Any issues or questions during the build, you can email us at bristolbotbuilders@gmail.com or message us on facebook, we’ll be happy to help!
As well as the parts included in the Featherweight Drive kit you will need the following:
- A 3-5S lipo battery in the 2-3000mAh range. (If this is your first feather we recommend a 3S 2200mah lipo.)
- A lipo balance charger that can charge that lipo (we like the Turningy Accucel-6)
- A transmitter (we like the Flysky i6 and it comes with a receiver)
- a receiver if you did not select one in the kit – make sure it supports your transmitter.
Tools you will need:
- 2.5mm Hex Key
- Cross head screwdriver
- Pliers or something to grip the motor shaft
- Cordless Drill to attach mounts to your robot with either:
- woodscrews, barrel nuts or screw inserts.
- Optional Electrical Tape
- Optional Blue Threadlock
- Optional M5 Tap
Building a featherweight chassis
This section is going to be really vague as there’s tonnes of ways to build and you should do what suits you!
Generally the construction of featherweights *can* be very similar to beetleweights.
At BBB we’re huge fans of HDPE and if you want to take our approach we’d generally advise 10mm thick baseplates and 20mm thick walls as a good starting point. Woodscrews can be used to mount together these panels, but for super strong results use barrel nuts (M5 is a good size) to join walls together! We’ve not had great results using screw inserts for holding base/top plates in HDPE for full combat as they tend to tear out under spinner hits, but should be fine for non-spinner fights.
Metal chassis are much more common at featherweight than beetleweight too – both mild steel and hardox. There’s even scope for a wooden chassis if you made it really thick!
One of our findings is the 13.6kg weight leaves you with a lot more weight to play with once you’ve done the drive system, relative to beetles – if you build a basic 2WD pusher with HDPE panels mentioned above you’ll have absolutely tonnes of weight to play with (possibly even half the weight left!). As our focus with the BBB feather “BEVS” events is entertaining fights and humour, we’d really advise using that extra weight to add a weapon and decorative features!
Good ways to add a weapon is using an extra drill or two for a grabber or lifter (a bit like a servo) or a linear actuator for a more linear motion. Axes are typically powered by small electric scooter motors. We’re just giving you some inspiration, our aim is to give you the core parts to get a featherweight driving and then you add your personal spin to that! So with that, let’s get that drive kit working
Motor prep – locking the clutch
At the heart of most featherweights are trusty drill motors – in our kit these come pre-removed from the drill casing. Drills come with an adjustable clutch that allows it the motor slip and control how much force is outputted from the gearbox. This is not what we want for a combat robot – we want all the torque, no slip!
Watch from 4:12 – 6:49 of this great video from Angus of Makers Muse fame demonstrate how to lock a clutch and how that actually works! We’re using shorter grub screws in this kit than he does so they’ll go inside the gearbox rather than stick out.
Using a 2.5mm hex key, you’ll screw the 4 included M5 grub screws into the gearbox. I do this without tapping, but some people like to use an M5 tap to cut a few threads into the start of the hole to make inserting the grub screws easier. It requires a fair amount of force to screw into the holes.
Carefully screw the grub screw down into the gearbox until you feel it just touch the output plate inside and then back it off half a turn. The grub screw will be pretty much flush with the hole.
You don’t want to be putting pressure on the output plate – you should be able to wiggle the output shaft back and forth a small amount feel the bump as the ring gear hits against the grub screws.
You’ll want to repeat this for all four grub screws in every second hole of the gearbox.
At this point it’s worth adding some electrical tape over the vent ports at the back of the motor to stop debris from getting in – they don’t need ventilation for 3 minute fights.
Mounting the Motors
This bit is pretty simple! The front face of the gearbox sits inside the front mount and then is attached from the other side by screwing in the the two included wood screws. The back mount slides straight on behind the gearbox.
You can then attach this to the baseplate or in my case top plate of your robot. I used 5mm woodscrews, but if you want a more reusable option you could use barrel nuts or screw inserts in the mounts.
I used two woodscrews for the front mounting plate and two for the back . The front and back mounting holes are ~61mm apart from each other, but it’s best to measure on your robot to ensure the motors are well clamped.
Attaching the wheels
Our wheels come with a threaded hub – screw them on to the motor shaft by hand, and tighten a bit while gripping the shaft with some pliers or similar.
Then take the M5 20mm reverse threaded screw that comes with the motor and screw it by hand with a cross head screwdriver into the shaft through the hole in the wheel – note it’s reverse threaded so turn left to tighten otherwise you could damage the shaft thread! Make sure it’s fully tightened.
After a good bit of drive testing, my wheels were well attached to the motors and very difficult to remove, however if you’re having issues with wheels coming off you can use blue threadlock on the reverse threaded screw to help it stay in place. You can even do the same with the motor shaft, but bare in mind this makes removing the wheel much harder later!
A great upgrade to the wheels is to attach bike tyre with small woodscrews to add extra grip. This will wear down after a few events and need replacing to maintain good grip / pushing power! Also bare in mind this changes the diameter of your wheels quite significantly so think about ground clearance/chassis height etc!
Electronics
This is another area that’s really similar to beetles. So I’ll start with our beetleweight circuit diagram, made by the legendary Nick of Team DSC:
This diagram totally applies to feathers too! So we’ve included our safety kit, but with larger 60A fuse wire. The 12V LED is fine for 4S, but we’d recommend finding a higher voltage power light for 5S!
Here’s a circuit made from the kit soldered by Ross:
He’s using an external BEC so will remove the red wire from the servo connector of each ESC.
With our 18V motors we’d recommend a lipo anywhere between 3 and 5S and somewhere in the 2000-3000mah range.
We’d really recommend 3S if you’re just getting started as it’s cheap and most likely if you’ve worked with beetles your charger will work with it. If you’re feeling confident 5S will give you more speed/power on our 18V drills! Our BBB Feather ESCs will support two drills per side if you decide to do four wheel drive.
Be sure to only use one BEC in your bot to power your receiver, we generally recommend using an external BEC, but if you want to use one off your ESC of the two drive ESC – disable the other by cutting the red wire off the servo connector. If you use an external BEC, cut the red wire on all ESCs’ servo connectors in your bot.
Binding Receiver to Transmitter, Mixing to set up drive
We cover all of this in our ant kit guide and it’s exactly the same setup here! Here are the links:
Add a weapon
That’s pretty much all the steps to making a driving chassis! Any questions please email us at bristolbotbuilders@gmail.com or post in the facebook group!
We’ve also written a guide to adding a BEVs suitable weapon! Check that out here.
Thanks for reading 🙂
– Joe