TMP Diagnosis

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Aaron J Hardin
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Joined: Wed Jun 19, 2019 4:26 pm
Real name: Aaron J. Hardin

Re: TMP Diagnosis

Post by Aaron J Hardin » Tue Jun 25, 2019 6:39 am

Considering that these pumps run between $400-$900 in good condition I would lean towards a faulty pump. The condition described is a shorted winding. Check that the wiring is correct as this will have similar symptoms as will water/condensation on your stator.

A bad hallefect sensor is a possibility, however this would not blow fuses (unless faulty wiring). It would likely overheat or indicate a fault.

The oil is not an issue, it is non conductive and will create minor drag. Once you repair the windings (or evaporate any water) run the pump on low rpm and purge with dry nitrogen. There is a sight glass at the bottom cap of these pumps, the oil should settle at the halfway point.

I know this is an older post but Molecular Turbopumps are vastly superior in many ways and worth the effort to get running correctly. Yes they are overkill for many hobbyists but to name a few benefits:
-They are especially useful in a fusor where the objective is to collide hydrogen^2 (explosive) into helium (also explosive)
-You can control the vacuum speed 100:1 in many applications
-They can operate for extended periods of time uninterrupted
and finally, the cleanliness

John Futter
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Joined: Thu Apr 22, 2004 2:29 am
Real name: John Futter

Re: TMP Diagnosis

Post by John Futter » Tue Jun 25, 2019 7:31 am

a lot of RAP spelt with a "C"
Helium is one of the noble gasses
Most turbos are on the second hand market because their bearings are past end of life.
In 40 failures in our lab of turbos all except one was bearing failure.
the odd one out was vane failure (read spectacular) a mass of scrap aluminium

Any water vapor would mean that you do not have sufficient vacuum for backing and the pump should not be started.

For fusor work for inexperienced vacuum practitioners I would recommend Diff pumps - less of a mess when making mistakes this applies to the $$$ spent as well

as an aside turbos do not like running at typical fusor vacuums ie on th edge of molecular flow where blade tip damge is foremost

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