[DML] Re: RPM Relay - A Modern Alternative

["bitsyncmater" <david.mckeen@xxxxxxxxxxxx>]

Appreciate your concern but if transistors were as unreliable as you 
suggest then our new cars are really death traps.

Safety is the major reason I built this replacement.  I have read of 
many owner driving on the freeway and their engines cut off due to a 
failed RPM relay.  Lucky no one has suffered as a result.  Try 
pulling of the DC beltway during rush hour.....


--- In dmcnews@xxxxxxxxxxxxxxx, "David Teitelbaum" <jtrealty@...> 
wrote:
>
> I would suggest you test all possible failure modes. This is a key
> safety item and it MUST "fail safe". I applaude your efforts to
> improve the Delorean but you may be allowing yourself too much
> potential liability exposure. The current RPM relay available from 
the
> vendors has a low failure rate and it only seems to "fail safe". I
> have never heard of an instance of a properly wired car where the 
RPM
> relay failed in a constant run state. Even if you are not planning 
on
> making any money on this you certainly don't want to lose money
> either! Just defending yourself in a lawsuit can be costly even if 
you
> win! Maybe a double-redundant circuit could make it less likely to
> fail "ON". A relay (mechanical) element has certain inherent safety
> advantages. That's why it has to be constantly energized, it opens 
the
> circuit if loses signal (fail safe). A shorted power transistor can
> make the pump run constantly (even if the motor should stop with the
> key on). Just substituting a power transistor will reduce the power
> requirements but that's not all that the relay does!
> David Teitelbaum
> vin 10757
> 
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "tho323" <tho323@> wrote:
> >
> > I have been beta testing a new, re-engineered RPM Relay design, 
and
> > wanted to share my thoughts about it. I have posted a full review 
at my
> > blog (link below), and here are some key excerpts:
> >
> >
> [moderator snip]
>



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