Single-speed/fixed conversion

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%3AMEBIDX%3AIT 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-50-122BCD-STRONGLIGHT-TYPE-49-3-32-CHAINRING-BOLTS-/371148506390?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item566a2cc516, or buying a new more modern crank arm?
cheers, any advice would be appreciated.

the ebay link for the peugeot is dead.

So basically my question is how bigger deal is this for a conversion?

It's not. If you must change gears do so by using cogs a tooth or two apart. You're really best off setting it up with a 70" gear and learning to ride that. It'll probably feel quite light to start with.

When I converted a Peugeot I had faced a similar issue with a one-piece chainset. These are your options if you want to avoid buying a new chainset and bb;

a/ Buy or build a track rear wheel and (using a spoke key) run round the non-drive side – dishing the wheel until your chainline is good. You can do this in the frame. Being a 120mm hub in 126mm(?) dropouts you can put axle spacers (LBS oddments box will have these) stepping the hub to the drive side, whilst your (now dished) wheel rim runs centrally in the frame. If you've got cone spanners you can put those spacers behind the locknuts on the hub axle.

b/ Use a 8/9sp 3/32 chain and 3/32 cog. Chainline is less crucial.

–spam–

I actually have a chainset you might be interested in (PM me if you are);

• Driveline 165mm 130bcd thing with bolts
  
• Used 48t TA 3/32 ring, 130bcd
  
• Brand-spanking new 42 stronglight ring, 13obcd
  
  

–spam–

hey, cheers for the reply, sorry im a bit late in replying- i thought i would get email notifications if anyone messaged me, so didnt check the thread, but alas not. iv given it some thought and to be honest i think i would like to replace the chainset, as im new to fixed/single-speeed i want to be able play with around with my ratio and work out what i prefer- i realise I could do this with the rear cog but id prefer a bit more flexibility- the bike wasn't too expensive so I have some money to play around with. however, quickly if i didn't buy a new chainset, are the front cogs like in the second ebay link an option? also can i remove the inner chain ring on the bike? if i do replace the chainset my concern is the bottom bracket- as i realise its going to be french threaded- would i definitely have to replace the bottom bracket- would for example new cranks fit and could i get the chainline right with with other methods, like what you suggested? if i did replace the bb, i wouldnt really know where to start with getting one that fits, considering the threading, would it be very complicated? sorry to bombard you with questions, any light you can shed on any of them would be much appreciated.

Your frame will have a french bb with a spindle length that isn't ideal for single speed(setup for a double on the front), I personally wouldn't change it apart from maybe taking off the smaller ring so it looks more like a single. The range of ratios you can get with swapping the back is huge, I haven't done loads of fixed riding as I like freewheeling but start out with your 49t(???) and a 19-21t on the back as smaller than that could kill your knees... I find this chart gave me a good idea, 46/16 was crazy heavy for me and then 46/19 was a nice world of change.

Also buy the stars, everyone needs the stars...

http://www.ebay.co.uk/itm/361023538285?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

cheers for message, was really helpful, i guess changing the front cog isn't as essential as I thought. do you reckon I will be able to get an adequate chainline without changing the bb, and presumably if I did would all english threaded bb be no good?

The threads are a different pitch so you are stuck with french cups if you have them.

http://sheldonbrown.com/velos.html - about french parts(you can ignore lots of it, totally ignore the maillard bit)

You should be able to get a reasonable chainline with the redishing and stuff. Swap the chainring from the outside to inside can move it a bit more so if you see on this pic the small bolt nearest the bb you can unbolt those to remove the chainrings then undo the bolts holding on the smaller chainring and bolt the larger ring back on the inside(so long as it doesn't foul the chainstays). But that's a last resort ghetto fix and be careful as old bolts don't always like being disturbed and it might not want to go back together.

I would make sure it all rides good geared for a bit and is sound as a bike before chucking money at it.

I am certain you can get a perfect chain line to the outer ring with just dishing. Mine was straightforward although I was building the wheel from scratch. You might have to loosen some spokes if your dishing an existing wheel.

cheers for the comments- thats fairly reassuring. sounds like I have some options to get the chainline on the money. out of curiousity, are there any many modern bb that are designed to fit these sort of threads?

When I looked into it this was all I could find.

http://www.ebay.co.uk/itm/French-Threaded-Bottom-Bracket-various-lengths-/191105554879?pt=UK_sportsleisure_cycling_bikeparts_SR&var=&hash=item2c7ec759bf

OR a threadless bb but they can be a world of hurt in themselves.

http://www.bikeplus.co.uk/p/47132/YST-Threadless-Cartridge-Bottom-Bracket?kw=&fl=1000&ci=54665503241&network=pla&gclid=Cj0KEQjwnZShBRDfxqzr55rcyMEBEiQA1iRNP1N353u3vArkvjlLa8Z6jEDhkoGytUrhKCBFG6LSSVAaAi-U8P8HAQ

Threadless BBs exist for damaged shells. One of those might work (I'm not certain).

...as clockwise says... :)

and those would definitely fit a modern chainset?

also would it possible to potentially just change the axle?

and those would definitely fit a modern chainset?

A more modern type – JIS square taper. Still the most common type of cheap crank.

also would it possible...

Of the OG BB? I'm sure it's possible but I wouldn't even go there.

couple with more questions and then I will really leave you guys in peace from my ignorance! 1) probably nothing but it'something I've never come across, in the picture I've included there appears to be something in the rear dropout, maybe part of the derailleur or it's removal as it has a screw but the way that it appears it seems it would block me from pulling the wheel back into the dropout and achieving chain tension 2) my original intention had be to ride 48/16 but now probably going to keep the front 52 cog and ride 18 at the back. sorry if this is painfully obvious, but despite them being comparable ratios are there are any implications for riding a bigger cog at the front (i know it's only minor), for example maybe for rear wheel skidding? apologies for dragging you lot back into single speed 101 with me...

http://tinypic.com/view.php?pic=1213n1k&s=8#.VCgrxmddVBE

Some sort of adapter claw thing would be my guess. You won't need any of that ss but you will likely want chain tensioners/tugs of some sort so basically take everything off of the dropouts and then fit it like these. The 1st pic might be a good option for using the chain tug partly as a spacer too.

i didn't think I need any of that sort of stuff in terms of chain tension - providing I can get an ok chain line I thought I can just pull the wheel back in the dropouts as they are horizontal?

You don't really. Some people find chaintugs nice to help get the wheel straight in the frame.

oh I see thats good to know. so that thing in the dropouts will come straight out? and in terms of what i said about 52/18 are there any implications from the bigger cogs compared to say 48/16?

You might want to have shorter trousers with the 52.

lol

52/18 is 76" (on 25mm tyres). That's a high gear.