Sand Casting the Engine Block

I thought some people might get a kick out of seeing how the sand casting process that we used to make our blocks and crankcases works.  It combines a bunch of different manufacturing techniques from rapidprototyping (commonly called “printing”), casting and machining.  A mold into which the molten metal will be poured to make the engine block must be made.  It has outer walls that define the shape of the outside of the block, and it has “cores” that define the shape of the internal cavities of the part.  These are made out of sand that is held together with a binder material.  The way these are made these days is to use a laser-sintering process.  A computer-controlled laser hardens a thin layer of sand in the shape that is required for the core or mold part.  Then a fresh layer of sand and binder is deposited onto the just-hardened layer and the laser makes another pass, building up the part layer-by-layer.

Sand cores for the MkII Clarke-Brayton engine

Sand cores for the MkII Clarke-Brayton engine

Above you can see a variety of the sand cores and molds that were used for our engine block/head.  Basically, you need to have sand filling up all the spaces where you do not want metal.  Building the mold is kinda like building a “negative” of the engine.  All the cores are assembled together.


Special coatings are sprayed on to improve the surface finish of the metal and ensure that sand does not stick to it.


The cores you see assembled here will be passages within the engine block.  Some of these passages will be to allow the air to flow through the engine as needed.  Some will be for coolant to flow through making sure the engine does not get too hot.s_CIMG4722

There is a last piece that goes on top of the assembly you see above but unfortunately I do not have a picture of the whole mold ready for pouring.  In designing the mold, special care needs to be taken that the molten metal will be able to fill up all the gaps completely, allowing air to escape through vents as more metal is poured in.

After the metal cools and hardens, all the sand gets broken up and cleared away, leaving just the metal part!s_CIMG9663

That part is closely inspected using 3D scanners to ensure dimensional tolerances were maintained and x-ray scanners to make sure there are no internal cracks or other problems that cannot be seen from the outside.

Next the part is put in to computer-controlled machining centers that will cut away excess material and provide all of the tightly controlled dimensions, surface textures and other features that are required to make an engine work property!

Here is a video that shows a similar process being done for a different engine block.  This video was not made at the foundry that is casting our parts.


First Pour

Our first block has been poured at the foundry – ACTech in Freiberg, Germany.  I was tempted to title this post as, “It LIVES!” We have been working on computer models of this complicated part for so long, to finally see a photograph of a real block made of compacted graphite iron instead of 1’s and 0’s is very very exciting.

MkII Clarke-Brayton Engine block just after being poured at the foundry

MkII Clarke-Brayton Engine block just after being poured at the foundry

The block is now being prepared for machining, after which it will look much sleeker!  The bulk of our smaller parts are already out for quote and we anticipate beginning testing on August 1st.  Maybe I will save the, “It LIVES!” post title for when the engine is actually breathing.

Happy Memorial Day, everybody!

Motiv Releases Design of MkII Clarke-Brayton Engine

I have been woefully absent from these pages the last several months since we started the design effort on the new engine. I am excited to finally be able to share what the team has been working on so dilligently.  The MkII Clarke-Brayton Engine is the next step in dramatically reducing fuel consumption in trucks, automobiles and generators without increasing costs.  It is also the next step in developing a highly efficient compression-ignition 100% natural gas engine that can meet the up-coming greenhouse gas emissions regulations. This is a boxer configuration split-cycle engine implementing what we have come to call the Clarke-Brayton cycle.  The thermodynamics of this engine are virtually identical to our previous “CCI” design but are implemented in a much more conventional way.  Everything that we published in our SAE paper at the 2013 World Congress holds true for this engine, but many of the difficulties related to the old engine are resolved.

MkII Clarke-Brayton Engine

MkII Clarke-Brayton Engine

Section of the MkII engine

Section of the MkII engine

As with the previous design, in the MkII air moves sequentially through three cylinders, starting at the mid-sized cylinders at the top of the section image. This architecture allows us to achieve a 56:1 compression ratio leading to a 30MPa peak pressure.  It has far less surface area for heat loss than a comparable conventional diesel due to the very small bore of the combustion chamber. The small combustion piston area leads to lower forces on the crank than a conventional engine would have if it were able to reach similar pressures, reducing rod bearing friction compared to conventional architectures. A lack of net forces on the main bearings due to the opposing forces of the piston pairs reduces main bearing friction compared to conventional engines. It expands exhaust gasses all the way to ambient pressure before the exhaust stroke.  Gas transfer from one cylinder to the next is begun at equal pressures on either side of the valve, which keeps velocities low, minimizing pumping losses and eliminates blow-down. The power is produced in almost a 50-50 split between the combustion (central) and exhaust (largest) pistons.  There is a power stroke every revolution. All valves are actuated by overhead cams. Piston ring sealing is completely conventional, eliminating the dynamic effects of the old design and greatly reducing the reciprocating mass.

The major components of the MkII Clarke-Brayton Engine have already been released to the foundry for casting and everything else should be released for fabrication within a couple of weeks.  We will test this summer at a globally renowned engine development lab and I hope to have results to share shortly after that.

A team of just three people designed the MkII from a back-of-the-napkin idea to a fully developed test engine in 7 months.  Azra Horowitz and John Clarke have both put in herculean efforts to get this done in time despite a couple unexpected thorny technical challenges along the way.  I could not be more proud to be working with them.

Babson Magazine Article

We do not focus much on PR around here (yet), but an article was just published in Babson Magazine that features us called, “Risky Business with a Purpose”.  It was a real pleasure speaking with Donna about Motiv and kinda fun doing the photo shoot out in Brooklyn with people stopping and staring wondering if I’m someone famous.  Sorry for the disappointment, people!

“I’m Bored With All Games”

“I’m Bored With All Games.”  That is something that Mark Pincus, founder of mobile game maker Zynga, said recently at a gathering of tech entrepreneurs in Israel. I have to say that I am not surprised.  Entrepreneurship and running a rapidly growing company (or a company struggling with growing pains) is enormously hard.  To keep doing it, you need real passion for what you are doing.  I can imagine that it would be difficult to maintain that passion for mobile games after a while.  Don’t get me wrong – I am not saying that games are not a worthwhile thing to start a company around. I’m a big fan of Zynga games “Words with Friends” and “Scramble with Friends”.  I’m glad Mark has made these available to me!  But he has made his money.  He has more than likely accomplished all the goals he set out with for Zynga and more.  I bet he has started yearning to make a different kind of impact on the world.

John, Azra and Abhishek discussing aspects of engine design.

John, Azra and Abhishek discussing aspects of engine design.

I’ve become kind of a snob about this after two startups dealing with major global problems.  But I also get a bit jealous.  Every time I hear about another startup that allows people to share more pictures of cute animals or babies in slightly different ways than before getting bought out for a billion dollars my outward reaction can be something like, “what a waste of time and money that could have been put to good use”, but inside I’m totally jealous.  The developers of these “technologies” had no real technical challenges in making it work.  Any software engineer can crank that kind of stuff out.  There is no risk that they won’t be able to figure it out.  They just have to figure out how to get people to use it (not easy of course) and BAM! One billion dollars one year after founding the company.  Sounds awesome.  But if a company is really trying to do something new that solves a really big problem, things are somewhat different.

So after I get over my jealousy I realize that after enormous success, these entrepreneurs often yearn to do something like we are.  And I must say, I cannot think of a more exciting or satisfying place to be right now.

Launching the Design of the Mark II Engine

What an exciting week!  I finally got the new office 90% ready and our new team showed up on Monday to begin work.  The first thing to do is introduce our new engineers.

Seated around the conference table in the new office from left to right: Ed O'Malley, John Clarke, Azra Horowitz, Abhishek Sahasrabudhe

Seated around the conference table in the new office from left to right: Ed O’Malley, John Clarke, Azra Horowitz, Abhishek Sahasrabudhe

Abhishek Sahasrabudhe came to us after finishing his MS in Mechanical Engineering at Stanford.  He has experience working on an advanced engine efficiency technology at Bosch Automotive.  He was a graduate research assistant at Stanford where he was also a teaching assistant in the finite element analysis class.  Abhishek completed his BS in Mechanical Engineering at the University of Pune in India where he graduated first in his class.

Azra Horowitz recently completed his BS in Mechanical Engineering and Physics at the Massachusetts Institute of Technology where he studied internal combustion engines under Dr. Wai K. Cheng.  He has designed a novel organic rankine cycle engine for powering submersible unmanned autonomous vehicles and was the winner of the Sherman Math Prize at Wesleyan University.

I could not be more pleased with our team, their knowledge of engine thermodynamics and design, and their enthusiasm.  It makes Motiv a very exciting place to be and we have already launched the design effort on the new engine.  This work is being done in our new office, of course.  Here are some more pictures, before we got started working in it.

Desks with Dell M4700 mobile workstations and 23" second monitors.

Desks with Dell M4700 mobile workstations and 23″ second monitors.

Brainstorming/meeting area

Brainstorming/meeting area

Break area.  Fridge and microwave to be added to the already well-used coffee maker!

Break area. Fridge and microwave to be added to the already well-used coffee maker!

We started the week out with a review of engine thermodynamics, as well as general engine design concepts implemented in applications ranging from model airplanes to Ferrari Formula 1 race cars.  It was a great way to get the gears turning (pun?) and prepare our minds for the task ahead!

Preparing for Orientation Week

Kickoff day for the design of MkII of our engine is coming soon – September 23rd. Our two new engineers, Azra from MIT and Abhishek from Stanford, will be starting that day and John will be in town for the week.  I’m busily getting the new office ready.  As you can see, it is still mostly empty.  It’s 1350 square feet in Midtown South in Manhattan on West 36th Street. I will post pictures of it once it is done.  Furniture is being delivered tomorrow.  I have the new Dell M4700 mobile workstations and 23″ monitors as well as a new PowerEdge server. Our design software should be here tomorrow.  Here is a before picture.  I’ll post more pictures once everything is all set up.

Our new, empty office

Our new, empty office

Somehow popular lore makes it seem like orientation for a startup should be full of games, lavish parties and tons of promotional gear with quirky logos.  Ours will be a little bit more like jumping into the middle of an advanced graduate thermo-sciences semester… But for us that is actually fun! I can’t wait until we finish the first part kick-off meetings so I can watch how the engine is born and see what it looks like, part-by-part.  I considered having the first orientation task for the engineers be unpacking and assembling their desk and chair, but that does not seem very welcoming, so hopefully I will have all that done before they arrive!