Singlespeed & Fixed Gear - How do you convert a 7 speed?

Hi guys! I need to convert my Diamondback Sorrento 04 into a singlespeed. It has a 7 speed shimano Maga range cassette gear thing. And Acera shifter (that dosn't matter though). I have been reading up on and asking for help on converting it but all I can find is conversion kits for 8 and 9 speed cassettes(gear gizmo). And what do I do with the 3 gears on the crank?

So... How do I convert a 7 speed gear thingy?
What do I do with the cranks?
How much will this be?

Thank you, Leo

*edit*
Its a 21 speed, not a seven, 7 in back, 3 on the crank.

If you wanna be ghetto (like me an my first SS) you can find a gearing you like which has as somewhat close to straight chainline and just rip off the derailers. Then cut the chain to the right length for your favorite gear ratio and there ya go. SS in 5 minutes with almost 0 cost.

If you wanna spend money with a new cassette just take it to your local bike store. I don't want to sound like an ass but if you're calling a groupo a cassette gear thing you might not want to mess with chainlines and hub spacings.

I have done that take off the derailer and chop the chain to lenght with my old cheap bike, I wanna go a little more porfesional with this one.

As for my english and bike language, no hard feelings. I am very good with my hands and injoy working on bikes, but just dont have the know how yet. I will be able to put it on just cant find parts to do it.

if you have vertical drop outs you might want to invest in a surly singulator to keep your chain tension nice.. you can also take off the casette and replace it with spacers and a single casette cog like this to get your desired chainline.

http://farm1.static.flickr.com/123/320695928_c5c2e0c4be.jpg

As for the crank, Put whatever ring you want to use in the position you want to use it (probably the outside for aesthetic reasons.) and get rid of the other 2 rings. You'll need to either get some single-spaced chainring bolts, or you can use the longer bolts to attach a bash-guard. Then just use the spacers in the back to get a good chainline.

Thanks for the help!

Im going to replace the cassette and put this Gusset 1-ER Single Speed Conversion Kit, DMR STS Tension Seeker Single Speed Tensioner, and Truvativ Stylo Single Speed GXP Crankset '05. All this is at Price Point.

I can put it all on, but will this work?

I have done that take off the derailer and chop the chain to lenght with my old cheap bike, I wanna go a little more porfesional with this one.

If you want to go a little more professional, haha, get a new rear wheel (or check this (http://shop.greatdealsonbikes.com/merchant.mv?Screen=PROD&Store_Code=GDOB&Product_Code=TR01&Category_Code=TR) out) and a new crankset (i like this (http://store.somafab.com/paketrackcrank.html) crank for the price).

The cheap way people have mentioned before is to just find a gear ratio you like and cut the chain short. That works, too. How much do you want to spend?

7 speed freewheel or 7 speed cassette? Since it's an '04 I'm guessing freewheel, but either way you need to spend some time at http://sheldonbrown.com/k7.html and learn about how each one works. Elsewhere on that site you can read about redishing, which is what you will probably have to do if it's a freewheel.

If you want to go a little more professional, haha, get a new rear wheel (or check this (http://shop.greatdealsonbikes.com/merchant.mv?Screen=PROD&Store_Code=GDOB&Product_Code=TR01&Category_Code=TR) out) and a new crankset (i like this (http://store.somafab.com/paketrackcrank.html) crank for the price).

The cheap way people have mentioned before is to just find a gear ratio you like and cut the chain short. That works, too. How much do you want to spend?
That wheel looks pretty sweat, I never thought to replace the wheel. I have $200 for this build sence my other whent bad.

7 speed freewheel or 7 speed cassette? Since it's an '04 I'm guessing freewheel, but either way you need to spend some time at http://sheldonbrown.com/k7.html and learn about how each one works. Elsewhere on that site you can read about redishing, which is what you will probably have to do if it's a freewheel.
Wow, that is alot of confusing stuff. I will read up on in to get a better know-how of what I am doing.

Thank you all!

This is a 7 speed cassette conversion with vertical dropouts and no chain tensioner. You need spacers for the freehub, a shorter BB spindle and short chainring bolts. You need a little bit of brains and a lot of luck to figure out the magic gear so you don't need a chain tensioner.
http://thumb9.webshots.net/t/42/43/5/9/89/2236509890068014369jHohCP_th.jpg (http://sports.webshots.com/photo/2236509890068014369jHohCP)

nashbar single speed cassett conversion kit 29.99

This is a 7 speed cassette conversion with vertical dropouts and no chain tensioner. You need spacers for the freehub, a shorter BB spindle and short chainring bolts. You need a little bit of brains and a lot of luck to figure out the magic gear so you don't need a chain tensioner.
http://thumb9.webshots.net/t/42/43/5/9/89/2236509890068014369jHohCP_th.jpg (http://sports.webshots.com/photo/2236509890068014369jHohCP)


half links

nashbar single speed cassett conversion kit 29.99
That looks to be what I need, thank you! It dosen't look to be that hard to put on.
:D

not at all and it work pretty well the only thing I have done to those is change the pulley out for a steel on rather than plastic

Thanks for all your help!