I started one, a 3phase 15hp 440v motor drove it - well, it worked but never put the formica etc on it - it had a mess of dwyer magnehelics that gave direct readout on fpm and i messed with it a lot. I found taht with a good shop vac and a box for a plenum you got nearly the same info - the magnetude is lower but the data is nearly the same and the shop vac was way quieter.
After all that i realized it was cheaper to buy one.
I kinda need to look into getting one large enough for carburators, i am at that stage where i need to decide to make the next step or not.