Knife-edge a race crank? - Page 3

**italcarguy** · #31 (**permalink**) 03-13-2008, 08:05 PM

Quote:

Originally Posted by George Willet

Nadar: Don't!! George

**jrclem** · #32 (**permalink**) 03-13-2008, 08:56 PM

I'm not sure that the aerodynamics aspect are nearly as big a deal as the reduction in spinning mass... I have previously done all I could to reduce the mass of the spinning stuff.... (O.S.Giken clutch & Flywheel {the lightest available} and light-weight do-nut cage, etc.) The Knife Edged (i.e. LIGHTENED) crank has made a very noticeable difference! This led to me missing THREE shifts in my flag race last weekend at California Speedway... I haven't missed a shift under race conditions in years... The new lighter crank involved a little learning curve, and, as we all know, it's hard to teach an old dog new tricks!
That said, I've figured it out and won't be screwing up (at least that way) again any time soon.
Re: Italcarguy's three years of trouble free operation... I wouldn't give it much credence, he has spent most of that time on the sidelines... DUCKING ME!!!

PSk · #33 (**permalink**) 03-13-2008, 09:10 PM

Quote:

Originally Posted by jrclem

I'm not sure that the aerodynamics aspect are nearly as big a deal as the reduction in spinning mass

**jrclem** · #34 (**permalink**) 03-14-2008, 11:17 AM

Here's a pair of videos from Fontana last weekend (Flag Race part 1 & 2)

YouTube - CalSpeedway3-08pt2 (Part 2)

http://www.youtube.com/watch?v=NwRRod7C954 (Part 1)

GTV-GR · #35 (**permalink**) 03-14-2008, 01:26 PM

jrclem sweet engine sound! What the hell have they done to the sedan so that it's quicker than you?

roy · #36 (**permalink**) 03-14-2008, 03:31 PM

I just cut all the counterweights off the 1750 crank & had it balanced ( 10# off a 42# crank ). My machine shop said it would be no problem as long as the engine is always accelerating or slowing down ( no harmonics from constant 7000 rpm full speed runs around Daytona ! ). It's been 8 years now & it still runs great !

**velocedoc** · #37 (**permalink**) 03-14-2008, 05:13 PM

Quote:

Originally Posted by roy

I just cut all the counterweights off the 1750 crank & had it balanced ( 10# off a 42# crank ). My machine shop said it would be no problem as long as the engine is always accelerating or slowing down ( no harmonics from constant 7000 rpm full speed runs around Daytona ! ). It's been 8 years now & it still runs great !

**jrclem** · #38 (**permalink**) 03-14-2008, 06:47 PM

Boles:
Yup. DO NOT screw with the counter weights for steady state running... it WILL pound out the bottom end!
GTV-GR:
The Super is indeed well prepared, but the magic ingreediant is that damn whippersnapper Fabrizzio Rimicci! The kid drives his *** off and makes only the rarest error, as you can see in the video.

**italcarguy** · #39 (**permalink**) 03-14-2008, 07:40 PM

Quote:

Originally Posted by jrclem

This led to me missing THREE shifts in my flag race last weekend at California Speedway... I haven't missed a shift under race conditions in years...

**jrclem** · #40 (**permalink**) 03-14-2008, 07:45 PM

Anthony:
...and where were you?

fafner1 · #41 (**permalink**) 03-27-2008, 09:02 PM

Why don't F1 engines use knife edge cranks? Several reasons. Their super short strokes (on the order of 1.6 inches) means the rotational inertia is near minimum, and their super efficient scavanging systems means not only is there not any oil in the crankcase to generate drag; there isn't even much air. The 2000 Ferrari V10 used a total of 11 scavanging pumps to insure the crankcase operated under a reasonable vacuum.

FMG_V6_btb · #42 (**permalink**) 03-28-2008, 01:53 AM

Rotational inertia doesn't depends directly on the stroke, depends on the masses distribution of the rotating parts. Obviously short stroke crankshafts have short diameter, and for that the masses are more next to the center, which means less inertia moment. Due to this fact and the extremely high engine speeds and lineal inertia forces induced by the pistons and rods (part), the correct crankshaft balance by means of the counterweights becomes more difficult. For that reason F1 crankshafts uses some inserts of very dense material in the counterweights (as far as possible from the rotational axle), so why F1 engines does not use knife edge cranks?... because the need to maintain as much counterweight as possible.

Pictured: Ferrari F1 V10 alternative and rotative parts.

Paco.

**jrclem** · #43 (**permalink**) 03-28-2008, 08:36 AM

Here's a link to the guys that make "Mallory Metal", an ultra dense material for weighting cranks... interesting stuff.
Mi-Tech Metals - High-Density Tungsten Based Metals

180OUT · #44 (**permalink**) 03-28-2008, 04:26 PM

Brabham/twin cam Ford race engine w/ modified crank. 8k +/- rpm. $$$$$!

**ECARRILLO** · #45 (**permalink**) 05-04-2008, 07:37 AM

Old Master,
Were you able to get more HP's? Do you have the before & after? Was it worth it? Cost vs. benefit?