Need Help With Calculating Torque/Speeds

[StormRyda]

Hey all...
I was just curious but would a 25 Volt Ac Motor be able to pull 50lbs...let so say on wheels? I dont have the exact motor specs but would this be achievable with a certain gear ratio or a certain circuit that could amplify the power going to the motor to lets say 30-40 volts? The actual base of the motor (not including the shaft) is about 3 cm long, 2 cm wide and 2 cm high? If so what sort of speed could be achievable...? Thank you for your imput.

The motor does work on both Ac and Dc...from an adapter...
So how many volts would i need in ac (from battery's) and then convert to dc to drive the motor faster.?

 

[Johnson777717]

Heya Storm:

I advise using gearing to achieve the necessary torque in order to pull 50 lbs. Ramping the voltage could work....but for a short while. If the motor is rated at 25 volts, pressing more voltage into the motor (lets say 35 volts) would eventually damage the motor itself. Thus, gearing the motor would be the best alternative.

Are you sure the motor is AC? I guess I'm confused about this statement:

So how many volts would i need in ac (from battery's) and then convert to dc to drive the motor faster.?

Most batteries that I know of, supply DC.

About the gearing: Using a single motor, There is a tradeoff that must be made between the speed and the torque output of the motor/gear box. For more speed, you'll have to live with less torque, for more torque, you'll have to deal with less speed.

A good place to start is to find what the motor RPM's are, at a given voltage/amperage. This should be the nominal values for the motor (25 volts and whatever amps the motor can handle). Knowing the RPM, you can approximate what kind of gear ratio you will need to provide a certain amount of torque.


Check this site out for a little bit on gear ratios and torque:
**broken link removed**

 

[StormRyda]

Well im not worried about speed at the moment.....basically the torque to actually try to move the object. I read the tutorial and that is a great source and helped me quite a bit.

Now is it possible to use lets say a 9 - Volt Battery and amplify its current non-stop to provide 24 Volts of power to the motor?

*The ac uptop was a typo.
*Convert To *Higher DC, Also a typo.

But the thing i also want to know is that will this Small motor be able to handle or even pull 50lbs at 25 volts and at the highest torque ratio? No part number or nothing on the motor.

 

[Optikon]

Well im not worried about speed at the moment.....basically the torque to actually try to move the object. I read the tutorial and that is a great source and helped me quite a bit.

Now is it possible to use lets say a 9 - Volt Battery and amplify its current non-stop to provide 24 Volts of power to the motor?

*The ac uptop was a typo.
*Convert To *Higher DC, Also a typo.

But the thing i also want to know is that will this Small motor be able to handle or even pull 50lbs at 25 volts and at the highest torque ratio? No part number or nothing on the motor.

If the battery can sustain a sufficient amount of current then probably the answer is yes. But, what needs to be figured out is how much current is required to generate the amount of torque needed?

The amount of torque needed can be figured out by how much force is needed to move your load at a certain speed. It is a mechanics problem.

Since you do not have any information about the motor, testing it would be a good idea.

 

[Johnson777717]

Let's address the actual speed control of the motor. If you supply the motor with 25VDC (assuming the motor is DC), you can adjust the speed (output RPM's) of the motor by using a potentiometer to adjust the amperage that is supplied to the motor. Without knowing the max amps the motor can handle, a little trial and error may be in store here.

Is there any way that you can find out the max ratings for the motor? Also, knowing the no-load RPM's, motor efficiency and torque would help.

Without knowing these variables, calculating the necessary torque, load-RPMs and possible gear ratios is simply guess work.

see this EVEN BETTER link for motor calculations. Reading therein will help you to better understand what is required to calculate what you're looking for.
**broken link removed**

 

[StormRyda]

Well the only information that i can seem to get is that between the 2 leads going from the motor: Positive and Neg their is a cap

This is the best i can read it
Their is a diamond ontop of the numbers
.1Z ?
25V

Would this indicate MAX 25 DC volts?


Also it says R.O.C Taiwan on it. I will try to get more information on it.

Also i dont seem to have a potentiometer.....

 

[Johnson777717]

I'm thinking that the .1Z is the amperage rating. I'm not sure where the Z comes into play. Does it possibly look like an "A"? If so, this is the amperage rating.

If this is the case, we have a 25VDC motor capable of handling 100mA of current. Again, if this is the case, 100mA is very small, especially if you want to move 50 pounds with it. The 100mA tells me that there isn't a lot of torque being produced by the motor, thus a gear reduction is needed in order to ramp the torque up at the loss of RPM's or the linear motion of the 50 pound object.

 

[StormRyda]

I am positive it looks EXACTLY like a z. Not even close to the letter A...



IT MAY be .12 or .1Z im guessing .12 with 25 Volts on it
Its a tantalum Cap



So what would happen if i desoldered this "cap" off the 2 leads? Could i replace it with a bigger one that lets more current in? This could burn out the motor...but still.

 

[StormRyda]

So basically lets say i replaced that tantalum with something that let in 5 Amps which would give me about 120 Watts which with the right gear ratio would be able to pull it. Could this small motor draw 5 amps from 24V or do i need to us a pent....to figure out and change the value?


Right now i can only be getting a MAX of 2 - 3 WATTS with the motor....i need way more.

 

[Johnson777717]

Well the only information that i can seem to get is that between the 2 leads going from the motor: Positive and Neg their is a cap

This is the best i can read it
Their is a diamond ontop of the numbers
.1Z ?
25V

Would this indicate MAX 25 DC volts?


Also it says R.O.C Taiwan on it. I will try to get more information on it.

Also i dont seem to have a potentiometer.....

I'm sorry Storm, I thought you were talking about the actual motor labeling, not the tantulum capacitor. Thus, please disregard my previous statement. Apologies.

 

[Johnson777717]

I have some discouraging news. Since the tantalum rating is 25 volts, the motor MUST be valued lower than 25 volts (possibly 12 volts). My reasoning here is that a manufacturer wouldn't place a capacitor which is rated for the same voltage as the motor. (25 volt cap and a 25 volt motor). If the manufacturer were to do this, they would have some law-suits on their hands because any voltage spike in the supply could rupture the capacitor due to over-voltage, and rupturing capacitors can be very volatile.

I guess you can try pumping 5 amps into the motor. 5 amps is a heck of a lot of current for a motor this size. To be honest, I wouldn't suggest any amperage above a couple of amps (if the motor can handle it). I would start with a low amperage (say 100mA) and slowly ramp the amperage up in 100mA increments or so until you achieve what you think is the best operating current. If you're not comfortable with this (I wouldn't be) I suggest taking it to someone who has experience with electric motors, who can tell you what the ratings are etc.

 

[StormRyda]

Alright thanks for the time

 

[StormRyda]

So what would be a good motor to find in a device that can push 50 lbs....does not have to be really big but a safe one that can handle more voltage..

 

[Johnson777717]

Well, let's work off of your 50 pound object. How do you want to move this 50 pound object? are you going to be sliding it across the floor, using a cable? Are you going to be lifting this 50 pound object up off of the floor?
Are you going to be using the motor as a drive motor for some sort of 50 pound vehicle? The reason that I am asking? The application is important to consider, especially when calculating the type of motor that you need. Lifting an object involves differently vectored forces when compared to driving an object with a motor, thus, we need to consider what forces will be working against the motor. Then we can effectively approximate the torque, RPMs, and power requirements for the motor.