XLR-1

This project includes development of the next generation of frames that began as a speed project, but will also give rise to production frames for racing, freestyle, and endurance.

NOTE: Most, if not all, updates are in regards to the speed project. The production project can be found here.

Contents:

  1. 200mph, 30A ESCs and Nano Tech Lipo??? LMAO!!!!
  2. Progress Updates
  3. Scrapped Designs
  4. Frame Evolution… or Revolution?
  5. Lightweight Frame Test
  6. Modular Design
  7. Electronics

0005r6

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200mph, 30A ESCs and Nano Tech Lipo??? LMAO!!!!

Yes, not spectacular and not good for marketing the latest hyper-amped ESCs and 100C+ lipos. There still is a need for those, but not when it comes to top speed builds.

The gift that keeps on giving

That gift actually starts by taking away something: drag. Once this is done, we are given the gift of speed, and speed starts a seamless circle that keeps on giving:

  1. Less drag = more speed (less force needed to push through air)
  2. More speed = props less loaded (blog on prop unloading is here)
  3. Less loaded prop = less torque needed to spin props
  4. Less torque = more RPM
  5. More RPM = more speed
  6. Steps 2-5 repeat seamlessly up to the “terminal drag” point
1524929257938_image
Graph of data from a speed run (from a different frame). Power requirements drop with speed

Terminal drag

This is where either:

  • The residual thrust equals the drag force. Remember the faster we go, the less thrust we have which, as long as the drag is low, isn’t a big deal.
  • The propeller tips start going transonic (about Mach 0.75-0.80). This is where torque requirements skyrocket and things go bad from there.

The meaning?

For brushless motors, volts = RPM and amps = torque. Now we see (and tested) why 80A ESCs and 10s batteries will do absolutely nothing but create heat and flames (didn’t I say that about 6s at one point? Hmmmm…..) The faster we go, the less amps we need to keep moving. However, we need the volts (RPM) to get there – up to a certain point: the prop tip transonic speed limit. This is where amp draw will jump and things go into a downward spiral – sometimes literally.

Just a quick note: the above is also the reason there is still a need for higher amp ESCs and batteries. Race quads and freestyle quads do a lot of direction change and throttle hammering. This means the props are undergoing a lot of stress and loaded a relatively high amount of time. Think of a bicycle with a fixed gear ratio. When you are travelling at high speed, pedaling effort (like amps) is easy. Now if you were to start doing some frequent stop, accelerate, repeat over and over… pedaling effort has increased tremendously.

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Progress Updates

April 10, 2018: As usual, I will have to clean up this page and organize it a bit better.

The Record Attempt(s)

More things went wrong than I am willing to admit, but the biggest lingering issue was the video reception. It was a huge “duh” moment. The whole event was pretty chaotic, but this is a general overview.

Witnesses involved in the runs (we had a lot more than required) were people from various engineering backgrounds including several from the aerospace industry.

April 4th: Practice day. I brought 5 frames with me, 2 5s frames and 3 6s but I only got to practice with 5s since video range was bad and I was afraid that 6s would quickly leave video range. 5s practice went OK, but the frame was very unstable at high speed. Max for practice with 5s was 171.5mph/276kph.

April 5th: Speed runs. Still had video issues which only allowed for a good run in one direction (100m average in one direction). To add more to the mess, the GPS lost connection on the last battery (due to a broken wire) and then had a minor crash. Max speed was 181.44mph/292kph. However, since the 5s frame was so unstable, it couldn’t keep up a consistent speed. The best I had was an opposite 100m average of only 163.61mph/263.3kph. It was a good time for a break and to do repairs. While doing repairs and since we had the means to record and measure it, Josh Cook gave a try at the ascent record – this way, if things went really bad and I never got the chance to give the ascent a try, at least one record would have been broken. Josh ended up with a 100m ascent in 2.80 seconds which was roughly a full second quicker than the previous record.

Being very careful not to go out of video range, I got in a quick practice run on my 6s “mutt” frame at the end of the day. If any frame was going to crash, this was going to be it since it was pieced together with some beat up motors and ESC’s. First pass hit 167mph and was very smooth. Second pass ended in a crash. As I was going throttle up, an ESC failed (not exactly sure why, nothing was burned up). This single run gave me confidence in the 6s, but the video issues lingered.

April 6th: Speed runs continued and ascent attempt. This was scheduled as the backup date since we were leaving the next morning. Starting with 5s, video issues continued and seemed to be even worse. It got to the point where I had to stop things and figure it out. Thinking my goggles were bad, I sent an SOS to Jayson Smith (MetropolisFPV) and he let me use his goggles. Once I had those, I did some on ground comparisons of video reception of all the vtx’s I had and between my goggles and Jayson’s. Truthfully, reception was only marginally better with Jayson’s – not enough for me to feel comfortable.

As time was running out, Jayson asked what the tail cone was made out of. I told him it was 3D printed and that all I know is that the material is carbon reinforced. Jayson pointed out what should have been obvious to me about 4 months ago. The carbon is messing with the rf signal. Duh. So I then realized the antennas had to be moved to the outside.

Before I did that, I made an attempt at the ascent record. Since I had Wraith32 ESCs on this quad, I thought I would be able to see the quad easily, especially since it was very late and nearly completely dark out… Well, that didn’t work out that well. The thing took off, I didn’t get the stop signal, so I was on the throttle a bit too long and lost it. Good thing is that the video of the ball and string (100m string attached to a whiffle ball) was recorded. Time started at quad launch and ended when the ball moved. The string was taped on the drone so the string wouldn’t follow along and get wrapped in the motor (this happened to Josh). The whiffle ball was attached securely to the ground so the whiffle ball would win the tug-o-war. After review, the time was 1.70 seconds. I then got to work on putting the antenna outside the tail cone for a last attempt.

The ascent video: As expected, the take off does look SLOW. This is due to the high pitch 5260 props – calculations showed that they would take off a little “slower” than a 5″ pitch prop, but the 6″ pitch would over take a 5″ prop in a 100m race.

April 7th: Last chance. Everything went great. Video test of the new antenna placement looked good so I decided to use my own FPV goggles while my son wore Jason’s as a backup. It flew like a dream, did 4 passes and then decided to bring it in early since I easily could have done 2 more passes but I wonated to play it safe. I knew it went fast, but when I saw the 325K max speed on the OSD, I could hardly believe it. I then took a look at the log and double checked to make sure all looked good; the quad was slightly climbing for both of the fastest opposite passes and the headings were only 4.16° off from 180°.

At the end of the 3 days, 4 records were set – ascent twice, speed, and payload for 250mm quad was set by Forrest Frantz (I will have to get the details and video).

Opposite direction average over 100m: 195.99mph/315.42kph

  • Direction 1 average over 100m: 196.70mph/316.55kph
  • Direction 2 average over 100m: 195.28mph/314.28kph
  • Max Recorded Speed: 202.11mph/325.26kph
  • Blackbox data is here
  • Spreadsheet with decoded GPS data is analysis is here
  • How the data is analyzed is here

Special thanks to Forrest Frantz for making this happen, Jayson Smith for saving this speed attempt, and to Jon Blackburn for printing/designing the nose and tail cones.

2018-04-08 03.56.24.png

GPS Path

April 7, 2018: Another short update. One of the 5s frames reached an altitude of 100m/328ft in 1.70 seconds.

April 6, 2018: Still working on things, so far hit a peak speed of 292kph/181.5mph on 5s (not an average, just a peak speed)

292kph

March 26, 2018: Thanks to Josh Cook of GetFPV for doing this article on the speed record attempt, he made me sound like a halfway decent human being. GetFPV recently started writing articles at getfpv.com/learn which are very informative and professionally done.

March 25, 2018: Added a section with a few pictures of 2 different design concepts that were scrapped.

I also wanted to thank Jon Blackburn and Forrest Frantz – they perfected the nose and tail cone design and Jon printed them.

Cones 1

Cones 2

Cones 3

March 1, 2018: I must remember: hit the record button. I only have video of 4s runs (boring). This is why I will be making a checklist… I flew a few times over the month with no significant flights (due to weather) except for yesterday. It was relatively warm at the time (50°F) so I decided to tune in some APC 5050 props on 5s and do a few short speed runs (only 1.5-2 seconds WOT). The first 5s flight began and ended with some PID adjustments but I got a couple speed passes in between. 146mph/235kph is nothing remarkable, but I’ll take it considering that:

  • The PIDs still needed to be lowered (oscillations at WOT)
  • The time at WOT was only 2 seconds
  • Relatively cool temp, so the batteries were cool
  • Only 2 speed passes which didn’t give the battery a chance to heat up – it was barely warm
  • A “practice” nose cone with higher drag was being used
  • In the past, the 4th or 5th speed passes are the fastest and are typically about 15-20mph/24-32kph faster (since the battery warms up and internal resistance drops)

I wanted to continue and try some 5060 props, but then my motors became afflicted with the “mystery” rocks (more like the size of sand). I ended up getting some dirt/sand in the motors on one of the landings. To put it as short as possible: I blew out the sand, thought all was good, but after about 20 seconds, motor 1 failed. At home, I still felt the sand in the motors and could not blow it out. When taking apart the motors, I found what looked to be like very small rocks sticking to the magnets – sticking since they were magnetic (mildly magnetic). In my metal working experience, I have never seen any metal that has looked like this so they are not any part of the motor. Being magnetic, they wreaked havoc on the motors and scratched up the magnets and one motor had a dislodged magnet while another had 2 dislodged magnets. The impact to the ground was relatively soft, so I don’t think the impact dislodged them. It’s still inconclusive as to what actually happened, but here is a picture of one of the magnetic rocks:

Magnetic rock
Motors do not appreciate tiny magnetic rocks, especially while spinning at 30-40k RPM

January 29, 2018: After a couple of “mishaps”, a few other issues (gyro not wanting to calibrate), and wanting an external sd card for blackbox logging, I decided to go with the Joshua Bardwell Edition F4 Flight Controller which I just ordered from Rotor Riot – they DEFINITELY get 17 out of 10 stars for their customer service! As far as I have heard, the JBF4 reviews are great and it has everything I need. A close runner up was the CL Racing (which uses the same hex as the Bardwell F4) but there are too many “death roll” reports.

XLR-T33

Although the weather is looking rough, I did find a large field not too far away that I can do some test runs – this should help a bit with progress.

January 16, 2018: A quick test flight was done last week on 4s. A poor decision in construction made one of the ESC wires break loose and ended up crashing. Temp was 30°F and I didn’t go full throttle long enough to get to top speed. I didn’t want to let it go too far out since the snow was deep and it would make crash recovery tough.

Conformal coating was used and no major damage. The frame will be reworked to the latest revision of the frame, which is the final revision.

I have changed my mind about having the frames adjustable in size. Instead, I will build separate frame sizes. I would rather have each frame ready to go instead of reconfiguring them. Although the idea is simple, I would rather not deal with that right now… So the fleet will be like this:

  • 2 5s “Revision B” frames (for flight tests)
  • 1 6s “Revision B” frame (for flight tests)
  • 3 5s “Revision C” frames
  • 3 6s “Revision C” frames

Yes, 5s is plenty, but 6s will also be used just for an added cusion. No matter how you slice it, the math shows that anything more than 6s will only turn into heat and excessive amp draw.

December 30, 2017: The date has been set and the world record fleet (Guinness World Record attempt for speed) is slowly coming together. Although they are in various stages of completion (only one is flyable at the moment), there is plenty of time to refine the frames. Right now there are 5 frames, but this number might increase slightly. When I say frames, I mean the base structure since being a modular design, they will all share 3 or 4 sets of electronic modules. Goals for the world record day:

  • Have at least 5 base frames
  • Frames can be configured with different arm layouts
  • Frame bodies can be configured for different battery sizes.
  • Although only the top overall speed will go in the books, top speeds will be attempted for different battery cell sizes.
  • Other records (not using my frame) that will be attempted on the same set of days are quadcopter endurance and fastest quadcopter ascent to 100m.

December 29, 2017: A small update – due to independent motor tests and the recent Choosing The Right Motor blog post, I have decided to stick with the Cobra CP2207 2450kv motors.

VX1 05
Cobra motors shown on the VX1 project

December 8, 2017: The Future is Clearer: Not so clear on the site – I will have to expand on this over the next few days (slightly). In short, the speed fleet is being built. They are slightly different from each other and completely interchangeable with one another using a modular design. If a new idea does pop up, it can easily and quickly be integrated. Overall I am extremely happy with just about all aspects of the design, but I am extremely unhappy with the weather. Hmmmm, maybe a heated transmitter powered by a lipo should be next on the project list…

November 28, 2017: The 5″ production prototype (race/freestyle) is a bit heavier than anticipated at 44g, but it should be able to be trimmed to 36-38g. More info is in the video description about the build, but it was done in an extreme rush. Some specs so far:

  • 215mm Motor to motor distance
  • Final design will be around 36-38g
  • The only fasteners will be for the motors and the stack – no fasteners, epoxy, glue, etc. is needed to hold the frame together (although the one in the video used 2)

November 14, 2017: The next prototype frame is well under way. I do not expect much to happen in terms of flying, but if I do get a chance, it won’t be a surprise if it breaks 165.80 mph mark set by the VXR-190. Although I expect this prototype to do very well, there will be more frames being built to hone in on the features that the final build will have.

November 5, 2017: I finally had a flight with the first frame design which is already obsolete, but it still had some other aspects that had to be tested and was successful. I’m not bothering with video since it was beyond boring and I was only flying with a 4s. So now it is on to the next frame. If it goes the way I hope, it is going to be very cool in terms of having a modular design.

By the way, with the updated Blheli 32.1 update, the Wraith32 ESCs sound great.

October 5, 2017: I never quite finished the first prototype (this is common for me), it never quite felt right. The 2nd prototype frame is almost done (no electronics yet). The arm design is radically different from previous designs. Once this design has been proven, it will be on to the more refined version. However, both of these frames (if they work) will not have the goal of all out speed. As stated earlier, the current goal is to get some testing on different configurations – many different configurations that can be accommodated and switched out (relatively easily) on the test frame. Whether it hits 200 mph or 36.2 mph, I will be sure to post videos. Hopefully this will be next week.

September 2, 2017: After looking at this build, I really don’t expect to be finished until spring. Although this sounds like a long time frame, a lot of progress will be made along the way. Why? This design is more of an adaptive design (at least that is what I am aiming for). There will be a core frame which can be modified relatively quickly with different sub assemblies. With that being said, there might be many configurations that will be tried out before the best combination is found.

August 29, 2017: The official start of the next speed project. I don’t have any specific goals or speeds to hit since there are a lot of unknowns. It really kills me, but for good reasons, I will be giving even less details about this build for the time being.

I do plan on posting what I can (numbers, logs, video, etc.) as things progress. I hope to have a frame or two built by this weekend, but as history has shown, it will probably be 2 or 3 weeks until something good happens.

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Scrapped Designs

Design 1: 6s design that used 2 3s batteries. It sounds simple, but the logistics of the accessory components started to give me headaches. It could definitely be done, but I had other ideas.

X1 04

X1 03

Design 2: I’ll admit, I didn’t have very high hopes but it was worth a shot. The arms were too flimsy (not to mention very wide). I did get to fly it once but it needed a little reinforcement. Needless to say, it was scrapped for the latest design.

D13

D12

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Frame Evolution… or Revolution?

Although flying time has been lacking, there has been plenty of time to develop, evolve, and build different arm configurations using different construction methods and materials. The latest configuration design is extremely promising as far as versatility, strength, low cross section, balance, and has a high possibility for production kits. The design scales down extremely well while retaining its strength.

Another big development is the motor mounting. It might sound odd, but it is a big breakthrough.

So far, these are the frames that have been constructed using this method and their weights. Just in case, a lot of this should still be taken with a grain of salt and all weights given are bare bones:

  • 5″ Speed Drone Frame: 26g (excludes nose and tail cones)
  • 5″ Freestyle/Race Frame: 20.25g. This frame has me very, very excited.
    • I would like to refine this version into a frame that can have replaceable arms. I am guessing it would add another 6-8g.
    • There is a slightly promising method that might only add 2-4g to have the arms replaceable.
  • 5″ Light Weight Frame: 9.96g. Although this frame can support 95 lbs (see picture below) this might need just a little more to strengthen it (torsionally), but It shouldn’t be more than 11g.
  • 5″ Featherweight Frame: 5g or less. This is still in progress and is at 4.45g. I am still pinching myself over this one… but something tells me it wouldn’t hold up to hard flying or maybe just hovering… This one is on the shelf for the moment.

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Lightweight Frame Test

A dirty test setup: the frame is placed over a pot. The arms are supported on the rim near the motors. In the middle of the frame is a 1.5 inch square block to set weights on. I ran out of weights, so I threw the bar on too.

DSCF8319
I ran out of weights, so I added the bar. It might look like some weight is resting on the pot handle, but all 95 lbs (roughly) is resting on the 5″ 9.96g frame which is hidden under the weights.

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Modular Design

Just a quick mention – I can see this frame being developed into a kit that can be configured several different ways by adding components to the bare bones frame.

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Electronics

About the only thing I have confirmed is using a Betaflight F4 flight controller.

Betaflight F4 front

Betaflight F4 back

For the initial ESC choice, I will be going with the Airbot Wraith32 Metal. Since Airbot was nice enough to send these to me, this might be a good chance to redo my Wraith32 review. Apparently, the firmware was at fault on my initial review.

The reason I want to use these ESCs is so I can record and analyze the data from the ESC telemetry.

I also had a couple other frames that were outfitted with the Spedix ES 30 HV ESCs. They were mainly chosen for their reliability – 32 bit is still a little new, so I wanted to have a stable backup.

However, when it came down to the wire, the Spedix were on the spot and performed flawlessly.

spedix-30a

And of course, I will be using the ublox M8N for the GPS reciever.

t150-04

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11 thoughts on “XLR-1

  1. Torashuu says:

    Very nice site, was wondering when someone was actually going to design around frame aerodynamics in a more rigorous way. I’ll be keeping an eye out for any frames you might put out.

    Liked by 1 person

  2. Torashuu says:

    Dont worry about site organization, so long as the principal ideas are there (excempting those involved in any patents of course). Just the clarification of the possible gains, the back of the envelope calculation on maximum attainable speed already sets some rough limits and goals that give you something to work with, contrary to regular frame design which seems mostly based on gut feeling and user feedback. Not to mention this actually gets me thinking about custom frame design for myself. 🙂

    Liked by 1 person

    1. downanddirtydrones says:

      Glad to hear – back of the envelope is about all you can do with these things. It was a good sign that I was doing something right when a small group of guys took me in back in July – very smart guys. A few affiliated with R & D in various aerospace and air defense industries, dozens of patents among them, all retired early – hopefully by their choice 😉 We have a rather lengthy confidentiality agreement among us and we bounce ideas, verify, etc. Since being in the group, I haven’t had to change the Speed Calculation spreadsheet at all. That’s not to say it couldn’t be improved! Although the website is in the doldrums (as far as info goes), things are busy behind the scenes – very tough to stay focused… I almost forgot to mention: frame design is addicting. I started by modifying existing kits. Some are so cheap, you can buy a few kits and use them for materials.

      Like

  3. Reinhard Plietsch says:

    U – R – CRAAAAAZY! This pulverizes all current speed records like they are ‘toddlers toying around’. This is serious biz now – big hands of cheers and hearty congratulations!

    Liked by 1 person

  4. Darrel ( Sennheiser357) says:

    I knew after seeing the vx1 record your design was the best engineered attempt at the top speed run🍻.
    Im curious if you considered bullit typing the front and backs of your motors and tapering were the air velocity is highest?
    Also the tail section being drag coefficient is the greastest gain at the moment due to prop design and battery energy density, weight to power output.
    I love how you equalled the drl 8s build with better engineering and knew your
    Design would reign supreme.
    Even bragged for you to Baurdwell and Floss on comments in YT ,,,lol.
    Ive been looking into turbo prop designs and alot of the ww2 engineering when most of the R&D for aircraft solidified to seek answers myself.
    The sound barrier seemed to be the limit for xf-84 h turboprop plane with A 6-1 hp to lb ratio i dont know it cD .
    Any thoughts on counter rotating props smaller motor setups smaller props ? Less tip velocity?
    Future of prop designs ?
    Sorry,,,lol
    Congratulations anyway and thanks for your contributions🍻

    Liked by 1 person

  5. Adigo says:

    I can fully confirm that higher speed require less power-thrust in real-world flight. And in quadcoper-domain C-rating and less Amperes. Just think about the specific thrust of pulse-jets and RAM-jets> they have the lowest specific thrust among airplanes, yet achieve efficiency at highest speed. But the CONDITION is AERODYNAMIC.Good aerodynamic! Your conclusions are perfect (proportionally scaled down for quads)> And the results shown that! .

    Liked by 1 person

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