OT(somewhat) - battery operated tools

Re: OT(somewhat) - battery operated tools

John K Jordan

> So what do ya'll think???

I think there is no way to predict! The battery in my crystal ball is dead...

There are a BUNCH of very smart people working on new battery technology and have been for many years. Over those years I've read many press releases of new battery chemistry breakthroughs that promise higher capacity or quicker charge or lower internal resistance or smaller/lighter/safer/cheaper. Unfortunately, practical game-changing technologies like those in the lithium family are rare.

I think the only thing we can do is buy the best available when we need it and just expect it to be superceeded in the future. Besides power tool people, the cell phone/tablet/computer, electric automobile, solar power and lots of other industries and users would love the crystal ball too!

Re: OT(somewhat) - battery operated tools

Alan Zenreich

Funny you should mention battery powered tools. I published a video about some of mine just the other day.

Although I have both gasoline and electric Stihl chainsaws, and enjoy using my Festool corded and battery powered tools, I tend to reach for B&D 20 volt tools most of the time.

Take a peek at some yard cleanup we did the other day.

https://youtu.be/k-Tw1snu6Vk

Re: OT(somewhat) - battery operated tools

Alan Zenreich

Also, there are techy alternatives to leaf blowers for gutter cleaning.

Because the gutters on our multi story house are hi, and I really don't enjoy dragging out and climbing my extension ladder, I hire a gutter cleaning service to do the dirty work.

But of course, when I saw this device.... Well... looks interesting.

Irobot Looj gutter cleaner. http://youtu.be/wT8PvUlTyUo

Gasoline vs. Lithium Ion

Doc Green

Punch line: Using the best current technology, a lithium-ion battery would have to weight almost 15 pounds to deliver the same amount of energy as a pint of gasoline.

If this is indeed the case (if I didn't screw up with my math), the implication is that battery-operated tools like chainsaws, leaf blowers, etc., still have a long way to go before they become comparable to gasoline-powered equipment.

My source of information: Wikipedia! Energy content of gasoline 42.4 MJ/kg. Energy content of lithium ion 0.36 - 0.95 MJ/kg. Note the wide variation.

For my math, I took the best value for lithium ion (0.95 MJ/kg) and assumed that a gasoline engine was 33% efficient, which is probably optimistic for a small 2-cycle engine.

Truth is, I know little to nothing about the specifics of any battery technology or the efficiency of a small 2-cycle engine. However, you can reach the above conclusion based simply on the energy content of gasoline vs. lithium ion batteries.

It's like, you don't have to know all the details of a turnip in order to know you can't get blood out of one.

I wish someone would check this out and find my mistake or back me up. I've got to go cut firewood - with a gasoline-powered chainsaw.

~Doc

Re: Gasoline vs. Lithium Ion

John K Jordan

> ..a lithium-ion battery would have to weight almost 15 pounds to deliver

> the same amount of energy as a pint of gasoline.

Gasoline stores an amazing amount of energy. We didn't do the calculations but once speculated that the energy in one gallon of gasoline should propel a small automobile 20 or 30 miles through the air. (This of course assumes some method of efficiently converting the energy in gasoline to the high velocity a ballistic shot.)

There would be loss from an increased air friction at the much higher speeds at the beginning and end of a ballistic parabolic trip, but perhaps not significantly higher than the loss from the normal friction of rolling tires, bearings, and internal mechanical parts, plus efficiency losses due to heat from the internal combustion.

Car as Projectile

Doc Green

If one gallon of gasoline were used as "gun powder" to shoot a car like an artillery shell, the farthest it would go is about 5.6 miles, or almost 10,000 yards.

Assumed weight of car is 3,000 lbs. Neglected air resistance altogether. Fired at an angle of 45 degrees for maximum range in the absence of air resistance.

Energy content of one gallon of gas: 120 MJ, from Wikipedia.

Not much to do today.

~Doc

Re: Car as Projectile

John K Jordan

That's interesting. I calculated 11.2 miles just now (below) but either way it's still a "fer piece!" We should remember that when carrying a gallon of extremely volatile gasoline in a can. (Or in the trunk of a car!)

Interesting that there is more energy in a gallon of kerosene than gasoline, 142 MJ vs 130 MJ according to The Engineering Toolbox, with diesel at 147 MJ and #6 fuel oil at 161 MJ!

I'll have to ask my buddy Joe who knows everything. What did you calculate for the initial velocity for that mass and energy?

Using 130 MJ energy for gasoline and 1361 kg car (3000 lbs), the kinetic energy calculation gives an initial velocity of 420 m/s. ( KE=0.5*m*v^2 ) Plugging that into the ballistic trajectory calculator I get X=18000 meters at 45 deg, or about 11.2 miles. The car would be in the air about 60 seconds and reach an altitude of 15000 ft. Unless I missed something.

JKJ

Re: Car as Projectile

john lucas

All I know is a little bit of gasoline poured on charcoal brickets and left to sit until it forms vapors will blow the little buggers out of the grill. shouldn't have answered that phone call.

Oops! I only got half of it.

Doc Green

And the correct answer is . . . 11.2 miles, as John J. said.

My value for the initial velocity: 420 m/s. To find the time of flight, I calculated the time to reach its highest point (30.3 seconds) and then -should have- multiplied that by 2, because it's still flying as it comes back down. But I forgot that part. (I'm losing it.) I also get about 15,000 ft for the maximum altitude.

I also made an error with the battery calculation above. The value I gave of a 15 lb battery is for one pound of gasoline - not one pint as I stated. For a pint of gasoline, the battery would have to weigh only about 11 pounds. (Because a pint of gasoline weighs only about 12 oz.) Oh well . . .

~Doc

Acetone vs. Gasoline Flammability

Doc Green

Punch line: Acetone is as flammable as gasoline, if not more so.

While we're off topic, I thought I would throw this in. A few months ago I did an experiment to see if acetone (used by many turners to remove CA glue) is flammable. I put about 2 drops on the corner of a paper towel and then lit it with a match. Before the match even got near the towel - Poof!

The acetone burned so fast it didn't even scorch the paper towel.

I mention this because I saw a video made by a well-known turner in which he had acetone in a spray bottle and was squirting it all around. Had it ignited, the video would have been much more exciting. Ya gotta watch out! Things are lurking out there . . .

~Doc

Back to woodturning

John K Jordan

>I put about 2 drops [of acetone] on the corner of a paper towel and then lit

> it with a match. Before the match even got near the towel - Poof!

I'm no chemist, but I've read that acetone and gasoline are very similar in flammability, behaving somewhat differently under controlled conditions. I have heard that gasoline is more dangerous but I suspect either will burn down your shop. (There, back to wooturning)

My favorite gasoline story: a friend poured gasoline on brush before lighting it. He carried the can WAY back and set it down on the ground. (He said the can was not leaking or dripping) When he lit the brush pile the flame followed path he had taken back to the can. There was a very nice explosion. The moral: don't do that!

Diesel fuel works quite well for that. BTW, the absolute best way I've found to burn a big pile of even damp brush is turn it into a blast furnace with a leaf blower. It gets hot enough to melt glass.

Hey, more woodturning! (Disposal of offcuts and shavings)

JKJ

Re: Back to woodturning *LINK*

Dave Paine

Acetone is in the same flammability class as gasoline, but it is more volatile and has much lower % in air which can ignite - Lower Flammability Limit.

I use acetone to cleanup CA and epoxy glues, cleaning metal parts, etc. but do so carefully. I use a small amount on a piece of paper towel.

The paper towel is soon dry since the acetone evapourates so fast. A lot faster than wetting a piece of paper towel with gasoline.

The link is a Wikipedia page showing some of the flammability statistics for common flammable compounds.


https://en.wikipedia.org/wiki/Flammability_limit

Re: OT(somewhat) - battery operated tools

bill tucker

Thanks everybody for their wisdom and especially for their humor This is just why I love this group! Alan, I've got to admit - that gutter-cleaning thingy is pretty awesome....expensive, but awesome. My problem is always one of allocation of resources. ie: the cost of that leaf blower vrs a new wood turning tool! Decisions, decisions!

Re: Car as Projectile

Brad Vietje

GASOLINE ? Was that a DAMHIKT moment?

Whoa there, John, that's some pretty serious fire starter! And letting 'em vaporize sends little fire-bombs across the yard, too!

If you aren't going to use the "approved starter fluid" in the little blue/white squirt cans from the store, you might want to opt for some kerosene next time... not as volatile by far.

-- OR --

For some real fun, try ether or some spray-on started fluid

Safe spinning (and BBQ!!!),

Brad Vietje

Newbury, VT

Re: Car as Projectile

Bob Macgregor

I have a vague recollection that a shell from one of the main 16" deck guns on a WW2 battleship weighed more than a mid-60's VW Beetle and could be fired over 20 miles. So their powder charge must have been at least a couple of gasoline-gallon-equivalents, right?

Re: Back to woodturning

William Duffield

There are some other solvents that you might find inexpensive, easy to carry into your shop and also useful. Compare the numbers for toluene in the Wikipedia article. Another property of toluene is its density. It likes to crawl along the floor, until it finds a spark, and the whole floor of the shop is instantaneously on fire. It deserves even more respect than gasoline and acetone.