Gunblade Build Diary - FW spinner

[COAESystems]

Hello everyone,

So it's time to take a leap of faith, combine the best bits of my featherweight design for Flatfish and my beetleweight horizontal spinner Naginata. It's time to build a featherweight horizontal spinner! The name follows the French weapon concept, the Gun Blade, also inspired by Final Fantasy VIII.

This is still early planning stage, so my first question will be:

Is a chain drive or belt drive better for a featherweight horizontal? I've seen chain drive on some American robots.

Also, would an M12 steel bar be enough to take the forces involved with a featherweight spinner?

More planning and likely CAD to follow!

[COAESystems]

So I answered one of my questions straight away, 20mm centre hole looks a lot more suited to the bar spinner than the 12mm centre design. I scaled up the beetleweight bar to give me a 1.4kg featherweight bar, which should be heavy enough for the job.

FWGunBlade_20mmcentrebarspinnah.png

[Ocracoke]

Is a chain drive or belt drive better for a featherweight horizontal? I've seen chain drive on some American robots.

Belt. Easily, it'll slip on excessive torque and not snap like a chain might I'd imagine.

[McMullet]

My understanding from other people's spinners is that you have to have some give in the system, so if you use a non-flexible drive from the motor to the spinner (chains or gears) you have to include a clutch/torque limiter somewhere or you risk destroying your motor or transmission. So a belt isn't essential but it seems much easier!

Edit: Also, good luck!

[COAESystems]

So, a quick update!

Firstly, I now have all the belts and pulleys required for the spinner assembly, and have cut the steel centre bar for the spinner down to a few cm above my final cut size (to double check I'm not cutting it too short before the rest of the spinner parts arrive!)

Based on an approximate robot height of 14cm, I modelled the first draft of the basic robot chassis with 16cm diameter wheels. Like Naginata, I will cut these wheels myself out of HDPE, and add grub screws to hold the wheels onto the main drive motor/gearbox assembly. I've got a screenshot of the basic robot shape now, which turned out to be an arrowhead cut from standard 50x50cm HDPE. Looking good so far!

FWGunBlade_basic3Dmodel1.png

[Ocracoke]

Looks neat. How do you add the grub screws to the wheels though? Do you cut a circle of HDPE and then lathe down to create a hub as part of the wheel so that you can drill that for the screw?

[COAESystems]

Looks neat. How do you add the grub screws to the wheels though? Do you cut a circle of HDPE and then lathe down to create a hub as part of the wheel so that you can drill that for the screw?

Yeah, it will be similar to Naginata 2's wheels where there is 2 grub screws sandwiched onto the motor shaft which has an extra flat ground out on the other side. For the featherweight I may be able to drill through the motor shaft for a better solution. 20200131_180237.jpg

[Ocracoke]

I'd recommend that.

[COAESystems]

So, after the lockdown slowed progress, I managed to get the plastic panels ordered, and have done my first outline of the robot shape. I'll make a template from wood before committing to the cut.

20200502_120740.jpg

[Ocracoke]

Looks good, better than the outlining I did for my robots :P How thick is the base?

[COAESystems]

Looks good, better than the outlining I did for my robots :P How thick is the base?

Gone for 15mm thick HDPE, that's more than my first featherweight, and similar for the wheels

[Ocracoke]

Sounds good. Azriel uses 15mm HDPE for its side panels, been durable enough so far

[COAESystems]

This is the first build diary vlog (summary), currently the next step is to cut the plastic along those marked lines. Metal parts to support the weapon shaft and attach the wheels to the motors are ordered.

https://www.youtube.com/watch?v=5tSI-zIXK9Q

[Maxamuslead]

hey dude, how are things? few things 1 is the frame holding the weapon also 15mm ? and 2 also what weapon motor you thinking ? htd 5m belts are what most FW spinners use in the uk. one last thing where you gonna run it ?

[COAESystems]

hey dude, how are things? few things 1 is the frame holding the weapon also 15mm ? and 2 also what weapon motor you thinking ? htd 5m belts are what most FW spinners use in the uk. one last thing where you gonna run it ?

The weapon shaft will be held in by flat 5mm steel plates sandwiching the HDPE frame, with an extra square of 15mm HDPE at the top, easier to explain in pictures when it all comes together!

The weapon motor is a brushless motor from Overlander UK, it runs up to 6S but I'll be running it on 5S. I've calculated the tip speed will be 160mph, so the kinetic energy is a lot higher than my Beetleweight spinner. I've reinforced it a lot knowing the forces involved.

The plan is to run it at Robodojo or Extreme Robots, and as the build is progressing slowly I'm likely to have it done by the end of the year.