Venturi Assistance Lever / Resistance Control Knob ?!

[cariss2709]

So I've got an Apeks ATX200 that I've been using. It just occurred to me that I should know more about what the lever thingy and the knob doo-dad does.

When would you want to keep the venturi lever in the +/- position? I know + means possible freeflow and - eliminates it. But when would you want to adjust the lever?

Also, the resistance control knob. I know it controls the breathing resistance, but when would you adjust it? I'm guessing when its completely out it might possibly breathe a bit wet with possibly freeflow? And when its in you'll have a tougher time breathing? So probably cold water you might want to loosen it and tighten with warm water. Or maybe its just diver preference. Of course, I might just be completely making this up...

Anyways, hope this is the right spot to post it. Thanks!

 

[vicdiver656]

As far as I know, the Venturi controls the amount of vaccum flow, and the resistance just controls how easily the regulator breathes. Here's a run-down from Apeks.

The flagship of the Apeks ATX regulator range and the definitive blend of style and high performance. Every detail has been carefully designed to offer a high quality piece of equipment. From the attractive, luxurious and hardwearing satin silver chrome of the first stage through to its overall build quality. We believe that your regulator should be as flexible as you are. The smaller lighter ATX200 second stage (25% lighter than our TX100) retains our well proven combination of diver adjustable venturi and cracking resistance controls with an ergonomically designed venturi lever and breathing resistance knob for ease of use.

Click to view close-up picture of this product

Click to view close-up picture of this product
The ATX200 also has the benefit of an additional MICRO ADJUSTMENT that allows each individual regulator to be altered during service to keep your regulator at optimum performance. The dry-seated first stage suitable for cold water diving, now with removable ARCAP seat, heads the Apeks range and has been redesigned to improve the gas flow and reduce both its size and weight. All ports are angled for optimum hose configuration. With the balanced first and second stage the ATX200 offers excellent air delivery no matter what the dive conditions. The ultimate Apeks regulator.

Specifications

First Stage

* Compact one piece body
* 4 angled medium pressure ports, 1 x 1/2" UNF + 3 x 3/8" UNF
* 2 angled high pressure ports, 2 x 7/16" UNF
* Environmentally dry sealed system
* Attractive black and luxurious satin silver chrome finish
* Balanced for superior performance
* Removable ARCAP valve seat



Second Stage

* Suitable for extreme diving
* Pneumatically balanced system - reduces breathing effort
* Heat exchanger for cold water diving
* Integrated Venturi Control
* Cracking Resistance Control - alters breathing resistance to suit individual diver preference
* Micro adjuster
* Extremely efficient exhaust valve
* Compact integrated exhaust
* 25% lighter than TX models
* Comfo Bite mouthpiece

As far as I know, you would turn the resistance lever to + when breathing at deep depths, and - at shallow depths. That lever is useful when at over 100 fsw, but not really necessary when doing shallow under 100 fsw dives. The venturi lever only controls the amount of vaccum that brings air to your mouth, only changing the rate of air delivery. I do have to say, I am not completely sure about this, so if any other members want to correct me, please do!


Hope that helps.
Taylor
Vicdiver656

 

[DA Aquamaster]

Company marketing aside...

The venturi adjustments on most second stages work well to prevent freeflow. On the "+" setting they will continue to freeflow once the purge is depressed until you place an obstruction over the mouthpiece. On the "-" setting they will stop on their own if the purge is accidently depressed.

In terms of breathing perfromance the venturi effect in the second stage ensures that little or no effort is needed to continue air flow once it is initiated. In that case you actually stop airflow by stopping the inhaltion and in effect creating back pressure to push the diaphragm back out. That is where it gets problematic as too much venturi flow can leave you feeling like the regulator is trying to inflate you and is not very natural feeling. Some divers like, but most don't.

So on an octo it is common to set the flow vane to the "min" position as a freflow will then stop on its own in most cases. On a primary reg, most flow vanes get set somewhere in the middle and are seldom if ever adjusted - which usually replicates the built in effect of a second stage with a non-adjustable flow vane making it more or less useless on a primary reg.

The inhalation adjustment knob is useful to add some resistance if you are in a position where the case geometry promotes a slight freeflow, such as looking up at the surface. Conversely if you are looking straight down, the second stage may tend to freeflow slightly compared to what it does in a normal swimming position where the diaphragm is somewhere between 45 and 90 degrees from being parallel with the seabed.

Another condition where inhalation adjustment is nice is when swimming into a strong current or using a scooter. The water flow can create pressure against the diaphragm and cause the reg to freeflow. That condition aside, most divers set it to a point where they get maximum performance in a normal swimming position and do not adjust it unless they change the orientation fo their head for long periods of time.

Some divers will set it heavier in cold water to reduce the potential for a slight freeflow that could increase adibatic cooling and potentially cause a major freeflow event if the first stage freezes up.

Practically speaking, an adjustabel reg is less critical in terms of adjustment. If a tech adjusts a non adjustabel reg and gets it a bit too light, it may freeflow once the seat breaks in and require re-adjustment (ie: a trip to the shop for the customer). If the same thing occurs with an adjustable reg, the customer just turns the knob in about a half turn and resolves the problem with no need to adjust the orifice. The end result is that many techs will lay up and be very conservative with a non adjustabel reg (ie: it will breathe like rock) while the same tech with an adjustable reg will be more willing to adjust it to enable it to deliver minimum inhalation effort.

 

[redacted]

So I've got an Apeks ATX200 that I've been using. It just occurred to me that I should know more about what the lever thingy and the knob doo-dad does.

When would you want to keep the venturi lever in the +/- position? I know + means possible freeflow and - eliminates it. But when would you want to adjust the lever?

Also, the resistance control knob. I know it controls the breathing resistance, but when would you adjust it? I'm guessing when its completely out it might possibly breathe a bit wet with possibly freeflow? And when its in you'll have a tougher time breathing? So probably cold water you might want to loosen it and tighten with warm water. Or maybe its just diver preference. Of course, I might just be completely making this up...

Anyways, hope this is the right spot to post it. Thanks!

I think you got the thingy right but we'll have to work a little on the doo-dad.

The venturi lever controls the vacuum established behind the diaphragm by the air flow. This vacuum reduces the amount of work you have to do to keep air flowing. But it can also give you the feeling of air being forced into your mouth (positive pressure breathing) which some divers find to be uncomfortable. So this lever is normally kept in the easiest breathing position when you are using the reg as long as you are not experiencing freeflow.

The doo-dad (breathing resistance knob) adjusts the force on the spring that is trying to keep the regulator valve closed. It has no effect on exhaling or wet breathing. It will effect cracking pressure (work to start air flow) which is not effected by the venturi lever as well as the continued work of inhaling. Again, this knob is normally kept in the easiest breathing position when the reg is in use (in your mouth). In conditions of current ands surge, you may want to dial it in a bit to prevent freeflows caused by those adverse conditions. Or, if you find that over time your reg starts to leak just a little when you turn on the gas, you can use that knob to stop the leak until you can get your tech to make a minor adjustment.

 

[cariss2709]

Think the answer is that I don't need to worry about re-adjusting them after my original tweaks. So I'll just leave the settings as-is. Thank you much peeps.

 

[KrisB]

One thing that hasn't been mentioned is that the venturi control lever is often treated as a "pre-dive / dive" switch. When the reg goes in your mouth for the dive, switch it all the way to the plus. When it comes out of your mouth at the end of the dive, switch it all the way to the minus.

The other thing to keep in mind with this -- if you put the venturi assist half-way between the + & -, it had might as well be all the way to the '-'. The whole principle of it is similar to that of an aircraft wing (the Bernoulli effect) -- air passing over two sides of the vane causes it to accelerate on the other side... if there's no resistance, it will cause the reg to think you're still drawing a breath (and free-flow). If the vane isn't lined up perfectly (i.e. all the way '+') with the direction of airflow, the Bernoulli effect doesn't happen, and the vane does nothing except (slightly) restrict airflow.