Retro Review: Hot Rod Calculator

 Retro Review:   Hot Rod Calculator

Quick Facts:

Model:  8703, Hot Rod Calc

Company:  Mr. Gasket Co/Calculated Industries

Years of Production: 2009 - 2020*

Memory Registers:  1

Batteries:  2 LR-44

Operating System:  Chain

Display:  8 digits, unit indicators 

New Price: $80 retail; can be found on sale or clearance

* I can no longer find the Hot Rod calculator as a new calculator on the Calculated Industries website.  However, the Hot Rod app for both iOS and Android.  

Ladies and Gentlemen, Start Your Engines!

The Hot Rod Calc is a specialty calculator that emphasizes on automotive mathematics, with solvers and applications including:  

*  Air Temperature, Relative Humidity (Moisture), Elevation

*  Vehicle Weight, Elapsed Time (1/4 mile traveled in seconds), MPH

*  Bore, Stroke, RPM, Torque, Engine Displacement

*  Tire Ratio, Gear Ratio

*  Engine Volumetric Efficiency

*  Carburetor Size

*  Vehicle Weight, Horsepower, Elapsed Time

*  Conversions including length, area, volume, temperature, mass, velocity (speed)

You can download a PDF version of the manual here: 

https://documents.holley.com/mr_gasket_instructions_hot_rod_calculator_8703.pdf

The manual has several reference tables:

*  Drag Coefficients depending on the automobile type

*  Holley Jet Chart

*  Jet Orifice Area Conversation Chart

Keyboard

The calculator comes in a bright red Armadillo Gear case.   The keys are bright and colorful, with most of them sporting a warm color palette (red, orange).  The keys are responsive, but have a rubber feel to them.  I believe the keys are made to handle dirt and oils given the target audience of the Hot Rod Calc.

The case has a quick reference guide.

Example Calculations

The calculator is set to U.S. units (default)

Example 1:

Calculate Air Temperature given:

Elevation:  1,284 ft

Air Pressure:  30.12 inHg

Humidity:  33%

1284 [ Elev/ADI ]

33 [ Moisture ]

30.12 [ Conv ] [Air Temp] (Pressure)

[Air Temp],  Result:  55.4211 °F

Example 2:

Find the weight of a vehicle given:

It's horsepower:  426 HP

It's elapsed time:  9.73 sec to run 1/4 mi

426 [ HP ]

9.73 [ ET ]

[ Vehicle Wt ],  Result:  1999.7337 lb

Example 3:

Find the speed, in miles per hour, for an automobile traveling with the following specifications:

1st Gear:  3.26

Final Drive Gear: 3.03

RPM: 5800 (revolutions per minute)

Diameter of the tires: 26 inches

3.26 [ × ] 3.03 [ Gear Ratio ]

5800 [ RPM ]

26 [ Conv ] [ Gear Ratio ] (New Tire Dia)

[ MPH ],  Result:  45.417902  mph

Verdict

If you are into racing, hot rods, and automobiles, and you need a quick mathematics tool, the Hot Rod calculator is worth the investment.  Its user manual is a well written.  Now may be the best time to purchase one before the calculator becomes a rare item.  

Eddie

All original content copyright, © 2011-2021.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author. 

HP 42S/DM42/Free 42: Auto Solvers

HP 42S/DM42/Free 42:  Auto Solvers

Introduction

This blog entry has four solvers for use the on the HP 42S (or Free42, DM42) in the subject of automobiles:

1.  Displacement, Bore, Strokes
2.  Gear Ratio, MPH, RPM
3.  Quarter Mile Estimation:  Elapsed Time, Car's Weight, Horsepower
4.  Tire Sizes

If you  are entering these programs by hand, I suggest that you create the needed variables ahead of time by storing an arbitrary value (it doesn't matter) into the variable.  Therefore when you recall the variables, they will be available in the soft menu.  Activate the solvers by pressing the orange shift key ([SHIFT]) [ 7 ] (SOLVER).

Link to the programs can be downloaded here:  https://drive.google.com/file/d/1N4wpO9Q-Mhyp51kdubAh5guf2xZhp8Tc/view?usp=sharing

1.  Displacement, Bore, Strokes  (File:  displacement.raw)

00 { 79-Byte Prgm }
01▸LBL "DISPMNT"
02 MVAR "DISPMNT"
03 MVAR "BORE"
04 MVAR "STROKE"
05 MVAR "#CYLIN"
06 PI
07 4
08 ÷
09 RCL "BORE"
10 X↑2
11 ×
12 RCL× "STROKE"
13 RCL× "#CYLIN"
14 RCL- "DISPMNT"
15 .END.

Variables:

(DISPM):  displacement of the a cylinder (cubic inches)
(BORE):  diameter of the cylinder (inches)
(STRO):  distance traveled by the piston (inches)
(#CYLI):  number of cylinders

Equation:

π/4 * bore^2 * stroke * #cylinders - displacement = 0

Example:

Bore = 4 in
Stroke = 3.5 in
4-cylinder engine

Result:  Displacement = 175.9292 in^3

2.  Gear Ratio, MPH, RPM  (File:  gearratio.raw)

00 { 74-Byte Prgm }
01▸LBL "GEARRTO"
02 MVAR "RPM"
03 MVAR "MPH"
04 MVAR "TIREDIA"
05 MVAR "GEARRAT"
06 PI
07 RCL× "RPM"
08 RCL× "TIREDIA"
09 RCL÷ "MPH"
10 1056
11 ÷
12 RCL- "GEARRAT"
13 .END.

Variables:

(RPM):  the tire's revolution per minute
(MPH):  speed of the vehicle (miles/hour)
(TIREDI): diameter of the tire (inches)
(GEAR):  gear ratio = transmission ratio * final drive ratio

Equation:

(RPM * π * tire_diameter) / (MPH * 1056) - gear_ratio = 0

Example:

RPM = 3,400 rpm
Tire Diameter = 28 in
Gear Ratio = 3.85

Result:  MPH = 73.5635 mph

3.  Quarter Mile Estimation:  Elapsed Time, Car's Weight, Horsepower
(File:  quartermile.raw)

00 { 52-Byte Prgm }
01 ▸ LBL "QRTMI"
02 MVAR "ET"
03 MVAR "WEIGHT"
04 MVAR "HP"
05 5.825
06 RCL "WEIGHT"
07 RCL÷ "HP"
08 3
09 1/X
10 Y↑X
11 ×
12 RCL- "ET"
13 .END.

Variables:

(ET): elapsed time for the car to travel 1/4 mile (seconds)
(WEIG):  weight of the car including passengers, drivers, fuel, and other items carried (pounds)
(HP):  horsepower

Equation:

(weight/horsepower)^(1/3) * 5.825 - elapsed_time = 0

Note:  MPH = (horsepower/weight)^(1/3) * 234 = 1363.05/elapsed_time

Example:

Weight:  3,540 lb
HP:  215 hp

Result:

ET: 14.8190
(MPH = 91.9802 mph,  [SHIFT] (TOP.FCN) ( 1/X ) 1363.05 [ * ])

4.  Tire Sizes (file name:  tiresize.raw)

00 { 87-Byte Prgm }
01 ▸ LBL "TIRESZE"
02 MVAR "SECWDTH"
03 MVAR "RIMDIA"
04 MVAR "ASPECT"
05 MVAR "TIREDIA"
06 2
07 RCL× "SECWDTH"
08 RCL× "ASPECT"
09 2540
10 ÷
11 RCL+ "RIMDIA"
12 RCL- "TIREDIA"
13 .END.

Variable:

(SECW):  section width (millimeter)
(RIMDI):  rim diameter (inches)
(ASEPC):  aspect ratio
(TIREDI):  tire diameter (inches)

On a side of a tire, we can get three of the four values by from a code that looks like this:

P235 / 75R17

P:  passenger car  (L for light trucks)
235:  section width
75:  aspect ratio
R:  radial tire
17: rim diameter

Equation:

(2 * section_width * aspect_ratio) / 2540 + rim_diameter - tire_diameter = 0

Example:  Use the stats of the tire above to calculate tire diameter.

Result:  30.8780 in

Source:

John Lawlor.  "Auto Math Handbook:  Mathematical Calculations, Theory, and Formulas for Automotive Enthusiasts"  HPBooks:  New York 1992  ISBN 1-55788-020-4

Eddie

All original content copyright, © 2011-2019.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.