy does not publish it efficiency for your current motor, but when other people have tested similat models they get 5 gram/watt at best. Tiger motors can easily do 10 gram/watt and can go as high as 20 gram/watt depending on load.
If you can calculate his many grams of thrust you need I can recommend/sponsor you a high efficiency motor.
Keep up the good work. Marius
Trent,
You may want to take one of the motors and servos etc. and set up a static endurance test, estimate how long your motor is going to run for on the trip then have a bench power supply run the test motor for at least that long. This will tell you hopefully how many extra motors you should take with you, similarly you could put a load on a servo and have it continuously move back and forth to find out the replacement interval for those servos. I would also consider building multiple aircraft and taking them with you just in case.
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