hi!
This is my first design of a custom Gearbox.
As i have little to no experience, i’d really like some feedback from more experienced people.
How can i do the weight reduction better?
Any other comments will be appreciated as well…
You need to fillet ALL of those corners. 1678 usually does 0.080-0.090" radius so we can machine them easily with our 4mm on the router.
What kind of reductions are you looking at here? Wheel size? CIMS? MiniCIMS?
(Sniped)
Additionally, There don’t seem to be fillets on the weight reductions of your parts, and since you’re likely doing this on a Mill or Router, round tooling makes round cut out corners.
The two tiny cut outs above the lowest bearing seem really small, and thus unlikely to be able to manufacture. (Also they probably save basically no weight)
Are there standoffs for attaching two plates?
What is this attached to?
+1 on the fillets.
Instead of making struts around holes, trying making them connect holes. After all the forces are usually between the holes.
Looks like you forgot to make mounting holes for the CIMs.
Outline looks nicer if everything is tangent, and creating that outline of tangent lines also makes space for standoffs/spacers to attach the gearbox.
Near the top of the box where those two webs come in I would add material. When you have a sharp corner like that it creates a stress concentration and plus you would not want to run a cutter into a corner like that. If you intend to waterjet cut this even more so because the machine will dwell in that corner where there is no fillet and blow a small hole out in that location making it even worse.
I would also close those holes between the bottom two shapes because that is not enough material worth removing plus it will add some strength to your boxes.
This looks pretty good for a first run through. As you finalize your design pretend you are going to bend the plates on purpose and add a little material where you think it will bend the easiest. In between each shape in this case is where your material thickness probably needs to increase but as previous posters have mentioned, it depends on what you want to drive with it!
Don’t weight reduce yet. Don’t weight reduce until absolutely everything is done. Not until the whole thing is put in a full assembly with all of the parts mated to it, including sensors and hardware. At least, not for your first gearbox. I know it’s the “cool part”, but it’s both the least important and the biggest waste of time if you have to go back and add things, which unfortunately you almost certainly do here.
The separate issue with your lightening, in addition to it being done prematurely, is that depending on your manufacturing method, it’s impossible to make. Hard interior corners basically cannot be done with a conventional CNC mill or router, as the cutting tool is round. Even if you were waterjetting or lasering this plate, hard corners are often stress concentrators and are not usually advisable. There’s also just a lot of spaces where the hard corners here take away important material for very little weight benefit (the tiny pockets above the bottom bearing hole, the material between the first bearing hole and the “rim” for the second one, etc). But really, throw all of this out anyway, and don’t worry about pocketing until you’re very nearly done.
Without seeing the rest of the gearbox (e.g. what goes inside, the exact gear reductions, what the gearbox is for, etc) it is hard to evaluate what’s going on here. It seems like a very big gearbox for what it’s trying to do, though, and I’m not sure why you’ve made it so tall. It’s also unclear if there is any provision for mounting this gearbox at all, and there are no holes for standoffs anywhere in the bottom half of the gearbox. It’s not clear if this thing will have enough rigidity fully assembled to do what it is accomplishing.
I agree with Chris… do you have a way to put your torques in and do a stress analysis? If you can, You can then look at reducing weight in areas of little stress. In your drawing you are using a radial approach to weight reduction. This does little to combat any forces that are in torsion… radial lines will increase strength in compression through the radial “strut” but do little about torsion forces in the piece.
I agree with all the other comments regarding sharp interior corners. Sharp interior corners are a great place for force lines to concentrate… Cracks will start there.