Back with a little more info on the D2-55.......
You can pull a maximum of about 19 kW from the front of the engine
, up to three separate pullies with 6.8 kW each. This spreads the load on the crankshaft as several belts pulling in different directions tends to balance the bending load on the crankshaft. Installing a single
side load of the size which you envisioned will place a heavy bending load on the crankshaft and is best to be avoided. If you design a bearing supported shaft and drive the alternator
from that, it would be much better.
The difference in the amount of power which can be taken from the front or the rear of the engine
has to do with the design of the crankshaft. In the case of the D2-55 engine, the diameter of the rear of the crankshaft is about 80mm, while the front of the crankshaft at the large end of the taper is probably 25 mm. Plus, the power that is taken from the rear end is completely axiel in nature....no bending loads. The loads on the front of the crankshaft are almost completely side loads, and if you overload the crank with side loads, it can break, or wear out the front main bearing, or other things which are no fun.
As was mentioned earlier in the thread, circulation pump flow is low pressure and high flow. With a fully open thermostat and 35kPa external circuit back pressure, the D2-55 pump will flow as follows:
. 70 l/ min
2800 RPM 75 l/min
3000 RPM 80 l/min
This means that the 12 volt pump shown earlier, with 12.5 l/min will be significantly undersized for the job at hand.
I think your idea of multiple smaller alternators with the standard circulation pump might be a better way to go.