Engineering a crowded roller bearing setup for the big end

Discussion in 'Performance Mods' started by lazylightning@mail.r, Aug 15, 2012.

  1. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Hi!
    I'm trying to put together a decent immortal crankshaft. Unpressing and repressing and truing is not the problem. These are knowns. The question is, what size and how many rollers are packed into the space between the conrod and crankpin bigend?
    For example, my conrod big end is 22mm inner diameter and the crank pin is 16mm(15.95?) in diameter. The bearings that came out are 3mm in diameter (from the smashed cage). By placing them into the space, I count that I could probably fit about 22 - 24 such roller bearings in there. But how tight will it be? What if, I put in 22 and there isn't enough space for number 23 and there is enough space to be a noticeable gap. Maybe an off size like 2.9 mm is in order to get more in so the last one goes in flush with a pretty tight fit. This is all theoretical of course. I'm planning to use special ceramic racing coatings on all surfaces here which take up only a micron of space or less and dont affect clearances. Then the tungsten disulfide that is burnished in also takes up no space.
    Has anybody seen one of these Chinese kits with a crowded roller bearing - big end setup with the crank unpressed and looked closely at this setup? What were the spec.s observed? Has anybody got experience in theoretical clearances for crowded roller bearing setup on conrods for two stroke racing machines?
    Thanks in advance

    Best Regards,
    Paul
     

  2. Fabian

    Fabian Well-Known Member

    Virtually all Chinese bicycle engines come with a crowded roller bearing as standard these days.
    It's easy to see the crowded needle rollers in the big end when you have the cylinder removed from the case.
     
  3. lazylightning@mail.r

    lazylightning@mail.r Active Member

  4. lazylightning@mail.r

    lazylightning@mail.r Active Member

    In Moscow, there's only one dealer of these engines. It's all pretty lame. They all have the caged big end rollers =-( But that doesn't matter, because there are plenty of places to buy roller bearings for high performance. What can you tell me about the big ends that had crowded rollers? I noticed that in one of your photos, you show the conrod big end as having an inner diameter of 21mm Mine has 22mm and it's riding on the same 16mm diameter crankpin.
     
  5. lazylightning@mail.r

    lazylightning@mail.r Active Member

    What was the diameter of the rollers? 2.5mm - ish?
     
  6. Fabian

    Fabian Well-Known Member

    The diameter of the rollers should be visible on the digital caliper
     
  7. Fabian

    Fabian Well-Known Member

    2.49mm for the caged needle roller bearing
     
  8. Fabian

    Fabian Well-Known Member

    It's interesting that your I.D. is 22mm.
    I have not checked the I.D. for the crowded needle roller bearing big end, because i haven't had a failure yet. It's given me bullet proof reliability.
     
  9. lazylightning@mail.r

    lazylightning@mail.r Active Member


    I thought so. Mine are about 3mm, because my conrod has the 22mm inner diameter. I wonder what the micro-specs and clearances down to a thousandth of an inch are for the crowded roller setup, regardless of 21mm or 22mm conrod bigend diameter. Any iformation will be quite useful for engineering purposes...
     
  10. Fabian

    Fabian Well-Known Member

    With a 22mm I.D. you can upgrade to a much better "brand name" caged needle roller bearing. That was my original plan in the beginning: boring out the big end to 23mm and having a 22mm I.D. tool steel sleeve pressed into the big end to take a K16 x 22 x 10 caged bearing, but by the time i started to get the process moving forward with a tool maker, the Chinese were producing crowded needle roller big end bearings which have proved to be very reliable.

    Given the I.D. dimensions of your connecting rod, you should be able to install a quality needle roller bearing.
     
  11. lazylightning@mail.r

    lazylightning@mail.r Active Member

    An interesting link: http://www.eurospares.com/graphics/engine/INAcrankpinbearings.pdf

    The good titanium caged caged bearing could be a good temporary option for me...
     
  12. Fabian

    Fabian Well-Known Member

    From previous research, the INA-F.A.G bearings are very high quality items.
     
  13. FelipeCobu

    FelipeCobu Member

    I do found K16x21x10 INA bearings on a supplier here in Brazil.
     
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