Imagine you have a cordless tool that is held like this dude is holding this massive spoon/paddle:



The application is not cooking related; it is more of a handheld agitator (think paint mixer) about 12ft/4m long that you stick down into a big tank.

I want to have proportional speed control like a cordless drill, but the form factor is different and a trigger just doesn't seem to make much sense.

So what would you recommend? Slider pot?

 

ooh. I think a twist grip like a motorcycle

 

As cool as that sounds, I'd make sure that whatever you choose is resistant to normal hand movements by the operator. For instance my bicycle used to have grip shifters. That was just fine most of the time but would often cause a gear change when I hit a large bump. My hand had to stay on the grips, so there was no easy way to avoid that. Now I have paddle shifters and they NEVER misfire.

Rotary mixers are prone to harmonic motion - perfectly smooth at one speed but wildly oscillating at another. Whatever you choose should allow adjustment while running so the operator can easily get smooth spinning.

 

My first thought would be a twist grip, too. But I wouldn't have it so that the person has to hold it in position at the same time they are also using the thing to stir something, especially if there's much force involved. How about a knob at the top that the person could easily turn with their thumb and forefinger that would then stay in that position when they remove their fingers back to the normal position. Of course, what you give up relative to the motorcycle throttle-like approach is if the person lets go, the thing would automatically stop. But that could be dealt with (if it was a concern) by putting a sensor in the handle that detects if the person is holding it. Lots of ways to do that.

Another approach to speed control could be a couple of buttons or push sensors that, perhaps, lay under the index finger and the little finger and the person pushes the index finger to speed up and the little finger to slow down. You could make it so that it speeds up in increments each time the button is pressed, or that the speed ramps as long as the button is pressed. You would need to make the activation force high enough (or maybe position the buttons away from the fingers so that the operator has to move a finger sideways a bit to activate it) so that unintended activation didn't happen easily.

 

A point of caution if the paint mixture uses a combustible ingredient! A brush type motor would have internal sparks that might ignite such a vapor. So I suggest an air driven tool for safety. In addition, the possibility of accidentally dropping a battery tool into the tank is very real. And the final caution is based on what I saw many years ago, which was exactly such a device, but on a smaller scale, used with an electric drill motor to stir a gallon can of paint. NEVER have the tool sinning prior to immersion in the tank, or paint can. A spinning mixer blade is quite a wide-angle paint sprayer.

 

"siri, can you turn a bit faster?" - my tongue-in-cheek response.

 

I couldn't find a twist grip that would fit a 3/4" pipe so I ended up going with a trigger. I used this one and I made a (pretty)-dimensionally-accurate 3D model of it that you can find here, in case anyone needs it.

 

At the foot?

 

At the foot?

Huh?

 

Huh?

A foot control like a welder or sewing machine.

 

A foot control like a welder or sewing machine.

You beat me to it. But I was also thinking that since this is going to be a battery powered tool, a foot pedal wouldn't be a reasonable approach.

My deWalt 20VDC drill has two speeds selected by a sliding switch that engages different gears for high or low range of speeds and torque. I often use a much smaller mixer to stir my paint, but the drill itself has a variable speed trigger. I'm unfamiliar with exactly how they achieve the variable speeds, it may be some form of PWM or possibly a brushless DC motor driver with variable speed capability.

Can't give you a good answer as to how to approach your project but perhaps this might spawn some new direction of thinking.

 

It seems like supporting a suitable battery for a larger device would be a real pain after a while. So I would choose a mains powered mixer, and with a power cord anyway, a foot operated speed control might work out well. But as we have no hint as to how much effort it actually requires, a trigger control of some kind might also be OK.

 

It is already made. I used a variable trigger like a cordless drill has. That is what post #7 was about. It is actually a long-reach rotary brush tool for cleaning a gasket in the bottom of a bulk tank railcar so a guy doesn't have to do all the confined space entry stuff and get inside to scrub it. I chose to describe it as an agitator because I felt that conveyed the concept with fewer steps, less explanation. Very few people would be able to visualize what I would be talking about. But now I have pictures.

 

THAT is a brilliant idea. Not only will it be faster, but it avoids the closed space hazard issue very well. If it works out you will get thank-you's from the safety folks and the union folks and the foreman that manages the cleaning operation. But your power head may need a spotlight so that they can see the tank drain ports.

 

THAT is a brilliant idea. Not only will it be faster, but it avoids the closed space hazard issue very well. If it works out you will get thank-you's from the safety folks and the union folks and the foreman that manages the cleaning operation. But your power head may need a spotlight so that they can see the tank drain ports.

Thanks, I didn't even consider putting a light on it, but it's obviously needed. THAT is a brilliant suggestion, thank you!