How to share responsibility for part of my advisor's project, which I did not create and I am insecure about? I am a first semester PhD student, working in the planning of an experiment that is on a funded project from my advisor. I am not paid by this project, the professor has not spent grant money on me. I did not participate in the writing of the project proposal, but I read it before applying. I wrote my research plan aligned, in general terms, with the project's topic, which interests me. The project, as planned, was supposed to be carried out by a team. The experiment was supposed to be ongoing when I arrived.

I have seen myself in the position of becoming the main responsible for this experiment in the past few weeks. I have many operational tasks, like buying material to build it, making drawings and specs, actually doing some of the manual work of building things, etc. This is taking anywhere between a third and two-thirds of my time, for a given week. I have expressed to an experienced co-worker who is kind of a lieutenant to my advisor that I feel like I am not making progress as fast as I should. 

I see some positive sides to this situation:


This can be a sign of trust in me.
Being new here, I want to help the group and establish good relations. 
My advisor is an important researcher in his field, I trust his judgement on finding interesting research topics, and I feel the experiment may actually lead to something good. 


However, I have some concerns:


The experiment was very vaguely specified in the proposal. I thought they would have advanced when I arrived, and I would only help and learn, but I'm having to compensate this. 
This is costing more money than they had anticipated. I found out that equipment that was supposed to be available is not. As the cost goes up, this thing becomes "too big to fail" and the immobilized capital makes it harder to just stop it.
I feel like it may be using me as free labor just to get something the research group needs done.
I currently don't have enough time to actually improve my research plan or even study properly, with all this "operational" work. 
I have a hunch that the experiment's goal could be achieved with a much cheaper, quicker "numerical experiment" or "model blind test", but this idea came a little late in the process and I don't have time to formulate it better.
I don't want to say it like the plan was a half-baked idea.
Most importantly, I don´t want to become a slave to this experiment, being the main or sole responsible for treating the results, dealing with the possible shortcomings of it´s conceptualization, etc.


What strategies and etiquette would you recommend to share responsibility and keep the option of "going rogue" or pursuing something else and becoming detached from this experiment later on?

I have thought of the following:


Asking for more time and make this experiment more "mine", by developing some sketches and ideas that I have for it.
Asking if we can involve a Master's student to help me.
One question additional question I've got, you state you're not funded under the funded proposal. Does that mean you came to your advisors group with your own funding or are you being paid by the department to TA or something related?

I ask this because the above two funding situations for a PhD student means the advisor is free to spend what would otherwise have been your salary on materials, equipment, or other personnel. But your efforts can still be attributed to the project. So unless your source of funding is conditional on publishing, I wouldn't worry about how the various things you're working on are funded.

That said, if you find your current efforts interesting and exciting, stick with it and try to align your research plan with it. As a first year PhD student, you have the time to spend developing an apparatus(you've got 3 or so years extra over postdocs or masters students). And if you do get the apparatus setup and working, that sets you up as the person in charge of the equipment, paving the way for collaborations.

Though I would advise you to do your best and layout a timeline for your advisor, and make him aware of your timeline. If he wants faster results you can always suggest the intermediate steps such as your hunch(nothing beats experimental results), or ask for assistance from the more senior members in your group.