Cross Thru?

[srodeo]

What exactly is cross thru?

Just combination of Cross under and over?

[jacopodotti]

Yes, also called midweighting

[leeho730]

And some may not like what I say, but EC turns also utilise xthru...

[Beckmann AG]

also called midweighting

"Midweighting" is to the OTTO cycle, as Cross-through is to the DIESEL cycle.

[Jack M]

http://www.bomberonline.com/resources/Techarticles/cross_under.html

[lonbordin]

"Midweighting" is to the OTTO cycle, as Cross-through is to the DIESEL cycle.

Ref:"Mister Rudolph Diesel was aware of the gasoline engine ([http://en.wikipedia.org/wiki/Otto_cycle Otto cycle]) problems and wanted to improve it. The gasoline engine inherently has problems with efficiency and/or fuel. In order to improve the efficiency one must increase the compression ratio of an internal-combustion engine (see the bonus section at bottom of this article). However, in the gasoline engine there is a limit - the gasoline-air mixture will self ignite once the compression gets too high (because every compression drives temperature increase). So, either you can have a low-efficient, low-compression engine that uses a cheap fuel, or you can have a high-efficient, high-compression engine that uses expensive, high-refined fuel that wont self-ignite even at high compression levels (a 120 octane gasoline?). In [http://en.wikipedia.org/wiki/Diesel_engine diesel engine] this problem is solved. The diesel engine can use much higher compression levels than the gasoline engine reaching higher efficiency. In addition, the diesel engine can use fuel that is not nearly as refined as the high-octane gasoline fuel (thus cheaper). To make this possible, Rudolph changed the Otto cycle and created the diesel cycle. The difference is that during compression phase, no fuel is present in the cylinder and thus no self-ignition can happen. The fuel is only injected at the moment the ignition is wanted - when injected into the hot pressurized air the diesel fuel self-ignites immediately (the diesel-air mixture, as we said already, is happy to ignite even at relatively low temperatures)."-wiki.answers

You seem to be implying cross-through is more efficient than "midweighting"? I'd like to read your impetus for that line of thinking.

[KingCrimson]

"Midweighting" is to the OTTO cycle, as Cross-through is to the DIESEL cycle.

Midweighting, adding energy to make the combustion happen, versus just letting things happen with compression anyway?

That wouldnt make sense to me though..I associate a gasoline engine with more of a gradual expansion vs. the rattly explosion of diesel (or a gasoline engine "detonating" and dieseling) I would associate an explosion with midweighting instead of crossthrough.

I have to say, you say some pretty cryptic and vague stuff, but this takes the cake.

Edited March 28, 2012 by KingCrimson

[Beckmann AG]

You seem to be implying cross-through is more efficient than "midweighting"? I'd like to read your impetus for that line of thinking.

The short version:

If the goal is to get to the finish of a course containing and utilizing the greater part of the potential energy you had as you stood behind the start wand, then cross-through, when possible, would be more efficient.

(In the diesel cycle, the pressure in the combustion chamber remains largely constant for the greater part of the power stroke, due to the ongoing, and accurate injection of combustibles.)

Whenever you have a pressure spike underfoot, that represents inadequate control/loss of the energy contained within the system. It has to go somewhere; either sending the rider skyward, excavating the surface beneath the edge, or breaking free and altering the path of travel in a lateral skid. All of which can be described as some form of 'work', and/or a loss of directional control.

(In the OTTO cycle, the fuel load is pre-set, and the pressure in the combustion chamber drops as the power stroke continues from the point of ignition and subsequent 'explosive' burn.)

When the pressure underfoot drops to, or approaches zero, (post spike) that represents the start of a time frame whereby the board is not loaded (no spring tension until decamber), and therefore an area where the options for direction change are limited.

Of course, the best rider on the day is the one who squanders the least energy from start to finish, and that involves employing any and all options that allow the rider to take the 'fastest' line, which implies more complete management of any and all options involved in changing direction over the shortest (if necessary) span of time.

If the goal is to bounce through a course like a bunny, then "midweighting" (a variant on the classic 'up-unweight') is more efficient than cross-through.

(The previous may or may not make sense, depending on your operating definition of cross-through,and/or "midweighting" and your interpretations thereof.)

I have to say, you say some pretty cryptic and vague stuff, but this takes the cake.

What do you suppose a sonic boom looks like, as seen through the eyes of Milton's God?

[KingCrimson]

I agree with Beckmann.

Assuming you're negotiating a specific course minimizing how much energy you're putting into the system, I would think crossthrough is more efficient.

It believe it's slow slower in a race course though. For flatter courses, the goal largely seems to be bouncing through the course like a bunny- fundamentally maximizing the amount of energy in the system.

I think for the purposes of carving when edge grip is a concern, such as steeps or bad conditions, decreasing edge pressure throughout the turn is preferable to maintaining it consistently. The board is much more able to grip before the fall line than after. Why not pressure it more initially and back off throughout the turn? I guess I'm an otto cycle carver.

By the way, I'm a huge proponent of pumping, wheelies, and ollies in my carving.

Can't say I'm well read enough at all to answer that one, Beckmann.

Edited March 28, 2012 by KingCrimson

[jacopodotti]

Of course, the best rider on the day is the one who squanders the least energy from start to finish, and that involves employing any and all options that allow the rider to take the 'fastest' line, which implies more complete management of any and all options involved in changing direction over the shortest (if necessary) span of time.

Sorry to disagree with you.

The best rider of the day is the one that has the bigger fun! :)

[lafcadio]

The best rider of the day is the one that has the bigger fun! :)

Yes! Love it! :D

[xy9ine]

o/t, but i like the way you think / write, beckman. curious what your background is.

[lowrider]

Where do variable valve timing , precombustion chambers and direct and indirect fuel injection fit into this analogy ?

[lonbordin]

What do you suppose a sonic boom looks like, as seen through the eyes of Milton's God?

As an essential piece of handiwork? (Is there a prize?!) ;)

[Beckmann AG]

The best rider of the day is the one that has the bigger fun!

Indeed. And will this new 'timing' system be in use at Sochi?

Why not pressure it more initially and back off throughout the turn?

Kinda hard to get this with an up-unweight.

It believe it's slow slower in a race course though. For flatter courses, the goal largely seems to be bouncing through the course like a bunny- fundamentally maximizing the amount of energy in the system.

With many things in skiing and snowboarding, it is all too easy to ascribe practical meaning to the seemingly obvious.

'Pumping' will only get you whatever is available from your own internal effort, and it is certainly debatable whether or not that avenue is worth pursuing; particularly if you wind up denting the snow any more than required for a direction change. Unless one is particularly deft, 'pumping' through a course is more likely to cost than gain.

As you proceed with your racerness, be aware lest your 'beliefs' interfere with your growth.

Where do variable valve timing , precombustion chambers and direct and indirect fuel injection fit into this analogy ?

Those affect volumetric efficiency, cold starting ability, and utilization of available fuel, but they don't significantly alter the generalized pressure within the CC on the power stroke; so while they are interesting asides for the discussion of internal combustion, they don't really fit.

Unless I misread something somewhere.

As an essential piece of handiwork?

Probably not, but thank you for trying.

Re: Background; "I am a mechanic, working with machines of varying type in varying context."

Edited March 29, 2012 by Beckmann AG