OSL Week 1: Kickoff, Team + Client Selection

tldr: Over the summer, I’m participating in Open Style Lab, to design accessible clothing for a client with a disability. We had our kickoff, and I got to meet all of the students and select our client preferences; learned things, met team, much diversity

Over Summer 2014, I’m participating in Open Style Lab, an awesome program based at Boston which matches occupational therapists, designers, and engineers to create a clothing solution for people with disabilities. Each team of three is matched with a client, a person with a disability in the area who have specific clothing needs, depending on their disability.  Teams are given plenty of support, ranging from a variety of workshops every Saturday to expert mentors who are able to provide guidance. We are also given resources  (read: MIT Hobby Shop Access, SETC, lectures to introduce us to amazing people :D) to build our first prototype, which we will showcase at the end of the summer, both at MIT and at the Boston Science Museum. Why is this necessary? Some people with disabilities are unable to wear the same kind of clothes that able-bodied people can. Depending on their condition, they may not have the hand dexterity to use zippers or buttons,  they may not be able to fit normal sized clothes because of a prosthetic, or normal shoes may not fit their bloated feet – it depends on the individual need or condition. At this point, clothes that disabled people can wear is limited to only specific or specialized wear, and the normal fashion industry overlooks these needs.

Kickoff (6/13):

On the weekend of June 13, Open Style Lab had its kickoff. There were 24 students: 8 engineers, 8 occupational therapists, and 8 designers (though these ranged from design students to business majors). At OSL, people are really passionate about their fields of study, and everyone is coming together with one task: functional, accessible clothes.

The team members and their experiences are pretty diverse – there are students still figuring out their career paths, people long graduated, employees with full-time jobs. Their experiences in working with disabled client is also varied: from the occupational therapists who are trained to work with them every day, to people like me, who have had no previous experience. I am looking forward to working with people who have diverse skill sets, to help us create this product.

After meeting the other OSL students, we sat down to the student-client matching process. We were given the names and descriptions of the 8 clients who had an idea of what they wanted us to work on. Again, the list of clients was pretty diverse: perhaps they can’t wear long pants because they can’t put it over a lower-leg prothesis, they have bloated feet making shoe selection difficult, they can’t wear certain fabrics, or they have issues with temperature regulation. All in all, I’m astounded by the loss of independence that accompanies a disability, especially as they are limited by the dress code that society often imposes.

Team Match (6/14):

How does OSL train and lead 24 students to successfully meet with clients, design a product, and present it successfully? Every Saturday, the OSL fellows participate in workshops, designed to lead us along the process of creating our product. “Learning”  workshops are interspersed with “Making” days at the SETC (South End Technology Center), as well as a “Immerse” portion: responsibility to keep in touch with our client and show them our progress through the weeks.

The next morning, the OSL fellows filed into MIT, ready to start a workshop of prepping us to talk with our client.We got to listen to lectures, teaching us how to meet and interview clients (ethnographic techniques), how to document the process with videos and pictures, and how occupational therapists think.

The OSL staff also sorted us into our teams, based on our preference for a client. We were paired with our client, Rachelle, a graduate student researching depression at MIT who has sensory processing disorder, SPD, which means that she is unable to wear nylons. We were also matched with our team, consisting of 1 engineer (me!) as well as an occupational therapist and a designer. I got to meet Derrick, earning a masters degree at Tufts in occupational therapy, and Kathryn, our designer who is working in a nonprofit to teach entrepreneurship.

Team Rachelle: Kathryn, Designer (right); Derrick, Occupational Therapist (middle); Me (left)

Final Competition + Reflections

Final Competition Day

See Charles’ blog post 🙂

Photocred to shewu and charles!

IMG_8434 IMG_8427 IMG_8426 IMG_8420 2014-05-03 01.37.54 2014-05-02 20.10.30


Riding Phoenixkart around was exhilarating. The main thing to notice, though, was the instability. Being a 3-wheeled kart that torqued heavily and also rode low to the ground meant that I did a fair bit of scrubbing the ground with the back edge of the kart. A few reflections.

1) The chain fell off twice :(, both times while going full speed around corners. That still needs debugging

2) The tensioner got loose a few times, which helped the chain to fall off. It was very hard to tighten as well. If I were to re-design this, I’d make the sprocket/chain system much more modular and accessible.

3) The motor got (understandably) hot, but thankfully, there was no smoke. The lawn tractor seat was comfortable, the kart accelerated nicely, and it rode smoothly (8 inch wheels were fine, though a bit bumpy on the parking lot).


If I were to design this kart again, I would…

  • Make a 4-wheeled vehicle. There’s better stability, and 2 motors is more power!
  • Not buy a 130A Kelly controller when there are 40A fuses on the bateris ^-^
  • Make a smaller go-kart. We aimed to do that, but we ended up having a pretty nice, comfortable kart in the end. It could have been smaller though, but this complaint is just nitpicky.
  • Have the kill-power switch in a slightly more accessible spot. I mean, reaching behind you to cut power isn’t the most intuitive.

What I learned:

  • This class is awesome! I came in knowing nothing about go-karts, and I left with the resources on how to build things that I didn’t know how to build. Now, when I want to build something new, I’ll know where to find blogs, people, and resources that will teach me how to build things. I’m also more confident in my ability to design large things – I’d only previously designed small robots in MASLAB, and designing something that is able to support my weight and move quickly is different.
  • Finding where to buy things. Charles makes us choose where to buy everything for the go-kart, which means that we learn the best sites to buy hardware. It’s a pretty important skill to learn to spec items of mcmaster,buy them on ebay or harbor freight, etc.
  • Everything is machinable (with the right tools, of course. Please use the right tools).
  • CADing is great, but check with actual parts.


All the Electronics + Debugging

Well, I haven’t written in a while – have been procrastinating until the end of finals and then relaxing for a couple of week but…it seems like I should probably update now, perhaps…a  month after the competition :D. First, a post about all the frantic last minute fixes and debugging. Then, I’ll write another post with the results of the competition + reflections 🙂

I left off at the formation of Milestone 7 (vehicle frame check point) and Milestone 8 (making electrical diagrams). The next milestone was to actually complete the electrical system. Near the end, everything blends into a blur of soldering, testing, and taking apart the chain/motor, as we started to operate on a tight timeline to finish before the race.

Wiring: A night of soldering

Aisha and I came in on friday and basically stayed until we’d finished soldering that electrical system, following our electrical system diagrams. I used a lot of the 4mm bullet connectors – replacing some of the ring terminals with them, simply out of taste.

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bullet connectors I soldered to the motor controller replacing ring terminals

We soldered most of the connections, using XT60 connectors as the main connector from the battery to the rest of the system. (The diagrams are shown in the previous blog post). I also sat down and finished CADing the battery box. I’d previously ordered wood from Ebay, and I set out designing a fingerjointed box to hold the batteries and also a mount for the switch. Unfortunately, the box (and thus, the switch) were behind us – still within hand reach – but we’d just have to learn to instinctively reach behind us to get to the kill switch. (2 switches, one for the precharge resistor, the other the large Hella power switch). The beautiful battery box came out perfectly – t-nuts, fingerjoints, and all! But I had to scrap it – in the CAD, I forgot to put the chain in, and when lasercut, the box conflicted with the chain. I decided to admit defeat, get rid of the offending box sides, and just velcro the damn batteries to the bottom piece of wood.

Battery Box
Battery Box

Hall effect sensors:

Because we used brushless motors, we needed hall sensors to tell the motor controller where the rotor is. First, the hall sensors needed to be calibrated, and we spent many tired hours figuring out the right configuration – at first, nothing worked. This was because the tiny hall sensor board was very difficult to solder precisely. Charles helped us to debug, and we discovered that our hall sensor board was shorted out. I got another board and this time, after careful soldering and calibration, it worked! The hall sensors, however, caused me the most problems in the electronics. Later, the 3D printed hall effect sensor mount broke in the middle of testing, which meant that I spent valuable time taking down the chain/sprocket/motor mount to replace it.

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Hall sensor board on motor


After figuring out the hall effect sensors, we were finally able to drive Phoenixkart around lab. Our first test drive was recorded by Charles with his newly bought Chinese dashcams. With further test-driving, we discovered some problems. First, and foremost, our chain kept falling off. This was largely because our kart “dgonzed“, aka, it didn’t have enough triangular supports to keep the two body pieces of 80/20 horizontal with the front of the vehicle. This meant that when the driver leaned into sharp turns, the kart leaned into them too – during the race, you could hear the kart scraping the ground when I took it around really fast on turns. That was fun.

2 wheels on the ground
I drive with 2 wheels on the ground

Back to the problem. The chain kept popping off the sprocket because as we turned corners, the back of the kart would torque, especially because of the way we designed the back wheel supports. Essentially, the back wheel supports are cantilevered, which allows the frame to tilt substantially around the wheel. If I were to design this again, I’d make the wheel axle go through the entire column.We solved this by shortening the chain and perfecting the tensioner. We only finished debugging this the night before the competition. If I were to redesign this kart, I’d make it more stable by having 4 wheels.

Problem #2: Pinning the steering column: the steering column shaft collars that Aisha had cut out just weren’t staying, so she pinned them to the steering column by simply drilling a screw into the shaft collar and the column.

Problem #3: Blowing Fuses: Our battery fuses could only pull 40A, but our motor controller was able to output up to 130A. This meant that when I pressed the throttle too hard continuously, the fuses blew. Charles handily taught us how to program the kelly controller to only output 40A.

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Tensioner, Masterlink, Electrical Diagrams & Milestone 7

We originally planned to finish Milestone 7 after Spring Break but then…the Hobby Shop Waterjet broke down. There was a bit of delay 😦 So our Milestone 7 was put off until the parts came in.


I designed a tensioner, waterjet the pieces, and proceeded to assemble everything. The attachment of the spring was more difficult than expected – the spring was harder to manipulate than I thought, so I proceeded to shove it (with much effort) onto the little ledge I’d waterjet. I also drilled a hole into the screw to mount the spring onto it. And it worked! The tensioner successfully applied tension on the chain. However, after all this hassle of designing and machining and figuring things out, I decided not to use it because the tensioner contact with the chain caused a bit of friction, and in the end, the costs would outweigh the benefits of this additional tensioner (also because we can just tension the chain by adjusting the motor distance on the 80×20).

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Drilled hole through screw to attach spring
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Janky attachment of spring to tensioner


We also assembled the chain onto the motor sprocket.

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Aisha finished the steering!

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The brake lever I found fits onto the steering wheel with a screw and half-circles of metal.

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Completing Milestones

I drew up electrical system diagrams for the power side and signal side. Aisha and I stayed late on Friday night soldering the electrical system!

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Power Side Wiring
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Signal Side Wiring

We passed our Milestone 7! Except that our vehicle actually does not fit through a 33″ door, as we planned for it to fit through 36″ door. Oops.  So we’re going to recalculate the steering and re-waterjet a piece for the steering that will work with a shorter front length.


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Final CAD


Lab Shenanigans

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Spring Break – Friday: Brakes + Mounting Chair

Today, I mounted the brakes. Thanks to youtube + Charles/Jamieson, I figured out where everything goes. With the handle brake lever I yanked off a New House bike, I attached it to one end of the bike cable and housing. Next, I needed to mount the black band brake to something. I took a scrap piece of 1/4″ aluminum, drilled holes in it, and fastened it to the wheel attachment. One end is screwed into the band brake outer casing; the other end is fastened to the motor plate.

Brake Attachment   2014-03-28 07.12.41

Next, the brake kit came with an attachment that would stop/hold the housing and allow the cable to pass through. I fastened that to the seat H plate.

Mount Brake attachment to underside

The other end of the cable goes into a screw on the brake. Here’s a picture of the final assembly!

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Finally, now that everything else was secured, I was able to mount the chair by screwing it in from underneath.

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I decided to take a break / finish up all my schoolwork over the weekend. Our rolling frame is due this coming friday! But I’ve pretty much finished my part! The only thing I can do now is wait for the set screws from the McMaster order to arrive so I can mount the sprocket and chain onto the motor + wheel.


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Spring Break – Wednesday + Thursday: Motor Mounting, Battery Cage, Tensioner, PhoenixKart

Motor + Sprocket Mount

To fit out sprocket to our motor, I needed to drill out the sprocket to 8 mm to match the motor shaft. I then decided (after much deliberation) to use set screws – I haven’t had good experiences with them in the past, and I definitely don’t want set screws detaching for such an important part as a motor and sprocket. But I decided to make this set screw larger, 10-32: more surface area for contact. So we got set screws (90289A337 on Mcmaster). I then drilled and tapped a hole on the sprocket for the set screw.

Machined Sprocket

Lastly, I keyed the shaft on the motor to provide a flat for the set screw (never use set screws without a flat).

Milled a Flat on Motor Shaft
Milled a Flat on Motor Shaft

I did all this machining at the Edgerton Shop, an awesome shop open for students on campus, as they had larger milling machines than the IDC. [pictures] I came back with the motor and tried to assemble everything. The motor mount conflicted with the 80×20…so I dremeled it down. So Dremel. Much fun. Wow. It was pretty fun.

2014-03-26 09.23.39

Then, sad problem. When I assembled the motor, I realized that because we had changed the dimensions on our plates for holding the motor (because they had worked in the CAD but not in real life), the little sprocket could not fit onto the motor shaft and also line up with the larger sprocket. It was off the shaft by approximately 0.4 inches. I was dejected as it means we can’t use the original motor plates to hold things together…adding 0.4″ will mean it won’t line up with the 80×20 pieces. But I really wanted to test everything else about the motor, so I cut a new piece of 80×20 and attached it with the original pieces by, well, taking advantage of the fact that there are 2 sides to attach things to. As you can see in the picture below, the top hole doesn’t match the 80×20. I also took a bandsaw to the useless part, as it conflicted with the motor mount.

Bandsawed part of the Aluminum Plate off
Bandsawed part of the Aluminum Plate off

After that, I could attach the motor, put the chain and sprocket, and proceed to design a tensioner, now that I could see everything by eye.

Small Sprocket, Chain, and Large Sprocket now line up!
Small Sprocket, Chain, and Large Sprocket now line up!

 Brake + Flipping our Kart:

After happily spinning the wheel and seeing it work, I suddenly realized that our brake wasn’t working anymore. It had unscrewed itself because brakes have a preferred direction (thanks Jamieson!), and if you spin the wheel in the other direction, the band brake screws itself off. Good thing we realized this before installing everything permanently. So, we needed to flip the direction of the wheel so that when we drive forward, we can keep our brake screwed on. Instead of taking everything off, I realized I could just flip the kart upside down and then reverse the seat mount – that would solve all our problems. So our new kart looks like this:

Kart Flipped
Kart Flipped

Also, I got more of an idea of how to put our brakes in place (thanks youtube) but I can’t cut the wire and housing until the steering is in place, so that’s tabled a bit. Brakes are definitely a priority, though, because it’s on the checklist of Milestone 7. I took a hand brake lever off a bike.

Brake Lever for our Go-Kart
Brake Lever for our Go-Kart



Our motor is movable, so that in itself could act as a tensioner. But because we only have 11 teeth on our small sprocket, we decided to design a tensioner that allow the chain to contact more teeth. I CADed out a tensioner . The spring and the screw are quickly represented by cylinders in the model. We will waterjet the tensioner frame (which simply holds the spring and the tensioner at a correct height) and the tensioner bar, which is pushed down by a compression spring. I also designed the tensioner piece to be exactly the same as our sprocket, so it will work with the chain. I also ordered longer 1/4-28 screws (2 inches).

Designed Tensioner
Designed Tensioner

 Front Plate, Steering Wheel+ PhoenixKart

Aisha designed the front plate that will go on the front of our kart, act as a footrest, and hold the accelerator. Early on in our brainstorming process, we decided we wanted a theme for our kart. We decided on road-kill kart phoenix kart, complete with phoenix steering wheel and a footrest that looked like flames. Artistic Aisha used splines to CAD and then lasercut  the front plate and worked on the steering wheel. Pretty, isn’t it? Though to prevent us from impaling ourselves on our kart, we’re going to have to make the steering wheel / front plate less pointy. Don’t want to kill anyone either.

PhoenixKart's front plate
PhoenixKart’s front plate in CAD
2014-03-28 07.17.08
Steering Wheel


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Spring Break – Monday + Tuesday: Assembling Wheel, Seat, Steering, Mounts

Waterjet Pieces (and Waterjet Taper)

Our waterjet parts finally came in Monday night! It was super exciting. Now we could start assembling all the pieces, make more measurements, and construct more things! There is a lot to do (as evident on the spring break post). But first things first – even though we had added 0.005″ to our holes to account for waterjet taper, it still manifested itself  in slots not fitting :(. So Aisha and I filed. And filed. For a few hours.

Significant filing effort was made to make sure the slots fit
Significant filing effort was made to make sure the slots fit the tabs

Wheel Mounts

Remember those wheel mounts we designed so it’d be easy to adjust? This was important so we could make sure the wheel was centered (because it’s slightly asymmetrical from the band brake/sprocket on either side). It took a fair amount of fiddling.

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Making sure wheel is centered
Making sure wheel is centered

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motor electronics back design
Looks similar to the CAD? 🙂


Seat Mount

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Waterjetted H Bar attaches Seat to the frame

So our awesome lawn tractor seat (with minor cosmetic defect, $20 on ebay!) fits onto our waterjet H bar. We’ll put this on our kart. Assembly order will be a bit of a hassle, because we can’t tighten down the H bar onto the frame when the seat is attached. We’ll just assemble the H bar first and then put the seat down at the end. Where the seat goes is still pretty variable because of COM optimization. I should probably put the material properties on Solidworks to find the center of mass (COM). We also placed spacers stacks of washers under the set to adjust tilt of chair.

Stack of washers
Stack of washers

We’re going to buy spacers to replace the stack of washers, now that I know the correct height.

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Aisha’s Steering

Aisha (my partner) and I split up the work. She is working on the steering, steering arms / column, front section, while I’m designing the frame/kart back/drivetrain. It’s been working out well. Here are some pictures of the steering arms and steering columns.

Steering Arm
Left Steering Arm2014-03-25 01.21.04
Steering Column
Steering ColumnSteering Column Attachment


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They also take a significant amount of maching. Here is a picture of Aisha dremeling.

Dremels are fun
Aisha Dremeling; Dremels are fun


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Spring Break! – Scheduling

Thank goodness it’s spring break – time to take a break from classes. Aisha and I are both staying over spring break and working on our go-karts. Last week, Aisha and I ordered our go-kart on Mcmaster (joking! but not really) and designed all the pieces to be waterjet. We’re currently waiting for our water-jet parts and Charles will be able to get to them on Monday. In the meantime, I’m UROPing, catching up with friends, and doing some design. Sadly, I broke my mouse (I tend to destroy anything I use daily so the earphones / mouse / watch / computer that I end up keeping for a long time are super durable only because I haven’t managed to break them). But I ordered a new mouse so…I’m not going to be CADing because that would be painful.

Aisha are planning to start coming in once our parts are waterjet. Here is our beautiful list of things we need to do:

Steering and Front assembly:

  • Thread and cut bolts (for axles)
  • Thread 80×20 15″
  • Thread vertical steering supports x6
  • Cut 1/4″ rod
  • Cut Aluminum tube
  • Design and CAD steering wheel
  • Front footrests
  • CAD pedal

Back and Frame Assembly

  • build/design a tensioner
  • Assembling everything (1 day)
  • Assemble sprocket and chain
  • Assemble brakes
  • Find a bike handle (email Mike)


  • design Battery cage
  • buy hella switch + configure all electronics

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2.007 Milestone 6: Making an MDF-kart

Redesigning the kart rear wheel drive + mounting:

Aisha and I spent a frantic Friday solidworksing and Arduinoing (for physical homework #6 – program a motor controller!

I realized that I had designed a back wheel mount that was lower to the ground but it didn’t match the design for the front wheels. Oops. Here is our new design! I put in plates similar to the the ones we had for our front wheels to hold the back wheel in place. We also decided to mount our electronics in the back of our kart (as seen here!)

motor electronics back design

Kart with Person
Kart with Person

Prototyping and Building our Kart out of MDF

On Saturday / Monday, we went in and prototyped our kart. We lasercut the joints / pieces out of MDF and cut the 80×20 into our frame pieces with the cold saw.

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Assembly assembly assembly

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Wheel Mounts + Rear

A Lesson on Designing for Assembly

When designing, it’s important to think about the order of assembly and the easiness of assembling it. In Solidworks, everything can assemble fine, but in real life, it won’t work the same way. This lesson was duly learned when I sadly tried to put together the MDF-kart and it was hard to screw in the wheel mount nuts.

old motor mount
Looks beautiful in CAD
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Cannot actually tighten this; can’t reach my fingers in 😦

We’re going to redesign this.

Rules, Deadlines, and Organization:

The milestone 7 deadline is looming closer – by April 1, we need to have a rolling frame done! That means it needs to be able to roll, brake, have a person seated, etc. Here are the requirements:

1) The frame is assembled and can support weight without unreasonable flexing.

2) Mechanical subsystems such as steering, braking are mounted rigidly and do not wobble, flex, or move with interference such as scrubbing or scraping.

3) The vehicle can roll freely without mechanical interference in the drivetrain

4) From a jogging-speed push, the vehicle is able to lock up its braking wheel(s); the vehicle’s braking force exceeds available traction.

5) The motor is mounted rigidly with fasteners, but not necessarily connected to the drivetrain.

6) ll provisions for hooking the motor up to the drivetrain are finished (e.g. pulleys are properly bored and mounted, tensioners and retainers mounted)

7) Fasteners are properly used and installed  (e.g. all screws and bolts tightened, bolts are not used in shear, standoffs and spacers are not made of stacks of washers)

8)  No portions of the frame are bent or forced to fit an assembly – all machined and fabricated components fit true and square, or as-designed

9) All materials used in the vehicle are final and documented in the Bill of Materials. No prototyping mat’ls (e.g. class-supplied wood) or “tape and zip ties” construction is present.

10)  The final seating or riding arrangement is present.

This is a lot for 2 weeks! Considering we have yet to order a few parts (namely brakes and fasteners) and shipping (when will our ebay seat get here?!) it’s a bit worrisome. But we’ll be able to do this! Also, out of the next 2 weeks, one of the weeks is my hell week and the other week is spring break. Aisha and I will likely be spending our spring break in the IDC. However, we do need to get a lot of things done this week, especially because a lot of things take downtime – shipping and waterjetting take time. Since we’ll be building a lot in spring break and Charles cannot officially encourage building, we won’t be able to order parts / waterjetting that week, so we’ll need to order everything now! So, we plan to have all our waterjet components finished and formatted this weekend, as waterjetting takes 1 week of time to deliver :\, and we plan to order the rest of our parts. We’ve definitely come a long way!

Making a tensioner:

As mentioned, we need to make a tensioner because our sprocket has too few teeth.

Research on the internet: http://machinedesign.com/archive/belt-and-chain-tensioners

I was thinking about simply screwing on a tensioner, but since the chain stretches and produces oscillatory movements, most tensioners you can buy have springs to damp the vibrations. That’s why many tensioners have a lever arm to automatically tension the chain.

We tried this design first:

Motor Mount Front Face

Next Steps

We are submitting our finalized waterjet pieces and BOM on Tuesday. Hopefully this is all that is left! After Friday, Aisha and I will begin building, and hopefully, we already have all our pieces. The final step to fulfil Milestone 7 is assembly and after that, electronics.

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