REFLECTOR: How to protect the battery bus

[Sid Knox]

Hiro, I am in Keith's camp here... I have never before heard of a shunt in 
the hugh current starter circuit.  I can think of not one valid reason for a 
shunt in this line.  Some of the posters have mentioned protection from 
shorts... but that is not what a shunt is for.  It is no suprise the engine 
cranks slow using a shunt with enough resistance to fry itself on two or 
three hundred Amps.

You say "The shunt drives the ammeter."  IMHO it makes no sence to attempt 
to measure starter current with anything other than a Hall Effect, clamp-on 
meter and that is only for diagnostics and has little utility as a cockpit 
display.

Sid Knox
Oklahoma

Velocity  173 RG  N199RS
Starduster  N666SK
KR2         N24TC
W7QJQ


> From: "Hiroo Umeno" <humeno at microsoft.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Friday, February 16, 2007 4:35 PM
> Subject: Re: REFLECTOR: How to protect the battery bus


> The shunt drives the ammeter.  In my case, even under the best of 
> circumstances, the first
> rotation after the starter engages is painfully slow.  It usually takes 
> about 2 seconds for the
> starter to get past the first compression stroke of the Franklin engine, 
> then after that, it cranks fine.

> Last time, I held my finger on a bit too long hoping that the weakened 
> battery can
> still overcome the compression stroke ending up in a blown shunt.

> Hiroo