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10-12-2019, 04:51 PM
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Join Date: Sep 2019
Location: Ionia Michigan
Posts: 160
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I've been running a Honda alternator with external regulator on my RV6, I installed it in 1997 and haven't had a problem with it. I live in Michigan so it isn't around any extreme heat very often.
__________________
RV6 N7219d
IO-320-B1A
Sam James cowl
first flight May 2, 1997
RV8 #83830 tail done, wing done
Fuselage started
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10-12-2019, 05:17 PM
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Join Date: Oct 2019
Location: SoCal
Posts: 318
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Do you really need a larger diameter pulley on the alternator?
Car engines can run more twice the rpm of an aircraft engine.
__________________
Ed
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10-12-2019, 06:05 PM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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Quote:
Originally Posted by emsvitil
Do you really need a larger diameter pulley on the alternator?
Car engines can run more twice the rpm of an aircraft engine.
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Need?? If your alternator works with the small pulley you don't "need" a larger one. However, your alternator will last longer with a larger pulley. I knew it would not take long for someone to ask your question.
While modern auto engines have redlines of 5,500 to 7,500 RPM, those engines only visit those speeds for mere seconds at a time. The average V-8 powered car only turns about 2,200 RPMs to do 70 MPH in top gear. It's doing so with a crankshaft pulley of about 6" diameter.
Asian 4 cylinder engines might turn 3,000 RPM at the same speed, but have 4.5" diameter crankshaft pulleys. Your Lycoming is going to run 2,400 to 2,500 RPMs for most of it's life.
Cars use small alternator pulleys due to the high electrical loads placed on them during low RPM operations. A car up north during the winter is running the heated rear glass [20 - 30 amps], the heater [4 -15 amps] lights at night [12 amps] ignition and fuel injection [12 amps] plus other items. Auto engines speed most of their lives at 700 to 1,800 RPMs.
Charlie
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10-13-2019, 10:53 AM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by emsvitil
Do you really need a larger diameter pulley on the alternator?
Car engines can run more twice the rpm of an aircraft engine.
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The Plane Power has a 2.75" pulley & runs 9570RPM @ 2700 engine RPM. The bearings/grease are rated for 15,000.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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10-13-2019, 12:13 PM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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Quote:
Originally Posted by BillL
The Plane Power has a 2.75" pulley & runs 9570RPM @ 2700 engine RPM. The bearings/grease are rated for 15,000.
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I would imagine that plane power uses higher quality bearings and parts than your average budget rebuilt. The engine pulley on most of the 4-cylinder Lycoming engines that we use is 9.75" in diameter. That's quite a bit bigger than your average car engine crankshaft pulley. Most of the Nippon Denso alternators converted for use on our engines use a 2.5 inch diameter pulley. That gives 10,530 alternator RPM at 2700 RPM.
Charlie
Last edited by chaskuss : 10-14-2019 at 08:15 AM.
Reason: clarified what is turning 10,530 RPM
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10-13-2019, 02:36 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Most auto alternators reach full output at 6-7000 rotor rpm. No need to spin them any faster than this continuously. Some car stuff will reach 14,000 rpm at redline but needs to be that way to supply enough amps at idle for the high electrical loads they have. Highway cruise, 70-80 mph, they are seeing 5000-7000 rpm in most cases.
Bigger pulleys extend bearing and brush life on aircraft. If you have the cowling clearance, not a bad idea.
Last edited by rv6ejguy : 10-13-2019 at 03:02 PM.
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10-13-2019, 03:53 PM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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Quote:
Originally Posted by rv6ejguy
snipped Highway cruise, 70-80 mph, they are seeing 5000-7000 rpm in most cases.
Bigger pulleys extend bearing and brush life on aircraft. If you have the cowling clearance, not a bad idea.
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Ross just to clarify, you're 5000 to 7000 RPM quote above is referring to alternator RPM correct?
Charlie
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10-13-2019, 08:32 PM
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Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966
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Quote:
Originally Posted by chaskuss
David,
What model ND alternator [or what year/model car] failed on you? One thing I forgot to mention on the last 2 posts. The 1995 Dodge ND alternator has a serpentine belt, rather than the OP's requested Vee belt pulley. Vee belts were phased out by the late 1980s on cars. So basically you can buy an alternator for an early 1980s car, with the right pulley & an external regulator. It will be hard to find a replacement alternator on short notice, as few of these cars are still on the road. Your other choice is a newer, more modern ND alternator, most of which are internally regulated and which all have pulleys for a serpentine belt. The mid 1990s to early 2000s Dodge trucks offer an alternator that stores still stock and has an external voltage regulator [it's built into the truck's engine computer aka PCM].
Changing the pulley is a 2 to 3 minute job, if you have a 1/2" impact gun [pneumatic or electric] to remove the mounting nut. It has been recommended on past threads to install a 4" diameter Vee belt pulley, rather than the 2 - 2.5" Vee belt pulleys that came on the old models. The advantage of the larger pulley is that it compensates for the added alternator RPM due to the large pulley on the Lycoming flywheel. Most car engines have crankshaft pulleys of 5"- 6.5" diameter. Going from memory, I believe our Lycoming pulleys are around 9.75" in diameter. [I don't have the reference materials on this computer to look that spec up.] Using the smaller alternator pulleys with a Lycoming ensures that the alternator spins much faster than it does on a car. That extra speed helps charging while you taxi, but wears your bearing & brushes out faster in cruise and climb flight. The larger diameter Vee belt pulleys are available at automotive hot-rod shops. For ND or ND clone alternators, you need a pulley with a 15mm hole for the shaft. The downside of the larger pulley, is possible cowl clearance issues, depending on where you mount the alternator. The clearance issue is more common on the tightly cowled RV 3s & 4s.
Charlie
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The one for a 1987 Suzuki Samaria is what I used. Even had a blast tube on the built in regulator to keep it cool.
__________________
David C.
Howell, MI
RV-10: #41686 Under Construction
RV-9A: #90949 Under Construction
RV-10: #40637 Completed/Sold 2016
Cozy MKIV:#656 Completed/Sold 2007
"Donor Exempt" but donated through Dec. 2020
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10-13-2019, 09:20 PM
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Join Date: Sep 2019
Location: Edmonds, WA
Posts: 105
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Where do you get a 4" alternator pulley?
I was just thinking of turning my own, maybe out of titanium 
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10-13-2019, 11:56 PM
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Join Date: Jun 2014
Location: Sherwood Park, Alberta
Posts: 77
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__________________
Phil Kite
F4 Raider project with RV-8 wings and tail
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