Quote:
Originally Posted by MattC9
As a part of this years off season I was looking into making custom gearboxes in the off season. But I have small problem, I don't know much about gear boxes, I know the basics from putting AM gear boxes together and making custom vex ones.
But how do I plan one out?(other than copying a hole pattern from an AM one) Lets start simple, I want a single speed gear reduction lets say 8.5:1. Now where should i go to look at custom gears? How do I cad the gears and there "meshing" with out a gear generator?
All your knowledge you could share would be very appreciated.
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You have to start with some basic knowledge about gears. There are probably papers here on CD that talk about gears.
Let's start with your example: 8.5:1 in a single reduction. If you look at MartinSprocket.com gears, just for an example and 20 DP, 20 deg PA gears (I didn't explain what DP and PA mean.) The smallest gear listed is 12 teeth and it has a 0.6 inch PD (pitch diameter - the diameter at which this gear would run with its mating gear.) A mating gear of 100 teeth will get you pretty close to 8.5:1. The pitch diameter of the 100 tooth gear is 5 inches. The center distance between gears would then be (0.6+5.0)/2 = 2.8 inches. This would be the distance between gears. However, there are some practical limits. The 12T gear has a maximum bore of only 5/16 of an inch - this would be a pretty small shaft. The OD (outside diameter) of the 100T gear is 5.1 inches which may be bigger than the wheel you want to use if you are direct driving off the 100T gear. Obviously, there are lots of things to be concerned with and I just touched on a couple.
As far as CAD goes, you don't need to model the gear teeth - they look really good in the model but don't add much real value. You need the outside diameter, the bore (and how torque is transmitted), the thickness, and the pitch diameter.
For starters, do some research on gears and find the basic formulas - they aren't too difficult. Build yourself a spreadsheet that does the calculations you need and after that work on the CAD side of things. You can download a spreadsheet that does these calcs but I believe you'll learn more by creating the spreadsheet yourself.