Alternator

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Alternator

Postby Chillyride » Sun Sep 02, 2007 2:49 pm

Does anybody know about mounting an alternator on the tail rotor drive shaft u-joint up at the transmission? I have an old service bulliton that shows Hiller doing it with a generator. I have a 12C that I have been trying to get working right for some time. My last hurdle (I hope) is the charging system. I am planning to mount a Plane Power Alternator with a Zeftronics regulator. I was hoping that this had been done before and I wouldn't have to manufacture my own mount system. They also mounted superchargers up there in the past. Any ideas will be appreciated!

Chillyride
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Tail rotor pinion

Postby ted.stokes » Tue Sep 04, 2007 2:39 am

I'm not aware of an alternator mod but you need to check out Hiller Service Bulletin 84. It is used for the generator or supercharger modifications. It places a solid insert inside the tail rotor transmission pinion to support the added load and reduce spline wear.

Ted
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Postby Tim Tyler » Tue Sep 04, 2007 2:50 pm

Ted is right about the solid plug in the T/R output shaft. Additionally, the Hiller S/B shows a double belt pulley which was necessary to drive the Turbo but is more than is required to drive a generator. Unfortunately, the alternator installation is not approved by the FAA so you would need a one time field approval to make it legal.

I would recommend building the adaptor/attachment plate and utilizing the double pulley arrangement exactly as specified in Hiller S/B 84. The more approved data you can show the FAA the better your chances are of getting the field approval.

if you decide to go this route you will be able to eliminate the entire electrical junction box on the engine deck as the alternator will have it's own internal voltage regulator and associated reverse current sensing system.

I installed an alternator in this fashion and was able to remove over 10 lbs of associated equipment and (as a bonus improvement) the engine deck was a lot cleaner. Of course, this change required a whole new wiring harness from the engine deck cannon plug through out the entire engine and tail boom. I simply bought a new cannon plug and built a new wiring harness for it and carefully noted the changes to the wiring diagram as listed in the back of the Hiller Maintenance Manual.

Tim Tyler

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Alternator

Postby ted.stokes » Wed Sep 05, 2007 1:13 am

Tim,

Just curious, I have always wondered about the rpm loss in autorotation for accessories driven on the tail rotor pinion since you are attached to the rotor side of the sprag. What loss do you experience? What alternator are you using? Do you have some means of killing the voltage to the alternator rotor so you are only driving the internal friction during emergencies?

Ted
A&P IA
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Postby Hiller360 » Wed Sep 05, 2007 4:08 am

I've done a few alternator conversions by FAA field approvals,using both Delco and Motorola single wire 40 amp systems,we use the double sheeve pully with 1/2 inch belts for redundency. No noticable draw on an auto to affect rpm,and we've had from between 10 and 20 pound reduction in aircraft weight depending on the helicopter,and the best part is you never have to stand on your head taking out the generator again.We are currently working on making a set of prints for the brackets and may be interested in putting together a alternator "kit" if there was enough interest,it would still have to be installed on a FAA field Approval and 337 form, I went this way a few years ago approving a spin on oil filter kit and had guys bootlegging my paperwork and using JC Whitney adapters and car filters,that won't happen again,the FAA requires a letter of authorization from the IA on the previous 337 or they won't approve it.

Dave
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Alternator

Postby Chillyride » Thu Dec 27, 2007 3:49 am

To Tim and Ted, Thanks for responding to my question and sorry for the late reply. I appreciate both of your inputs, I do have the service bulletin in hand and will comply. I have a new plane power alternator and zeftronics regulator and have started building a mounting bracket. When I get this all sorted out I will let everyone know how it works. At the very least it will be easier to work on and lighter weight.
Chillyride
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