Young Bentley has Cerebral Palsy and needs help

I’m Bentley’s uncle and his mother, my sister, came up to me asking me for help in making him a specialized bike to help with his muscle development and control of his legs.

He has Cerebral Palsy which is a major challenge for anyone that has it. He is a miracle baby to say the least and a bright child with determination to make the most of his situation.

My goal is to develop a specialized bike for Bentley that will allow him to develop his fine motor control in his legs and feet.
The starting point is a sort of medical bike that costs $1500 but none on the market have everything his mother wants. That’s where my building skills come into play and I need to make some custom parts that attach this bike to an adult bike and allows him to still us his legs to move the bike.

Any financial help to make this special medical bike for little Bentley would be stellar and much appreciated. Thank you!