Weight concentration and placement

[John Palmieri]

OK,

Since we are talking about weight placement, I thought I would ask this question. We have a new smooth S-shaped track that one of the dads built. We came in 3rd this past year behind him of coarse.

My question is to all is, where would you put the weight in your car and how would you contentrate the weight ??

Theory says on an s-shaped track to pack it in the middle. Should it be in the middle with most of the weight concentrated in the middle ? We ran an extended wing with the weight packed in the back with CG 1.25 in front of rear axle. We came in 3rd and would like to improve. I have included somes pics.





Thanks,
John.

[Panzer]

Can you tell us the track running length and start/finish line height difference?
Looking at the pictures I would guess about 30 ft length and 6 ft height difference.
What sort of running times have you seen on this track?
Looks very fast. Probably in the neighborhood of 2.150 to 2.000 seconds

[John Palmieri]

I do not have specific stats on track, but your guess is probably pretty acurate. We do not have a timer, just a place finish timer. It is very fast, so 2 seconds sounds about right.

Also, as you can tell from the picture the track is all down hill ( no flat level area on the track)

[GILLS]

John,

Go to www.stanpope.com, and then click on how to win a pinewood derby. Stan talks about all different track designs, and gives some extremely good knowledge on weight placement and design. Check it out!!

[John Palmieri]

GILLS said:

John,

Go to www.stanpope.com, and then click on how to win a pinewood derby. Stan talks about all different track designs, and gives some extremely good knowledge on weight placement and design. Check it out!!

Thanks, Gills

Not sure what stanpope.com is. Maybe you are refering to members.aol.com/standcmr/lbw_apl.htm

I have read LBW and it does not get into detail about s-shaped tracks. He does hint with a diagram that the CG should be placed in the middle of the car. I was wondering if that changes at all if the slope of the track never reaches 0 degrees.

I posted this topic really just to get other builders input on where they would put the weight and how they would concentrate it if they had to make a car for this track.

John.

[Panzer]

Have you ever seen a car go partially airborne when entering the 2nd major slop section?

[woodenwonder]

Since the start looks to be of very little slope I would put the cm towards front of car, maybe an inch or so past middle of wheelbase. Since there is no flat run out the placement in back does not really benefit. I would think the further forward the weight was it would pull your car over the starting hill quicker. However I have been wrong before. Would be fun to build cars to test the theory though.

[GILLS]

John,

Yes that is the site that I am referring to. I just took you in thru Stan's own personal site. If you will look in the book under section 3, "science 101", and read the first three topics, Stan refers to "S" shaped tracks and gives you a few crude hand drawings to illustrate his point. Hope this clears it up for you.

[John Palmieri]

Panzer said:

Have you ever seen a car go partially airborne when entering the 2nd major slop section?

No, we never have seen any cars airborne. It was our first year with the track.

John.

[John Palmieri]

wooden said:

Since the start looks to be of very little slope I would put the cm towards front of car, maybe an inch or so past middle of wheelbase. Since there is no flat run out the placement in back does not really benefit. I would think the further forward the weight was it would pull your car over the starting hill quicker. However I have been wrong before. Would be fun to build cars to test the theory though.

Thanks for the input. I would like to test, hopefully we can organize a workshop. When looking at the track it seems that it could flatten out for a few feet (its hard to tell). If that is true, would having any of the weight in the rear help ?

If the track flattens at the end for a few feet, I would guess that the center/forward weighted cars would jump out to an early lead and once the cars hit the mini flat, the rear weighted car would catch up some.

[John Palmieri]

GILLS said:

John,

Yes that is the site that I am referring to. I just took you in thru Stan's own personal site. If you will look in the book under section 3, "science 101", and read the first three topics, Stan refers to "S" shaped tracks and gives you a few crude hand drawings to illustrate his point. Hope this clears it up for you.

GILLS,

Yes I have read that section and it still does not help a whole lot. He mentions that this type of track requires a "detailed inspection". I think from the diagrams the weight should be placed in the middle, however I am not sure if that conclusion is based on the track only having one slope and reaching flatout 0 degrees. The track in question has two slopes and small if no flatout.

Thanks,
John.

[GILLS]

John,

Unfortunately I don't think there is a clear and conscise answer to your question, but I do think that you have done several things correctly since you placed third. I do think that wooden wonder is on the right track though. I know that testing isn't the easiest thing to do with limited availability to that track, but its probably the only way you will get your answer. You may want to look at www.grand-prix-race-central.com and go to derby talk and do a topic history search on the subject. I know that Mr. Pope and other pwd professors are on that board and may be able to help. It is a free access board. Hope this helps! Good Luck!