Grama on Yom Tov
I have heard from Rav Weiss on many occasions how the grama gadgets are asur to use on Shabbos, because they violate meleches machsheves, since you clearly want the act to be done.
What is the Rovs opinion when it comes to doing these things on Yom Tov?
(Some sources to consider – Shulchan Aruch 514,3 and MB 25 and Shaar Hatzion 31. Also Shulchan Aruch 507,4 and 511,1 and MB 1)
Also would a Grama on an Issur derabban be allowed if it is lo nicha lei?
(See MB in 320,53 and Minchas Shlomo 1,10)
The problem with grama gadgets is as you mention they may be considered “maleches machsheves” as it is נתקיים מחשבתו, this would mean they are in fact not considered as grama but rather as his מעשה. The leniency of the Mishna Brura and a number of other poskim is with regards to grama itself. While on Shabbos we are stringent even on a real grama some poskim are lenient on Yom Tov. This would only be for something we consider a grama, like putting a candle outside when the wind will come afterwards and put it out. Gadgets that you describe for which we are חושש are not grama would be treated the same on Yom Tov as Shabbos.