pic: Offseason Gearbox

[rponmalai]

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[asid61]

Looks very clean.
I like the use of thunderhex and circlips to retain shafts and use round bearings, but for the amount of manufacturing this requires you may want to use 1/2" bearings and shafts with ends rounded. It's a pretty simple lathe job that IME is comparable to an e-clip slot.
You could probably get away with only 4 standoffs, but for mounting purposes you could keep it like it is I guess.

I noticed on the plates your radii are pretty variable, with a 0.04 radius in one of the plates. Depending on the machine, this could make it take considerably longer to machine than using a single larger radius throughout, as a larger endmill can take off more material in general in a certain amount of time.

Overally a pretty sweet gearbox.
It looks like it fits very well into the back of your WCD.

[R.C.]

Originally Posted by asid61

Looks very clean.
I like the use of thunderhex and circlips to retain shafts and use round bearings, but for the amount of manufacturing this requires you may want to use 1/2" bearings and shafts with ends rounded. It's a pretty simple lathe job that IME is comparable to an e-clip slot.

The better way to handle this is to use 3/8" Hex shaft and flip the bearing so the flanges are on the inside that way the bearing is geometrically retained.

Also if possible round down the shafts if possible so you can use a cheaper bearing etc...

[mman1506]

Originally Posted by asid61

I noticed on the plates your radii are pretty variable, with a 0.04 radius in one of the plates. Depending on the machine, this could make it take considerably longer to machine than using a single larger radius throughout, as a larger endmill can take off more material in general in a certain amount of time.

I think your being a little picky. CAM software will try to cut the tightest radius it can with tool specified. You should be able to cut 90% of the lightening holes with a .25 end-mill and then finish things up with a 1/8 end-mill. All in all it should take 8-15 minutes a plate with decent end-mills.

[asid61]

Originally Posted by mman1506

I think your being a little picky. CAM software will try to cut the tightest radius it can with tool specified. You should be able to cut 90% of the lightening holes with a .25 end-mill and then finish things up with a 1/8 end-mill. All in all it should take 8-15 minutes a plate with decent end-mills.

Wait really? I was told I had to put all the radii in manually even for a CNC.
I've been lied to... lol.

[sanddrag]

Originally Posted by asid61

Wait really? I was told I had to put all the radii in manually even for a CNC.
I've been lied to... lol.

You generally want to design the pocket radii some amount larger than the radius of the tool you intend to machine it with. This is to prevent the tool from encountering a sudden and peaking chip load when it gets into the tight corner. It needs some room to still move in the corner, so it isn't contacting all around at the same time.

[Cory]

Originally Posted by asid61

Wait really? I was told I had to put all the radii in manually even for a CNC.
I've been lied to... lol.

If you don't enter the radii you will end up with sharp corners in your toolpath or with finishing passes that take out huge chunks in the corner, not the (for example) .015" you may be running around the rest of the chain. You'll get a radius there, but it will be harder on your tool than desirable and will leave a poor surface finish.

It's always best to make your radii slightly larger than the cutter you intend to use, so that you can roll the cutter through the corners instead of coming in and making a sharp line entry/exit. We usually use .010-.015 more on the radius to help with this.

[asid61]

Originally Posted by sanddrag

You generally want to design the pocket radii some amount larger than the radius of the tool you intend to machine it with. This is to prevent the tool from encountering a sudden and peaking chip load when it gets into the tight corner. It needs some room to still move in the corner, so it isn't contacting all around at the same time.

Can CAM do this for you or do you have to put in all the radii manually?
What size endmill would you normally use as a minimum for something like this?

[MStump]

Originally Posted by R.C.

The better way to handle this is to use 3/8" Hex shaft and flip the bearing so the flanges are on the inside that way the bearing is geometrically retained.

Also if possible round down the shafts if possible so you can use a cheaper bearing etc...

I agree, using 3/8 with rounded ends is pretty nice, simple, and light. You can also use the smaller 7/8 OD bearings.

All in all it looks really clean and nice. I came up with a similar design at the beginning of the season to mount our gearbox at the back of the frame but it did not end up looking nearly this nice haha.

My suggestions for minor improvement:
1. Use the 3/8 shaft mentioned previously for the first stage reduction.
2. Take advantage of the upper bolt on the lower cim for a standoff instead of having another hole solely for a standoff.
3. I wasn't able to download the model but make sure you have straight access to all your bolts on your CIMs. It'll make maintenance a lot easier but I'm sure you already thought of that.
4. Add additional mounting holes and bolts so that it isn't completely resting on the output shaft. (There might be something I'm missing but I can't see where else it would directly mount to the frame.
5. Also just an idea to consider, having only one plate that is repeated on both sides of the gearbox saves some time cadding, machine programming, and machining. However, it also adds a little bit of weight. So if you have the time making two plates is probably better, but if you are in a rush it may be better to forgo the second plate.

[Cory]

Originally Posted by asid61

Can CAM do this for you or do you have to put in all the radii manually?
What size endmill would you normally use as a minimum for something like this?

You should just use the fillet tool in solidworks/inventor/whatever and add .010+ to the nominal radius when you create the fillets.

I dislike using anything less than 1/4" diameter in 1/4" plate. with 1/4" cutter diameter you can go full depth (with a reasonably rigid machine and good chip evacuation). 3/16" and smaller won't allow you to do that.

[Dylan179]

Is the bering on the output shaft pushed out some?

[rponmalai]

Originally Posted by Dylan179

Is the bering on the output shaft pushed out some?

Yeah the flange is actually on the inside of the tubing and that gap is for the thickness of the tubing.

[asid61]

Originally Posted by rponmalai

Yeah the flange is actually on the inside of the tubing and that gap is for the thickness of the tubing.

How will you get it into the tubing?

[Joey Milia]

Originally Posted by asid61

How will you get it into the tubing?

And once you do how will you get it to stay in the wall of the tubing?

[rponmalai]

Originally Posted by Joey Milia

And once you do how will you get it to stay in the wall of the tubing?

http://imgur.com/a/n6cZ8
One of the things I was playing around with in this design was running the timing belts through the tubing of the drive base. I have an access hole for putting the belts through that can easily fit the bearing. The entire shaft would be held together with snap rings. The grooves for those snap rings are on either end of the output shaft.