When 5hg may not be actually 5hg

[bucket]

I've been using a brake bleed hand pump for ages. Hardly ever go above 5hg, still got blisters after an hour of pumping, even with regular 15m rests.

I recently got one of the electric hand pumps from AliEx that we've been discussing. The electric pump uses kpa so I calculated that 15-16 kpa is = 5in/Hg. I loaded my cylinder up with the electric pump at 15kpa and it felt nowhere as strong a pull as the hand pump when it was telling me 5in/Hg.

So I thought I'd better calibrate the two. I had an airtight jar with two hoses out of it (to create a vac chamber). One hose to the electric pump and the other to the hand pump. I'm assuming here that the electric pump is the more accurate of the two, but my findings were that the electric pump at 16kpa was reported as 3Hg on the hand pump. To get the manual pump to 5in/Hg the electric pump had to go to 25kpa which is really 7.5inHg. Likewise a hand pump 8in/Hg reading calculated 33.3kpa (9.85in/Hg) on the electric.

It seems to even out as you get too higher vacuum but for the lower ranges (<=5in/Hg) the manual pump is not accurate at all, nearly 50% out. Of course, ymmv, yours might be worse. You won't know until you test it.

[PumperSoCal]

Yeah you have to watch those for sure. I did this near exact thing recently since I've gone primarily to electric pumps for the hands off convenience. But according to mine. The hand pump was actually lower than the electric pump was. The electric smart pump I pumped up to 17 KPa and my vac tester said 4.94 in/HG, so it was actually pretty close to the 5 in/HG per the conversion charts, while the hand pump at 5 in/HG was really at 4.24 in/HG. So it is rather interesting that there is that much variation. But not good for us pumpers trying not to cause issues with our packages. So I guess chances are if you're getting blisters and don't have a vac tester setup. Then maybe backing the pressure down is the best option because it's either the gauge you're using isn't accurate, OR your body just can't take that pressure.

[Pumpforgirth2021]

Yeah you have to watch those for sure. I did this near exact thing recently since I've gone primarily to electric pumps for the hands off convenience. But according to mine. The hand pump was actually lower than the electric pump was. The electric smart pump I pumped up to 17 KPa and my vac tester said 4.94 in/HG, so it was actually pretty close to the 5 in/HG per the conversion charts, while the hand pump at 5 in/HG was really at 4.24 in/HG. So it is rather interesting that there is that much variation. But not good for us pumpers trying not to cause issues with our packages. So I guess chances are if you're getting blisters and don't have a vac tester setup. Then maybe backing the pressure down is the best option because it's either the gauge you're using isn't accurate, OR your body just can't take that pressure.

Yeah my vacutec electric pump on pulsar mode at high 5-7 hg has me filling up tubes unlike manual pump I can go to 12 hg but can't pack tubes as fast and get a lot of blisters. I have started to live my vacutec pulsar mode which is helping me pack my 2.50 in 6 months then it's onto the 2.75 can't wait. One thing I learned over 4 years of pumping once the first 2 years your skin adapts to pumping then high HG is not need plus blisters put you out from pumping for weeks. I also noticed 1 day on one day off is the best routine for me 4 to 5 days is sufficient to good less injury growth.

[PumperSoCal]

^ That's been my experience as well. My electric pump in "pulse" mode has yielded far better results than my hand pump ever did. And I'm pumping far more frequently now than I was because I'd have instances of blisters or irritation.

[tout69]

I have to agree. The electronic pump is able to keep a consistent pressure which has allowed me to use lower pressures which then allow me to pump for longer helping me get closer to the results I am looking for.