For our (team 3175) off-season swerve I was planning on using a 12:70 reduction off a CIM to drive the wheels. Vex offers both Aluminum and Steel gears on their website, and it seems to me that using as many steel gears as possible would make the design more reliable. Vex offers the 12t pinion gear in steel, but does not offer a 70t spur gear in steel. Is using a steel pinion gear with an aluminum spur gear going to cause problems? If it will Vex does offer the 12t pinion gear in aluminum.
It’s not an issue at all unless you expect to run it under extremely high loads. Most teams have gotten away with aluminum gears on the drivetrain, us included. The 70t gear will also likely last about as long as the 12t one, since the wear is spread out across 70 teeth instead of 12.
It shouldn’t cause any issues in an FRC application. Many teams, mine included, have used steel pinions that mated with aluminum gears. Remember that in your 12:70 reduction, each tooth on the pinion gear will be loaded and unloaded 5.83 times per revolution of the 70 tooth gear.
It’s not an issue at all in FRC, it only becomes an issue under the kind of loads you should avoid using aluminum gears for in the first place.
In general, steel pinions and aluminum cluster gears are a good way to compromise between strength and weight in small to medium reductions.
And proper lubrication and maintenance is still the most important thing to long gear life!
Steel pinion to aluminum gear will be a good setup. The aluminum gear will wear to the pinion to run as smooth as possible. We usually run our gearboxes in for 15-30min to get the initial wear-in to happen.
I try to avoid aluminum-aluminum gear stages. Aluminum can gall easily and identical materials in general will stick to each other more then different ones.
We ran 12T pinions on our NEOs with both pinions in the gearbox driving an 80T aluminum gear this year on our DT. We just replaced the aluminum 80T gears 2 weeks ago after the robot had played 92 official matches and a lot of drive practice over the last month.
For the most part I do steel-aluminum pretty much everywhere for gear stages; steel-steel for really high loads.
This past year we started the season with steel on steel for our first stage but after having poor teeth wear, we switched to a different (32 to 20) and then aluminum also. We had aluminum to aluminum on our second stage and that wore fine (24:70 I think) and then everything else was steel on aluminum with no issues. We stripped the teeth on our climbing racks but what do you expect with that much torque and stalling it out.