I was always thinking that all the TFs used by Hasbro were always designed by (only in G1 some were from Bandai and other companies) Takara, but recenty I have some doubts on this.

 

So can anyone tell, which series was designed by Hasbro and which by Takara?

I think it is some mix of both.

 

Aaron Archer's demonstrations showed how things have been lately rather well. They submitted sketches and such to the Takara team and noted some examples where the Takara team would send back suggested changes.

 

I think that for characters who were to appear in the show, it was important for both companies to be involved in some capacity. Yet we know that MP Starscream was created in Japan. And I would bet that the US Kicker figure is american considering the MM japanese one.

 

So I think it is actually safe to say that design hasn't been one-sided and that it is a positive collaborative effort.

 

I also recall hearing that initial mock-ups of Hot Rod were way too large. So I would bet that large parts of the season 3 and beyond G1 line were also collaborative.

All the early figures based on Diaclone and Microman moulds were obviously designed solely by Takara. Some early figures based on non-Takara toys were designed by their respective manufacturers (e.g.: Bandai, Takatoku, Toybox etc). The 1986 line saw the first series of Transfomers that were created as a collaborative effort between Hasbro and Takara. Essentially the process involved Hasbro telling Takara want they want to see in certain figures, Takara would then create concept designs based on Hasbro's request, and Hasbro would then give feedback for Takara to go off and tweek further until they get final approval from Hasbro. It's much like how George Lucas works with designers like Doug Chiang and his team - George will tell Chiang what he wants for a certain character, vehicle, weapon etc., Chiang and his team go off and work on a series of conceptual designs. George comes along and approves the designs that he wants and from then on the design is refined until it reaches what Lucas wants. The process between Hasbro and Takara is like that, only on a smaller scale. Examples of the earliest figures created collaboratively would have been toys like Hot Rod, Kup, Blurr, Wreck Gar and Rodimus Prime.

 

For more information about how this whole thing works, refer to the interview with Ono Koujin in the "Transformers: Generations" book (there's an English translation of this interview on Planet Sabretron.