Did you not notice the holes in the piston your light blue arrow was pointing at? Several of your other comments were about as good.

Sorry you're so miffed and feel the need to behave thusly.

 

I asked you a simple question for you to explain:
If this is so, could you please tell me how the oil is pressurized as everything is than equalized and how the white cup is pushed down and sealed on the outside & inside so the spring could be compressed? I am confused with this explanation, please clear it up.

If the whole shock is pressurized (around 0~50# PSI) how would spring pre-load work or the only function of air pressure would be to compress the spring (spring pre-load)?

Do you understand how to read a question and how to answer one? No miffed, and no behaving badly. Answer the question please as you made the statement.

It would also be a good idea to take your time and not to assume what those "holes in the piston your light blue arrow was pointing at?"but to know those white arrows with blue outlines are pointing at is a white cup, when pressurized, pushed down on the white cup and adds spring pre-load. You will not like me very much when throwing around accusations and I will have to answer you, it is your choice. Act respectful and you will be answered courteously.

 

You’re going to threaten me now? Seriously?! Over a post of mine about how an air shock works? Good lord, how childish are you?

The only one throwing around accusations (and insults) is you. You’ve peppered both your posts in this thread with them. You’ve not shown anything like the respectful and courteous manners you demand you receive.

The term is “king baby”. http://www.drugaddictiontreatment.co...baby-syndrome/

But I tell ya what, I’ll go ahead and take you at face value, that you really don’t understand how shocks and springs and such work, and answer some of your…”questions”.

You didn’t write this well the first time, and didn’t fix any of it in your second post. It’s not real clear what you’re stating or asking. But, I’ll take a stab at it.

The Harley (Showa) air shock air chamber is sealed. The air chamber is what you cut apart in your pictures. The top mounting eye unscrews from the shock shaft. Perhaps you didn’t realize that and this is why you chose to cut the chamber off instead. The air tight seals for the top are still mounted and covered under the cap in your picture. The lower seals that slide against the shock body are on the left of your picture, along with the spring perch and retainer clips. The white cup you are referring to, is that the spring bushing at the top of the spring? That doesn’t seal anything, and doesn’t need to. The spring is riding in the air chamber.

I’m not sure why you’re confused about compressing the springs. When the space between the spring perches (top and bottom) is smaller than the spring, the spring gets compressed. That’s why spring compressors are used to put assemblies like this together.

Since the air shock is open on the top (which is why the shock oil drains out if it’s inverted), the air pressure acts directly on the hydraulic oil, with no effect on the oil, except a faint reduction in foaming. The effect is faint because the pressure is faint. Unlike sealed high pressure nitrogen charged shocks where the reduction in oil foaming is appreciable.

Since the assembly is sealed, the pressure stays in there (minus leakage), and acts equally in all directions, as is the nature of pneumatic pressure vessels.

Air pressure would not compress the springs at all. Not sure why you would think it does. Nor would it affect preload as there isn’t enough range of motion to relax the coil spring, even if the resulting force from the air pressure were sufficient to exceed the preload values of the coil springs.

Perhaps you’re not clear on how the air pressure works to create force, a spring force.

It’s got everything to do with pushing the lower half of the assembly out of the pressure chamber. The diameter of that body being forced out is what determines the force that will result from the pressure. Pressure times area gives force. So with the lower shock being ~1 inch in diameter, if we do the classic pi R squared we get 3.14*0.5^2 which is 0.79 square inches.

Now put the pressure across that. Using your 50 psi * 0.79 square inches and we get39.5 pounds of force. Not much of an effect especially compared to the metal coil springs. But, that would be why it’s a tuning or trimming adjustment.

Before you leap onto the larger diameter of the spring perch, observe that the air pressure is acting equally on both sides of it as it is completely open to the chamber air pressure on both sides. The argument for the spring perch would only hold if it was sealed like a piston.
That’s quite a bit of a mess there.

Lets start with your notion of there being no such things as light, medium or heavy duty springs. A spring with a 50 lb/inch rate is lighter than a spring with a 100 lb/inch rate, which is lighter than a spring with a 200 lb/inch rate. Those three springs, relative to one another, could easily be referred to as light, medium and heavy duty. So yes, there most certainly are light, medium and heavy duty springs.

You are right that the spring is what holds the load up against gravity. However you are wrong in thinking it has no bearing on ride quality. I’ll explain that with the above three 50/100/200 lb per inch rates.

To keep the math simple, I’ll use one spring and since a touring Harley weighs about 800 lbs, I’ll set the tail weight at 400 lbs. Suspension travel, I’ll set at 4 inches.

For that 50 lb/inch spring to hold up 400 lbs, it needs to be compressed 8 inches. (400 lbs / 50 lb/inch = 8 inches). If we compress that spring in preload to 350 lbs (7 inches), when the bike rests on it, the bike will sag down one more inch, picking up that last 50 lbs (350 +50 = 400). The bike now has three inches of suspension travel remaining in compression.

The rider weighs 150 lbs and sits down on that. I’ll put his weight onto the rear, again for simplicity and clarity.

The 150 lb/inch spring absorbs that 150 lb rider by compressing 3 inches. (150 lb / 50 lb/inch = 3 inches compression).

But there was only 3 inches of suspension travel remaining. The bike is now completely bottomed out with that 50 lb/inch spring. Not good!

Lets go with the 100 lb/inch spring then, and keep everything else the same.

The 100 lb/inch spring will hold up the 400 lbs of the bike by compressing only 4 inches (as opposed to the 8 inches the 50 lb/inch spring compresses). To put the bike at the same ride height (1 inch down in the 4 inch suspension travel) the preload would be 3 inches.

Lets put that same 150 lb rider on the bike. This weight will compress the spring 1.5 inches under the riders weight (150 lbs / 100 lb/inch = 1.5 inches).

So we have total sag of 2.5 inches, and 1.5 inches of suspension travel remaining (2.5 + 1.5 = 4.0) . Certainly not bottomed out like the 50 lb/inch spring above was, but still not very much travel and very prone to bottoming out.

On to the last spring, the 200 lb/inch spring.

Preload this spring to 1 inch and let the remaining 200 lbs of the bike compress it down that 1 inch sag.

Add the 150 lb rider and the spring compresses 0.75 inches under the riders weight.

With the rider on board with the 200 lb/inch spring the bike has total sag of 1.75 inches, and 2.25 inches of suspension travel remaining in compression (1+0.75+2.25 = 4.0).

So clearly there is a difference resulting from light medium and heavy duty springs, and there is not just one spring and certainly not one exact spring.

Further, metal coil spring rates cannot be adjusted. Preload can be adjusted, and the ride height resulting from this. But the spring rate itself cannot be adjusted. Having an adjustable air charge over the metal spring rate though does allow for adjustment of the total spring rate by adjusting the air spring rate.

Could we adjust all the springs with preload to get the bike and rider up to 3 inches of suspension travel? And the ride for all three springs would be significantly different. The light (50 lb/inch) spring would give a very plush ride, but be quite prone to bottoming out. At the other end the heavy duty (200 lb/inch) spring would give a harsher ride, but be far less prone to bottoming out.

The most obvious and classic example of this is the harsh tail hopping ride of an empty pickup truck vs the same truck with a load in the bed. Empty, the truck is over sprung. Full, and the truck is barely adequately sprung.

Does the hydraulic damper come into play? Certainly! It’s what absorbs the rapid motions of bumps and dips and helps to dampen the oscillations of the vehicle.

In quick summary, the spring is the carrier of the loader, the damper is the absorber of quick motions or shocks.

Wise words to heed I suppose. ;-)

 

Foxtrapper, an educated reply.

Air shocks are definitely the king of easy adjustments. Great for someone who rides solo, loaded and two up often. The shocks Howard sells will give a safer ride and handle much better but require the saddlebags be removed and tools to adjust, a pain if you ride solo every day and ride two up every other.

The Showa shocks could use better damping.

 

Nice response, and thanks for your explanation.

 

King baby got schooled! LOL

That's what he gets.

 

Many have altered that by changing the oil in the shocks, and claim a significant improvement. I plan to try this next riding season.

 

I tried it. Didn't improve the ride or handling.

If you want a comfortable, floaty 1940's Caddy ride that's adjustable, stick with the 13" air shocks and use enough air not to bottom out. If you want a safer, more Euro car ride with better handling go for aftermarket shocks.

I liked the ride of the 13" air shocks but not the handling.

 

I am going to say that I finally got a respectable amount of discussion from one of my threads...haha. Can the Troll Killer move me up to Elite Member??