I don't believe a TP smaller than 3.0mm ever works in a 12FP springer....

[Shed tuner]

I just don't think it can flow properly and make the power... irrespective of length etc, I've never found anything less that 3.0mm to be efficient, and generally unless the port is exceptionally long (like an LGV), 3.2 is a more usual minimum starting point.

Even 25mm cylinder guns with fairly heavy pistons found 3.0mm too tight, and had to open out to 3.2. And larger bores 26/28/30 3.2 is always too small.

Discuss.

[look no hands]

Interesting stuff, I love the way you share your many years of research and tinkering skills with us

Pete

[Gunfun]

I've always imagined that for sub 12 ft/lb there must be a maths formula you could use to determine the perfect diameter and length of port if you know how much pressure the compression tube is creating, is this flow rate calculator of any use ?

https://www.copely.com/tools/flow-rate-calculator/

[BTDT]

I've always imagined that for sub 12 ft/lb there must be a maths formula you could use to determine the perfect diameter and length of port if you know how much pressure the compression tube is creating, is this flow rate calculator of any use ?

https://www.copely.com/tools/flow-rate-calculator/

I have three formulae for transfer port diameter, and they never agree with each other

There's too many unknowns to make such calculations reliable.

The flow rate calculator in the link is for fluids, not air.

[Gunfun]

I have three formulae for transfer port diameter, and they never agree with each other

There's too many unknowns to make such calculations reliable.

The flow rate calculator in the link is for fluids, not air.

I thought in physics fluids were considered liquid, gas (air) or plasma.

https://en.wikipedia.org/wiki/Fluid

[TonyL]

Interesting stuff, I love the way you share your many years of research and tinkering skills with us

Pete

Yes, Pete, I also think it's brilliant that we have so many people like Jon who will put the work in, experiment etc. and then share their findings with all and sundry. Like he says, anything tighter than 3mm probably creates too much choking effect on most layouts, but I only base that comment on what I've learned from these many great people who are willing to share their knowledge.

[look no hands]

Yes, Pete, I also think it's brilliant that we have so many people like Jon who will put the work in, experiment etc. and then share their findings with all and sundry. Like he says, anything tighter than 3mm probably creates too much choking effect on most layouts, but I only base that comment on what I've learned from these many great people who are willing to share their knowledge.

Indeed Tone, I've been looking at long drills now starting at 3mm and working up in increments, may have to purchase some and have a play one day, I suppose finding out what size TP my Mercs and Supersport have already would help.

Pete

[Shed tuner]

Indeed Tone, I've been looking at long drills now starting at 3mm and working up in increments, may have to purchase some and have a play one day, I suppose finding out what size TP my Mercs and Supersport have already would help.

Pete

a taper reamer makes things a bit easier.. just go from both sides

[look no hands]

a taper reamer makes things a bit easier.. just go from both sides

How do you us one inside the cylinder?

Pete

[Mr. Gen]

I go 3.5 mainly due to the fact that’s the size drill bit I’ve usually got lying about 🤣🤣

[Barryg]

I just don't think it can flow properly and make the power... irrespective of length etc, I've never found anything less that 3.0mm to be efficient, and generally unless the port is exceptionally long (like an LGV), 3.2 is a more usual minimum starting point.

Even 25mm cylinder guns with fairly heavy pistons found 3.0mm too tight, and had to open out to 3.2. And larger bores 26/28/30 3.2 is always too small.

Discuss.

What is the factory 80 size?

[les allam]

What is the factory 80 size?

I think the 80 has a 2.8mm TP standard from the factory, two of mine do.
Les..

[les allam]

Out of interest what size TP as the AA Pro/elite got ?.
Les..

[trajectory]

This has the makings of an interesting thread. I'd like to try & get an understanding of how the variables interact with one another.

Noticed a comment "The flow rate calculator in the link is for fluids, not air."earlier on in the discussion but isn't air classed as a fluid? I think all gasses are regarded a fluids. They are complex in some respects as they are compressible fluids as opposed to liquid fluids which are generally regarded as incompressible.

Looking forward to learning a bit about flow rates & fluid dynamics....

[BTDT]

This has the makings of an interesting thread. I'd like to try & get an understanding of how the variables interact with one another.

Noticed a comment "The flow rate calculator in the link is for fluids, not air."earlier on in the discussion but isn't air classed as a fluid? I think all gasses are regarded a fluids. They are complex in some respects as they are compressible fluids as opposed to liquid fluids which are generally regarded as incompressible.

Looking forward to learning a bit about flow rates & fluid dynamics....

Gasses are indeed regarded as fluids but, being compressible, will behave very differently in a transfer port.

The flow rate link would be spot on if we filled our springer cylinders with water, though.