Re: Building an RSG

Hi All, 
         I am putting the finishing touches, fancy finned electrode holders, 
to my first rotary gap.  It is 2800rpm 12 electrode to run at 5kW.  It has 
been tested at full speed with the electrodes in place and a gap clearance of 
about 0.6mm on each side of the disk , so i have some experience .....My 
comments interspersed

>Greetings all,
Same to you alan

>I am considering building a rotary spark gap.
Good idea

>I've got a sync AC motor out of an old LP turntable.
>I'ld have liked something a bit more powerful but I
>think that it will do.
You will have massive trouble spinning a disk of any size, even without 
electrodes. I don't know how powerful your motor is but my turntable, a Dual 
505 which has a very heavy platter and huge flywheel, says 8VA on the back so 
I'd guess it isn't very much.
Using this motor will also give you problems with endplay on the motor shaft 
if you run the disk straight off it.

>I was going to make  disks from two 1/4" thick paxolin
>boards. I was considering using meccano parts for
>the spindle, using pulley wheels to secure the disks
>to the spindle. I would probably space the boards about
>1/2" apart to give a bit more rigidity.
The meccano pulleys are not made to high enough tollerances. I have one here 
and when placed against a mirror, the flattest thing man can make, you can 
see that the rim is noticeably curved.  I hope you weren't planning to use 
meccano bearings as well !!!!
It is not hard to machine a mandrel to hold the disk and even if you have 
never used a lathe before, which I doubt, you shouldn't find it hard.  I am 
14 and can machine competently enough to build an rsg with no actual tuition.

>I have several quite basic questions.

>1) how much difference will it make to the coil? At present
>I can get 4 foot arcs at 2kW with a static gap.
It depends on yor exact coil setup.  But if you get that gap set up properly 
for your coil then at least another foot is probably on the cards.

>2) Is the project doomed because I only have a press drill
>and basic tools?
To be honest unless you can get a lathe to make the mandrel with or buy a 
mandrel then you won't be able to get the electrode clearance really close 
beacuse the disk will wobble too much.
The disk can be made with hand tools though, as long as you don't mind filing 
the electrodes to balance it.

>3) Can an RSG work with a horizontally spinning disc?
Yes, Greg Leyh used a huge horizontal gap for the Electrum

>have fun,
Trust me, I will

>Alan Sharp.
Nick Field