Author Topic: Selecting gear ratios  (Read 13741 times)

0 Members and 1 Guest are viewing this topic.

Online Dynoroom

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 2192
Re: Selecting gear ratios
« Reply #30 on: October 07, 2015, 10:00:39 AM »
And yet Sparky has a "blue" hat, to go along with his red & Merlot.........

He must be doing something right........ 
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: Selecting gear ratios
« Reply #31 on: October 07, 2015, 10:32:19 AM »
IO
In my opinion you have to gear for the speed you need with the best TE combo for that speed

I ran 305 out the back with 28" tires at 7800+ 2000 rpm above peak torque. Back up run  I pulled the OD 1/3 mile form the trap--- it would not pull OD --it nosed over and hence my 299 red hat

I went back home and played with the charts and figured out I could get 17ft # more TE by going town to 24" tires in od #  went back next month and it ran 307 and 309 out the back  for a 305 avg at about  6850.

In my opinion you have to gear for the speed you need with the best TE combo for that speed.  I now have some 23" tires that I will try to bump Seths record.  the puts me slightly down the torque curve but up in TE because of the smaller tire.
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline RebekahsZ

  • Full Member
  • ***
  • Posts: 55
Re: Selecting gear ratios
« Reply #32 on: October 07, 2015, 01:26:12 PM »
Thanks, SPARKY.  I'm new to this...specifically what does "out the back" mean?  I'm serious, I'm still learning the lingo.  300-damn that's fast...fortunately, I'm gonna be a concrete/asphalt landspeed racer since I'm way out here on the eastern side of the nation and the past two salt events that I have tried to attend have been weathered-out.  My lifestyle/marriage isn't compatible with something so unpredictable when it comes to budget and schedule.  So, I'm looking at Wilmington and Loring for my experiences.  So, I have 1 to 1.5 miles to get it all done.  My one toy car will be serving me for landspeed, autocross, drag racing and even some commuting when it isn't broken.  The only other car I own or have time and space for is my truck.  So there will be constant set-up changes and a lot of compromises.

Offline Interested Observer

  • Sr. Member
  • ****
  • Posts: 433
Re: Selecting gear ratios
« Reply #33 on: October 07, 2015, 01:39:11 PM »
So---Sparky (reply #31) unwittingly demonstrates that power cleans torque’s clock.

He runs 305 at 2000 rpm above torque peak, which would put it near the power peak.
He then invokes overdrive to bring the revs back down to the torque peak and GOES SLOWER.

He then changes gearing and runs 305 at 6850 rpm, 1000 rpm above torque peak but again climbing up the power curve.  Note how the best speeds were achieved at revs well beyond the torque peak, and consequently, the tractive effort peak.

Q.E.D.

Imagine what he could do if he just geared for peak power!

Next try is with smaller tires, which will put him yet further up the rev range, further from peak TE but closer to where the power presumably is.

Sparky, join the rest of the world!!  It’s simpler and more effective.

Offline turborick

  • Full Member
  • ***
  • Posts: 202
  • Go as fast as we can with as little as we can
    • http://www.bonnevillestreamliner.com
Re: Selecting gear ratios
« Reply #34 on: October 07, 2015, 01:57:28 PM »
So---Sparky (reply #31) unwittingly demonstrates that power cleans torque’s clock.

He runs 305 at 2000 rpm above torque peak, which would put it near the power peak.
He then invokes overdrive to bring the revs back down to the torque peak and GOES SLOWER.

He then changes gearing and runs 305 at 6850 rpm, 1000 rpm above torque peak but again climbing up the power curve.  Note how the best speeds were achieved at revs well beyond the torque peak, and consequently, the tractive effort peak.

Q.E.D.

Imagine what he could do if he just geared for peak power!

Next try is with smaller tires, which will put him yet further up the rev range, further from peak TE but closer to where the power presumably is.

Sparky, join the rest of the world!!  It’s simpler and more effective.


I agree gear for peak Power.
Torque gets you going off the line HP give you the MPH
Rick Yacoucci

The new Nebulous Theorem 3.5 #788
http://www.bonnevillestreamliner.com

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: Selecting gear ratios
« Reply #35 on: October 07, 2015, 02:33:38 PM »
  ---that is why RPM has equal value in the HP formula

When I work with a eng.  builder  I am willing to give up a little HP if I can move the torque curve up more or keep it from looking like falling of a cliff.

R-Z 

At Bville there are 3 timed miles at the beginning of the 1st timed mile the 2 mile mark, there is an entry speed 1/4 mile long timing trap---we call it "entry" or "1/4 speed"   at the end of the 3rd time mile which is at the 5 mile mark there is the standard 132' timing trap that gives you your terminal velocity speed as opposed to your avg speed for the last timed mile. We call this "out the back door"  . When B'ville racers are talking to fellow racers lots of times the leave the hundreds number off.  Ie he did 9 out the back or something like he was running   in the mid 70s  and it is up to you to know the class and guess if they meant 170 270 or 370

The entry and exit speeds are to help the racer try to figure out what he and his car or getting done!!!!!!

FB  said it all ---read, reread and learn and use what he is putting down---I learned to use TE selling trucks it let me compare one drive train to another in working with a customer ---FB has been using it at the race track for years-but the dyno sheet with a good Excell "dream Sheet" will help you understand what you need to do to get there--------THE FUN IS IN THE JOURNEY   

LSR is a wonderful addiction that leads to a sickness--- SALT FEVER for which there is no know cure!!!! and becomes a lifestyle!

Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!