How to pair a 7spd freehub with the rest of the drivetrain?

[Rick L]

So I've found my 7speed freehub that I'm going to use. It is a 14-28 tooth unit (don't know what this means).

I understand that the derailer needs to be able to handle the largest gear on the freehub (?). Do I have to get a 7speed unit? I know that I need a mid to shortcage model due to ground clearance issue.

On to the front derailer, I'd like three gears to make a 21 speed trike. How does one figure out if the crankset is compatible with the freehub? Or does this matter? The trike is going to be used mainly on the flat but could see some hill time.

BTW: I'm a big fan of Sheldon Brown and am sorry to hear that he passed away. I've read over his amazing site but I'm very new to bike building and rather confused.

Thanks

Rick L

[TheKid]

Do you have a freehub? Or a freewheel? There's a difference, but it won't matter as far as the questions you ask. You probably have a freewheel.
14-28 refers to the number of teeth on the cogs. (Rear sprockets) The largest cog has 28 teeth, the smallest has 14 teeth. Most front and rear deraillers in the lower price ranges (Under 30 bucks) are compatible with common cranksets and your freewheel. Common cranksets have small chainrings (Front sprockets) from 24-28 teeth, but some have smaller rings with 22 teeth, middle rings with 32-38 teeth, and large rings with 42-48 teeth. They'll be described with 3 numbers, such as 22-32-42.
I used the same rear derailler on different bikes for 6 speed and 7 speed freewheels, and an 8 speed cassette. Sheldon Brown has a wonderful tutorial on making the adjustments. (I say has, because as long as his articles and tutorials are available, he's not really gone.)

[Rick L]

Thanks for the info. I'll head to the local bike store and see what they've got

Rick L