Mark IV Module Steering Gear Ratio

[Tom_Line]

What is the SDS Swerve Mark IV Steering gear ratio?

Docs say 12.8:1. But the gears that I count are 15 : 32 and belt pulleys 10:40, which results in a 8.53333.

I know I’m missing something obvious here.

[swurl]

You probably miscounted the belt pulley as it is 15 : 32 and 10 : 60, not 10:40

[thatnameistaken]

@Tom_Line

belt pulleys 10:40

I’m guessing you were fooled by this:

pic: New COTS Swerve Module

A few people have asked about the tooth profile on the base pulley part. The belt is HTD-5M profile. The tooth profile on the pulley only has a full tooth every 3rd tooth. I designed this profile to make the part faster to machine. I can use a 3/16" end mill to cut the tooth profile. This profile has no negatively effect the operation of the module. It is such a large pulley and has over 180° of wrap so it works perfectly fine. The modules 2910 ran all last season used this same profile as well. …

The large pulley is intentionally missing teeth to ease manufacturing. Due to the large size and wrap, it doesn’t cause an issue.

(This part is a MK1 pulley, but I believe the subsequent revisions have used the same tooth profile.)