There are 742 family trees on Ancestry.com listing Tobias Hartranft. If you are a member of Ancestry you could send a message through Ancestry to each person who developed one of the trees giving them a way to directly contact you rather than through Ancestry. There is a Hartranft Family Reunion page on facebook and if you are already not part of that group it would be a way to contact a few people Hartranft Family Reunion | Facebook.
Dear Mr. Hartranft,
Thank you for posting your request on History Hub!
We suggest that you review NARA’s Resources for Genealogists, as well as the History Hub Blog titled Suggestions and Advice for Family History Researchers. We also suggest that you contact the Pennsylvania State Archives for any information and/or resources about the Hartranfts in Pennsylvania. In addition, the FamilySearch Research wiki for Pennsylvania Genealogy and Mennonite Church in the United States may be useful.
We hope this is helpful. Best of luck with your family research!