Open Source Car Concept

Wanted: NEEDS CLEANING and SHOULD ALSO BE PUT UNDER TRUCK

- Nice - Marcin

Conversation with Dan Foukes

• Concept in mind similar to Urbee
• Considering a 1000 lb, 12-18 hp, hydraulic drive car, first plain gasoline, then moving to hybrid hydraulic
• For the truck, we want a Mercedes Unimog-like car with suspension, 60 mph. Main task is to design the suspension and steering, and then we can prototype. Once again - hydrauilic drive for add-on power units.
• 1 ton equivalent (F350) cargo capacity should be our first cut. It should have serious traction power like a F350 to do things like haul 20,000 lb of woodchips from 30 miles away, on a trailer.
• It would have attachment plates and hydraulic takeoff to handle anything that the tractor can.

Some early thoughts from Mark Rudnicki on the Open Source Car:

• Basing the OSCar on the Urbee would allow for radically faster development than starting from scratch. I suggest that Marcin contact Jim Kor and make a pitch for him to open source the Urbee.
• RepRap machines or modified larger versions could be used to produce the body panels for the OSCar, but it's unknown how resilient these panels would be to things like bumping and extreme heat and cold. If we find that RepRapped panels are not durable enough, then perhaps RepRap machines could be used to produce forms from which fiberglass or carbon fiber composite body panels would be produced.
• Using a three-wheel design like that of the Urbee would probably allow for the OSCar to be registered in all U.S. states as a motorcycle and therefore avoid a lot of legal requirements such as crash test standards.
• Using a three-wheel design would allow for the back wheel to be directly driven which would obviate a differential, shafts, etc.
• Using a hybrid hydraulic system would allow us to exploit Power Cube technology. The drive wheel would be coupled directly to a compact hydraulic motor. Regeneration from braking could also be conveniently exploited.
• Using a fairly large accumulator would allow for good city fuel efficiency and good acceleration (highway safety).
• The coefficient of drag of the Urbee is quite good: 0.146 according to http://en.wikipedia.org/wiki/Automobile_drag_coefficient.
• Plastic windows are preferred due to their lower weight over glass windows, but the windshield may have to be glass due to scratching problems with plastic.
• As many off-the-shelf parts as possible should be used to allow for quick development. Such parts could later be replaced by similar open source parts.
• A rough calculation for fuel efficiency for a maximum cruise speed of 60 MPH is about 130 MPG. An engine designed to run at peak efficiency at 6 HP would be required for this max cruise speed.
• A rough calculation for fuel efficiency for a maximum cruise speed of 70 MPH is about 100 MPG. An engine designed to run at peak efficiency at 10 HP would be required for this max cruise speed.
• The engine must have a electric starter and electronic fuel injection (EFI) (http://en.wikipedia.org/wiki/Fuel_injection#Electronic) in order for it to start quickly and reliably in all weather conditions. Engines with EFI are also more fuel efficient (perhaps 25% more) and less polluting than those with carburetors. A hybrid hydraulic version of the OSCar will by design have an engine that regularly starts and stops during city driving.
• The smallest production gasoline engine with EFI that I've been able to find so far is the Subaru Robin "EX21 Fuel Injection" (http://robinamerica.com/pfeatures.aspx?pid=226) which has a maximum output of 7 HP. Peak fuel efficiency is assumed to occur at peak torque, which, according to this plot: http://robinamerica.com/media/images/diagrams/226/0_l.png, occurs at 2400 RPM where output power is only 4.8 HP. At an output power of 6 HP, engine speed is about 3100 RPM, where torque is only about 5% lower than peak torque, where efficiency is still probably pretty good at this speed, making the EX21 a good candidate for an OSCar with at cruise speed of 60 MPH. At max engine output at 4000 RPM, where fuel efficiency is lowest, a top speed of about 63 MPH is predicted.
• This engine comes with a pull start, so an electric start from a similar Subaru Robin model would have to be fitted to it.
• We'd also need to figure out how to connect an alternator to this engine.
• I couldn't find a price on an EX21 with EFI online, but found an EX21 without fuel injection new for $381. I conservatively estimate the price of the EX21 with EFI to be $600.

• The next smallest gasoline production engine with EFI that I've been able to find so far is the Kohler ECH630 (http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=Command%20PRO%20EFI%20ECH630) which has a maximum output of 19 HP. Peak fuel efficiency is assumed to occur at peak torque, which, according to this plot: http://www.kohlerengines.com/onlinecatalog/jpg195x290/ech630_max_torque.jpg occurs at 2800 RPM where output power (http://www.kohlerengines.com/onlinecatalog/jpg195x290/ech630_max_power.jpg) is 16 HP, which is well over the 10 HP required for a 70 MPH cruise speed. At an output power of 10 HP, engine speed is a bit over 1800 RPM where torque is about 7% lower than peak torque, where efficiency is also still probably pretty good, making the ECH360 a good, but oversized candidate for an OSCar with a cruise speed of 70 MPH. At max engine output at 3600, where fuel efficiency is lowest, a top speed of about 88 MPH is predicted.
• I received a price quote of $1607.46 plus $70 for freight for an ECH630 from a Kohler dealer on April 25, 2010.

• Although, the EX21 and ECH360 are designed to run on gasoline, it's assumed that the primary fuel for the OSCar will be ethanol.
• Technical requirements for adapting these engines to run on pure ethanol or at least E85 are unknown. At the very least calibration of the ignition and fuel injection systems would have to change.
• One hope is that a variant of the ECH630 that's compatible with E85 (http://en.wikipedia.org/wiki/E85) fuel will eventually be available (http://www.kohlerengines.com/common/pdf/EIA_WinterMarch09.pdf). An inquiry to a Kohler engine dealer on April 25, 2010 regarding use of E85 in Kohler engines netted no information.

--Crank 09:57, 25 April 2011 (PDT)