sk8norcal said:
From what I understand the hub/core is urethane also, created good bonding with the soft urethane. (vs plastic hubs)
and the "interlock" helps also.
chuttney,
do you have something specific in mind that your are trying to make?
Hummina Shadeeba said:
the rebound isn't given but from what I hear a rebound test is simple and involves dropping a ball on a portion of it and seeing at what percentage it rebounds to. I hear a typical good skateboard wheel will have maybe a 65 rebound so 65% of the height the ball is dropped from it will return to.
Back around 2000 (i think), there wasn't much choice in longboard wheels, pretty much kryptonics. And then ABEC11 flashbacks came out, it was a game changer,made by AEND designed by Chris Chaput. A lot of people were just amazed at how much rebound it has.
what are those!!
Hubmotors? What the hell is Jim Carey doing with those strange hubmotors? What's the white material? They look like they added fins in the white to give airflow. Cool but what about rocks. They even look 3D printed.
I talked to a California wheel manufacturer today forget which. They don't sell the liquids to pour but only done wheels. They were willing to do small runs of whatever but more so what I wanted to hear was that he thought using a hard polyurethane can make a good mold. He explained it's all about having a good plug or pattern or whatever you want to call the part you use to make the mold. But at a point beyond being round it becomes esthetics and while aluminum is better, for prototypes rubber is pretty good. A good 3D print Would do for a pattern and adding some product that covers the lines and maybe some polishing.
You can get rubber at smooth-on.com. Silicone molds are much easier to use but they don't sell a high Duro so maybe only polyurethane is available in the higher duro.
If u get a vacuum chamber make sure it hits at least 29 inches of mercury, all of a sudden a lot of liquid rubbers and resins, even at different viscosity, will degass around there. They blow up and muffin top then collapse. Some things, including polyurethane I think, you don't want to over degass as it will start sucking out weird poison gasses. alot of the vacuum pumps and chambers sold are used for making distilled marijuana. What they do exactly I don't know but they don't need to get to 29 inches of mercury and while pumps are advertised to get to 29.9 even they don't get there but people are still happy cause their weed is still sucked enough. I didn't get enough suck and I wasn't happy and had two get two strong 2 stage pumps and daisy chain them. And you have to get to such a vacuum at a good rate depending on the "pot life" of the liquid rubber or resin your using or things will set-up (harden) before you want or before its fully degassed.
Most casting places will sell or advise using a pressure pot instead of a vacuum To be used on any of the liquid rubbers or resins they sell. How bubbles can get squeezed at 60psi until they somehow disappear when the rubber or resin has cured, even in a soft duro, I don't understand, but none-the-less that's how it's typically done.
If u do get a vacuum and want to see how much suck you truly have, despite what the gauge may say, you can test by using water and a thermometer and Google maps. Depending on your elevation you will be able to boil water at a certain temp if you are at a certain vacuum pressure. For me at 360ft above sea level I think it was 82 degree water that will boil if under 29inches of mercury vacuum. Except when u do this you first must degass the water u use as it'll look like its boiling regardless, and only after you vacuumed it for at least half an hour will it stop bubbling from contained gasses and then it's good for the test. But then when you put this water back under the vac and it starts to bubble because it is truly boiling, the vacuum pressure is released by the gass released. I'm still not sure exactly what I'm getting to but the gauge says 29.5 and I have only found one resin I can't suck till it muffins then breaks.
And if u make a mold ur going to stick I the vacuum chamber it must have been a mold that was made with rubber that had been degassed itself or you can let the mold set in a pressure pot (strangely) or it will later expand and the I have deviations in the casting. Pinholes from the mold bulging.
This is a long explaination and largely just about the vacuum pot and distancing from what's involved in casting wheels..bu t mold making and casting is fun and I've been into it for a couple months and it's rare anyone asks.
I am totally out to do this project. A 2.5 to 3 minute pot life too short for my hand mixing needs which means use of equipment that can extrude material already mix into mold without added air.
