pic: Gerrish Gearbox MK-III

[CD47-Bot]

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[George1902]

Someone's gonna have to explain this one to me. I just recently got my mind around your last creation, Tytus... Are you trying to drive me crazy?

Joking aside, care to give a more detailed explaination than in the caption?

[sanddrag]

The top of the picture is a bevel gear differential that is coupled to a different size gear on either side. These gears are rigidly mated with a shaft, one on each side. The shaft's are separate from left and right sides.

In the lower portion of the picture are two different size gears (opposite of the ones on the differential shaft) that ride on bearings and mate with the other gears. The shifting dog is rigidly attatched to that shaft. And engages either gear to drive the differential.

But I'm still oblivious as to why there is even a differential there, this is just sort of the technokats design + one bevel gear differential.

I'm confused too.

[Tytus Gerrish]

the diff is to compincate for any discrepinces in the Rpm's of the two motors over the entire power arc

[sanddrag]

Oh I see now, the motors input the differential, not the shifter. We've gotten into this whole "difference compensation" discussion before.

[Tytus Gerrish]

ill draw the motors in and post that later


Another thing about this box , is its semetrical , so ot can be used on either side of a robot without being mirrored

i also need to know the free rpm for the bosch without its gearbox
i know the CIM is around 5000

[Madison]

Originally posted by Tytus Gerrish
i also need to know the free rpm for the bosch without its gearbox
i know the CIM is around 5000

Approximately 19,700 RPM and 5,500 RPM, respectively.

[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.

[Tytus Gerrish]

there are actual 4 bevels in the diff,1 for each motor and 2 connected to the diff, i think it will be more balanced, and instead of having 1 bevel connected to the diff casing i have 2, since there is twice the surface area i think there will be half the friction, I THINK!, correct me if I'm wrong

a wider tire has more traction than a thin tire right?

[sanddrag]

Originally posted by Tytus Gerrish
there are actual 4 bevels in the diff,1 for each motor and 2 connected to the diff, i think it will be more balanced, and instead of having 1 bevel connected to the diff casing i have 2, since there is twice the surface area i think there will be half the friction, I THINK!, correct me if I'm wrong

I'm really sorry to break this to you but that is kind of what it looked like in the picture. I was just waiting for someone else to say it. Your diff is now, well, not a diff anymore. It will be just as good as a solid axle with all four bevel gears in there. Think about it or try it with legos. Trust me, you need to take one of the bevel gears out that is attatched to the diff housing.

[Tytus Gerrish]

legos dont have a peg for a fourth

And it will work, 4 is fine

[sanddrag]

Originally posted by Tytus Gerrish
legos dont have a peg for a fourth

And it will work, 4 is fine

And I wonder why they don't... Trust me if it worked, you wouldn't be the first to have made one. I've tried. You cannot have a 4 bevel gear differential. Sorry.

[Tytus Gerrish]

i gont think you have grasped this concept


if you made a cube with 6 bevals in all, it of course would not work
but there are only 4 in here 4 will work

[sanddrag]

Originally posted by Tytus Gerrish
i gont think you have grasped this concept


if you made a cube with 6 bevals in all, it of course would not work
but there are only 4 in here 4 will work

Fine have it your way. You know, some people here are trying to help you but if you don't want it that's your own decision. I'm sorry to everyone for these back and forth posts but I thought it was worthwhile for everyone to read.

[Tytus Gerrish]

Me too, sorry
I argue about my gears too much anyways,
ill just draw it better