Gravity Vehicle C

[iwonder]

I use LPS-2(slightly thicker than WD-40) and it works perfectly. Until you hand your vehicle off to someone who picks it up and handles it by the axles, despite being told not to, and fails to clean and recoat them when they're done for the day. I came back the next day and they were slightly rusted and the bearings were staring to grind(these are bronze bushings, so the rotation contact occurs between the shaft and the bronze), luckily after a few turns the shafts freed back up. Do keep in mind that I live in southeast texas and the relative humidity indoors is around 30-40%, outdoors is worse.

[_HenryHscioly_]

Just to confirm,
So zinc plate steel, will easily rust if wd-40 or some type of oil isn't used??
And touching it with your hands is bad??

I hope my car from last year isn't orange/brown by now.....

[iwonder]

Oh, no, no, no... I don't use zinc plated or galvanized steel for my axles, I used raw steel(It's actually O-1 Tool Steel), zinc plating is very corrosion resistant, so no need to worry about that. And touching it with your hands is fine for that kind of steel. It's just raw steel that corrodes much more easily, sorry for the confusion.

[_HenryHscioly_]

Oh, okay, thankss
iwonder, why did you use raw steel instead of a all-thread zinc-plated rod? Was it just because they weren't straight enough?
Would using a die on a zinc-plated/galvanized all-thread defeat the purpose of buying the plated rod?

[iwonder]

I used drill rod on my back axle because I can buy drill rod that's straight to very, very tight tolerances locally, on the front axle, a local machine shop took the design I had and turned down an axle from steel, so both ended up being raw steel(for easy of turning and straightness) I had planned on getting them plated, but failed to ask the shop to turn everything slightly smaller so I could get it plated.

And yes, using a die on zinc-plated rod would get rid of the zinc plating(it's only surface level, probably in the .005-.015" thick range). All thread is plenty straight if you look for the right piece, but my front shaft is much more complex than all-thread.

[_HenryHscioly_]

If my ramp transitions to the floor at, lets say, 10degrees.
then, sin10 of the total velocity would be vertical. Would it somehow still transfer into horizontal velocity? or should the car just bounce/absorb the vertical component?

[retired1]

O-1 drill rod is normally Rockwell C 62-64. That is rather hard for using a die on. A shop that I worked in used a lot of O-1 on fixtures. Part of my duties was to harden it. We bought it annealed.

I live in FL and I do not remember having that much problem with rusting. We did keep most of it lightly oiled. We did have one tool and die maker whose sweat was so corrosive that it would rust a finger print over lunch time.

Zinc plating is normally a max of 0.0015". Galvanized can run up to 0.015"

What kind of plating were you planning on using?? (I am an ex plater)

Why a bronze bushing rather than a ball bearing?? Or a specialty plastic bushing?

[iwonder]

Sorry, again I didn't clarify, I never did any work on the O-1, it was just used for the tolerances it's produced at. I definitely did not harden it, I'm fairly certain it wasn't annealed either.

With the corrosion, yes, the few pieces that I have had control of, and been able to keep oiled haven't rusted, but I wasn't the one running the event for a little over a week, so a few other kids had the vehicle and didn't know how to treat the stuff, it was stored clean and dry, the rust isn't horrible, but because of the bushings and not ball bearings it doesn't run smooth anymore.

Thanks for the correction, I was thinking of galvanization when I typed that, much thicker. I was planning on getting everything nickel plated for the lower friction and corrosion resistance, but we didn't have the time to find a plater and get it plated before states.

The bronze bushing was mainly a price choice, we got SAE-40 impregnated bronze pillow blocks for something like $12 a piece, instead of the $17 or so for ball bearings. The bronze also has the benefit of being self aligning(I thought I would need to use that for slight course corrections, but I didn't). We will definitely use ball bearings this year instead. While we're discussing bearing choices, does anyone have any comments on extended inner rings or not? I'd like to use them(as I use collars on the back axle) but I'm having trouble finding 1/8" ball bearings with an extended inner ring.

[beaverkid]

Retired1, thanks for all the useful insight. You sound like you have a lot of experience with this event. Are you a coach or do you compete?

[Cheese_Muffin_Man]

Does anyone have any ideas on an elastic method to help propel our vehicles?