Max Wheel Radius on Inclines w/ Torque & Speed

[Jones1987]

Hi,

I have a set of data which indicates the maximum radius of the wheel a vehicle can move before it begins to stall.

For example if I have an incline of 10 degree and at 50 RPM / 2Nm my max wheel is 2m.
Then I have an incline of 15 degrees and at 30 RPM / 2.5NM my max wheel is 2.5m.

Does this mean, if I picked a wheel radius of 2m would my vehicle stall at 10degree at a speed of 50RPM, or would it slow down to 30 RPM and be able to climb the higher incline?

If this is not fully clear please mention, it may seem a simple thing to some of you, but I can't to get my head around it. Do DC motors stay at fixed speeds and torques, or do they drop and torque increases?

My assumption is the motor will slow down and produce more torque until the speed reached zero. But it would be helpful for someone to clarify this for me.

Thanks.

 

[Unrest]

Hi,
For example if I have an incline of 10 degree and at 50 RPM / 2Nm my max wheel is 2m.

How is the RPM being used? There'll be a minimum torque required to climb a hill with a particular gradient and vehicle weight. I don't see how RPM is involved unless the formula also considers some other effects besides gravity.

My assumption is the motor will slow down and produce more torque until the speed reached zero.

For a DC motor, yes.

 

[Jones1987]

Well, I have table data with the torque values at certain RPM. So looking at the table, as the RPM decreases the torque increases which means higher maximum wheel radius.

So if I have a speed in RPM, with a torque value. And the max radius at this point is 2m, but at a lower RPM with a higher torque the max radius increases. My question is, at a certain incline, does the motor realize it requires more torque and begins to slow down. Or does the motor only stick at a specific RPM range depending how much load it is carrying?

 

[jack action]

The maximum incline you can climb is related to the maximum friction force that the wheel can handle. Once you know that force, then wheel torque = friction force X wheel radius.

See http://hpwizard.com/car-performance.html" for more info (Go at the bottom of the page: Theory »» Longitudinal acceleration »» Hill climbing).

 

[Unrest]

does the motor realize it requires more torque and begins to slow down. Or does the motor only stick at a specific RPM range depending how much load it is carrying?

Yes to both. It'll slow down when more torque is required. Also, its RPM is determined by how much load it's carrying (ie torque) - climbing the hill counts as a load.