My wife and I get off a bike and barge trip in July in Bad Wimpfen and want to go to Rothenburg from there. The train takes 3 plus hours since there is no direct route and to rent a car to drive the 70 plus miles seems like a hassle. I want to see if there is a local bus that goes from the two towns but can not find a local schedule. Any idea how I might access that or other suggestions?
Bad Wimpfen and Rothenburg are both out of way locations in different Länder (states) , hence the multiple connections. The buses can usually be found on the same Dbahn website where you looked up the train connections. Local buses normally seem to be limited to short run trips within state borders. Perhaps someone else will know an exception. You may have to make a tough choice between train and car.
I am a big fan of Rothenburg but unless if fit very well into the remainder of the trip, I would skip it in this instance. There are other places to see similar sights nearer Bad Wimpfen.
I will add that if you go to Rothenburg, it is rich in sights beyond the town square and the shopping area. Here are a few of my amateur paintings based on the area: both the town and the Tauber Valley.
...and Rothenburg may feel like an unnecessary detour after visiting Bad Wimpfen, which is a gorgeous little town overlooking s scenic bend of the Neckar river. Unless you really want to visit Rothenburg's unique overabundance of trinket shops.
Local buses normally seem to be limited to short run trips within state borders. Perhaps someone else will know an exception.
Rothenburg is in the middle of nowhere. There would be no demand for a bus service running from the Heilbronn area across the Württemberg/Bavaria border into western Franconia.
For various reasons, buses in Germany are an extension of rail transportation, not competition. It's not like the US, where Greyhound runs as parallel competition with Amtrak. German buses generally provide transportation from towns served by rail connections to neighboring towns without it. As such buses tend to be run by local transportation districts (Verkehrsverbünde) for short distance travel within the district.
As a fan of picturesque small towns, I know well the frustration of trying to move between two such places in different regions. The local transportation just isn't set up to make that easy. When I look back on my trips, the most common mistake I've made is spending too much time trying to get to a difficult-to-reach, cute small town when there were similar, more accessible places I could have chosen.
Well you asked for other suggestions so I'll offer one. Instead of going to Rothenburg why not continue along the Neckar to the wonderful university town of Tubingen? From there if you aren't tired of bikes and water you could make your way to Lake Constance (Bodensee) where lots of Europeans go to bike along the lake shore (300 km I think) and take the ferries across the lake? There are several beautiful towns with medieval and baroque cores that line the eastern shore. It's easy to rent bikes and there is a great bike culture everywhere.
We spent 3 weeks exploring this area from Überlingen last summer and it was wonderful!