Motorizing robot cart

Is it legal to motorize the robot cart to avoid the long distance traveling at worlds?

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Check out the event rules, section 6 on robot carts: https://www.firstinspires.org/sites/default/files/uploads/frc/EventRulesManual.pdf

When talking about a motorized cart, E601 is certainly a concern in the design and operation of the cart (it can be done, but you have to think through it!), and make sure the size is appropriate per E602.

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I am by no means a rules expert here but:

Teams have done something at least similar in the past (I can’t remember the team name but I recall years ago seeing one with an Egyptian theme having a whole chariot robot cart that the driver actually rode on with the robot) However any motorized carts I have seen have not at any point exceeded walking speed.

I think you would get some grief or at least added hassle of additional inspection/review. I would suggest you strongly consider if this is something you want to spend time dealing with at worlds (or anywhere else you use such a cart)

You likely would encounter less issue if the cart is “assist only” in other words, someone must actively be pushing/pulling the cart to activate the motor and it only assists proportional to the human effort input (truthfully pretty easy to do with a strain gauge integrated into the handle)

You will still have to walk the distance, you most certainly cannot bring in a platform large enough for your whole drive team plus robot to ride from the pits to the field.

You would have to have batteries/chargers dedicated to your cart.

Robot carts often have to negotiate cable covers, door jambs, concrete joints, and other bumps that a motor may help with, or may make more difficult/dangerous as it tries to force its way over instead of carefully lifting over or whatever you may need to do otherwise.

Again, I am no rules expert, but I remember considering building something like this in the past and determining while cool, it would not be worth the added hassle.

All that said, it could be a fun engineering challenge and if you do it please do post it so we can oohhh and aahhh.

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4564 Orange Chaos has a motorized cart that I believe is built on the base of a motorized wheel chair. Image stolen from their facebook page.

I would advise against it, at least as far as powered drive wheels. There are a number of teams (2767 included) that have motorized lifts on their carts to raise/lower the robot for any maintenance. Useful on occasion. That may be a better use of your time and invite less scrutiny.

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Team 696 has a scissor lift motorized cart that I think is really cool. The only downside to the cart was you couldn’t push it unless you used the motors.

To quote the changes to the event rules for 2024,

First, motorized carts (i.e. carts with powered propulsion) will not be allowed to be used at events. These carts create safety hazards as the driving could become uncontrolled in potentially crowded areas. This rule is not meant to disallow carts with motorized lifts.

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That is team 5006

I wonder if the opposite is true — eg will FIRST disallow adding motors to carts for the purpose of back driving them for charging laptop batteries and LEDs, etc?

By the letter of the rule, it seems like that would be allowed. Backdriving the motors isn’t “powered propulsion”.

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Why would you want the cart to be more difficult to move? The energy obtained isn’t free.

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You can always use a battery. More efficiant than converting from electrical to mechanical back to electrical energy.

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You don’t always have an open outlet at events, especially near the field, if your cart could have a hand crank generator or a way to get a little power back on each trip to and from the field it’s better than nothing. I agree it’s not free energy, but it’s something gained from having to push the cart anyways.

I don’t think it would ever be enough to charge a laptop, but I bet if you were efficient about LED placement and maximum brightness you could charge enough energy for that just from pushing power.

I agree a 12v battery is better with an DC/AC invertor for charging a laptop, this still means you have to top off your extra batteries for this purpose as well.

Our cart already has a battery with AC inverter that shows charge capacity percentage and a solar input charge controller.
It lasts about 2 days worth of cart and laptop charging, without recharging the battery itself.

I think I know my students pretty well, and they would make it a challenge to see who can recharge the battery and getting it back to 100% just by pushing the cart around.

It’s not about making the cart more difficult to push, while technically true, it’s about the motivation to “see how much extra charge I can get” to do the mechanical work.

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This LED or laptop charging usecase is nuts considering I have a strip of LEDs that runs off of 4 AA batteries for a long time. Sure not as bright as what a lot of folks might want, but more than enough for a comps worth of trips to the field.

Just use an old 12V battery like we all basically seem to agree is the practical option. It will last more than a comp and you can use the cheapest inverter on the market and cover 99% of your usecases.

As for the “student motivation/challenge” element… Idk. It’s fun an all and we all need some outlet that isn’t pure robot competition. If that’s what keeps these students motivated then go for it I guess.

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Several years ago, 503 had a stationary bike near their pit at MISJO (where there’s plenty o pit space) that students and some mentors/ parents used to charge batteries. It was for fun, not to address a practical problem.

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i mean… some events have some serious power limitations in the pits, I have been at some off season events where the power available is at best suitable for charging about 3 batteries once the extension cord length reaches across the gym; that extension cord is for 2-3 teams.

I don’t know the full story of the battery bank 2767 has kicking around to power the yellow monster, perhaps @Mark_Wasserman can elaborate on the power limitations at some past events that resulted in something like 100lbs of marine deep cycle batteries sitting in a box with wheels for extra juice.

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I haven’t yet read this thread but then @Skyehawk said "Beetlejuice, Beetlejuice, Beetlejuice!

Generating power by pushing the cart reminds me of this with the same outcome:

(1298) Bart’s Bike Light - YouTube

Then I thought would a cart be considered powered if it was human-electric powered like a diesel-electric locomotive? Human cranks a generator which powers the motors in the wheels.

As far as our pit power, our pit has the option to run on a 2000W inverter with a giant battery pack. The reason it came into being was, at the time, power on the floor at MI State eliminations was limited so we wanted backup/extra power (I believe this is no longer an issue at MI States).

It turns out that if you power the pit through the inverter, through the battery, through a battery charger, to the wall outlet, the current draw from the wall hovers around 4ish amps even if you run a soldering iron, hot glue gun, power tool, or even the dreaded hot air gun. This means that if you have multiple pits running on a 15Amp breaker, at least our pit wouldn’t bring on a peak current draw that might blow a breaker.

I know, multiple energy conversions makes some of us urrp up a little in our throats but it kinda works, sooo… there ya go.

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What, Mark, you mean to say I can’t recharge my car’s battery by holding a pinwheel out of the window?

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Hold two pinwheels out the window, easy!