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Z-12 Twist?

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thorn(at)starflight.aero
Guest

Posted: Mon Apr 12, 2010 12:50 pm Post subject: Z-12 Twist?

[quote]

Bob,   

After a lot of business travel Iâ€™m getting back to our airplaneâ€™s electrical system design.  As a reminder, weâ€™re building a Lancair Legacy â€“ a small very weight sensitive airplane (explaining why weâ€™re not going with dual alt dual batt).  We have the engine (IO-550N) and it has a big 100A alternator (all electric air conditioning) and B&Câ€™s little 20A alternator on a vacuum pump pad.  Weâ€™re planning on your Z-12 power architecture â€“ but, first Iâ€™d like to explore a variation.   

As you know, in your Z-12 with the SB1B voltage regulator, the auxiliary alternator does not come online unless the main alternator is overloaded or off.  It would be nice to have the 20A alternator contribute to the electrical power generation during normal operation.  Could I use two normal B&C voltage regulators (LR3Cs) with the 20A alternator voltage regulator set at 28V while the voltage regulator for the 100A alternator is set at 26V so that the first 20 Amps of load are handled by the little Alt and the big Alt gets the rest of the load?  Would there be any instabilities between the two voltage regulators?      

I like that in the worst load conditions â€“ like taxiing out on a hot day with the electric A/C on â€“ that the big Alt would be 20A lower and cooler, maybe extending it's life.   



  

What do you think?   

Thanks,   

Valin Thorn 



  

Lancair Legacy Project

 



[b]

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edleg

Joined: 11 Jun 2009
Posts: 14

Posted: Tue Apr 13, 2010 6:42 am Post subject: Re: Z-12 Twist?

Your kidding,... right? A "very small, weight sensitive" airplane with a 550 engine, air conditioning, all electric....



jeeshh

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 13, 2010 7:14 am Post subject: Z-12 Twist?

At 03:39 PM 4/12/2010, you wrote:



Bob,



After a lot of business travel Iâ€™m getting back 

to our airplaneâ€™s electrical system design.  As 

a reminder, weâ€™re building a Lancair Legacy – a 

small very weight sensitive airplane (explaining 

why weâ€™re not going with dual alt dual 

batt).  We have the engine (IO-550N) and it has a 

big 100A alternator (all electric air 

conditioning) and B&Câ€™s little 20A alternator 

on a vacuum pump pad.  Weâ€™re planning on your 

Z-12 power architecture – but, first Iâ€™d like to explore a variation.



As you know, in your Z-12 with the SB1B voltage 

regulator, the auxiliary alternator does not come 

online unless the main alternator is overloaded 

or off.  It would be nice to have the 20A 

alternator contribute to the electrical power 

generation during normal operation.  Could I use 

two normal B&C voltage regulators (LR3Cs) with 

the 20A alternator voltage regulator set at 28V 

while the voltage regulator for the 100A 

alternator is set at 26V so that the first 20 

Amps of load are handled by the little Alt and 

the big Alt gets the rest of the load?  Would 

there be any instabilities between the two voltage regulators?



    You could use two LR3 as you suggest but the SD-20

    driven from the vacuum pump pad is not capable

    of significant output during taxi operations.

    This is why it's a "standby" alternator as opposed to

    an "auxiliary"  alternator. It's capable of rated

    performance only in flight.



    Bob . . .

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longg(at)pjm.com
Guest

Posted: Tue Apr 13, 2010 8:24 am Post subject: Z-12 Twist?

Wow,



The Legacy is already CG sensitive with the big motor, then you install

the air-conditioning stuff which moves the CG aft and you've stopped the

big guys from sweating so they're no longer losing weight which makes

the plane more sensitive to gross weight when you fill up the 32.5 gal

fuel tanks. Now, you either need more power or you need to buy a 40 amp

alternator to save 4 pounds so you can carry a change of clothes for the

weekend. To save more weight I'd install the SD-8 and when #1 goes

south, shut down the air-conditioning, turn out all the lights and run

home on a 1 amp Dynon. When the 100 amp job goes you'll be sweating

bullets anyway so the air-conditioning will simply become camping gear

at that point.



That said, I really do enjoy the Legacy.



--

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Valin

Joined: 13 Apr 2010
Posts: 31
Location: Colorado

Posted: Tue Apr 13, 2010 5:11 pm Post subject: Z-12 Twist?

Ed,  

   

Yea, the Lancair Legacy is certainly not a Piper Cub.  The weight sensitivity I’m talking about is because the Legacy was designed for a 1500 lb empty weight -- but most people’s airplanes come in around 1650 lbs and some even approach 1800 lbs.    

   

Also, I live in hot, humid, Houston so have added 40 lbs for an air conditioner.   I have made the A/C unit easily removable, though, for winters or when payload is more important than comfort.   I’m looking to make up the weight in other areas.  Adding a second battery of around 8 AHr adds about 15 lbs  more.  I took about 17 lbs out with an MT propeller vs. the Hartzell.  

   

Valin  

   

   

--> AeroElectric-List message posted by: "edleg" <ed_legault(at)yahoo.com>  

   

Your kidding,... right? A "very small, weight sensitive" airplane with a 550 engine, air conditioning, all electric....  

   

jeeshh  

   

 [Rolling Eyes]  

   

        [quote][b]

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Valin

Joined: 13 Apr 2010
Posts: 31
Location: Colorado

Posted: Tue Apr 13, 2010 5:24 pm Post subject: Z-12 Twist?

Okay, so I shouldn’t have to worry about an instability with the two controllers as long as there’s enough difference in their voltage set points…  Good point that the SD-20 only makes rated power at cruise rpms.    

   

Does anyone know of an “auxiliary alternator” candidate that will fit on an IO-550’s vacuum pump pad that has a 1.5 turn ratio to the crankshaft?  

   

Thanks,  

   

Valin  

   

   

   

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>  

   

    You could use two LR3 as you suggest but the SD-20  

    driven from the vacuum pump pad is not capable  

    of significant output during taxi operations.  

    This is why it's a "standby" alternator as opposed to  

    an "auxiliary"  alternator. It's capable of rated  

    performance only in flight.  

   

    Bob . . .  

   

   

        [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 13, 2010 8:33 pm Post subject: Z-12 Twist?

At 08:13 PM 4/13/2010, you wrote:

 	  Quote: 	
		  Okay, so I shouldn’t have to worry about an 

instability with the two controllers as long as 

there’s enough difference in their voltage set 

points…  Good point that the SD-20 only makes rated power at cruise rpms.



Does anyone know of an “auxiliary alternator” 

candidate that will fit on an IO-550’s vacuum 

pump pad that has a 1.5 turn ratio to the crankshaft?


	


   The problem is drive speed. Most alternators with

   automotive pedigrees have a 4000 rpm for full output

   with maximum efficiency at about 6000 rpm. George

   Braly has another AND2000 pad driven alternator

   and claims 30A max output . . . but that too will

   be at cruise RPM . . . and I think he gets there by

   over-exciting the field by several volts.



   Bob . . .

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Valin

Joined: 13 Apr 2010
Posts: 31
Location: Colorado

Posted: Thu Apr 15, 2010 11:00 pm Post subject: Z-12 Twist?

Hi Longg,  

   

Yes, our Legacy’s weight and c.g. location are one of my focus areas of concern.  Houston is just too hot and humid to not have an A/C in an airplane like the Legacy with a bubble canopy.  I figure half our flights will be local, low altitude with no relief from the temps with altitude.  To make up for the 40 lb A/C unit behind the seats, I’ve saved 17 lbs with an MT propeller vs. the Hartzell.  Of course, that weight behind the seats hurts the aft c.g. tendency of the basic design.  So the batteries (30 lbs) are going on the firewall.  Also, we plan on a G900X integrated avionics system which is going to hurt weight but help move the c.g. forward.  Also, the A/C unit is easily removable for winter months or when the payload capability is needed.  

   

On the electrical configuration, I subscribe to the design goal that the failure of an alternator in flight should not prevent comfortably continuing on to your destination – at least VFR.  I do have a Dynon PFD planned as a backup.  With the SD-20, though, I can cover the G900X system with Wx Link and Traffic Awareness systems off.  

   

Valin  

   

   

--

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