The Craftmans Shop > Radio Control Models
Bruder Manitou 2150 - RC conversion
David Jupp:
It might not be worth too much effort chasing a particular size of shot. The reason being that for a particular regular shape, the absolute size of the particle does not change the bulk (packing) density achieved - as long as the container is reasonably large compared to the particles.
To get a higher bulk density you need a distribution of sizes - so the smaller particles can occupy some of the gaps between larger ones.
ddmckee54:
David:
I went with the #12 shot, 1.3mm diameter, because that allowed me to print a container and add about 25-30g of extra weight into a space where I couldn't even fit a #6 shot or a BB. Which are about 2.8mm and 4.5mm in diameter respectively.
I carved a chunk out of my 3D printed part that fills the gaping 62mm hole Bruder left in the back-side of the tire. I then hollowed that part out to the thinnest wall I was comfortable printing. I've got my filament width fixed at 0.3mm. I'm a bit ham-handed at times so I set the wall thickness at 0.6mm. This left me with a container with an OD of 61mm, walls 0.6mm thick and about 15-20mm deep. The rest of the wheel support structure has about a 3mm wall thickness, I know that's over-kill but so what.
If I can remember to do it, I'll try and set up an exploded view of the internal 3D printed parts for the tire. Designspark 3D is not real friendly for exporting partial views of a model, let alone an exploded view.(It just plain doesn't do it! When I try exporting a 3D PDF with parts of the model hidden, it exports the ENTIRE model.) But at least I can wrap my head around it and make it work, Fusion 360 is just too frustrating for me at this point. Maybe after I retire in a few years I'll be able to spend a week or two doing nothing but Fusion 360, then it might be less frustrating.
Don
awemawson:
Get your view on screen and ‘screen grab’ - control / print screen in windows - then paste it into Paint or whatever, trim, resize, save as a file.
ddmckee54:
Andrew:
Thanks, I've used that trick before.
OK, before I forget about it - AGAIN.... I've attached several files, the first is the 3D PDF of the revised wheel, for those of you that can open it and actually see something.
The second file is a cross section shown through the centerline of the wheel. The silver/grey part with the purple cross section is the only part in this view that isn't 3D printed. This is the rim of the Bruder wheel. The Bruder rim and tire are one piece. I believe that the rim is molded first and then the tire is molded over the rim. Probably using an over-molding method similar to the way hand grips are molded on some tools.
The third file shows the weight containers and the inner part of the tire, with the containers oriented so that you can see the openings. It took 4 design iterations of my inner tire before I got the Bruder tire to stretch over my 3D printed inner tire and then snap back into shape with a relatively smooth transition in all directions. With a flexible tire and a 62mm diameter opening you'd think it wouldn't make much of a difference, but you'd be amazed the difference 0.5mm in diameter can make. For reference in this view I have also shown 3 different sized spheres. NO, they are NOT beryllium spheres - these are smooth not dimpled. The smallest is the 1.3mm diameter of the #12 shot. The mid-sized sphere is the 2.8mm diameter of #6 shot. And the largest sphere is the 4.5mm diameter of the BB.
WeldingRod:
On maximizing the density, you want what's called an apollonian sphere packing. Look for a dense object that is 0.29 times the shot diameter. Sand, maybe?
A three level packing with just a touch of water will turn into a fluid. Very weird to convert stiff mud into free flowing slurry by ADDING super fine sand... we used to.give our clients kits to try this out; it simulated one of our oilfield cements.
Sent from my SM-G892A using Tapatalk
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