My teammate insist on building a 77w drive base and expect it to be super competitive and outpush every other robot (400rpm on 4’’ wheels). I’m concerned about whether this can actually create stable advantages on pushes that were worth that extra motor. What are your ideas on it?
firstly, 400rpm on 4’’ wheels is crazy fast. even if you are not going for a tank, this speed would be hard to control. if you are doing 400rpm, it should be on 3.25’’ wheels.
secondly, the power of the drivetrain is not what determines whether you can push another bot. power is just the product of speed and torque. so having more power gives you the advantage that you can have a similar speed at more torque.
also, torque is not the only thing that determines whether you can push another bot. if you want to actually make use of the torque, you need to have a heavy bot. if the bot is very light, you will not have a lot of traction to push.
if your bot is lightweight, you could use forks to get under other bots and increase your traction, while lifting their wheels from the ground.
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You (and your teammate) might want to start with what you consider “super competitive” by adequately defining your goals and thinking about what your robot will need to succeed. Is a competitive robot one that outpushes other robots? Are there other factors you might need to consider when building your robot?
It would help if you also considered what functionalities your robot might need and the motors you may need. Because you’ve used up 77w of motors for your base, this would leave 11w for all other functionalities (assuming you are doing VRC, which you probably are). That’s only two 5.5w motors or one 11w motor.
I personally think that experimenting with this sort of design could be very useful. If utilizing a 77w drive properly, your robot could be very good offensively, but this could come at the cost of other functionalities, such as shooting the triballs. It’s just a matter of what you and your team decide to be the best and most competitive at the very end.
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Welcome to the community! 400RPM on 4" wheels is extremely fast, so you won’t actually have as much pushing power as you might like. It’s also important to consider whether you need more than 11W of power for the rest of the robot. Most robots (Ace, Calamity, etc.) use a 66W drive because they need 22W for an intake and launcher. However, if you really, really want to do a 77W drive (I do not recommend), I would look at the 21417A explanation video. They used a PTO system to use a 44W drive when using their catapult and a 77W drive when they weren’t using it.
tl;dr Your drive is too fast and it’s not really worth using more than 6 motors anyway
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Respectfully, just a plain 77w drivetrain is not good. Either you sacrifice your match losing capabilities or you sacrifice an intake. An elevation is completely out of the question.
I’d say you need to implement a pto to other subsystems like the shooter or something to use 77w drive. That way you can transfer between being a powerful pushbot and a robot that can actually do something other than pushing.
Personally, I think putting on that extra motor won’t actually do much for the stability of the robot. Also, you are only left with 11w for the other mechanisms in your robot. I would suggest a 6 motor drivetrain, giving you 22w for everything else.
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To add on to what people here have said, 77W drivetrain is very GOOD but not very VIABLE unless if you use a PTO like Robokauz. 66W drivetrain is plenty for most good teams. Or you could be like one of my sister teams and choose 22W drivetrain because "weight savings are crucial"
Also, 400RPM on 4 inch wheels is quite fast. Unless if you are a 8 year veteran who has 6 championship titles under theirs belt, you are going to have trouble with 400RPM on 4 inch. (83 in/sec) Check out this link too. Catalogue of Drive Gearings
Also, drivetrain wattage is not the only way to get the advantage in a push fight. If that is your main priority, then you should consider wedges or tilted skirts. Also, more wheels = better traction so maybe look into a way to have 3 or 4 wheels on each side.
All in all, tell your teammate that unless if he wants to be like McQueen, he should slow it down or pick smaller wheels. Also tell him that he should look into skirts. And that 66W is plenty.
Yes, it is worth it but only in certain scenarios. Me personally I did a 77W drive with a double ratchet for my intake and catapult like some robots from last year. I only really think this is useful though if 1. it fits on your robot easily and it’s at the skill level of your builder. Second if you think that you have issues with pushing power or you want a very fast drive Ex. 400rpm on 4". If you do want to do a double ratchet though try to understand fully how that works and how it will affect your driving since your intake with that ratchet if it goes backwards your cata will shoot.
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