flywheel could be the answer

Discussion in 'General Questions' started by japat100, Aug 6, 2007.

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  1. japat100

    japat100 Guest

    has anyone ever tried adding a flywheel ?? i am beginning to think it may make a great difference , less vibration, much smoother running , idle better and i think would get rid of clutch noise ,, it seems there is only one sweet spot now on these motors 27 mph ?????? my belief is if somehow you could mount a flywheel maybe 1 or 2 lbs on the crank shaft it would be all sweet spot from 500 rpm ,to 7000 rpm , there already the clutch that spins but not much of a flywheel due to the slower rpm ,, the magneto side of the motor has some weight but it sounds like not enough , the clutch noise and the chain jerking in my view is caused by inconsistence rpm of the motor ,,and the answer is a flywheel 1 or2 lbs
    maybe theres a way to try ,,
    just a thought to make things better

  2. gone_fishin

    gone_fishin Guest

    ever notice the happy-time crank isn't balanced? i'd think that would be the logical first mechanical tweak, just my opinion.
  3. Lowell

    Lowell Guest

    How about a cush drive like a motorcycle?
  4. japat100

    japat100 Guest

    if i had only one wish to improve my motor it would be to balance the crank ,,vibration is a killer ,,i am surprise that at high rpm the whole motor don"t fly apart

    one of the jobs of the flywheel would be is to balance the crank , a power saw ,or weed eater turns 7, or 8,000 and still no vibration ,,

    no doubt over the next couple years there will be many improvements to happy-time and the motors we have now you may find at a flea markets ,,,2 for $5.00 ,and for extra $1.00 they will give you 5 spark plugs from china with there tops missing
  5. lotsa_mpg

    lotsa_mpg Guest

    Adding some weight in the form of a flywheel might help get rid of the vibes, however I wonder if it might also add some stress. No doubt, it would also worsen the already lacklustre throttle response. Man, I wish some Chinese factory would start producing some little Wankel rotary engines for these bikes. Those things are incredibly smooth and have great torque even at low RPM's. I've been trying my darndest to find one of those Sachs-Dolmar chainsaws they made with the Wankel engine back in the seventies. I think it would make a fantastic bike mill. Any I've found have been priced outta sight. Good luck with the flywheel experiment.
  6. OldPete

    OldPete Guest

    Honest opinions

    Light flywheel advantages.
    Faster acceleration.
    Quicker gear changes because rpm drops faster.

    Heavy flywheel advantages.
    Smoother low speed running as well as a lower idle speed.
    Less shock loading to the drive train from power pulses.
    Better mid-range torque.
    Better throttle control when on ice or loose surfaces.
    Sometimes a very impressive increase in fuel mileage(a lightened flywheel can cut mpg by 50% depending on the motor).

    A heavyer flywheel will not reduce engine vibration by much. At lower rpm it might a little just because the mass is there but at higher rpm it will have very little impact.

    Balancing a built-up crank is expensive because it must be pressed apart, the rod removed, then pressed together, balanced, then the rod reinstalled. Lots of labor there.
    To balance a crank, all rod rotary weight and about 50% of the rod's reciprocating weight(balance factor) is added to the crank pin. The con-rod is weighed while suspended by its end centers, then brass weights added to the crank pin.
    EDIT: The weight of everything connected to the small end of the rod is also added to the balance factor. The piston, its pin, rings, locking clips and roller bearing if used.

    Depending on what is needed or desired by the owner the balance factor can be anywhere from 40% to 60% . Lighter gives smoother running at high rpm. My old Guzzi had a balance factor of 47% and was as smooth as glass at 7000rpm but a little rough at 4000rpm where most of the riding was done.

    Single cylinder engines are the hardest to get balanced smooth. A 90degree V-Twin like Guzzi or Ducati or a three cylinder in-line are the easyest small four stokes to get smooth. Kawisaki two stroke triples were smooth running motors too.

    Cush drive like a motorcycle??
    The rubbers that are installed on either side of the spokes for the rear sprocket should provide enough to protect the spokes from serious shock loads if the clutch is not treated roughly and the mounting bolts were not tightened to the enth degree (or so this old mechanic thinks).
    Last edited by a moderator: Aug 8, 2007
  7. rcjunkie

    rcjunkie Guest

    A heavier flywheel would worsen the already anemic performance of these engines. Balancing the engine assmebly is the answer that cures the problem and doesn't mask the symptoms like a heavier flywheel would do.

    As for a rotary engine having high torque at low RPM? NO WAY JOSE!!! Rotary engines have many benefits but low end torque IS NOT one of them. If you don't belive me, you are welcome to drive my anemic 91 Mazda RX7 which has 30,000 original miles and needs to be revved high to get the car moving. There is a reason why rotary powered vehicles have a 8000 to 9000 rpm redline!!!! Believe me, I know rotaries. I have owned 5 rotary powered vehicles in my life and even owned a rotary powered model airplane engine. The first full sized kit private plane I will build will be powered by a 13B rotary engine spinning at 7000 rpm feeding a prop at a 2:1 reduction gearbox.
  8. lotsa_mpg

    lotsa_mpg Guest

    rc, my only experience with rotaries is with various Sachs 295 & 303 cc mills used in snowmobiles in the early seventies. They had gobs and gobs of low end grunt compared to conventional two strokes of the same era. However, snowmobiles run torque converter transmissions and perhaps these trannies were more capable of making the rotaries come alive than would a conventional gear box. I'm glad you shared your thoughts on the Wankel power characteristics because now I know that if I was to find one, I'd need to use a torque converter set up to make it work.....and I don't think it's possible to mount one on the small chainsaw engine that I was hoping to utilize.
  9. OldPete

    OldPete Guest

    Look at pics of the crankshaft used in these engines. Those are wide counter weights! They are not cut down like pork-chops(lightened crank). A heavy flywheel does slow down acceleration but it offers many advantages.
  10. 570rm47

    570rm47 Member

    My Apologies for digression from topic but i have a thing for rotary engines.

    I am not an engineer but they are so fun i have had a couple and when i was a bit younger you could buy one for nz$1200 a series 4/5 13b, i had cash so it came with a turbo, an inter-cooler, wolf 3d tuning computer wiring loom and a gearbox. I left my original 4 speed and diff in for a bit it peeled out in every gear like that till it didnt do anything anyway.
    The only thing it had done was a small hole was drilled just above the original intake on the housing a mere sound orientated mod, the computer was plugged in as set at manufacture.

    Another 600 dollars and some help from a friend and it was a serious coffin at high speed and that 600 was for seals and a new diff and my friends tools and porting expertise. Mine was not even exceptional.

    Now the same motor re-conditioner wants nz$5000 for a block re-conditioned internally with nothing attached :icon_cry:
  11. Pedalnwolf

    Pedalnwolf New Member

    centrifugal clutch.
  12. Fabian

    Fabian Well-Known Member

    pull start.
  13. HeadSmess

    HeadSmess Well-Known Member

    harmonic balancer with synchromesh
  14. keatonx

    keatonx Member

    Always wondered about putting a harmonic balancer on a little single cylinder :jester:
  15. HeadSmess

    HeadSmess Well-Known Member

    the harmonic balancer in old aero engines, and still occasionally used, was to have the counterweight on the crankshaft suspended on very short linkages, allowing it to rock back and forth slightly :)
  16. jaguar

    jaguar Well-Known Member

    Everyone should balance their crank.
    Just buy the drill bit I recommend on my site, take the crank out, drill it, and put it back together.
    If there is no way in hell you are going to do that then the least you should do is put a lighter weight piston pin in. I recommend some on my site.
  17. darwin

    darwin Well-Known Member

    Anyone notice the date of the OP? We're in a timewarp Scotty, beam me up!
  18. HeadSmess

    HeadSmess Well-Known Member

    hence the smart ass reply :) not my fault people kept on with it!

    im living in the 70's though i was never there ;)