# Dc motor help

Discussion in 'The Projects Forum' started by nitro22, Jul 8, 2012.

1. ### nitro22 Thread Starter New Member

Jan 26, 2010
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0
Hey guys I need little help on finding a electric motor that has plenty of torque and speed

I'm going to make a can smasher for my work as a gift

So it has to plug into a wall outlet and be able to have power to CRUSH

Any idea on what motor I should look for ??? Brand,house power

And I would like it to be medium size nothing to huge if u might have a nice one for sale please pm me

Last edited: Jul 8, 2012
2. ### #12 Expert

Nov 30, 2010
17,996
9,491
Well, judging by the place where you live, the required voltage will be xxxxx and the postage will be yyyyy. You'll need a Z:12.38A reduction drive or were you planning on making that part yourself?

3. ### nitro22 Thread Starter New Member

Jan 26, 2010
14
0
I'm from Ohio my zip code is 43452

So for now im looking for a heavy duty motor and once I find that I'll get a speed controller for it

4. ### #12 Expert

Nov 30, 2010
17,996
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Excellent. Your response means you should look first to find a speed controllable motor, then look for the controller. I expect a quarter horsepower will be quite sufficient, possibly even less. It depends on the gearing.
I'm not all that good with motors but you have now given enough information that we can help you.

Your title says, "DC" but you also said, "plug into a wall outlet". In Ohio, that's AC, 120 Volts. This will soon be resolved as somebody that knows about motors will arrive and find the information he needs.

You know that the first moment of the crush is the critical moment. (Once you get 'em started, they go much easier.) Do you have one of those wall mounted, pull the handle down, crushers? If you put a can in there and added weights until it broke the integrity of the can, we would know how much force is the critical amount.

I'm curious about this and will be watching. I hope you can get an automatic (gravity) feeder going, and an ejector. That would be way cool!

5. ### THE_RB AAC Fanatic!

Feb 11, 2008
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You could use a lever/linkage that gives high force low speed at the start of travel and less force but more speed in the later stage of travel.

6. ### nitro22 Thread Starter New Member

Jan 26, 2010
14
0
I don't no that much either so I needs AC then so it can be plugged into a wall outlet?? And be controlled by a controller

Also I no it does not take much force to crush a can I just don't no how fast a 1hp motor will move and do I really need gears ? That's why I want to make it with a speed controller so I can control how fast it crushes cans

7. ### strantor AAC Fanatic!

Oct 3, 2010
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One horsepower has the value of lifting 550 lbs, in one second, one full foot.

We can think of lifting, as crushing.

$power = \frac{force * distance}{time}$

$1 HP = \frac{550 lb * 1 ft}{1 sec}$, or $1 HP = 550 \frac{ft*lb}{sec}$

I just crushed a bunch of soda cans on top of a digital scale, by very slowly increasing my body weight on top of them. They ranged from 80lbs to 120lbs, with one ahead of the pack at 140lbs. So let's shoot for 150lbs.

A soda can is 4.8" tall. Lets say you want your crusher to crush 3 at a time. That's 14.4", or 1.2ft.

Let's say we want the cans to crush in 2 second max.

$\frac{150 lb * 1.2 ft}{2 sec} = 90 \frac{ft*lb}{sec}$

So, proportionally

$\frac{1hp}{550} = \frac{X}{90}$

$X = .1\overline{63}hp$, or ~11/64 HP

Get a 1/4HP setup and you should *theoretically* be fine. The problem in lies what type of linear actuator meets the speed and force requirements? I just checked here and didn't find any. All I see is high torque/low speed and low torque/high speed. No middle ground.
So, if you aren't willing to compromise for a painfully slow high torque model, you have a lot of mechanical engineering in front of you, designing a linear actuator.

I will wait to hear back before vomiting any more words and numbers.

8. ### strantor AAC Fanatic!

Oct 3, 2010
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What is your work? an office? a shop? Do they have compressed air?
This project could be done simply and effectively with a pneumatic actuator.
Your "speed controller" could be as simple as turning the dial on an air regulator.
Or if you're bent on integrating electrons, it could be as simple as potentiometer connected to a I/P transducer.

9. ### wayneh Expert

Sep 9, 2010
13,874
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I believe you could use a lever to achieve any ratio you want, or at least maybe 1:4 tor 4:1, depending on the lever arm lengths.

I recently tore apart a shredder that had a bad gearbox. I suspect you wouldn't have much trouble finding a shredder that needs a new purpose. A lot of the engineering and electronics in a shredder would apply well to this project. Power board with fuse, rectifier, IR LED for paper detection, motor reversing switch, indicator LEDs, all of those could apply. You just need a crushing action instead of the rotating knives.

10. ### strantor AAC Fanatic!

Oct 3, 2010
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Off hand I can't think of a good way to turn rotation into linear smashing, other than using a screw, which is how the linear actuators work, or pulling a cord. A cord could be wrapped a few times around the cans, or around a couple of sliding plates with cans between, and cinched up by the motor to crush cans. But that doesn't reverse nicely. Would take a lot of user interaction (PITA). Can you think of a way?

11. ### BillB3857 AAC Fanatic!

Feb 28, 2009
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To convert rotary to linear, a crank and connecting rod will work. Car engines just do the opposite.

12. ### #12 Expert

Nov 30, 2010
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I was thinking about a fairly large wheel with outside teeth driven and a cam welded on the face of the sprocket by using maybe a 1/2" wide strip of steel that is 3/16" thick. Whatever follows the cam, crushes the cans. With a cam, you can move slowly during the first part of the crush, then quicker as the needed force diminishes.

So, where to get a wheel with outside teeth? The flywheel off a car engine. A motocross motorcycle rear sprocket.

Arrange the cam follower to push on a lever with 1/3 to1 leverage and the wheel reduces to a rather small diameter.

Slowing the motor down enough is still not solved with this concept.

13. ### THE_RB AAC Fanatic!

Feb 11, 2008
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I'd go with the crank and conrod. You could get huge force at the start of the stroke to get the can crushing, then fast in the middle then big force again at the end of the stroke to complete the crush.

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14. ### #12 Expert

Nov 30, 2010
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I tried to visualize that as I was going to sleep but it wouldn't work because I was laying on my back. I had my frame of reference wrong.

15. ### BillB3857 AAC Fanatic!

Feb 28, 2009
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Get yourself an old lawnmower engine, cut opposite sides out of the cylinder, position piston at lower end of stroke, insert can, rotate flywheel one revolution, can falls out other side. (Watch out for your fingers)

16. ### THE_RB AAC Fanatic!

Feb 11, 2008
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Fantastic idea, apart from lawnmower engines typically have a stroke about 1.5".

17. ### DMahalko Senior Member

Oct 5, 2008
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This discussion is far too open-ended to know what the OP is really trying to do.

Some mechanical skill or knowledge will be needed, probably with access to machine tools such as a mill or lathe and the knowledge of how to use these tools without ripping your arm off.

If you want dirt simple with very little mechanical design, then, um... Use a low-torque motor to store potential energy in a weight, and release it when turned off.

Put a wide, flat, small-diameter drum pulley on the motor, as small diameter as will fit on the shaft, with large diameter flanges on edges of drum.

Attach a nylon rope or steel cable to the drum, with say a 50lb weight hanging on the cable.

Turn on motor, it lifts the weight until the cable is tight and the motor sits and hums.

Place can under the weight, turn off motor.

crunch.

This is super-simple but also super-dangerous, no safety controls, open design exposes people to serious injury if the cable breaks, etc.

The motor windings can overheat when stalled, and melt down.

If the cable breaks, it becomes a 6ft diameter flying weed-whacker and will maim anyone nearby.

Free-falling weight crushes.. your hand or foot...

18. ### shortbus AAC Fanatic!

Sep 30, 2009
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Best one I have seen is made of two wheels opposite each other. The gap is set to what size you want the can to end up. Cans were dropped between the wheels and that crushed them. Only one wheel needs to be powered. Think of a ball pitching machine, thats what it was like. The crusher was made to sit on top of a small (35 gallon) drum.

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19. ### wayneh Expert

Sep 9, 2010
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My dad used to describe how they made themselves a walnut crusher. Jack up the Model T truck. Mount a short section of old tractor tire to a board and place the car tire inside of it. Obviously they gave some attention here to the clearance between the Model T's wheel and the inside of the larger tire.

Then, just fire up the truck and pour walnuts through the clearance. Spend the rest of the day picking up shelled walnuts out of the yard.