Posts: 5,903 Threads: 47 Likes Received: 2,785 in 2,247 posts Likes Given: 7,684 Joined: Jul 2019 Reputation: 97 09-Jul-2022, 12:51 AM (This post was last modified: 13-Jul-2022, 05:12 PM by iFly4rotors.) Hi Janz, Well, I am going to toss in my thoughts just to keep you thinking. You know, I have NOT yet tuned any of my quads; everything is running on the stock default settings as it has from the factory. I have literally run pretty much the same settings on builds from 4 inch to 7 inch with NO adverse affects. What I am saying here is that you probably won't have to change any settings or the tune to run 3 inch props on that rig. In fact, if you get an exact replacement GEPRC frame, try a set of 3 inch props and see if you can really tell much difference {except for the fact that the 3 inch props will have a less thrust due to the smaller prop area}. If I was looking for an alternate frame for a 3.5 inch quad, I would definitely be looking at a 4 inch frame which will handle the 3.5 inch props AND 4 inch props PLUS 3 inch props with or without prop guards {not that you want to, but it actually works quite well}. I think that a 4 inch frame would be the better choice. For me, any frame over 50 grams is too much for a sub-250 gram build. It just causes you to compromise somewhere else. There are quite a few 4 inch frames that are way less than 50 grams. Personally, I like RoninUAV frames which have a dual mounting setup and plenty of space in the frame and only weigh about 42 grams. Although you can find lighter ones, most 4 inch frames are in the 35 - 45 gram range. I think the GEPRC exact replacement frame weighs about 47-48 grams ??? I maintain a spreadsheet which contains a lot a lot of information with tabs organized by item or subject matter. There is a tab for each frame size, one for motors, one for batteries, and other stuff. I have added a new "Build Guide" tab in an effort to make it easy to plug in some of the weights and see what the AUW of the quad will be. You might find this spreadsheet interesting especially for comparing components. It is a challenge to keep it updated with the most recent information, but I do try. Anyway, Click to download --> Parts Guide. Posts: 4,731 Threads: 392 Likes Received: 3,231 in 1,827 posts Likes Given: 3,214 Joined: Apr 2019 Reputation: 101 Just chiming in here cos I was saying the same thing on Lemon's thread. I used the same 1404s and same tune / filtering on a 3" and 3.5" variant and it flew great. The half inch makes a material difference in throttle authority but didn't seem to require any additional rejigerring of tune. Posts: 155 Threads: 15 Likes Received: 36 in 25 posts Likes Given: 2 Joined: Jan 2022 Reputation: 0 Thanks for all the suggestions guys, greatly appreciated and will keep my brain moving. This winter I think we will look into either building a replacement quad for the current Smart35 or we will swap frames and use all the components from the 35 for the build. Our summers are short enough, I didn't want any lengthy down times as we sort out a new frame and getting everything swapped over. Its more important right now to get as much seat time as possible, have fun and keep progressing. The one piece bottom plate from a beginners standpoint leaves a lot to be desired. Although, it only took me 20-30min to swap everything over and re-calibrate the accelerometer. The big issue I have is that we are so close to the 250g limit that we have no room for any sort of accessory. Id love to put some printed arm skid plates on or a small bumper to protect the camera. We would have to give up some battery size to make room for anything at this point. Its just nice having the power and flight time that these 4s 850mAH batteries provide. • Posts: 5,903 Threads: 47 Likes Received: 2,785 in 2,247 posts Likes Given: 7,684 Joined: Jul 2019 Reputation: 97 13-Jul-2022, 05:46 PM (This post was last modified: 13-Jul-2022, 05:48 PM by iFly4rotors.) Yes. It is challenging to do the most we can and keep the All Up Weigh below 250 grams. The battery is the heaviest single component. It just is. To get anywhere decent, you need to allow at least 75 grams, but 100 grams is better as it will allow for a little bigger LiPo or even a 2S Li-Ion pack. So that limits the entire rest of the quad to 149 grams MAX including all action cams, mounting hardware, payloads, literally anything and everything. If you count the prop and prop bolts with the motor, then the drive train is often the in competition with the frame as the next heaviest subsystem. Here where it gets interesting. Stronger frames are heavier. Bigger Motors are heavier. As you add power and strength, you also add weight...quickly. I did build a 5 inch with 20 gram (each) motors, but having a dry weight of 198 grams, it was only sub-250 grams with a very small battery. Any decent battery pushed the AUW right on over the 250 gram mark. So, there is the harsh reality: Motors that weigh 20 grams each are really too heavy. Now, selecting a motor to fit your desired flight characteristics can sometimes be challenging. Personally, I try to keep the motor weight to about 15 grams each. This is why the sub-250 gram performance quads tend to be the smaller ones... 3.5 inch and smaller. The stronger frames are heavier while the lighter frames tend to be weaker. Ah, but this is the place where you adjust a bit if you need to loose some weight. The electronics package tends to be about the same for each type of video; analog vs digital. There really isn't a lot of room to negotiate much weight here. Each type has things with pretty much consistent weights...so we are just stuck with that. • Posts: 155 Threads: 15 Likes Received: 36 in 25 posts Likes Given: 2 Joined: Jan 2022 Reputation: 0 Building a sub-250g definitely seems like sitting on a teeter totter. Everything is a compromise to get you to the magic number. What is the advantage of building a 5" sub 250g versus a smaller 3.5, 3 or even a 2.5" quad? Looking at the numbers it would seem like going to a 5" you would need to give up a significant amount of performance over a well built 3/3.5"? More stability at speeds? • Posts: 5,903 Threads: 47 Likes Received: 2,785 in 2,247 posts Likes Given: 7,684 Joined: Jul 2019 Reputation: 97 (14-Jul-2022, 02:09 PM)Janz99 Wrote: Building a sub-250g definitely seems like sitting on a teeter totter. Everything is a compromise to get you to the magic number. What is the advantage of building a 5" sub 250g versus a smaller 3.5, 3 or even a 2.5" quad? Looking at the numbers it would seem like going to a 5" you would need to give up a significant amount of performance over a well built 3/3.5"? More stability at speeds? Hi Janz, The advantage of bigger props is that they push a lot more thrust, period. It is not about acceleration or performance, but rather being able to push enough thrust to fly at lower throttle {less RPM} for endurance AKA long range. That is precisely why the true long range guys start with 7 inch and go up from there...9 inch, 10 inch, and up. I have actually built two 5 inch sub-250 gram quads. The first had 20 gram (each) motors which meant small battery, but that thing was butter smooth and didn't take much throttle to fly. She was a real dream. Yep, lost that one. My other 5 inch was running smaller motors and yet, butter smooth and didn't take a lot of throttle to fly. Yep, that was the Unsanctioned-1 which is now in a tree. I am going to try to get this one back since it was built on a one-of-a-kind prototype frame. Any sub-250 gram build that is 4 inch and larger is NOT going to be a Hi-performance quad; it just isn't. The motors required to push a quad this size to a performance point that the ACRO pilot likes are just too large and too heavy. That is why these will end up just being cruisers and perhaps long range. My next build, GT_LT6-X1, will be built on a 6 inch frame and assembled to be a sub-250 gram quad. The frame is a special cut by gt40 and only weighs 32 grams. I think that I can get a nice 6 inch sub-250 gram cruiser. You know, 250 grams is pretty light when compared to the thrust of 6 inch props; probably only need about 10-15 percent throttle to fly it. I predict that it will be the 3 inch and, maybe, the 3.5 inch that will end up being the sub-250 gram Hi-Performance quads. For the smaller prop size, the smaller motors will spin up fast enough to get that acceleration that is so desired by the ACRO pilot. New motors seem to be coming out every day for the sub-250 gram builds. I have seen one of the fastest ACRO pilots run only on 3S batteries. Interesting... With the right motors and props, a 3S battery will provide plenty of acceleration power. It all depends on the components and how the quad is built. Personally, I like a 2.5 inch to play around with and try ACRO stunts. This size is my favorite quad to just have fun especially in smaller locations. • Posts: 4,731 Threads: 392 Likes Received: 3,231 in 1,827 posts Likes Given: 3,214 Joined: Apr 2019 Reputation: 101 14-Jul-2022, 04:53 PM (This post was last modified: 14-Jul-2022, 04:54 PM by the.ronin.) I will be the first to admit that even on its best day my best build on my best frame with the best tune will not hold a candle to an equally well built, well tuned 5" Apex. And 100% iFly, 3.5 in my opinion is *currently* the sub250 sweet spot. And to me, I define sweet spot as excellent speed and throttle authority, bando-worthy durability, 3-4 min of hard acro flight time, capacity for a 4K cam. Emphasis on "currently" since power trains and HD cams are getting smaller and better over time. So it may be at some point sub250 5" will be the norm as tech progresses. • Posts: 21,302 Threads: 589 Likes Received: 8,987 in 6,652 posts Likes Given: 1,426 Joined: Jun 2018 Reputation: 789 Yeah, until the regulators get wise to the fact that everyone is managing to bypass most of the regs with sub-250g quads, so they will just raise the bar even higher and change the limit to 200g instead Just build what you want without worrying about the weight or having to make compromises, then fly it like you stole it well enough away from civilisation where there is no-one to bother and no-one to care whether it's over or under 250g Posts: 2,509 Threads: 76 Likes Received: 1,389 in 1,040 posts Likes Given: 804 Joined: Apr 2022 Reputation: 41 If it's small (whoop, 2-3"), it's possible to get away with it in the city, but if it's noisy and runs on 4-6S, do as Snow mentioned and fly it in the countryside as far from people as possible. People are the bane of our hobby, avoid them at all costs. I used to worry about flying my whoop in the city, but literally no one cares. People just ignore me (or maybe I look crazy and they are too scared to approach me). Either way I can live with people not going near me. I found a few places to fly, a mixture of parks and bandos. You find other people in parks, but bandos only FPV pilots, Urbexers, Grafitti Artists (and very rarely) Junkies. You will probably be able to find similar places to fly near you. Try Not, Do or Do Not - Yoda Posts: 1,489 Threads: 92 Likes Received: 574 in 468 posts Likes Given: 0 Joined: Nov 2020 Reputation: 27 Even if only 2mm clearance, I would definetly prefer larger 3.5" over 3". Do it. Find a way • |