Engineer Dopers and Guitar Geek Dopers - small electric motors?

[Ogre]

OK, so I’ve been drooling over rotary speaker cabinets recently. I’ve really been wanting that 3D, rotary pulse sound. Think Leslie speakers. Think Stevie Ray Vaughn. Think Booker T and the MG’s. That sound.

Leslies are usually vastly expensive, however. But what’s this? I found a guy who wanted to sell his Little Lanilei rotary speaker cabinet for a very small amount of money. Awesome!

So I just got it today, and it kinda sucks. The rotating cone is cheap and poorly designed, so the tremolo effect is not very clean, deep, or pronounced. And it takes FOREVER for it to spin up to speed, and then stop again. Unacceptable. Hell, half the fun in a rotary sound is being able to change tremolo speeds on the fly, or stop them suddenly.

But I don’t think I’m going to be able to send it back. So I was thinking, why not make it a project? Make it rule.

So I want to redesign the cone. Not a huge deal. I can do that out of a cylinder of styrofoam and a sharp knife. I’m SURE I can make a better cone than the thin, chintzy one they made.

But here’s the problem: I don’t know much about small electric motors. But I kinda know what I want. I want a small (probably 9V) electric motor that runs at low speeds (I don’t want to spin a propeller. I just want to spin the cone at up to a few hundred RPMs. I also need it to have adjustable speed, and (important, I think) higher torque. I need it to be able to start and stop much faster, and change speeds fairly promptly.

So you engineers and guitar/organ/Leslie folks: ever taken something like this on? Are there any good sources for small electric motors that would fit my needs? Any ideas?

[Grumman]

You may want to use a gearhead motor. Compared to a normal motor of the same size it would be slower and have a higher torque. Depending on how much torque you need, you can still get them for under $20.

[Quasimodem]

I can’t offer anything but a brothrrly slap on the shoulder or a ^5 from another guitarist, but just reading the description of what you want to do, impresses the hell out of me, Ogre!

I’m getting all kinds of “confident” vibes from your words, and when you get that thang built, I know it will be just what you want, man!

Best Wishes

Q

[HongKongFooey]

@Ogre

But here’s the problem: I don’t know much about small electric motors. But I kinda know what I want. I want a small (probably 9V) electric motor that runs at low speeds (I don’t want to spin a propeller. I just want to spin the cone at up to a few hundred RPMs. I also need it to have adjustable speed, and (important, I think) higher torque. I need it to be able to start and stop much faster, and change speeds fairly promptly.

I think a stepper motor would suit your application except the ones I’m familiar with have very low torque ratings, especially at higher speeds. Is the cone hard to get moving? Steppers are good at changing speeds and moving to the correct position, not so much at producing torque.

[Tuckerfan]

You might want to do a search over at instructables.com as someone there has probably done something similar and will have published part sources in their instructions. If nothing else, it might give you a few pointers on how to do it. A lot cheaper to learn from someone else’s mistakes than your own.

[Ogre]

@Grumman

You may want to use a gearhead motor. Compared to a normal motor of the same size it would be slower and have a higher torque. Depending on how much torque you need, you can still get them for under $20.

Awesome! The price is right, too. I Googled for these, and they seem to be a good choice. It looks like I can get them rated at 12V. I really kind of want to use the standard 9V Boss-style transformer already installed. Do you know if these motors will crap out if somewhat starved? Also, how do I get an idea of the physical dimensions of it?

I can’t offer anything but a brothrrly slap on the shoulder or a ^5 from another guitarist, but just reading the description of what you want to do, impresses the hell out of me, Ogre!

I’m getting all kinds of “confident” vibes from your words, and when you get that thang built, I know it will be just what you want, man!

Best Wishes

Thanks, man. I appreciate it. But don’t be too impressed. This actually should be quite a simple project. Not rocket science at all.

I think a stepper motor would suit your application except the ones I’m familiar with have very low torque ratings, especially at higher speeds. Is the cone hard to get moving? Steppers are good at changing speeds and moving to the correct position, not so much at producing torque.

Well, I really need quick acceleration from full stop, and the ability to immediately go from high speeds to low speeds (and back). Will a gearhead or stepper (or something else) do this best?

You know, I was screwing around with my adjustable speed drill last night and thinking “If this weren’t so noisy, something like this would be perfect. High torque, so it has quick spin-up from full stop, the speed is more or less infinitely adjustable up to its max speed, and it stops immediately.”

So I guess I need it to be silent (or close to it) as well. Not asking for much, am I?

Edit: Re: the cone. It shouldn’t be difficult to get moving. While it is quite wide compared to the shaft, it’s light. I was thinking of building a cone from a piece of light styrofoam or balsa.

You might want to do a search over at instructables.com as someone there has probably done something similar and will have published part sources in their instructions. If nothing else, it might give you a few pointers on how to do it. A lot cheaper to learn from someone else’s mistakes than your own.

Will do. Thanks for the advice!

[Kevbo]

Source for cheap surplus motors, including some gearhead motors. Note that the link above is to page one of four.

ETA: Same source has a good selection of speakers as well.

[Ogre]

@Kevbo

Source for cheap surplus motors, including some gearhead motors. Note that the link above is to page one of four.

ETA: Same source has a good selection of speakers as well.

Awesome. That will help. I’ve found out that the max RPMs of the old Leslies were about 350-ish RPMs, so I’m shooting for that general range.

[Grumman]

@Ogre

Awesome! The price is right, too. I Googled for these, and they seem to be a good choice. It looks like I can get them rated at 12V. I really kind of want to use the standard 9V Boss-style transformer already installed. Do you know if these motors will crap out if somewhat starved? Also, how do I get an idea of the physical dimensions of it?

When I’ve used them, I’ve used variable voltage to control the speed and torque. 0-9 Volts would work fine as long as you don’t make it push too much weight around, it would just be a bit slower than if you were running it on 0-12 Volts. As for the dimensions, if you have a particular store in mind, they might have the specifications on their website.

[CookingWithGas]

I don’t know about the motor but all the cone redesign in the world won’t help you if it’s a shitty voice coil. I hope you don’t spend a huge amount of time on the motor aspect and then still get unusable tone…

[Snowboarder_Bo]

When I lived in the Orlando area, my girlfriend (at the time) took me to what is now one of my favorite places in the world. It’s a great source for all kinds of electronics.

Skycraft Parts & Surplus

[WordMan]

Subscribing to this thread, sir - do keep us posted!

(and no, I don’t think I could be more clueless in regards to your questions - sorry)

[DanBlather]

Go to a Goodwill or other used goods store and buy an old sewing machine that has a footpedal. Take it apart and use the motor and footpedal. I’ve done this a couple of times for spnidle winders and each time it cost less than $20. Lots of tourque and variable speed.

[Ogre]

@DanBlather

Go to a Goodwill or other used goods store and buy an old sewing machine that has a footpedal. Take it apart and use the motor and footpedal. I’ve done this a couple of times for spnidle winders and each time it cost less than $20. Lots of tourque and variable speed.

Oooooooh. Dang, that’s a good idea. Thanks!