2nd Laser Cut Drive Assembly

Happy Holidays and happy new years to everyone!

We have fabricated a new laser-cut prototype with more details. Next up is the waterjetted final assembly.

The structural support for the motor is comprised of three plates which we
named "Base", "Shark Fin", and "Rear Fork".  As shown in the photo, we
laser-cut new plywood prototypes of all three.  The seat is supported with
aluminum angle, which might be the actual pieces that we use in the final
build.  The actual LMC-170 motor had indeed arrived and was relocated
slightly in the new Shark Fin plate, so it is now well clear of any
interference.  The Base plate still needs to be remade to solve U-bolt
alignment and clearance issues.

We have received the LMC-170 motor and intend to install it during IAP.

second laser cut prototype

Custom Electronics from the EE Team

Overview

The EE team this year is working on some custom electronics in addition to all of the COTS (commercial off the shelf) work we do on the larger electric vehicles. Our responsibility has grown to not only include the interface and safety circuitry for the large motor controller, battery pack, and system logger for the trike but also a variety of custom electronics.
We have two (new) main projects):

1. Electronic actuation of a brake system for the NY bike trailer
2. A custom BMS (battery management system) for small (bike) to medium (moped/go-cart) electric vehicles

In addition to these two tasks, its also my job to teach electronics to the EE-team; the engineering goals of the projects have to balance cost, effectiveness, and the potential to teach electronics design principles.

Our lab space was recently upgraded with a new electronics test bench (courtesy of the MIT Edgerton Center) to accommodate, in part, our new role.

Brake system

We needed a way of actuating a pair of rim brakes on the bike trailer, and while a mechanical linkage was preferred initially, mocking up the requirements for quick disconnects and cable pull routing lead us to shift to electrical actuation. The system uses a worm-driven motor to pull and release the brake cable; because this can not be back driven (a property of the work gear) the motor does not need to stall to continue apply brake force. While the ME's worked on enclosures and mounting, team produced a schematic and a board layout for this task using an Attiny85 micro-controller at the center. 

Layout for NY-bike-trailer-brakes

Battery Management System

We are working on a battery management system that is fully modular. Someone who wants to build an EV, once our system is complete, could connect several 4s2p modules together with a central controller to form a 'smart pack' capable of self balancing and charging. We are still at the system design level and currently working on a digital communications bus to communicate between all of the individual modules.

More updates are coming your way in the future.

Follow us on github

Mock-up of the Drive Train config

Busy day today at EVT!

The MechE team built an awesome mockup of the drivetrain design out of laser parts, sprockets and zip ties.

yes... our final version will have acrylic sprockets!

lauren and erich dismounting a wheel

Drive Train and Brake Drive Design

This weekend there was a lot of progress in the drive train design as well as in the trailer brakes.

We arrived at a motor decision, we'll be using the LMC-170 motor.  It is a bit smaller than the motor used in the eSuperbike but it is still an axial flux PM DC motor, it can give us a lot of power (...a lot). We ran some simulations to determine the gear ratio we should use.

Speed Time curve for Trike at 0% grade

Speed-Time for 10% grade

screenshot of simulink model (made by Abraham, Roberto and Nigel)

The plots above are at a voltage of 50V (duty cycle of ~50% in the controller), also at the speeds shown above our speed is limited by the no load speed of the motor (which is of course dependent on the voltage) this means we have the freedom to increase our speeds considerably if we increase the voltage a bit. We'll be limiting the motor speed via the motor controller output voltage to stay within legal limits.

From the data shown and practical considerations of the size of the sprockets we arrived at a gear ratio of 8. Erich and Alex are currently busy designing/buying the sprockets using the #35 chain specs. Jacob and Will were busy all day yesterday CADdding out the mounting of the motor. Here is a picture of the current design.

notice the eccentric motor mount that allows for tensioning the chain

We have put in the order for the motor and as soon as we get some more detailed cad for the motor we can go ahead and manufacture the mounts.

The brake team had a very productive day, we decided to try out some work-gear driven motors (like windshield wiper and car window motors) to actuate the brake cables. These motors have huge gear reductions which makes them very hard to back drive which is great for us. The simplicity of the motor will allow us to drive it open-loop to open and close the brake calipers.

c-clamp holding the motor for testing

jack and j-rod testing out the motor driven brakes

We powered the motors from a power supply and the mechanism worked well. The addition of these brakes will give us lots of stopping power and keep us safe in the road.

The EE team also had a big day yesterday but I'll let them give you guys an update in a separate blog post.

EV Party (featuring a Model S)

This weekend we had some guests that came to check out the team! Scott and co. came over to EVT and we had an EV party in the alley. Lots of cool vehicles that got riden including: chibikart, chiquicycle, jamcycle, luis-vespa the Porsche and a Tesla Model S!

scott and alex with jamcycle and luis-vespa

the model S in all its glory!

TEST RIDES!

Charles and Chibi got outgassed by the model S

Kurt driving with Style

Scott on Chiqui-cycle

Scott and the team after he broke chibikart

the FSAE kids pleading kurt for a ride

Scott fixing chibi

the Porsche (beautiful as always) 

shot of the two e-cars

alex pretending to know how to drive

alex on jamcycle 

moto-sisters

????

obligatory group pic

Energy Night!

Last Friday we had the opportunity to be part of MIT Energy Night for the second consecutive year!

We took the eSuperbike for its yearly crawl down the elevator as well as the pocket bikes and the trike/trailer. The event was a lot of fun and we made many important contacts in the energy industry. Here are some pictures of the event.

michelle and john 

rango talking electrons

moving the esuperbike

jubilant joey on the trike

Trike is here!

We got our trike from Bicycleman this week!

Our Mechanical team has rapidly started working on mounting a Lynch drive train on the existing trike. Lots of cardboard engineering being done!

cardboard models of the motor and mounting panels

We are currently studying different mounting strategies as well as different style of Lynch motors to use.