Redline said:
The OJ test indicated high temperatures for this ARB pump, but the fill time was okay.
High temperature is the issue I was describing earlier, and arises from exceeding the duty cycle. In the article, mention is made that the unit is a 50% duty cycle device, 30 minutes on and 30 off. I believe this is a mis-statement.
Although ARB lists the duty cycle, it does not publish the cycle time that goes with it, or the thermal limit that goes with it, whichever is used or comes first. It would require some knowledge of the engineering of the unit to know just how hot is too hot for the unit, but if the target temperature is, say, 200 degrees (approximately what some of the other tested units ran to), then when the pump reaches this temperature, it has hit its duty cycle limit and should be shut off for the same amount of time it took to get to that temperature. It won't be 30 minutes. (If the pump could run indefinitely, it would be rated as a 100% duty cycle pump. Since it isn't, it would be helpful to know how the 50% duty cycle rating should be interpreted.)
Unfortunately, how many minutes it took to get to a target temperature was not one of the test parameters, and I have not seen published data for any of the pumps that would allow a tester to pick a suitable cut-off temperature. I just have to think that 300+ degrees is way too hot for a small oil-less pump, and running the pump to these temperatures on anything like a regular basis will cause the pump to fail.
Also note that in the article, tires were inflated to 35psi which is 20% higher than the rated performance of the unit (29psi), also contributing to the elevated temperatures. The harder it works, the faster it gets hot and the shorter the duty cycle. Certainly the pump will produce more than 29psi since the lockers run at around 100psi, but ARB chose to list 29psi for a reason, mostly having to do with amperage and marketing. The difference between achieving 100psi for lockers and 29psi for tires is night and day because of the vast difference in volume of air needed for each task. It takes only moments to raise the pressure in the locker system to 100psi. Peak amperage was not tested in this mode, nor was temperature achieved. Having used a similar pump for years, I believe the results would show that amperage stays fairly low and the pump never really gets hot, as long as it is used to lock lockers.
I also noted in the article that the peak amperage draw was 34 or 35 amps which is something like 60% higher than the published draw. I assume without knowing that the amperage peak occurred while pumping over the rated pressure of 29psi, i.e., just before the tire reached 35psi. If the relationship between peak amperage and pressure produced was tracked, it was not published, but amperage, pressure load, and temperature rise are all related.
All of which is why I still believe the pump is not suitable for airing tires. I would use one of your other pumps for that purpose and leave the ARB pump to locking the axles.
[edit] On the ARB spec sheet for the pump, it does, in small print, say "on time/off time - 30/30". Presumably this is intended to mean 30 minutes not 30 seconds. If so, the run time stated would still be at no more than the rated amp draw and flow for the same specification, 22.9 amps @ 200KPa. The test parameters in the article went well beyond this rated output with the results noted by the author. I don't fault the author for this since 35psi is not an unreasonable target for the forum and his test procedures were uniform. Rather, I find the ARB specifications to be misleading as even our technically inclined author apparently didn't make the connection between exceeding the rated output and the effect on the duty cycle run time. In laboratory testing it took 30 minutes at a constant pressure of 29psi for the pump to achieve a shut-off temperature, whatever that is, whereas in field testing using the pump to inflate 4 tires from zero to 35psi it took around 16 minutes but drove the temperature of the pump to 329 degrees (IIRC). Without the lab data we still do not have a basis for comparison but if the pump got to 329 degrees in a bit over 15 minutes, some part of which was down time to switch tires and a good part of which was at pressures between zero and 29psi, how hot would it be at 30 minutes of any kind of continuous use? I believe the ARB pump is a good tool for a limited purpose, but if a similarly priced, tiny pump can do the same basic job, quietly and with a 100% duty cycle at a fraction of the amp draw and at a far lower temperature, why make excuses for the ARB pump as a tire airing tool?