Hacker News Reader

Comment by mylons | Hacker News Reader

artisanal ladders

Artisanal Firewood https://youtu.be/TBb9O-aW4zI

x2. This seems like a case where there probably exists better options but the cost and friction of switching is too high. As long as the money's still coming there's no reason to look for alternatives though, especially when looking for alternatives would involve doing battle with a union over the jobs the alternatives would eliminate.

Does SF really have that many more overhead power lines than other cities to warrant the extra expense? Firefighters elsewhere don't exactly get fried on the daily.

Are there other types of cheaper (in terms of cost per ladder per year) ladders that can be used? Is there a high temp fiberglass? Does someone make aluminum ladders coated in rubber?

Edit: per jdietrich's comment NFPA 1931 compliant fiberglass fire ladders do exist

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.

Wood burns, but doesn't burst into flame with heat and stress. Do fiberglass ladders start to separate into fibers and epoxy under stress conditions, and is that very fine material prone to rapid ignition?

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.

All those downsides apply to wood and aluminum to varying extents. It's a typical case of engineering trade-offs.

Wood chips and cracks (well, splits but it's basically the same thing) dents in any metal structure cause stress rises that do basically the same thing for strength as chips and cracks in fiberglass.

Wood and metal assemblies will all "fail suddenly" when overloaded because a huge part of their strength comes from their shape, they deform from overloading and that reduces strength (positive feedback loop).

Regarding heat, a quick google search turned up [1] which is good to just shy of 400f, about same temp at which the strength of 6061 falls off a cliff. I also found this[2] which to me indicates that the underlying chemical science is at a point where a fiberglass should be able to replicate the heat resistance of aluminum.

https://www.fibreglast.com/product/high-temp-epoxy-resin-300...

https://chemistry.stackexchange.com/questions/22198/are-ther...

Several manufacturers offer NFPA 1931 compliant fiberglass fire ladders. When used with a suitable resin, fiberglass has significantly better resistance to heat and flame. Fiberglass and wood are both prone to sudden failure due to crack propagation, but in both cases that risk is mitigated by regular inspection.

When used with a suitable resin, fiberglass has significantly better resistance to heat and flame.

And how's the price compared with wood?

I can't imagine it's not better than wood ladders made in a low volume specialty shop in SF

You'd be completely wrong. They have access to a lot of wood up there, the space to store that wood, and the time to dry it completely. The actual woodworking itself takes a small fraction of the time, and the overall cost of a wood ladder built this way is under $1000.

In contrast, a high-heat-tolerant resin is expensive. The amount of such resin needed for a table-sized ladder would cost in the hundreds; for a 50 foot ladder, the resin alone would cost in the thousands--and that does not include the cost of other materials, or the cost of actually making, test, or shipping the ladder.

All you're describing sounds way more expensive than a couple carpenters...simply being able to fix a ladder than toss it is a huge saving

Its the little details: -- For example, a 3" Fiberglass Ibeam 10 feet long is ~$200, and only rated to 140 degrees. I can't readily find a more comparable product.

-- your aluminum ladder with high temp rubber, also needs to be electrically insulated; so now you have to toss the whole ladder if the shell is breached in any little way, and probably needs to be re-certified yearly.

edit: i guess you edited while i was replying

Carpenters earning San Francisco wages, who probably qualify for a pension after 25 years of service (because they are in the fire dept)

You say it like its a bad thing. They build a product that consistently has carried firefighters and civilians to safety. They should be making a living wage, and have the ability to retire instead of dying on a factory line at 90.

You should also Google Image search, "San Francisco power lines" -- yes, they have a ton of overhead lines

SF really does have a lot of overhead power lines. e.g. this is pretty typical: https://i.imgur.com/j5v35QY.jpg

Not everything has to be measured in terms of economics.

Reply on news.ycombinator.com