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The San Franciso Fire Department makes its own wooden ladders by hand

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Re: The San Franciso Fire Department makes its own wooden ladders by hand

#281

Post by jaggederest »

theoh wrote: post #220
jaggederest wrote: post #215

Earlier quoted context omitted.

For what it's worth, every rated parachutist packs their own parachute. For the reserve chute, it's always packed or repacked by an FAA certified rigger, which is an incredibly high bar by comparison. They must be repacked every 6 months. The estimate is that on average a parachute will fail one in a thousand times, mostly due to packing error, seldom due to equipment failure. Maybe 90/10 ratio. For a reserve, the ex…

According to Wikipedia, it varies. Some organizations don't require the jumper to pack their own parachute. What does seem to be a common principle is that "All riggers are jumpers and can be asked at any time to jump with a parachute they have packed." or in the US military, that any rigger has packed, without knowing who. http://en.wikipedia.org/wiki/Parachute_rigger

Yep. It's not really that you have to pack your own parachute, more that it's cost and convenience to do so, so it's pretty universal as far as I am aware. I'm not certified or anything but I've jumped a few times and that's what the 10k+ jumpers said at the time.

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#282

Post by mmagin »

mdorazio wrote: post #264
noer wrote: post #61

Earlier quoted context omitted.

Heat deteriorates fiberglass

Do you have any data to detail this? Fiberglass is glass fibers + resin. Decent resin doesn't melt or become weak with normal heat, it just thermally stresses at some point (we're talking > 180C at which point a wood ladder would be on fire). Wood also has issues with heat - it expands, which can cause buckling and cracks. I'm trying to find fiberglass temperature-strength data to figure out why it's not used in fire…

As far as I can tell after some brief googling when I saw this article earlier today: 1. Fiberglass ladders tend to use polyester resin. 2. polyesters tend to have a glass transition temperature (i.e. where the polymer starts to become soft and lose its shape) in the 75 to 125C range.

Wood combustion temperatures are typically about twice that. Also, incidental heat contact can char the surface of the wood and leave it mostly structurally intact.

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#283

Post by mmagin »

burger_moon wrote: post #124
bluGill wrote: post #47

Earlier quoted context omitted.

How does fiberglass stand to high heat?

I looked up g11 and g10 for their structural heat limits, because I know they have a higher heat resistance than most fiberglass, and are limited to around 150c/ 300f. I looked up what a typical house fire burns at which is 600c/1100f. This is actually a great case where asbestos shines. It's nonconductive and can stand very high temperatures. If not for the whole cancer thing.

Some casual googling earlier suggests to me that fiberglass ladders are fiberglass/polyester, not fiberglass/epoxy.

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#284

Post by donarb »

DannyBee wrote: post #226
pm24601 wrote: post #156

Earlier quoted context omitted.

> "I can't think of any reason to acclimatize them this way instead of" .... I bet the expert woodmakers doing this job have very good reasons. Reasons that you haven't thought of.. Seriously, these people are experts. They probably know their job, really, really well.

"I bet the expert woodmakers doing this job have very good reasons. Reasons that you haven't thought of.. Seriously, these people are experts. They probably know their job, really, really well." This is just a random appeal to authority. If you would like to be constructive, please be constructive. First, there is one person doing this. Or was. It was Jerry Lee, who recently retired. He did it for 30 years. In fact,…

Isn't a forestry handbook a "random appeal to authority"?

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#285

Post by tptacek »

padobson wrote: post #135
DannyBee wrote: post #53

I can't think of any reason to acclimatize them this way instead of kiln drying/vaporizing them (depending) to roughly the right moisture content and waiting for 1% change (instead of kiln drying them to 0, or waiting forever for completely green wood) There are studies going back to the 70's by the forestry service (and others) showing there is no change in mechanical properties of pine/fir from these drying schedul…

I'm not sure how many degrees of separation this knowledge is from programming, but it's got to be one of the highest values I've ever seen on HN. Bravo.

It's funny how well this kind of lowbrow snark works here until exactly the moment it totally doesn't.

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#286

Post by tptacek »

donarb wrote: post #284
DannyBee wrote: post #226

Earlier quoted context omitted.

"I bet the expert woodmakers doing this job have very good reasons. Reasons that you haven't thought of.. Seriously, these people are experts. They probably know their job, really, really well." This is just a random appeal to authority. If you would like to be constructive, please be constructive. First, there is one person doing this. Or was. It was Jerry Lee, who recently retired. He did it for 30 years. In fact,…

Isn't a forestry handbook a "random appeal to authority"?

At the point where one of us literally called up the dude who was doing the work and asked, can we dispense with the message board rhetorical kung-fu and just have the rest of the conversation? Thanks.

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#287

Post by segmondy »

Cofike wrote: post #195
eigenvector wrote: post #158

Earlier quoted context omitted.

One of the biggest differences between Europe and North America in this regard is that in European cities, emergency vehicles have to be designed to fit a 1000-year-old city in terms of width, turning radius, maximum weight, etc. This leads to a much more compact shape and shorter wheelbase. In North America streets are designed to fit emergency vehicles. You're not allowed to build a street so narrow that a fire eng…

You should see some streets in San Francisco. No way that a fire engine is fitting on those.

They do, they have the trucks were the rear wheels can turn as well

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#289

Post by maxbond »

function_seven wrote: post #279
tw04 wrote: post #270

Earlier quoted context omitted.

Every fiber glass ladder I've seen has aluminum caps at both ends and aluminum steps.

As long as those steps and caps are connected with fiberglass sides, what’s the issue?

At high voltages the electricity may be able to arc between the steps. Electricity will do some pretty incredible things at high voltages. Check out this video of some idiots turning a powerline into a Jacob's ladder.

https://www.youtube.com/watch?v=-yBTHrXEK4U

Re: The San Franciso Fire Department makes its own wooden ladders by hand

#290

Post by rickycook »

VectorLock wrote: post #235
gsnedders wrote: post #232

Earlier quoted context omitted.

How do other countries with OHLE cope? AFAIK, most use metal ladders. Just rely on quickly getting the wires isolated?

I think when the electrical service wires have insulation it isn't as much of an issue as opposed to the electricity driven trollies needing bare conductors.

melbourne has probably the worlds most extensive tram network, with exposed overhead wires and our fire department uses metal ladders
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