How might HR build closer relationships with managers?

Provide training for them, anything from half-hour sessions once a month to one or two weeks away at a management school.

Assist them in selecting staff. By really getting to know what skills they need their people to have, and by improving screening techniques for applicants.

Assist them in organizing, by providing project management software or other software, and training how to use it

Look at their career propsects and re-organize the company so that people's prospects fro promotion improve.

Support them in disputes.

Thank them in speeches

HR is a support function and as a support function, HR needs to find out what the managers need to help them do their job. Obviously the biggest thing is to get qualified and enthusiastic employees. Working on job descriptions and hiring practices and productivity tools help increase the department output. Working on employee morale and team building improves the employees efficiency. Often HR is in charge of safety. Programs to improve safety will be a tool to open communications. Newsletters also help communications. I started a forklift rodeo to train employees and increased morale.

Well since HR departments are the equivalent of a Nazi goon squads, it might be difficult.

Most middle managers are spooked by HR departments and so are the employees of a given corporation.

I would recommend being friendly, available, and return all correspondence within a short period...

Good luck, but you might as well resolve to being the bad

guy in most situations and never being liked by anyone

May I recommend a book? It won't be a quick answer to your question but, nothing worth learning is easy.

Max Dupree---> Leadership Jazz

This is an easily digestible piece of literature and all your questions will be answered and your company will be thankful of the knowledge you gain that will enable you to create long-lasting internal relations.

Good Luck!