> i had a 69 datsun 4 door... ignition switch fried. replaced it with a toggle switch and a push starter button from pep-boys stuck it in the cig lighter hole.... nobody could figure out how to start it...
Did just that with a '70 Volvo 1800. You cudda got a new Datsun switch, or adapted a Chevy switch. The Volvo was too-too clever: the switch and spark-coil were permanently tied together with armor cable! No way you could hot-wire it! And no way to get spark with a failed switch.
Evidently Volvo didn't think car thieves would bring their own coil. Since the Volvo dealer was promising over 6 months to get another $500 assembly, that was a pretty good bet.
Well, spark is spark. I lashed a Ford spark-coil to the useless coil. Powered with a toggle switch, moved the HV wire over. Pushbutton start like you.
> Those hole-shots he got were amazing. I'm really surprised it was able to hook up as well as it did. Instantaneous torque is a marvelous thing.
It's amazing.
But it isn't just "big torque". Gear-down and get any torque you want.
The force-density of a motor pole is lower than a piston. True, the rotor is more compact than a crank-and-rod, may run higher RPM (allowing more gear-down).
Although for drag-racing there is a limit to gear-down. If the mill moves faster than the vehicle, its mass is geared-up. High-performance cars can have effective low-gear mass twice the vehicle weight, due to 100 pounds of flywheel, crank, and pistons multiplied by total gear ratio. The Sports Car by Colin Campbell has an adequate discussion of this effect.
I'm thinking it is smooth torque. Motor can give high torque at zero RPM, explosion engines typically fall to zero torque at zero RPM. So we always need a contraption to engage a high-RPM engine to an axle which starts from zero RPM. Clutches are grabby or slow. Fluid couplings are smooth but lossy.
Also a motor tends to have smoother torque. Not dead-smooth, not for the usual constructions. But instead of an explosion the force/rotation is more like a sine. Above 12 cylinders the engine can be pretty smooth. But lesser cylinder engines bang-bang the tires. Flywheels fix this for high RPM but not so much for low RPM. The peak torque tends to break traction, so the average force is less than ideal traction.
Moreover the torque can be controlled EXACTly. I can feather my engine but it is a very approximate thing. A butterfly throttle does not limit torque, it limits power. So as RPM falls, torque rises and vice versa. In a motor, current IS torque. The old knife-switch controllers had no control, but his microprocessor controller KNOWS the current and can be told what current to use.
He could first-approximation set his current limit in the pre-race burnout. Bring up current until tires spin, note that current. There is a correction between the slick burnout box and the rubbery starting-line which has to be found or estimated.
Tire traction is maximum at around 5% slip. If you "simply" controlled current so that rear wheels went 5% faster than front wheels (corrected for diameter) (assuming front wheels roll not hop), your traction would be maximized even for odd or uneven track surface.
The lead to LIon swap is interesting. He lost weight, but did not go proportionally faster. He lost weight over the drive axle, had -less- available traction (and that car sure is traction-limited). If he had a lot more than 2 seconds development time, he'd be moving some nose-weight rearward.
His cables and connector look way too small. He must have some voltage drop. 300HP at say 400V battery is 560 Amperes, and that looks like a 100A connector. At the hole-shot, this does not matter: motor voltage is very low, if line drop is high the controller just has less to drop. But if his hole-shot head-start has not won the race and it comes to 100+MPH over the last 100 yards, he needs every one of his 300HP. That body needs maybe 150HP to -hold- 100+MPH, and some excess to keep gaining speed. Since mildly-hopped Stingray or GTO will have excess HP at 100+MPH, the electri-car needs some too.
I'd feel better about the LiON conversion if I knew the batteries were recycled as reliably as lead-cells are. Sumthin like 98% of battery lead is recaptured.
Topic: electric dragster... (Read 8358 times)