I need the opposite of a worm gear...what's it called?
Asked by
lilikoi (
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April 20th, 2010
Worm gears provide a gear reduction; I need an increase. I also need the input direction of motion to be perpendicular to the output direction of motion, just like a worm gear. What kind of gear am I looking for?
I made a bicycle powered blender and had MacGyver’d this part of the design using a small skate wheel in contact with the larger bike wheel. This worked well, but I want a larger gear ratio to get the blender spinning faster with less work required from the cyclist. So no industrial gears made for large machines, lol, something small and compact is a must. I forget what range of RPM I was looking for originally, but if I can just get a name for the type of gear I need, that will be a great starting point. Thanks!
Or if I ever find one of these on Craigslist, maybe I could just use the skate wheel :D
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11 Answers
I bet Ed Begley might know :)
I saw him making his toast by bicycle power on a recent episode of Living With Ed on the Planet Green channel.
He’s very much into alternative energy resources. Some really fascinating things featured on that show of his.
Why not just use already existing bicycle gearing? If you have a 10-speed derailleur gear from the bicycle then you might already have the transmission / power converter you need.
The redirection of motion from horizontal to perpendicular can be most easily achieved with a flexible shaft.
@CyanoticWasp I’m using a retro/vintage exercise bike that I got for $5 from a neighbor because it is compact (only has one tire) and already has the frame that keeps the wheel off the ground so no gears…
@lilikoi got it.
How difficult would it be to put the gearing from an old ten-speed into the “driven” position on your stationary bike? Then you just need to modify a chain to fit, and mount your gearshift somewhere handy.
I can’t picture how something compact could give more RPMs than running a little skate wheel (approx 3 inch diameter?) off the bike wheel (26 inch?).
You could use epicyclic gearing, similar to the planetary transmission on the Model T Fords. Sort of a poor mans CVT.
@CyanoticWasp Oh, I see what you were saying now. The bike comes with a larger chainwheel and a smaller sprocket at the front tire. The sprocket can’t get much smaller. I may switch out the chainwheel to something bigger, but not sure yet (I’d have to abandon the chain guard thing to make it fit which is cool looking). A gearshift is an option, but my problem right now is speed not torque. Good blenders get something like 30,000 RPM (looked it up again), and I figure an average person won’t want to pedal more than 100 RPM. So the gear ratio needs to be something like 1:300, ideally, which I’m not sure is even possible at all. I can’t get this RPM from bike sprockets alone…The flexible shaft sounds like something that might come in handy. Do you know of anyone that makes one for RPMs like this?
@jaytkay Well, I was using a longboard wheel because they were ‘stickier’/provided more friction. The smaller shortboard wheel was too smooth and didn’t track well. They are made of diff materials… I thought about just lathing the big wheel down, but seems like a waste. Even so, not sure if even that would be a large enough gear ratio. The longboard wheel on the 26” tire was still a bit slow. The exercise bike has an even smaller tire (16” maybe?) so it is even worse. I was thinking something like this would be perfect, where one gear is very large and the other very small and they are perpendicular to each other so the change in direction of motion is inherent. I haven’t been able to find any designed for ‘overdrive’, though, they all seem to be for gear reduction. Not sure if you can just install it backwards and it would work…probs not.
@stranger_in_a_strange_land I think epicyclic would make things more complicated than I’d like them to be, and more expensive… :/
You’re better off using the bicycle to simply charge a battery and use a battery with an induction step-up transformer to change the battery DC to AC at 110V. (Plus a battery charger and that transformer arrangement gives you the option to power anything you own that runs on 110V AC, which in the US is just about everything.)
No way are you going to get a 300:1 gear ratio and shaft (not to mention the changes you have to make to the blender itself) in any cost-effective way.
It’s called a spur gear.
Worm gears have spiral cut drive gears that mesh with a slightly angled driven gear.
Spur gears are straight cut.
The advantage is that worm gears are stronger and quieter, where spur gears aren’t as strong and are noisy.
What you might need is a drive shaft that is driven by a bike chain/gear setup and then the angled gearing would be with two spur gears with 45 degree cut gears so they could operate at a 45 degree angle, like in the differential of a car.
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