Godfrey DiGiorgi wrote: >On Apr 7, 2008, at 7:45 AM, Mark Roberts wrote: > > >>You could get a lot of horsepower from those engines if you had the >>skill, time and money for it. My friend stopped racing his when it got >>to the point that the helical-cut primary drive could no long >>withstand >>the forces being fed through it. There is a shop in England that >>makes a >>straight-cut primary drive kit for that engine. Cut from billet. >>When he >>found out the price he decided it was time to stop development on that >>project :) >> >> > >The fact that the primary drive was a helical cut gearset both quieted >their operation and increased the amount of power they could handle, >for the materials etc used, at a small expense in power consumption. >If he was breaking gears, it was because he was reaching the material >limits for the production drive gears, not because they were helically >cut. > >Straight cut gearsets produce lower power losses but require more >durable materials and better production qualities (precision grinding, >heat treating, etc) to withstand the loads, that's why they're much >more expensive (aside from the fact that they are made in very small >quantities...). > > The _big_ advantage of straight cut gears for ultimate power output is that they do not produce (well, they shouldn't...) any side loads. It's often the helical gears trying to force themselves apart along the axis of the shafts that causes problems.
>Ducati made several production road racer variants based on these >engines with straight cut gears in displacements from 100cc to 300cc. >A friend of mine when I lived in NY (Charlie Keene from New Hampshire) >had the 175cc Formula III ... a truly outrageous little monster for >its time ... He raced it in AAMRR street production as late as the >early 1980s and was regularly pulling podium placement against then- >modern 250s. (He also ran a '58 Manx Norton 500, managed to get that >qualified for one of the US 750cc races at Pocono Speedway about >1976-77 ... qualified third from the back in front of two TZ700s, when >Ken Roberts was the leading contender... Shoulda seen how KR passed >him at the end of lap three... [EMAIL PROTECTED] ;-) > >Another friend of mine, Harold Parks, now retired to Nevada but still >riding, held the 250cc single-cylinder drag racing record with a >modified 1966 Ducati 250 Mark III ... I'm not sure whether he still >holds it. > >Wonderful, quirky, fun little machines. > >Godfrey > > > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
