Calculating Torque for a 24in Single Wheel Vehicle

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Discussion Overview

The discussion revolves around calculating the torque required for a single 24-inch wheel vehicle weighing 150 lbs to achieve a top speed of 25 mph in 5 seconds. Participants explore various aspects of the vehicle's design, including the use of hydraulic motors and the implications of different power sources.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to determine the torque needed for their vehicle, having calculated a wheel revolution rate of 350 RPM but unsure of the torque in ft-lbs.
  • Another participant questions the context of the inquiry, asking if it is for schoolwork and whether the 150 lbs includes the rider.
  • Some participants discuss the choice of a hydraulic motor, with one expressing a preference for gas or electric motors instead.
  • There is a calculation presented by a participant that results in a torque value of 2112 ft-lbs, which they later question as being too high.
  • Another participant provides an alternative torque estimate of about 35 ft-lbs and suggests a minimum of 5 hp motor considering inefficiencies.
  • Concerns are raised about the vehicle's stability at higher speeds, with suggestions to limit the top speed for safety.
  • Participants discuss the design features of the vehicle, including remote control capabilities and the use of a variable displacement pump for speed control.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate power source for the vehicle and the calculations related to torque and horsepower. There is no consensus on the correct torque value, with multiple calculations and estimates presented.

Contextual Notes

Participants mention various assumptions in their calculations, such as the weight of the vehicle and the method of acceleration calculation. Some calculations may depend on specific definitions or interpretations of torque and horsepower.

Who May Find This Useful

This discussion may be of interest to individuals involved in vehicle design, particularly those exploring the use of hydraulic systems, as well as those interested in torque calculations for engineering projects.

Inventermark
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Need torque for single 24in wheel vehicle weighing 150lbs to reach top speed of 25 mph in 5 sec. So far I have got wheel rev of 350 per minute but not sure of torque in Ft lbs
 
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Inventermark said:
Need torque for single 24in wheel vehicle weighing 150lbs to reach top speed of 25 mph in 5 sec. So far I have got wheel rev of 350 per minute but not sure of torque in Ft lbs
Welcome to the PF.

What is the context of your question? Is it for schoolwork? And is the 150 pound weight a total weight including the rider? Must be a light rider on a Fixie...? :smile:
 
berkeman said:
Welcome to the PF.

What is the context of your question? Is it for schoolwork? And is the 150 pound weight a total weight including the rider? Must be a light rider on a Fixie...? :smile:
Wanting to make a self propelled wheelbarrow type vehicle, wanting to figure out what size engine and hydrolic motor to power it.
 
Given a speed and time, do you know how to calculate the required acceleration? Wolfram Alpha could give you some convenient back-of-the-envelope calcs: http://www.wolframalpha.com/input/?i=24mph+in+5s

Why are you planning to use a hydraulic motor?
 
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Mech_Engineer said:
Given a speed and time, do you know how to calculate the required acceleration? Wolfram Alpha could give you some convenient back-of-the-envelope calcs: http://www.wolframalpha.com/input/?i=24mph+in+5s

Why are you planning to use a hydraulic motor?
Want to be remote controlled. And already have electronic seloniod, for that
 
Is it a solenoid with proportional control? How will you control speed? Hydraulic drive systems also need cooling heat exchangers, will you have one of those as well?

It seems obvious to me you should be using gas or electric motor but anyway...
 
Mech_Engineer said:
Is it a solenoid with proportional control? How will you control speed? Hydraulic drive systems also need cooling heat exchangers, will you have one of those as well?

It seems obvious to me you should be using gas or electric motor but anyway...

Yes, will have variable displacement pump, with electric control want to power it with gas engine, but need to know torque value to order hydrolic motor, and to size engine.
 
So let me ask, why not drive with the engine itself rather than adding the complexity of a hydraulic drive system?
 
Inventermark said:
Yes, will have variable displacement pump, with electric control want to power it with gas engine, but need to know torque value to order hydrolic motor, and to size engine.

So far I have got acceleration as 7.04 ft/sec that times mass should give me torque, at 2112 ft lbs that times rpm of 300 is 633600 divided by 5252 should give me HP of 120.6? That seems high to me. I was thinking it would be closer to 12 HP... Did I do something wrong?
 
  • #10
Mech_Engineer said:
So let me ask, why not drive with the engine itself rather than adding the complexity of a hydraulic drive system?
So what I am building is a powered wheel to drive a wheelbarrow type vehicle that already has two fixed wheels in front, my power unit will mount behind and needs to have variable speed and steering up to 180 degrees and wireless remote control. I am using a variable displacement pump because I can control it with an electric actuator, and also use an electric motor to run a gear or sprocket for turning the power wheel.
 
  • #11
Inventermark said:
So what I am building is a powered wheel to drive a wheelbarrow type vehicle that already has two fixed wheels in front, my power unit will mount behind and needs to have variable speed and steering up to 180 degrees and wireless remote control. I am using a variable displacement pump because I can control it with an electric actuator, and also use an electric motor to run a gear or sprocket for turning the power wheel.
Using common automotive remotes give easy control to the electric motors and the hydrolic pump provides the transmission and cluch allowing me to be not have to control engine speed.
 
  • #12
I would recommend you don't make its top speed nearly so fast, rear-steer reverse tricycles are nimble but will have dynamic stability issues. I'd be hesitant to take it faster than 5 mph, are you building this thing as a go-kart or wheelbarrow for hauling stuff?
 
  • #13
Mech_Engineer said:
I would recommend you don't make its top speed nearly so fast, rear-steer reverse tricycles are nimble but will have dynamic stability issues. I'd be hesitant to take it faster than 5 mph, are you building this thing as a go-kart or wheelbarrow for hauling stuff?
As a prop, will have a lightweight plastic cover that makes it appear to be a cow. I am trying to keep the weight very low to the ground to help with stability, would be interested in making it electric, but don't have much experience in that area, it will only need to operate for 3 min or less not sure of the size battery needed for that.
 
  • #14
I will try to upload some basic plans
 
  • #15
Trying to upload a drawing..
 

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  • #16
Inventermark said:
So far I have got acceleration as 7.04 ft/sec[2] that times mass should give me torque, at 2112 ft lbs...
This torque is way too high. Show your work.
 
  • #17
http://www.wolframalpha.com/input/?i=24mph+in+5s

Is where I got my acceleration from, my weight is 150 lbs

Torque= acceleration x mass

I am just trying to get a ball park idea of torque needed to drive wheel and HP needed in order to size motor and gears.. Can someone give me the correct values?
 
  • #18
I get about 35 ft-lbs torque at the wheel, 2.3 hp. With inefficiencies, I'd use at least a 5 hp motor.
 
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  • #19
Thanks! Insightful you are the bomb! I was not really looking for a class on (how to) as much as the answer so I could continue my build. Thanks so much for your help!
 

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