Gear size/teeth question

[jsfboat]

I'm building a throttle quadrant for a 747-400. I have a certain radius figured out (for the distance to be measured) and the length of travel. How do I figure out what size of a gear I need on the lever and on the potentiometer? Example the travel length is about 12" from the aft limit to the forward limit with a radius, from the pivot, of 6". What size gear should I use so that when the lever travels from the aft to the forward limit, it is one complete revolution of the gear? Is there a certain formula to figure this?

[kermit]

Hi do you have a one turn or a multi turn potentiometer and if so how many turns.
Normally you could use software to ajust
greetz

[Westozy]

Hi Jsfboat,
This is an easy one! A standard potentiometer usually has about 300 degrees of rotation and it is best practice to optimise most of it's travel. If you calculate the actual degrees of movement of the throttle lever you will find it will be somewhere around 90 degrees. In every throttle I have ever made I have used 3:1 gearing - 60mm 60 tooth gear on the lever driving a 20mm 20 tooth gear on the pot. This arrangement obviously gives 270 degrees of rotation on the pot which is ideal. There is a little rotation of travel left on the pot so it isn't driven to it's limits.
I usually cut gear teeth on the actual lever arm itself to save time and reduce the number of parts required but I can supply you with gears cut to any size and ratio if you need some. I now supply Throttletek with TQ gears and they are all 3:1

Cheers Gwyn (Westozy)
www.aerosimsolutions.com.au

[riche543]

Hi
Gwyn
Hope your well
Question on the gears again, Am i right in saying that in involute if i want a gear that is 60mm diametre & has 60 teeth you have to use a 1mm end mill ? . as i use 1.5
which gives me a tip tp tip of about 98mm & cant seem to reduce that down. only if i change module to 1.0 then get 62 on the tip.
Cheers
Rich.

[Westozy]

Hi
Gwyn
Hope your well
Question on the gears again, Am i right in saying that in involute if i want a gear that is 60mm diametre & has 60 teeth you have to use a 1mm end mill ? . as i use 1.5
which gives me a tip tp tip of about 98mm & cant seem to reduce that down. only if i change module to 1.0 then get 62 on the tip.
Cheers
Rich.

Hi Riche, I used those numbers as an example. I usually use 1.5 module with a 1.5mm cutter, a 60mm diameter gear will actually have 38 teeth. My TQ gears are 48T (75mm tip diameter) driving 16T (27mm tip diameter) = 3:1
What is important is the PITCH diameter, add the two pitch diameters, divide by two and you have the centre to centre distance of the axles! I have made module 1 gears with a 1mm cutter and they work out great.

Cheers Gwyn