Author Topic: Noob here - Want to build ~10mph personal vehicle for 2 people. [Electric Motor]  (Read 1323 times)

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Offline jacksonTopic starter

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I want to build a small vehicle that can move 2 people at ~10 miles per hour.

I will be able to design the thing just fine, but I don't know anything about electric motors.

I want to use a Gas-powered Honda Generator ~120V (so I don't run out of fuel) to power a motor that's strong enough to move ~400 pounds total. - If this is just ridiculous, I would settle for using a car battery/s

All i need is a go button or switch.


Anyone have any ideas of what kind of motor I would want to get?  


edit:  it will probably have just 1 wheel in the back, and 2 in the front.
« Last Edit: February 17, 2010, 11:29:30 PM by jackson »

Offline Daanii

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How much money do you want to spend?

Offline Soeren

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Hi,

I want to use a Gas-powered Honda Generator ~120V (so I don't run out of fuel) to power a motor that's strong enough to move ~400 pounds total. - If this is just ridiculous, [...]
That IS ridiculous!
If you are prepared to put up with the noise of a generator, you'd be better off letting the generator drive the thing (remove the generator parts), or eg. a (Honda) 50cc 4-stroke engine.

By using a gas driven motor to generate power for an electric motor, you add conversion loss and complexity.


To move two grownups at 10mph, about 1hp/775W should be about right. 500W might just do it, but you don't wanna push it uphill I guess.
« Last Edit: February 18, 2010, 06:49:15 PM by Soeren »
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline madsci1016

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Hi,

I want to use a Gas-powered Honda Generator ~120V (so I don't run out of fuel) to power a motor that's strong enough to move ~400 pounds total. - If this is just ridiculous, [...]
That IS ridiculous!

If you are prepared to put up with the noise of a generator, you'd be better off letting the generator drive the thing (remove the generator parts), or eg. a (Honda) 50cc 4-stroke engine.


Actually, the Honda generators I'm sure he is referring to (the small red ones, I call them lunch box generators) are almost dead silent. I work with them all the time and forget to shut them off when I'm done because they are so quiet. They are the main power source for some of the autonomous robots I work with, and this idea is not so 'ridiculous'.

Most (all?) modern locomotives are Diesel-Electric driven; diesel generators powering electric motor driven wheels. Systems like this remove a-lot of moving parts, as they have no transmissions, clutches, etc to connect the power source to the drive train, and also get rid of all the fluid and maintenance that go with these systems. And, these systems are usually lighter.

The reason we have generator powered crafts is the control. Slow speed, accurate maneuvers (and fast speeds without 'shifting gears') are possible with a decent motor controller and motor. And while it's possible with a completely mechanical system to get such and effect, it comes at the cost of weight, more points of failure, and more preventative maintenance.

And for his project as a DIYer, It's easier to mount a electric motor to a wheel, wire a motor controller and generator then it is to fab linkage with support framework, mount a transmission, mount an engine, mount a gas tank and control system.
« Last Edit: February 18, 2010, 09:28:30 PM by madsci1016 »

Offline Daanii

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It does sound interesting to power your motors with a generator. For the motors, I suggest a total of about 2 to 5 horsepower. Either one motor on the back wheel or two motors, one on each of the front wheels.

If your budget is tight, you may look to scavenge a motor or motors from an electric wheelchair or electric lawnmower. Wheelchairs tend to top out at about 5 to 6 miles per hour. But if you increase the diameter of the wheel, you could use the same gearing and get your 10 miles per hour.

Using a system from an electric wheelchair may be easiest since it will give you the controller, the motors, and the gearing already put together.

Using a generator to produce 120 volts AC means you will need to convert that to (probably) 24 volts DC.

Offline Soeren

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Hi,

Actually, the Honda generators I'm sure he is referring to (the small red ones, I call them lunch box generators) are almost dead silent. I work with them all the time and forget to shut them off when I'm done because they are so quiet. They are the main power source for some of the autonomous robots I work with, and this idea is not so 'ridiculous'.
Well, he didn't specify what he had, so your guess is as good as mine.


And for his project as a DIYer, It's easier to mount a electric motor to a wheel, wire a motor controller and generator then it is to fab linkage with support framework, mount a transmission, mount an engine, mount a gas tank and control system.
Even an electric motor needs a transmission/gears, so whether you bolt one thing or another - no difference.
The gas tank he needs whether he use a genny or a motor - no difference.
A sprocket wheel is very easy to weld to an axle, whether the motor driving it is electric or gas driven - no difference.
Gas or electric, both needs a control system - no difference.
The dual conversion gas(electric model generates loss - big difference.

You have an opinion and so do I, but what it all boils down to, is the OP's mechanical savvy and the efficiency he wants.
I tried to give him something to base his opinion on.
What did you try, except to disagree with me (as so often before)?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline madsci1016

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Hi,

Even an electric motor needs a transmission/gears, so whether you bolt one thing or another - no difference.
The gas tank he needs whether he use a genny or a motor - no difference.
A sprocket wheel is very easy to weld to an axle, whether the motor driving it is electric or gas driven - no difference.
Gas or electric, both needs a control system - no difference.
The dual conversion gas(electric model generates loss - big difference.

Electric motors do not need transmissions and may have gears, depending on application / motor type. Gas tanks are integrated into the small Honda generators, which i'm going to assume he's using, unless he's trying to run a space heater on his cart. Electric control systems ( a speed pot and direction switch) are easier to mount then a throttle cable, and shifter with linkage to a transmission. There's not much loss in an electric system, only controllers that get warm and motors that are what, some where around 90% efficient? That can be easily argued this is negligible when you start considering friction loss in transmissions and linkage. Not to mention you only tried to defeat some of the advantages of an electric system.

And while you have your 'opinion' I have the experience and expertise of the billion dollar federal defense contractors that designed and built the generator-electric vehicles for the Department of Defense that I use every day. I think it's safe to assume they put a little effort into finding out which system has more advantages over the other.

Quote
You have an opinion and so do I, but what it all boils down to, is the OP's mechanical savvy and the efficiency he wants.
I tried to give him something to base his opinion on.
What did you try, except to disagree with me (as so often before)?

Wow, Apparently you feel I am out to get you. Well, don't worry, I'm not. The OP purposed an idea and asked a question, you attempted to shoot down the idea and call it 'ridiculous' (with not much proof other then 'it just is this way') before answering his question, and I provided some examples of engineering in existence ( and reasons ) that show his idea is practical (and give him examples to 'base his opinion on'), and has several advantages you may have not considered; after all, this is a discussion and I was adding to it. In fact, I never directly disagreed with your opinion (or called it a bad one), i just supported the OP's design.

I did not attack you ( as you did me now), nor belittle your opinion as 'ridiculous'. The fact that 'Soeren' was the author of the post didn't influence me at all in my posting. I wasn't 'out to disagree' with you, and for the sake of limiting flame, I won't discuss this anymore. I would have not posted this, however my motives for being an active participate in this discussion where called into question so I wanted to make mine clear.
« Last Edit: February 18, 2010, 11:12:07 PM by madsci1016 »

 


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