Quitting a collaboration project without hurting collaborators I am a PhD student collaborating with another PhD student A, under supervision of Prof. B &amp; Prof. C. I am student of Prof. B. Student A is co-advised by Prof. B and Prof. C. 

Prof. B chairs the project. I was asked to join this side-project because of my certain experience.

Our work requires knowledge from both A and me. A is doing well in his part. However, the novelty in my part, is problematic (in my view) and hard to produce. To this, not everyone is convinced: Student A thinks I need more tunings; Prof. B is dubious yet believes the novelty; Prof. C agrees with me but with a little suspicion.

I have now enough lab evidence to support my claims (i.e. the failure novelty). And I believe I will convince others at next meeting.

I would like to quit this project, and do not want to waste more time. Student A can still publish his part, just not a "big" paper though. And I will not ask for any credits of course.

The question

How can I, with enough respects, yet properly quit the project without hurting feelings of other colleagues? Especially student A and Prof. B?
Just graciously explain yourself and be firm. They may not be happy but if you just won't go forward, they have to deal with it.  

You can't always make everyone told happy.  Sometimes you just need to cut things off.  

Don't belabor or debate.  Just be respectful, but firm.  And brief.

https://www.youtube.com/watch?v=ABXtWqmArUU