Introducing Rick

Rick explains one of his setups, a fluorescent bulb that has been altered so that it can run off of a 12V car battery.
Rick explains one of his setups, a fluorescent bulb that has been altered so that it can run off of a 12V car battery.

He was the fairy godmother that the powers that be bestowed upon us.

Rick Masumbuko showed up one day in the middle of the Banda market and introduced himself to a mzungu that was just walking by. Sophie showed up to Kigogo that day with an unfamiliar face in tow. “This is Rick!” she called out as she arrived, and I poked my head out from the kiosk to see a small man, a backpack slung over one of his shoulders, walking right beside her.

Max, Rick, and Sophie in matching DHE gear.
Max, Rick, and Sophie in matching DHE gear.

Earlier on in the trip, we had reached out to some of the DHE alumni regarding their work in Banda. One of them was Ben Koons, and ‘08 who was responsible for the genesis of DHE hydro. In one of his emails, he recommended a Congolese man whom he had worked with when DHE first established the Banda sites. The man had previously lived in Banda but now lived somewhere else, and Ben CC’ed him on the email.

Apparently, it was simple as that. Soon after, Rick happened to check his email at the house of a friend, a Peace Corps volunteer. Within two days, he had hopped on a bus and was headed to Banda. We had no idea that he was coming, but I guess that when you’re the only group of mzungus in a village, you’re not that hard to find. Rick, as we later learned, is also little short of a local celebrity. With all of his many informants, he had no trouble finding us. He has friends throughout the village because he once lived in Banda for eight years, and whenever we walked with him, we would quickly find ourselves the awkward third or even eleventh wheel to a happy reunion.

In the two weeks that I was able to spend with Rick, I’ve grown to truly believe that he’s one of the most exceptional people that I’ve ever met. Rick is fifty-eight. He dropped out of school after primary school when his father passed away. He learned French and English while working as a tour guide for Nyungwe Forest, and he did research on primates with Europeans that he met through his work.

And they would bring him textbooks. He pored over them, applied the theory using what hardware he could find and absorbed it. Never has he attended a class, done a problem set, or had a professor guide him through a difficult concept. He is a self-taught electrician and has an exceptional understanding of his craft.

Rick met Ben while working as the receptionist at a Nyungwe lodge. Ben was on an assessment trip to find potential hydropower sites, and when they met, Rick showed him what he calls his “12-volt DC light.”

Rick's 12V DC light. Many of the components were taken from broken radios.
Rick’s 12V DC light. Many of the components were taken from broken radios.

I was confused by the terminology at first because I imagined a simple set up, the likes of what all of us have seen in intro physics: a lightbulb and a battery. Of course, Rick’s system is much more. Power-saving fluorescent bulbs are especially valuable in developing nations because of the limited supply of electricity. However, the issue with these bulbs is that they are designed for 220V AC—for use in home electrical systems. Those that use our hydro sites in Banda get their electricity by charging their 12V DC car batteries at the site. To get 220V AC, they must hook up their battery to an expensive and often unaffordable alternator.

The purpose of Rick’s bulbs is to circumvent this issue. He removes the electrical components in the fluorescent bulbs so that only the fluorescent tube is left. He then assembles a collection of transistors, resistors, electrolytic and paper capacitors, and a transformer, scavenging many of the components from broken radios. His small hands wire up a set up that can convert 12V DC to an AC voltage high enough for the bulb to light up. The user can then hook up the bulb to their 12V battery, and voila. Fluorescent light.

Rick demonstrates his 12V DC light to us with our battery.
Rick demonstrates his 12V DC light to us with our battery.

I assume that Ben was just as astonished as I was. Rick told me that Ben then realized that he was perfect for the job. Because of his work as a tour guide, Rick knew every single river and waterfall in Nyungwe, and he was clearly technically qualified.

Rick still uses the multimeter that Ben gave him in 2008 and also has a well-loved copy of Practical Electronics for Inventors—it too is a gift from Ben. Both came in handy that day he showed up at Kigogo, I briefly talked through the system with him and then pored through the book. Meanwhile, he happily drew himself a schematic of our electrical system and checked voltages with his multimeter.

This summer, the team had struggled with the realization that no matter how well we designed the system, something would fail in our absence, just as it had done so many times before. In the past, a technician new to the system would be called in from the city, and he would make decisions without entirely understanding the system. An example of this was the dump loads that were removed from the system at Kigogo. Without them, the system voltage can get too high and even cause a battery explosion. The technician had realized correctly that because the dump loads were heating up, they were taking power away from the system. However, the outside technician incorrectly assumed that removing them would simply charge batteries more quickly.

Site operator and manager training would not be enough to mitigate this issue. At one point in training, we even learned that one of the operators had trouble reading a multimeter. Rick was our saving grace. By the time he arrived, he had already planned that he would move back to Banda and work at the sites as a full time job. Three days later, he had already rented a house and was spending his nights there. We later even learned that the house didn’t yet have a bed. He was so excited to be working with electronics again that he could not be fazed.

Rick helping the site operators, his new employees, review their contract.
Rick helping the site operators, his new employees, review their contract.

Jean Baptiste’s Wedding

JB&ClementineDSC00767

This afternoon, one of our site operators got married. Jean Baptiste, or JB, as we call him, is twenty-two and works both the day and night shifts at Kigogo. He had invited us to his wedding within the first few days of our arriving in Banda. Unfortunately work at Nyiragasigo kept us from attending the morning religious ceremony at the church, but we headed to his and his wife’s new home for the reception.

We lugged twenty-four glass bottles of Coke, Sprite, and Fanta, purchased at a store on the way there, as our gift, as Pete had told us that it was customary for soft drinks, not alcohol, to be served at weddings. As soon as we arrived, we were given seats in the front row, right across from JB and his bride, Clementine. Despite the choir’s energetic singing, coming from a row over, the newlyweds were stiff and hardly made eye contact with each other, let alone with us. For the first portion of the reception, we worried that his inviting us had somehow only been a formality and that we, as muzungus, were not actually welcome at this sacred event. JB doesn’t speak English, so we’d never been able to speak to him without a translator, but our interactions each time we’d worked with him at Kigogo had been overwhelmingly positive. Despite the language barrier, his smiles and his proud and correct responses whenever we asked him technical questions had given us confidence in our partnership.

I even worried for a moment that JB and his wife was an unhappy marriage. But then I remembered that some customers had complained to us that JB was not always at the site and accepting batteries because he was off with his fiancé. So this wasn’t it.

We were given plates of food, which we gleaned from watching the other guests that we were supposed to only partially finish. The leftovers went to children that stood at the fringes of the ceremony. Eventually, JB and his wife went into his new house as a traditional part of the ceremony, and a small television set with about a square-foot screen was turned on to our left. A Rwandan music video started playing, and the kids wove through the crowds of chairs and people to form a tight half-circle around the screen.

As with the music at the church, the television set and associated speaker system were powered off of a single Chloride Exide battery, charged at our sites.

Far to our right were an even larger speaker system and a two-person band. One man played the keyboard while another played the electric guitar. They wore matching John-Lennon style glasses and accompanied the choir’s singing. Later, when I got up and started walking around the edge of the reception, I noticed that their electronics were powered entirely off of a large generator. Batteries can only carry so much charge, and the speaker system would most likely have drained the batteries far too quickly. It was a reminder of the limitations of our battery-charging system.

As I passed by the musicians’ booth, JB came out of nowhere and stopped me. “Welcome to home,” he said, and I thanked him, thinking that he was welcoming me to his reception. I then heard my name called from his house, where Pete was gesturing for me to come in. JB smiled at me and escorted me inside.

In the first room I stepped into, the rest of the DHE members were sitting on a bench across from Clementine, who looked up when JB stepped through the door. She’d changed out of her white wedding dress and into traditional Rwandan attire. When he sat down next to her and started talking to Pete for him to translate to us, his body language toward Clementine changed drastically from when we’d been outside. He held her hand and cheerfully explained how he’d courted her while Clementine giggled and looked embarrassed. Pete joked that if he had met Clementine first, he would have stolen her away from JB, to which Clementine covered her mouth and laughed even more. Unsurprisingly, JB was happier than I’d ever seen him.

Civils: Solutions for Erosion

Alison landed in Kigali on Wednesday, and Joey, Max, and Pete, our foreman, left Banda at 4:30AM that morning to go pick her up and go on a materials run. Mountains surround Banda on all sides, and accessing the main road involves a two hour, steep uphill hike up the side of one of the mountains. They were hoping to catch the 7AM bus to get to Kigali by around noon.

In the week or so leading up to their departure, we started modifying our site at Kigogo. Rwanda has a rainy season, which falls roughly during our winter, and we have to make civil modifications to both of the sites so that they can fare better against the increased water flow during this period. One of these changes involves increasing the number of overflow channels in the system. When there is more rain than our system was designed for, our channels overflow, and water gushes down the hillside that our channel runs along. The water erodes the soil from the hillside, causing a mini-landslide from our channel, down to the kiosk.

Overflow channels create an alternate escape for the excess water. By lowering the height of a short length of channel wall, whatever water is above that level flows into an alternate path. At the erosion points, we lay cement so that the water is funneled into a PVC pipe. PVC pipe then carries the excess water down the hill and returns it to the river. The water originally came from upstream the same river.

An example of an overflow. This overflow is at the intake at Nyiragasigo where we divert some of the water from the river into our hydro set up. Behind the channel wall is just a continuation of the original river. When water passes through that overflow, instead of going downhill or through a PVC pipe, water directly returns to the original river. This intake overflow limits the amount of water that originally enters the system. This overflow was made by the 2008 trip when they originally implemented the system.

Looking downhill from the channel at Kigogo, we can see the river, the kiosk that houses the turbine and the electrical set up, and the hill that we will be placing the PVC pipe for the overflow in. The PVC pipe returns the water from the river to the river that it originally came from.

Another issue we’ve been looking at is the stagnation in certain parts of the channel. We’ve noticed that there’s a build-up of silt in certain parts of the channel, and although this isn’t entirely negative as it means that silt is settling out of the water before the water goes through the turbine, it also means that water may not be travelling through the channel quickly enough. To fix this, we will be increasing the slope of the channel at certain points, such as the channel right by settling tank at Kigogo.

Increasing the slope of the channel could also help decrease erosion. At Niragasigo, the slope of the channel at two of the erosion sites is close to zero. By increasing the slope here, we increase the speed of water flow through the channel. When there is excess water entering the system, having a higher slope moves water down the channel more quickly and minimizes overflow.

A temporary solution to soil erosion is to lay soil bags by the channel. This increases the height of the channel wall and also prevents contact between the water and the hillside’s soil. This is not an ideal or permanent solution to the erosion, but it is cost-effective and very easy for local workers to replace in our absence.

At Kigogo, we’ve already laid the cement for the new overflow by the settling tank and changed the slope of that segment of channel. We’ve also laid our soil bags. Right now, we’re waiting for the cement at Kigogo to dry and for Joey and Max to return with PVC pipe for the overflow.

They’ll also be returning with metal to build a sluice gate. Typical hydro set ups use a rotating gate valve as a sluice gate, but to maximize the ease of repair, we’re planning to build our sluice gate using only a metal panel, secured by L-profiles. The sluice gate stops water flow into the system so that the system can be dried out for maintenance.

We’ll also be able to finally implement our electrical system in its entirety. The plastic box that we’ll be mounting our electrical set up in will be arriving, as well as additional circuit breakers for the Nyiragasigo system.

While we’ve been waiting, Sophie, June, and I have worked on making updates to the Impact Analysis survey, learning more about the electrical system, and taking measurements at Nyiragasigo in order to inform civils design.

Joey, Max, Alison, and Pete are planning to come back tomorrow afternoon. We’re excited to get back to work at Kigogo!

Cooking & Kinyarwanda

Pascal cooking

Dinner every day is close to a four-hour affair. Tonight, Sophie and I started cooking the rice a little past six while June was out visiting Kigogo with Pete. Joey and Max, meanwhile, worked on calculations for civils designs. “Civils” refers to the larger, structural parts of the system, like the channel that brings water to the turbine. Joey and Max eventually left for the market and bought around 1500RWF in groceries, roughly three dollars US. This is enough to feed the eight of us for the night.

Cooking with the open wood-burning stove has made us think of the bioenergy team and their previous initiative for clean cook stoves. The stoves that we cook with spew smoke, and although we open the windows and the door, it’s uncomfortable to be in front of the fire for a long time. The smoke bothers me, and I often have to step out of the room for a breath, but I notice that our Rwandan counterparts are unfazed.

Pascal is a student from the Kigali Institute of Technology that has been working on the sites with us, and he seems completely unfazed by the smoke. Jeremiah, a long-time DHE contact in Banda and a doctor in the village health clinic, and Pete, our foreman, can indefinitely continue to stoke the fire and peel potatoes in the small kitchen.

For the people cooking with it every day, the smoke can be lethal. Over the years, the air pollution takes a serious toll on their health. Because they’re not bothered by the smoke, there’s also little incentive to look for alternatives. Jeremiah’s petroleum-fueled stove sits next to the wood stove, but he leaves is unused. As a doctor, he has one of the highest incomes in the villages and is the most conscious about his own health, but still, the price of petroleum is too high.

Once we finished cooking, it was past 8:30 and we wolfed down the food. Two nights ago, we talked with Pascal, Jeremiah, and Pete about marriage and relationships in Rwanda, the overturn on gay marriage in the US, and the expansion of the universe. It was a great night. Tonight, as we finished our dinner, Pete announced that we’d be learning more Kinyarwanda. We pulled out our notebooks and turned on our head lamps.

How do you call this?: Ichi cyitwa gute?
I want: Dashaaka
I like: Ngunda

Egg: Umagi
Potato: Ibirayi
Sweet Potato: Ibijumbo
Bread: Umugati
Onion: Ibitunguru
Tomato: Einyanua
Rice: Umucheri
Salt: Umuunyu
Pineapple: Inanasi

One: Rimwe
Two: Kabiri
Three: Gatatu
Four: Kane
Five: Gatanu
Six: Gatandatu
Seven: Karindwi
Eight: Umunaani
Nine: Icyenda
Ten: Icumi

Spoon: Fork
Fork: Ikanya/Ifork
Knife: Icyuma

Other words that we already knew:
White person: Muzungu
Yes: Yego
No: Oya
Good morning: Mwaramutse
Good afternoon: Mwiriwe
How are you?: Amakuru?
I’m good: Ni meza.

I didn’t get to write down all of the words that we were taught, but hopefully I’ll get to learn more as the weeks go on. We finished at around ten, and the six of us from Dartmouth talked for a few hours, updating each other on our progress for the day and talking through some of the more controversial design decisions. Our days are long but rewarding.

Alison, our last traveller, gets here at the end of the week. We’re excited to see you!

We’re Finally Here! But First, Our Path to Banda…

2013-06-14 12.01.16

Muraho! Hello!

I’m Shinri Kamei, a ’16 and a prospective electrical engineer from Japan. I’m a part of hydro’s travel team to Rwanda this summer, along with Joey Anthony ’12, June Shangguan ’13, Max Sloan ’13, Alison Polton-Simon ’14, and Sophie Sheeline ’16.

We’ve been in Rwanda for almost a week now, and we’re currently in Banda, where we’ll be spending most of our summer. In 2008, DHE’s hydro team set up two hydropower sites at waterfalls each about a thirty minute walk away from the village. Most villagers use car batteries as their source of electricity, and these can be carried to the sites and recharged. Previously, the only source of electricity had been a micro grid, six hours away by foot.

The path to the hydro sites is like a scenic hiking trail, and after finally meeting our local partners, I know that the next two months will be amazing. Our house is pitch black at night, and a small battery, charged by one of the hydropower sites, lights up the kitchen that we cook dinner in. I learned to say 100, 200, 300, 400, and 500 in Kinyarwanda, the native language, and our contractor and foreman, Pete, now knows the same in Japanese. Our toilet, a hole in the ground more than thirty feet deep, feels charming, and the freezing shower is refreshing. The next two months will be amazing.

But our trip didn’t start a week ago when we got on our plane at JFK. Let me step back and walk you through what we’ve been up to.

In the two weeks between Dartmouth graduation and our departure to Rwanda, they hydro team split up into sections. June, Max, Alison, and I stayed on campus and spent upwards of fifteen hours a day in Thayer, working through an electrical intensive with Prof. Charles Sullivan, one of DHE’s advisors. We got a chance to thoroughly test and understand the electrical system implemented by previous trips and identified its limitations. We spent so much time together that we all shared the same cold. We huddled in Thayer’s otherwise deserted Advanced Design Laboratory with tea, honey, and popcorn. We somehow made it out alive.

 

June led the charge on the intensive. She’s a computer engineer that just graduated from Dartmouth with her B.E. and is headed to Michigan in the fall for a Master’s in engineering. Prior to the intensive, she’d been the only one in the group with electrical expertise in the system. She quickly caught us up to speed and started presenting us with different design diagrams. Our questions would lead to changes in the design, and once we had our new design for the day, she’d respond with her trademark “good,” complete with the extended o-sound. The next day, we’d present our design to Sullivan, and his critique would inform further alterations.

Max is the other ’13 on the team. Being a mechanical engineer, electricals were completely new to him, but by the end of the two weeks, he could answer any of my questions about dump load sizing, charge control, and anything else I was unclear on.

Alison, a ’14, is a NYC native and the past year’s DHE president. She spent her spring term away at the Johns Hopkins Applied Physics Lab and returned at the beginning of summer for our electrical intensive. Alison is a fiercely organized computer engineer and is a lover of lists and Greek yogurt. During those two weeks, she juggled communication with Joey, who was already in Rwanda, documentation, finances, logistics, and of course, electricals, with a sage-like wisdom.

At the end of the two weeks, June, Max, Alison, and I finally came up with a new system design that we were happy with.

 

A lot of our work was defined by Joey’s work in Rwanda, which was going on at the same time. Joey, a member of the 11X travel team had worked in Banda two years ago, and was project leader of hydro in the terms that followed. The Monday that our intensive officially started, he got on a plane from Tokyo and departed for Rwanda alone. In Kigali, the capital of Rwanda, he hired a contractor and interpreter. Upon arriving in Banda a few days later, he visited the sites we’d been working at and discovered that not only had storage batteries, crucial buffers for the system voltage, had been removed from both sites, and one site had zero circuit breakers.

These situations made sense. The storage battery could be sold for profit to new customers. Circuit breakers, if designed to trip at low current levels, made the system safer but could be a nuisance. These current levels were higher than those expected during normal operation, small but harmless spikes could trip the breakers and cut the circuit. They could also break on their own and were difficult for the villagers to replace.

These revelations informed our design of the system, and we were able to come to Banda better prepared.

Meanwhile, Sophie Sheeline ’16 prepared material for Impact Analysis from California. An engineering major with a focus on applying engineering to global health and development, Sophie had been working all term on preparing surveys and surveying methods for the summer, so that DHE can better understand the impacts of our sites on the people in Banda, and how we can make our impact bigger and more positive in the future. In the weeks leading up to our departure for Rwanda, Sophie finalized survey documents and plans with the help of previous travelers and Peace Corps volunteers that spent their last two years in Banda.

Thank you so much to everyone, both inside and outside DHE, that helped us along the way. We’ll make you proud!

Images from Last Summer

Strange to think that it’s almost been a year! Last summer, DHE’s hydro team went to Nyamirambo, Rwanda, to implement a new hydropower site. Some of the photos have gone a little under the radar, but everyone should take a look.

They can be found here.

Here’s a taste of some of what can be found on the page.

Local friends we made while waiting for an interview.
Local friends we made while waiting for an interview.
View of the site from downstream.
View of the site from downstream.
An interview.
An interview.
Natalie Burkhard '12 and Adam Khamis (Imperial College London, e.quinox, civil engineer) grout the rebar frame into the bedrock.
Natalie Burkhard ’12 and Adam Khamis (Imperial College London, e.quinox, civil engineer) grout the rebar frame into the bedrock.
Mayor aka Pierre Niyomwungeri—our foreman and translator as MC.
Mayor aka Pierre Niyomwungeri—our foreman and translator as MC.
Kevin Francfort `15 and Natalie Burkhard `12 work on the rebar framework for the settling tank.
Kevin Francfort `15 and Natalie Burkhard `12 work on the rebar framework for the settling tank.
http://www.flickr.com/photos/thayerschool/8178945821/in/set-72157631991926519/
http://www.flickr.com/photos/thayerschool/8178945821/in/set-72157631991926519/
Kurt Kostyu '12 chatting with a villager wearing Kostyu's sweatshirt from his home state.
Kurt Kostyu ’12 chatting with a villager wearing Kostyu’s sweatshirt from his home state.
The battery they already have and use to charge cell phones and power lights. They had to go several hours away to Ruramba to get it charged, before our system became operational.
The battery they already have and use to charge cell phones and power lights. They had to go several hours away to Ruramba to get it charged, before our system became operational.
The team discusses the project.
The team discusses the project.
The site and the river valley.
The site and the river valley.

Hydropower Project Group: Steps for Amateur Sand Casting

We gave a primitive overview of the casting process in our first blog post, but to further clarify the technique to readers, we decided to prove an in-depth guide.  Online resources for sand casting are hard to come by, and those that exist are mainly semi-professional—far beyond our skill level.  Hopefully, this sand casting guide can help students like us learn from our triumphs – and (many, many) mistakes – and try sand casting for themselves.
Materials needed:

  • The object that you want to cast
    Must have a simple shape. Any cavities must exist on the same plane; for instance, a standard coffee mug cannot be casted because the cup’s main cavity runs perpendicular to that of the handle’s.
  • Casting flask
    Make a box with walls and a bottom, and another with only four walls. The top and bottom boxes are called the “cope” and the “drag,” respectively.
    The size of the box will differ according to the size of the object being cast—allow at least two inches on all sides of the object to allow for the heat of the aluminum pour.
    The cope and the drag should be the same length and width, although height can vary. Must be of a sturdy material. The reasons for this will become clear in the step-by-step instructions.
  • Something that can be used to tightly pack sand into the mold, a “rammer”
    The sand must be packed very tightly into each part for the mold to stay in place. While we used our hands to press the sand in early one-part molds, we found that the mold maintained its shape much better when we had a solid object to physically pack the sand into the box with. For the two-part mold, working without a rammer is virtually impossible.
  • Fine silica sand
    Playground sand, available at low prices, works well.  Silica sand is chosen because of its relatively low porosity; sand made from other rocks can absorb moisture and explode when it comes into contact with molten aluminum.
  • Fire clay
    This may be slightly more difficult to obtain. It must be able to withstand the high melting point of aluminum.
  • Water


Recommended:

  • A mesh sheet to sift sand through
    Anything with holes small enough to allow through grains of sand but not small pebbles should work. We have found that a kitchen sifter with fine, double-layer mesh serves the purpose well.


Steps:
Making a Sand-Clay Mixture

  1. Make a 1:9 ratio mixture of clay and sand. Mixing in small quantities is recommended to ensure that the materials are mixed together well.  When you think you’re done, mix again; inconsistent mixtures are more likely to crumble apart in a two-part mold. Each time that you reuse a sand-clay mixture, make sure you sift the material well to make sure that you are not working with any clumps.
  2. Mix water into the mixture. Make sure that the added water is thoroughly mixed into your sand before adding more. For the amount of sand-clay we generally deal with, we add our water in roughly tablespoon increments. Use the test below to determine when your sand is ready.
  3. Squeeze (hard!) a handful of sand into a hotdog shape. You should be able to pick up the shape and break it in half without crumbling. However, when loose, the mixture should flow through your fingers similar to dry sand. Adding too much water during this step will lead to bubbling during the cast.

Mold-Making
Here, the mold-making method will differ slightly according to the object being cast.

  1. Once the mixture is ready, fill the drag to the brim with the mixture. Pack the mixture very tightly into the drag using the rammer. The mixture should not move in the mold when the box is jostled. The sand will compress; continue to fill and ram until the entire drag is filled.
  2. Level the sand, using a rod to scrape off excess sand.
  3. Pack sand tightly into any of the object’s cavities and scrape off excess sand, so that any cavity or valley in the object is filled and leveled.
  4. Place the object cavity-side down on the flat sand surface of the drag.At this point, it is wise to lightly tap the object and make sure that you can raise it without taking the sand with it—just as if you were building a sandcastle.
  5. Sprinkle a bit of dry sand on the drag’s surface. This will help keep the two parts of the mold from adhering to one another.
  6. Place the cope on top of the drag and situate them so that they are exactly on top of one another. Aligning them correctly at this stage is crucial, as you will have to realign them later. Slippage will result in a skewed cast.
  7. Pack sand into the cope. When sprinkling the firstlayer of the sand-clay ixture into the cope,becareful not to disturb the dry sand layer.
  8. When adding sand to the ope, include at least half an inch of extra sand-clay mixture above the top of the object. This will depend on the size of the object being cast. Using the rammer, pack the mixture tightly into the cope.
  9. Once the surface of he mixture in the cope has been rammed smooth, identify where the highest point on one end of
    yourobject is in the sand and poke a hole here, using a pointed tool such as a pen.Make it pinky-sized—this is the hole that you will pour your molten aluminum into.
  10. Find the object’s highest point on the opposite side and also open a hole here. This will be used to allow steam to escape from the sand as molten aluminum flows into your mold.
  11. Gently gently, making sure not to shift it horizontally, lift the cope straight up off of the drag.
  12. Gently gently put the cope down on a smooth surface, being careful to not to jostle it. Unnecessary movement here may cause your entire mold to fall through.
  13. That process should have left your drag and object looking just as it was before you added the top half of the mode.
  14. Lift the object straight off of the drag, being careful not to let any of the mold mixture move out of place.
  15. Replace the top mold to exactly where it was before removal of the object.
After this step, all  you have left to do is pour molten aluminum into the pour hole. Details about building a furnace to melt aluminum are soon to follow!

Hydro Project Group: Buckets Through the Ages

We’ve come a really long way since our first cast, and we wanted to share some of the Hydro buckets that we churned out as we figured out how to sand cast.

Bucket 1:
As explained in the last blog post, the sand-clay mixture that we used in our casting attempts back in September had water content that was too high. When we poured aluminum into the sand mold, the water evaporated upon contact and bubbled through the aluminum. The aluminum solidified as the bubbles were pushing through it, and we ended up with this.

Bucket 2:
In our second attempt, we still weren’t quite sure what was going on.  We now know in retrospect that too much clay traps air and that too much water causes rapid evaporation. The combination caused bubbling in the poured aluminum. Regardless, it appeared slightly more solid than our first messy attempt, so we agreed to try less water next time and hope for the best.

Bucket 3:
Since this made our first cast, we were getting more comfortable with the one-part mold–dangerously so. Enough that we thought we could re-shape the stem of the bucket after the mold slightly collapsed. This resulted in a scrawny stem. We did, however, manage to significantly cut down on bubbling by lowering moisture content.

Bucket 6. Buckets 4 & 5 looked roughly the same.

Bucket 4, 5, and 6:
Since our previous attempts prompted more reading, the DHE Hydro team looked to text and online resources for advice. We quickly learned that a 1:9 part clay to sand mixture was the ideal, with barely enough water for the sand to clump together. This revelation vastly improved our casting and led to consistent buckets with a one-part mold.

Bucket 7:
This half-bucket represents the hydro team’s first attempt at the intricate, tricky, patience-strangling two-part mold. Its sleeker sides meant that it required half the molten aluminum to cast, and thus led to a turbine of half the weight. Unfortunately, we believe that the aluminum solidified before reaching the rest of the bucket, resulting in our stubby bucket. But it put the two-part mold within our reach.

Bucket 8:
Following our first limited success with the two-part mold, we found it more finicky than ever. Our attempts resulted in collapsed messes, to the point that–due to time constraints–we agreed to make just another one-part mold. In that, this cast wasn’t especially special; trying to quench it too soon, however, we accidently broke off its handle before it solidified.

Bucket 9: After some serious two-part mold practice during the Holiday break, DHE members returned to campus to redeem our last attempt. The molding went well enough, but during our first pour the aluminum solidified before filling the entire negative space. Unwilling to leave any bucket unfinished, we made a second pour into the air holes on the bucket’s opposite side, resulting in a patchwork bucket but a successful one overall.

Bucket 10:
Similarly, the aluminum in our next pour hadn’t reached a high enough temperature to seep into every corner of the bucket. This resulted in one of the best surface textures we’ve achieved, but a bucket that would be useless in the field.

Bucket 11:
In a cast done not an hour later, DHE members managed to form our first full bucket, casted in one pour, made in a two-part mold. We made sure that the aluminum had been heated well enough to correct our last two mistakes, which resulted in a grainier texture but a decent bucket. Since we now knew we could make a successful two-part cast, we turned our focus to the surface texture—aiming for a smooth surface that would lend well to a turbine.

Bucket 12:
In our past two-part molds, we had found ourselves having difficulties with sand sticking to the template bucket’s stem when we lifted the top mold. This ruined our clean edges and often meant starting the whole mold over—a process that could take as much as twenty minutes. To rectify this concern, we placed a small slip of paper on top of the bucket’s handle, which the wet sand would cling to instead of our template bucket. The quick-fix resulted in our cleanest, most beautiful bucket yet.

The top half of the mold, complete with the paper slip that we inserted between the bucket’s stem and the top mold. The slip helped the sand around the stem stay in place when we lifted the top mold.

 

Cecilia Robinson ’16, Shinri Kamei ’16

Hydro Project Group: 13W Sand Casting Update

Sand Casting: the process of pouring molten metal into a sand mold to make a metal casting.

Purpose

This project’s value lies not only in its end product, a working hydropower station for a rural village in Rwanda, but also in its ability to be replicated on-site. Sand casting requires only basic materials: bricks for a furnace, fuel to burn, aluminum to melt, sand to mold, and wood for frames. By using such readily accessible materials, DHE hopes to instruct the local residents to be able to fix their own turbines and start new hydro projects on their own.


Basic Sand Casting

Minimally, sand casting requires two parts: a furnace and a mold. Stock aluminum is collected in a steel crucible, which is then placed inside the furnace and heated to roughly eight-hundred degrees. During this melting process – which can take fifteen minutes or much longer, depending on the fuel and furnace – a mold of the object is made out of sand.  At the beginning of our sand casting practices, we used a simple one-part mold which worked by impression, similar to footsteps on a beach.  The melted aluminum is then poured into this impression, and after a few minutes of cooling and quenching, the object is finished.

The mold-making phase requires ramming the sand around the mold to ensure that it maintains its shape.

This type of casting – i.e., implementing a one-part mold – resulted in turbine buckets with vertical sides: well-defined buckets, but too heavy for real use.  As casting progressed, we moved to the two-part mold, a trickier but more accurate version that replicated full 3-D objects.  Just like the name suggests, a two-part mold involves two parts which result in a cavity between two layers of sand: three air holes leading to the cavity allow room for aluminum to be poured and air to escape.  Our resulting buckets have been lighter, smoother, and much more suitable for turbine use.  This more complicated procedure, however, has presented new challenges that the DHE hydro team continues to meet and resolve.


Baby Steps

When the Hydro Team started out this term, we had minimal experience with sand casting. Previously, DHE had made hydropower turbines in Engineering Sciences 89-90 classes or at a professional foundry, and we only had books and internet tutorials on which to rely. We spent one of the first meetings exploring sand casting in front of computers, googling “How to sandcast aluminum;” and for the freshman, our first “homework” was to choose a specific component of sand casting and research it before the weekend.

When we started, we knew two things: that we would be using a sand clay mixture to make a mold in the box, and that we needed to melt aluminum. This turned out to be more difficult than we’d anticipated.

We were proud of our first attempt, but looking back, the bucket that we ended up with looks almost hazardous.  In making our sand clay mixture, we thought that in order for the mold to retain its shape, it would need a high water and clay content. We were wrong. As we poured the molten aluminum into the one-part mold that we’d crafted, the excess water started evaporating upon contact, making bubbles in the aluminum. But molten aluminum solidifies rapidly at room temperature—and even faster in snowy Hanover. The water vapor didn’t bubble through the aluminum so much as push it to the side, where the aluminum solidified. As you can see, there are holes in the bottom of our first bucket, and when flipped over, the aluminum bits are sharp and barely stuck together.

It took us a few more attempts before we realized youtube’s potential as a resource. In one trial, the mold-making took so long that the group working at the furnace to melt the aluminum (melting point ~660°C) accidentally melted the steel crucible (melting point ~1370°C) containing the aluminum. For this furnace, we’d used a steel bucket insulated with concrete, leaving a cylindrical hole in which to place fuel and the crucible.  Toward the bottom of the bucket, a pipe circulated air – supplied by a hairdryer on the other end – into the furnace, giving us greater heating efficiency. Of course, aluminum came seeping out from the melting crucible and clogged the hairdryer-pipe combination that we used to feed air into the furnace. Lopsided casting boxes also did not help our progress.

A few instructional videos later, we learned that the sand clay mixture should have about a 1:9 ratio of clay to sand as opposed to the 1:1 ratio that we’d previously been practicing. As for water, we only needed enough for the sand to be able to maintain a “hot dog” shape after squeezing it with our hands. When broken in half, this ideal hot dog would break cleanly without crumbling. Our previous mixtures had the consistency of snowballs; but this new mixture would still flow smoothly through your fingers if you scooped some up.

Our sand casting improved greatly after this revelation, and our casting became fairly consistent.

One of the buckets that we made near the end of the one-part molding phase of our sand casting.

We then decided to move on to the two-part mold.

This first two-part mold was surprisingly successful. The aluminum was poured in through the main pouring hole and flowed into the mold up until the air holes—but no farther. The highest point on the bucket is on its back, and we put the air holes at the farthest end of this back; however, the lip of the bucket continues on.  The aluminum was flowing through the mold slowly and solidifying quickly, so that once the aluminum reached the air holes, it couldn’t move into the lips since there was no place for the air there to escape.


Winter Research

Several of our members worked over break to replace our hair dryer as our furnace’s air circulator, instead using wooden billows to manually pump air through the system.  Manual billows relinquish our dependence upon electricity for a hair dryer and can also be made on-site in Rwanda.

Additionally, two winter projects tested the viability of a brick furnace.  Both successfully melted aluminum in a brick furnace, so the practice has carried over into our work for this term.

One DHE member with ceramic training constructed several clay crucibles, as our steel crucible sometimes proved difficult to pour, and we thought we would give it a try.  On returning for winter, we tested one larger clay crucible, but removed it from the furnace due to increased melting time.

Lastly, as our two-part molds had little success before break, one project focused solely upon the two-part mold, pouring wax instead of aluminum for ease of process.  This has also translated into the greater success of our two-part molds this term.


13W; Winter term

A brick furnace.

Our original steel-bucket furnace has now been replaced by a brick furnace, which forms a square around the crucible and will hopefully increase efficiency and reduce melting time.

The one-part mold has been abandoned: future casting will be exclusively two-part, as the two-part mold shows promise for excellent turbine buckets following more practice. On Jan. 9th, three days after returning to campus for the winter term, we headed to the woodshop to make new boxes to replace the parellelogram-esque boxes that we’d used in the fall term. Two days later, we did our first cast. Unfortunately, the aluminum had not melted enough when we did our pour and filled only half of the mold. We filled the rest of the mold from its air holes a few minutes later.

Two casts, made on Jan. 14th, 2013. The bucket to the left was cast first, and with the second, we managed our first full bucket.

This morning, we conducted two more trials, and on the second, successfully made our first full bucket. On the first bucket, we encountered the same problem we had before: the aluminum did not reach the extremities of the mold. The surface of the bucket was rough and felt similar to some of the buckets that we’d made earlier in the casting process. We believe that this is because there was higher water content in the sand clay mixture that we used, and this should be an easy enough issue to avoid for the next round.

For this cast, we melted almost double the amount of aluminum necessary to do a single cast. The aluminum was able to maintain a higher temperature throughout the duration of the pour, and the aluminum flowed smoothly into the mold. We believe that this is why we were successful in this attempt.


Future testing

More tests will be done using ceramic crucibles, including three different sizes.

A separating agent may be employed within the two-part mold, which would result in cleaner separation of the bucket from the sand and give a finer finish to our end bucket.

For future tests, more documentation will be made concerning several variables which might be affecting our molds: e.g., pouring temperature, aluminum amount, and exact water-sand ratio.

Cecilia Robinson ’16, Shinri Kamei ’16