First Ever Robot Build: Invertible Featherweight Vertical Disc Spinner

[TheNeonMatt]

This is my first ever robot build and after reading a bit on this forum and watching some featherweight videos on youtube I have decided to try and build (as the title says) a featherweight disc spinner that is also invertible. So far I have decided to use two cheap 12V 550W drill motors for drive and probably two Turnigy 85A ESCs that I plan to try and hack myself, not yet sure on the weapon stats as I'm planning to attach everything drive wise to a chopping board as a test run and work from there.. I don't know the dimensions of all the internals but once I have them I will adjust my google sketchup plans to include them. Any help on materials and thicknesses would be extremely useful as I haven't sorted any of that out yet, (I only have basic tools at the moment so was looking at a HDPE structure with metal plating in places, I'm also planning to get a drill mount/pillar drill to make accurate holes)


Here are my basic plans that let me get the shape and rough size and I'm also planning to add a hinged wedge to the back:

Any help on the design, components, and weapon would be appreciated.

[Niels - Team K.a.L.M.]

First up, welcome.

Try placing the dics and the wheels closer together. This will reduce the gyro effects a little.

[TheNeonMatt]

Thanks for the advice

I saw them talking about that with Archangel in the Hardwire 2 Build diary and have tried to bring them closer but it will either mean I have to make a smaller disc or a steeper angle on the wedge. Does a particular angle work better on a wedge? Also how does the disc size relate to the hit? I understand how weight affects rpm as in more weight is harder to spin up to speed but I've heard stuff like bite (I think is theoretical amount of the tooth on the opponent), KE (I'm guessing is kinetic energy of the disc) and KV but I don't fully understand how they relate to one another.

Finally would a larger base help stop gyro or am I looking at it wrong?

[maddox10]

Hi NeonMatt.

On the pillar drill. Even when you're not building a robot, it's a dandy tool to have.
But, don't buy too small. The £75 versions from Ebay or the DIY are capable enough for basic feathers or smaller machines. But the small motor will struggle with the better materials or bigger holes in metal. Especialy when using cheap and/or blunt drills. Better to safe up for a bigger one with a 500W or better motor.

On the TZ85's. For a basic drill drive, the BotBitz 30 A speedo is more than good enough.
Also, I myself buy TZ85's from BotBitz. Not worth my time to reprogram those myself.


KV stands for rpm per volt input. A 1000 KV motor will run 5000 rpm on 5V.

Kinetic energy aka KE. The faster a weight is moving, the more force will be in that object. A slow light disk will contain less force than a fast heavy disk.
Keep the same speed and double the weight, and the force contained in the disk will be doubled.
Kep the weight and double the speed, and the force contained in the disk will quadruple.

Wheel placement and such. In a vertical spinner the wider the wheels from each other, the less the gyro effect. The closer to the axle of the disk, the more weight on the wheels, so more control/torque availabe.

[TheNeonMatt]

For a basic drill drive, the BotBitz 30 A speedo is more than good enough.

If my drill motor is 12V and 550W it means it is just under 46A, does that mean I need a different speed controller?

[Max]

Sorry for the thread hijack but I've got a 650W pillar drill and it struggles even drilling a 6mm hole in mild steel, the motor itself does not stall but the belts slip even in it's lowest gear ratio. Any ideas why this is happening? Should I replace the belts with slightly smaller ones?

[overkill]

Sorry for the thread hijack but I've got a 650W pillar drill and it struggles even drilling a 6mm hole in mild steel, the motor itself does not stall but the belts slip even in it's lowest gear ratio. Any ideas why this is happening? Should I replace the belts with slightly smaller ones?

The belts that come with cheap bench drills are usually complete crap. Try replacing the belts with cogged versions as they have more grip. You can usually get cogged belts at engineering or auto spares stores, or on line. There should be a short tensioning lever somewhere of the drill head; adding a length of pipe to the lever lets you get much higher tension on the belts.

[harry hills]

Either that or add a tensioner.

[RogueTwoRobots]

Has your pillar drill motor got a spring/tightening bolt on it? On my 500W pillar drill, the motor is on a hinge. When I want to change the belt ratio, I slacken the bolt and it releases the tension from the system and the motor hinges towards the front of the drill. Once I've moved the belt onto the other pulleys, I push the motor back against the spring, re-tensioning the transmission, then tighten up the bolt which holds the motor in place.

My drill was slipping at first until I got the hang of that, but now it gets through steel without issue.

[Flag Captured]

Welcome!

Personally, I'd have a good look at Gary (typhoon_driver)'s machine Hornet 2 because it reminds me of that sort of design, may be able to pick up a few ideas there!

I do feel like the wheels are a little too far back, perhaps you could shorten the bulkheads and beef up the body a little? The disc can easily cut into the body shape as long as you design it right. Archangel's will be doing that for the most part, to try and get everything as compact as I can to save on weight, I guess. Also means that all the weight is on top of the wheels and so you'll get more grip, Will (Team_Shock) wrote loads of helpful tips from his experience with the various versions of Inertia XL on my build thread, definitely read that if you can find it (amongst the posts of me pretending progress is happening when it really isn't)

S3 from robot wars could be a nice design start-point too, now that I think about it, may be a little too big if the disc you want is larger, but it's certainly something to look at. What size/speed weapon would you want on this? That definitely is something you'll want to decide on before going too far with your design, given you'll need to contain all the energy in it too - it's all well and good having a monster of a weapon, but you need to make sure your bulkheads are up to the task too, so that it doesn't chew itself up after a few hits.

What sort of dimensions and all that were you thinking for the disc/wheels too? That might help out a starting point on exactly what parts you'll need for it all. For reference, Inertia XL's disc is about 300mm diameter and I believe that Hornet 2's was pretty similar. I think Maddox's Valkiri is one of the bigger verticals about at around 400mm on the disc, and most of those are about 2-3kg in weight from what I remember hearing. May be of some use to you when designing, possibly!