A question for the ENGINEERS!

[hostile]

It is pounds. I triple checked. An absurd weight limit that will be hard to reach, even if I hollow out the pine and fill it with molten lead (which I plan to do).


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Use tungsten - higher density. It is more costly than lead.

[Pheidippides]

Use tungsten - higher density. It is more costly than lead.

Yeah, but harder to get and not in my budget.


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[wuapinmon]

If you can't get bearings for the wheels, be sure to drill out the nail holes in the tires (they aren't perfectly round, ever). Also, graphite should be your lubricant of choice (for the race).

[wuapinmon]

Alright, a thought. I was just peeing and I stared out the window at my AC unit's condenser wildly blowing around the branches of my fuschia azaleas (in all their vibrant glory), and I wondered something. Being largely ignorant of the intricacies of physics, tell me please, how far out from the top of that fan would back pressure on the flow of air impede performance (I imagine it depends on the HP, rpm, etc of the blades). I ask only because it's a serious amount of air being blown into the sky, and I was wondering if a generator fan could be mounted somehow to recapture some of the wasted energy.

[Donuthole]

Alright, a thought. I was just peeing and I stared out the window at my AC unit's condenser wildly blowing around the branches of my fuschia azaleas (in all their vibrant glory), and I wondered something. Being largely ignorant of the intricacies of physics, tell me please, how far out from the top of that fan would back pressure on the flow of air impede performance (I imagine it depends on the HP, rpm, etc of the blades). I ask only because it's a serious amount of air being blown into the sky, and I was wondering if a generator fan could be mounted somehow to recapture some of the wasted energy.

Time to build a pool.

[Bo Diddley]

Alright, a thought. I was just peeing and I stared out the window at my AC unit's condenser wildly blowing around the branches of my fuschia azaleas (in all their vibrant glory), and I wondered something. Being largely ignorant of the intricacies of physics, tell me please, how far out from the top of that fan would back pressure on the flow of air impede performance (I imagine it depends on the HP, rpm, etc of the blades). I ask only because it's a serious amount of air being blown into the sky, and I was wondering if a generator fan could be mounted somehow to recapture some of the wasted energy.

That really depends on the model of your a/c unit. Unit specific documentation should give you the answer. For a typical a/c condenser, I think you're looking at about 48".

[wuapinmon]

That really depends on the model of your a/c unit. Unit specific documentation should give you the answer. For a typical a/c condenser, I think you're looking at about 48".

So, it probably wouldn't be worth the effort then given the dissipation after four feet. Though, in these parts, we're talking pretty much six months of a guaranteed 20 hours a day steady breeze.

[Uncle Ted]

Alright, a thought. I was just peeing and I stared out the window at my AC unit's condenser wildly blowing around the branches of my fuschia azaleas (in all their vibrant glory), and I wondered something. Being largely ignorant of the intricacies of physics, tell me please, how far out from the top of that fan would back pressure on the flow of air impede performance (I imagine it depends on the HP, rpm, etc of the blades). I ask only because it's a serious amount of air being blown into the sky, and I was wondering if a generator fan could be mounted somehow to recapture some of the wasted energy.

Mounting a wind powered generator on top of your A/C compressor would just most likely impede its air flow and cause it to be less efficient. In fact you might want to consider cutting back those glorious fuschia azaleas branches if they are getting too close.

May I suggest that you install a power generating disco floor in your home instead...

http://www.environmentalgraffiti.com...ectricity/1307

http-inlinethumb47.webshots.com-19374-2247035920102365357S600x600Q85.jpg
http-inlinethumb08.webshots.com-27847-2841785880102365357S600x600Q85.jpg

[YOhio]

Nik, can we get an update on the derby? I missed this the first time around and now I'm curious what you ended up doing.

[Pheidippides]

Nik, can we get an update on the derby? I missed this the first time around and now I'm curious what you ended up doing.

I ended up having a conflict and didnt actually race, which was for the best because my design was pretty hard to do with the tools I had available. Now if my dad had have been here with his lathes, CNC milling machines, drill presses, band saws, grinders, belt sanders, etc. - well, that would have kicked the pants off of my power drill and hand saw combo. To make it work I think we would have had to had a few prototypes to work through and experiment with. But the kids and I had a blast making a mess and exploding CO2 cartridge after CO2 cartridge.

[Eddie]

If you ever have one of these "no rules" races again...

We had one of those races. All kinds of clever designs. One guy put in an electric motor, another had his attached to a fishing pole (initially he thought he would reel it in, ultimately he ended up just whipping it), a guy rigged a large sail and brought his electric leaf blower. I completely hollowed out the interior of mine and turned it into a stomp rocket (which worked pretty well).

But the most impressive - a couple of YM put an eye-bolt in the front of their block, put some wheels on it, placed a large cinder-block at the end of the track, and strung a bunch of rubber bands together between the cinder-block and eye-bolt. They had to put a pillow on the bock to keep their car from being destroyed when it reached the end. While they had attached wheels, they were wholly unnecessary. Upon being released their car would leave the track at the starting line and hit it again at the finish line. Of course, if you have rules about staying n your lane, or on the track at the finish line it would be less effective.

[Donuthole]

Bump. I have a situation where an OSHA standard requires that a guardrail "be capable of withstanding, without failure, a force of at least 200 pounds (890 N) applied within 2 inches (5.1 cm) of the top edge, in any outward or downward direction, at any point along the top edge."

No formal testing was done to measure the strength of the rail, but one guy did press against it and shake it to make sure it was sturdy. How strong would a person have to be to intentionally exert 200 pounds of force per-square inch on the railing? I realize the actual railing specifications would probably be necessary to get an exact calculation. I'm just wondering if it's possible for an average person to exert that much force, and if so, how much effort would be required to exert that much force.

No need to worry about grammar in your responses, folks. I's but a humble litigator.

[Uncle Ted]

Bump. I have a situation where an OSHA standard requires that a guardrail "be capable of withstanding, without failure, a force of at least 200 pounds (890 N) applied within 2 inches (5.1 cm) of the top edge, in any outward or downward direction, at any point along the top edge."

No formal testing was done to measure the strength of the rail, but one guy did press against it and shake it to make sure it was sturdy. How strong would a person have to be to intentionally exert 200 pounds of force per-square inch on the railing? I realize the actual railing specifications would probably be necessary to get an exact calculation. I'm just wondering if it's possible for an average person to exert that much force, and if so, how much effort would be required to exert that much force.

No need to worry about grammar in your responses, folks. I's but a humble litigator.

Yes.

A human bite is about 200 PSI (or 890 N) with the molars. You should ask if the person tried to bite it.

[wally]

Bump. I have a situation where an OSHA standard requires that a guardrail "be capable of withstanding, without failure, a force of at least 200 pounds (890 N) applied within 2 inches (5.1 cm) of the top edge, in any outward or downward direction, at any point along the top edge."

No formal testing was done to measure the strength of the rail, but one guy did press against it and shake it to make sure it was sturdy. How strong would a person have to be to intentionally exert 200 pounds of force per-square inch on the railing? I realize the actual railing specifications would probably be necessary to get an exact calculation. I'm just wondering if it's possible for an average person to exert that much force, and if so, how much effort would be required to exert that much force.

No need to worry about grammar in your responses, folks. I's but a humble litigator.

I am removed from my structural courses (and don't work as a structural), so this is basically from memory. Also, in your first paragraph you indicate a '200 lb force' but in the second you indicate '200 lb per square inch' you need to specify which you really mean.

Hypothetically, if a 201 lb person lifted themselves up on the rail on the palms of their hands, they are exerting a >200 lb downward (gravity) force on the rail, but only 200 lb/(whatever they square inch surface area of their palms is).

I am guessing that OSHA is using a point load, so the 200 lbs. Assuming this, an outward 200 lb would take person heavier than 200 lbs and depend on the angle of the force.

Also, I am assuming that the OSHA reg is based on a static load not an impact load. I don't think that the intent of the OSHA reg is to protect people from stupid recklessness, so if a 200 lb person ran at full speed and kicked the railing at full momentum, that would generate an impact load a lot higher than 200 lb.

Generally speaking, if your occupation takes you to places with guardrails, you should assume that they always rickety and never rely on them by leaning on them etc.

[Uncle Ted]

I am removed from my structural courses (and don't work as a structural), so this is basically from memory. Also, in your first paragraph you indicate a '200 lb force' but in the second you indicate '200 lb per square inch' you need to specify which you really mean.

Hypothetically, if a 201 lb person lifted themselves up on the rail on the palms of their hands, they are exerting a >200 lb downward (gravity) force on the rail, but only 200 lb/(whatever they square inch surface area of their palms is).

I am guessing that OSHA is using a point load, so the 200 lbs. Assuming this, an outward 200 lb would take person heavier than 200 lbs and depend on the angle of the force.

Also, I am assuming that the OSHA reg is based on a static load not an impact load. I don't think that the intent of the OSHA reg is to protect people from stupid recklessness, so if a 200 lb person ran at full speed and kicked the railing at full momentum, that would generate an impact load a lot higher than 200 lb.

Generally speaking, if your occupation takes you to places with guardrails, you should assume that they always rickety and never rely on them by leaning on them etc.

He was just asking if it is possible for a human to exert 200 pounds (or 890 Newtons) and how they could do that. The answer is "yes". The person could bite with his molars. It doesn't matter if it is 200 lbs or 200 PSI.

(The first rule of being an expert witness: Don't give more information than what is asked for. The second of being an expert witness: Don't give more information than what is asked for. Third rule of being an expert witness: Make sure the client is billed rounding up to the nearest hour.)

DH, where do we send our invoices?