I wrote up a SS/FG gear calculator called Rabbit. Attached are screen shots...

I'm new to the SS/FG thing so I put this together to help me understand what gearing I wanted...

Check it out: https://software.bareknucklebrigade.com/

Current Features:
- Gear Ratio
- Gain Ratio
- Gear Inches
- Development (meters)
- Skid Patches (option for ambidextrous skidding)
- Equivalent Gearing (by chainring or sprocket)
- Speed @ RPM
- Can launch as Java Applet (in browser) or with Java Web Start (allows off-line use on your machine)

New feature 03/24/2007:
- added skid patch analysis tool to help clear up confusion regarding the correct skid patch count calculation. This tool shows that Fraction's theorem is correct (https://www.bikeforums.net/singlespeed-fixed-gear/242123-skid-patch-theorem.html)

Hint-of-the-day: Use the mouse-wheel for quick changes in editable fields.

If you want features added let me know...

tt

i wonder, if you have a 27'' front wheel and a 700 x 23 rear, would that affect the gear ratio? or is it just the rear that matters?

oh and i like the calc, btw, impressive that you did this

the wheel driven by the chain is all that matters...

thanks... not exactly a novel idea but being hands-on i need to do something while i wait from my bfssfg iro....

I can't make it work in OSX Java. Looks good though, nice and simple.

dang, what version of OS X? email or PM me the error text or a screen dump and I can take a look at it. I have an OS X machine at work I test with tomorrow...

thanks...

It worked for me. Maybe you need to update your Java VM or something. Also, I'm using Firefox which opens the file in an external Java viewer. If you're using Safari, it might be trying (and failing) to open it itself.

Edit: I'm on 10.4.8 on an Intel. And this is a pretty cool program. I like the layout and all of the information presented.

There's no error message, it just crashes. It's 10.3.9 if that helps at all.

Edit Poop, it doesn't work with Firefox either. In either case Java Web Start just freezes.

Another suggestion, the rpms/ speed chart ought to go up to 150 or 160 for those of us rolling small gears down big hills.

I don't have a 10.3.x machine to look at this with...

As an alternative you can download and save the jar file from https://rabbit.bareknucklebrigade.com/dist/rabbit.jar .

Save it somewhere then either click on it to run it or type 'java -jar <directory you saved it in>/rabbit.jar' from a command line if you're that kinda person...

just pushed that change out...

Nicely done, bookmarked

Added support for ambidextrous skid patch calculation per Sheldon Brown's site.

Shouldn't my GI change with crank length?

edit: Also, I thought the calc was (chainring)*(wheel size)/(cog)

I run 40x13 with 23's... It should be 70, but your calc shows me 80.

No, thats why Sheldon favours the gain ratio measure instead.

Nice program.

You're on a bigger gear than you think.

No, not according to Sheldon's calc and my intuition.

Hmm... Whats so difficult about CR teeth/cog teeth*27=gear inches? Calculating gear inches ain't rocket surgery.

Oh wow lol. How do you calculate it correctly then?

Dude (or dudette) 40 divided by 13 times 27 is 83.07 gear inches. Now, you are probably running a 700c wheel which is not exactly 27", but use 27, its close enough for the girls we go with.

From the data I have 700c x 23 has a cirucmference of 2085 mm

for 40x13 and 700c x 23 the gear inch is calculated as:

gear inches = ( chainring ) / ( cog) * (wheel diameter in inches)
gear inches = ( chainring ) / ( cog) * (wheel circumference in inches) / ( pi )
gear inches = 40.0 / 13.0 * ( 2085 mm * 1 in / 25.4mm ) / 3.14159... [hey, it's pi day!]
gear inches = 80.40...

An issue in the software could be the wheel circumference lookup table. circumference isn't truely fixed across all scenarios and changes with tire brand, psi and rider weight. differences should be minor... i.e. if you're a bigger guy running low psi your gear inches could be a *little* lower than you think but we're spliting hairs...

I weep.

https://sheldonbrown.com/gears/

It just plan works!

See, you can sit here and be internet tough guys... or you can actually provide useful information. Thank you, testtube!

I've updated the jnlp file to give the user the *option* to install desktop and start menu shortcuts.

Let me know if anything else can/should be added... FYI - all the editable fields can be scrolled with the mouse wheel (if you have one...)

Launch Rabbit...

I'm declaring a moratorium on people saying "I weep" when nothing merits weeping .

**** man, I can't get this to work in java and I'm too lazy to figure out why---sorry. Other Java apps work fine for me.