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Unread 08-26-2018, 10:13 PM
tdogb tdogb is offline
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pic: Concept Planetary 775Pro Gearbox

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Unread 08-26-2018, 10:28 PM
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Re: pic: Concept Planetary 775Pro Gearbox

This is pretty slick. Should be pretty easy to slap an output block on there, especially if you don't constrain yourself to the Vex mounting pattern.
How would you machine the ring gear on something like this, as it's probably going to need to be custom?

And as far as I can tell it looks like there's nothing keeping the planet assembly in there. Adding an output block (with another bearing) would solve that.
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Unread 08-26-2018, 10:32 PM
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Re: pic: Concept Planetary 775Pro Gearbox

SDP/SI makes ring gears of many sizes. If you can figure a way to clamp it against rotation (mill slots/keyways, or roll pins), it might make for a nearly all COTS version of this.
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Unread 08-26-2018, 10:46 PM
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Re: pic: Concept Planetary 775Pro Gearbox

Quote:
Originally Posted by Mechvet View Post
SDP/SI makes ring gears of many sizes. If you can figure a way to clamp it against rotation (mill slots/keyways, or roll pins), it might make for a nearly all COTS version of this.
Good SDP-SI ring gears are all metric and made of steel, as are most affordable rings gears. Imperial ones are for some reason thin and of 24DP or higher.
Waterjetting the ring gear might be a better solution given the weight and cost of a COTS ring gear, not to mention post-machining time.
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Unread 08-26-2018, 11:19 PM
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Re: pic: Concept Planetary 775Pro Gearbox

Quote:
Originally Posted by Mechvet View Post
SDP/SI makes ring gears of many sizes. If you can figure a way to clamp it against rotation (mill slots/keyways, or roll pins), it might make for a nearly all COTS version of this.
I looked on sdpsi and khk and couldn't find the exact one I wanted. I could have access to a wire EDM tho.

Quote:
Originally Posted by nickbrickmaster View Post
This is pretty slick. Should be pretty easy to And as far as I can tell it looks like there's nothing keeping the planet assembly in there. Adding an output block (with another bearing) would solve that.
If you look closely there is an e-clip on the sun gear shaft which retains the planet assembly.
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Unread 08-27-2018, 09:02 AM
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Re: pic: Concept Planetary 775Pro Gearbox

I had Anchor labs prototype a waterjet ring gear for me in the spring.

Due to my design, it was not successful. i didn't have proper tooth form for clearance, just CADed standard involute teeth. I still intend to revise the design and 3D print it in carbon fibre to prove it out, then I might go back to them for production. If someone has a resource on how to design ring-gear teeth (clearance), I'd love to see it.

Anchor was very cooperative and if I'd done my job right the part would've been very usable, but I ended up with one ring gear for $116 minus their voucher (thanks).
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Unread 08-27-2018, 01:14 PM
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Re: pic: Concept Planetary 775Pro Gearbox

If you wanted to waterjet ring gear teeth I would probably use a coarser DP than 20, especially on something like this where it's presumably a drive gearbox and you want all the efficiency you can get. Something like 16 DP would be more comfortable depending on nozzle size, etc.

Wire EDM would produce a much better quality part if you have the means to get the ring gear cut that way.
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Unread 08-27-2018, 01:25 PM
Marcus Q Marcus Q is offline
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Re: pic: Concept Planetary 775Pro Gearbox

Another option for a cheap ring gear is cutting up the banebots p80 ring gear like what was done here.
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Unread 08-27-2018, 01:52 PM
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Re: pic: Concept Planetary 775Pro Gearbox

Quote:
Originally Posted by hrench View Post
I had Anchor labs prototype a waterjet ring gear for me in the spring.

Due to my design, it was not successful. i didn't have proper tooth form for clearance, just CADed standard involute teeth. I still intend to revise the design and 3D print it in carbon fibre to prove it out, then I might go back to them for production. If someone has a resource on how to design ring-gear teeth (clearance), I'd love to see it.

Anchor was very cooperative and if I'd done my job right the part would've been very usable, but I ended up with one ring gear for $116 minus their voucher (thanks).
MITCalc is a free downloadable software for designing involute gear teeth.
There is an internal gear tooth generator.
Generate one tooth, spline all the points it generates, extrude the single tooth and array a pattern to form the gear. Otherwise it will take forever to generate the model and tax your CAD system. We did not do anything for tooth clearance that I can remember. We wire EDM'd our gears so we might have just cut a little small to get the clearance, but I don't think we even did that.

We used MITCalc to design the internal gear teeth for our in-wheel-CIM swerve drive in 2014, our shooter shroud gear segment in 2017 and our intake arm gear segment in 2018. It might take you an hour to get it down, but once you do it is invaluable.
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Unread 08-28-2018, 03:05 AM
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Re: pic: Concept Planetary 775Pro Gearbox

If you are looking for cheap 20dp planetary gearbox parts I would see if you can make any of our old GEM parts work. It might save you a bunch of time and money if you can adapt your design to use them vs a custom ring gear. http://www.andymark.com/GEM-Planetary-Parts-s/227.htm
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