Deep Dive: Division V4 Design (Flywheel, Hubmotor, and more!)

This video is a long and detailed look at the design choices I made for Division V4 - my lastest beetleweight combat robot. Division V4 features a custom hubmotor weapon system, friction-driven flywheel counter-gyro, and many other unique design elements.
Thanks again to PCBWay for making the flywheel for Division V4! Check them out here: bit.ly/PCBWayJustCuz
Other videos referenced:
Division V4 Reveal • DIVISION VERSION 4.0 H...
V2 highlight reel • Division: Beetleweight...
V3 at Open Sauce • Spinning Steel vs Flam...
V3 some good fights: • Division V3.2: Norwalk...
Hubmotor CAD 5536: grabcad.com/library/rdy-5536-...
Just 'Cuz Robotics Website: justcuzrobotics.com/
Just 'Cuz Store: justcuzrobotics.com/shop
Support on Patreon! bit.ly/JCRPatreon
Try PCBWay's CNC Machining or PCB Fab using this link for a $5 new user credit: bit.ly/PCBWayJustCuz
Instagram: @JustCuzRobotics
/ justcuzrobotics
Bloodsport KZbin Channel
/ bnsrobotics
@bloodsport_battlebot
/ bloodsport_battlebot
Bloodsport/BnS Facebook Page:
/ bnsrobotics
#combatrobotics #beetleweight
Timestamps:
00:00 - V4 Design Intro
00:39 - Looking at Past Versions
03:30 - Materials and Construction
06:37 - Wiring Brief
07:35 - Drivetrain
08:27 - What Causes Gyro - Physics Lesson
11:21 - Gyro Design Math
14:13 - SPONSOR: PCBWAY
15:11 - Division V4 CAD - Flywheel
16:09 - Full Robot CAD
16:29 - Design for Repairability
17:23 - UHMW Uprights
18:47 - Drive motors
19:41 - Internal Electronics Layout
22:58 - Hubmotor Wire Routing
23:53 - Keep It Simple
25:04 - Invertibility
26:30 - Hubmotor Design
32:04 - Real Hubmotor Close Look
33:24 - Outro

[@thedumme103]

I don't have any questions. I just want to thank you for sharing your engineering thought processes in the V4 design. Your channel has inspired me to make a simple antweight this year as a personal challenge. I don't anticipate including a hub motor (or any weapon motors at that) in the design, but the breakdown of your much more engineering intense robot makes mine seem much less intimidating.

[@JustCuzRobotics]

That is great to hear, good luck with your new build!

[@subsnovideos-ur4cn]

The two things i thought division could use. A hub motor and a anti gyro wheel and you did both. This version is going to kick ass!

[@JustCuzRobotics]

A hub motor never would have worked with the previous design because I needed extra torque on the weapon to self right. The Hub motor has about as much peak power as the previous weapon motor but it has three times less torque on weapon because there's no belt reduction.

[@subsnovideos-ur4cn]

@@JustCuzRobotics i had the idea of you using a smaller diameter disc instead of a bar. Shorting the uprights and making it easier to self right.

[@alexsalchemy]

19:03 - My robot Cheesecake actually had a similar thing in the past: The motors would slide axially into a tube, motor first, bottom out on the gearbox, and then they were held in with an internal retaining ring against the face of the gearbox, rather than a flat faceplate. Your robot is a much better application of this than mine because you don't have wheel guards in the way of pulling the motors out for replacement.

[@JustCuzRobotics]

Oh that's cool! I cut it out for time because this video would be like an hour long but I had to start over this design 2 times before arriving here. My previous iteration had the motors mounted via a clamp from the back and molded in wheel guards like Fully Defined but I decided it required way too much material around the motor/gearbox to make room for the screws.

[@Julipapa]

I really enjoyed the detailed explanation of design decisions, etc. 👏

[@JustCuzRobotics]

Glad it was helpful!

[@Kinekitsu]

Coolest physics lesson I’ve ever had~ What an awesome design to solve the gyro problem verts have!🔥🔥🔥

[@gearedloop3195]

I like the look of division v3 because it looks spindly, but in a threatening and intentional way. I like the look of division v4 for the *CHONK. IT IS A VERY SOLID LAD.*

[@JustCuzRobotics]

It's definitely a very different Aesthetic but I think (hope) it will grow on people.

[@nWestie]

if you do end up getting black uprights made, I agree that that helps the look alot. It gives a very 'I am a brick that can take anything' whereas v3 seemed more feisty, wild, kinda vibes

[@nightrider5420]

Great video! Your skills never ceases to amaze me. 😎👍

[@DanSwart]

I will admit that I’ve been taking some inspiration from the various iterations of division for my own vertical spinner, but this new design is truly something else. The anti-gyro flywheel is genius, and the invertible body will almost certainly prove to be invaluable. I only wish I’d thought of making a flywheel before committing to a 10” diameter blade lol

[@TheRook12325]

Can’t wait to see the fight!

[@gsasagas]

It fought at last nhrl event.

[@gsasagas]

It fought at last nhrl event.

[@TheRook12325]

@@gsasagas that’s how I worded it yep

[@alexsalchemy]

25:06 - I absolutely love the invertibility of this design, that makes me happy :)

[@balcazar8529]

Thanks for sharing the hub motor cad, it will help me build my own!

[@LukeQuin]

Really like the hub motor. Nice work. Making hub motors is a pain.

[@JustCuzRobotics]

Thank you! It was a challenge to design for sure, but I had a lot of inspiration from other successful bots. Primarily the 12lb bot Chronus (Mk2) by Julien Mott, and to a lesser extent Synthesis 3lb.

[@jo-e246]

Maybe use capacitors to gain discharge rate? Would need some time to recover in between spinups, but may save some space/weight.

[@penelo9114]

I'm eager to see it in action ^^

[@jinwonlee3105]

Amazing video, wondering if you'll be doing an in depth video on division V4's electonics.

[@JustCuzRobotics]

I covered some of that in this video, what specifically do you want to know about?

[@jinwonlee3105]

@@JustCuzRobotics I'm really interested in the drive train esc's and if your using am32 or bl32 and why you chose it.

[@most_displeased_customer1209]

Any plans for HW sized hub motors further down the road? Also cool and super informative video. I wanna see a heavyweight vert with a hub motor but they're seldom if ever widely used at that level.

[@JustCuzRobotics]

Heavyweights are a bit too custom for a one size fits all product like that. NHRL is just one (big) league and within NHRL there are about 400-500 Beetleweight robots that compete each year according to their rankings. Heavyweights are a miniscule market by comparison with only a handful made for a new season of Battlebots. It would be prohibitively expensive to develop a motor just for heavies.

[@most_displeased_customer1209]

@@JustCuzRobotics ok thanks for your reply. It would be cool if like somebody found a way to reduce te cost of heavies to a point where it made a lot of sense for more people to become involved cos cost is obviously one of the most prohibitive aspects of robot fighting along with the technical elements I think.

[@prodgbm]

Do you plan on making any more kits or weapon setups for antweight robots in the future? More specifically would you be selling a hubmotor for ants?

[@JustCuzRobotics]

I may or may not have already started designing a smaller hubmotor...

[@americankiwi]

With quite a few fire or heat based weapons in the 3lb class, how do you plan to protect it from a fire or heat attack? Love the updates, and can’t wait to see it in the cage.

[@JustCuzRobotics]

I don't have a great plan besides a lot of foil tape. I think flamethrowers are still very rare though. If I had to I could print the chassis from a rigid but fire resistant plastic for that occasion.

[@mw4222]

Could there be a version of the hubmotor that accepts much wider blades? The current geometry seems to be for thinner blades and bars only if you don't want the blade to be off center.

[@JustCuzRobotics]

Having the blade off center isnt a big deal, I think up to 1/2 inch is doable with longer M4 screws. It's sorta designed around 1/4" as that's extremely common in Beetles. It would be pretty expensive to make a small volume run just for people with OCD who want the blade centered with a thicker one tho.

[@allenroughton]

Maybe I misunderstood something, but you mentioned you can run it without the flywheel to keep it under 3lbs, so does that mean with the flywheel it's over the weight limit? Or is extra weight allowed because it's part of the locomotion mechanism?

[@JustCuzRobotics]

NHRL specifically has weird rules. At NHRL you can have 4 pounds total if you have a "multibot", so I have a little robot called Remainder which is 200 grams (0.44lbs) which allows Division to weight up to 3.56lbs. With the flywheel and long front forks which is Division;s heaviest configuration its like 3.44lbs. I also can actually get Division with the flywheel just under 3lbs if I remove the front end attachments (wedge/forks and their TPU mounts) and run without the minibot then.

[@Termini_Man]

What if you set up a gyro wheel that was powered separately from the disk. To make it compact and lightweight, it would be an outrunner motor with a hoop flywheel. then, encasing all of this would be a thin pressure body, where the inside would be a vacuum. This allows the flywheel to spin very fast with little air resistance. The motor would not need to be very powerful. it would need to be optimized for efficiency to reduce the heat produced by the windings. heat created in the magnets via eddy currents would just diffuse to the rotor and casing via black body radiation (although might need to use high temperature magnets.) or perhaps it could also be a vacuum with a small amount of helium, which should have little air resistance, while letting it cool via convection. I have no idea if this would work or be practical, but I think it might have potential.

[@JustCuzRobotics]

I think the practical limitations of building such a thing would far exceed any possible benefits. Making a thin lightweight pressure vessel that can contain a full or even partial vacuum, with motor wires exiting it, would be impossible using any tools I can access. I did originally start the design with the concept of a normal outrunner brushless motor with a hoop flywheel attached to it, but there were a number of issues. It adds a whole other layer of complexity, one more motor and one more ESC, and a way to communicate what speed it needs to be at. These motors have bearings and shafts that are extremely small, and it would probably just break from the shock of impact from my own hits let alone outside forces. In combat robotics the goal is to make things as robust as possible, usually that means the dumbest, simplest solution is best.

[@willkelly6626]

Will the dartbox pro motors use the same brushed motors? And if so, what motors did you use on division V4?

[@JustCuzRobotics]

Right now the plan is to use the same brushed motors yes. I ran Geckos on V4 in January but I think I'll upgrade to Vipers.

[@johnathanclayton2887]

There's the flywheel have any effect on how much connect energy you deliver? Or does it help you get back up to speed after a big hit? I know it's primary function is anti-gyro, I thought it might also be helpful for that.

[@most_displeased_customer1209]

Yeah an anti gyro system means the robot doesn't float around when turning and the weapon itself is turning at whatever desired speed the builder(s) want and provides a more efficient transfer of energy. Shatter from battlebots uses magnets to counteract the jumping caused by the firing of his hammer for the same reason. Energy lost by the robot being unstable caused by kick up of a hammer or flipper or buffering of spinners (mostly verts) is still energy lost after all. So yeah you're right it is all about how you transfer energy after all especially with high impact weapons like those listed above.

[@JustCuzRobotics]

It does not add significant energy to hits since the rubber disk will slip when the weapon stops instantly, but yes it should in theory also work to spin the blade up faster after a hit. Not very efficiently mind you but definitely to a noticeable degree.

[@most_displeased_customer1209]

@@JustCuzRobotics true it doesn't add significant energy to hits but it does mean you can use that initial energy more efficiently saving energy that would otherwise be lost. In a sense not unlike a regen braking system in modern electric or hybrid cars where the vehicle can collect some of the energy from friction in the brake system and use it to recharge the battery for example. Your gyro system does largely the same thing, using energy more efficiently, just in a different way right?

[@Drawliphant]

Why so many screws from the carbon fiber to the uprights? Im not an engineer but i would have used like 2. Does it help connect the two halves together?

[@JustCuzRobotics]

Probably don't need more than like 3 but carbon fiber tears relatively easily so it spreads the stress out to 5 points instead of 2 or 3

[@zachharris3779]

I love that you made the motor more efficient by making it smoother even tho your spinning a 6 inch blunt blade just made me laugh

[@JustCuzRobotics]

Well it's a product others will use too, not just me. Most people will probably use smaller diameter weapons with less drag.

[@williamhoover1515]

Seth- Can you add a super-caps to help boost spin up on the weapon? They are very light and can add support in vertical areas.

[@DigitalJedi]

I wouldn't suggest using electrical components for anything structural. The Supercaps may also not help spin-up much, as the current the battery is able to provide may already be more than the motor draws under load. Lipos can already dump loads of current and these motors are typically in the 70-100A peak range.

[@williamhoover1515]

@@DigitalJedi I meant the caps go into normal structural components for space/ weight concerns.

[@DigitalJedi]

@williamhoover1515 And then your frame distorts a little in a hit and one of your caps pulls a leg out of the PCB and your weapon is dead. Weight concerns are why you don't do this, not a reason to rely on capacitors to be a structural member of something that will bend and distort and deal with massive shock loads.

[@JustCuzRobotics]

I tried to do the math for this. Long story short the energy density per gram (specific energy density) I could get from my current lipo is 640J/g (13Wh/73g). A supercapacitor that is rated for 5.5V, 1F, is 3.7g, and let's say I use 4 charged to lipo voltage 4.35V each. That means each capacitor stores 9.46J which means it has a specific energy density of about 2.55J/g. So it's 250 times less energy per weight than a lipo. Better just use a bigger lipo!

[@williamhoover1515]

@@JustCuzRobotics Thanks, I'm glad for all the great comments-B

[@IsaacSchultz-lz8jc]

Im wondering if you are going to offer the hub motors in different kv maybe for drum spinners or smaller diameter weapons.

[@JustCuzRobotics]

I have plans to do that at some point in the future if demand is high enough, but if you want a higher RPM you can also run the motor at 5S or 6S. You will probably find even 1200kv is a good KV at higher voltage for smaller diameter weapons. With a 1200kv hubmotor, 3inch diameter weapons on 6S voltage will have a tip speed around 250mph theoretical. With 3.5inches, on 5S you are also around 250mph. On 4S, 4, 4.5, and 5 inch blades have 228, 257, 286mph respectively.

[@IsaacSchultz-lz8jc]

Or possibly use timing advance capable esc on 4s. Have you tried any timing advance capital esc’s before tho?

[@JustCuzRobotics]

I only use ESCs that will fit inside my robots. Usually this means drone ESCs. I'm not familiar with that type.

[@IsaacSchultz-lz8jc]

Timing advance is usually in rc car esc but it can be implemented via software if you can find out how to do it it essentially works by powering each phase early to get more torque and rpm but at the cost of amp draw and heat but being in a fight for only 3 minutes that might not be too much of a problem for the motor but the esc might get too warm if it doesn’t have enough heatsink but I think it might be beneficial to look into this because sometimes you can get close to double the rpm without sacrificing torque and keeping weight down with needing a larger battery.

[@IsaacSchultz-lz8jc]

Without needing a bigger battery*

[@aminechouchene6824]

i'm really imased by your videos and explaination , I'm doing a 40Kg battelbot and I'm having a small problem in my big vertical weapon ( actually I didn't do any calculation hehe ..) I want some guide in it and thank youu

[@JustCuzRobotics]

40kg is a very very large difference from this 1.36kg robot. I would recommend you do a lot more research! And make sure yoy are very careful about safety around a spinner that large.

[@aminechouchene6824]

@@JustCuzRoboticsyeah it's really scary espacially it's a weapon bar ( riptide's weapon) with a 600rpm speed , I didn't tested with more than 20% speed and I'm worried haha

[@JustCuzRobotics]

600rpm? That is not particularly fast. Do you mean 6000?

[@aminechouchene6824]

Actually its 600rpm , i have a motor with 300rpm and a torke of 80kg , i'm using two motors to drive the weapon because the weapon itself quite heavy and i'm thinking for a single big hit everytime , The brushless motor are really expensive for a student and also i'm still new in battelbots hehe

[@gimp079]

HELLO...will you be releasing this as a full kit to purchase ?

[@JustCuzRobotics]

No I don't have any plans to release division as a kit. I may at some point sell the CAD design files so that you could attempt to build a copy yourself if you have the skills necessary but I don't want to have to provide assembly instructions and customer support for something like this - it's a bit too dangerous and complicated.

[@gimp079]

Thanks for the quick response. I see you plans/kit have just come back in stock.......:) @@JustCuzRobotics

[@KenzieeeBBB]

Where do you get your weapon? Drive belts I’m talking about beetle weight weapon drive belts because I see that you have three and 4 mm belts on your website but I’m not sure if those are gonna be thick enough. I’m a first time builder.❤

[@JustCuzRobotics]

The ones I sell are just a single size for the SSP kit, I had to order like 100 at a time. For normal people, check Fingertech for S3M belts, and BBMan, PolyBelt, McMasterCarr for any other type really.

[@KenzieeeBBB]

Thank you so much you have one of the best channels the reason I wanted to do this is because of you and I didn’t even think you would respond but you’re just the best KZbinr and I’m using most of your parts and also I was wondering where we could get a charger for the 550 Lipo that you sell on your website

[@JustCuzRobotics]

Aww thank you so much! Honestly, amazon. I would suggest any decent reviewwd model that is a proper balance charger should work. Something like the B6AC or it's many clones. amzn.to/3UK5zpd Note you will also need to solder up an XT30 charging adapter yourself.

[@KenzieeeBBB]

Thank you very much. When are you going to do a build review on subtraction

[@KenzieeeBBB]

And I’m only 11

[@chazzon4769]

This looks like a lot of inspiration was taken from Monsoon

[@JustCuzRobotics]

That's exactly right!

[@cannan9615]

What tpu do you use in your bots?

[@JustCuzRobotics]

I mostly use Sainsmart TPU but I switch between brands based on availability and color sometimes

[@charlesballiet7074]

33:30 how can you just specify a 1200kv usually the trade off between # of windings and wire diameter for a given hub footprint is rather constraining especially if you want high torque/ fast spin up or more power at during low rpm

[@JustCuzRobotics]

Because these motors are custom wound they can make almost any kv within reason.

[@c.i.n.b4710]

it looks like a better version of Bruh Moment Simulator from BBB

[@Gunstick]

Getting debris inside the weapon area which will then damage the wires may be an issue.

[@JustCuzRobotics]

Not very likely, I had the entire weapon motor exposed on Division for a long time and it was only other weapons that were a danger, not debris.

[@Onisanofwhan]

How difficult would it be to fit a 500 or 600 kv motor into a hub like that?

[@JustCuzRobotics]

Do you mean how hard would it be for you to make a one off lower KV version of my hubmotor? Or to design your own hubmotor with a lower KV motor? There are very few off the shelf motors that low KV in this size, if any, so that would be a challenge for a one off. You would lose a lot of peak power at lower voltages.

[@Onisanofwhan]

@JustCuzRobotics well I have a very specific design I'm working on for a large over head bar beetle. I already have the motors and have tested them rigged up to the weapon and am in the process of designing/ fitting the hub for them. I've worked as a manual machinist for 10+ years and have little to no cad experience. I have my design on paper and am about to turn it on the lathe but looking at your I figure I could use some help. Robot vet 20+ years.

[@JustCuzRobotics]

For an overhead spinner I actually have a different custom motor I designed for that type of use case. See here: justcuzrobotics.com/products/jcr-4935-1000kv

[@Onisanofwhan]

@JustCuzRobotics ya I like that. My weapon in this case has a 12 in diameter so to keep the tip speed under 250 mph I need something in the 500 to 600 kv range. That's the reason for my initial question.

[@JustCuzRobotics]

You might need to belt drive the weapon for that large of a diameter, then you can use a larger kv and a belt reduction to get better spinup times

[@neilrhoades5951]

I would say anodize your titanium, but it's hard to get a great orange color i think.

[@JustCuzRobotics]

Yeah I tried it for last version's wedge but a vibrant orange isn't really possible, easier to do blue, purple or a faded yellow.

[@henriqueitaopalos9743]

How much will the Hubmotor cost?

[@JustCuzRobotics]

Exact pricing TBD but between $90-100

[@TheRattleSnake3145]

Will you sell weapons for this motor?

[@JustCuzRobotics]

I'll probably provide a few designs for free that others can use a service like send cut send to produce.

[@TheRattleSnake3145]

@@JustCuzRobotics the trouble for me is that sendcutsent don't send to Australia. PCB way do, but I don't think they cut that sort of metal.

[@JustCuzRobotics]

I can probably arrange a one-off order for you if need be. Once the hubmotors are in stock in a couple weeks, send a customer support message or email [e-mail] about it.

[@TheRattleSnake3145]

@@JustCuzRobotics thanks, I'll do that.

[@gsasagas]

Hey Seth. Division v4, looks insane. Um from Brazil, How can i get one hubmotor like this one.

[@JustCuzRobotics]

Thank you! Right now the hubmotors are in production, I don't have any more prototypes available. The motors will be for sale starting mid-late March most likely. I ship internationally, though it will be on you to figure out what shipping option is best and any related import fees. DHL or UPS usually work best for international orders.

[@monkeyboy1387]

2:57 I too like being able to go balls out all the time.

[@OverlordVRC]

Would a tpu shock mount for the flywheel be effective to decrease possible damage to the bearings?

[@JustCuzRobotics]

The flywheel needs to be rigigly held in place so the rubber wheel can spin it. So not really.

[@Coboxite]

I bet you could mess with some people by telling them that the section that houses the fly wheel is actually where the weapon motor is

[@JustCuzRobotics]

Oh some people already thought that when seeing the bot in person lol

[@charlesballiet7074]

why not just paint the white plastic parts black?

[@JustCuzRobotics]

UHMW is incredibly slippery and does not bond well to paint or glue it would flake off easily.

[@AJB2K3]

Using fire as a weapon, what a lazy stupid idea.