He only wants 30 kw, many engine could do this at lower rpm. Low rpm is not a
problem as long as it is high enough to keep the oil pressure up and not cause
vibration that may cause crankshaft failure.
-----Original Message-----
From: "Lee Hart via EV" <ev@lists.evdl.org>
Sent: 5/03/2018 04:55 p.m.
To: "R. Sparks Scott" <spa...@kcst.com>; "Electric Vehicle Discussion List"
<ev@lists.evdl.org>
Cc: "Lee Hart" <leeah...@earthlink.net>
Subject: Re: [EVDL] Genset range extender
R. Sparks Scott <spa...@kcst.com> asked me to post this for him, as he's
not subscribed. He wrote:
> Aside from the worn-out idea that impromptu series hybrids are
> anything worth bothering with, John needs to know that his *diesel*
> genset head is intended to be driven by a diesel engine, not a
> gasoline engine. Why this matters is that all directly-driven
> generator heads for diesels will be optimized for 1800 RPM at rated
> output (for 60Hz), while gasoline (and LPG) heads will expect 3600
> RPM.
>
> Obviously, if he is intending on rectifying the output to DC, it
> doesn't matter that the head won't need to be on-frequency of 60Hz,
> but forcing a gas engine to lug along at lower RPMs to make the
> voltage more-or-less correct is going to be a strain on the ICE and
> probably give him a big hit in available peak voltage, and by
> association, available current into his battery pack/motor.
>
> My inclination would be to stop encouraging him until he understand
> the dynamics of what he is proposing. Series hybrids don't work well
> in the best of designs, and he's throwing together a collection of
> incompatible components that are sure to disappoint.
That's a good point. While I've seen gasoline gensets that ran at 1800
RPM, most do indeed run at 3600 RPM. This makes them smaller (but
noisier). Gasoline engines need to run fast to generate their rated
horsepower.
But if he's driving it with a car engine, most of them will happily run
at 1800 RPM for hours on end. You just can't get anything near its rated
horsepower. For instance, it might require a "100 HP" engine to produce
30 HP continuously.
Projects like this are always a trade-off between the "right" way, and
the "expedient" way to do it. Using what you have, in unconventional
ways isn't perfect, but may be good enough to get by.
--
You never change things by fighting the existing reality. To change
something, build a new model that makes the existing model obsolete.
-- R. Buckminster Fuller
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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