Strider mini quad build log

[joshuabardwell]

This post is a placeholder for the Strider mini quad build I'm going to do. The Strider frame is shipping in early April, so I'll update when the parts actually arrive.

For the time being, here is my parts list.

• Strider mini quad frame from RedRotor
• ZTW Spider 12 amp opto ESC
• Sunnysky X2204 2300 kv motors
• HQProp 6x3 props
• Acro Naze32 FC
• FrSky D4r-II receiver
• Turnigy Nanotech 3S 1500 mAh 35-70C LiPo

I will also be installing the FPV gear from my ElectroHub, which is:

• ImmersionRc 600 mW vTX
• 25mm Sony 600 TVL Super-HAD 5v-capable camera (this is a great camera, that is finally available in a 5v version!)
• BlueBeam CP antenna

I plan to skip the telemetry functionality of the D4r-II and use the built-in OSD on the frame. I don't really think an OSD is necessary on a mini quad, but the Strider is a really nice frame, and the non-OSD version was only a little cheaper, so I figured what the heck.

EDIT: This is the Strider RROSD, not the Strider Flex.

 

[ExperimentalRC]

I cant wait for this.

 

[joshuabardwell]

PS: I did the math, and by the time all is said and done, I'll be in about $450 for the quad, and about $1100 all told including the FPV gear and transmitter. Yikes. Nobody ever said this was a cheap hobby. Still, it kind of sneaks up on you. I bought my first plane (a Bixler) on April 15, 2014, so I'm just about a year into the hobby. $100 here, $200 there, and suddenly you're flying $1000 into a tree. How did that happen? I've spent nearly all my disposable income on this hobby for the last year. I guess it shows.

 

[joshuabardwell]

Well, this is only loosely related to the Strider build, but since I've nothing else to post for the time being... I put my ElectroHub up on Craigslist for sale, and got offered an RC car in trade. The guy was actually the perfect buyer for the ElectroHub. He had been flying a micro RTF quad indoors and was ready to step up to something bigger, but thought a 250 mini might be a bit beyond him. I got his transmitter and receiver set up, configured the rates and everything for a beginner, and the deal was done.

It took me not very long at all to kit the car out with the FPV gear that had been on my copter. Great fun!!!

 

[joshuabardwell]

As of today, all parts have arrived except the frame, which is supposed to ship "at the beginning of April". Waiting the next couple of weeks is going to drive me crazy, but at least I can start getting the electronics sorted out.

 

[joshuabardwell]

Today, I received the D4R-II receiver. There is a known issue where the frame sizing on the CPPM output only allows up to six channels to be used, when the receiver can output up to eight. So I flashed a firmware that fixed the issue.

Instead of using FrSky's USB adapter, I used an FTDI cable that I already owned. This required inverting the RS-232 signals from the cable, according to instructions here (LINK).

Then I downloaded the updated firmware from here (LINK) and flashed it according to the instructions in the readme PDF in the zip file. The only problem I ran into was that the FrSky updater program kept being unable to contact the receiver. The issue turned out to be that I still had the FTDI configuration program open, and it was holding onto the COM port. Everything went smoothly after that.

The next step will be connecting the D4R-II up to the Naze32, except that I have just realized I don't have a male-to-male servo lead (my Naze board didn't come with a header for some reason), and I will have to fabricate one.

 

[joshuabardwell]

I did some work getting the receiver and the Naze32 configured tonight. First I set the channel endpoints. I went to the Servos screen in the Taranis...



And adjusted the endpoint while holding the relevant stick all the way up or down. While I did this, I watched the channel value in the Cleanflight configurator...



And tweaked the values until the endpoints were 1000/2000. I used subtrim to make the midpoints 1500. The right values for the Taranis were about 98% in at the endpoints, and about -0.5% on the center. This highlights the importance of checking the actual readout in whatever app your FC uses, instead of following generic advice to "set the endpoints to +125/-125". That advice certainly will work, since it will cause your channels to exceed the required min and max threshold to get the FC to respond, but you'd be wasting a LOT of your stick travel with this particular transmitter.



Although I plan to use the Strider's built in OSD as the primary means of monitoring battery state, I couldn't resist wiring up FrSky telemetry. The Taranis uses it, so why not? The D4R-II came with several leads for just such a purpose. In an instructional video on the topic, someone advised cutting off the two un-used wires in the above-pictured four-wire connector. I think it's much neater to use a utility knife or other thin blade to lift up the retaining tabs and pull the pins out entirely.

A side benefit of hooking up telemetry is that the Naze reports a few other interesting tidbits, such as accelerometer data. I don't know of much use for this, but it's gratifying to know it's there.

Regarding telemetry, it's important to know that the Naze can't do telemetry and USB at the same time (EDIT: By default, at least). If you are plugged in via USB, telemetry seems to stop updating, although the receiver continues reporting the last-received value, so you don't get a "Telemetry Lost" alarm from the Taranis. Also, the Naze only reports telemetry when it is armed, which is a common source of confusion.



The result so far is pictured above. The battery monitor allows the Naze to report battery voltage through FrSky telemetry. An important tip is that the voltage is NOT reported as one of the analog inputs (A1 through A4) but is reported as if the Naze was a FrSky FAS current sensor. As a result, you must set "Voltage Source" in your Taranis to be FAS (this is on the Telemetry screen). This will cause the display at the top of the main screen to be the voltage reported by the Naze, and not the A1 voltage reported by the D4R-II (which will always be the 5v that it's getting from the BEC, not the actual pack voltage).

So far, I am really thrilled with how easy the Naze32 is to configure, and how well-integrated it is with the FrSky system.

 

[joshuabardwell]

Here's the final (?) board and receiver, nicely dressed and ready to install.



I've used a wrap of electrical tape to dress the VBAT and Telemetry leads, both to keep things neat ,and to provide a bit of extra reinforcement against them coming loose from the pins. I've done the same thing on the receiver end to retain the wires going into the telemetry connector, as they are quite thin. It's probably unnecessary, but it keeps things tidy and I like it.



For the single-pin and dual-pin leads, I am simply crimping on a pin and then putting a length of 1/16" heat shrink on the pin. I don't have any 1x1 headers or I'd use them.

EDIT: I've also just realized I've posted a photo of a whole bunch of my solder joints on the Internet for everyone to criticize, and have I've become terribly self-conscious of every one that isn't absolutely perfect as a result.



You can purchase the crimp pins quite cheaply here (LINK) and they're very handy to have around when making custom headers. You can use a crimp tool to install them, but it's very easy to do with a needle nose pliers if you're willing to invest a little more time. Given that the crimping tool costs around $35 it's a no-brainer to me to do it by hand. If you work with RC flight, I highly recommend keeping some of these crimp pins around, as you never know when you need to shorten a header or make up a custom header from some spare jumper wire or something like that. If you like, you can also order custom-size housings here (LINK).

 

[joshuabardwell]

The frame is supposed to have shipped today. VERY EXCITED!

 

[joshuabardwell]

I finally received the frame today, and construction can begin in earnest.



Frame came in a priority mail box with all parts neatly sealed in plastic. Very professional packaging.

 

[joshuabardwell]

The first thing I would recommend somebody do when building this frame is sort out all the screws by size. There are several different sizes used, and some of them are easy to confuse for each other. The manual has a parts list that details the sizes and their uses. My frame came with a few extra nuts, screws, and standoffs. The manual says they came as spares. Okay, on to the construction.

Bottom plate, PDB, and standoffs installed.





Legs installed.



The next photo shows the front legs, one in the rear-most position and one in the front-most position. The front-most position is used for flight, and the leg can collapse to the rear-most position in a collision.



By pulling outwards firmly first, the leg can be folded into the transport position. Due to the force required to pull the leg outwards, it's hard to imagine a situation where the leg would fold up in flight.



When I first heard about the frame, I imagined that the collapsing mechanism would be such that the leg could fully fold up in a crash. Obviously, this would have the potential for spinning props to damage the quad, but I wondered whether the creators of the frame had some deviously clever solution to that problem. The situation seems to be that the legs can collapse slightly backwards to absorb the impact, but that they don't fold up altogether unless you do it manually. This is, all things considered, probably the right way to do it.

Neither the frame, nor the motors that I bought (Sunnysky x2204 2300 kv from Multirotor Superstore) came with mounting bolts, so off to the hardware store with me tomorrow. I tried to do a temporary installation using the 6mm screws intended for the top plate of the frame, but for some reason, two of the Sunnysky motors won't take M3 screws, while the other two take them perfectly. I'm at a total loss. The threads look fine. It's almost as if they are a different size of screw.

 

[joshuabardwell]

After a trip to the hardware store to get some screws for the motors, I got the motors mounted.



There was no further problem with the screw holes. There was a bit of resistance on two of the motors, but with steel screws I wasn't hesitant to push through it and all was well.



Figuring out how to mount the receiver and vTX was tricky. I actually got the top plate on and figured out that my receiver location wouldn't allow the vTX to fit where it's intended, so I had to go back to the drawing board. I ended up using foam tape to stick the receiver to the top of the FC and I had to move the motor output wires to a different side of the board, to make more room for the vTX to slide in. I've also got a lead installed for the Bluetooth adapter, which I plane to use to tun the PIDs. Cleanflight does have the ability to do in-flight PID adjustment by flipping switches, but I prefer the more granular approach of choosing exact numbers. Maybe I'll change my mind once I try it.

This is the arrangement I plan to use. FC, receiver, then vTX. The vTX will be taped to the top plate.



And here's the frame with battery installed.



It looks like the frame is very tail-heavy, but the battery is the vast majority of the weight, and the CG is actually about 25% back from the front edge of the FC in this photo.

I accidentally ordered RP-SMA hardware instead of SMA for my vTX, so I won't be installing it for now, and that also means I won't be playing with the OSD or anything like that. In the mean time, I will do some flight tuning line of sight.

 

[joshuabardwell]

Let's talk about wire management. Originally, I wanted to do wire wrap on my motor wires, to give them that lovely professional look. I got some para cord wrap and tried using it, and immediately ran into some problems. First of all, I couldn't figure out how to get it onto the wires if I was going to solder them vs. using bullet connectors. In order to do that, it seems like I would need to squeeze the wire wrap and the heat shrink for the ends all the way over to one side, then solder, then heat shrink the individual wires without shrinking the heat-shrink for the ends of the wire wrap, then finally stretch the wire wrap out and shrink its heat-shrink at the ends. I don't see how that all is really feasible. So I gave up on the wire wrap and resorted to my old stand-by of twisting the wires to take up slack.



But I hate it, and it looks terrible, and this is supposed to be my no-compromises luxury build (as opposed to my kludged-together Electrohub), so I un-twisted it and tried something else.



At least this looks neat, if not ultra-luxe. One challenge is that, in order to fold the legs, you need a bit of extra slack in the wires, to allow the arms to pull out. This makes a bend in the wires that has some danger of coming up into the prop, if you're not careful. I'm not sure how best to manage this. I could certainly re-solder the wires a bit shorter, but I'm not sure I want to go through all that work.

If anybody has any input on how to do professional looking wire-wrap, please let me know. For the time being, the only thing I can think of is to use bullet connectors that would allow me to easily install the wire wrap without having to apply heat to the motor wires with the wrap installed.

Here's a quick shot of the camera install. My camera has a bracket, so I'm not using the board camera plate that comes with the frame. It's installed to a pre-existing frame slot with an M3 screw and nylock nut. Then I use some layers of foam tape to hold the camera at the desired angle, which for the time being is level with the horizon, although I will probably be tilting it up eventually.



Finally, I need a bit of advice as to how to mount the antennas. I have heard of people using heat shrink and coffee stirrers, but I'm not sure how people are actually connecting these things to the frame. I could come up with something, but if there is a neat and elegant solution that others have figured out, I'd love to hear it.

 

[SHIFFTY]

antennas

Let's talk about wire management. Originally, I wanted to do wire wrap on my motor wires, to give them that lovely professional look. I got some para cord wrap and tried using it, and immediately ran into some problems. First of all, I couldn't figure out how to get it onto the wires if I was going to solder them vs. using bullet connectors. In order to do that, it seems like I would need to squeeze the wire wrap and the heat shrink for the ends all the way over to one side, then solder, then heat shrink the individual wires without shrinking the heat-shrink for the ends of the wire wrap, then finally stretch the wire wrap out and shrink its heat-shrink at the ends. I don't see how that all is really feasible. So I gave up on the wire wrap and resorted to my old stand-by of twisting the wires to take up slack.

View attachment 45021

But I hate it, and it looks terrible, and this is supposed to be my no-compromises luxury build (as opposed to my kludged-together Electrohub), so I un-twisted it and tried something else.

View attachment 45022

At least this looks neat, if not ultra-luxe. One challenge is that, in order to fold the legs, you need a bit of extra slack in the wires, to allow the arms to pull out. This makes a bend in the wires that has some danger of coming up into the prop, if you're not careful. I'm not sure how best to manage this. I could certainly re-solder the wires a bit shorter, but I'm not sure I want to go through all that work.

If anybody has any input on how to do professional looking wire-wrap, please let me know. For the time being, the only thing I can think of is to use bullet connectors that would allow me to easily install the wire wrap without having to apply heat to the motor wires with the wrap installed.

Here's a quick shot of the camera install. My camera has a bracket, so I'm not using the board camera plate that comes with the frame. It's installed to a pre-existing frame slot with an M3 screw and nylock nut. Then I use some layers of foam tape to hold the camera at the desired angle, which for the time being is level with the horizon, although I will probably be tilting it up eventually.

View attachment 45023

Finally, I need a bit of advice as to how to mount the antennas. I have heard of people using heat shrink and coffee stirrers, but I'm not sure how people are actually connecting these things to the frame. I could come up with something, but if there is a neat and elegant solution that others have figured out, I'd love to hear it.

so i used an old nitro rc antenna tube cut it down to size i liked and used heat shrink to hold your quad antenna to the tube and the use another heat shrink piece to hold it to the vertical frame bar. make sense lol?

 

[SHIFFTY]

here is a crapy picture if you can make it out

 

[joshuabardwell]

View attachment 45048
here is a crapy picture if you can make it out

Thanks. That's clever.

 

[SHIFFTY]

Your welcome, not the cleanest or pretty way but it seems to work well and allows for the antenna to bend if it has to upon a wreck or going through tight spots.

 

[joshuabardwell]

Here is an update.

I maidened it today, LOS. At first, it had terrible oscillations, even with P values as low as 2. Then I realized that I had the looptime set at 1666 (600 Hz ESC's) and had apparently never changed it back to 2500 like I meant to. After setting it to 2500, the quad flew great. Well, it hovered great. I put the P values back up to around 5 and started rolling the quad abruptly to one side to look for oscillations. WOW! It is much snappier than my Electrohub! I was doing great until all of the sudden, I pushed the stick too far, and before I knew it, the quad flipped all the way over and landed on its head. I had downloaded the suggested tuning values from RedRotor, and it turns out Pitch/Roll Rate of 0.8 and Expo of 0.6 is just perfect for me to get myself into trouble. Enough expo that I think I can fly it while hovering, and enough rate that I turn myself onto my own head as soon as I actually bang the stick a little.

A WORD TO BEGINNERS: Set the Pitch/Roll rate at something like 0.5 to start with and work up. I could fly my ElectroHub at 100% rates no problem, but this is a whole other world.

One ESC's motor wires were nicked in the crash, so I decided the best way to fix it would be to desolder the wires from the ESC and replace them. Unfortunately, there is a glob of glue on top of the receiver wires, and it pulled the signal wire's pad off of the board when I removed the heat shrink. So I think I have to get a replacement ESC now, unfortunately. I'm kind of disappointed that the ZTW ESC broke so easily, although maybe that's a normal part of life when dealing with tiny ESCs like this.

One lesson of the experience is that the way I mounted the ESC's isn't ideal. They're mounted in such a way that if the prop is deflected (e.g. by the copter landing upside down) the prop can hit the ESC. I'm going to move them further into the frame so that they can't be hit by the props at all.

 

[joshuabardwell]

PS: I had the thought to video the maiden, but I figured it would probably be so boring it wasn't worth it. LOL.

 

[joshuabardwell]

Okay, so after some consideration, I've decided to swap over to the F12-A Fire Red series ESCs from RTFQuads. In the past, I have spoken out about the slow customer service from RTFQuads, but I looked at what ESC's RedRotor recommends, and these were at the top of the list. They come with BLheli 13.1 pre-flashed on them, they have an SBEC to power the FC with, and they are freaking $8 a piece. Given all that, I will suck it up if the shipping turns out to be slow.

Why did I decide to switch to a different ESC? The main reason is that the little ZTWs don't actually fit well in the frame. The problem is that the frame has some gaps in it, and it is intended that the ESC's will bridge this gap, but the ZTWs are small enough that they just fall into the gap and kind of have nowhere to attach to, except on the edge of the frame, where they are susceptible to being hit by the prop. The ZTWs don't have BECs, which I knew when I bought them, but I hadn't considered that it would mean that I would need to pull power off of the 5v pin at the front of the quad, which means there's an additional wire cluttering up the build. It's a small, petty thing to care about, but darn it I don't want to compromise on this build, and it feels like a kludge and just bugs me.

EDIT: Received tracking info for the shipment 4/16. Encouraging.