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Fuel leaves behind a thin film
I have noticed that the fuel leaves a film on anything that it slides against, and each piece of fuel adds to that layer until eventually there is a pale yellow plastic film covering everything!
This film seems to reduce the effectiveness of shooter wheels by reducing their coefficient of fiction, and reduces the grip of rollers and polyurethane belts. Our plan is to simply scrape it off after every match with fingernails and non-metal tools. stretching the polyurethane belts a bit by hand also seems to loosen up the film. What are your thoughts on this Polyethylene film menace? How do you plan to remove it? How long before the fuel loses so much mass that it shoots differently? Have you found any wheels that naturally shed this film? |
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Our team was suggesting that we spool up our flywheel shooter, and touch some high grit sandpaper to it for a few revolutions.
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We are going to be doing a bit of experimentation on techniques to remove the film but honestly we are probably just going to be buying a ton of wheels and replacing them up to a few times an event.
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Embrace the residue. Let the residue become part of your shooter wheels. Then you never have to worry about cleaning it off ;)
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I saw the same thing with the FTC particles while mentoring last year. It looks like it shouldn't cause much of an issue if your shooter wheels are moderately compliant, and in contact with the fuel for several inches of travel.
My best guess is that it happens with the initial acceleration, where the fuel is grabbed after about 2 rotations, and it's not causing an issue after it is at speed. If you plan to be shooting a lot, either plan around it or be prepared to remove it after each match. In FTC, I found that it's easy enough to grab with your hands. |
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We have not seen this in any of our testing.
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Basically, anything where physics is going to force the wheel to slip at high speed on the fuel for a prolonged time is probably going to melt some of it off. |
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Try acetone or benzene.
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This is an issue for every single kind of shooter wheel, intake mechanism, etc. that we've tested. Some tips:
1. Coarse sandpaper, with pressure and motion applied parallel to the axis of rotation (i.e. left to right) will quickly (albeit, not easily) strip off this material. 2. Some material retains their traction qualities better than others when coated with this clear stuff. Think about the different factors that cause adhesion beyond just if the rubber is grippy or not, such as compliance. Big hint there. 3. Get the RPM right for your wheels. The more slippage between the ball and the wheel, the worse the wear is going to be. Everyone who did Frisbees in 2013 knows this. So if you're relying on over-driving your wheel open-loop and just taking the speed loss, you're doing it wrong. 4. Load the shooter as fast as your mechanism can justify. The less speed differential between your ball speed at the indexer and your ball speed at the shooter, the less material gets stuck due to lower slippage. (Of course, there may be more material on your indexer surface, but that's less of a big deal) 5. Pick kids for pit crew who love sanding things. |
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Is there any prolonged effect of the polyethylene buildup on the shooter wheels even after scraping it all off every match? How often are we all going to have to replace our shooter wheels?
From testing shooter prototypes in the snow, even a little bit of ice or water buildup reduces shooter speed far more significantly than I ever would have thought. |
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Isopropyl alcohol as a cleaning method rather than a solvent may help with removal a little, but really Elbow Grease and Friction are the way to go here. |
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Our shooter is a gravity fed double wide 4 inch stealth wheel "fly wheel". The ball compression created by the fly wheel is less than 1/4 of an inch. WE have found that the build up is due to the quick ball acceleration. The issue we ran into is once the residue build up hit a certain thickness it began to peel off some ball would hit that bare spot on the fly wheel and be sent much farther than ones that hit a residue covered section. We attempted to calibrate our shooter with the build up, but we ran into that issue. So, we will just dedicate a team member to sand our flywheel after every match to clear up our issue.
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To remove the film off a smooth wheel, first cut across the film with a sharp knife or razor. Then you can probably peel it all off easily.
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You might try varying the compression of the ball in your shooter.
The material you see is probably a result of the wheel spinning on the surface of the ball. It is also evidence of a certain amount of inefficiency in applying energy to the ball due to this slippage. We found that by increasing the compression slightly, not only was the residue reduced, but we shot further and with more reproducibility. Compression is really key in getting your shooter to work consistently. It is worth experimenting with small changes to see what happens. |
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For everyone mentioning compression, is this a pretty constant compression throughout the contact arc? And if so, are there any teams trying out a gradual increase or decrease of the amount of compression? That might help with all sorts of things.
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I recall that in '06 we were consistently shredding the surface of the Nerf balls with our shooter wheel. We thought that decreasing the compression would help, but it made the problem worse... increasing compression was the answer. Note that if you have a buildup of plastic from the fuel that means that you are removing the PE from the fuel... thus damaging a field element. If you are removing so much plastic that you need to clean your shooter wheel every match, then you are likely violating the "don't damage the field" rule. Jason |
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