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Reply-To: "David Carter" <dcarter@datarecall.net>
From: "David Carter" <dcarter@datarecall.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Cc: "Ned Thomas" <923te@cox.net>
References: <list-558635@logan.com>
Subject: Re: [FlyRotary] Re: gear drive for distributor and oil metering pump
Date: Tue, 7 Dec 2004 16:59:23 -0600
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Output   Alternator  Alternator . . .  Regulator . . . . Regulator
Amps  . . . . P/N . . . . wt & cost . . . . P/N. . . . . . . . . .wt & cost
. . . Total cost & wt

. . 20  . . AM877557 . 1.81#, $145.49 . AM101406 . .  0.2# $66.56 . .
$212.05 & 2.01#

The above info is an extract from 1st line of a spreadsheet about John Deere
PM alternators.

On 2 Apr 2003, Ned Thomas reported:
"I went to the local John Deere dealer and bought the 20 amp PM alternator.
I then bought a 14 amp PM alternator that is used on the 3 cylinder diesel
Kubota engines.  It is 2 lbs lighter than the 20 amp and I think is adequate
for a backup alternator.  Fell free to give me a call to discuss further.
. . . Ned Thomas, 405-360-4298, Norman, OK, RV9A"

I just called Ned and we figure he meant 0.2 pounds difference.  He's going
out to his shop and recheck his notes or re-weigh the alternator.

So,  looks like we need to address the "design factors" for getting a PM
alternator to fit in the distributor (or oil metering pump) hole securely
with the Mazda gear on the end:
. . . 1)  Length of shaft of stock Mazda device vs the alternator shaft -
cut down if too long; extend with shaft extension with Woodruff key and/or
shrink fit or press fit.  Long term durability of such a 'joint' is biggest
need if have to extend the shaft.
. . . 2)  Diameter of shaft of stock Mazda device vs the alternator shaft -
if shaft is too large, can turn it down for proper fit into Mazda gear; if
too small, maybe can machine a spacer (collar?) for "press" or "shrink" fit
over end of alternator shaft, that will provide an OD to give an
appropriately tight fit into the Mazda gear.
. . . 3) Mount for alternator, so it fits centered in hole for distributor
or CAS and secured so it won't slide out, for example (not sure how the oil
pump drive gear & shaft are).  I don't have an engine so can't address this
part of the physical install.
. . . 4) Clearance of  mounted alternator - any interference with engine or
any other installed parts?

Ned, when you get this, will you measure the OD of the PM alternators (Deere
& Kubota) and send it to us on this list so we will have an idea if
interference is going to be a problem?

Also, Ned (or anyone else on this rotary list), did you get any size and wt
info from B&C on the SD-8 (8 amp PM alternator)?  I'm not sure 8 amps is
enough to run 1 EFI pump and ignition & fuel inj systems if lose main
alternator in flight.  If 8 amps was enough, then we ought to get size data
and run that alternative through the "design factors" above.
    -  My "electrical loads" spreadsheet has a "6 amp" entry for each of the
two efi pumps.  Didn't document brand name of pump and who gave the info.
Ken Powell says, "It takes a minimum of 13 amps to drive the fuel injection
and ignition system."
    -  Is that running both pumps for landing or just 1 pump "enroute"?
    -  I've never noticed anyone say what the current draw is for Tracy's
EC-2 and the 4 njectors it drives during cruise and at full power (in case
of go around during landing after alternator failure).  If only 2 injectors
are in use at normal cruise and only 1 pump is on, will the B&C SD-8 PM
alternator produce enough current at 1/2 of "engine cruise rpm of, say, 5400
rpm", i.e., at 2700 shaft rpm of SD-8?
    -  If the SD-8 was OK for cruise but not "landing", it would be OK to
let extra current needs be met by battery for the few minutes of approach
and landing - SD-8 doesn't have to be big enough for "all possible" loads
all the time.

David Carter
409-722-7259

----- Original Message ----- 
From: "Jim Sower" <canarder@frontiernet.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, December 06, 2004 11:30 PM
Subject: [FlyRotary] Re: gear drive for distributor and oil metering pump


> What about those little PM alternators that John Deere has on lots of
stuff?
>
>
> Ernest Christley wrote:
>
> > David Carter wrote:
> >
> >> Wonder if "we" could come up with an alternator to drop into that
hole -
> >> some back-up "juice" for our "electrically dependent engines".
> >>
> >> David
> >>
> >
> > That is exactly what I've been thinking, David.  Steve stopped by to
> > look at my project last week, and we were discussing it. Thanks to Mr.
> > Leonard over there, I now know what to look for.
> >
> > I need to find a 2/3HP or 500W or 30Amp generator/DC PM motor.  It'll
> > be 3" or 4" in diameter, with a couple inches of shaft sticking out.
> > I'm thinking it would be easy enough to key the shaft to fit as a
> > direct replacement for the metering pump.
> >
> > I don't have the numbers with me, but I was doodling with them a while
> > back.  I figured something like a couple of in.lb. of torque on the
> > worm gear to produce 500W at 6000RPM.  I now know the gear would turn
> > at half that, so it is still less that 5in.lb. on the gear.  The
> > upshot is that 3000RPM motors are much more abundant that 6000RPM
motors.
> >
> > I'm trying to source a part.  I'm also thinking that a standard
> > alternator can be made to fit by cutting down the housing.
> >
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>