Mike Willmon wrote:
So another question for the list. Since welded gears are not EVen allowed under NHRA rules and spools are only allowed with aftermarket housings, whats the strongest type of locking differential to get for drag racing? Detroit, Auburn, ARB (are ARB Air lockers EVen strong enough for racing?)?
I think they’re all pretty strong. I love the Detroit Locker in White Zombie. Not a lick of problems to report, and it simply goes about its business. In a quiet EV, it’s pretty cool because you can clearly hear the locker ratcheting and clicking as the car turns, then when you line up straight on the strip launch pad, it goes ‘Ka-clunk!’ as if to say, “Yeah, I’m ready to help you paint twin blacks stripes.” The Detroit has taken all the power the Siamese 8 has twisted into it and has easily handled the torque. I would highly recommend one.
I’m pretty sure the new Strange differential is going to be fitted with a set of 3:70 gears. Two years ago, I chose 4:57 gears and they netted the car with its best 60 ft. time of 1.59…but only once on a night with extreme stickiness on the track (your shoes nearly stuck to the pavement from all the Pro Stock rubber being laid down that night). The more typical 60 ft. time was 1.62 – 1.66 depending on track conditions. The 4:57 gears had the motor spinning precariously close to the safe rpm limits though, at the trap speed of 106 mph. When I considered a ratio change to prepare the car for a better top end speed with lower motor rpm, I was worried about losing the incredible hole shot we had. The choice was to go gradually in a step-by-step procedure, as in from a 4:57 to a 4:38 to a 4:11, or simply bypass the in-between step of 4:38 and going right to the 4:11. If going the two steps straight to the 4:11 indeed, ruined the hole shot while improving the top end, then ‘finally’ all those yelling at me about a transmission, would have a point.
History now shows the pro-transmission forces were as I figured, off base, as the change to the 4:11 didn’t affect the hole shot one bit! The same 1.62-1.66 60 ft. times were being delivered…thank you, abundant electric motor torque! The unfortunate thing, was that all through ’06, we never saw the top end improvement with the gear ratio change, but that was more due to the second battery pack not being as strong as the first one was and the car turned out to be battery limited that restricted any improvement at th far end of the track. You could see it in the power graphs we plotted…you could see the pack sagging down, sometimes as low as 169 volts long before the end of the run.
Now, we have a very strong battery pack that’s not even turned up yet. Because of the pack’s stiffer voltage under current, the motor is getting BIGGER amps at the far end and raising the terminal voltage across the motor, thus flash-over at higher rpms. Time again, for a ‘taller’ rear end ratio. I could go from the 4:11 to a 3:90, but anticipating the kind of power we can get to over-come any kind of loss out of the hole…remember, we can crank up the battery amps on launch another 500 amps if we need to…I’m going with another two step move and will go straight to the 3:70 gears. It’s entirely possible this might be too far and the 60 ft. time will suffer, but it’s also possible that a small loss there might pay big dividends in the 1/8th mile speed and acceleration that will more than make up for any loss in 60 ft. time. i guess we’ll all have to wait and see The taller legs this ratio will give the car will keep the motor volts down to where at 110 mph or so it should still be at a low 150V-155V or so. Who knows, maybe we’ll see an 11.9 @ 110 mph next time we hit the track!
See Ya……John Wayland