Help selecting a electric motor

[bgoomba]

I am hoping to get some help from people who know things about electric motors. I know little to almost nothing with respect to electric motors and decided to seek some help on a project I am constructing.

Please forgive the rather mundane nature of this.

My 4 year old has decided she wants Ferris wheel for her barbies. Since I have been completely bored out of my mind of late, I decided to build her one. The further down the road I have progressed with my designs, the more extravagant it has become.

I have decided I want to motorize it. Right now, I have created a 6 seat barbie ferris wheel out of wood. It stands about 3 feet tall. Each seat can accommodate 2 barbies. It’s not overly heavy but being made out of wood it’s fairly substantial.

What kind of motor should I consider for turning it? I know that is a fairly 'general' question and may be hard to answer with the information I am providing. I would prefer something battery powered. It would not have to spin the ferris wheel very fast.

I do feel rather odd posting here but I had trouble finding a form that I felt could provide a decent answer.

It’s been a fun project. I am worried that if it turns out well that I may get other requests. Her favorite ride is the Tilt-a-whirl. Might have to turn down that request.

I have thought about creating a double ferris wheel though. Used to be one of my favorite rides at the county fair. Wonder if I would use 3 motors or 1 motor and gears to drive that sort of monstrosity.

Thanks for any help,
Steve

 

[jraef]

Don't use anything that can't be run on a couple of D cell batteries, otherwise you run the risk of having a pinch-point and hurting her. Erector sets used to have D cell powered DC motors like that, they would be perfect, but do they still sell erector sets?

 

[sreid]

My favorite was the Tilt-a-Whirl too.

Since you need slow speed and high torque my first thought would be a stepping motor. Simple amplifiers are cheap but you'd need to probably make a simple step generator (variable frequency square wave oscillator). Batteries are not a good choice; low voltage step motors require a fair amount of current but power supplies are cheap and safe.

 

[bgoomba]

jraef,
Thanks. I have been looking around for motors to purchase on line. The problem I am running into is I am not sure what to buy. Most of the motors I run across have lots of interesting specs but being electric motor handi-capped, I have no idea what kind of motor can be powered by D cell batteries.

Here are some examples of items I would consider:

http://www.hobbyengineering.com/SectionM.html

http://www.hobbyengineering.com/H2242.html

Can I hook these up to D cell batteries?

 

[bgoomba]

If I went with a stepper motor, how would I go about powering it? 12 or 24 volts dc are required for the motors listed at the site below.

Cheap stepper motors:

http://www.futurlec.com/StepperMotors.shtml

Which of these do you think would be adequite power wise?

 

[sreid]

Here's a link to step motor selection at

http://www.digikey.com

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=983126;keywords=step motor

I'd select 5 VDC and unipolar. With some clicking you can get to the catalog page that also has a step motor driver.

You can also find powersuplises at Digikey.

 

[itsmoked]

You understand that it's you that wants a motor. A kid would be happy with a a hand crank. Possibly happier.
Speaking from l o n g experience I think you're making a mistake bringing power cords/batteries/switches pinch points into a neat Ferris wheel project for a young child.

But I guess if you are driven to repeat my mistakes what you need is a model gearmotor. Many of them come in different ways. I have one that has 4 planetary gearboxes that you could assemble and stack the gear boxes to change the ratio or final shaft speed. You could go clear down to seconds-hand speeds. I can't remember the name of the kit but here is a an example that would likely work fine for your application.

http://scientificsonline.com/product.asp_Q_pn_E_3039118

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

How about adapting a cordless drill? Torque limiter built in, geared down nicely, fairly cheap.


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

I think the gearmotor picked out by itsmoked is exactly what I had in mind when I said an Erector Set motor (who, by the way, is defunct). Small, simple, inexpensive, low risk of injury (assuming you encase the gearbox) and can be powered by batteries so low risk if electrical malfunction that could start a fire or injure the child. Steppers require power supplies, i.e. plugged into the wall and programming that may or may not provide adequate mechanical injury protection: you won't know for sure until it happens. Big dangers with kids.

Cordless drill would also be workable, they can be had fairly inexpensively now and provide inherent rechargeability. Might be a little more difficult to implement IMHO than that hobby gearmotor and a 12-18V drill battery can more easily start a fire than a pair of D cells.

But all in all, I also agree with itsmoked about the hand crank issue. I too had a tendency to apply engineering solutions to things I made for my kids; most of the features and benefits were lost on them because a) they just wanted to fill a basic need and/or b) if it didn't come from a store or have the right label on it, it was "lame" according to my daughter.

 

[jraef]

By the way bgoomba, save all the relevent links ASAP. Sooner or later someone is going to recognize this as a hobby post and flag it for deletion.

Sorry, dem's da rulz.