Piston Ring Fitting

Discussion in 'Help Wanted' started by Skankin_giant, Feb 8, 2012.

  1. petternut

    petternut Administrator

    Steve
    I don't think anyone is now suggesting you should. The debate seems to have evolved into peg styles and there relative merits.
    Nick the PAB one seems nearly as bad to me as the peg fills the whole groove.
    The general style is one that occupies only half/two-thirds the groove as used by; Villiers, S-T and Petter amongst others.

    cheers
    Roland
     
  2. martinpaff

    martinpaff Member

    Hmmm...

    Since I was the one who mentioned what a rotten design it is, perhaps I should come back.

    I agree that Steve should stick with what he knows, although I think the chances of successfully hand-filling new rings to shape is no better than replacing the pin with a sensible shape. In this engine, however, I suspect if you wound string around the piston it would work - we're not going for speed or much compression here. I'm not just talking through my rump - I have a bit of experience tuning and racing 2-strokes.

    The argument that it was good enough for Scott motorcycles doesn't really hold water. They were not exactly successful, and outside the cognoscenti were often considered a bit of a joke. (very pretty though!) The sales speak for them selves - I would guess that Yamaha made more 2-strokes in one afternoon than Scott made altogether - Yamaha didn't use tapered piston rings. My own engines, routinely doing 18,000rpm, didn't either.

    So the question is; "originality" or "technical superiority"? On balance, as long as Steve can achieve the correct fit and seal, I would agree - go for originality! The benefit is; if it just doesn't work out, there remains the possibility of changing the set-up.

    Martin.
     
  3. nickh

    nickh Member

    Martin; I can go off people you know! Scotts were technically, if not commercialy, successful when compared with contemporary designs (pre WW1 lest we forget), just that they stayed in production way past their sell-by date (probably about 1928 if not even earlier).

    Roland; yes, if anything the PAB peg seems to present an even bigger leakage path than the SE / motorcycle type. I guess there must be some reason for it being like that, as you say, the 'half in, half out' round peg was very much established practice.

    Just out of interest, I attach a selection of stop designs from Irving's 'Two Stroke Power Units'.

    NHH
     
  4. campingstoveman

    campingstoveman Active Member

    Gentlemen,

    Can I ask a daft question, I've read this thread from start to finish every time someone posts and I'm loosing the will to live, Scott had this design for a reason what ever that was and as far as I can tell Steve wants to return to the original with the new rings so why all of the discussion!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Martin P
     
  5. petternut

    petternut Administrator

    Out of technical interest and the love of good-mannered dispute. We should perhaps have started a new thread but que sera.
    At least we are not discussing; vans, monster trailers, hidden engines or making bearings from tin-soldiers :)

    regards

    Roland - V grumpy after waiting all day for a courier who arrived at 1620.
     
  6. martinpaff

    martinpaff Member

    For somebody at death's door you seem to be typing ok...

    :lol:
     
  7. Skankin_giant

    Skankin_giant Well-Known Member

    Well going to give it ago, take my time, and see how I get on! If I cant do it, I have an expensive door stop.

    Cheers Steve
     
  8. nickh

    nickh Member

    Err, weren't you the one complaining it was too quiet?

    NHH
     
  9. Numpty1

    Numpty1 Member

    Thank you Gentlemen, you have increased my limited knowledge!

    Mark
     
  10. petternut

    petternut Administrator

    Steve
    It was not my intention to over-persuade you into to doing something that you have not the tools to do. Most of the people in this thread are equipped at home or work to stand a fair chance of success. As you observed it will work well-enough as designed.

    cheers
    Roland
     
  11. Skankin_giant

    Skankin_giant Well-Known Member

    Made a start on the rings, ones is good the other not so, need a little more meat removed and tidying up! but getting there.

    Cheers Steve
     
  12. Skankin_giant

    Skankin_giant Well-Known Member

    Had the Scott going yesterday, nice load of compression now, and will start with a couple of flick over compression.


    http://www.youtube.com/watch?v=VlGDYVGSaKo

    Need to finish the thing off now, and work out the oil ratio, been told 15 drops a min is quoted, but is that for 1 oiler or both, this is at about 6 drops a min, so 12 for the both, plus a little 2 stroke oil in the fuel as its whats left over from the Scott PAB.

    Im not sure if the needle in the carb is to short and when the float is up in the groove it floods, could also do with picking up the speed a touch, running at 550rpm there.

    Cheers Steve
     

Share This Page