Single-speed/fixed conversion

[am505]

Hey, sorry for adding this to presumably the mounds of single speed conversion questions from relative noobs like myself. I realise there are resources out there that should cover the majority of this stuff, sheldon brown ect, but for some reason I've had no luck on shedding light on my particular question.
Anywho, I just purchased a 70s Peugeot bike for a singe-speed conversion. http://www.ebay.co.uk/itm/171472263702?_trksid=p2060778.m2750.l2649&ssPageName=STRK:MEBIDX:IT I had been endeavouring to get an 80s peugeot, as I get the impression they are a little bit more straightfoward, english-threaded bottom bracket, for example, however this particular model came up which I've always had a soft spot for so I went for it. As I said I am a relative noob when it comes to a conversion (been riding geared road bike for the last 5 years) so forgive my probable butchering of termnology, but basically another issue I had forgotten you encounter from 70s bikes is (expressing this as best as I can) the crank arm and chainring being seperate, at least not like later bikes in which you can just interchange chain rings- hopefully the photos on the ad will explain it better than me.
So basically my question is how bigger deal is this for a conversion? My assumption is that I won't be able to remove the chainring without removing the crank (which is bit irritating as I live in an area which is relatively hilly so wanted to be able to change quickly depending on the terrain) and therefore what am I better off purchasing, just the appropriate chain rings, something like this http://www.ebay.co.uk/itm/48-TOOTH-...sure_cycling_bikeparts_SR&hash=item566a2cc516, or buying a new more modern crank arm?
cheers, any advice would be appreciated.

 

[Old Plodder]

Neither pics on the referred page shows the chainwheel side of the bike, but I'm guessing that they are 'one piece' cranks.
To obtain a gear ratio suitable for single speed riding, it would be best to replace them with 'bolt on' cranks.
When choosing your gear ratio, you must consider your terrain; it is a waste of time changing it often - find one that suits your riding style and terrain.

 

[jazzkat]

I have no experience of such old bikes but that sprocket certainly is fixed in a different way to what is now the norm. To be honest, I'd leave it as it is and get another bike to fixy lol.
One way to do it though, would be to buy one of velosolos hub conversions spaced as near as you can to your frame mearsurements, http://www.velosolo.co.uk/shophub.html (I've got one on my surly and it is very good).
You would need to build it into a wheel but you could lose the smaller chainring on the crank, keep the large one giving you a chainline of 46mm (measure it to make sure!) and pick a sprocket on the back to suit your needs. They go as big as 22t http://www.velosolo.co.uk/shopdisc.html
I'm a big fan of Velosolo, I'm certainly not linked to the company, other than by the amount I spend

Edit - Doh, ignore all that, you want single speed not fixed! Sorry

 

[Ian H]

That looks like the Stronglight crankset that takes TA Super-touriste rings. Still available, I think, from Spa cycles...yup, here. Find a double-sided fixed hub and put sprockets two teeth different either side.
As some kind of guide I live in Devon (which is hilly) and run 67/63" (only one tooth difference, but I could do two). That's 43/17 or 18.