I have recently become aware that the Versaplanetary 2:1 option has become extinct from both the Vex Pro and WCProducts web sites. Is there any reason for this? We use these more than any other single reduction, but I guess we will now have to switch out to other ratios. Did other teams use them? I am guessing it was mostly a demand thing.
I’ve actually never seen a 2:1 option available.
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It’s probably either lack of demand or the release of a new version soon. Let’s hope for the latter
I could be wrong but I’m pretty sure there never was a 2:1 ratio option, and I’ve been ordering versaplanetaries since they came out.
That said, I would certainly love to see both 2:1 and 6:1 options, there are several specific ratios they would be quite useful for. I get why they don’t have them though, for the majority of applications you can just go up or down a ratio and still have whatever you’re trying to build work basically the same way and it gets expensive to keep so many different SKU’s in-stock (and they already have trouble keeping what they already make in-stock).
How do you physically accomplish a 2:1 ratio in a planetary setup?
Ratio = (Ring teeth + Sun teeth)/(Sun teeth)
Ratio of 2 necessitates ring teeth = sun teeth, which is a coupling, not a gear reduction…
Vex nor WCP has ever sold a 2:1. Maybe your thinking of the 3:1?
VP gear ratios usually go out of stock between weeks 5 and 6 (The 4:1s are usually available however). I like the spread the Vex provides currently, as it lets me get gear ratios in a very wide spread and accuracy with just 2 stages.
6:1 is impossible because the ring gear is 72 teeth. The formula is:
Ring/Sun + 1 = R
For a 6:1, Ring/Sun would need to be 5, and 72 isn’t divisible by 5.
^^ Exactly this. If you made a 2:1 planetary with a fixed ring gear, it would be more of an asteroid belt gearbox than a planetary. :eek:
Curiously enough, it was half of the answer to a quiz I posted a while back.
Full marks. Not possible to get 2:1 in a planetary – you can approach that number but that the best you can do.
In practice the lowest I’ve seen in a planetary is 2.5:1 (48T ring, 8T Planets, 32T sun).
If you want to get all technical, you can get lower than a 2:1 ratio but it is not the ratio from the sun to the carrier but rather in the ratio from the sun to the ring or from the ring to the carrier. BUT neither of those cases apply to a VersaPlanetary which uses planetary gearsets in the sun to carrier configuration (holding the ring stationary).
Can I ask why do you want 2:1 in a Versa Planetary?
Dr. Joe J.
My apologies. Both me and our mentor remembered there being one, but I think I’m just losing it. I should have thought about how a 2:1 would even be possible, I just thought I remembered seeing one at one point. It’s been a long season. The reason we need one is because we had one cim powering our climber and are switching to a dual input versaplanetary with 2 775 pros and a cim output shaft, and we did not want to screw with the gearing of the existing gearbox because then we would have to order more gears. We originally would have designed like that, but we kinda ran out of PDP slots and did not want to risk smoking a 775 (although we used 8 on the drivetrain, so…)… It’s a pretty sketchy gearbox, we did not anticipate going with it on the final product, but it just worked. With a 3:1 we have a lot more margin I guess.