Building FPV RC CAR from old drone parts

Copy and pasted from the other topic, and making a seperate one for this.

Now I can print my own parts I'm going to try to make an rc car using old drone parts.
Searched on youtube and found several videos/tutorials on how to do it, I don't have to buy anything.
Already gathered all the electronics and other stuff I need for the build.



Here's an example of an rc car made from drone parts:
Not going to make mine exactly the same though.



The guy that made the rc car video from above also made a video that shows the Betaflight settings he used.
But the way he set it up it can only drive forward, going to try set it up in 3D, so I can drive backwards too.
He also included a link to a printfile for the wheels. [https://cults3d.com/fr/mod%C3%A8le-3d/jeu/roues-pour-voiture-fpv]

Checked all the electronics and so far everything is working fine, including receiver link to the radio and arming.
Even the old batteries seem ok, though not sure about the performance, and still must be extra careful when recharging.
Now thinking about whether to print some 90 degree standoffs for the wheels and use the drone frame, or design and print an entire new frame.

Little update on the fpv rc mini car build.  
All the red parts are made by me (excluding the tire rims).
Used the ones from the download link above for scale of the motor axis.
Only the carbody is downloaded and modified a bit.
May need to print the body in 2 parts as it's just too big for the printer, 
or maybe modify it a bit more, so I can print it as 1 part, but it looks cool like this.
btw That bar around the wheels is to secure the axis of the motors.
Because the dronemotors are not designed too work as carwheels and,
the axis are pretty weak and probably won't last very long without securing them.



[https://ibb.co/Px2JL2K]

[https://ibb.co/5LZ9c6J]

Couldn't resize the carbody without having to rescale and redesign the entire car.
Eventually it turned out to be a good thing because now I also know where to place all the electronics and camera.
I rescaled the body to fit the printer build plate, so I can print it in 1 piece.

OMG   So stupid... I realised I could print the carbody without resizing after all by rotating it 90 degrees and print it nose first.
The printer would have almost reached max height for it, but it is possible. Funny I had not thought of that at all, till just now..  

Almost finished printing the car body.

Came out pretty good, the front window frame is a bit thin, but the rest seems strong enough to handle a couple of crashes.
Will be printing some of the other parts later today.

Finally done printing all the parts, can start building now.  

Had a little trouble printing with the pink resin, which I had not used before.
Caused some failed prints, but no serious damage, and I learned some stuff.
Can still use parts of the failed prints, so it's not a complete waste of resin and time.

Also had to redo the entire spring dampening system because I had mixed up radius and diameter in 3dsmax.
I know, it's very stupid, but easy mistake to make going from cylinder to spiral object, so I don't feel too bad about it...
Eventually all the prints came out perfectly fitting and scaled exactly as I made it in 3dsmax.

Here are some pics of the parts

Got the wheels and springs done.  
Unfortunately I had to remove part of the wheelbar I made to fix the axis, because it was almost impossible to install the wheels.
At least the spring system works fine.

Done salvaging all the electronics, and ready to install everything in the car.
Also including some leds so the semitransparent car body and frame will glow.

Was a bit of a puzzle to make it all fit, but starting to look like something.

Made the leds on the inside of the carbody with a seperate plug so I can still easily remove the carbody when needed. 
At the moment I used sticky tape, but now I know how to make it fit, I will look for a better way to attach the leds more permanently. 
May add some more leds, if I can find a place to put them. btw these leds are so bright they light up the entire room.

Fixed the leds by using the soldering iron to melt a couple of holes in the carbody and then used regular standoffs.
Most of the stickytape is gone now, only using a small piece of tape to keep couple of wires in place.

Pic of the electronics, everything fits, but absolutely no space left.
Only have to permanently install it on the car frame and then most of the building part is finished.

Last I plan to do is try to replace the wheels with a couple of paint rollers.
These things are perfect to use as wheel, if I can think of a way to attach them to the motors.
Besides a little springy and dampening, the paint rollers are wide, so the car can't flip over when making sudden turns.

Finished the electronics, got the fpv feed going, everything works so far. 
Next step is setting up Betaflight, configuring the motors, etc.
And finally try and replace the wheels with paintrollers.

Finally done setting up Betaflight and the transmitter.  
Everything is working as it should, except... the wheels are too smooth.
The car can drive back and forth, but not make turns cause the wheels slip too much.
Already thought the wheels wouldn't perform that great, but not that it would be this bad.
Was planning on replacing the wheels anyway, so that's what I'll be doing next.

Replaced the wheels, but still unable to steer the car, even though everything is set up correctly, plus 3D mode enabled.
The wheels turn left side and right side, as I move the gimbal, so the controls are working, but the car won´t turn.
Still can try some stuff, but maybe 3Dmode just doesn´t work for some reason.
Only difference I noticed in the video from the first post which shows the Betaflight configuration, was the´flip over after crash´ switch.
Had not realised why this switch was active, normally used for ´turtle mode´ when your quad landed upside down.
It is a switch to reverse the props/throttle, which then ofcourse allows to drive backward, funny I missed that completely.
So now I´m going to undo 3Dmode and try use normal setup exactly as shown in the example, this time with a switch to reverse.

Well.., that went different than expected.  

After undoing the 3D settings and following the normal set up as in the video, it still would not work.
The throttle worked as supposed, but no yaw roll or pitch for steering, the motors would not spin.
In Betaflight I can see that the channels are reacting to the stick input, so the receiver is working properly.
Eventually I decided to reset entire Betaflight and try setting it up from default.
At some point I wanted to try out if the new settings had any effect.
Already being careful, because if the throttle settings are off, the motors can start spinning wildly, and I wanted to prevent that.
I flipped the arm switch on and off quickly, and indeed the motors started spinning like crazy, but then the arm switch failed to disable.
The whole car started bouncing as the motors went full speed, had to catch it and unplug the battery.
Most of the spring system could not handle the violence, and needs to be reprinted and replaced, but I'll just remove it for now.
Going to try a little more, but if I can't get the steering to work, maybe I'm just going to buy a real rc car.
Just don't want to give up too quick as I am at 99% of finishing the build.

Making good progress, think I fixed the steering problem.
The problem was that the endpoints from the transmitter and receiver were screwed and a reset was needed to fix it.
Made a new profile on the transmitter and had to reset Betaflight again, and after that the steering seems to work as supposed to.
Now first need to do some repairs on the car, before I can do a test drive.

After fixing the car, so it could drive again, I managed to make some turns.
But it's not great, the car drives too fast at the slowest speed the motors can turn.
And because I kept bumping into stuff I really needed the abillity to drive backwards also.
So I tried to set up a switch to reverse the car, but this works different than I expected.
To reverse the car I'd need to disarm, switch to reverse, and re-arm again, which kinda sucks.
I decided to go back to 3Dmode, but now I have the same problem as before, motors start spinning fast after arming.
For safety I had lowered the motor max rpm so the motors wouldn't spin too fast if anything went wrong this time.
The motors are 2600kv on a 4S 14,8V battery, so normally at half throttle the motors spin at around 20000rpm.
(I just realise maybe a lower voltage battery could help make the car go slower
But I don't have lower than 3S, and those batteries are too big to fit on the car.)

Somehow the throttle channel range is a bit screwy, but I don't know why it happens.
At least I found out what's going wrong, now trying to figure out how to fix it.
I had 3Dmode throttle working correctly before, so I know it can work.
By now I just want to finish this little project and get on with the next thing.
Already decided I want to get a proper rc car, and just put a fpv camera on that.