Hi,
Having first punched a speed bag last week and with my shoulders not being in the best of health, I spent some indoor time over the weekend trying to make myself a ball swivel. I made this mainly as an exercise in design and prototyping - the process might be of interest, so here it is. This first post covers inception to the second working prototype (#7).
It's certainly not intended to be a clone, but does bear obvious similarities in design and construction to the ARC which I've seen and read about. Ultimately, I will likely end up buying something (Thrasher EVO 13 has been mentioned twice to me), but nevertheless I thought there would be some mileage in having a go at making one for fun.
I started with a few initial design constraints:
I printed a few protoypes in PLA (using up old filament).
The nylon balls hadn't been delivered yet, so I used the time to iterate on the design looking at things such as:
I didn't like the wide, flat flange of #1-#3, so I made the fillet asymmetrical so it extended to the bolt holes to cover it a bit, and also modified the shape of the "mouth" to give the bolt a bit of support as it hits at the extent of the swing. Comparison of #1 and #5 below...
Final (current) design in OpenSCAD looks like this:
I had prototype #6 installed last night, and after one more print this morning to tighten up the tolerance around the ball socket, I currently have prototype #7 installed with a 4mm welded eye bolt (counterbored lock nut on the back side of the ball):
It is a bit "sticky" in use... when it slows down, the ball judders in the socket. Weak drywall screws are NOT ideal to mount this with, nor is the use of a mini-alloy carabiner. But the way I hit, neither is likely to be a problem short-term.
I might try a different ball (stainless finial ball??), a different filament in the printer, or perhaps I should quit now and just buy one.
Hope that's interesting to someone.
Matt.
Having first punched a speed bag last week and with my shoulders not being in the best of health, I spent some indoor time over the weekend trying to make myself a ball swivel. I made this mainly as an exercise in design and prototyping - the process might be of interest, so here it is. This first post covers inception to the second working prototype (#7).
It's certainly not intended to be a clone, but does bear obvious similarities in design and construction to the ARC which I've seen and read about. Ultimately, I will likely end up buying something (Thrasher EVO 13 has been mentioned twice to me), but nevertheless I thought there would be some mileage in having a go at making one for fun.
I started with a few initial design constraints:
- 25.4mm nylon ball (influenced by the ARC)
- 69mm BCD bolt pattern seemed to be the "standard"
- "as much of a swing" as possible (ball protruding as much as possible)
- clearance around the mouth for the eye bolt, clip etc.
I printed a few protoypes in PLA (using up old filament).
The nylon balls hadn't been delivered yet, so I used the time to iterate on the design looking at things such as:
- dimensions: thickness, height, hole diameter
- shape: support surfaces, strength, etc.
- surface finish: printer settings
I didn't like the wide, flat flange of #1-#3, so I made the fillet asymmetrical so it extended to the bolt holes to cover it a bit, and also modified the shape of the "mouth" to give the bolt a bit of support as it hits at the extent of the swing. Comparison of #1 and #5 below...
Final (current) design in OpenSCAD looks like this:
I had prototype #6 installed last night, and after one more print this morning to tighten up the tolerance around the ball socket, I currently have prototype #7 installed with a 4mm welded eye bolt (counterbored lock nut on the back side of the ball):
It is a bit "sticky" in use... when it slows down, the ball judders in the socket. Weak drywall screws are NOT ideal to mount this with, nor is the use of a mini-alloy carabiner. But the way I hit, neither is likely to be a problem short-term.
I might try a different ball (stainless finial ball??), a different filament in the printer, or perhaps I should quit now and just buy one.
Hope that's interesting to someone.
Matt.
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