Need 18V 1.5 amp motor having 200-400 maximimum RPM 1

[acesareking]

I need an 18V 1.5 Ah 27 Wh motor having 200-400 maximimum RPM with no gearing.
I can't find one to buy so is it possible to make one?
How would I make one?

 

[davidbeach]

If you have to ask...

To make one custom motor when you’ve never made one would be a huge investment.

 

[edison123]

Google pancake motors.

Muthu

http://www.edison.co.in

 

[Sparweb]

Your motor specs are nonsense.

From Hugh Piggott you can learn about both: Principles of electricity, and how to build custom motors with simple materials.

http://www.scoraigwind.com/

http://www.sparweb.ca

 

[waross]

Motor RPM is easy, cheap and light.
Motor torque is heavy and expensive.
Gears are your friend.
Use a gear-head motor and save yourself a lot of grief.
Cheaper, lighter, more dependable, easier to locate and buy.
Don't re-invent the wheel.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[dArsonval]

"Hey, can you send me the Association of American Railroads?"

And submit the specs on the Space Shuttle too. I'll need those.

Building a motor from scratch is certainly possible.

Here is a brief list of raw materials you'll want to seek out.

Silicon Steel Sheet. (Or a box of common nails.)

Electrical Insulation Material (Various kinds too numerous to list.)

Insulated Magnet Wire. (Numerous AWG sizes down to about a number 36.)

The above materials provide for the electrical aspect of your machine.

But! You'll also need the mechanical portions of your machine which consist of the rotating
elements. These items will have to be constructed from scratch as well.

You didn't specify if you want it powered with Direct Current, or Alternating Current.

An A.C. motor at the speed you're seeking would be physically larger in diameter
than a D.C. apparatus.

How would you make one?

For starters, you would consume everything you could possibly learn on the subject matter.
This exercise by itself will take a considerable length of time and study.

Once you've discovered you're not able to absorb all the facts and relationships
making up the [workings] of a motor, you'll look for compromises.

For your first step, I'd say you have started in the right place declaring your required operating voltage.

Soliciting or farming the Internet to help you with your objective (in a subtle way)
indicates your objective is possibly a passing pipe dream.

If you're up to the challenge though, get started on your motor.... get it to
turn, and come on back to this forum with some data, photos, and results of your attempt.

Then, maybe then...

John

 

[itsmoked]

Don't re-invent the wheel.

Let me correct that for you:

Don't re-invent mis-invent the wheel.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Thank you for the correction Keith. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ViCH]

If cost saving is not important, - I'll propose simple AC motor + VFD controller. Expensive, but quite accurate. And no gear, as U wish

Viktor
Electrical Technician II

 

[LittleInch]

Why no gearing?

What does it matter?

No mention of torque.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BrianPetersen]

Hmmm.

A 27 watt motor, if it were 100% efficient (which it won't be), is about 1/30 of a horsepower.

At 400 rpm that's about half a lb.ft of torque.

At a more senslble (and standard, on this side of the pond) 1750 rpm that's like a little more than a 1/8 horsepower motor.

So take an off the shelf 1/8 hp AC motor and drive it through a little VFD.

It will probably use more than 27 watts just to keep itself spinning, though, without even doing any useful work.

The fact that the cooling fan of that motor would only be running at a quarter of design speed might be a theoretical issue ... although perhaps the motor is running at such a low power level that it can't hurt itself.

As usual ... "more information, better answers"

 

[acesareking]

Hi Bill,

I see what you are saying and please correct me if I'm wrong but won't the use of a gearbox reduce the torque as well as reduce the RPM?

My understanding from what I've read online is that when a motor is designed with a low RPM then the torque is high at the low RPM, but when using a gearbox to lower the output RPM, the motor is still running a high RPM so torque will be low, right?

Sorry if my poor understanding is blinding me to the obvious here but what I want ideally is a low RPM output (say 100 RPM max)18V DC motor with a very high torque and I want the torque as high as possible at those RPM.

Is that available off the shelf, with or without gearing?

 

[EdStainless]

If you use gears to reduce the speed you are then increasing the torque. Aside for very small gearing losses the total power stays the same.
Sounds like a lot of missing pieces for this one.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[acesareking]

The post I'm using for reference is this:

https://www.reddit.com/r/askscience...o_electric_motors_have_maximum_torque_at_low/

Where the implication is that the design of the motor determines the RPM and the lower the RPM is, the higher the torque is.

My question is: By using a high RPM motor to drive a gear box I accept the torque will increase by using the gearbox but would the torque be greater if the motor was designed to be low RPM in the first place without the use of a gearbox?

To be clear, two identical motors, the first achieves 100 RPM through a gearbox and delivers maximum 10 ft lbs of torque, the second achieves 100 RPM by design without a gearbox, would or more spefically COULD the second deliver more torque, or could it only deliver the same torque as the first example?

 

[Compositepro]

A low rpm, high-torque electric motor will always incorporate gearing. This website is for engineers who would know that, and also know how torque, rpm, and power are related.

 

[EdStainless]

You can't create power from nowhere. While it is possible to build low speed high torque motors they are not a common item.
You have 18V, is it AC or DC?
You need 300rpm.
And you have a current limit (though that isn't what you have said).
Use that electrical supply and rpm to search for gear motors and see what you can find.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[ViCH]

Ed, he looking for NO gearing

Viktor
Electrical Technician II

 

[EdStainless]

No, he doesn't understand gearing. I am suggesting a solution method for the application.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[Compositepro]

Electric motors are basically electromagnets. There a physical limits to how much force can be created by an electromagnet of any given size and most motors are built to these limits to keep cost down. The only way to make a motor produce higher torque without gearing is to make it larger. So you can use a 100 hp motor with no gearing or a one hp motor with gearing. Which makes more sense?

 

[Bill West]

Hi Aces. Reddit just copies other forums, the catch is that some of those forums know less than you rather than more.

The "when a motor is designed with a low RPM then the torque is high at the low RPM" understanding you saw is a classic incomplete statement. It should have had "for the same horsepower" added to it.

Some basics:
Horsepower and watts are the same, just different units (like feet and meters are both length).
one hp =746 watts. (watts = volts x amps)

HP, torque and speed connect this way:
(torque in ft-lbs x speed in RPM) divided by 5252 = horsepower
You can turn the arithmetic around. But once you choose two of the figures, the third is dictated by the formula.
So:
a one horsepower motor designed for 1800rpm has 2.9 ftLbs of torque.
a one horsepower motor designed for 900rpm has 5.8 ftLbs of torque.

Gear boxes exchange speed for torque. 3:1 gears step the speed down to 1/3 and the torque up by 3x. The horsepower stays the same except for a bit of friction loss. A 1:3 box triples the speed but cuts the torque to 1/3.
If my one hp 1800rpm motor above is fed to a 2:1 gearbox it too will put out 900rpm and 5.8 ftLbs .


Your earlier posts suggested to me that you are trying to do an electric vehicle and have some golf cart parts. The motor/drive train that you have is as good as you are going to get. The existing controls for the motor are also the right choice. If you don't have them then maybe try the same source where you got the motor.

This forum supports high school and college education like yours but draws the line at actually providing it. We're more aimed at people who have completed their education and are having issues with their work, that's why some of the posts here have reacted with surprise. Your instructors should be directing you to books that match your needs.

Okay? Bill