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External Alternator for the Rotax

Dvalcik

Well Known Member
Sponsor
Adding the External Alternator has been an interesting modification for my RV12 - EAB. With all of the avionics I needed the extra power. After inspecting where the alternator would go, it was identified modifications to the mounting bracket, hose placement, cowling, and cooling shroud would need to be done. Basically the alternator sits on the pilot side and conflicts with the left intake for the scat hose to the cooling shroud .

Started the mods over the last few weekends,
1. Design a modification for the existing alternator bracket. Allowing for clearance with the upper cowl. The bracket is being finalized; we worked by tacking first for placement. I hope to every all install this weekend
2. Prop extension for the 3 blade Sensenich
3. The cowl is approximately ? in longer
4. Modify the cooling Shroud - Relocated the 90 degree intake off the shroud to the left side.
5. Modify the Cowl - Intake mod, cut off the inter lip on the lower cowl and moved it to the left intake.

These pictures are a few days old and are of the ruff fiberglass work. The nice thing is the left side intake will help keep the alternator cool.

I will post more pictures of the finished project once done. I need to thank the guys at KPTW; Al, Ned, Mark, Scott, Dick for their suggestions / help and Bill for fabricating of the mounting brackets

alt2.jpg
Cowl1.jpg

shroud1.jpg

shroud2.jpg
shroud3.jpg
 
Hi David,
Interesting.

I'm good with mine the way it is(No ext Alt), but have heard others desire for more juice.

Do you have a prediction for the effect on W&B?
 
Andy

Not sure on the W&B, I hope to have her on the scales in about 45 days after paint. Sensenich states the 3 blade wt is less then the 2 blade, but the small increase in weight for the alternator will have an effect, just how much???

I need the power for my panel design

2 GRT's Garmin 796, sl30, 327 and a Navworx ADS-b

rv-12_panel.jpg
 
This is going to be a great thread!

Did you consider an external alternator driven from the accessory pad on the back of the gearbox? Like this 20amp $700 example?
http://www.aircraftspruce.com/catalog/eppages/sd20_alternator.php
(I have NO IDEA if it would actually "fit" given the other stuff on the top of the engine.)


++++++++++++++++
For reference purposes:
Regarding the new Rotax fuel-injected engine electrical system - this is from the ROTAX manual on it.

QUOTE
Two alternators are built into the stator.
Alternator A is only used for electronic engine components (ignition, injection, and sensors).
Alternator B is used primarily to start the engine and charge the aircraft battery.

While the engine is running, Alternator B can be used for the on-board instruments.
Alternator A 14V/16A (220 watts nominal)
Alternator B 14V/30A (420 watts nominal)
If Alternator A fails, Alternator B takes over its functions. This means that the bettery will no longer be charged and no voltage will be available for the on-board instruments.
UNQUOTE

Besides these an optional external alternator is also available:
"600 watts DC at 6000 rpm"
"14.2 V to 14.8 V"
"6.61 lbs"
It appears to be about 40 amps at 4000 engine rpm.

Note that the engine has TWO electric-driven fuel pumps.
These are listed as "optional" and are listed as 10 amps each (in one place) but 10 amps total (in another place). Confusing.
And, they supply at 65 psi. This optional assembly is recommended to be installed under the fuel tank, with an upstream filter and water trap.
+++++++++++++++++++
 
Bill

I already had the Rotax 912 and removed it from my old SportHornet ELSA. The Rotax has 135 hours and had the external Alternator. I did look into the one you asked about, but more investment and the one I have is turning out to be a good solution with the mods.

We are talking to Rotax regarding which direction to hook up the two alternators. The original setup had both charging with switch circuit breakers on each. Still researching!

Open for suggestions?
 
spare Alternator

This is going to be a great thread!

Did you consider an external alternator driven from the accessory pad on the back of the gearbox? Like this 20amp $700 example?
http://www.aircraftspruce.com/catalog/eppages/sd20_alternator.php
(I have NO IDEA if it would actually "fit" given the other stuff on the top of the engine.)


++++++++++++++++
For reference purposes:
Regarding the new Rotax fuel-injected engine electrical system - this is from the ROTAX manual on it.

QUOTE
Two alternators are built into the stator.
Alternator A is only used for electronic engine components (ignition, injection, and sensors).
Alternator B is used primarily to start the engine and charge the aircraft battery.

While the engine is running, Alternator B can be used for the on-board instruments.
Alternator A 14V/16A (220 watts nominal)
Alternator B 14V/30A (420 watts nominal)
If Alternator A fails, Alternator B takes over its functions. This means that the bettery will no longer be charged and no voltage will be available for the on-board instruments.
UNQUOTE

Besides these an optional external alternator is also available:
"600 watts DC at 6000 rpm"
"14.2 V to 14.8 V"
"6.61 lbs"
It appears to be about 40 amps at 4000 engine rpm.

Note that the engine has TWO electric-driven fuel pumps.
These are listed as "optional" and are listed as 10 amps each (in one place) but 10 amps total (in another place). Confusing.
And, they supply at 65 psi. This optional assembly is recommended to be installed under the fuel tank, with an upstream filter and water trap.
+++++++++++++++++++[/QUOTE
Somewhere in this forum on MUCH earlier postings there is a picture of a Rotax 912 with an Alternator fitted to the accessory pad .... do a search to find it!
 
Update on the progress

A few new pictures from this weekend. Tried the bracket for fit and final welding.

alt5.jpg
alt6.jpg

alt7.jpg
 
Additional Power for Electroincs & Lighting

Any recent updates on how to get more power to run additional electronics, and lighting.
 
This is going to be a great thread!

Did you consider an external alternator driven from the accessory pad on the back of the gearbox? Like this 20amp $700 example?
http://www.aircraftspruce.com/catalog/eppages/sd20_alternator.php
(I have NO IDEA if it would actually "fit" given the other stuff on the top of the engine.)
...

Somewhere in this forum on MUCH earlier postings there is a picture of a Rotax 912 with an Alternator fitted to the accessory pad .... do a search to find it!

I've able to find two threads on this and not much detail. I'd love it if there was something else I'm missing...

http://www.vansairforce.com/community/showthread.php?t=80077
http://www.vansairforce.com/community/showthread.php?t=42959&highlight=altenator

Bob
 
Looks Good

David - looks good to me - should eliminate any concern about 'brown outs', etc. I'll be following your work on this and hope that it is all that you hope for. Will you isolate the power from this alt. or will you tie it directly into the main power buss? Please continue to post on this most interesting modification. Do you know how many hp this alternator will use?
 
David - looks good to me - should eliminate any concern about 'brown outs', etc. I'll be following your work on this and hope that it is all that you hope for. Will you isolate the power from this alt. or will you tie it directly into the main power buss? Please continue to post on this most interesting modification. Do you know how many hp this alternator will use?

I installed a Vertical Power (VPX) and isolated the Gen and the Alternator. The VPX starts up with the Alternator as the main and the Rotax Gen is off. Should I have a failure of the Alternator I will get a warning on my GRT via the VPX and switch the Alt off and the Gen on through the VPX. I would also shut down avionics so I don?t draw too much from the Rotax Gen ie.. Second GRT, ADSB, the Garmin 796 (to Battery) and others as needed.

No idea for the HP question.
 
Any updates on this? A larger power budget would be great! How did the weight and balance work out?

Thanks,

Bob
 
Has anyone tried the EPApower Gen2 alternator on a RV12. It seems like a possible solution adding 26 amps. I don't know if it would interfere with the engine mount. Below is a discription from their web site.


Independent, Supplementary and Backup Electrical Power
Gen2 is an independent alternator with its own regulator, providing supplementary electrical power, and also functioning as a backup to the ROTAX alternator.
The Gen2 does not require an external mount. It takes no space under the cowling and is crankshaft driven just like the existing 18-Amp ROTAX alternator. Gen2 bolts to the aft end of the engine and adds 26 Amps of reliable power, for a combined output of 44 Amps.
 
Has anyone tried the EPApower Gen2 alternator on a RV12. It seems like a possible solution adding 26 amps. I don't know if it would interfere with the engine mount. Below is a discription from their web site.


Independent, Supplementary and Backup Electrical Power
Gen2 is an independent alternator with its own regulator, providing supplementary electrical power, and also functioning as a backup to the ROTAX alternator.
The Gen2 does not require an external mount. It takes no space under the cowling and is crankshaft driven just like the existing 18-Amp ROTAX alternator. Gen2 bolts to the aft end of the engine and adds 26 Amps of reliable power, for a combined output of 44 Amps.

I must be searching wrong, I'd like to find out more about this, but just don't see it. Do you have a link?

Thanks,

bob
 
That's a lot of money for an alternator! But then you are eliminating a lot of cowling work and probably other issues in the process from mounting on the prop hub. The weight and balance would probably be easier to deal with closer to the firewall and you'd end up with 44 amps total.

For someone that has all the options including dual screens, ADSB, etc. and is thinking about going an IFR panel this might be worth it. Although how long will it be before someone else comes up with a less expensive model?

Bob
 
That would be nice for a post pink slip install...When I'd be able to install the radio/GPS for IFR.

Bob
 
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