gl1000 - alternator rpm ?

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dontwantapickle
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gl1000 - alternator rpm ?

#1

Post by dontwantapickle »

Does anybody know if the alternator rotor spins at a 1:1 ratio with the crank?
I don't even know where to begin to look that up.
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Re: gl1000 - alternator rpm ?

#2

Post by pidjones »

Shouldn't be all that hard to put a wrench on the alternator bolt and watch the point cam (1/2 turn/rev) or pull a plug and put a straw in the hole.
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Re: gl1000 - alternator rpm ?

#3

Post by CYBORG »

Curious ...... Why do you want to know?
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Re: gl1000 - alternator rpm ?

#4

Post by dontwantapickle »

CYBORG wrote: Sun Sep 19, 2021 10:26 pm Curious ...... Why do you want to know?
Like you.... I'm just curious.
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Re: gl1000 - alternator rpm ?

#5

Post by dontwantapickle »

Old Thread...
As I start putting another 1979 GL1000 engine back together,
This time I remembered to check the speed ratio between the crankshaft and the alternator and answered my own question.
Just for reference and posterity, here are my findings.

41/36 gears equals a driven ratio of 1.1389:1
7500 crankshaft rpm = 8542 alternator rotor rpm.

SO... if anyone is ever curious, The alternator DOES spin faster than the engine.
79 ratio.jpg
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Re: gl1000 - alternator rpm ?

#6

Post by Whiskerfish »

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Re: gl1000 - alternator rpm ?

#7

Post by redglbx »

Thanks Don ! I know on a car/truck under-driving the accessories can generally give you a free 10-20hp but It probably can’t be done on the GL.
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Re: gl1000 - alternator rpm ?

#8

Post by Shadowjack »

It rotates backwards as well so it offsets the torque effect.
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Re: gl1000 - alternator rpm ?

#9

Post by dontwantapickle »

^ I know that it sounds logical, but I have never found evidence to support this idea.

All of the flat 4 engines that I have ever dealt with have no counter balancers (Wing, VW, Subaru, Porsche, Lycoming).
The opposed cylinders cancel each other out, self balancing.

I assume that the GoldWing alternators spin counter to the crank because that was the best way to build the engines.

I should be able to test this theory soon as I'm going to be building another racing engine after I finish this one.
The plan is to remove the whole charging system, electric start, etc. to take strain off of the crank and free up some HP.
I'll be able to tell if there actually is a torque effect as soon as I fire it up.
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Re: gl1000 - alternator rpm ?

#10

Post by redglbx »

Don, I think the “torque” effect is real, maybe. I had a friend years ago that was big into BMW’s and when he’d get into it the torque effect would have it cranked over very noticeably but,,,, that was a twin not a four.

Although he & his brother were putting VW engines into BMW chassis years before there were Goldwings, one with a 2400cc fi VW engine they built was a real monster and would definitely torque over. Does it cause problems ? Not that I ever seen once you got used to it.

They (GL’s) do Jack up & down a lot due to the pinion trying to climb the ring gear…. Is it a problem ? Not that I’ve noticed ,,,, but I’ve found that trying to do the racer boy thing in the corners means you go in slow and add throttle in the corner to give the most clearance, never want to chop the throttle mid corner to prevent bottoming…..

But that’s all different from what you’re trying to do. If I can maybe answer any questions for you just ask ! Top end racing is something that I’ve always wanted to do but time has marched past for me.
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Re: gl1000 - alternator rpm ?

#11

Post by dontwantapickle »

I think the effects of the alternator counter rotating on a GL1000 engine would be minimal at best.
that's why I think it would be interesting to try it both with and without.
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Re: gl1000 - alternator rpm ?

#12

Post by Sidecar Bob »

Sit on the bike with your feet on the ground, holding the handlebars loosely, engine idling and transmission in neutral and rev the engine suddenly and you will feel the torque reaction trying to rock the bike sideways.
As I understand things the effect would be greater if the alternator's flywheel mass was rotating in the same direction as the engine.

Note that CX/GL500/650 bikes have about the same amount of torque reaction as a GL1000/1100 from a much smaller engine but they have the alternator rotor/flywheel mounted directly on the crankshaft.
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Re: gl1000 - alternator rpm ?

#13

Post by redglbx »

The older BMW’s I got to play with many years ago had significant torque rock when blipping the throttle, most were 600 cc’s . Don’t know about the new boxers.
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Re: gl1000 - alternator rpm ?

#14

Post by CYBORG »

I agree with the older BMW's. And my Goldwings also have torgue when the throttle is twisted.....but al both cases only really noticable when sitting still. Off set by the rotation of the wheels when in motion. Under excelleration, not noticable.
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Re: gl1000 - alternator rpm ?

#15

Post by Sagebrush »

Torque effect and balancing are two different things. If you really want to feel the torque effect ride down a straight level road with no hands on the handlebars, every Goldwing I've ever owned will stray to the left. Quite noticeable. Any V-twin I've tried that on will carry on straight because the torque is in line with the front-rear axis. Bobs technique might be a safer method of testing the torque effect though.
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