Single Speed Conversion

[sean_iow]

Thought some of you might be interested in the conversion of my geared frame to singlespeed. I'm usually a singlespeeder but when I bought the Genesis frame I'd been riding a geared bike for a few months and thought that it would be ok to not have an ebb or sliding dropouts. It didn't take long to realise that I missed the simple life and so converted the bike to singlespeed. At first I thought I was lucky as it seemed to work with a magic ratio using the sprocket, chainring and chain from my other singlespeed. As the chain wore I decided to fit a new one and then discovered that the magic ratio only worked as the chain was part-worn when fitted and a new chain was too tight. I fitted a bb mounted tensioner and this was ok but the wheel only had an outer bearing and once muddy and wet the chain would slide over it rather than spin the wheel. I tried a rear tensioner but the shrouded dropouts limited the range of movement. I also had the my first puncture in years that the tubeless sealant didn't seal and removing the wheel was a pain as I had to unbolt the tensioner. I decided that a proper conversion was required. I considered using an ebb in my threaded shell but these have limited movement and I would no longer be using my preferred Hope BB. I thought about replacing the BB shell myself but then thought this might be a bit risky if it went wrong. I tracked down a frame builder who said they could fit sliding dropouts so I sent the frame off to them but 17 weeks later it returned with a note to say he couldn't get dropouts to match the angles of my stays

I then decided to revert to fitting a new BB shell myself, what's the worst that could go wrong? I bought the shell from Ceeway and a Bushnell EBB from Charlie the Bikemonger and got to work.

I made a jig to hold the frame parallel to the bench by measuring the size of the tubes and then selected/made spacers to suit.



Checking the frame is set correctly on my surface plate. The jig holds the frame such that the BB is 90 degress to the main steel section on the jig.



I then mounted the whole lot on the drill bed and cut out the old BB shell with a holesaw.



Checking the fit of the new BB shell, I had to fettle the cut on the tubes to get this to fit as I wanted. The top plate holds the BB shell in place for welding and the bottom one spaces it up as it's narrower than the threaded shell which was cut out.



I cleaned it all up with a small shot-blasting gun to get it nice and clean for welding.



I did consider welding it up myself as I have a small DC TIG but I've not used it in a few years so I'd have to get some Argon for shielding and get some practice in. I tracked down a friend of a friend who welded it up for me.



After painting the area and new BB shell I fitted the EBB. The new paint isn't the same shade as the original frame so I added some decals on the line where the colour changes to hide it. You can see the change in colour on the inside of the non-driveside chainstay but this is hidden with the wheel fitted.



Bike back together and ready to go



The worst bit of he whole job was cutting the old BB out as the holesaw didn't have enough depth of cut so I had to cut part way through, then cut out the bit of BB, then holesaw some more etc. It was also pretty nerve-racking as once I'd started cutting there was no way back if it all went wrong.

I rode it for the first time this morning, only a flat 7.5 miles to work on a cycle path but seemed to ride ok. It's a proper off road test on the way home of 25 hilly miles in the dark which also has the advantage that I won't be able to see the new paint doesn't match

Sean

[benp1]

Good commitment to SS there sir, good job too

Not sure I'd be brave enough to cut my frame myself...!

[Ben98]

That takes some balls, good work!
Looks really well finished and the decals look like they were there from new.

[Bearbonesnorm]

Superb, good effort

[Charliecres]

Impressed.

[johnnystorm]

Mentalist!

[slarge]

Good effort, not sure if I would go quite that far on a hack frame!

[sean_iow]

Cheers All, I'm really pleased with how it came out.

Good effort, not sure if I would go quite that far on a hack frame!

Oi! That's my pride and joy

The low cost of the original frame as an ebay bargain (it was new but has a paint defect on the seat tube, I put a sticker over that as well ) did help with the decision to try the work myself as it was not too big a loss if it all went wrong.

There were several reasons I decided to modify it in the end, apart from getting a better way to tension the chain:-

I couldn't find a replacement frame with all my required features
The bike is the most comfortable hardtail I've ridden (and the same has been said by my friends who have ridden it)
It handles really well (it's saved me on more than one occasion when I've run out of talent and the bike seems to just somehow stay upright)
I really like the look of the frame
I couldn't really afford to buy another frame
I'm quite emotionally attached to it (it's the bike I rode on my fist solo bivi and on my first off-road century)
Most importantly - I've got custom full and partial frame bags I've made for it and there is more time invested in making these than the conversion took to do

I went the long way home from work last night (22 miles with about 60% off road) and it seemed to still ride just as well as before the work When I got home I did wonder why I put in the effort to hide the transition between the old and the new paint as the trail conditions seem to be up to the task of doing that.

[Fat tyre kicker]

Epic mod there to be fair

[fatbikephil]

Nice one, got to love steel frames!

[Trail-rat]

Good work that !

[Zippy]

Top tinkering Sean. Looks very well executed.

What sorry of shot blaster did you use, and what medium were you blasting with? That's next on my list of things to get (thinking alloy refurbs)!

[sean_iow]

My blasting gun is this one by SIP

https://www.sipuk.co.uk/sip-02150-maxi- ... 1-cfm.html

You need a fairly big compressor to keep up with it but it's ok for small areas. I used normal blasting media as it's a steel frame. I bought it in Machine Mart about 10 years ago so you can tell it doesn't get much use but on the frame it was the only way to get it cleaned up. If I did another one I'd clean the area with the wire cup brush on the grinder before cutting out the BB as then I could turn it over as it wouldn't be fixed to a length of steel box section

You'd might need softer media for alloy? but I'm no expert. I have the gun as I've used it on bits of land rover over the years. It does also make a mess and the media goes everywhere! I did the frame outside but if I was doing a larger item I'd work inside and bicycle up a tarp (not the nylon sort we sleep under) in a bath tub type shape so I could collect the media, sieve it and re-use.

If you've got a big area to do you'd probably be better off with something like this

https://www.sipuk.co.uk/sip-02157-sandb ... 1-cfm.html

But I've got no experience of using one so couldn't comment on how well they work. When I need something really big doing like a land rover chassis I just pay for it to be done at the local blasters who then prime it as well straight afterwards.

[Zippy]

Nice one - I like that sandblaster hopper kit. Shame it takes up a lot of space and that's something that is at a premium. Still 11cfm is fine, my 50Litre compressor does 12.9 according to the specs, so should be alreet. Won't be doing this till summer anyways

The neighbours must love people like us

[GregMay]

Good work sir, that I liked.

[Bearbonesnorm]

You'd might need softer media for alloy?

I used to use coconut husk for cylinder heads.