Jekyll2018-07-28T13:23:49-04:00https://dvernooy.github.io/Ab hincA website with a blog and various projects I've done.Dave Vernooyhttps://dvernooy.github.ioChristmas payback2017-12-27T00:00:00-05:002017-12-27T00:00:00-05:00https://dvernooy.github.io/blog/truing-stand<p><img src="https://dvernooy.github.io/assets/images/blog/truing/ian-cyclocross.png" alt="" width="420px" />
<em>Nah … no bike repairs needed after this race, right Ian?</em></p>
<h3 id="a-really-cool-christmas-present">A really cool Christmas present</h3>
<p>After many years of bike mechani<em>cry</em>, with <em>cry</em> being the operative word,
I was paid back in spades with this really cool homemade bicycle wheel truing stand. My son (pictured above
at 2017 cyclocross nationals in Hartford) was the brainchild here - he built it all himself
from scratch with the sawdust flying until late on Christmas Eve.</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/truing/truing-stand.jpg" alt="" />
<em>Standing true</em></p>
<p>Pretty cool, eh? Now maybe I can learn how to expertly true a wheel … I’ve got a basement full of ‘em.</p>
<p>Check back for updates on progress.</p>Dave Vernooyhttps://dvernooy.github.ioNow I can really learn to true a wheelBerry Picking2015-07-04T00:00:00-04:002015-07-04T00:00:00-04:00https://dvernooy.github.io/blog/berry-picking<p><img src="https://dvernooy.github.io/assets/images/blog/berries/berries.jpg" alt="" width="700px" />
<em>Summer is here</em></p>
<h3 id="how-long-is-the-berry-season-anyways">How long is the berry season, anyways?</h3>
<p>The date is Sunday, June 29th 2014. For some reason, we have a blackberry bush in our front yard & counted 60 unripe berries. Score. But how long until they ripen? Well, we started doing a daily count
and found out they’re basically all ripe within 2 weeks.</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/berries/berries-2014.png" alt="" width="913px" />
<em>What is our RR? (ripening rate)</em></p>
<p>Now, we weren’t super scientific this first year, so we upped our game in 2015 … learn by (re)doing.
The season was earlier by about a week in 2015 … here’s the data:</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/berries/berries-2015.png" alt="" width="899px" />
<em>Berry good data in 2015</em></p>
<p>Yes, there were more berries in 2015 & there were a few error bars here and there (ahem … Kai) but our initial estimate of 400 berries was pretty darn close, & I was fascinated by that S-curve. The final stats:</p>
<blockquote>
<p>2 week season, starting last week of June through 2nd week of July</p>
</blockquote>
<blockquote>
<p>7 days from first ripe berry to the “berries-galore” knee in the S-curve</p>
</blockquote>
<blockquote>
<p>7 days from hitting “berries-galore” to end of season</p>
</blockquote>
<p>There you have it.</p>
<h3 id="do-you-have-to-make-everything-soooo-boring">Do you have to make everything soooo boring?</h3>
<p>No.</p>
<p>Yum.</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/berries/yummy.jpg" alt="" width="600px" />
<em>Thanks, Mom</em></p>Dave Vernooyhttps://dvernooy.github.ioTime it right for a yummy delightPinewood Derby2010-06-10T00:00:00-04:002010-06-10T00:00:00-04:00https://dvernooy.github.io/blog/pinewood-derby<p><img src="https://dvernooy.github.io/assets/images/blog/pinewood/cars.jpg" alt="" width="550px" />
<em>Thumbs way up for the Pinewood Derby</em></p>
<h3 id="the-master-equation">The master equation</h3>
<p>OK. If you are going for speed (uuh .. you <em>are</em> going for speed) …there is really one equation that describes everything.</p>
<script type="text/javascript" async="" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-MML-AM_CHTML">
</script>
<script type="math/tex; mode=display">% <![CDATA[
\begin{align*}
& v_{max} = \sqrt{\frac{2gH}{1+0.58N\cfrac{m}{M}}}
\end{align*} %]]></script>
<p>where <script type="math/tex">v_{max}</script> is the max speed of the car, <script type="math/tex">g</script> is a constant, <script type="math/tex">H</script> is the height of the car, <script type="math/tex">N</script> is the number of wheels that are rotating, <script type="math/tex">m</script> is the mass of one wheel and <script type="math/tex">M</script> is the mass of car.
In a game where every millisecond counts … punch this thing into a spreadsheet & start playing. Here is a screenshot of some realistic values showing the impact of several different design choices.</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/pinewood/pinewood_spreadsheet.png" alt="" width="1102px" />
<em>Crunching the numbers</em></p>
<h3 id="so-what-does-it-all-mean">So what does it all mean?</h3>
<p><img src="https://dvernooy.github.io/assets/images/blog/pinewood/kaicar_old.jpg" alt="" height="512px" />
<em>Awesome … that’s what it all means</em></p>
<p>Besides having fun .. here are my 4 golden rules (plus one).</p>
<blockquote>
<p>Do the basics right … de-burr the wheels, smooth the axles, graphite the axles & make sure the car rolls straight by testing and tweaking the axle positions. No extraneous friction.</p>
</blockquote>
<blockquote>
<p>The math says as large an <script type="math/tex">H</script> as possible, <em>but how</em>? … Here’s how: get the extra weight you add as far back on the car as you can without it tipping over. This effectively “raises the height” of the car. Since the master equation is
all about conversion of potential energy to kinetic energy, this is about the only (legal) way to do it.</p>
</blockquote>
<blockquote>
<p>The math says as large an <script type="math/tex">M</script> as possible … so add weight right up to the max. This has nothing to do with heavier objects going faster (they don’t) .. it is because the larger the ratio <script type="math/tex">\frac{M}{m}</script> the more of the original potential energy is converted into translational (vs. rotational) kinetic energy.</p>
</blockquote>
<blockquote>
<p>The math says as small an <script type="math/tex">N</script> as possible. So <script type="math/tex">3</script>. So tweak it so only <script type="math/tex">3</script> wheels touch the track … the real goal here is to keep one from not spinning & use that saved energy to propel the car forward (reduced friction is just a bonus)</p>
</blockquote>
<blockquote>
<p>+1: Make the car look awesome (for karma) … and also so the guy or gal staging them on the start ramp handles your torpedo with kid gloves.</p>
</blockquote>
<p>Beyond these, everything else in the master equation (<script type="math/tex">g</script>, <script type="math/tex">m</script>) is fixed either by nature or the car kit you got at your cub scout troop.</p>
<h3 id="if-you-cant-go-fast-">If you can’t go fast …</h3>
<p>Soooo … did we ever win the derby? Well, once or twice.
<img src="https://dvernooy.github.io/assets/images/blog/pinewood/fast.jpg" alt="" height="568px" />
<em>Fast</em></p>
<p><img src="https://dvernooy.github.io/assets/images/blog/pinewood/kaicar.jpg" alt="" height="512px" />
<em>Faster</em></p>
<p>We also got confused <sup>1</sup> a couple of years and got creative … and that worked out ok, too … turns out, there are points for style.</p>
<p><img src="https://dvernooy.github.io/assets/images/blog/pinewood/adlog.jpg" alt="" />
<em>The ol’ Adirondack log</em></p>
<h3 id="even-more-math">Even more math</h3>
<p><a href="https://en.wikibooks.org/wiki/How_To_Build_a_Pinewood_Derby_Car/Physics">This gem</a> goes into a ton more detail for all you budding Newtons out there.</p>
<p><sup>1</sup> <em>see the opening sentence of the blog</em></p>Dave Vernooyhttps://dvernooy.github.io4 Golden rules ... plus one