Search found 475 matches

by GravityRacer
Fri Dec 03, 2010 9:03 pm
Forum: General Car/Truck Racer Topics
Topic: Graphite pads via water?
Replies: 188
Views: 29880

Re: Graphite pads via water?

I lube the locks on my cars with a "liquid graphite" lube called "Lock-Ease". Works great to avoid frozen locks on those freezing Southern California mornings...snort. Readily available in auto parts stores. Never thought to use it on my PWD cars. It has "mineral spirits and kerosene" in it, as well...
by GravityRacer
Fri Dec 03, 2010 8:47 pm
Forum: General Car/Truck Racer Topics
Topic: Should Councils ban the use of lead (Pb) in PWD cars?
Replies: 53
Views: 8736

Re: Should Councils ban the use of lead (Pb) in PWD cars?

Interesting topic, to say the least. I have a couple of comments, one off topic. Note that the Scout Shop only sells ZINC weights. What an individual decides to do in his/her own home and decides to appropriately encapsulate in wood, plaster, Bondo, whatever, is at the risk of said free US citizen, ...
by GravityRacer
Thu Sep 23, 2010 8:02 pm
Forum: General Car/Truck Racer Topics
Topic: Do you hold back info locally?
Replies: 64
Views: 13759

Re: Do you hold back info locally?

Good topic! I usually will show or tell people how to make a faster car. But I won't do all the work for them, they have to do the work. Also, as a former schoolteacher (physics and math), I expect that people who want to "beat all the rest" are going to invest enough time and brainpower to make it ...
by GravityRacer
Sat Sep 04, 2010 9:10 am
Forum: Car & Semi-Truck Construction
Topic: Teflon Theory v. Practice
Replies: 20
Views: 9904

Re: Teflon Theory v. Practice

Wups! The graphite line has the steepest slope near the low pressure end, so my "extrapolation" was wrong in any event. Also, I went to the MaxV website FatSebastian linked, and indeed that is quantitative enough for me. That's how we did coefficients of friction measurements in physics labs.
by GravityRacer
Wed Sep 01, 2010 7:01 pm
Forum: Car & Semi-Truck Construction
Topic: Teflon Theory v. Practice
Replies: 20
Views: 9904

Re: Teflon Theory v. Practice

Like I said, extrapolation is a dangerous business. However, I don't see anything quantitative at either of these links, just "This works better". No offense to MaxV.
by GravityRacer
Tue Aug 31, 2010 8:39 pm
Forum: Car & Semi-Truck Construction
Topic: Teflon Theory v. Practice
Replies: 20
Views: 9904

Re: Teflon Theory v. Practice

By my engineering estimate, the pressure at the wheel-axle interface is about 13 psi, give or take. A bit below 300 kips. Soap and water aren't going to be a good method for removing teflon, and in fact may make it worse. I'd mechanically scrub it off, if I were ever to use it (as if). Teflon sleeve...
by GravityRacer
Wed Feb 17, 2010 10:39 pm
Forum: Car & Semi-Truck Construction
Topic: Derby Freaks R Us
Replies: 8
Views: 1601

Re: Derby Freaks R Us

True, you can't beat lacquer. Fast drying, easy sanding, and ready to use in less than an hour. Yeah, here in sunny California, we can do hobby spraying at will. Can't beat the finish, that's for sure. I'm wondering what I'll do when I go commercial production on my line of woodworking products. I'l...
by GravityRacer
Tue Feb 16, 2010 9:11 pm
Forum: Car & Semi-Truck Construction
Topic: Drilling axle holes with camber and toe.
Replies: 27
Views: 6534

Re: Drilling axle holes with camber and toe.

One can easily drill a hole that lines up for the camber and toe one wants in one shot. I have a copy of the cartesian to spherical coordinates transformation matrix right here in this math book. Seriously, that isn't necessary...just figure the angles you want and place the shim at the appropriate ...
by GravityRacer
Mon Feb 15, 2010 10:24 pm
Forum: Car & Semi-Truck Construction
Topic: PinePro Axle Alignment Jig
Replies: 31
Views: 8495

Re: PinePro Axle Alignment Jig

gpraceman wrote:
Kenny wrote:I am assuming it's not hardened steel.
According to this eBay listing, it is aluminum.
For ~16 USD, aluminum. For ~160 USD, A2 steel. But then, you'd never have to replace it, and all your friends could use it.
by GravityRacer
Sun Jun 07, 2009 8:32 pm
Forum: Car & Semi-Truck Construction
Topic: Exotic materials??????
Replies: 12
Views: 2772

Re: Exotic materials??????

I've never used anything "exotic", but I have reinforced thin areas or areas where the wood could easily snap along the grain. I've always used thin 1/8" to 3/32" hobby plywood, which I recycle from old clementine crates around Christmas time. I find that if you glue a plank of that to the bottom o...
by GravityRacer
Sun Mar 15, 2009 8:16 am
Forum: Car & Semi-Truck Construction
Topic: Help me to understand
Replies: 21
Views: 4191

Re: Help me to understand

<tosses match on fuel-soaked logs> The amount of energy available (potential energy) to be converted to speed is related to the difference in height (start to finish) of the cg on the track: PE=mg h. Regardless of track configuration, the speed will be greater, all things considered, with a cg moved...
by GravityRacer
Fri Mar 13, 2009 8:11 pm
Forum: Car & Semi-Truck Construction
Topic: How fanatical are you guys? (Instrumenting a car.)
Replies: 28
Views: 4827

Re: How fanatical are you guys? (Instrumenting a car.)

Two things: 1kHz is probably a high enough sample rate. That comes to a .5 mm distance. How many (.5 mm dia.) mechanical pencil leads wide is the length of the track? :lol: There is no reason to accept the standard axle for this experiment. It would be acceptable to ream the ID of the wheel to .100"...
by GravityRacer
Fri Mar 13, 2009 11:54 am
Forum: Car & Semi-Truck Construction
Topic: How fanatical are you guys? (Instrumenting a car.)
Replies: 28
Views: 4827

Re: How fanatical are you guys? (Instrumenting a car.)

Given that the car goes <.5 M/s, 10,000 samples per second will give a data sample every .05 millimeters. That's probably more than enough to give a reasonably smooth plot. Flattening the axle, within some limit, would be preferable, I'd think. To find the limit you'ld have to analyze the stiffness ...
by GravityRacer
Thu Mar 12, 2009 7:27 pm
Forum: Car & Semi-Truck Construction
Topic: How fanatical are you guys? (Instrumenting a car.)
Replies: 28
Views: 4827

Re: How fanatical are you guys? (Instrumenting a car.)

wonderer, that setup should give some good results, depending on how low a force (deflection) you can read. The bending moment is going to be pretty low, given the amount of weight and the thickness of the axle. It's worth a shot, just to get some information. I'm used to strain gages on bolts that ...
by GravityRacer
Wed Mar 11, 2009 7:17 pm
Forum: Car & Semi-Truck Construction
Topic: How fanatical are you guys? (Instrumenting a car.)
Replies: 28
Views: 4827

Re: How fanatical are you guys? (Instrumenting a car.)

Ain't that the truth, Fatdaddy! If all that edumacation we get all stuck, we'd be driving Jetsonmobiles to work (on the days when the terabit computer hooked to your head isn't good enough)!