# Gear Ratio on Rack and Pinion

Hey guys, I’m trying to make a rack and pinion and I want to make it go faster with gear ratios. How am I suppose to do that? Thanks

You could build a gearbox with the desired ratio and connect the output shaft to the pinion and bing bang boom you’ve got yourself a powered slide.

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Use a larger gear to interface with the rack, build a gear box, or you can also change the internal gearing of the motor you are using with cartridges (assuming you are using V5 motors) to a cartridge with a higher output rpm. Is there a specific target speed you are aiming for?

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@RunsWthScissors Yes, I’m using v5 motors; however, I don’t have the cartridge to for that but I could go ask to buy some. For the answer to your question, I really don’t have a target speed but I just want to deploy really fast because I’m doing this challenge at my school where we have to travel a certain distance and push 6 blocks (the Tower Takeover ones) in the shortest amount of time possible, so I want to use them as walls to push the blocks out. In addition, I’m not really familiar with a gear box could you elaborate more?
@NicolBolas Could you elaborate more about your design as well because I’ve only done this for a year, but I didn’t get very hands on with the material since I was mostly the programmer…
Thank you both for trying to help me.

In addition, I want to try and make it as easy and as compact as possible since we have set rule on size limits.

I would recommend starting off by using a 36 tooth gear, directly connected to the motor. You may be able to optimize it if you can figure out what kind of surface you are pushing on. If you can figure out what the friction coefficients are (both static and kinetic) you can calculate how much force you have to push with over a set distance (is there a distance requirement? And if so how far?) and then work backwards to optimize for speed using the power output characteristics of the motor (I’m assuming a green cartridge?)

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I’d recommend just using the largest possible gear and then possibly doing a custom slide passively from standoffs and HS bearings. Those will deploy very fast, and passively

I understand what you mean. However, I thought about it but I couldn’t figure out how to motorized this type of linear slides.

You don’t need to. The point is that it’s a compact and passive linear slide that can have variable punching power. If you put rubber bands between the two bearings, then the bands will naturally pull the two bearings together.

Alright, thanks for helping me. I’ll find out. Yes, we have a distance requirement which is just 1 meter from the blocks. In addition, we are using the green cartridge, but I might be able to buy the different color cartridges.

you can gear the drive up by putting a 60t on the motor shaft and add a 36t gear on the wheel. Something like this.

Since one rotation of the motor will make the wheel spin 1.6 rotations, your drive speed can be effectively faster without needing other motor cartridges. Using gears to speed up / slow down mechanisms is what we call gear ratio, and a unit with multiple gears used to change speed with gear ratio is called a gear box. I’ll also suggest using 3.25” wheels (shown in the photo) to ensure that there’s enough torque to push the 6 cubes.

As for rack speed, using larger gears will make it faster as there are more teeth per rotation, so more distance can be traveled compared to a smaller gear

Would you mind elaborating the challenge you guys are doing so we can better know the requirements?

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This has a good model of a linear slide system. It isn’t geared up, but you can use the same type of system to set it up.
https://kb.vex.com/hc/en-us/articles/360037388692-Building-V5-Robot-Lift-Systems
You can skip to the linear slide section, under the scissors lift one.

So the challenge is to go under a desk that has the measurement of 33" (length) by 16.5" (width) by 14.25"(height). Then we’ll have to go a meter and expand to push 6 Tower Takeover blocks another meter. The objective is to get the shortest time possible.

However we have to under a desk before we can expand to push the blocks; therefore, i can’t really do that because it will expand when the bot is turned on

Just so you know, this set up will cause the wheels on one side of the chassis to spin in opposite direction. You need an idler to have the wheels spin in the same direction.

I think that there’s supposed to be one.

Looks like there’s a shaft that goes between the gears, may be a space for a 12 tooth pinion.

Oh I see now, the gears driving each wheel are independent of the other wheels. In that case, I’d recommended a continuous gear train for either side of the chassis. That will allow the power of 2 motors to power one wheel in the event that one wheel gets stuck. There’s no real reason for independent power output outside of an x-drive or mecanum drive.

What surface are the blocks sliding on? I’m curious because if I could replicate it I could measure the coefficient of friction and do some of the calculations myself

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yup I actually replaced the standoff with a 12t pinion after figuring out that independent power output is unfavorable. The CAD was from around last April

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um I’m not really sure, but i can go ask tomorrow about the material the surface is made of.