## Ground Pressure Conversion Fail

I was looking at the spec’s of a specific mining machine, and looking at the track section it has ground pressure ratings:

Hmm, 1 decimal place for the psi rating, but 8 or 9 dp for kPa, looks like someone was asleep during high school science.

Charts like psi to pa this don’t help the matter, but really given that the 15.5 psi can come from any value is the range 15.45 psi to 15.5499999 you get a value interval of +-0.344737864kPa. Thus using the old rule output dp equals no more than input dp, thus 1dp or give the error is 0.3 kPa, you should almost use 0dp.

Upon showing this to a co-worker, I also noticed that the track length is noted to the half inch 181.5″ (it also could be read as tenth of an inch) but the metric value is 461.01 cm, yes to the hundredth of an centimeter, called a tenth of a millimeter, that’s some very fine precession. Even at the tenth of a inch, that’s a +-1mm error.

Picky I know, but I’ve been slow on the blogging front, so any post is a good post.

## Amazon Shipping

I have learned some hard lessons from ordering expensive (to me) items from Amazon.

In the past I’d buy something from Amazon that I’d needed, but not really wanted right now and used the Super Saver shipping, and then always felt surprised when it arrived earlier than I had expected and/or they estimated.

This time my weeks and weeks of planning and reading reviews meant I knew what I wanted, Amazon had all the parts in stock, and at good prices, thus I was quite excited. So again I ordered the first lot with Super Saver shipping, and then proceeded to review the shipping process details 3+ times a day, and this slowed the internet down, and thus I’m getting results like this:

This first item arrived last Thursday June 16, but was ordered on the same day the following items:

These will not arrive until tomorrow (Tuesday June 21), and

did arrive on Saturday June 18th.

The first of the two being the key thing I was wanting… so having learned my lesson, that the free shipping was not that free – the cost of faster shipping is not that much more especially relative to ticket price and I could have had it earlier.

There were some other items that I was wanting, so I ordered them. I noticed one of these items got put in the larger shipping bundle of the first order (that hadn’t shipped at that point of time), but again the key item of this new order was delayed.

So inspired by paying more to get it earlier, I changed the shipping to normal shipping (3-5 business days vs. free shipping 5-8 business days) and then split the items for faster shipping to avoid the key item waiting for the non-key item and I’m now greeted with:

The non-key item that originally appeared to be delaying things has shipped and the key item

Has not even left Amazon (they show it in stock) and it’s estimated to get to me tomorrow. This I’d like to see, given that every other package has taken 3 1/2 days to get to me, after it leaves Amazon.

I’m quite grumpy that when I changed to paying for shipping the delivery dates changed from ’30 June – 16 July’ to June 23.

The real kicker is I have ignored the free 1-month Prime two days shipping trial for so long, I didn’t think to use it and I could have gotten the-lot much quicker. Arg, or just paid <\$50 on the important stuff and got that sooner.

Maybe it’s just better to buy from local shops, because if they have it, they have it. Where-as Amazon, wait a week before we even startis shipping model, makes me grumpy. Or maybe this is just the first time I’ve really cared, and thus watched the process and am sensitive to the ‘normal’ process. Or I’ve just never ordered 9 things in the same week, and thus seen the chaos.

Anyway, my key purchase is due for delivery tomorrow, and I’m quite excited.

[Update: 21 June] Shipping got a little messed up today, but Michaela rang local US Postal Service office, and they found the package, and did a special delivery. The only reason I’m updating the blog right now, and not playing is I’ve lost possession of my new toy, or I’m a good preschooler and sharing toys.