Gravity Vehicle C

[JTMess]

I don't think we've tested ours at 10m recently, but it scored 227 at 8.2m at states last week. As far as aiming our ramp, we just aligned it with the starting line and hoped we were as precise as possible...probably not the best method. If another ramp event exists, I would think a scope fixed on the ramp at a fixed angle would be the most reliable way to aim it properly.

[Balsa Man]

A scope will certainly work. So will a simple V-notch and post/pin sight (like used on rifles). The longer the separation between the V-notch and sighting pin, the better the precision. We use an 18" long piece of wood mounted on the top of the ramp- the end toward the target has a pin of 0.020" diameter piano wire, at the other end is a piece of aluminum angle iron with a V-notch cut/filed into it.
The keys to making it work are:
-getting the vehicle to roll consistently- ideally, running straight, though if it runs a consistent curve, and you get/have data on how far off straight that curve is at various distances, you can work with that. A guide rail, or wheel trough setup, or other way to get the launch angle- the line it runs on the ramp- the same each run is critical.
-getting the sight aligned with the run-line of the vehicle- start with the sighting bar (the wood with pin and notch) so it can pivot from one point. Have it offset from the centerline of the vehicle so it lines up with the paperclip. Set/adjust the ramp so the paperclip passes over the target point. Put a targeting rod up at the target point 10m out (we use a 1/4" steel rod, 24" long, mounted vertically in a plate). Making sure the ramp doesn't move from the alignment that has the paperclip passing over the target, pivot the sighting bar until the notch and pin align with the target rod. Glue the free end of the sighting bar down (w/ CA).

[mrsteven]

I use a literal rifle scope on my ramp, it took a few days of testing to get it so that it was lined up correctly but it works fantastically. Probably a bit overkill but I just had one lying around anyway...

[jacobxc]

I use a literal rifle scope on my ramp, it took a few days of testing to get it so that it was lined up correctly but it works fantastically. Probably a bit overkill but I just had one lying around anyway...

Me and my partner have been wanting to try that, but unfortunately our state is in 2 weeks so we don't and probably shouldn't change anything.

[Cheese_Muffin_Man]

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?

[twototwenty]

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]

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

[catfoot]

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!

[iwonder]

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.

[Balsa Man]

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.