Thanks that's very helpful. Gotcha. Well I'm trying to use my brain (what little there is). I was curious if there was any way to figure out how much trust you need to efficiently carry a certain weight. For example, I come from an automobile background where I drag raced for almost 20 years. I could easily figure out it would take x horsepower to go x mph at x weight. I would think that there would be something similar for Multirotors too. I'm still fairly new to all of this so that's why I ask all these questions. Good to know. Good point. That makes me think that this motor might be a good motor where you can stay maximum efficiency with the motor by just changing the prop depending upon GAW. It's nice to have a really good discussion on motors and to hear different opinions.
Dave, you know I like the Avrotos. Jim's post makes me like them even more. My average payload, now that I'm flying a much heavier 3-axis brushless gimbal, is in a range of 5.5kg. Copter AUW will be around 11kg-11.7kg. I think the Avrotos will work well. I'm now a little concerned about the wonky thrust issue using the 12c converter...something you mentioned some time ago. I think ultimately if I see any issues I'll just mask it by raising the mixer values a little, just to get a nice hover at around 50% throttle input
Dave use ecalc to do comparisons. Unless you want to buy lots of motors and build a thrust test stand and do lots of research.
So.........I went through Ecalc with 4 of the most popular Tiger motor selections and plugged different values in for weight, and prop size to see the affects. Very interesting data to see how each motor responds to the changes. I wanted to share my findings with this forum. If the throttle at hover was over 80% I didn't even bother entering the data, not that anyone would chose a motor that takes 70% throttle to maintain a hover either. I'm glad I went through the data as I learned a lot.
No problem!!! Let me know what you think you are going to do. I'm thinking the 4012-9 will work the best because it gives the most flexibility for efficiency by allowing you to change prop size for different GAW's.
This is all very interesting stuff. Now I'd like to see you guys continue this discussion to the "beyond" part. I already get 10 minutes flight time with a 5dm2 on a stock Cinestar 8 - no heavy lift needed. This is plenty of flight time in my opinion for this weight class. You guys are talking about 9-10kg, but the next camera weight class, in my opinion, is moving right on up to fly a RED. Lots of people are doing this already of course with the motors that have been available up to this point. But they're generally flying them stripped to bare minimum, restricted to lighter EF lenses etc...and flight times are not great. If you're going to be lifting RED-sized cameras, then you are talking about commercial jobs. So wouldn't you want to be prepared to carry them fully kitted with proper glass and follow focus etc...? That puts you in a much higher weight class than the 9-10kg class that you are talking about here with these 4012 motors etc... Flying a fully rigged RED camera yields an AUW of 14kg (30lbs) or more. As an aside I think all these pro rigs should be designed to carry an extra 5 lbs above that - in the form of an instant-deploy rocket-propelled emergency parachute ( that i hope someone invents soon ) as a matter of safety for carrying $50k worth of hardware, not to mention safety for humans on the ground should something go wrong. This is something I think the U8 will be able to do with ease, just trading a fews minutes of flight time for safety. So...you're getting ready to build a new machine, and today there's new motors out there like the U8. Aside from cost, what are the negative tradeoffs for going with something like the U8 motors?
I would like to see how the copters equipped with U8 motors will perform in windy conditions since we put on big props like 28"/29". One of the early adaptors of U8 motors, Ferdinand Kickinger, was complaining about this issue and he was not happy at all. He is using WKM.
Bryan your rig might be doing it but I guarantee its not doing it efficiently. If you try hovering your setup your motor temps go through the roof. For me extra flying time means the difference of shooting an extra shot on a set of batteries or not. It can also mean the need to have less batteries on a job, and less time changing batteries which is less time on a job. Bryan look again at the specs. The 4012-9 480KV motors are getting the job done up to 12 pound payloads which is way beyond the 9-10kg point. QC has tested them up to this point and are getting 12 minute flight time with a 12 pound payload and one battery. The Averto 3520's can even fly more payload than the 4012-9's. How do you plan on using a follow focus up in the air? You can also get really good glass that doesn't weigh anything more than a normal EF lens. Bryan its inevitable for crashes and those that are flying the heavy investments take that into consideration. Again the "pro rig" that I am building right now will be able to carry 10 pound payloads with an all up GAW of 22 pounds and I'm most likely using the 3520's. Right now I"m still debating the 3520's or the smaller Averto 3515 400kb's.
Been done, although they’re very, very pricey, and there has been much conversation as to their value and effectiveness. http://www.marsparachutes.com
How are you measuring efficiency? Not challenging you, just seriously asking because I dont know how to do it. My machine hovers at 65% power and motor temps a minute or two after landing are 100-120F. Yes, we all would like extra flight time, of course. I guess I'm not reading your graph correctly. The highest weight spec'd on the graph is 10.8kg with around 7 minutes flight time. People are already flying and using follow focus rigs NOW because the clients want it. If you want to be competitive in the top end of the field you need to be as flexible as possible regarding your payload. Many commercial clients are as particular about the glass as they are about the cameras you can fly. We can all argue about whether they "need" a RED, or "need" a certain lens, but it doesn't really matter. The competent operator who can handle the heavier payloads are going to get the top jobs. MALFUNCTIONS are inevitable - crashes maybe not. That's exactly my point regarding the parachute. The technology already exists on a larger scale for small planes and ultralights. It just has not been adapted in a lightweight enough package yet for our machines - though maybe soon (Photohigher). I tested the Mars Parachute system which was a good effort, but even as a non-techie, I immediately saw that there were huge improvements to be made in terms of weight savings and deployment method. To restate my point...you are building a new rig right now. I am doing the same thing. So, taking all these factors into consideration - weight, motors available today, size of the rig, and potential clients, I'm trying to find the sweet spot. The machine I built 6 months ago is already obsolete. I don't want that to happen again. In my opinion building a machine around a 10 pound payload is obsolete from day one. I'm building a new machine because I am getting requests to fly a RED. A 10lb RED payload is a stripped down bare minimum that you can get away with in terms of lens choice, no follow focus, etc...Why do I want to go through all the expense and cost to only be able to fly the bare minimum RED package?
Holdff on that purchase, a new slightly higher KV 3520 is being tested now...something in the range of 450-480 which is a great!
Bryan put the data for the 2814-11 in Ecalc and you will see that its way over in efficiency for density altitude's. High motor temps are an indication of inefficiency but again where you are flying effects it. What might be efficient for someone in San Francisco might not be efficient for someone in Denver. Take a look at the chart for 16" props at a GAW of 26 pounds. It looks really efficient to me at that weight. I wasn't disputing that a follow focus will help, my question to you is how do you plan on adjusting the follow focus in the air?
I haven't seen any wireless follow focus. At our school we just use the manual Red rock units that the operator adjusts manually. Cool to see that there's wireless units out there.
I had to look them up too, Dave. Google: wireless follow focus Looks like Red Rock is quite a popular unit. Andy.