linear actuator ratio

[psycho_fling]

Hi all

I'm trying to work out the ratio of my linac

currently its setup in the 90 degree position, however im looking at changing that so the motor will lie flat onto the main linac body

to then transfer the motor motion to the screw i plan to use timing belts and pulleys. but i want to stick with the same ratio if possible but the 'gear box' is a worm gear to a (i think) Helical gear.

my question is how do i work out the ratio between them ??

thanks alex

[craig_colliass]

Re: linear actuator ratio

On the Worm gear you count the number of starts if you look at the worm gear you will see it is like a multi start thread. the best way to count them is to look at the end of the worm gear you should be able to see quite easily. say there are four starts.
Next you count the teeth on the wheel gear this is straight forward lets say it was 40 teeth,

Then to find the ratio divide one from the other 40 divided by 4 equals a 10:1 reduction ratio

Hope that helps

Craig

[RogueTwoRobots]

Re: linear actuator ratio

I was about to post how to do it, but Craig got in as I was typing, which is just as well because I was wrong

Depending on the ratio, it might be difficult to replicate that using a single-stage timing pulley setup. The smallest timing pulley I know of is 10-tooth, so a 10:1 ratio would require a 100-tooth pulley at the other end. For reference, a 44-tooth timing pulley (T5 pitch) is about 75mm diameter so a 100-tooth one would be pretty huge. So you'd be looking at a two-stage reduction of (roughly) 3:1 per stage. This would require a bit more work and it would maybe be worth getting some sort of plate machined to hold it all together properly.

Or, you could keep the worm gear setup but instead of having the worm attached to the motor, attach it to a bevel gear and put another bevel gear on the motor on a 1:1 ratio. That would allow you to mount the motor on the same line as the actuator but keep the current ratio without having to worry about multi-stage pulley setups.

[psycho_fling]

Re: linear actuator ratio

cheers guys get the jist of it all now