From mwest_at_cdsnet_dot_net Wed Oct 21 14:02:29 1998 Received: from mail-01.cdsnet_dot_net (mail-01.cdsnet_dot_net [220.127.116.11]) by yiff.azaccess_dot_com (8.8.5/8.8.5) with SMTP id OAA25167 for <vintagebus_at_type2_dot_com>; Wed, 21 Oct 1998 14:02:23 -0700 Date: Wed, 21 Oct 1998 14:02:23 -0700 Message-Id: <199810212102.OAA25167_at_yiff.azaccess_dot_com> Received: (qmail 3806 invoked from network); 21 Oct 1998 21:14:04 -0000 Received: from d01a8867.dip.cdsnet_dot_net (18.104.22.168) by mail.cdsnet_dot_net with SMTP; 21 Oct 1998 21:14:04 -0000 X-Sender: mwest_at_mail.cdsnet_dot_net Mime-Version: 1.0 To: VintagVW_at_listproc.sjsu_dot_edu From: mwest_at_cdsnet_dot_net (Mike West) Subject: Crankshaft, Flywheel, Weights Cc: vintagebus_at_type2_dot_com, type2_at_type2_dot_com Doin' a crank . . . Actually more of a visit to 3 of them . . A stock type 1/2/3 (1600 engine) A stock type 4 . . the later van engine 1700/ - - /2000 engines The last is a type 1 counter-weighted crank . . Bugpack. . welded. There is always that question of "what it is? and do I need it?" Looking at the stock crank(t1), I do regret there are no pictures. Still I will try to do this with words . . I went down and borrowed a scale . . like a bathroom scale . . Put my 25 pound barbell on it for a calibration check . . ok . . A stock type1, 69mm crank weighs in at 19 lb. The gears weigh another pound . . . . The 74mm counter-weighted crank weighs in at 21 lb. bare . . . Note: there are good photos and some real good data in Bill Fisher's book "How to hot-rod vw engines" . . that CW crank in there looks a lot nicer than the one I have . . . The van crank, a 66mm stock job weighed 22 lb bare, 23 w/gears . . A stock 12 volt, 200mm flywheel weighs 16-1/2 lb. less than I had thought. That's a type 1/2/3 flywheel for the non-gear-heads . . I went out and drug the one off the t4 engine in here . . 210 mm weighs 14-1/2 lb . . not at all what I expected . . . Giving these cranks a visual . . it's my eye . . YMMV . . :-) The stock 1600 crank while forged by definition is only partly forged. You can see both forging marks and cast surfaces in various spots . . The CW crank I have here kind of worries me . . one spot even has raised letters cast on it . . pretty hard for me to see this as anything but cast. I assume it is a partial forging like the stock . The type 4 engine crank is a beauty tho, no cast marks anywhere and most surfaces forged to finished condition . . a true forging as far as I'm concerned . . Let's cover the counter-weight thing . . This counter-weight is put in a place that makes every conn-rod journal balanced within itself. It eliminates a bending moment that was there before . . in so doing it also removes some harmonics from happening. Those are bad things for your bearings and crank and on thru to your case. The fact that it adds a couple pounds to the crank is actually to the good in one manner . . it transmits a smoother load to the flywheel . . This makes it easier on the crank/flywheel connection plus more ease to the bearings . . . The negative is, by definition, horse power has a time element so any added mass to the shaft is a loss of hp. So you lighten the flywheel. None of the above is for street . . it's for getting off the line. Fisher's book says a stock crank is good up to 5000 rpm . . suggests putting a rev-limiter on if your carbs are too big . . It isn't mentioned but while a limit on rpm is apparent so is fast wind-up. What I mean there, is if you have some big pistons in there and stand on the throttle for a nice wheelie . . you can bend that crank big time . . So if you have a heavy foot even in a 1600 engine, it would be to your advantage to have a CW crank . . What I have on Balancing: damn little . . :-) My local guy says he balances to 1/10th gram at 850 rpm . . I have a definite maybe that he is talking of a centimeter-gram which is what the Bentley Manual speaks of. The stock crank specs at 12 cm-g max. Stock flywheel (1600) is 20 cmg as it writes it . . . Max what? it gives no rpm so it could be interpreted at max rpm. . Never happen joe . . . What the hell is he talking about? you say . . . :-) A centimeter-gram is like an inch-ounce as far as I know . . put a gram out on the end of a 1cm lever arm . . . Why . . . ! . . . ? we're talking of dynamics here . . something moving . It has to have a direction or vector . . one of you teachers can explain this better . . . Now to the machine that is doing the work balancing this pig it is a reading at the bearings it's turning on in a location that rotates with the shaft. 3 or 4 pressure sensors mounted around the bearing . . It resolves the heavy spot into a location relative to the start point and can then point that place out to the operator on the shaft circle. It also tells him how much of course . . One or more have asked can you statically balance like a bicycle wheel? In theory you can . . get a couple extreme knife edges and set them up flat and parallel and level with the earths bulges and then if you have a balance you can spin it on the bearing surfaces and it will stay where it stops every time and doesn't stop in the same place etc. Then by sticking some small weights like coins and tape on the light side, that's the side pointing up, you could achieve some kind of balance. I don't think it's such a good idea tho . . . . It's only $35 to have it done right and I wouldn't even trust me on this one. Don't think I'd do it with a bicycle wheel if I had options . . Are the counter-weights necessary to really balance the crank? . . . ? Not at all . . it balanced in all planes before and in fact the counter-weights are put on such that they zero out each other on the shaft . . ie. 2 on one side and 2 at 180 degrees. I'm going to break this off and do a second one on the monkey-motion of the crank. . . . west "pushin' back the dark"