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Registered Member #61847
Joined: Sat Oct 21 2017, 07:51AM
Location: Riana, TAS Australia
Posts: 2
Hi all Noob to this forum, so 1st post is a question to the VdeG aficionados out there: I cannot, ever,ever, get an externally excited machine to work. I have built maybe a dozen self excited machines with various belt & pulley combinations, with varying degrees of success, but I have never been able to produce a functional external one. I have tried with grounded lower pulley, grounded bar with charged comb, grounded comb with charged bar, silicone belts, polythene belts, latex belts, charging units have included flybacks, NSTs, OBITs, even ignition coils with oscillators and a rectifier stick - nothing! I have experimented with upper comb positioning, to no avail. My question is, what is the secret?? any advice? Waiting hopefully for some insight. (I'm not too bad with Tesla coils & CW multipliers, btw)
Registered Member #230
Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284
so our VDG @ work 3MeV has a two foot wide belt and the belt goes round @40mph charging supply is 20kV at 0.5mA metal combs top and bottom to put charge on belt and to take it off. Belt width gives current and belt must move fast enough to take the charge to the terminal before it leaks away
Registered Member #61847
Joined: Sat Oct 21 2017, 07:51AM
Location: Riana, TAS Australia
Posts: 2
johnf wrote ...
so our VDG @ work 3MeV has a two foot wide belt and the belt goes round @40mph charging supply is 20kV at 0.5mA metal combs top and bottom to put charge on belt and to take it off. Belt width gives current and belt must move fast enough to take the charge to the terminal before it leaks away
Cool! - thanks for that. That is a big unit. Can you please help with a couple of specifics? What is the belt material, is the lower pulley grounded, and where is the lower comb positioned, ie level with the centre of the lower pulley or above? Thanks for any info.
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Externally excited Van de Graaffs
