Some musings on future power trains
As an owner of a 32ft DP with a Cummins 6.7 diesel and two F150 pickup trucks with 3.5 Ecoboost engines I have long felt that the Ecoboost outperforms the Cummins used in this application, is quieter ...
Forum Discussion
rgatijnet1 wrote:
Perhaps something like today's locomotives. The drive is actually from electric motors with a diesel engine supplying the power. Maybe with some better batteries that can better recapture the lost energy used for braking etc. Throw in some solar and you might reduce the need for diesel power to keep the batteries charged. With the electric drive you have plenty of torque for even the heaviest MH and you should be able to minimize the size of the engine needed to keep the batteries charged.
Diesel/Electric locomotives are a completely different drivertrain with a different purpose.
Direct drive from diesel to wheels would be more efficient. The problem is big slow turning diesels (as in thousands of HP) have a very limited RPM range where they put out good power. To build a mechanical transmission that can handle 3-6,000hp would be large, complex and not very efficient. Then try to link 5 separate engines accelerating simultaneously and the complexity goes up by an order of magnitude.
On the other hand if you use a generator and electric motors as a transmission, you can spin up the diesels to their ideal RPM and then draw power as you need it. Since electric motors can develop max torque from 0 RPM, it's great for starting from 0mph under heavy load. Even better, it's really easy to link the electric motor controls for multiple engines on the same train.
Now they've put a lot of effort into minimizing losses but the real reason is it's effectively just a better replacement for a mechanical transmission. The efficiency advantages to trains come from two primary things. Low rolling resistance (steel wheels on steel rails blows away rubber tires on uneven pavement). Rail cars drafting at 8ft spacing drastically reduces drag compared to the same cargo carried by multiple semis.
In cars and trucks, a mechanical transmission with gears works much better. The loads are small enough and the motors have a wider RPM range where they can generate good usable power. But they operate over a wider range of speeds with more common speed changes. The use of a hybrid system is intended primarily to keep the ICE operating at it's most efficient RPM.
