Woods!

[Kinser Racing]

Last night after I went to bed, in my delirium I was thinking about PWD. I was thinking about the types of woods that are available and that they all have different properties. Most guitar guys can tell you about tone woods. Well, as the car goes down the track it develops a tone with the wheels and other vibrations of the track. I wonder if there's a faster wood out there that we haven't tried? I know we're always looking for light weight with strength but what if we found a wood that had just the right vibration for our car? This wood would most likely be different from class to class, as each class has a different vibration. Just a thought and no I don't own any stock in a wood supplier. lol

Any thoughts?

 

[TRE]

i like that kind of thinking

 

[Obsessedderbydad]

interesting thought. I played the violin for over 10 years and I know that deals a lot with vibrations. You may want to look into it, but I'm not sure it'll have the same effect your looking for. I believe you're looking for a wood that will absorb the vibration or dampen the vibration? Here's what I read about the wood on the violin:

The bridge is a precisely cut piece of maple that forms the lower anchor point of the vibrating length of the strings and transmits the vibration of the strings to the body of the instrument. Its top curve holds the strings at the proper height from the fingerboard in an arc, allowing each to be sounded separately by the bow. The sound post, or soul post, fits precisely inside the instrument between the back and top, below the treble foot of the bridge, which it helps support. It also transmits vibrations between the top and the back of the instrument.

Maple is probably the best bet in wood for vibration dampening.

 

[bracketracer]

I used to use pine, now I pretty much only use scrapbinium!

I think how you cut it, slots, grooves, ribs, cavities, foam filled, etc. would affect your results also, maybe more so than the type of wood you use?

 

[Guest]

I used to use pine, now I pretty much only use scrapbinium!

I think how you cut it, slots, grooves, ribs, cavities, foam filled, etc. would affect your results also, maybe more so than the type of wood you use?

Are we talking micro vibrations here?
Sorry, I could not resist.

 

[GravityX]

I would think that you would have to decide or determine the frequency you would be dealing with first. We've got a labscope at work that picks up vehicle frequencies for, what is called NVH or Noise Vibration Harshness. This helps use determine first, second, third and fourth order vibration and helps us isolate the cause of the vibration to which rotating part is causing the problem. This could probably be used to help determine the frequency that needs to be cancelled out, if this is what you are talking about Kinser. But, as you said, each car will be different.

EDIT: For purposes of clarification I was talking about getting the frequencies from the track and not directly from the car itself, as it passed a point on the track. Frequencies would be relatively close.

 

[down4derby]

What about MDF? Lol

 

[plhiatt]

It would be interesting to try different species of wood.
I own a wood manufacturing/cabinet business and I have the ability to machine
any blocks of wood I would like.
Cherry, Walnut, Both maples, bassswood, poplar...etc.....
One thing I have noticed on hardwoods its just like the pinewood blocks we use with density.
For example some pieces of cherry are very light/fine grain compared to other pieces of cherry.
I have never tried to make a car out of it but it may work with a lighter board,
Anyone tried Basswood?
I do like to machine my own wood, I can get it real flat and square even check moisture content.
Except for basswood I would think the woods may be too heavy.

 

[Guest]

Hey Plhiatt,

I use bass wood in some of my cars, but no idea of what they sound like.

When I hit the art supply store I lift up each piece of bass to check for density just like I do with balsa.

Sometimes the bass is as light as some of the balsas.

I like the consistency of bass.

 

[bracketracer]

I used to use pine, now I pretty much only use scrapbinium!

I think how you cut it, slots, grooves, ribs, cavities, foam filled, etc. would affect your results also, maybe more so than the type of wood you use?

Are we talking micro vibrations here?
Sorry, I could not resist.

hydrogen times pi, Joe, hydrogen times pi.......

 

[Tony_in_NYC]

As a guy who makes acoustic guitars, vibration of the wood is what I am looking for. Maple is not going to dampen vibrations. Its purpose as the sound post in a violin is to transmit the vibrations to the back of the violin from the bridge and top. In the guitar world, specifically acoustic guitars, I look for light, strong spruce to make a sound board out of. That's the part of an acoustic guitar with the hole in it. It takes the least amount of energy to get that light, stiff spruce to transmit the vibrations of the strings and move the sound board to make sound.
Balsa is good at absorbing vibrations, but not great. The softer a wood is, the more it will absorb vibrations. The harder it is, the more it will transmit vibrations. So the least dense piece of the lightest wood will dampen the most vibration. Foam rubber will absorb vibrations the best, but structurally, it will not make a good guitar, or pinewood derby car. Ipe, the hardest wood I know of, will dampen vibrations the least, but it is heavy and also does not make good guitar sound boards because of its weight. It probably would not make good PWD cars either because it will skew your COG due, again, to its weight.
So, it looks like, unless you can somehow incorporate a vibration absorbing feature in your cars, the type of wood you are looking for is light, and not too soft to hold nails. Pine works well. Fir might also work well. Do any of you guys make cars from 2x4's bought at Home Depot or Lowes? Those are usually pine, fir or spruce depending upon where you live.

 

[Kinser Racing]

I was hoping you might chime in on this one Tony. My line of thinking on this is not some much to get rid of any frequency's that the track and wheels produce but to try to match them up and put them in harmony. This could give the car faster times if every things in harmony. Some woods are better at some frequencies than others. Maybe there's a better wood to meet the pinewood derby frequencies than pine.

I did try to make some body's out of some wood I got from lowes and it didn't work out for me. DD4H's Sugar Pine Blocks are the best I've found.

 

[Tony_in_NYC]

I get my guitars to sound the way I want by thinning the sound board and then adding bracing. I'll post a pic of a sound board later from my computer. I'm on my phone now. Anyway, I am not well versed in resonant frequency calculations, but I suspect that even if you tuned your car to your track, it would not help when you ran on another track as the vibration of the track plus car would be different. Throw three more cars on the track and all bets are off.

 

[Pacfanweb]

How about a nice piece of cedar? At least it'd smell good.

 

[Tony_in_NYC]

Here is a sound board fully braced and tuned to sound how I want it.

If you would like to see more pics of the construction process, here is a link to the pics of that:
http://www.flickr.com/photos/49539199@N06/sets/72157632630382300/

 

[Kinser Racing]

I get my guitars to sound the way I want by thinning the sound board and then adding bracing. I'll post a pic of a sound board later from my computer. I'm on my phone now. Anyway, I am not well versed in resonant frequency calculations, but I suspect that even if you tuned your car to your track, it would not help when you ran on another track as the vibration of the track plus car would be different. Throw three more cars on the track and all bets are off.

This is totally true. But, if something could be found that was closer than pine maybe, just maybe there's a possibility. A guitar will sound different in a bedroom setting than in a band setting but there can still be harmony between the instruments in the band setting. We can see evidense of what you are are saying by the frequencies of a less than optimally tuned car slowing down the other cars on the track and vice versa. In some cases aerodynamics will play into that but not always. It may just be an exercise in futility but it could have some possibilities.

 

[DerbyDad4Hire]

I was hoping you might chime in on this one Tony. My line of thinking on this is not some much to get rid of any frequency's that the track and wheels produce but to try to match them up and put them in harmony. This could give the car faster times if every things in harmony. Some woods are better at some frequencies than others. Maybe there's a better wood to meet the pinewood derby frequencies than pine.

I did try to make some body's out of some wood I got from lowes and it didn't work out for me. DD4H's Sugar Pine Blocks are the best I've found.

It is weird. The cars I have made from this also do not perform as well.

 

[Tony_in_NYC]

Maybe softer woods dampen the vibrations too much, and slow the car down? As an experiment, it would be interesting to run optimally tuned cars made of different woods to see which goes faster.

 

[plhiatt]

I have never made a car from basswood, but I do make fenders from it.
I wonder why its not used more, its mostly very light and the grain is fine....
I don't know how it would perform with repeated axle removals though.

 

[Carolina Gravity]

It's been awhile since I checked in, but I'll fill you in on all the different woods I tried over the years. Of course I have done the Sugar Pine, yellow Pine and White Pine and John's blocks always worked for me. Then I got into doing sugar pine frames with carbon fiber and that was really fast. I then started getting some wood samples from Banjo and ended up doing cars out of Walnut, Mahogany, Cherry and Purpleheart. Cherry worked really well and was a beautiful finish. A good friend from the NC mountains worked at a saw mill and picked me out some really nice Basswood. It was super light ans very strong. I liked it a lot. I ended up making my last few cars with cedar and they where the best looking cars and ended up being my fastest. Just a few tidbits of some different ones I tried.