Magic Wheel Calculations

[38flattie]

Last year I made a HUGE mistake in my gearing calculations, and I really don't want to repeat that mistake this year. Last year I used a computer program. This year, Stan Back was kind enough to send me a magic wheel!

I'm simply hoping someone can double check my numbers, so I don't end up under geared like last year!

I've done all the calculations at 5000 rpm, 28" tires, and Halibrand QC.

155 mph=2.8 gears
165 mph=2.55 gears
175 mph=2.4 gears


Am I figuring this right? Am I forgetting something that will effect the proper gear choice?

Thanks in advance!

[hotrod]

Am I figuring this right? Am I forgetting something that will effect the proper gear choice?

Tire growth at speed and a few percent slippage. You will go slower than the calculated speed due to slippage and faster due to tire growth.
Some say they just about cancel out but can't say for sure until you make a couple runs to see what your tires and driving style result in.

Larry

[desotoman]

Hi Buddy,

I come up with 148.75 for 2.8, 163.33 for 2.55, and 173.54 for the 2.4 gear set. YMMV. As said above tire growth vs slip plays a role also.

Good luck,

Tom G.

PS. At El Mirage my car ran 5700 RPM with 2.91 geared Q-change and ran 163.xxx which indicated I had no tire slip. Of course I did not have much HP either. LOL

[Bob Drury]

  Flatie, a couple of things to remember: your torque curve will be significantly less in high gear (or worse yet) overdrive with a moderate horsepower engine. 
  Secondly, remember that this is really a five mile drag race , this means that the quicker you get up to speed, the easier and faster it is to creep up to top speed as you get up to 1 to 1 gear ratio or higher with a overdrive.  It is a long, slow pull to the five if you have limited beans in the engine.                                                   Bob

[38flattie]

Bob, for me it will be a 3 mile race-I won't be able to qualify for the 5 mile.

On the low side I should have a little over 400hp, and on the 'hot' tune, a little over 500hp, if that helps at all.

[Bob Drury]

  Flatie, keeping in mind that your race car probably isn't as aerodynamic as a 53 Studebaker, Bruce Geisler who ran a 53 Stude on the salt for almost fifty years (YES FIFTY!) and has run and set records with it in many classes (and has one of the fastest one way times of over 242 with a twin turbo small block Chev from Gail Banks) says that a 53 Studebaker will go 200 with a 500 h.p. engine.
  Why not set that as your goal ?  I raced my Stude with a Early OLds engine for eight or nine years against brand new motors and accomplished more that I had expected out of a motor designed in 1946 and it made it all worth while.
                                       Good Luck,            Bob

[38flattie]

Haha!

Bob, our goal is to go as fast as the car will go! Realistically, I think that the 'brick' should go around 175-180, IF we can keep it together on the great white dyno.

I plan on starting with a mild tune, and working up gradually. I know some have urged me to just 'attack' the salt, but I'm comfortable with my plan. The reason I'm looking at gearing at different speeds is because of this plan.

[Glen]

Buddy, smart planning.

[BoredAndStroked]

I'm with Buddy - start conservative, figure out what the heck it is doing and then put a bit more tune to it.  Thank God that we spent time with Beck, all those dyno pulls and his knowledge gave us something to work from.  I'd love to see the car make it to 175, that was a number we've thrown around a lot.  Big white dyno, behind to us!

B&S

[jdincau]

"Add gear till it won't go any faster, then add horsepower"
Jack Costella

[Stainless1]

Your speeds match my calculator, with no slip.  Tire growth  may not be too much of an issue.  Your plan is good, you don't want to go home after only getting one run.... huh Bob, otherwise you will end up with a nickname.... 
Tom Burkland reminded me of one of those old Bonneville philosophies of land speed racing the other day....

if it spins the tires add weight, if doesn't spin the tires add nitro!

Just remember to have fun

[BoredAndStroked]

If it spins the tires add weight, if doesn't spin the tires add nitro!

Now that is good!