ColinRX7

Cool!

ColinRX7

Wow surprised I didn't see this earlier. Here's a neat setup that replaces the tailshaft assembly of popular transmissions. Electromagnetic actuation.







Didn't realize this was an option to add-on to a factory box. Apparently 4 speed hot rodders have been into this for a while..



http://www.gearvendors.com/installation.html

inanimate_object

That 's based on a type e gearbox, I'm not sure one of those could handle the power of a 13b unless quaife have beefed it up a bit.



EDIT: the rocket box I mean.

j9fd3s

i was about to chime in; the triumphs of the late 50's and early 60's came with the option of an overdrive like that. the racers used to wire it up so that they could use it in 2nd 3rd and 4th, think like having a 3rd and a half gear... 4th... 4th and a half....



so its been done and it works, http://www.tjwakeman.net/TR/Net_racing.htm

Baldy

Ahh yes, there is a TR6 at our local autocross that has that. I was wondering aloud how he could shift so quickly, then someone explained it to me.

Old Splatterhand

very interesting read

now as much i'm into engine bulding, i gotta admit, i know as good as nothing about trannies. But i'd like to throw some food for thoughts in:



i had an old volvo 740 stationwagon. However, it had a 940 engine including transmission.

Now the tansmission was like this: Gears 1 to 4 had H-pattern, as million other cars.

But the 5th gear was activated with a switch. You had a switch on the center of the shiftknob. Depress clutch, press the button, and clutch in. Bam, 5th gear.

The transmission consisted of three intersections: the bellhousing, the transmissioncase with the 4 gears AND an additional "box" bolted to the transmissioncase. The propellershaft goes into that "box". A cable was routed from the 5th gear-switch to this box. When the 5th gear got activated, a big electromagnet got supplied with power. you get the idea.

btw, when we had to sell the car, it had over 300.000 kilometers on the clock, and that special 5th gear worked flawlessly.

ColinRX7

Your overall drive speed is determined by how many RPM the shaft is spinning.



1:1 ratio means the differential input is spinning at 9500 on a powerhouse rotary, and 1900 on a slugging diesel. So while you're going much faster than multi-lane highway speed (upwards of 100 mph? 9500 in 4th gear), imagine how fast that same car would go in 4th while only spinning 1900 RPM. 45 mph? Roughly?



I meant to point that out earlier to help show why trucks need more gears, but I left it out.

heretic

It's all about the powerband. Scaling up or down just helps to illustrate that a 1200 to 1900rpm powerband represents a roughly 60% increase in speed. That's actually pretty good.



Of course, it has been proven time and time again that a proper close ratio gearbox will benefit any engine, even stock low-performance street engines. It's one of the simplest ways to improve a car's acceleration, albeit oftentimes an expensive one.



I'm sure the truckers are not overly concerned with the quickest 20-60 times, but they would be concerned with getting the optimal fuel economy under all conditions, which makes it good to have a wide variety of gears to choose from so they can get their BSFC down. Even shaving a tenth of a MPG makes an enormous difference when you do well into the six figures per year and your clients are beating you up for the last penny per mile in shipping rates.

ColinRX7

And you're right. When you get 4 mpg, a slight increase is a huge difference. We have trucks in our fleet with 1,200,000 kms. 1999 model units. So mathematically very tiny increments in savings dictate thousands saved per year.



I was just trying to give some backround behind purpose for so many gears. Smaller trucks using diesel engines using common final drive ratios in differentials needed more gears to achieve highway speeds.



It's tough to work between economy, power and speed.



Now the differentials have splits for healthy balance between gears for economy, power, and speed (although some may not realize).



Older trucks have a big difference in speed between pulling 50,000 lbs and running empty. That's not fun especially, when empty, the truck takes five minutes to get between 80 kmph and 100 kmph. Right now we have new trucks in our fleet that you can hardly tell between empty and 100,000 lbs. And, barely slower than common low power econoboxes hitting the on-ramp (if, you can grab your gears fast enough that is).



Half of the fuel economy and performance improvements on large trucks has been with driveline modifications (over the years).



That said, both our posts point to a common conclusion. Driveline design dictates power, economy, and speed, just as much as the motor does. A strong motor design can be tweaked with additional focus on what puts the power to the pavement, and that was the purpose for shedding light on those who might not have ever thought about doing anything different to their driveline after building up their supermotor.

TYSON

Keep in mind you will be wasting A LOT of potential acceleration time just shifting gears. Formula 1 only uses 7 gears, even though they are computer shifted FAR faster than you can by hand.



Unless you are no-lift-shift-ing you will find you are spending an awful lot of time with your foot off the gas and it won't matter that you are staying in the powerband.



I'm not a truck driver, but I don't think too many of them hit all 18 gears on the way down the on-ramp.