The San Franciso Fire Department makes its own wooden ladders by hand • Hacker News Board

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

#321

Post by stronglikedan » Thu, Jul 12, 2018, 3:09 PM UTC

Broken_Hippo wrote: post #309

curun1r wrote: post #216

Earlier quoted context omitted.

LOL at SFFD giving any shits about costs. This is the same department that power grabbed emergency medical response away from dedicated paramedics in ambulances. Responding in full ladder trucks to take care of drunk homeless people...yeah, they do that, costing millions every year in added expenses and road repairs. But good for them for saving a few bucks on ladders, that must make a huge difference.

This is part of a first responder program, occasionally saving lives. Plenty of cities across the US do this sort of thing. If you have an emergency - especially a medical one - whoever is closest is the right person to respond, be it fire department, ambulance, or police. 3 to 10 minutes in an emergency can make a huge difference. Like it or not, a drunk homeless person is generally a health and/or safety issue. Com…

A lady at a bar passed out for a few seconds last week, and they sent out a full ladder truck, and ambulance, and four sheriff cars, even though she had resumed consciousness before the dispatcher was done gathering info. I would think they could have coordinated via radio and picked one vehicle to show up. A couple of the responders even seemed to be annoyed that she was conscious when they got there. That didn't seem very efficient to me.

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

#322

Post by HillaryBriss » Thu, Jul 12, 2018, 3:31 PM UTC

frandroid wrote: post #201

HillaryBriss wrote: post #69

Earlier quoted context omitted.

a retired police officer once told me that the quantity of officers citywide goes through a repeated cycle from low to high to low again. when the number of officers is too low and there's too much crime, the people demand that the government hire more. so government does that. and crime goes down. then the public notices all these police officers "doing nothing" and complains about wasted government resources. so, n…

Because crime is directly caused by the lack of police officers there to "prevent" it. &eyeroll&

here's a little supporting evidence, but, I freely admit, it's from a mostly rural country many people consider barbaric: http://www.cbc.ca/archives/entry/1969-montreals-night-of-ter...

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

#323

Post by Retric » Thu, Jul 12, 2018, 3:59 PM UTC

LeifCarrotson wrote: post #56

Retric wrote: post #12

Earlier quoted context omitted.

Fiberglass is a terrible choice for these ladders. Most places use Aluminum or steel but that has conductivity issues with the amount of overhead powerlines in SF. They can be coated to reduce conductivity but that has other issues. http://lacountyfirefighters.org/items/Ground_Ladders_by_John... 3. May chip and crack with impact forces. 4. May suddenly crack and fail when overloaded. 5. Can burn when exposed to flame…

I find it interesting that they list "Can be exposed to heat and flame and retain strength" as a property of wooden ladders, but "Can burn when exposed to flame" as a property of fiberglass ladders.

Toss a wood log on top of a fire for 10 minutes then rinse it off with water and you have basically the same wooden log. That fits with how firefighters use ladders because they are trying to put fires out.

It's much larger issue if a ladder is exposed to high temperatures then suddenly fails without warning.

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

#324

Post by namibj » Thu, Jul 12, 2018, 4:35 PM UTC

mmagin wrote: post #282

mdorazio wrote: post #264

Earlier quoted context omitted.

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…

The choice of resin can be accomodated, using polyamides as a matrix with suitable glass (some low-temperature types might not work), or with carbon fibers, should allow ~400°C/ 670K as a usage-limit. If it were to be coated with e.g. CVD SiO2 or something similar, it could have a pretty high reflectivity in the higher-temeperature thermal radiation range of light (where most of the radiation heat from a fire is in).

The mentioned charring is a very important property in buildings, as solid (hard-)wood pillars have astonishing endurance in a full-scale fire, due to them smoldering slowly from the outside in, compared to e.g. steel framing that quickly softens throughout. One additional factor is evaporative cooling/associated covering with mostly inert water vapor due to the water contained in the wood and the water released from the cellulose fibers upon thermal decompositon.

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

#325

Post by namibj » Thu, Jul 12, 2018, 4:43 PM UTC

wahern wrote: post #175

mkhalil wrote: post #67

Earlier quoted context omitted.

For the right money, you can find the right ladder. It's not going to be cheap though, because you have to age the wood. I wonder if there is a way to age the wood to SF humidity/climate faster than real time. Just feels like there has to be.

You can dry wood faster. Lots of woodworkers build little makeshift kilns by stickering the wood inside an enclosure with a fan and, optionally, using the sun or an electric heater. Temperature control, sticker spacing, and proper stacking is key so it takes lots of experience if you don't want to lose too much wood to warping, checking, etc. And 13% moisture is relatively high. Kiln-dried hardwood for furniture is s…

You can also stick them in a room-sized microwave oven operated at rather low frequencies, to get deeper penetration into the wood and dry it from within. If you do that with whole logs, you should be able to cut them to be straight in the dry state.

This takes in the order of days, not years, without damaging the structural integrity by chemical decomposition that starts at relatively low temperatures.

If you are in a hurry, you can also put something like burnt lime in the chamber as that chemically captures the evaporating water without releasing it in these conditions. That way you can keep the humidity under 5% during the process if you spread the lime enough to capture the water as fast as it is driven out of the wood. You need to be careful to not burn the wood, but you should be able to use something from FLIR with some computer vision to check that no lumber overheats. The water also increases the absorption a lot, so this provides feedback that equalizes the humidity, instead of e.g. a runaway heating that would happen if dryer wood absorbs more microwaves.

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

#326

Post by estebank » Thu, Jul 12, 2018, 4:48 PM UTC

morsch wrote: post #311

dalbasal wrote: post #302

Earlier quoted context omitted.

Just as a side point... A lot of architects like this idea from an aesthetic or architectural-sociological reasons. Living in em.. these as houses don't give you a lot of privacy. People walk by, less than a meter from where you're sitting. They sometimes stop to look at your TV. You get used to it, but it's not the kind of thing people go looking for on purpose.

Put stores or offices in the ground floor. Or have a raised ground floor.

Or just embrace it, like the Dutch do[0].

[0]: https://stuffdutchpeoplelike.com/2010/11/24/no-8-not-owning-...

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

#327

Post by cascom » Thu, Jul 12, 2018, 4:59 PM UTC

gsnedders wrote: post #234

cascom wrote: post #183

Earlier quoted context omitted.

For most small towns I think its more the fact that a fire is a pretty rare occurrence (a couple call outs a year with a major fire every few years) so its more of a cost/benefit decision - they're willing to add ~5 min to the response time for a rare event in order to deploy $1m+/year to other higher priority areas

In the UK the majority of firefighters are on retainers, and will spend a few hours a week training, but otherwise just rely on pagers. They're paid a few thousand per year plus hourly and callout rates.

Which is the model for volunteer firefighters in the US (minus the hourly compensation/annual stipend) otherwise its essentially the same.

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

#328

Post by namibj » Thu, Jul 12, 2018, 5:17 PM UTC

jaggederest wrote: post #213

garmaine wrote: post #90

Earlier quoted context omitted.

Pressure? But it’s going to be mighty expensive to build a pressure chamber that big.

Negative pressure might be more useful. Boil out the water under half an atmosphere, and replace the atmosphere with dried nitrogen and a chunk of desiccant. You'll probably damage the wood if you do that though. Now I want to try it in my vacuum chamber, but I'm not sure it'll hold vacuum for weeks/months at a time.

Just use a pipe with conductive plating on the inside and operate it in the 3-digit MHz range as a waveguide. Make sure that the core of the wood has more power than the outside, and that you e.g. move it around lengthwise if you get longitudal resonance in the pipe. Add some desiccant, and make sure the way you couple the energy into the chamber can handle this resonance without frying itself through reflection. Might not need the vacuum, but it should be easy to construct it in a way that it can hold a vacuum of around 10~200 mBar, e.g. with a simple one-stage pump. If you make sure the pump doesn't take in much moisture, there shouldn't be an issue for it.

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

#329

Post by Broken_Hippo » Thu, Jul 12, 2018, 9:15 PM UTC

stronglikedan wrote: post #321

Broken_Hippo wrote: post #309

Earlier quoted context omitted.

This is part of a first responder program, occasionally saving lives. Plenty of cities across the US do this sort of thing. If you have an emergency - especially a medical one - whoever is closest is the right person to respond, be it fire department, ambulance, or police. 3 to 10 minutes in an emergency can make a huge difference. Like it or not, a drunk homeless person is generally a health and/or safety issue. Com…

A lady at a bar passed out for a few seconds last week, and they sent out a full ladder truck, and ambulance, and four sheriff cars, even though she had resumed consciousness before the dispatcher was done gathering info. I would think they could have coordinated via radio and picked one vehicle to show up. A couple of the responders even seemed to be annoyed that she was conscious when they got there. That didn't se…

That in itself likely wasn't. But we are human and stuff happens. We tend to notice such outliers. Having flaws and miscommunication doesn't really mean the system is all bad, though.

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

#330

Post by VectorLock » Thu, Jul 12, 2018, 9:22 PM UTC

rickycook wrote: post #290

VectorLock wrote: post #235

Earlier quoted context omitted.

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

Having never been to melbourne how close to they run to multi-level structures? In San Francisco the wires powering trollies are practically feet from dwellings.