Plaction wheels coming apart
 

We bought brand new 6" Andymark plaction wheels this year. We noticed after the scrimmage that one of the wheels was cracked. Today, one of the wheels on our practice bot completely came apart. It appears to have originated at the hub area. The entire hub disintegrated intiny pieces.

Has anyone else had problems with Plaction wheels? A possibility we thought of is the loctite. I know some plastics don't like loctite. It is likely that when the sprockets were assembled, some loctite got on the plastic. Is this a likely culprit?

Re: Plaction wheels coming apart
 

http://www.useloctite.com/library/faqs3bd1.html

Q: Do you recommend using anaerobics on plastics?
A: Anaerobics are generally not used with most plastics. Anaerobics will stress crack some plastics including many thermoplastics like ABS and polycarbonate. If the product is used for metal-to-metal but in close proximity to plastic, there is the possibility of excess liquid product or vapor affecting the plastic. In the case of compatible plastics like acetals, the anaerobics are simply not the best family of products for effectively locking and/or sealing. Often cyanoacrylates are substituted if they meet the other application parameters.



Plaction wheels are made out of polycarbonate, you are most likely correct in thinking that may be the cause.

Re: Plaction wheels coming apart
 

Bearings. How did you put them on? Think. If you hammered them in, pressed them in, or did anything besides manually pushing them in, most likely you cracked something. Plactions are great if you do them right. We've NEVER had any problems with plactions, and the few problems I've heard are just like yours, for the reason I listed above. I doubt loctite would be able to break a wheel, especially from the place you said.

Another thing: Are you going over the bump? If you are, then you should be careful; Plaction wheels don't break too much, but a small crack in them from putting in bearings wrong added to the force of slaming into, and going over the bump is enough to completely destroy those wheels.

They wouldn't break otherwise. Tons of teams used them in 2010, when the bump was a lot taller, and they worked perfectly.

I'd keep using them, but look at HOW you're using them, and the stress and wear and tear you're putting them through. Every part has its limit, and you may just be pushing yours.

Re: Plaction wheels coming apart
 

Polycarbonate hates loctite. I have seen a sheet crack just from being under a little tension and having loctite driped on it and left to sit overnight

Re: Plaction wheels coming apart
 

We use lock nuts in all of ours, and haven't had a problem. We had little kids driving on our 6" Plaction wheels off and on for ~12 hours overall at the 2010 Science & Engineering Festival. They held up fine, though granted they weren't being banged over a bump there at the S&EF. Last year's 4" Plaction wheels were slammed from forward to reverse more times than I know, and they also engaged in a few high speed impacts too. They're still fine after 3 regular and 2 offseason competitions. We're using KOP wheels for 2012, the hubs of which look like identical plastic to the Plaction wheels. We've banged them around on the ramp a bit, but we'll see after competition season.

Re: Plaction wheels coming apart
 

we used 8in plaction wheels in the israel regional and one craked when we went over the bump. After that we switched to preformane wheels on front.
last year we used 8in plaction wheels and they didnt crack.

Re: Plaction wheels coming apart
 

We recently got some new AM plaction wheels to test for improved traction on the bridge. IMO the bearing fit was seriously off in the too-tight direction.
After testing and not liking the results with the wheels, we could not get the bearings out to transfer them into alternate wheels.

-Dick Ledford

Re: Plaction wheels coming apart
 

Ive have had the outer rim of the wheel crack and throw off the tread. No loctite was used on the wheel. It didn't disintegrate though. It was still usable.

Re: Plaction wheels coming apart
 

The mystery is solved. We didn't use self locking nuts because the ones we had were too tall to fit. We had a student put the wheels together and he use too much blue loctite (blue seems to be worse on polycarb than red) anyway, every wheel had cracks radiating from the nut locations.

Note to all: NEVER USE LOCTITE NEAR POLYCARB!!!!

PLACTION WHEELS ARE POLYCARB!

Re: Plaction wheels coming apart
 

The bumps may have been taller in 2010, but the were at a 45 degree angle. Not the 90 degree angles like this year. Also 2010s bumps were plywood covered in carpet, not steel like this year.

Re: Plaction wheels coming apart
 

Touché. From all I've seen, there hasn't been a 90 degree angled bump like the one now in FIRST except for 2004, but that was a platform you go onto, not a small bump you went over.

To the OP, if the problem persists, switch out the front wheels that hit the bump with performance wheels. They won't break. ;)

Re: Plaction wheels coming apart
 

Our team used them last year on our drive train and this year on our shooter (with trad covered in gorilla tape to reduce tear on ball) and we never had problems with them we push bearings in by hand and use nylock nuts no locktight

Re: Plaction wheels coming apart
 

History lesson--2001 had a bump. The trick there was you also had to go under a limbo bar to cross it--or use the tipping bridge (which wasn't self-leveling). 1999 also had a vertical bump, but it was mobile and more of a platform than a bump...

I think of this game as taking Aim High, using the Breakaway ball handling rules, reorienting and splitting the targets, and then adding the barrier and bridge from Diabolical Dynamics (2001) with a couple extra bridges.

Re: Plaction wheels coming apart
 

We completely destroyed several plaction wheels in 2010.

Re: Plaction wheels coming apart
 

This year's game couldn't have been explained better. I don't know too much about games prior to 2003, since our only alumni from 2001 time will only tell us it was the team's best robot ever (she designed it, of course ;)), and our team didn't compete in 2002.

Now I'm off to look at matches from 2001! :)

How? I've had to use a hammer before in the past to do something like that! :ahh:

Re: Plaction wheels coming apart
 

Take a 120 pound robot, drive it over a 13.5" bump, hit the ground front wheels first at reasonable speed, that seems like it would do about as much if not more than a hammer.

Re: Plaction wheels coming apart
 

This explains a lot! I was wondering why we destroyed a set of kit wheels with tons of fractures around the hub areas. My first thought was that the sprocket was grossly over-tightened into the plastic but I'm realizing it was the loctite! :o

Sigh lesson learned!

Re: Plaction wheels coming apart
 

Here is what happens when you get Loctite on your polycarb wheels:

Re: Plaction wheels coming apart
 

I secured a victor with loctite once.... It is now a bare circuit board... the case just disintegrated >_<