As you research similar products, find out how each one performed in the market, as well as the strong and weak points of their designs. Christini relied on his own evaluation of previous patents, talked to older bike riders (since he was too young to remember the previous products himself) and got additional information from writers and editors of bike magazines. Here are some other ways you can check out previous products:
1. Simply call the inventor or company and ask how well their product did. If the product is off the market, they'll typically tell you everything you want to know.
2. Talk to retailers; they often remember products that are no longer on the market.
3. Talk to manufacturers' reps or salespeople in the industry who are knowledgeable about past products.
Like Christini, don't be afraid to contact writers and editors of industry trade magazines or newspapers. If they can't help you themselves, they can often refer you to good sources of industry information.
In his research, Christini discovered that early all-wheel-drive mountain bikes had external, flexible cable drive shafts that bicyclists considered ugly and cumbersome. Another drawback: The flexible cable drive system needed to be twisted a certain amount before it could transfer energy, which caused a delay before the all-wheel-drive feature kicked in. Previous products also had too many plastic parts, which weren't durable enough.
Christini did uncover one positive feature of previous products: They had the front-wheel drive set at a less than 1:1 ratio to the rear-wheel drive, so that during normal riding, only the rear-wheel drive is engaged. Bicyclists loved this feature because it gave the bike greater traction and allowed for an efficient transfer of power without compromising steering ability. The front-wheel drive didn't engage unless the back wheel started to slip.