pic: Gerrish Gearbox MK-III

[Andy Baker]

Tytus,

Nice helical gears. I absolutely love the fact that you are trying something new here with the reversing differential.

Since you posted this, you obviously want input on how to make it better. Here are some suggestions:

1. Give us a cross-sectional picture in order for us to see what is going on with the differential.

2. I am also confused about the qualities for the differential. From what I see, there are 2 input shafts. There are 3 bevel gears mated so that the rotation direction is reversed from one side to the other.

However, I do not see the rpm compensation you are referring to. For example: If the motor on the right input shaft inputs a speed of 4,000 rpm, then the left shaft will turn at 4,000 rpm. If the left shaft inputs a speed of 16,000 rpm, then the right shaft will be spinning at a rate much higher than the free speed limit of 5,500, causing the motor to be very, very inefficient.

3. Your attention to detail with regard to texturing and how the gears look is admirable. This is good stuff for graphical design and animation, but not needed for detailed mechanical design. It is entirely acceptable to model a gear (helical or spur) by simply creating a cylinder with the o.d. as the pitch diameter. This way, you are saving time on the "eye-candy" and spending more time on the nuts and bolts design.

I like your differential idea. But, in order to work, you need to look at changing your ratios on the bevel gears. You don't need to exactly match the free speed ratios of 19,700 : 5,500. If you hit the ratio from anywhere between 3.2:1 and 4:1, then you are doing OK.

Andy B.