Mechanical Design Overview

Our Mechanical Work

The mechanical side of the electric go-kart focuses on making a functional and power delivering go-kart.

Over the course of this project we were able to design, manufacture and integrate a wide variety of parts to make sure that our go-kart operated efficiently and effectively.

Mechanical Components

In all out mechanical components are as follows:

Chassis x1

Rear Wheels x2

Front Wheels x2

Chain x2

Chain Sprockets x2

Break Discs x2

Break Calipers x2

Break Caliper Mounts x2

Break Line Wire x2

Bearnings x4

Bearing Housings x4

Bearing Housing Mounts x8

Motors x2

Motor Mounting/Chain Tensioning x2

Steering System

Chassis

We found an abandoned go-kart chassis that was missing a great amount of work in order to get it functioning again.

Old =============> New

Rear Wheels

The rear wheels we had served us well. They could still hold air and were easy to work with. Since they had to press fit to the shaft, it was nice to be able to remove the wheel from the mount and hammer the mount in. To make an extra gap with the ground we gave the shafts a camber so the rotors could be raised from the ground a little more.

Front Wheels

The front wheels were also able to hold air. One important thing here was properly aligning them with the steering rack. We obtained them not only unaligned with each other and the rack but also uncentered to the rear wheels! We had to put spacers in order to center them properly.

Chains

The chains might as well be one of the coolest solutions we have made. They are different sizes! What was critical here is that we can preserve the same gear ratio between the sprockets (our ratio was roughly 1 : 6). This meant that for the smaller chain the sprocket would visibly be smaller but still work! The other thing that we had to worry about here was tensioning the chains. Since they were different sizes each chain would experience a different chain wrap. We had to be careful about distancing them properly when mounting in order to get similar tensions too.

Chain Sprokets

As already stated, the sprockets wrapped around the proper chain size. However, we were short one sprocket at the start of the project we started manufacturing it. The FEA proved to be helpful when trying to lightweight the sprocket and with the aid of the waterjet we had successfully manufactured it.

Break Discs

The break discs were a fun part to design around. Notice that they are quite big! Our issue here was with mounting the brake and the caliper-to-shaft distance. We couldnt properly mount the calipers closer to the shaft without requiring lots of work. Insead, we increased the size of the rotors inorder for them to sit closer to the frame an successfully use the frame to mount the breaks to. We relied on mechanical breaks so we ordered breakwire and attatched lines to the pedal.

Break Caliper Mounts

As previously stated, as we progressed during our second sprint, we realized that the only mounting points we could use on the brakes where either to the tubing backrest or the bottom of the chassis, which would be a hazzle. Longer mounts would create larger moments, so we suck with more rigid mounts and the compromise of larger rotors.

Break Line Wire

Bike brake line wire, connected to the brakes and the pedal.

Bearings and Housings

The bearings we decided to use are double shielded bearings intended to withstand high loads and stresses. Manufacturing the bearing housing was done with one of the Olin shop's Tormach CNC machines. It was first designed in CAD, then passed to CAM and then run with gcode on the tormach. We needed to make one more housing to have 4 and properly secure the shafts. After sprint 2, we realized that we had to redo the mounts of the housings, welded pieces of steel that bolt the pillow block as seen on the right. We tried waterjetting and bending them but failed. We tried again with a 2 by 1 box tube and made it work.

Motors

We found these motors from scrap. Both motors have an output of 1800 Watts. They worked reliably with the motor controllers we purchased and had working shafts & bearings inside.

Motor Mounting/Chain Tensioning

For motor/mounting and chain tensioning, we designed and manufactured 2 plates that had holes and slots. The holes were used to mount the plates to the chassis and the slots were used to slide the motor back and fourth. This way, if we were to slide the motor away from the chain sprocket, it would tighten the chain. A chain must have a 2% slack in chain in order to have optimum chain tension. Anything less than that would cause for the chain to slip, or even worse, come off.

Steering System

For our steering system, it is a rack and pinion system that was previously already integrated with the chassis, thanks to the current seniors who worked on it during their freshman year.

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