Book 8: Robots design query

[Carlobrand]

Locomotion:

Like most of the design system, locomotion is unit-based. Transmission and suspension, but transmission's a bit puzzling: "One unit of transmission is required for each kilowatt of power plant output," for legs, wheels and tracks. Actual power consumption for wheels from the table is 0.3 Kw per unit for wheels, 0.4 for tracks, and 0.5 for legs.

So, if you have a 100 Kw power plant, 100 units, ergo your wheels draw 30 Kw, your tracks would draw 40, your legs would draw 50 (apparently irrespective of number of legs, else you're drawing more power than you can produce), a Kw would power your brain, your arms would take a bit, your devices would take some and ... what happens to the rest? Doesn't seem like a lot of flexibility here: you either load up on power-consuming equipment to use up the remaining power or you let that power go unused. I can't be understanding that right.

And your speed would be ... based on your arms, 'cause it's drawn from dex, which most of it comes from arms and tentacles? What the heck?

Then Errata comes in to make things a bit less clear: "Note the power requirements: each leg, 40kW; track, 30kW, wheels, 20kW. Each unit is per kW of power plant output." What? Wheels take 0.5 Kw per unit, or 20 Kw no matter how many or what size the bot is? 40 Kw per leg, regardless of the machine's actual size?

 

[Shonner]

We need a robot designer to write us some robot design rules.

 

[HG_B]

Locomotion:

Like most of the design system, locomotion is unit-based. ...

It is so illogical I decided to not use the book when I purchased it so many years ago. You'd be better of writing the rules from scratch.

 

[Carlobrand]

It is so illogical I decided to not use the book when I purchased it so many years ago. You'd be better of writing the rules from scratch.

Well, it'd be pretty easy to nab Striker locomotion rules. The grav and ACV bit, when you run the numbers, ends up being pretty much a direct lift from Striker. Speed being based on dex is absurd anyway.

I was hoping to work up some designer that would conform to the rules, but those rules don't make any sense.

 

[tjoneslo]

So, if you have a 100 Kw power plant, 100 units, ergo your wheels draw 30 Kw, your tracks would draw 40, your legs would draw 50 (apparently irrespective of number of legs, else you're drawing more power than you can produce), a Kw would power your brain, your arms would take a bit, your devices would take some and ... what happens to the rest? Doesn't seem like a lot of flexibility here: you either load up on power-consuming equipment to use up the remaining power or you let that power go unused. I can't be understanding that right.

This is correct iff you assume the connection between power plant, transmission, and locomotion system works like they do on an automobile. So the unused power goes to waste. Which makes no sense if your power plant is a fuel cell, a fusion plant, or the like.

The rule comes directly from striker (Book 3, sequence 1, section I), but poorly interpreted. The striker rule makes more sense. For your power plant, you must have a transmission of size x, of which you can direct all power through, for calculation of motive power and speed. The transmission doesn't take any power (or it takes all of it depending upon your viewpoint).

 

[Carlobrand]

This is correct iff you assume the connection between power plant, transmission, and locomotion system works like they do on an automobile. So the unused power goes to waste. Which makes no sense if your power plant is a fuel cell, a fusion plant, or the like.

The rule comes directly from striker (Book 3, sequence 1, section I), but poorly interpreted. The striker rule makes more sense. For your power plant, you must have a transmission of size x, of which you can direct all power through, for calculation of motive power and speed. The transmission doesn't take any power (or it takes all of it depending upon your viewpoint).

Unfortunately, bots are limited to fuel cells, fusion plants and batteries. I guess they don't want a bot emitting carbon monoxide exhaust into the passenger lounge or something.

It's that transmission taking X power that isn't making sense. If I ignore that (and the bizarre dex=speed bit) and - as you say - run with it a la Striker, it makes more sense.

 

[atpollard]

Sounds like errata.

 

[Carlobrand]

Sounds like errata.

Most likely, but I want to be sure I'm nut just misunderstanding it before I take it there.

 

[tancred]

No offense to DonM, but that has to be the least-useful errata I've seen.

I'm writing myself a .NET robot designer (because it takes me too long to write them up by hand) and I had to just skip that part to make any sense of it at all.

I haven't looked at Striker in years, and don't remember the locomotion rules from it.
But the design sequence for the locomotion in Book 8 has to be the most confusing thing I've ever seen, and the errata just made it more so.

So are we concluding to just skip the requirement in the errata and go with Carlobrand's calculation in the OP?

 

[Carlobrand]

...So are we concluding to just skip the requirement in the errata and go with Carlobrand's calculation in the OP?

??

My calculation was based on the Book 8 rules, which we all agree makes no sense.

Here's what I have so far:

Under the design rules, power and even your robot's mass are irrelevant. Speed is based on dex: if the bot's dex is 1-4, speed is 1 Book-1 combat band per round, or 25 meters per 15-seconds, about 6 KPH. Dex 5-9, speed is 2 bands per round, or 12 KPH. Dex 10-14 is 3 (18 KPH). Dex 15 is 4 (24 KPH). Robot dex cannot exceed 15.

Now the kicker:

Any grav bot automatically has a Dex of 15 (page 39) - presumably so long as it has thrust in excess of the 1G needed to neutralize gravity (though it doesn't actually say that). There's a maneuver G calculation on page 25, but it's not used elsewbere except to make sure the bot has more than 1G. So, all grav bots have a speed of 24 KPH.

Any Air-Cushion bot automatically has a Dex of 10. So, all ground-effects bots have a speed of 18 KPH.

For tracked and wheeled bots, dex is 3 (for tracks) or 2 (for wheels), plus the bonus from the logic program, plus the bonuses for the arms. Base for legs is dex minus 8, anything from 0 to 7 (or more if above Imperial tech levels). So, 6 KPH plus more if you toss on the right arms - you can usually get it up to 24 KPH.

The Striker speed was dictated by power level and weight, plus a few modifiers depending on whether you're using tracks, wheels or legs, whether you're a "light vehicle", and so forth. You divide power (Mw) by weight (tons), multiply result by 1000, look up result on a power-to-weight table and then factor in the modifiers. (The modifiers kick butt: tech level can turn great-grandpa's 25 KPH Benz Patent-Motorwagen into a TL15 125 KPH freeway runner.) Striker rules start at a base power-to-weight of 4-5 (comes out to 4-5 megawatts per thousand tons, the way they calculate). That gets you 15 KPH plus modifiers: another 10 if it's wheeled, another 15 for light (most robots), and 10 per tech level over 5. Net result, viewed over in Bot-land, is that 4-5 kilowatts can drive a ton of mass at anything from 15 to 140 KPH, depending on whether and how you embrace the modifiers. And, since the smallest bot power source is a 10 Kw fuel cell, and bots can get lots smaller than a ton, they can generally hit freeway speeds (or airplane speeds for the grav bots) - many times what Book-8 offers.

There's some logic to that madness: there's not much need for a steward bot that can achieve 120 KPH in the passenger lounge. Bots tend to fill human roles (usually tedious or laborious human roles, but human roles), and most human roles don't call for superhuman speed. There are a few - taxi driver, for example - but for the most part, if we want speed, we build something for speed and then get in it. Makes more sense to build a bot and then plug it into a taxi than to build a bot-taxi: if one breaks down, you reuse the other and preserve some of the investment. So, slow bots aren't actually a problem.

On the other hand, 13 horsepower behind something the weight of a manned go-kart, with a transmission about the size of a go-kart transmission, will deliver - no surprise - go-kart speeds, a lot more than the 24 KPH top speed that Book-8 offers. The problem comes in when we take what appear to be Striker transmission rules and then try to build a 24 KPH bot around that. The smallest Book-8 wheel transmission unit is a 0.3 liter, 0.5 kg structure, costs Cr15: "[o]ne unit of transmission is required for each kilowatt of power plant output." (So, technically, the smallest possible transmission is 3 liters, since the smallest power source is 10 kilowatts.) Coincidentally, a Striker TL7+ wheeled transmission comes in at 0.3 liters, 0.5 kg, and Cr15 per kilowatt. Same for the tracked transmission: Book-8 and Striker line up. (Same for TL8 legs if you draw on the MegaTrav data.) So, we're dealing with Striker sizing, weight, and costs, and - even without the modifiers - we're getting only a fraction of their potential out of them.

Point is this: you don't need a lot of power to move a bot, not if you're limiting your top speed to human norms. Since Book-8 runs everything by units, it might be better to toss the transmission calculations entirely in favor of an electric motor and drive train that takes X kilowatts of power, is size A, weight B and so forth, and delivers Z speed to a 100 kg or smaller mass - and if you want Z speed in a mass of 101 to 200 kg, you need two of those. I'm thinking around 3 kilowatts per 100 kg to achieve a solid 24 KPH performance across reasonable inclines as well as flats, but I'm not up on the size of a 3 Kw/4 HP motor.

 

[HG_B]

Unfortunately, bots are limited to fuel cells, fusion plants and batteries. I guess they don't want a bot emitting carbon monoxide exhaust into the passenger lounge or something.

At the TL's we're talking about they would use wireless power for those bots that basically remain within a ship. A small battery/capacitor for short term backup. So, for ship borne 'bots, eliminate the power plant.

 

[McPerth]

So, for ship borne 'bots, eliminate the power plant.

Fully agreed here- Battery for one hour is more than enough for them, as they can connect themselves to the power plant to recharge them if they need to disconnect themselves at any moment.

 

[aramis]

I'd go with 4 hours of battery (long enough to repair a downed plant) for engineering and repair bots.

 

[Carlobrand]

Have you compared prices? Fuel cells are pretty cheap for what they give.

 

[HG_B]

I'd go with 4 hours of battery (long enough to repair a downed plant) for engineering and repair bots.

Sure. That would suit their role. Rather than the cleaning bots where it isn't that critical.

 

[tancred]

Carlobrand, I wasn't even thinking about speed, although your explanation of why the rules don't make sense clears that up for me.

My only question was about the calculation for power, weight, and size, ignoring the comment from the errata.

All the subsequent discussion about speed and DEX shows where the rules really fall apart.

 

[HG_B]

Have you compared prices? Fuel cells are pretty cheap for what they give.

Why would you bother for bots that are bound to the ship? Kinda "messy".

 

[Carlobrand]

Why would you bother for bots that are bound to the ship? Kinda "messy".

'cause it's cheap. For Cr600, the Book-8 Type A fuel cell (presumably TL8 or lower) occupies 20 liters space and delivers 10 kW for however long the hydrogen lasts; a liter of hydrogen will last you 10 hours. Batteries become available at TL 12 (for absolutely no good reason - they duplicate the Striker batteries, and Striker has some decent ones as low as TL7-9); a TL12 1 kWH 1-liter battery costs Cr850 and gives you 6 minutes at 10 kW; higher tech batteries offer more power but at significant increase in price.

Even with an external power source available, the only time the battery makes sense costwise is when you are seriously, seriously cramped for space - some little "breadbox" bot, for example. Even given the relatively high price of bots, a manufacturer isn't going to build a model with a power source that costs more and delivers less unless some third factor becomes more important.

 

[pennshome723]

As for power, I always used 'broadcast power nodes' for the bots that are controlled by the ships AI and they have battery back up incase the power grid goes down.

 

[Carlobrand]

As for power, I always used 'broadcast power nodes' for the bots that are controlled by the ships AI and they have battery back up incase the power grid goes down.

My point was that the battery backup costs more than fuel cells. If I recall, it's one of those peculiarities of the game: I think they produce about 50 times more power for a given volume of hydrogen that they could if they obeyed the laws of physics. Not sure if that means they should be generating less power or consuming more hydrogen for their size, but that's the way the game made them, (probably so they'd be useful for this kind of thing) so for the purposes of Book-8 robot design, is cheaper to pop a fuel cell and a bit of fuel into any bot bigger than your kitchen trash can.