Gauge-less pressure calculation yields absurd results.

I’m reposting this from my personal thread, as I think it could be relevant here. Please remove if not allowed.

I was curious to see how much pressure is actually developed by my little T-Grip pump. I don’t have a gauge, but I have a ruler, and some basic physics to help me out.

At first, in a fit of stupidity, I thought I could measure how much water height in the tube changes after a certain number of pumps. But this would need to take into account drop in air pressure, and make assumptions about vapor pressure of water and yadda yadda.

I measured the volume of my tube (Vt = 0.545 L), and the displacement of my pump. Through water displacement, it averages out to Vp1 = 0.035 L, but measuring bore and stroke yields Vp2 = 0.0264 L.
I have to make an assumption on penis volume. Considering a cylindrical, wholly erect penis, I have a volume Vpen = 0.264 L.

We can use 2 different models for the air: isothermal and adiabatic. I’m assuming a constant temperature, so we’ll use isothermal, where the product of pressure and volume is constant. Adiabatic will yield somewhat higher vacuum pressure.

So, the model is that a volume of air V0 = Vcyl - Vpen is expanded to a volume V1 = V0 + Vp. Its pressure drops from Pn to Pn+1, where Pn+1 = (V0/V1)Pn.

As a result, the vacuum pressure decreases logarithmically with the number of pumps, with each pump decreasing the pressure less than the previous one. After just 3 pumps, depending on the assumed pump displacement, a vacuum pressure between 7 and 8 inHg is achieved.

A quick test shows that I start to feel pressure around after 6 pumps, and can easily go up to 9 or 10. Assuming these somewhat unrealistic conditions, that would mean that I regularly pump at over 17 inHg!
Am I going crazy? I accept the possibility that I might be pushing a bit harder than recommended, but this seems absurd.

Could I really be pumping at nearly 20 inHg, for up to 20 minutes at a time, with no discomfort or negative indications? Even dropping my cylindrical penis hypothesis, and taking a lower value of Vpen = 0.2 L, and assuming isothermal expansion, this would still be around 16 inHg, far above recommended levels.

When I pump, I never go to pain. At most, I have a nice firm sensation. I never have red spots, fluid build up, or hard flaccids. And I’ve been doing this for weeks. Someone tell me my math is wrong.

Possible issues: assuming no leaks, be it in pump or at seal. Assuming full, cylindrical erection at all times. Assuming perfect pumping displacement. Assuming no body fat ingress during session. Assuming constant temperature (I heat during pumping)

Guess I really do need a gauge.

Keywords: gauge, pressure, measurement, water, inHg, bar, science, assumption, help

Bath mate pumps are known to be really high pressure. My point is that everyone is different. Just because people say high pressure is unsafe doesn’t mean some people are freaks and can’t take high pressure.

There’s a guy I write emails with and he pumped for a long time, a few years straight and almost every single day, with Bathmate and then an air pump but all with no pressure gauge. He had complained about “things” wrong with his dick, like weird patches of skin, red marks/spots, and discoloration. I assumed he was reaching 10+ lbs of pressure throughout his pumping routine. He never complained of pain or anything like it. However, he suffers from mild ED (at least he tells me he does) and went to the doctor to deal with discoloration and he has been bruising himself so much from overpumping that he needs creams and something else to try to make part of his cock look like the color of skin again. Even with a pressure gauge he pumped to 15hg, and he swears he feels no discomfort. I feel like my cock is going to explode if I pump over 7-8hg and can only handle a few seconds. He said he must have an inability to feel pain in his penis, but I told him that sometimes parts of our bodies become injured and we never know it (like bumping into something and getting a huge bruise but we never knew we hit anything; or, I have friends who’ve been bitten by snakes and never knew it until their leg swelled up hours later). I think men can condition themselves to not feel pain during sexually oriented activities. I’ve slammed my cock into things inside my wife so many times and every time I say to myself “wow that smarts!” but she wants it and it still feels good and then an hour later my cock is a little sore and feels beat up. Plus while pumping we WANT to make it bigger and if there’s a small shred of pain we may see past it because, as we know, sexual excitement is powerful and a hard thing to turn off.

We just all need to be safe while pumping! As I told my friend, “discoloration IS bruising and/or injury of some kind.” Pain shouldn’t be the sole indicator of injury.

Well, I’ve yet to experience any kind of contraindication. But you can be sure that the moment I do, I’ll stop and fix my routine.

Been a while since I used Ideal Gas Law approximations etcetera, but the available volume of the cylinder is a constant (as you correctly stated). Where you might be wrong is that when you insert your penis, you already displace that amount of volume (at atmospheric pressure) which either a) gets pushed out while inserting or b) increases the pressure to above 1 atm in the remaining volume. Your starting volume upon which you apply pressure is then 0.545 - 0.264 = 0.281L
Your three pumps correspond to 0.0792L, plugging it in gives me (0.281/0.2018)*29.92 = Pn+1 = 11.74 inHg (I took the net difference and did not account for logarithmical decreases), so your values do make sense. It does seem highly unlikely that your T-grip pump (don’t know the build quality but I’m guessing it’s not the highest quality) is able to achieve an averaged ~4 inHg per pump…Have you taken the correct volume that it ‘removes’ every pump? This is probably the biggest error factor if you want to go at it through calculation.

One way to figure this out is to see how volume taken by your penis increases during your session. This way you have a clear difference in volumes occupied and would simply be able to calculate/estimate it through (V_i*p_i)/V_f = p_f, where p_i is atmospheric pressure, p_f the “to be calculated final pressure”, V_i the initial volume which is not occupied by your penis (Which you call V0) and V_f the final volume not occupied by your penis.

A test calculation where I assume post pump you gain 1/2 inch in girth:
Starting volume (from your Progress report, 17cm BPEL and 14.5cm MSEG, discounting cylinder not going as deep into fat pad as a ruler, etc): 0.284L
Final volume with 1/2 inch girth added: 0.336L
(V_i*p_i)/V_f = p_f; (0.284*29.92)/0.336 = 25.29 inHg or in absolute would correspond to 4.63 inHg of vacuum.

Also from your progress report you mentioned your cylinder has a diameter of 2.25 inch, which has a radius of 2.8575cm. Your MSEG has a radius of 2.30755cm. The maximum expansion you thus can get if you pack the tube is 1.36 inch in girth; if this happens then the total vacuum on it (again, discounting all other forces like elastic resistivity of your penis which is probably some form of Hooke’s law, etc, etc) would be 12.6 inHg.

To summarize, get a gauge :)

Another variable is how hard you are at insertion. If you’re 50% or 100% you take up a different amount of airspace. A hand pump with a gauge is $20 bucks. And this is your cock you’re messing with… it’s worth the investment!

How’s your progress with the current system of excessive pressure?

I’ve had no gains so far. But also no bad signs. I can tolerate the pressure I use for up to an hour.