Category: Motors

How to determine your centre to centre distance when working with motors

Centre to centre
Centre to centre distance

When you add a motor you need to transfer the motion. There are a number of ways to do this. Some basic tips will help you understand the process here.

Gears

The gears we use are 20 dp. To determine the centre use the Gear calculator that West Coast Products provides. You will need to count the number of teeth on each gear.

Gears
Click to use the Gear Calculator

The Center Distance is the distance you want to mount your gears at. Keep in mind – how will you mount your motor so that it doesn’t interfere with your wheel!

Chain and Sprocket

Chain and sprocket
http://www.revrobotics.com/content/docs/Sprocket-Guide.pdf

Rev Robotics has a great Chain and Sprocket guide. To make it easier to calculate the centre to centre distance to mount the sprockets I’ve created a program you can use. https://dotnetfiddle.net/rK2yF9 you need to enter the number of teeth for each sprocket and the chain pitch (use 35 as we will be using #35 in class. You will get a number of results. Pick one that will allow you to mount the sprockets so they don’t overlap. You will probably need to break the chain and connect the correct amount of links. Vex Robotics has a great guide on how to do that.

Chain calculator
https://dotnetfiddle.net/rK2yF9

Belt and Pulley

West Coast Products has a great belt and pulley calculator. Make sure you know the number of teeth on each pulley and your desired distance. It will then give you two options – one for a distance smaller than your choice, and one that is bigger.

How to belts

Roboting: A guide for total noobs – really impressed with the quality and presentation of this. Must read for new team members

roboting

Lots of great information in this resource.  New (and experienced) members of our robotics team need to read it.

Compression rates for ball shooters and pickup mechanisms

 

durometerI’ve been trying to find information that will help when designing shooters and loaders.  Basically if you have two objects and you know the width of both objects how do you determine the distance between the objects for optimal loading or shooting?  Case in point – my class designed some tennis ball shooters and we experimented with different distances because the tennis balls compress.  Thankfully our team has built up a collection of different types of wheels so we are able to experiment.  The question is can we mathematically determine an optimal distance so that we reduce the number of tests we run. I found this pdf file: http://www.diversifiedsilicone.net/pdf/compression-force-graphs2.pdf. It contains some graphs that show the % compression produced based on the force applied.  Next semester we will be trying to make a shooter for the First Steamworks wiffle balls.  We know the material that the balls are made of and we have the durometer rates of our various wheels.  I’m interested to see if we can design a fairly good shooter using this information.

Encoders

amt103-v_smlEncoders are sensors used  to track the rotations of a wheel.  In the 2017 season we used two AMT103-V sensors for our drive train.  This allowed us to score gears effectively in autonomous mode as we could determine the number of rotations of the wheels to a great deal of precision.  Mounting these encoders was a pain.

We wired the motors with 102-1504-ND connectors.  These connectors came loose a few times as they were mounted down and if we ran over a gear they could get caught.  We need to look at electrician’s putty which some other teams used.

We are looking at purchasing E4T OEM Encoders.  Ideally we would keep six or eight on hand – two for drive train and at least one for any shooting mechanism.