Is there a balanced piston 1st stage with I-shape appearance?

[nohappy]

I think that all unbalanced piston first stage has I-shape appearance like the below picture. (Correct me if I'm wrong) i.e. The air inlet is inline with the main body.

And most of the balanced piston first stage has L-shape appearance like the below picture. i.e. The air inlet is coming from the side of the body.

I guess there is an exception with some of the Sherwood first stages that comes with "moving orifice" design. It has I-shape but it's also a balanced piston first stage.
I wonder if there exists a balanced piston first stage that has no "moving orifice" but looks like "I-shape"? I'm aware that one of the reason unbalanced piston first stage being "unbalanced" is that the HP heat sits directly on air inlet hence IP is affected by air supply pressure. But I'm just wondering if anyone design an I-shape first stage that maybe has an "angled" air inlet so that it can achieve balanced function.

Maybe something like changing this...

to this... (Blue line is the new airway inlet)

So that it can be a balanced first stage but still has I-shape appearance?

Reasons that I want to ask this is besides curiosity I also want to know if I can determine a piston first stage is balanced or not by outlook only.

 

[Luis H]

Yes, TUSA did something like that. Not exactly what you are showing (that by itself will not work, you need to change the piston). Maybe @herman can post a diagram of the TUSA. He is very familiar with it.

Also Spirotechnique had a different balanced piston that looked like your first picture, but it used a different design. It uses something like a plunger on the back side of the piston. It is a bit hard to describe, but maybe when I have some time I can find the diagram.

There may be others.

 

[herman]

Funny you should ask, I am working on 2 projects with them. I know of 2 different models. Tusa made the R100, 350 and 390, all of which are the some first stage with some minor changes. Sherwood made the 3105 model which is really interesting because it has an external way to adjust the IP. I have heard rumors of a another but have yet to find it.
Here is a quick ( and poor )modification to your drawing. The red line is the air flow, the black blob is the HP seat.

To answer you question, no, you can't tell if it's balanced just by looking on the outside. However, any flow thru piston is going to be balanced and if the LP ports are at the end (bottom) of an axial flow piston reg then odds are it's balanced.

And if anyone has one of these that they would like to sell cheap ($20 or less) please PM me. I still would like another one or a different model.

EDIT: I forgot about the Healthways Airflo, it is a flow by piston like you have drawn. It's an odd reg and few were made but there was at least one made like you have drawn. it only had one port in the end and did not have a yoke. It screwed directly into a special tank valve, similar to a DIN. These are fairly rare so you are not likely to find one.

 

[nohappy]

@Luis H @herman Thank you both for your reply. Thanks to your hint, I found this interesting articles which kind of listing some of the inline balanced first stage. I also found Tusa R100 drawing. I believe that's what herman trying to describe.

I couldn't find information about Spirotechnique products Luis just mentioned or Sherwood 3105 that herman mentioned though.

 

[Luis H]

To answer you question, no, you can't tell if it's balanced just by looking on the outside. However, any flow thru piston is going to be balanced and if the LP ports are at the end (bottom) of an axial flow piston reg then odds are it's balanced.

And if anyone has one of these that they would like to sell cheap ($20 or less) please PM me. I still would like another one or a different model.

EDIT: I forgot about the Healthways Airflo, it is a flow by piston like you have drawn. It's an odd reg and few were made but there was at least one made like you have drawn. it only had one port in the end and did not have a yoke. It screwed directly into a special tank valve, similar to a DIN. These are fairly rare so you are not likely to find one.

The US Divers DeepStar II is a non-balanced flow through piston with the two LP at the end of the axial body.

The piston of the Healtheways Airflow is just like any other non-balanced piston. The only two differences is that they placed the LP port at the end of the piston cap. It is an extremely poor performer due to the very small airflow passages. The second unique feature is the threaded connection to the tank valve. I have one with a toke adapter. It can be attached either way.

 

[herman]

Want to play one up do you Luis? I'll call your yoke adapter and raise you an Airflo tank checker!

(nohappy, Luis and I are good friends)

 

[Luis H]

I also have one of those.

 

[Couv]

I also have one of those.

What don't you have?

 

[Luis H]

@Luis H @herman Thank you both for your reply. Thanks to your hint, I found this interesting articles which kind of listing some of the inline balanced first stage. I also found Tusa R100 drawing. I believe that's what herman trying to describe.


I couldn't find information about Spirotechnique products Luis just mentioned or Sherwood 3105 that herman mentioned though.

Take a look at the Spirotechnique Explorer in this web site:
https://www.spiro-vintage.com/reg-anglais

This is another balanced piston of a different design. Keep in mind we are mostly exposed to regulators that are all copies of each other. In other parts of the world there were (in the past) some very different designs.


Hey @couv, that is one of many regulators that I don't have. Can you find me one?

 

[tmassey]

Never mind: I somehow missed the entire paragraph that mentioned the Sherwoods....

Original post: Sherwood Dry Air Bleed regs from the 70’s through the 90’s. They used belleville washers to adjust for tank pressure.