pic: Concept Gearbox

[Bill_Hancoc]

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[Tom Bottiglieri]

Why use the 2 planetary drill transmissions. You are going to need to get some machine work and assembly done anyway, so why not get the reduction from the planetary in a smaller, lighter, do-it yourself set up?

[Andrew Blair]

As said above, if you're going to invest so much time into machining the interface, you might be better off combining the CIM outputs before the transmission, thereby reducing weight, and money. Your setup might be lighter too. You have an awful lot of steel in those big gears! I'm pretty the Dewalts could handle the torque from two CIMs, but you'd have to check the specs.

Keep up the good Inventoring!

[sanddrag]

I think the Dewalts are the easiest, cheapest, smallest, and lightest way to get that much reduction (I presume you're going for the 12:1 ratio).

However, here are some things I would change if it were my design:

-Reduce the size of those gears and their hubs a considerable amount.
-Move the motors closer together and push that gear out from being inline. You'd end up with a triangle shape of sort with the center of each gear being a vertex of the triangle. (does anyone get this or did I make it too confusing? Sorry I can't describe it well)
- Find a better way to mount the motors and planetary combos. I think the current method isn't going to cut it. I think in the NBD setup, there is a plate between the CIM and DW tranny. I would modify this plate to look something like the ones in the KOP and mount the CIMS that way.
-How thick are the gearbox plates? I'd say anything over 1/4" is overkill.

PS. I would stick with the two dewalts; I think 2 CIMS into one would fail after a while.

Anyway, looks good and keep up the great work!

[Tom Bottiglieri]

Originally Posted by sanddrag

I think the Dewalts are the easiest, cheapest, smallest, and lightest way to get that much reduction (I presume you're going for the 12:1 ratio).

And buy your way out of creating a solution? There are plenty of ways to get a 12:1 reduction without going for the pre-made DeWalt boxes. I mean, you could design a clone, or a totally different system. You might even learn something! I suppose I would be inclined to travel the educational path though, at least for this competetion.

[sanddrag]

Originally Posted by Tom Bottiglieri

And buy your way out of creating a solution? There are plenty of ways to get a 12:1 reduction without going for the pre-made DeWalt boxes. I mean, you could design a clone, or a totally different system. You might even learn something! I suppose I would be inclined to travel the educational path though, at least for this competetion.

Don't get me wrong. I'm a proud member of the small but mighty "'I think FRC has gotten too easy' Club" but this does bring up the point (which hypocritically I have combated in other threads) that why put yourself through more work if you don't have to? Why go through the trouble if an off-the-shelf solution will fulfill your needs.

To make your own planetary is a tricky business. Finding ring gears with the desired attributes is no easy task. You'd probably have to have some custom made. And the list of difficulties goes on.

To make a spur gear reduction box, I think it is a very educational and rewarding project. However, spur gears aren't cheap, and dewalt transmissions are. Also, a great deal of weight reduction machining must be done.

[Andrew Blair]

[Glitzy Marketing Smile]

And They Shift!!

[/Glitzy Marketing Smile]

[sanddrag]

Originally Posted by Andrew Blair

[Glitzy Marketing Smile]

And They Shift!!

[/Glitzy Marketing Smile]

Yes, but shifting the two of those linked together like they are, I think would end in disaster, or at the least, some very unpleasant noises.

And yes, we still need to know the goals of this design.

[Tristan Lall]

Originally Posted by sanddrag

Yes, but shifting the two of those linked together like they are, I think would end in disaster, or at the least, some very unpleasant noises.

And yes, we still need to know the goals of this design.

There's a small neutral band between the three ratios; try synchronizing the servos, or using one servo, with parallel links to each shifter.

[Tom Bottiglieri]

Originally Posted by sanddrag

Don't get me wrong. I'm a proud member of the small but mighty "'I think FRC has gotten too easy' Club" but this does bring up the point (which hypocritically I have combated in other threads) that why put yourself through more work if you don't have to? Why go through the trouble if an off-the-shelf solution will fulfill your needs.

To make your own planetary is a tricky business. Finding ring gears with the desired attributes is no easy task. You'd probably have to have some custom made. And the list of difficulties goes on.

To make a spur gear reduction box, I think it is a very educational and rewarding project. However, spur gears aren't cheap, and dewalt transmissions are. Also, a great deal of weight reduction machining must be done.

I don't necessarily agree or disagree. Yes, an "off the shelf" would make things much easier, but is this the best solution to the problem at hand? (We don't even know what we need to do yet, for pete's sake!)

I'm just playing devil's advocate.

[Bill_Hancoc]

Originally Posted by sanddrag

-Reduce the size of those gears and their hubs a considerable amount.
-Move the motors closer together and push that gear out from being inline. You'd end up with a triangle shape of sort with the center of each gear being a vertex of the triangle. (does anyone get this or did I make it too confusing? Sorry I can't describe it well)
- Find a better way to mount the motors and planetary combos. I think the current method isn't going to cut it. I think in the NBD setup, there is a plate between the CIM and DW tranny. I would modify this plate to look something like the ones in the KOP and mount the CIMS that way.
-How thick are the gearbox plates? I'd say anything over 1/4" is overkill.

-The gears are off the "shelf" from firstcadlibrary.com and probaley will purchase smaller for the actual assembly.
-I thought of moving the gears closer to each other to save space (one and 3 o'clock and one at 7 o'clock) but decided against it sice it might put too much troq unevenly spread over the center gear, and flexing the shaft.
-The NBD setup does have a plate between the moter and the tranny but i didnt make the actual dewalt trans i just used was a bosch i could find for the representation.
-The plates are 1/4.

Originally Posted by Tristan Lall

There's a small neutral band between the three ratios; try synchronizing the servos, or using one servo, with parallel links to each shifter.

We plan on using one servo to shift the dewalts. Just to mount the servo in the middle and use heavy gage wire (just to clairify not the kind you electronics box uses.) to attach to the shifters.

Thanks for all the input

Email me if you want any more pics since they are too big to attach

[Rod]

You can go to Boston Gear and download CAD drawings for just about every gear they make. If you use Inventor get the .step files.

[Bill_Hancoc]

Since Boston has a ton of different sizes what do you recomend as a tooth amount. I know i want 1/2 in keyed shaft with 20 pitch but dont know what to do for a gear ratio in the gear boxes. Any help is greatly appreciated.