Need help with choosing Versa-planetary redaction stages


#1

We are an Isreali team with a very low budget. Shipping time from Vex (not even to mention the price for priority shipping) is very high so we decided we want to order as many items before the build season so we don’t need to worry about what part arrives when during the build season.

When we came to the decision we want to buy Versa-planetary gearboxes for our robots we encountered a problem.

**We have no clue what redaction stages to get
**

We can’t afford to buy a bunch of all types and we don’t want to risk parts not arriving in time if we order during the build season.

My question is:
What stages would you as a veteran user of Versa-planetary recommend getting?
What stages do you find yourselves using the most?
And do you have any other tips for other related parts we should get/parts to avoid getting?

Any help will be thankfully welcomed, we are really out of ideas…


#2

How much do you have to spend? The beauty of the Versaplanetary is that you can stack different stages together to get different reductions.

If you can buy 3 stages, I would get a 1:3, 1:4, and 1:10 so you can stack them together as needed.

If you can only buy 2, probably get a 1:10 and one other, so you can get higher reductions when needed. The Versaplanetary is most often used with 775 type motors, which have fairly high speed and low torque (compared to, say, a CIM), usually necessitating higher reductions. If for some reason you wanted higher speed, you could use a lower reduction stage on its own.


#3

Call me tomorrow(I am from Israel), I will help you.
(I sent my number in PM)


#4

When I use the 57 Sport, I like to stock 20:1 and 100:1 ratios (since that leads to about 1000 and 200 RPM respectively with a RedLine). So 4:1 and 5:1 are about the mark in my mind.


#5

We seem to use 4, 5 and 9:1 the most.

I’d pick either 4 or 5 and not both if you’re to minimize extra.


#6

Due to bad experiences with 10:1s falling apart on us, we primarily use between 3-5, and then 7s or 9s in the first stage. Very rarely do we use 10s again after destroying many in build season 2017 for our climber. But besides our climber this year, we didnt really have a good place to set a 10:1 even.


#7

My philosophy is to standardize on 3:1 and 9:1. This gives you confidence that you can order the least number of choices and achieve a gear ratio somewhere between max efficiency and max power for any application.

This gives you a logarithmic set (3:1, 9:1, 27:1, 81:1, 243:1). Since max efficiency is roughly around T_stall/6 and max power is T_stall/2 you can usually hit a viable ratio on the first try and refine it by looking at your current draw.

If you feel the need to refine further you can add 3*sqrt(3) = 5:1 (or 5x5=3x9) to add half steps between your ratios. This gives you 5:1, 15:1, 45:1, 135:1 as additional choices.

Assuming you have four articulation channels per robot. I would start with 4-3:1, 6-9:1 and 2-5:1 stages. Don’t forget your Mag Encoders and Talons and use 1/2" Hex for everything. Feel free to double those numbers for spares/2nd robot.

That’s already a lot of money, but I think it is a good minimal set.


#8

We actually found 10:1’s to be the most useful reduction, since we could use it by itself for something like an intake system, while pairing it with 4:1’s or 3:1’s for other reductions like flywheels. So I reccommend stocking up on 10:1’s and 4:1’s, since those seem to be the ones we use the most.

As for any other tips, running a BAG with a 10:1 reduction is one of the quickest and easiest solutions for an intake on the fly. We used that on our 2018 robot, and it worked fine throughout the year.

P.S. If you find yourself needing 10:1’s in the middle of the season, don’t hesitate to use a 9:1, it’ll give you similar results in most cases.


#9

The most common stages we use are 3, 5 and 7. I would stay away from the 9 and 10 stages in high load applications as we have experienced the sun gears breaking because of their small size, But for low load applications like intakes 10s are fine
.


#10

As an acoustician, I tend to think of speed in terms of octaves. When expressed in octaves, normally multiplying/dividing gear reductions become adding/subtracting. VP single stages then become:

  • 3:1 1.6 octaves
  • 4:1 2.0 octaves
  • 5:1 2.3 octaves
  • 7:1 2.8 octaves
  • 9:1 3.2 octaves
  • 10:1 3.3 octaves

So, the basic unit for reduction using VPs is about 0.4 octaves (32%) The values per stage are basically 4, 5, 6, 7, or 8. Note that 9:1 and 10:1 are only a quarter unit apart - getting both of these is not worthwhile under limited funding.

For best results on a large budget, I’d suggest 3:1, 4:1, 5:1, 7:1, and 9:1. This literally lets you pick any gear ratio between 3:1 and 315:1 to within about 30-40%.

For a really tight budget, I’d suggest 3:1 and 9:1; this gets you three ratios pretty far apart for two sets of gears.

For a moderately tight budget, I’d suggest 3:1, 5:1, and 9:1. This gets you ratios from 3:1 to 45:1 in steps of about 0.8 octaves (75%).

Shooting for four ratios, I’d suggest 4:1 over 7:1 as the fourth ratio, but the differences are minor and a case could be made either way.

In any case, if you stack reductions, I recommend putting the greatest reduction first (close to the motor), and lowest reduction last (towards the output shaft). This minimizes stress on that tiny sun gear.


#11

The reductions you use depend a lot on what kind of motors you plan on using on your VersaPlanetary and what your intended use case is for them.

So, for instance, if I wanted to use a BAG motor for an intake system, I’d probably go with something like a 5:1 reduction for most cases. If I wanted to use a 775Pro for a “shooter” mechanism, I’d probably be looking at something closer to a 3:1 reduction.

Personally, if I was in your position and I had to pick a few sets of gears without knowing how I was going to use them, I’d probably get the following (in order of priority):

9:1
3:1
5:1
7:1

Assuming you get a least two VersaPlanetary gearboxes (since most of the time you won’t use just one), you’ll probably want about 2 sets of ring gears for each gearbox as well. In general, most applications will only require a single reduction (if you choose your motor correctly) and in the rare case you might use a two-stage reduction (our climber in 2017 did this). You’ll basically never need 3-stages on a single gearbox (and Vex discourages this in most cases anyways).

If you’re considering getting more than 2 gearboxes, you might also consider adding a few VersaPlanetary Lite gearboxes to save money. While not as strong as regular VersaPlanetarys, they are quite a bit cheaper and hold up for most uses (we used two of them on our intakes this year with no issues). You might also want to think about getting a VersaPlanetary CIM Adapter, in case you need to put a planetary reduction on a CIM-style motor.

Don’t forget to buy some lubricant for your gearboxes as well (if you haven’t already bought some), in general you can get that locally. Vex recommends white lithium grease, but personally, I strongly recommend Lucas Oil Products Red “N” Tacky Grease if you can get it (not sure what kind of availability it would have in Israel or if there’s a local equivalent).


#12

Note that the VP lites can only be face mounted. Probably not a show stopper, but something to realize and plan for before buying them.


#13

Good point! Though to be honest, I’ve never had to side mount a VersaPlanetary in the entire time I’ve used them, so that’s probably why I never noticed the Lites didn’t have that option. :rolleyes: