Today's Message Index:
----------------------
1. 05:36 PM - Re: Re: AMPS? (Noel Loveys)
2. 07:09 PM - Re: Re: AMPS? (Noel Loveys)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
Barry:
There are a few reasons why I wouldn't use a ground power connector. First
is there are no brakes on a float plane. It would work great if I had
someone else to remove the connector after starting the engine. Tying the
tail is with a slip knot is an option but then I would still have to have
the engine running with no one in the cockpit... not the best idea.
Finally is of course the possibility of damaging the ground battery pack if
the connector happened to fall in the drink.
Wheel planes are another quintal of fish! There are chocks to hold them in
place and usually a few people to remove the connector and of course it
gives you plenty of power for those cold morning starts without having to
worry about carrying the batteries aloft.
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of FLYaDIVE
Sent: October 3, 2010 2:56 PM
Subject: Re: RotaxEngines-List: Re: AMPS?
Hello Noel:
I really like your idea of a Ground Power Connector, they offer all sorts of
advantages.
How does being on floats negate the Ground Power Connector?
As you know and mentioned, wire run length is a major factor. An AWG of 2
should do well for short runs of wire and that #2 does have a safety margin
figured in. Going to an AWG of 0 for BOTH POSITIVE & NEGATIVE runs should
work VERY well.
I have never use it - But, there have been many reports of using 'welder's
cable', very flexible, abrasion resistance, low resistance and available at
welding supply houses. They also have the ring lugs.
AND - Gaggle - I know I posted this before but it REALLY is a GREAT TRICK:
SOLDER the wire to the ring lug ONLY at the end next to the mounting part of
the ring lug.
Crimp First - Then older. Clean well.
Barry
On Fri, Oct 1, 2010 at 7:40 PM, Noel Loveys <noelloveys@yahoo.ca> wrote:
Barry:
If I read you right you like myself feel the 6Ga. feed wire is a bit on the
light side. I agree if someone was to try to push 100 A through that wire
it wouldn't be long before it would heat up and cause even greater
resistance.
What would you think an acceptable gauge for the starter feed wire to be?
2Ga. ground straps were mentioned.
I'm almost ready to install the battery in my 912 mod. I think I'll have to
put the battery behind the seats and that means around an 8' run. I'm
seriously considering 0Ga or 00Ga. wire. If I weren't on floats I'd install
a ground power connector.
Noel
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of FLYaDIVE
Sent: October 1, 2010 7:28 PM
Subject: Re: RotaxEngines-List: Re: AMPS?
Ron & Dan:
Here is the math for the information you gave:
0.6KW = 600 WATTS
600 WATTS @ 12 VDC (I use 12 V because you are pulling the power from the
Battery)
I (current) = 600 W / 12 VDC = 50 AMPS But at WHAT TEMP?
Lets also use 8 VDC... Why? Because many starters will turn over at a much
lower voltage than 12 VDC to insure starting when the battery is low and the
temp too. SOoooo...
I = 600 WATTS / 8 VDC = 75 AMPS But again at WHAT TEMP?
I have VERY STRONG reservations to where and how they came up with this
0.6KW.
It sounds way - way too low.
I'm betting that current (0.6KW) is a sustained current AFTER the initial
surge.
I doubt if they used a current probe connected to a digital O-Scope to
capture the true current draw. Having done amperage checks on small
lawnmowers, they were pulling 100 Amps on a SUMMER DAY.
Don't go borderline.
Barry
On Fri, Oct 1, 2010 at 3:38 PM, rparigoris <rparigor@suffolk.lib.ny.us>
wrote:
<rparigor@suffolk.lib.ny.us>
Hi Dan B.
The old style starter draws .6kW.
According to Lockwood, the new style starter draws less amps.
For a quick estimate using 60 amps for old style and 50 amps for new style
will get you very close to what is probably real draw. Remember this engine
is not too much over 70 cubic inches, not 200, 320, 360 or larger.
This info I gathered was based on a 914, but would imagine the 912S would be
very similar.
You can choose a larger resolution and look at starter on the right side:
http://www.europaowners.org/forums/gallery2.php?g2_itemId372
<http://www.europaowners.org/forums/gallery2.php?g2_itemId372&g2_imageVie
wsIndex=1> &g2_imageViewsIndex=1
Note if you run starter for 10 seconds, you should wait 2 minutes for cool
down.
I have a Odyssey PC525 mounted aft in fuse and am using #4 CCA. Others using
#4 have good success, but #2 wire would be a little better.
I think in your instance if #6 worked before, it will work better with the
HD starter.
The wire I am using is copper clad aluminium. The diameter is larger than #4
copper but the resistance is just about the same. I almost took the yellow
covering off the wire and stripped out strands to make it #5 to save a
little weight, then heat shrink Teflon heat shrink over the strands. Sounded
good, would have saved a little weight, then I realized just how much weight
it was going to save from my rear pocket and idea was put in the bin.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=314349#314349
==========
-List" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
==========
http://forums.matronics.com
==========
le, List Admin.
="_blank">http://www.matronics.com/contribution
==========
--
Barry
"Chop'd Liver"
http://www.matronics.com/Navigator?RotaxEngines-List
http://forums.matronics.com
http://www.matronics.com/contribution
ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
--
Barry
"Chop'd Liver"
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
I'm not trying to be cute here but I do have to ask what are high
performance moder electrics? Do you mean modular or motor?
I'm interested in your idea of running all loads for a few minutes before
trying to start a cold car. Problem with that as I see it and believe me
this far north I do see quite a bit of cold, is the battery itself doesn't
warm up in discharge but actually polarizes faster. (grows bubbles of
hydrogen on the plates lowering power.) In fact in really cold weather the
oil itself may thicken enough that you will have to make two tries a couple
of minutes apart just to get the crank to spin. Don't ask what current or
voltage drop the starter would demand on one of those occasions. Needless
to say starting any engine not pre heated is just another game of roulette.
BTW Changing gears on a really cold (older type) transmission also can be
lots of fun! The clutch will feel like a rock and you may need both hands
to get it in gear. You get used to driving the first twenty minutes in
first until things start to warm up a bit. I've also been cars where the
brake fluid got cold enough that stopping was interesting.. Sometimes I'd
have to waid five minutes for the brakes to release... thank god for disk
brakes!
My understanding of electric motors is they are dumber than Homer Simpson.
When designed to operate with a specific current, voltage and load they are
more than happy to do so. But if you increase the load they will literally
commit Hari Kari by drawing more and more current until they overheat and
burn out in an attempt to handle a too large load. My instruction was to
make sure the feed to the motor was sufficient to provide enough current
with a minimum of voltage drop for a design load. Basically that means that
you can't use too large feed wires. Planes unlike ships, boats, cars and
trucks have to be light enough to fly so weight and balance become paramount
in importance otherwise we would all be using 0000Ga cable and this thread
wouldn't be here. If I were to err on choosing a cable to handle a starter
motor I'd choose to have one size larger cable than what I think is actually
needed. That way my current resistance and voltage drop across the cable is
minimized for times when my battery may be a little weak or the oil may be a
little cool.
Noel
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of
rparigoris
Sent: October 3, 2010 6:31 PM
Subject: RotaxEngines-List: Re: AMPS?
<rparigor@suffolk.lib.ny.us>
Hi Barry
"It's true that to achieve the same watt output with a lower voltage you
need to up the amperage, in reality when you lower the voltage going to an
electric motor the amp draw drops."
If you have a battery or power supply with wires that can keep the lowering
of voltage and amperage to a minimum, then it's true that if you lower the
voltage to a motor that is reasonably loaded the amp draw will go up since
the motor can't spin as fast as if it had higher voltage (within reason as
far as voltage and load and motor timing).
What I was getting at is that often (VERY OFTEN with high performance moder
electrics) you may have a battery and wire size that is very close to asking
max. amps that the battery can offer while maintaining a reasonable voltage.
If you ask any more amps it will begin to give up a lot of voltage and not
offer up any more amps. If you have long thin wires that only drop voltage
further, then heat the wires up and drop voltage even further, often you are
asking more amps from the battery that it can put out. The scenario is the
battery is huffing and puffing harder and harder but begins dropping amp
output and voltage, and the wires are warming up and making things worst.
Net is if you see too little voltage at a running loaded motor (again within
reason and you calculated what you are looking for), it probably means you
have a battery that has not enough ability to dump amps and keep the voltage
up, and or the wires are creating too much resistance and dropping voltage.
In this scenario of marginal battery and wires, lets put it in the cold
where the battery is offering up even less performance and the motor is
offering up more resistance to turning and we measure a lower voltage going
to the motor, t!
he motor will just plain not be seeing very many amps going to it compared
to a warm battery and engine.
Again what really matters to me is when it's cold out I can start my bird.
BTW on cars it works where on a cold day if you turn on all loads for a few
minutes before starting the the warming up of the battery compared to the
watts used nets to more cranking power.
Also with electric motors timing is every bit as important as on IC motors.
You want to select proper advance for what you are doing. You never want to
run a brushed motor retarded from neutral. Amp draw will go way up and brush
life and power output way down. Select too much advance for a highly loaded
motor and if you can provide enough amps you will get a little more power
output, but often the battery/wires net to less power and you are better off
running closer to a neutral timing. I wouldn't be too surprised if someone
tried a few motors and optimized timing for our 91Xs to get the high output
version that draws less amps than the original. I wouldn't be too surprised
if the original motor wouldn't benefit a lot by optimized timing, but then
again it may not be too easy to adjust.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=314525#314525
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|