December 30, 2017

Wall mounts for my RC cars

I designed (if you can call it that) and printed simple wall mounts for my RC cars this weekend.

This is how 5 of the prints turned out. My printer needs a lot of love to print. But when it prints it prints well. I had not given it enough love apparently. But when I took the time I got it back to friendly operation again.

And then this was the result. Simple wall mounts to hang the car by the tire. Turned out I actually only needed the middle screw hole.

The mounts in "action" with the cars dangling by the front tire. Haters gonna say it's bad for something in the suspension obviously.

The hanger is available on thingiverse for the ones that would want to print their own:

Final flight of the F-35

Last time I flew it I broke its nose. That was two years ago. After the nose was broken off, it might have been ugly, but it flew well.

And today was the day to fly it for the last time. Since I do not expect to fly this plane any more and it is ugly and taking up precious space, it was time to get rid of it. With a few final flights.

To spice things up I had 4S batteries prepared. ESC and motor is speced at 2-3S.

Away it went. My friend gave it a perfect toss and the power of 4S made it fly perfectly. It was fantastic. For about 10 seconds, then I misjudged the distance to a tree and the plane was converted to garbage.

Collected remains of the F-35

December 17, 2017

Futaba replacement?

Well hello there dear old blog! It's been a while now. I haven't forgotten about you, I just haven't done much on the bench lately.

BUT. I did get myself a radio on the HobbyKing sale maybe a month back. Being a Futaba fanboy, I never expected that I would ever in my life buy a Flysky system. But now I have, I got myself a Turnigy Evolution. I've been looking at alternatives to the bulky Futaba, at least for the leasure flying I do at the office and now that it was on sale I ordered the Evolution at 35€, incluing a receiver.

60€ radio to the left, 600€ radio to the right

Ok. So, there's a small price difference between the 14SG and the Evolution. Don't get me wrong. The 14SG is a flawless radio, at least by the time it was launched. It has never ever glitched in the transmission and the telemetry was a great addition and quite unique in the price range before the Taranis arrived. I really love that radio.

But for flying quads, especially indoors I need two major features.

  • 6 channels
  • Voltage telemetry
And the Evolution has that. Yes, it has telemetry. And the receivers are dirty cheap. And the radio was dirt cheap. In fact, I think I can outfit most of my rotor crafts with receivers for the price of one single Futaba receiver. 

But how bad can it be? I'll get back on that if I have issues with it.

I will not forget to mention there are alternatives to the Evolution out there as well. One of them is the TBS Tango. It's a purpose built radio for quad racing and has some nice features in therms of programming. It is quite expensive, and comes without a transmitter. Which makes it ridicously expensive.

And coming up is a multi protocol radio called iRangeX iRX-IR8M. It looks like a knockoff of the TBS Tango and comes with multiple radio circuits built-in. I won't order one until there are some decent reviews online. My guess is that it will have a bit better gimbals than the Evolution and a poor feature set in the software. It's mostly the form factor, the basic telemetry and the multi protocol feature that will push this product.

October 14, 2017

"Fixed" the z-slop issue on my Fabrikator 2

So. I've finally worked out an extremely simple solution to the Z-slop issues I've had with my Fabrikator II.

The problem with the Z-axis is a combination of two issues with the printer.

  • The Z-backlash prevention mechanism is poorly designed
  • The Z-axis does not run smoothly and has to be forcefully pulled down by the Z-axis rod
The obvious solution would be to address those issues. And I have tried, but can't get the Z-axis to run smoothly enough.

What happens because of this is the there is a 0.2-0.4 mm slop in the Z-axis when it descends and then starts climbing again. This happens when the print starts (home, lift, descend to first position) and whenever a lift is done during the print. As an effect the printer will print 2 or 3 layers at the same height, causing the printer to print badly and the model to be of incorrect height.

So far I've only printed parts in the printer where the effects of this issue is not problematic. Which is quite limiting.

After a bit of googling gcode I realized I can solve the issue at the print start with only a bit of fiddling with the pre start gcode snippet. By default in Cura it looks something like this:

G28 ;Home
G1 Z15.0 F6000 ;Move the platform down 15mm
;Prime the extruder
G92 E0
G1 F200 E3
G92 E0

One of the important parts to notice here is the "move down" which on this printer is actually a "lift" part. It is when the printer comes down from this movement and starts moving up again that the problem will occur and the printer will put down multiple layers at the same height. So we can remove that line.

But the homing process will still have the same problem. The last movement of the homeing process is the Z-axis descending until the endstop swith is triggered. After this, the first 0.2-0.4mm of any up movement by the Z-axis stepper and rod will not result in movement of the print head. To counter this the entire build must offset to move the entire model up and prevent this initial slop.

This turned out easier than I expected. By using the G92 an axis position can be adjusted. This will introduce the offset needed and will effectively cause an initial lift of the given value. So I added this command as the last initial command before the print. The resulting Start Gcode now looks like this.

G28 ;Home
;G1 Z15.0 F6000 ;Move the platform down 15mm
;Prime the extruder
G92 E0
G1 F200 E3
G92 E0
;Set the Z-position with offset to counter fab2 z-backlash issue
G92 Z-0.2

This will cause my prints to turn out good and not need any further adjustments. The solution has two drawbacks.

  • The initial movement of the print head will traverse the bed at 0 height. This can cause issues, but might also wipe the nozzle. Which is not always a good thing if it happens at a less preferable location.
  • The print cannot contain any lifts. Prints that would benefit from lifts can still not be printer with this printer.
So. This solves my issue short term. But I should probably try to solve the mechanical issues as well to avoid this hack.

October 2, 2017

3 printers, 3 failures

I have 3 3D printers. I don't know how I ended up with 3 but here I am. I have 3 cheap 3D printers. And it annoys me. Cheap DIY printers are really good for learning. And I have learned a lot. But they are not good for every day 3D printer when you just want them to work.

Yesterday I was sketching a few parts for the kit of BRIO MEC that my children are playing with. I wanted to print a few simple pieces which do not exist in the kit and I think should be there to make a few new construction possibilities.

So I fired up my 3 printers to print 3 pieces at the same time. And I got 3 failed prints.

To the left is a piece from the Mini Fabrikator 1, which also goes under the name TinyBoy. What happened here is the build plate is sticking to the guide bars, and the belt skips. I had this problem in the beginning so it is not new. But it will need some work to clean it up.

In the middle is a piece from the Malyan M150. It is not visible, but the piece is warped. Not really the printers fault, this PLA material warps and I don't know why. Aside from the material issue here, what annoys me most about the M150 is that the bed is unleveling "itself" with time and I have to spend to adjusting it regularly. Not something you have time for every time.

To the right is a piece from the Fabrikator Mini 2. The main issue with this piece is that it is missing its first 0.5mm. Simply because the Z-axis anti backlash is flawed in design and the X-axis gantry is not running smoothly on the guide bars.

After this I will really start considering getting a better printer and selling/giving away some of the others that are to unreliable.

September 28, 2017

Bad day in the HGLRC factory

Zero fucks was given on that very day in the packaging department.

It's not even remotely difficult to put the board correctly in the box. Must have had a terrible day at work.

The board looks really great at first glance. Nice soldering and it is cleaned, which is not always the case with that china stuff.

September 19, 2017

FPV150 got 3 flights

The FPV150 was flying fantastically after the upgrade. But after about 5 minutes one of the ESCs started cutting out. I wasn't running low on voltage or anything and it seemed strange.

Anyway, to make a very long story short, it turns out it is probably faulty. I cannot connect to it with blheli configurator and I actually found in my old blog post that I had this problem with another ESC while building the first FPV150.

So I set out to order a new device. It turned out harder to find than I expected. I couldn't find one identical. Instead I ordered two ESCs from hobbyking with similar specs. I was quite surprised hobbyking didn't carry more variants of this small ESC. Any way, I got a Kingkong and a Multistar. Once upon a time I promised myself never ever to get a multistar again. They used to be real crap. But hey it's revision 16. Sixteen! Did they get it right this time?

I guess I'll find out in a few weeks once I get those props spinning again!