Variable Mass Flywheel

[Robot]

Anyone who knows me, knows "Physics" is my thing, anyway I once knew a guy who could beat anyone "off the line",(or so he said), he claimed it was the mass of his flywheel that did it, as he popped the clutch.

I saw a rebuild show on Speedchannel the other day, the guy put a new,(lighter), flywheel on a V-8. The lighter flywheel would allow the engine to rev "more quickly".

Each of these statements seem "reasonable" to me. Changing the "moment of inertia" would account for this.

My thought was why not have a "Variable Mass" flywheel. Vary the mass and moment of inertia for the specific engine need.

Of course someone already thought of it and pattented it:

United States Patent: 6915720

My guess is some of the racers here have altered flywheels, what was the "real world" result of you changing the flywheel?

P.S. The link above is the U.S. Patent office, if you search, you will most likely be amazed at what is patented.

 

[Commuta_Busa]

Depending on how much mass was removed and how much improvement is made to the MOI it will allow the engine to spin up faster. The down side has been during gear ingagement (letting out the clutch) it becomes more fikel to find the right amount of slip. Since there's less mass there's less stored energy which tends to drop the revs a little more.

I could go on alot about this but I think you know the whole physics much better than I could explain it all.

 

[Mr Bogus]

Inertia is a great thing...

We used a "weighted" flywheel on our dragster to store energy for the launch.. While other guys were going lighter (blower cars) we had to get some energy stored while we waited for the turbos to spool up.. The heavy flywheel gave us that inertia.. the turbos had the HP advantage to mostly make up for this "borrowed" energy..

 

[Robot]

Great real world examples, Thanks Guys I'm surprised an automaker isnt using this as a "gimmick" if not as a useful performance application.

 

[Mr Bogus]

Great real world examples, Thanks Guys I'm surprised an automaker isnt using this as a "gimmick" if not as a useful performance application.

the are in a way... the constant variable transmissions sort of play on this.. your old briggs mini bike had a flywheel that worked very similar.. (centrifugal clutch)

 

[Robot]

the are in a way... the constant variable transmissions sort of play on this.. your old briggs mini bike had a flywheel that worked very similar.. (centrifugal clutch)

Changing moment of inertia, but not mass there. If I recall my go-cart (Tecumpseh) engine.(Centrifugal Clutch) ,Asbestos shoes spring loaded to fly out as RPM increased. Gradually grabbing the walls attached to the drive sprocket.

 

[GPW]

It is the same thinking used on lightened & balanced cranks and the other variable of knife cutting the crank to help cut through the oil for less drag or use of windage trays. Some say yes some say no. Some say yes on small displacement bikes and no for larger. Loss of torque is one the reasons bigger bikes take less off the crank. Could confirm Mr. Bogus's stored energy theory.

 

[Mr Bogus]

They actually had type of clutch that used giant roller balls.. as the engine RPM went up, they pushed against a spring loaded plate which in turn changed the effective working diameter of a belt pulley..

The balls moving outward increase the "effective" mass of the flywheel and that extra mass is utilized to move the belt further out (closed the gap between the two pulley halves and forced the drive belt outward) on the pulley essentially loading the motor with more demand..

I am familiar with the other type but never really fooled around with them very much.. The advantage of the roller ball type clutch is there were no parts to wear out.. they also lacked that tattletale rattle of the shoe style clutch..

I am trying to find a picture of the thing but seems rather hard to do... many mechanical "engine governors" were set up with the same principal of set of fly weights.. now I am not certain that this really changes the "physical mass" of the unit but it does change the amount of rotating mass pretty effectively

 

[Robot]

They actually had type of clutch that used giant roller balls.. as the engine RPM went up, they pushed against a spring loaded plate which in turn changed the effective working diameter of a belt pulley..

The balls moving outward increase the "effective" mass of the flywheel and that extra mass is utilized to move the belt further out on the pulley essentially loading the motor with more demand.. I am familiar with the other type but never really fooled around with them very much.. The advantage of the roller ball type clutch is there were no parts to wear out.. they also lacked that tattletale rattle of the shoe style clutch..

Interesting.....I have never seen the one you mention, sounds alot better than the one I had. My buddy would change the internal springs, so it would have a "pop the clutch" type start

 

[Mr Bogus]

Interesting.....I have never seen the one you mention, sounds alot better than the one I had. My buddy would change the internal springs, so it would have a "pop the clutch" type start

yea I like the idea you can tune a lot faster by changing a couple springs.. ToteGote used these "ball type" clutches almost exclusively along with a motor jack system.. you could physically move the motor forward and backward forcing the belt to ride higher or lower in the grove and so changing the torque to hp ratio driving the wheels... simple but really effective setup..

Oh I found a similar setup.. snowmobiles doh!! they use a fly weighted variable diameter pulley setup... sorry I never really rode a snowmobile so did not occur to me..

 

[HillsRider]

I was just going to throw that out there for you, Bogus. I have started tinkering with the clutching on my sled this year, so I have a basic understanding of what is happening with them.

 

[Robot]

yea I like the idea you can tune a lot faster by changing a couple springs.. ToteGote used these "ball type" clutches almost exclusively along with a motor jack system.. you could physically move the motor forward and backward forcing the belt to ride higher or lower in the grove and so changing the torque to hp ratio driving the wheels... simple but really effective setup..

Oh I found a similar setup.. snowmobiles doh!! they use a fly weighted variable diameter pulley setup... sorry I never really rode a snowmobile so did not occur to me..

Cool, I have seen something similar on industrial machines