Drive speed transmission for Tipping Point

[TXTaylor299792]

Do you think speed transmission is worth it for tipping point drivetrain design？

• No speed transmission
• pneumatic two speed transmission
• planetary transmission
• Other

[Ryan_4253B]

Drive speed will definitely be important for teams to grab mobile goals during autonomous, but at the same time blindly increasing speed lowers acceleration, and further adding mass of the mobile goals may kill the chassis during the match. This is why theoretically a 2 speed shifter is perfect for match play since you can have the high speed for grabbing mobile goals (robot is still light = higher acceleration), and switch to a more controllable speed once the mobile goal has been taken.

By computing a chassis’ max velocity given rpm and wheel radius and max acceleration given wheel torque and mass, it seems like a chassis can go well over conventional speed for the most efficient mobile goal sprint possible (it was around 700 4”). Note that i did not consider rolling resistance or other forces when computing these, so take it with a grain of salt as it’ll most likely be very off.

[Connor]

@Ryan_4253B

This is why theoretically a 2 speed shifter is perfect for match play since you can have the high speed for grabbing mobile goals (robot is still light = higher acceleration), and switch to a more controllable speed once the mobile goal has been taken.

VEX Parts are clunki and transmissions are chonky. The loss in control and added moving parts is not worth the tradeoff. And added friction and plastic parts from the transmission results in torque loss, and at that rate might as well have no transmission in the first place. Looking at some competitions and reveals, your robot should have the torque to drag two mobile goals on the ground with relative ease with merely a gear ratio or direct 1:1 for the drive if built correctly.

I would rather stick with the most simplistic design unless someone proves me otherwise. But for the meantime, I have not seen a transmission that is capable unless it’s some sort of differential design.

[VexTeamZ]

@Connor

have not seen a transmission that is capable unless it’s some sort of differential design.

Fred VII Highlights, Green Egg Robotics (Team 44)

[Connor]

Team 44 is a really good team but they are a team with extremely high dedication. They even built their own mecanum wheels one time:

But, although team 44 had a transmision and used them in 2014, it is obvious the meta is NOT to have one with V5 in VRC. If transmissions were the meta then you should have expected one in VRC during Turning Point season at least making RR. But since there has not been, as what I am aware of, I believe this is due to the sheer power of the motors that can just destroy the gearing of transmissions with shock loads.

Unless you have the same dedication as team 44 to make a transmission that is seamless and works well with V5 long-term, I do not believe it is worth a transmission.

[Ryan_4253B]

@Connor

your robot should have the torque to drag two mobile goals on the ground with relative ease with merely a gear ratio or direct 1:1 for the drive if built correctly.

The issue isn’t with whether a direct drive have enough torque to tow 2 mogos on the field. Any random 4m 200 drive can achieve that, even if not built correctly. The problem comes in when teams start gearing up their drive for speed in order to reach the center faster. A robot may have enough torque to accelerate under no load, but not when an extra 8 pounds of weight is added. Obviously this won’t happen under common drive speeds like 360 6m (2145z), but as teams go for speeds that are 600+ to gain an edge, it is where a shifter can come in useful.

@Connor

I have not seen a transmission that is capable unless it’s some sort of differential design.

N O

VEX U BLRS Change Up 2021 Reveal Video

[Connor]

@Ryan_4253B

The issue isn’t with whether a direct drive have enough torque to tow 2 mogos on the field. Any random 4m 200 drive can achieve that, even if not built correctly. The problem comes in when teams start gearing up their drive for speed in order to reach the center faster. A robot may have enough torque to accelerate under no load, but not when an extra 8 pounds of weight is added. Obviously this won’t happen under common drive speeds like 360 6m (2145z), but as teams go for speeds that are 600+ to gain an edge, it is where a shifter can come in useful.

@Connor

I have not seen a transmission that is capable unless it’s some sort of differential design.

N O

Honestly, if you believe you can make it work in VRC go ahead and build it.

Maybe consider talking with BLRS for assistance possibly in building such a transmission

[Xenon27]

@Connor

If transmissions were the meta then you should have expected one in VRC during Turning Point season at least making RR

I think the explanation for this is that pneumatics weren’t worth the motor cost ever in any of the past games since v5.

But now that pneumatics has no motor penalty, I do think a pneumatic transmission is viable. It’d be difficult to pull off successfully, but I think it could be worth it.

Alternatively, you could have 4 motors powering your drive as normal, but use a transmission to divert power from 2 or even 4 of your other motors into your drive if you need a ton of torque all of a sudden. You’re not going to need to use your lift or intakes in a pushing match, so if you can divert the motor power from these subsystems into your drive, I think you can get away with having a much higher drive speed than would normally be viable.