HPV Drivetrain Analyzer

Welcome to the HPV Drivetrain Analyzer. With this program, you can see what the metrics are for the drivetrain on your hpv (bike, trike, etc), if it uses chain coupled sprockets with an optional shaft coupled pair of sprocketsets between the crank and the road. Schlumpf Mountain-Drive, Speed-Drive, and High-Speed-Drive crank ratios are available modifiers in sprocketset #1. Three hub styles are accommodated, a single ratio or direct hub, a hub with up to 15 distinct ratios like the SRAM Spectro, and the Rohloff SpeedHub that has symmetrical ratios.

Math is done in floating point, which means that you can enter fractional numbers for the tooth count. This way you can, for instance, integrate the two Schlumpf ranges into one output display by entering the Schlumpf ratio times each of the chainrings on the crank. For an example of this technique, see the Schlumpf/Rohloff sample config.

There are five optional output tables:

1. A Cadence table showing speed data in miles/hour and kilometers/hour for a selectable range of crank rpm's,
2. a recap of the Input Data,
3. a table of Hub Ratios if the configuration has a ratio other than 1:1,
4. a Split Table showing tooth splits and percent change for shifts among sprockets in each sprocketset,
5. and a Gear Metrics table of gear permutations sorted by the output to input ratio. This table has several optional columns.

Preset Configurations

At the top of the input panel, there is a selector that will preset the inputs with known or typical configurations, which immediately display output when changed. One of the selections is 'My Configuration'. In this selection, you can save the values currently displayed by clicking the button labeled:

Below this selector is a six section table in which you can enter an optional title for the output and your sprocket and hub configuration.

Crank and Sprocketsets

In the 1st and 2nd Sprocketset sections, enter the tooth counts of the sprockets for the first or only chain. If your drivetrain is compound, enter the tooth counts of the sprockets for the second chain in the 3rd and 4th Sprocketset sections, otherwise leave them blank.

If a Schlumpf ratio is selected in the 1st sprocketset, entries 1 through 5 are copied to entries 6 to 10, multiplied by the Schlumpf ratio. This means that the chainrings on your Schlumpf drive must be entered in any of the boxes 1 to 5.

The sprocket tooth counts can be entered in any gearset array in any order or spacing. This makes it easy to make quick variations in configuration scenarios, and the +1 and -1 indicators under each tooth entry box can be clicked to increment/decrement that value for seeing the effects of changes on the output. The output is updated immediately (at least in Internet bandwidth terms). Clicking on an entry box will clear its contents.

Colorization Feature. The sprocketset that is selected for colorization will show each individual sprocket with all of it's combinations in a unique color, enabling you to see how ratios change as all of the ratios are selected without moving the chain off of that sprocket. Colorization is usually more meaningful for sprocketsets that are transmitting power by chain, as we more frequently shift the chain on the sprockets that receive power, such as the input cluster on the idler shaft and the cassette on the drive wheel.

Hub

In the Hub Values section, enter the ratios for your geared hub, otherwise select "direct 1:1" for an ungeared hub. The values in the entry cells for both hub styles can be changed if desired. Data for the presets comes from manufacturer's web sites, with much coming from Harris Cyclery. Sheldon Brown also has a good article on geared hubs

Driver Size

In the next area down, enter any of diameter or circumference in inches or millimeters, and select which measurement unit that you want listed in the output recap. The remaining 3 values are automagically displayed. Alternatively, you can select one of the preset options. The tire sizes and values for these options are courtesy of Harris Cyclery. Sheldon Brown gives some interesting insights in his tire sizing article.

Note: Driver size input must be accurate in order for the environmental data (speed, distance, development, etc) to be accurate. These data should be measured.

Crank length

If you select Gain Ratio for output, enter the length of your cranks, of at least 2 inches. If your rig has cranks shorter than 2 inches, I'd like to hear about your riding experience!

Display Controls

Towards the bottom, there are output options. If your screen is set for lower resolution than 1024x768, then you may find that sending output to separate windows may be helpful.
 
Output options are:

• the frame that you are reading now
• a new window each time (multiple output windows), or
• a single window that receives all output (default)

Browser Comments..

The browser that I use primarily is the most current Beta release of Google Chrome. When changes are made, they are immediately tested with it. Now and then, I will check other browsers' capability to display the output, but it is not unlikely that you may discover display and rendering anomalies before I do if you use something else. Browsers that are not reasonably current are almost guaranteed to be a problem. If this is the case, please don't hesitate to shoot off an informative e-mail with your complaint.

To do:

• Produce graphs to supplement tabular data.
• Optionally save 'My Configuration' in a cookie for a persistant configuration.

I hope you find the Analyzer useful.

DISCLAIMER:Use of this program is your own liability, as it's creators accept none.