Re: Conversion tool

Sorry for the delay with this. I've been struggling to keep up and only just 
saw this.

From: "Johannes Werner" <joe@???-?????.de>
To: <SPELLJAMMER-L@??????.???????.com>
Sent: Friday, October 19, 2007 11:20 AM
Subject: [SPELLJAMMER] Conversion tool, was: Herospace - non-spherical 
planets?


> Hi all,
>
> while reading the huge load of SJML-mails (still not read everything
> after my holiday...) I came across a comment about the standard form of
> plante descriptions. It stated that miles and Farenheit were the
> standard units to be used in SJ. Being raised on the metric system (that
> means not knowing what a quarterpounder with cheese is) I prefer
> Celsius, kilometers, litres and such over miles and gallons (which
> ones?)... so for me the standard system is sometimes awkward to use.

I know how you feel. It is very bad here in the UK, where they just forced 
us over to metric and lots of older people have little real understanding of 
what the units mean.

Personally, I'm a hybrid person preferring miles and Celsius. I've never 
liked using a temperature scale based on 100 degrees being the temperature 
of a cows bum!

I prefer SI Units to bushels and other weird imperial multiples, but for 
RPGs they work well in sci-fi games.

However, Spelljammer is a fantasy game and imperial measurements, 
non-decimal money and anything else that is a bit old all add to the 
flavour. While these things can be a bit hard to grasp, I think that using 
them (and any other historical things we can find) will add a sense of 
otherness, that makes a SJ game seem more real.

> Somebody suggested a conversion table to be put up on BTM. I made one,
> but it looked awful and lacked a certain geekiness. So I played around
> with circular sliderules and came up with this:
> <http://exp1.fkp.physik.tu-darmstadt.de/~werner/my_circular_sl.ps>

Try not to post embedded links or rich text links onto the list as they 
often don't work properly. Plain text works best for most people:
http://exp1.fkp.physik.tu-darmstadt.de/~werner/my_circular_sl.ps

> I started putting a second fixed scale on the inner ring that directly
> allowed the conversion miles <-> kilometers, but it was awkward to use.
> The "new" design is so far only a circular slide rule with a planet size
> table in the center. The conversion miles <-> km is marked with an arc,
> so the division / multiplication by 1.6 is easy to find (I'll probably
> include a red line there, so far only b/w since my laserprinter is only
> b/w). The accuracy is not that great, but it does not need to be (in my
> opinion), about 1% should be enough (and achievable), I'd round the
> result anyway....
> It can be printed on paper, cut out and glued on a cdrom and a clear CD-R
> shaped plastic piece, such as those that sometimes come with spindles of
> cdrs. Now I just need to find a nice axle to fit the 1.5cm hole in the
> center...

Try going to your local DIY superstore. They often have lengths of various 
diameter wooden doweling in stock. I would say, look for a dowel that gave a 
tight fit and then carve a thin shallow circle to allow the CD to rotate 
freely.

(I used to buy things like that, stick them in plastic water pipe tubes, 
cover them with "pipe lagging", carve "wood" patterns into the lagging with 
a soldering iron and then paint them with latex to make LRP staffs. In the 
LRP community, we built ourselves up a list of apparently random materials 
and supplies that all went together to form useful material for making 
props. Maybe there are things that can help a SJ DM who wants to use minis, 
without paying a small fortune.)

Alternatively you could use the spindle from a box of CDs! That *will* be 
the correct diameter!!!

> I will probably include a temperature conversion chart on the sliderule
> as can be found on the Jeppesen and Aristo manual flight computers
> (quite advanced and nice slide rules that are still being used). I'm not
> sure about the temperature range I should cover, the one on the
> commercial slide rules is probably not sufficient. On the other hand,
> anything outside that range (I guess -50°C to +50°C) qualifies as too
> cold / hot anyway (though my Canadian friends might disagree there).

Hmm. Don't forget to check out the magic spells that protect from heat and 
cold as they will extend the temperature range that a DM needs to think 
about. Crystal Spheres has an adventure where players need to fly close to a 
sun. Why not investigate the sort of temperature extreme that sort of thing 
involves.

> Which features would we need to put onto the slide rule? This is my
> first attempt at this and I am open to suggestions / new ideas.

Hmm, lets see what we have that needs mathematics. Here are some fairly 
simple calculations:

1) (Total*) Spellcasting Level vs Tactical Rating,
2) Planet Size vs Take Off Time vs Landing Time and
3) Lifejammer/Death Helm vs Lifespan.

* = Total Spellcasting Level being used for a multiclass Wizard/Cleric or 
similar character, so a Wiz 3/Clr 2 has a Spellcasting Level of 5 as far as 
Spelljamming is concerned. This is my take on things and not an official 
rule.

Here are some more complex calculations:

4) Air Envelope Size & Crew Size vs Remaining Air Supply,
5) Planet Position on Planetary Display Map (x2) vs Direct Distance and/or 
Travel Time (between them).

Air Supply is currently a bit of a pain. I've suggested converting over to 
"Man/Days" where every "Spacial Ton" provides 112 Man/Days of Fresh Air 
(that is 4 months/16 weeks for one man). A slide rule could be used both 
ways, so that when you add or subtract crew, or clean up or foul air, you 
could adjust the total air supply using mathematics. (This would be 
especially easy if we started having a Spelljamming Ship Character Sheet 
where we could keep a running total of air supply as well as other things 
like Hull Points.) And if two ships dock in wildspace, it would be lot 
easier to work out what happens to the air, because all we need to do is 
total up the Man/Days they both have and then divide that in proportion of 
the amount of Spacial Tons each ship has.

Planetary Position and Travel Time is probably more important than the exact 
Distance. If this was too difficult for a simple rotating slide rule, then 
perhaps you could cut the calculations down and just make one for a specific 
crystal sphere. That would limit the planetary orbits to a smaller number of 
possibilities.

> I'll try to cram as much on one side so that the assembly is still easy
> without the need to cut plastic. This gives some room to put some
> artwork on the back, I'll probably "steal" sth. from Steven's homepage if
> he allows it...

Artwork on the back? Why not use another clear CD cover and make another 
slide rule that goes on the back of your CD? That way you could use a dead 
CD for the middle and sandwich it with two clear CDs that both can be used 
for different things.

In fact, if you come up with a central spindle that can easily unscrew, you 
could make a series of front parts that can be swapped over to deal with 
calculations for different crystal spheres, different sized ships, different 
sized worlds or whatever. The rear disc could be static (or nightdruid - 
arf! arf!) and the front disc could swap to change the mathematical 
progression.

David "Big Mac" Shepheard
Virtual Eclipse Role Playing Club
http://uk.groups.yahoo.com/group/virtualeclipselrp/links/d20_system_001071937434/Spelljammer_001071430476
http://spelljammer.wikia.com/
http://www32.brinkster.com/virtualeclipse/