Search found 71 matches

by Jewel
Thu Jul 19, 2007 6:08 pm
Forum: Car & Semi-Truck Construction
Topic: Concentrating the Driving Mass.
Replies: 3
Views: 4349

Concentrating the Driving Mass.

I am sure this has been hashed out, so I am sorry for bringing up an old as the hills kinda question. But it seems to me that the added weight to the body or driving mass should be concentrated in a dense mass. The reason is that if you put the weight in the back it will be on the up hill slope long...
by Jewel
Thu Jul 05, 2007 3:09 pm
Forum: Car & Semi-Truck Construction
Topic: The Limit of Pine as a material
Replies: 5
Views: 7340

Re: The Limit of Pine as a material

Thanks for the tip. I am thinking of sandwiching 2 layers of 1/16 ply and then making the body maybe a a 1/16 in pine. Our rules state the wheels must be mounted in the pine. I was hoping to concentrate the weight as much as possible and keep the body as thin, full of holes, and rigid as possible. M...
by Jewel
Wed Jun 27, 2007 5:52 pm
Forum: Car & Semi-Truck Construction
Topic: The Limit of Pine as a material
Replies: 5
Views: 7340

The Limit of Pine as a material

Just how thin can you safely cut down your pine block?
When do issues of warpage come into play and the stability of the material with respect to alignment?
by Jewel
Wed Jun 27, 2007 12:39 pm
Forum: Car & Semi-Truck Construction
Topic: Rule and letting weight move
Replies: 8
Views: 8536

Re: Rule and letting weight move: Mobile Internal Weight

Let's say the angle of the starting ramp is about 30 degrees. Has anyone every made a cylindrical driving weight that would rest on an internal ramp that is part of the car body that would slope in the opposite direction of the starting ramp and with an angle of less than 30 degrees? What I am sayin...
by Jewel
Tue Jun 26, 2007 5:54 pm
Forum: Car & Semi-Truck Construction
Topic: Rule and letting weight move
Replies: 8
Views: 8536

Rule and letting weight move

Just reading over the standard rules, and this may be the dumbest question ever, but can the driving weight of the car be allowed to move a bit? Could it jiggle around or move in a slot?

Thanks!?!
by Jewel
Mon Jun 25, 2007 9:23 am
Forum: Car & Semi-Truck Construction
Topic: Should I angle the axles?
Replies: 44
Views: 47840

Re: Should I angle the axles?

I am say exactly the opposite. Leave the back wheels flat to minimize friction. Cant the front drive wheel the touches the rail. Canting the front wheel down allows it to roll on the rail rather than rub. It also brings the inside edge closer to the rail to allow a straighter line.
by Jewel
Thu Jun 21, 2007 1:23 pm
Forum: Car & Semi-Truck Construction
Topic: Should I angle the axles?
Replies: 44
Views: 47840

Re: Should I angle the axles?

I have seen this hybrid configuration win very competitive races where it is a team building exercise between experienced engineers. Back wheels Dead On. Front drive wheel canted down about 5 degrees. The front wheel rides the rail ligthly. The point of contact with the rail is at point, the tangent...
by Jewel
Thu Jun 21, 2007 11:01 am
Forum: Car & Semi-Truck Construction
Topic: Lecture 13: Pinewood Derby Physics, Oil and Graphite Lube.
Replies: 21
Views: 26324

Re: Lecture 13: Pinewood Derby Physics, Oil and Graphite Lub

Any more folks sharing results with racing experience using this method would be appreciated. Glad to hear that at least one person reports success.
by Jewel
Tue Jun 19, 2007 12:02 pm
Forum: Car & Semi-Truck Construction
Topic: Lecture 13: Pinewood Derby Physics, Oil and Graphite Lube.
Replies: 21
Views: 26324

Re: Lecture 13: Pinewood Derby Physics, Oil and Graphite Lub

It is a very impressive site, a very generous person has shared a good deal of quality information. I am glad it checks out with folks here. It is pretty counter intuitive to add oil to graphite, seems like it would lead to gummy lube, not fast lube. Lecture 13 calls for a pin head size qty. of Supe...
by Jewel
Mon Jun 18, 2007 12:43 pm
Forum: Car & Semi-Truck Construction
Topic: Lecture 13: Pinewood Derby Physics, Oil and Graphite Lube.
Replies: 21
Views: 26324

Lecture 13: Pinewood Derby Physics, Oil and Graphite Lube.

Is this site for real. Has anyone tried racing with the combination of Super Z plus graphite?

Check this site. http://www.pinewoodderbyphysics.com/lectures.shtml
by Jewel
Tue Jun 15, 2004 1:03 pm
Forum: Car & Semi-Truck Construction
Topic: The Best Lubricant Question
Replies: 32
Views: 54655

Re: The Best Lubricant Question

Krytox comes in 7 grades. It is all the same stuff but each grade has a different viscosity. Krytox 100 is the lowest viscosity, and Krytox 107 is the highest. Which one would be best for a pinecar? There is also a Dupont Dry Film lubricant available. Has anyone tried this? Thanks for the thoughts.
by Jewel
Mon Jun 14, 2004 4:51 pm
Forum: Car & Semi-Truck Construction
Topic: The Best Lubricant Question
Replies: 32
Views: 54655

Re: The Best Lubricant Question

It sounds like Nyoil II, SB10, and Krytox of various types all perform fairly close from what I am reading here.

Do the users of SB10 and Krytox know how long it lasts?

Thanks!!
by Jewel
Tue Oct 14, 2003 2:01 pm
Forum: Car & Semi-Truck Construction
Topic: Inertial and Vibration Losses?
Replies: 37
Views: 48984

Re: Inertial and Vibration Losses?

Hey Mike, I think you have to be really careful when going for the leaf spring design, it may make it hard to get your alignment right. A light chassis with a concentrated mass in one place should help minimize losses when you hit a bump. The key idea I came away with from this discussion is the con...
by Jewel
Tue Sep 23, 2003 2:13 pm
Forum: Car & Semi-Truck Construction
Topic: To True or not to True, that is the question!
Replies: 43
Views: 53931

Re: To True or not to True, that is the question!

My understanding of wheel woble is that it comes from the difference between the axle diameter and the ID of the wheel. If it is too big it is likely that you will get some woble or buzzing. The wheel kind of orbits around the axle rather than sliding around it. One solution is to make sure that you...
by Jewel
Fri Sep 19, 2003 9:15 am
Forum: Car & Semi-Truck Construction
Topic: Front Wheel Location
Replies: 7
Views: 10066

Re: Front Wheel Location

Three wheels are faster for a number of reasons. The most important reason is that your car only has to accelerate 3 masses so it gains speed faster. A key concept is to reduce total rotational inertia, faster accleration means more speed at the bottom of the hill. Some folks consider the fly wheel ...