Hi! So my team is currently in the process of doing a rebuild and we’ve noticed that 6 motor drives are popular for people who have pneumatics, but the problem is that our team does not have pneumatics so we were wondering if a drivetrain on 4 blue motors would be a good idea.
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Are you using gears?
4 motors (or 4 11w and 2 5.5 if you have 5.5w motors) can be good with blue motors. I’d recommend either 360 on 3.25 (blue motors geared down 60:36) or333 on 3.25 (green motors geared up 36:60). If your new to robotics I wouldn’t worry about the extra 11w.
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Yes we are thinking about a gear ratio
Why can’t you gear up on a blue motor
You would have almost unusably low torque and it will be very easy for other robots to push you. Probably you wouldn’t even have enough torque to move. Blue motor drivetrains have very, very, low torque even without being geared up. I would highly not recommend this.
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you would have to gear it way down and it would be more optimal to gear greens slightly up
The short answer is “torque”
The long answer:
Blue motors by themselves have really high speed but low torque. This is because your aren’t changing the motor or more so the wattage but the gearbox. This gear box acts as a ratio, it makes it have a high speed and really low torque. This means that if you did gear a blue motor up it would have unusable torque. This would make it get pushed easy and have terrible acceleration, especially with 4 motors.
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this statement is just plain incorrect, sure something like 450-600 will have nowhere near the same amount of torque as 360, but that doesn’t mean they have low torque, as 360 is a .6667 gear reduction. without a doubt 360rpm is the layout if you’re forced into running a 44w drivetrain due to it having a lot of power, the acceleration is good and the top speed is very competitive.(talking on 3.25 wheels, lowest competitive speed you should run on 2.75s is 450, which would have better acceleration than 360 3.25)
Sorry for all the questions, I am wondering if a one to one is good then
Could you do it? Probably. Should you do it? Probably not. The torque on just straight blue motors on 4 inch wheels (I assume that’s what your using, maybe not though) is much less than most all teams. You would get pushed quite easily. You might also struggle with acceleration. I would highly recommend checking out this catalogue of drive gearings to see what ratios are good for which wheel size. Keep in mind that wheel size changes your effective torque (catalogue provides different gearings for each wheel). For example, a great gearing on 2.75 inch wheels is way too low torque on 4 inch wheels.
For a straight 1:1 blue motor drivetrain, you’re right that it could be viable with small wheels. My team has only 4 inch wheels at the moment, so sometimes I forget to think about the other wheel sizes. However, OP will definitely have to consider this as it seems like many teams will less resources opt for 4 inch wheels, maybe because they come in the clawbot kit. I should’ve clarified wheel size, my fault.
We started with just a drive and tried blue motors with 3.25 wheels and a 5:3 gear increase. Even with just the drive, brain and battery the motors would overheat . We switched to 200 rpm and had no problems for a while. When we built the rest of the robot and had to move the motors later on, we had to go to direct, 1:1, gearing. I then made the great suggestion to try blue cartridges again, and it was a disaster.
Even with 2.75 wheels you are going to find it difficult to use blue cartridges on a drive unless you add gears to get about a 3:1 reduction in speed, and if you do that, why not use green ones.
While in theory, you can get a higher top speed, you are not likely going to find it useful while navigating around a 12’ square field with 3 other robots and obstacles in your path during competitions.
Good Luck.
While in general I would argue strongly in favor of a 6 motor drive, if you don’t have pneumatics, then an 11W goal clamp leaves you with only 11W for an intake and wall stakes. Maybe possible with 1028A’s direct mech but that would be very challenging for most teams to build.
So, in this case 4 motor drive is okay. If you want to use blue motors, you will have to gear them down (direct 600 rpm is only viable on 2.75" wheels and with 66W or more on the drive). I recommend trying 360RPM (60:36 on blue cartridges) with 3.25" wheels or 257RPM (84:36 on blue cartridges) with 4" wheels. Anything faster than this won’t have enough torque.
There’s the Catalogue of Drive Gearings as pointed out above, but that mainly focuses on 6 motor drives, so you won’t be able to successfully use many of the gear ratios there.
If you don’t want to gear your drive, you can run 200RPM on 4" wheels (direct green cartridges), but that is extremely slow and I wouldn’t recommend it.
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for 4 inch wheels, I recommend speeds around the 300-400 range, 400 is around the same speed as 480 rpm on 3.25 wheels, making you a fast and competitive opponent
I use 4 blue motors with 36 to 60 gear ratio, output 360 RPM. I had no issues.
2 motors for intake, 1 motor for conveyor belt, and 1 motor for fish mech.
And our team doesn’t have 5.5 W motors.
Check out my matches on YouTube.
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That is WAY too fast… 170 in/sec… and I assume you used 4 motors… which needless to say… is a severe lack of torque
Even 1:1 blue motors to 3.25 wheels is still way faster, even most VEX teams won’t go above the 86 in/sec of a 1:1 600 rpm 2.75 drivetrain.
If you absolutely need a four motor drive, I agree 360rpm is probably the best one (put a 36 tooth on the motor shaft and a 60 on the wheel).
However… (my recommendations)
I would distribute your motors like this:
66w drivetrain
5.5w over-center clamp
5.5w lady brown (it does work)
11w intake
Blue motors are by far the best for drivetrains due to the amount of gearings they offer (and perhaps the rumored less friction).
Try to shoot for a drivetrain around 65-70 in/sec.
At the very least have a 55w drivetrain, but I highly encourage 66w for more power and build simplicity. Unless you’re in middle school (even then you should), your other mechanisms won’t matter as much if your robot can get bullied like a bowling ball.
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Absolutely correct, I’ve been running 5.5 LB for a bit and it works great. I was assuming they don’t have 5.5W motors, in which case the only way to do a 6m drive would be an 11W combined intake + wallstake mech and the only way I can think of is direct mech (which usually is 22W, I don’t know how well it would work with 11).
If you do have 5.5W motors, locking clamp and LB is definitely the way to go.
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With 4 motors that ratio would fry those motors, not to mention the acceleration. I would not run 480 on 3.25 or 360 on 4 with 44W