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Re: pic: How 125 is rolling this year...
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The fiberglass we used was just simple fiberglass cloth you would buy from home depot/lowe's and then chopped via scissors into ~1/2" long strands and added to the urethane. Quote:
These wheels show a lot of promise in regards to FIRST robots. There are some definite changes I would make to the wheels in regards to geometry, but thats about it. What we are going to do over the summer is machine a block of wax into a wheel with more ideal geometry. We are then going to use that wax wheel to create a new mold. We want to produce some of those wheels from the mold and put them through some tests. If they perform like we expect they will, we want to make a multi-cavity mold. This will allow us to pop out 2-4 wheels at a time and essentially make wheels a standard item for us to design around. Let me know if you have any more questions. -Brando |
Re: pic: How 125 is rolling this year...
Has anyone else tried this? Any success? Brando, what mods did you come up with for this wheel? Can I get a picture of the actual mold? I don't quite get how you get the entire wheel molded on all sides without any machining.
Thanks Bruce |
Re: pic: How 125 is rolling this year...
Those look very nice, I'd love to see how well they work out on an actual drivetrain.
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Re: pic: How 125 is rolling this year...
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If you don't mind small imperfections on the face of the wheel then you don't need to worry about machining. Because you are using silicone as your actual mold cavity, the regular rules of molding can be stretched. Things like undercuts and 0 degree draft can be done because the silicone is compliant and moves out of the way of the way of the part when removing it from the mold. Quote:
-Brando |
Re: pic: How 125 is rolling this year...
So, to make the mold you just laid the master on the bottom of the mold box and poured the silicone over it? The top side of the wheel is as smoothe as the urethane was poured, correct? Or did you pour it high and machine off the excess?
Bruce |
Re: pic: How 125 is rolling this year...
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The mold "box" base was an aluminum plate with the bolt hole pattern drilled into it. This was then used to hold the master (aluminum) wheel down to the plate. I then hot glued a bucket with the bottom cut off around the wheel. Yes, the top side is as smooth as the urethane is poured. Some of our wheels have just the poured urethane surface on top. As we tweaked the process though, we added more glass to the urethane, which resulted in a "bumpier" surface on the top. To enhance the look of the wheels we did start pouring high and machining the excess away. One of the enhancements to the process we are trying to make is to eliminate that step, although it only takes a minute or 2 for that operation per wheel. -Brando |
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What is your final chopped glass to resin ratio? Are you still using 1/2 inch pieces of glass or have you gone shorter?
Bruce |
Re: pic: How 125 is rolling this year...
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The amount of fiber we use is something we still want to play around with. I feel with the geometry tweaks we plan on making that we can reduce the amount of fiber necessary. -Brando |
Re: pic: How 125 is rolling this year...
Have you looked into buying precut fiberglass? You can get in in pretty short lengths that might mold better.
Bruce |
Re: pic: How 125 is rolling this year...
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-Brando |
Re: pic: How 125 is rolling this year...
Where did you purchase the urethane? It's amazing how well this could work for other applications.
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Re: pic: How 125 is rolling this year...
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They have a huge selection of materials to choose from. You can use their data sheets to pretty effectively choose a resin yourself, however their customer service is also super helpful, so if you are not sure, feel free to ask them. The different resin sizes come in pretty handy as well, where trial sizes are cheap and get you a couple parts, and larger sizes can help get you through a large run. -Brando |
Re: pic: How 125 is rolling this year...
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Re: pic: How 125 is rolling this year...
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-Brando |
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