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-   -   Fuel leaves behind a thin film (http://www.chiefdelphi.com/forums/showthread.php?t=154613)

Bennett548 02-02-2017 08:59

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?

MrForbes 02-02-2017 09:13

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Bennett548 (Post 1639388)
What are your thoughts on this Polyethylene film menace?

It looks like the challenge was even more challenging than we anticipated.

Quote:

How do you plan to remove it?
We are not doing fuel, so we won't worry about it.

Quote:

How long before the fuel loses so much mass that it shoots differently?
I think that is the least of the worries for teams that are playing with fuel.

Quote:

Have you found any wheels that naturally shed this film?
No. But haven't looked, either.

flemdogmillion 02-02-2017 09:17

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by MrForbes (Post 1639392)
No. But haven't looked, either.

Wheels that shed the film will be the same wheels that have an even lower coefficient of friction, particularly fluoropolymers, such as FEP, PTFE, and Viton. Silicone may work though.

lukekaiser 02-02-2017 09:17

Re: Fuel leaves behind a thin film
 
Our team was suggesting that we spool up our flywheel shooter, and touch some high grit sandpaper to it for a few revolutions.

Sperkowsky 02-02-2017 09:19

Re: Fuel leaves behind a thin film
 
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.

pilleya 02-02-2017 09:19

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by MrForbes (Post 1639392)
I think that is the least of the worries for teams that are playing with fuel.

Yep, chances are the fuel is going to be cracked and/ or broken before the weight becomes a serious issue. The residue is a menace, but each individual ball is leaving behind very, very little.

Eric Scheuing 02-02-2017 09:31

Re: Fuel leaves behind a thin film
 
Embrace the residue. Let the residue become part of your shooter wheels. Then you never have to worry about cleaning it off ;)

flemdogmillion 02-02-2017 09:37

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Eric Scheuing (Post 1639405)
Embrace the residue. Let the residue become part of your shooter wheels. Then you never have to worry about cleaning it off ;)

That would be okay if it weren't polyethylene.

lukekaiser 02-02-2017 09:38

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Eric Scheuing (Post 1639405)
Embrace the residue. Let the residue become part of your shooter wheels. Then you never have to worry about cleaning it off ;)

I disagree our robot has shown significant decreases in ball speed when the residue builds up. After shooting about 150 to 200 balls our grey flywheel is a nice high visibility yellow color!!!:ahh: :ahh:

Kartoffee 02-02-2017 09:56

Re: Fuel leaves behind a thin film
 
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.

MrForbes 02-02-2017 10:11

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by lukekaiser (Post 1639409)
I disagree our robot has shown significant decreases in ball speed when the residue builds up. After shooting about 150 to 200 balls our grey flywheel is a nice high visibility yellow color!!!:ahh: :ahh:

Sounds like you might want to make your shooter so it works well after you shoot 200 or so balls with it. That's the point he's trying to make.....if you set up your shooter so it can just barely make the shots when the wheel is new, then you're going to have trouble. You want to set it up so it shoots too far when the wheel is used and has turned yellow, and dial it back a little.

EricLeifermann 02-02-2017 10:23

Re: Fuel leaves behind a thin film
 
We have not seen this in any of our testing.

Kevin Sevcik 02-02-2017 10:46

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by EricLeifermann (Post 1639430)
We have not seen this in any of our testing.

I suspect this starts cropping up when you move from gravity feeding into a shooter wheel to controlled conveyor feeding. If you don't get the spacing right, the conveyor is still holding the fuel when it contacts the shooter wheel, and the shooter wheel slips until it gets enough grip to rip the fuel out of the conveyor. At least, that's my experience from multiwheel frisbee shooters.

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.

Alex Chamberlin 02-02-2017 10:56

Re: Fuel leaves behind a thin film
 
Try acetone or benzene.

Chris is me 02-02-2017 10:56

Re: Fuel leaves behind a thin film
 
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.

EricLeifermann 02-02-2017 10:56

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Kevin Sevcik (Post 1639434)
I suspect this starts cropping up when you move from gravity feeding into a shooter wheel to controlled conveyor feeding. If you don't get the spacing right, the conveyor is still holding the fuel when it contacts the shooter wheel, and the shooter wheel slips until it gets enough grip to rip the fuel out of the conveyor. At least, that's my experience from multiwheel frisbee shooters.

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.

I will definitely be looking for this now. Though i do have our infeed running the same speed as our shooter feeder rollers, so maybe we won't see the extended contact...

jamesmcip 02-02-2017 10:58

Re: Fuel leaves behind a thin film
 
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.

chandrew 02-02-2017 11:01

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by EricLeifermann (Post 1639430)
We have not seen this in any of our testing.

We have not seen this in our testing either. Our compression is fairly low so that could be part of it.

Eric Scheuing 02-02-2017 11:10

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Chris is me (Post 1639437)
5. Pick kids for pit crew who love sanding things.

QFT. If you can get a student who's excited about maintenance in your pit, the'll make sure it gets looked after between each match.

Chris is me 02-02-2017 11:26

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by jamesmcip (Post 1639439)
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.

This entirely depends on your kind of wheel, your shooter dimensions, your motor power, etc. and is the kind of thing every team has to figure out themselves, unfortunately.

flemdogmillion 02-02-2017 12:36

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Alex Chamberlin (Post 1639436)
Try acetone or benzene.

Acetone doesn't dissolve polyethylene. Benzene may dissolve the wheel as well.

Chris is me 02-02-2017 12:41

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by flemdogmillion (Post 1639474)
Acetone doesn't dissolve polyethylene. Benzene may dissolve the wheel as well.

Really there aren't a lot of solvents that dissolve polyethylene but not polyurethane rubber or silicone rubber or polycarbonate or anything that might be around a shooter.

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.

lukekaiser 02-02-2017 13:17

Re: Fuel leaves behind a thin film
 
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.

AdamHeard 02-02-2017 13:21

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Chris is me (Post 1639478)
Really there aren't a lot of solvents that dissolve polyethylene but not polyurethane rubber or silicone rubber or polycarbonate or anything that might be around a shooter.

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.

Our wheels clean off just being rubbed by hand (isopropyl and tower work better), sanding isn't necessary for all wheel types.

flemdogmillion 02-02-2017 14:37

Re: Fuel leaves behind a thin film
 
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.

Bob Steele 02-02-2017 15:05

Re: Fuel leaves behind a thin film
 
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.

GeeTwo 02-02-2017 15:33

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Bennett548 (Post 1639388)
I have noticed that the fuel leaves a film [that] seems to reduce the effectiveness of shooter wheels by reducing their coefficient of fiction, and reduces the grip of rollers and polyurethane belts.

You're using a petroleum-based (mostly) aliphatic FUEL and you're surprised that it leaves a lubricating film? Today MUST be Groundhog Day.

bigbeezy 02-02-2017 15:40

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by EricLeifermann (Post 1639430)
We have not seen this in any of our testing.

Same here, though we'll be looking out for it now...

Cothron Theiss 02-02-2017 15:45

Re: Fuel leaves behind a thin film
 
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.

dtengineering 02-02-2017 17:03

Re: Fuel leaves behind a thin film
 
Quote:

Originally Posted by Bob Steele (Post 1639568)
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.

What Bob says!

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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