"It will be a lot more comfortable and a lot more forgiving on my body when I'm planning to do 150km a day," he said.

The 54-year-old public servant on Saturday begins the drive to Perth. He'll be doing the return 4000km trip on his recumbent bike, with his 77-year-old father Garry as support crew. They will leave Perth on August 3 and plan to take 25 days to get to Moruya, starting from one ocean and finishing at another.

Shane will be riding a heavy-duty Greenspeed Magnum XL recumbent trike and is not worried too much about crossing the roadtrain-heavy Nullarbor.

"I'm really not," he said. "They're professional drivers and I have a UHF radio to let them know I'm there and hopefully they will let all their mates know as well."

Shane was an infantry officer for 21 years and when he retired from the army,  felt he had "earned a break".

"In December 2016 I decided my break was over, so I bought a recumbent trike and set myself the goal of riding 4000km across Australia from Fremantle to Moruya," he said.

"I’ve been preparing and training for the past year. Since then, I’ve lost over 40kg - equivalent to two bags of cement - and I’m now averaging over 300km per week.

"I ride the 50km round-trip commute to work each day and do training rides on the weekend. Having a goal gets me on my trike each day, even on the cold, wet Canberra mornings when I would rather stay in bed a little longer and drive to work."

Shane will be raising money for Legacy and the Salvation Army. You can follow Shane's Long Ride Home on Facebook or donate at this link.

"It’s not a race and I’m not setting out to break any records. A man my age and size crossing the country on a pushbike is challenging enough for me. Doing my own thing at my own pace and enjoying a few weeks of splendid isolation and personal solitude has its own appeal," he said.