Page 1 of 2

gl1000 - alternator rpm ?

Posted: Sun Sep 19, 2021 6:23 pm
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.

Re: gl1000 - alternator rpm ?

Posted: Sun Sep 19, 2021 10:04 pm
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.

Re: gl1000 - alternator rpm ?

Posted: Sun Sep 19, 2021 10:26 pm
by CYBORG
Curious ...... Why do you want to know?

Re: gl1000 - alternator rpm ?

Posted: Mon Sep 20, 2021 11:13 am
by dontwantapickle
CYBORG wrote: Sun Sep 19, 2021 10:26 pm Curious ...... Why do you want to know?
Like you.... I'm just curious.
crossy.gif

Re: gl1000 - alternator rpm ?

Posted: Sun Aug 13, 2023 5:30 pm
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
79 ratio.jpg (135.83 KiB) Viewed 536 times

Re: gl1000 - alternator rpm ?

Posted: Sun Aug 13, 2023 7:00 pm
by Whiskerfish
action1 action1 action1

Re: gl1000 - alternator rpm ?

Posted: Mon Aug 14, 2023 7:21 am
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.

Re: gl1000 - alternator rpm ?

Posted: Mon Aug 14, 2023 8:04 am
by Shadowjack
It rotates backwards as well so it offsets the torque effect.

Re: gl1000 - alternator rpm ?

Posted: Mon Aug 14, 2023 12:55 pm
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.

Re: gl1000 - alternator rpm ?

Posted: Mon Aug 14, 2023 8:36 pm
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.

Re: gl1000 - alternator rpm ?

Posted: Mon Aug 14, 2023 9:21 pm
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.

Re: gl1000 - alternator rpm ?

Posted: Thu Aug 17, 2023 9:31 am
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.

Re: gl1000 - alternator rpm ?

Posted: Fri Aug 18, 2023 7:38 am
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.

Re: gl1000 - alternator rpm ?

Posted: Fri Aug 18, 2023 8:26 am
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.

Re: gl1000 - alternator rpm ?

Posted: Fri Aug 18, 2023 10:10 am
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.