Is there a benefit to one of these over another in terms of durability or robustness? In general, are the high reduction stages as durable as the lower ones?
Two 7:1 are way better than 10:1 and 5:1. The small pinion/sun gear on the 10:1 vp stages tends to break under a high stress/ torque load.
In general, the higher reduction stages are less robust than the lower reduction ones. So 2x 7:1 will be more robust than a 10:1 & 5:1.
If you do decide to go with the 10:1 & 5:1, make sure to put the 10:1 closer to the motor. That way it will see less torque and be less likely to fail.
Our team has been using 10:1 VP Stages for a while now, we have never had issues with them. But as others has stated the 7:1’s will be more robust. This year we are using a 40:1 for our lift, using the VP 10:1 and 4:1.
We simply have a rule; “No 10:1 VP’s on the robot.” We have been let down by the 10:1 too many times to count.
7:1 is now the highest we will use and we prefer to not go above 5: 1 if possible.
This seems like a valid question. Putting a 10:1 stage close to the motor and a 5:1 stage in the second stage gives you a bigger sun gear in the higher torque stage. We’ve experienced failures of 10:1 stages as well, in applications where we shouldn’t have been using them, so I understand the feelings toward those. As a first stage, though, they’re less of a risk.
If my math is right (using this as a resource, the difference in overall mechanical efficiency is negligible. The 10:1 stage should be less efficient than 7:1, but the 5:1 is more efficient, so it washes out.
Personally, I’d use whichever stages we had on hand. Otherwise I don’t think it matters that much. For us, I suppose we could save ourselves from ourselves by not having 10:1 stages around, because then we won’t be tempted to subsequently put a 100:1 planetary in a place where it’s likely to fail.
+1 We had issues back in 2017 and assemble nearly everything based around 3:1, 4:1 or 5:1. We have a couple 7:1 but they havent been used in awhile. We dont mind having an additional stage for 100:1 for example meaning that itll hold up an entire season.
As the reduction gets higher, the gear sets do get weaker. This is due to the sun gear getting smaller as the reduction increases and there being fewer planet gears sharing the load (3
/ 4 / 5 have 4 planets, 7 / 9 / 10 have 3 planets). That’s a significant increase on the amount of torque each tooth of the sun gear is seeing. This is why we recommend that the larger stages go closer to the motor.
Lots of people use 10:1 stages and are fine. Most of the gear tooth failures that I have seen on 10:1 have been installed away from the motor.
And, just to verify - you are planning to power this with a single 775pro, Redline, or BAG, not a CIM, miniCIM, or NEO, right? And you’re not using the CIM output shaft?
In what way would that make a difference?[
Those combinations exceed the load ratings.
The CIM, miniCIM, and NEO motors have significantly higher stall torques than the 775s/BAG motors, so that 10:1 stage (assuming it’s correctly installed as the first stage against the motor) would see much higher loads in a stall scenaro.
If you use the 10:1 in the first stage you shouldn’t have a problem but I don’t know if I would use a VP for an elevator at all. Having said that many people have and have had success.
I love VPs and have 4 on this years robot but our elevator uses a AM CIM Sport HD both for robustness and ease of Neo installation.
The simple load ratings for a 1/2" hex output shaft suggest that the only one that doesn’t work is CIM motor with two 7:1 stages. If they use 10:1 first stage and 5:1 second stage with 1/2" hex shaft, even a CIM motor fits the simple ratings. Then they’d want to be careful to keep the output load as close in on the output shaft as it can get.
As long as you use the 10:1 first (close to the motor) it is perfectly fine. I have never seen a 10:1 fail as the first reduction on the motor - even when a gearbox has too much reduction, either a later stage fails or the output shaft.
You do not need a hard and fast rule prohibiting 10:1s on a robot as long as they are used only as the first reduction and you keep the gearbox free of debris.
The 10:1 / 5:1 might even be marignally stronger as the second stage would have 4 planets instead of 3. But it shouldn’t matter.
That said, I would make this choice based on possible ratio adjustments you might make later on. You can step to 35:1 or 63:1 easily with 7:1s by switching one of them to a 5:1 or 9:1; if you start with a 10:1 you can jump to a 40:1 or a 70:1, but that 70:1 ratio is going to be a little closer to the limit for some motors.
I would do 10:1 close to the motor, then the 5:1. The 5:1 stage is stronger than the 7:1 stage, so it would be better closer to the output.
10:1s work as long as you are careful with them. Putting one on the first stage of a VP isn’t bad.
We have two 100:1 VPs on our robot (10:1 x2) with 775pros. Both have a 24:12 chain reduction afterwards. Should we be concerned about gear failure? The load ratings guide shows green, but based on what everyone is saying about 10:1s on the output I’m a bit concerned.
I would be a little bit scared. The chain reduction will help, but that’s still a little scary. Going down to a 7:1 on the second stage would be advisable.
Think about your question. You asked if it would be okay but you have not given us any input as to the TORQUE required or how they are used. The reason these fail is due large torques on small gears. If you are using these on intakes, then you are probably ok…but if it is a HIGH TORQUE situation, then you might look at other options.
It also can help to support the end of the output shaft of the VP and not just have it be cantilevered.