Post a pic of your latest purchase

[whitexk]

Got a present in the mail yesterday. ;D

+2mm over to bring me to 69mm. Compression up from 9.3:1 to 10:1 and the valve pockets sit .020" deeper. Being forged, they're also stronger and lighter than the stock pistons. Each of these come in at 210g as opposed to stock's 221g.

Do you think 11g will make that big of a difference? Usually I hear people refer to pounds and ounces but I have yet heard of a reference to grams.

 

[Sonreir]

Do you think 11g will make that big of a difference? Usually I hear people refer to pounds and ounces but I have yet heard of a reference to grams.

Let's do the math and find out, shall we?

The stoke on my 360 is 50.7mm and for argument's sake, we'll say I want to spin that baby up to 10,000 RPM. To get the speed of the piston, we need to do some math to first get the piston speed in meters per second.

First, divide 10,000 RPM by 60 in order to get RPS and we arrive at 166.66 RPS. So now we know that for every second that elapses, our crank shaft completes 166 and 2/3 rotation. Obviously, for every rotation of the crank shaft, the piston moves down and then back up again, covering 50.7mm x 2.

So now we multiply 50.7 x 2 x 166.66 and find that every second the piston travels 16,900 mm, or 16.9 meters.

Using the standard formula for calculating kinetic energy (KE = 1/2M*V² where M = mass in Kg and V = velocity in m/s) we find that a 210g piston traveling at these speeds has 29.98 joules of energy whereas a 221g piston has 31.56 joules.

Conversion from joules to ft/lbs gives us 22.11 ft/lb for the 210g piston and 23.28 ft/lb for the 221g piston. So you're right, not a great deal of savings.

That said, the main purpose of the piston purchase wasn't to reduce weight. I just happened to find it to be a pleasant added benefit.

 

[Sonreir]

More toys in the mail. Thanks to DCC for this shipment.

 

[Red Head Bastard]

Not really a purchase. Traded a three carb linkage for a three wheel cushman. Gonna need a little work tho.

It's under there somewhere. Trust me.

 

[lingo]

Let's do the math and find out, shall we?

The stoke on my 360 is 50.7mm and for argument's sake, we'll say I want to spin that baby up to 10,000 RPM. To get the speed of the piston, we need to do some math to first get the piston speed in meters per second.

First, divide 10,000 RPM by 60 in order to get RPS and we arrive at 166.66 RPS. So now we know that for every second that elapses, our crank shaft completes 166 and 2/3 rotation. Obviously, for every rotation of the crank shaft, the piston moves down and then back up again, covering 50.7mm x 2.

So now we multiply 50.7 x 2 x 166.66 and find that every second the piston travels 16,900 mm, or 16.9 meters.

Using the standard formula for calculating kinetic energy (KE = 1/2M*V² where M = mass in Kg and V = velocity in m/s) we find that a 210g piston traveling at these speeds has 29.98 joules of energy whereas a 221g piston has 31.56 joules.

Conversion from joules to ft/lbs gives us 22.11 ft/lb for the 210g piston and 23.28 ft/lb for the 221g piston. So you're right, not a great deal of savings.

That said, the main purpose of the piston purchase wasn't to reduce weight. I just happened to find it to be a pleasant added benefit.

The slight weight reduction translates into 5% less power needed to achieve 10k rpms. That extra power ends up at the back tire. Less rotating mass also allows the engine to rev faster and if built properly higher.

 

[Sonreir]

One other thing to mention... the rings on the new pistons are thinner and therefore incur less drag. I'm told the drag losses from the rings account for 75% of the drag loss in an engine.

Also, bear in mind, that my calculations above only consider mean piston speed. Peak piston speed is actually a lot higher than that because the piston spends most of its time accelerating and decelerating and, obviously, does not have a constant velocity. There's a lot of energy going into making that piston change directions and as lingo correctly points out, the less energy spent doing that, the more we have to spend actually moving the bike around.

Anyway... proof is in the pudding. When I (finally) get this project done the dyno will tell the tale.

 

[JustinLonghorn]

That Cushman is bad ass!

 

[Nein_Collins]

More toys in the mail. Thanks to DCC for this shipment. ]

awesome, I'm waiting for some goodies from them as well...how long was your wait time?

 

[Sonreir]

Exactly two weeks from order date to delivery date. They were backordered on the mufflers and so I had to wait a bit longer than usual.

 

[Nein_Collins]

Exactly two weeks from order date to delivery date. They were backordered on the mufflers and so I had to wait a bit longer than usual.

cool deal, I just ordered my stuff tuesday this week so I guess I've got a few more days to wait..lol

 

[dewjantim]

my wife rode my enfield all the time! she loved it... it did not get near 100 miles per gallon though

Mine got 70 when I got it new in 2001. I put on a new pipe, K&N airfilter and rejetted the carb. I get between 90-100 mpg now. Went on an all day ride with some friends a while back, they all had Yamaha Star bikes and had to stop every 100-150 miles to get gas. I filled up at the first of the day and rode 350 miles ..... it took 3.5 gallons for a fillup. At first I could not believe it but it regularly returns 90+ mpg even running around town. I have had it since 2001 and put 7500 miles on it, it is on the second set of tires and looks better than it did when I bought it.

 

[dewjantim]

The new Enfields have the "magic button"....hint hint ; )

Yes, but I can start mine with my hand........

 

[dgrady77]

And now looking for recommendations for a good red dot scope.

When I got home from buying the AR, I found that my back seat for my Harley had arrived from Corbin. Good day for me.

 

[Blake]

1960 Kay Galaxie hollow body guitar.

 

[Swapmeet Louie]

Rad! thats the best purchase on the board ever....

 

[JustinLonghorn]

That Kay is rad!

 

[dewjantim]

And now looking for recommendations for a good red dot scope.

When I got home from buying the AR, I found that my back seat for my Harley had arrived from Corbin. Good day for me.

I knew you had to be a good ole' southern boy....... I could tell by your firearm. Bet you use that to go squirrel huntin'.......hehehe. Nice piece by the way.

 

[dp9]

 

[dgrady77]

I knew you had to be a good ole' southern boy....... I could tell by your firearm. Bet you use that to go squirrel huntin'.......hehehe. Nice piece by the way.

I don't know if I'd call myself a southerner, but I've lived most of my life in the south and can't complain. Either way, I like to think of myself as an old-school patriot. Liberty or death, b****es, liberty or death.

 

[imseamless]

1960 Kay Galaxie hollow body guitar.

Nice man! I've got a 60's Kay archtop myself. Wish mine had electronics, good score