New HW design - Omni Wheels and 30kW spinner

[Black-Tie Knife Fight]

Could it be worth looking at some of the dual hardness wheels. The idea is that the core is hard to keep things in place and the outer layer is softer for a "best of both" approach. That said, I'd imagine that there could be an issue of separation? I'm far from an expert on the matter.

[typhoon_driver]

Rather than threading in the steel, why not just have a blind hole through with a nylon nut on the other side? Less faffing around on the machining side.

[TechAUmNu]

Rather than threading in the steel, why not just have a blind hole through with a nylon nut on the other side? Less faffing around on the machining side.

Not sure how that is easier... tapping the mild steel should be a walk in the park compared to the hardox. I have proper spiral flute taps which you can use with a cordless drill.

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Update: Oh I see what you mean now. Yeah that would probably be easier.

[TechAUmNu]

Could it be worth looking at some of the dual hardness wheels. The idea is that the core is hard to keep things in place and the outer layer is softer for a "best of both" approach. That said, I'd imagine that there could be an issue of separation? I'm far from an expert on the matter.

Problem is that we are using 60 wheels, so it gets a bit expensive if you use anything but bargain basement wheels. The ones we have are these https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1
so £1.75 per wheel. We are went way over budget with the hardox which is why we switched to mild steel.

[typhoon_driver]

I agree that tapping the mild steel will be easier than the hardox but easier still would be to remove the tapped hole completely and just have a blank hole with a nut and bolt. Unless there's something else I'm missing?

[TechAUmNu]

I agree that tapping the mild steel will be easier than the hardox but easier still would be to remove the tapped hole completely and just have a blank hole with a nut and bolt. Unless there's something else I'm missing?

Oh I see what you mean now. Yeah that would probably be easier. lol

[overkill]

Or you can just tap the lower aluminium ring to avoid having an exposed nut.

Now that the ring is mild steel, why not machine the chamfer for the skateboard wheels directly in to the ring and do away with the aluminium rings? It saves time, money and complexity, plus setting up the milling job will be almost the same.

[TechAUmNu]

Or you can just tap the lower aluminium ring to avoid having an exposed nut.

Now that the ring is mild steel, why not machine the chamfer for the skateboard wheels directly in to the ring and do away with the aluminium rings? It saves time, money and complexity, plus setting up the milling job will be almost the same.

Although its not shown in the rendering, the aluminium rings are actually multiple pieces. Which means we can do it on our small cnc 300x300mm. So we can't fit the mild steel ring into it.

[TechAUmNu]

One thing I am a bit worried about is the removable links. Since we have a total of 30kW on weapons max current ~600A and 6kW max current ~180A on drive what would be best to use? They need to be fairly small since we are invertible.

[Eventorizon]

It is a problem TBH, but remember you will never be pulling 600A all the time.

In the HW we are trying to build we have a theoretical Maximum wattage of ~15'000W and up to 400A Continuous. However we have gone for 4 XT90's, 1 per motor. The andersons were way to big for us and we are familiar with XT90's so why change. They can take the burst current of each motor and are good for the cont. rating as well.

You might need 6 or even 8 but its one of the few low profile methods available.

Edit: This was something I started to look at, designing custom links for invertable robots that could handle massive currents. I have a few ideas but testing them and making them isn't something I am able to do at the moment.

[typhoon_driver]

Typhoon 2 used a 1000A military grade connector that retails around the £1000 mark (probably more with inflation and brexit in the decade and a bit since). But failing something like that, your other options should handle more than enough current. If you are drawing 600A in any continuous fashion then I would expect either your fuses to pop on the lipo or your wiring to melt.

[TechAUmNu]

Typhoon 2 used a 1000A military grade connector that retails around the £1000 mark (probably more with inflation and brexit in the decade and a bit since). But failing something like that, your other options should handle more than enough current. If you are drawing 600A in any continuous fashion then I would expect either your fuses to pop on the lipo or your wiring to melt.

Just a bit out of our price range then... Probably going to use a bunch of XT90 then, or make our own ones that can handle it.

We will be using 8awg for the connection between esc and the batteries.

The ratings on our batteries are rather silly. They are 5.4Ah 12S LiHV rated at 65-135C (350-730A). We have 2S2P for them so theoretically could sustain 700A continuous and 1460A burst at 52.2V. So the theoretical peak power is 76.2kW (102HP) lol.

Obviously those numbers are crazy and we will probably be closer to 300A for all motors.

[overkill]

I back Alex's P90 recommendation but make sure you rate them conservatively. I just had a motor burn-out where the motor was connected with an MT60 connector; the connector looks OK but the plastic melted internally and fused the connector together - really not what you want in a power link!

[TechAUmNu]

I back Alex's P90 recommendation but make sure you rate them conservatively. I just had a motor burn-out where the motor was connected with an MT60 connector; the connector looks OK but the plastic melted internally and fused the connector together - really not what you want in a power link!

I will probably use either 2 per motor or make my own connectors with 8mm bullets and a 3d printed/milled case.

[overkill]

Good idea - adding a printed back shell to the XT90 connectors make them muck easier to grip. I use a printed base for the connectors as well, it make mounting them so much easier.