Gravity Vehicle C

twototwenty
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Re: Gravity Vehicle C

Postby twototwenty » March 18th, 2013, 7:09 am

This may be of interest to people here. At the bottom are the details of the winning vehicles for the NY C-Division State competition.

lmatkovic3
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Re: Gravity Vehicle C

Postby lmatkovic3 » March 18th, 2013, 1:39 pm

We have been getting a score of around 210 for a distance of 5 meters? Is that what you guys have been getting or have you been getting better scores?
On bad trials, we are hovering at around 150. Then again, we have yet to fully optimize our setup, so we may be able to drop to the mid 130's

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Re: Gravity Vehicle C

Postby catfoot » March 18th, 2013, 9:53 pm

So this question arises from pretty derpy circumstances but what's the best way to remove epoxy/glue in general from the insides of (open) bearings? Would just applying a healthy dose of acetone be good enough and not damage the bearings (in some strange fashion)? Would I need to relubricate the bearings, and if so, with what?

Thanks!

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Re: Gravity Vehicle C

Postby iwonder » March 18th, 2013, 9:57 pm

I'm not quite sure that;s possible... If you've got some chemical that dissolves the glue you can probably soak them in that(making sure it doesn't effect your bearing material) and then wash out the glue and dry them with compressed air or something... then relube with a heavy(but not too viscous) oil.
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Re: Gravity Vehicle C

Postby Balsa Man » March 19th, 2013, 4:20 am

So this question arises from pretty derpy circumstances but what's the best way to remove epoxy/glue in general from the insides of (open) bearings? Would just applying a healthy dose of acetone be good enough and not damage the bearings (in some strange fashion)? Would I need to relubricate the bearings, and if so, with what?

Thanks!
Short answer is replace the bearing.
Reasons, in order of importance, 1) safety, 2) likelihood of success (bearing turning out good as new) 3) cost, 4) time.

Let me say this first; I am not recommending you try to dissolve the epoxy out; I am specifically recommending you not try. This really is one of those, "kids, don't try this at home" things.

A little googling on "what dissolves epoxy?" will identify a number of organic solvents that to some extent will soften/dissolve various epoxys. What will work best will depend on the exact epoxyyou're dealing with. Of the organic solvents with some reported ability to dissolve epoxys, acetone is the least toxic. Still, breathing the fumes would not be good for you, and it is very flammable. Methylene chloride (active ingreedient in many paint strippers) is apparently more effective, but is a.....serious chemical requiring some careful safety procedures- known carcinogen, pretty low concentrations breathed in can have toxic effects, can be adsorbed through the skin (causing toxic effects). That means to try to use it, a real respirator, with organic vapor cartriges ($100-$150), nitrile gloves, adult supervision/parental approval. Bearing will have to come out, you'll need a sealed container to soak it in, with container and cap that it can't dissolve.

Problem is, even with multiple soaks, it is very unlikely you will be able to get it all out. Given the tolerances that any decent ball bearings run at, little bits, a film remaining will significantly degrade bearing performance; you will have spent many times the cost of a new bearing, and not have the performance of a new one.
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Re: Gravity Vehicle C

Postby mrsteven » March 19th, 2013, 7:43 am

I've tried to remove CA glue from open bearings before. I eventually got it, but it took an exuberant amount of time, and like balsaman said, it never really was back to good as new.
Trying to remove epoxy from the bearings would prove near impossible and won't be accomplished with just acetone. I think its a worth cause to just buy a new one.
The only reason I tried to salvage the bearing was because it was one I used for gravity vehicle but got glue in it, so it went into my graveyard of assorted parts. I needed it for maglev to be somewhat free but that extra friction from the little glue left was actually desirable so thats why I tried to flush it out.

$3 for the bearing vs 3 hours of your time? Its worth while. Let alone this event really comes down to friction reduction so that little friction left in the mostly-salvaged bearing will change your scores somewhat dramatically, I fear.
2011 Helicopters State Runner-up
2012 Helicopters State Champion
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Re: Gravity Vehicle C

Postby iwonder » March 19th, 2013, 7:58 am

$3 for a bearing? :O
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Re: Gravity Vehicle C

Postby catfoot » March 19th, 2013, 9:58 pm

Alright thanks for the advice everyone, new bearings it (probably) is.

Also, as iwonder said, $3 bearings? Hook me up! o_0

Also (again), does anyone have advice for how to secure the bearings to the vehicle and also to the axles? Seeing as my previous application technique is clearly flawed, I definitely need help.

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Re: Gravity Vehicle C

Postby mrsteven » March 20th, 2013, 5:17 am

.... Umm ya. $3, why what are you guys spending for them? I get all my tech-type-supplies from mcmaster carr so I got 1/4 inner D open flanged ball bearings for 3 a piece.
The flange helps to keep everything square. When you pound the bearing into place the flange keeps it flush with the surface. Therefore, as long as the holes for the bearings are exactly straight from each other and the 2 axles run parallel, it goes straight.
To ensure that, I printed my chassis :D

Securing to the vehicle? Cut the holes the same size as the outer D of the bearing and arbor press it in.
Bearing to axle? I used CA glue havent had an issue ~100 runs later
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Re: Gravity Vehicle C

Postby iwonder » March 20th, 2013, 5:29 am

Are these ABEC rated bearings or just conveyor-belt ones with a lot of play in them? I used some ultra cheap bearings from McMaster Carr for a floating arm trebuchet and I wouldn't use them again :P

I got my bearings for $15 a piece from Stock Drive Products, they're ABEC-3(tight tolerances), flanged, with an extended inner race(so shaft collars don't cause more drag), I also got pillow blocks to mount them in for that price.
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