Heavy flywheel equals more torque? (2014)

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john robert bould said:
Last Monday [yesterday] i watched Duncans Manx out pull the G50 of Mike Edwards from a standing start, but exiting corners the G50 had the edge...and watching the G50's taco on Mikes you tube blog, the G as quicker responce above 7000 ...Duncan recons the manx as the heavest flywheels which give it that extra whoomp from a stand still.

I thought it would be the other way around - lighter fly wheel = less inertia = quicker acceleration. Heavy flywheel = more inertia = slower acceleration but greater momentum when up to speed.
 
You forget on the start grid the Manx is reved up, which stores more energy that lighter ones...but watch the Mike Spike Edwards blog.
 
Never lose sight that engine torque ALL ultimately comes from how strong the fire in the boiler is.
That ole BMEP again = BHP.
Remember, torque happens all through the rev range, right from idle, not just some numbers on a brochure.
Flywheels and wheels and what is attached are only as fast as what drives them. !!

We'd have hoped folks would have twigged to this by now here....

Remember too that flywheels don't have some inexhaustable fund of energy,
They get it replentished every 2nd rev. (on a 4 stroke single).
Depending on how hard you are twisting the throttle....
 
Duh, dudes for the size and speed of our range of flywheel mass it can't store much more excess energy than to spin tire some on up shifts, aka catching rubber. For sure any extra mass energy stored that can fit in the crank case will not last though 1st gear run up, then its all fuel heat pressure burn after that. Almost all mc flywheels have enough mass to pop a standing wheelie like a mini bike or small scooters but not enough to carry the wheelie beyond that alone. How more flywheel helps going around corners in Norton road racers I don't know.
 
Right, But if you have a 2lb fly wheel and i have a 50Lb fly wheel and we both are sat on the start line,,both reving to 7000 rpm...i could out gun you with my throttle closed!
untill the energy in my 50Lb flywheel is drained, Can you recall the Gyro Bus> it was powered up in the station..then traved about on stored energy...returning just before the gyro stopped,



Rohan said:
Never lose sight that engine torque ALL ultimately comes from how strong the fire in the boiler is.
That ole BMEP again = BHP.
Remember, torque happens all through the rev range, right from idle, not just some numbers on a brochure.
Flywheels and wheels and what is attached are only as fast as what drives them. !!

We'd have hoped folks would have twigged to this by now here....

Remember too that flywheels don't have some inexhaustable fund of energy,
They get it replentished every 2nd rev. (on a 4 stroke single).
Depending on how hard you are twisting the throttle....
 
What about if you are comparing 2 bikes with both about with a normal flywheel though ?
Flywheels run out of energy in a few revs or 3.
Then your example falls to dust...

Whoever pulls strongly out of the corners is the one with the strongest fire in the boiler.
Torque wins races, every time !!

You guys need to forget about flywheel effect, which is only a momentary transient passing..
Its the BMEP connected to the throttle and the back wheel that gives the GO POWER ....
 
Duh, with big enough flywheel you could wheelie the bus, for a time. I'm limiting my statements to the flywheel mass range that can fit in our crankcases. At some point I may put horizontal flywheel on Peel so deer, goats, dogs can't knock us over. If ya want to feel you flywheel energy release just rev up to some rpm then cut throttle as ya ease out of dump clutch in your gear of choice. Regardless ole Al is grinning a bit wider so don't matter what we think of his installing less of a hi end Steve Maney product.
 
Good luck with the Britti Rallly Simon, you deserve a bit after all the work you've put in to achieve it.
 
hobot said:
Duh, with big enough flywheel you could wheelie the bus, for a time.

With a big enough flywheel, you could spin the earth backwards.
But lets stick to real flywheels and real bikes, like you say...
 
hehe, and the 2lb vs 50 lb prior example is less out landish? I watched an old slow thumping Norton mount a passenger, set throttle pleasant bit above idle, let go of clutch to immediately run up to ~15 mph and ascend a steep grass slope a few stories high w/o seeming loosing any easy engine breathing rpm. Fascinating permanent memory of one value of heavy-ish flywheel. An't academic to me as definitely sense flywheel effects on ease to balance in poor traction sloped turns and engine pulse hook up on loose steep climbs with off sloped curve blending into a drop off. Also have to alter rpm fear compensation on down shifts among flywheel masses and gear ratios on brit vertical twin vs modern V-win. Must spin V-twin half again as fast to get more self balancing to slight slide shifts of tires on top of rolly polly stuff. Also depends on what a pilot likes, same as tire pressure, spring rates, how to hang off or not, whether to let it skip now and then or always avoid it or taking hi or lo line around. Stuff happens so abruptly on my P!! Cheetah, Peel in chicanes and most always hear someone's screams each time on THE shitty stuff plus with hi power fling or braking, I figure the lighter more jerking uppy downy the better.

For an innate sense of flywheel effect picture it turning a paddle wheel.
[video]https://www.youtube.com/watch?v=SMyMRST5inE[/video]
[video]https://www.youtube.com/watch?v=BZnNBvfaA_o[/video]
[video]https://www.youtube.com/watch?v=02DKzQFsgJU[/video]
I really want one of these Combat powered to lug behind Peel.
 
We agreed, 10 pages back, that a heavier flywheel smoothes out the torque pulses. ??

Its easy to come up with all sorts of unsuitable examples, but a suitable flywheel, within a range of limits, is a flywheel is a flywheel is a flywheel.
Don't forget that the rear wheel, the clutch and the transmission add inertia too.
So does the bike and rider, to an extent....
 
john robert bould said:
You forget on the start grid the Manx is reved up, which stores more energy that lighter ones...but watch the Mike Spike Edwards blog.

Good point.

Rohan said:
We agreed, 10 pages back, that a heavier flywheel smoothes out the torque pulses. ?? ....

I'm not disagreeing with you but even if the whole forum agreed on a theory it doesn't necessarily mean it is correct.

gripper said:
Good luck with the Britti Rallly Simon, you deserve a bit after all the work you've put in to achieve it.

Cheers Dave.
 
"what about if you are comparing........"
Thats not what this post is about...it's about a heavy fly wheel having more "turning power" than a lighter one... my extream example 2 lb -20 lb is only extream , but would prove that once the heavy wheel was wound up..it's simplys harder to stop..which must prove the fact....after all the heavy flywheel takes more energy to wind it up to start with,
Your other point regarding "flywheels run out of energy quickly is not quite correct...a high spinning crank shaft as great energy. capable of destroying your crank cases!

A disc of only 15 thou was spun to thousands of RPM... and weighed only a gram , but its energy was enough to destroy a row of house's! why?
You are correct..if the flywheels/drive train are the same weight...ITS THE BMEP that scores on the day.


Rohan said:
What about if you are comparing 2 bikes with both about with a normal flywheel though ?
Flywheels run out of energy in a few revs or 3.
Then your example falls to dust...

Whoever pulls strongly out of the corners is the one with the strongest fire in the boiler.
Torque wins races, every time !!

You guys need to forget about flywheel effect, which is only a momentary transient passing..
Its the BMEP connected to the throttle and the back wheel that gives the GO POWER ....
 
Rohan said:
We agreed, 10 pages back, that a heavier flywheel smoothes out the torque pulses. ?? ....
Al-otment said:
I'm not disagreeing with you but even if the whole forum agreed on a theory it doesn't necessarily mean it is correct.

When the discussion here agrees with the theory in the textbooks agrees with real world practice,
its looking like a good sure thing..... !
 
john robert bould said:
Your other point regarding "flywheels run out of energy quickly is not quite correct...a high spinning crank shaft as great energy. capable of destroying your crank cases!

Its all relative.
And a little off track...

Flywheels were not designed to be destroying crankcases (hopefully !!),
but to assist in the process of propelling bikes down the road...
 
When you say the flywheel smooths out the torque pulses, are you referring to the pulse which occurs every time a cylinder fires, or the pulse which is the sum total of the thousands of pulses , which occurs between every gear change ? The believe the flywheel in a commando engine is too heavy to be successfully used in anger with the standard gearbox. A race change with a close ratio gearbox behind a near standard motor is quite something.
 
When engine flywheel speed is monitored closely its seen to essentially instantly speed up with each power stroke and slow down on compression with lessor speed changes on the other strokes but it also helps keep engine spinning w/o any throttle for a while too, so both views apply. I prefer to control tire spin in or out of traction more by pure combustion than inertia. Its easier to ride smoother with heavier flywheel but then so are locomotives stuck on rails.
 
When you rev a Commando engine with the heavy crank to 7,500 RPM and do a race change up one gear, using a close ratio box with high overall gearing - that is probably as fast as a Commando is ever going to accelerate. The crank inertia overcomes the wind resistance.
 
When engine flywheel speed is monitored closely its seen to essentially instantly speed up with each power stroke and slow down on compression with lessor speed changes on the other strokes but it also helps keep engine spinning w/o any throttle for a while too, so both views apply. I prefer to control tire spin in or out of traction more by pure combustion than inertia. Its easier to ride smoother with heavier flywheel but then so are locomotives stuck on rails.

With the heavy crank and the standard gearbox, it is impossible to be smooth. Every down change requires a heap of revs and you have to wait to match the revs to get a smooth change.
 
When you rev a Commando engine with the heavy crank to 7,500 RPM and do a race change up one gear, using a close ratio box with high overall gearing - that is probably as fast as a Commando is ever going to accelerate. The crank inertia overcomes the wind resistance.
Blimey have you been revving up for 4 years waiting to post this??? Sorry acotrel I couldn't resist
 
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