Broken Brompton hinge

[lkingscott]

I hate the splined bearings. There is so little depth for the tool to mate and the socket tools have such an offset, that there is a high chance if it slipping, if the bearing cups are siezed.

I'm a big fan of Pedro's socket holder. Mine's the simpler, older version, but it works well.

A bolt through the socket would have been simplest, but you know how it is in the heat of the moment... I was using a 1/2 inch ratchet in the socket, so putting something through the socket would have prevented using the ratchet. Once I started with the G clamp and spanner, I realised a bolt through the socket would be the next option if the G clamp failed.

I was surprised the G clamp worked so well. They have a habit of slipping off things like this as the cheap chinesium screw threads tend to be relatively poor tolerance and the screw wobbles about.

[lkingscott]

Yesterday, after getting the BB off, I added a warning comment in caps to the Video on YouTube showing the wrong BB tighten and untighten directions on a Brompton.

Today the video is down 

Other than the wrong thread directions, the video was good. I hope he fixes that part and puts it back up.

It is entirely possible to re-thread the BB tube backwards using a thread cutting tool the wrong way round and then fitting the BB cartridge the wrong way round.

[rogerzilla]

I recall a case either here or on another forum where a bike shop had done exactly that on a brand new frame.

One contributory factor is that the R and L markings on Cyclus and maybe other BB taps do NOT refer to which side of the bike they go in.

[Tim Hall]

I hate the splined bearings. There is so little depth for the tool to mate and the socket tools have such an offset, that there is a high chance if it slipping, if the bearing cups are siezed.

I'm a big fan of Pedro's socket holder. Mine's the simpler, older version, but it works well.

A bolt through the socket would have been simplest, but you know how it is in the heat of the moment... I was using a 1/2 inch ratchet in the socket, so putting something through the socket would have prevented using the ratchet. Once I started with the G clamp and spanner, I realised a bolt through the socket would be the next option if the G clamp failed.

I was surprised the G clamp worked so well. They have a habit of slipping off things like this as the cheap chinesium screw threads tend to be relatively poor tolerance and the screw wobbles about.

I have a separate bottom bracket tool which fits a 32mm socket.  Crank bolt (nice small head) , with washers, through the tool, socket over the tool. Handy length of scaffold tube over the end of the tommy bar. Remember to loosen the bolt as the bottom bracket unscrews. 

[lkingscott]

I recall a case either here or on another forum where a bike shop had done exactly that on a brand new frame.

One contributory factor is that the R and L markings on Cyclus and maybe other BB taps do NOT refer to which side of the bike they go in.

 :'( 

[lkingscott]

I hate the splined bearings. There is so little depth for the tool to mate and the socket tools have such an offset, that there is a high chance if it slipping, if the bearing cups are siezed.

I'm a big fan of Pedro's socket holder. Mine's the simpler, older version, but it works well.

A bolt through the socket would have been simplest, but you know how it is in the heat of the moment... I was using a 1/2 inch ratchet in the socket, so putting something through the socket would have prevented using the ratchet. Once I started with the G clamp and spanner, I realised a bolt through the socket would be the next option if the G clamp failed.

I was surprised the G clamp worked so well. They have a habit of slipping off things like this as the cheap chinesium screw threads tend to be relatively poor tolerance and the screw wobbles about.

I have a separate bottom bracket tool which fits a 32mm socket.  Crank bolt (nice small head) , with washers, through the tool, socket over the tool. Handy length of scaffold tube over the end of the tommy bar. Remember to loosen the bolt as the bottom bracket unscrews.

I only started working with the splined BBs last year, when I had to replace the BB on my touring/city bike. The main bike I use and therefore work on is a home built trike, built out of 3 old 24" kids bikes, which originally had all the old kids bike fittings, i.e. loose bearings everywhere. It's done over 25k km (25 megametres!) and I've gradually replaced the old rubbish, including welding on brackets to turn it to disk brakes. The final step, which will be done soon is to replace all the drivegear, moving to external BB bearings and Hollowtech crank and over 600% gear ratios (49 gears...!!!) but that's for another thread. 

I think I will be looking to do something like you suggest with my tool. Something like a CSK allen or torx head bolt would fit in the 1/2 inch (12.5mm) socket and still allow it to be used with standard socket tools.

However, the external flats are closer to where the force needs to be applied, reducing the bending moment arm, so I'll probably just use a standard bolt or threaded rod and nut with plate over the end of the tool.

[lkingscott]

BTW, it's going to be fun removing one side of the BB on the trike. I've tried before whenever I've replaced the loose balls and readjusted, but when I made it, I found that bearing cup would regularly come loose, so I locked it in place with red Loctite. This is permanent but can be undone if heated to 350C!!!

I think I'll need to repaint after...!!!

[Tim Hall]

BTW, it's going to be fun removing one side of the BB on the trike. I've tried before whenever I've replaced the loose balls and readjusted, but when I made it, I found that bearing cup would regularly come loose, so I locked it in place with red Loctite. This is permanent but can be undone if heated to 350C!!!

I think I'll need to repaint after...!!!

Loctite aside, there's a nifty trick (apologies if you know this already) for cup and cone bottom brackets, assuming you can get one side off, involving a hefty nut and bolt through the fixed cup.  Linky https://www.sheldonbrown.com/tooltips/bbcups.html.  Scroll  down to fixed cup tools. Substitute M16 for 5/8".

[lkingscott]

BTW, it's going to be fun removing one side of the BB on the trike. I've tried before whenever I've replaced the loose balls and readjusted, but when I made it, I found that bearing cup would regularly come loose, so I locked it in place with red Loctite. This is permanent but can be undone if heated to 350C!!!

I think I'll need to repaint after...!!!

Loctite aside, there's a nifty trick (apologies if you know this already) for cup and cone bottom brackets, assuming you can get one side off, involving a hefty nut and bolt through the fixed cup.  Linky https://www.sheldonbrown.com/tooltips/bbcups.html.  Scroll  down to fixed cup tools. Substitute M16 for 5/8".

I might try that, thanks.

It is the non drive side and it has flats, making it more difficult than the type which uses a C spanner, although the article states that side should be the adjustable side. It is strange it came undone, implying the threads are reversed. It is possible I welded the bracket on backwards, but I'm pretty sure I just cut a V close to the steering tube to reweld it at a different angle to the steering tube.

Anyway, I'll find out which way the threads are when I remove the drive side, which is removable and adjustable.

If the worst comes to the worst, I can weld a lump of metal onto the shell as it's going to be junked. Just the heat from the TIG would exceed the Loctite melt temperature.

All this for another thread though! I have everything ready, but I need a warm enough day to work on it outside. However when the weather is good I end up going for a ride!

[lkingscott]

Back on the subject of weirdness... the drivetrain!!!

I've been looking at whether to play with this. It would certainly be nice to make more standard.

However I've decided not to as it would be like pulling a thread on a jumper...!!!

The current design, with small hub gearbox and 2 speed derailleur is prehistoric. A rough estimate of the space between the frame mounts is 105mm. On the non drive side there are 10mm spacers. On the drive side I estimate about 25mm for the derailleur gears. Outboard of the frame on the drive side is about another 25mm of hollow nut with the hub gearbox shift chain going through. I checked the size of some of the latest derailleurs and a 12 speed 520% 10 to 52 tooth cassette is 37 to 40mm. So as far as space is concerned, it would be possible to rebuild it with a 12 speed 520% cassette, but the frame dropouts would need to be spread.

SRAM XD 12 speed compatible hubs are 145 to 148mm wide, which is a big increase from 105mm. I have used much wider and narrower hubs on dropouts before, simply bending the dropouts inwards or outwards to fit, with no issues. However 40mm would be almost 40% wider than the current width.

Other issues could be the derailleur shifter getting close to the ground, the chain alignment and what the chain tensioner does when folded, not to mention all the conflicts of bits and pieces when folded.

There are narrower hubs, 130mm and 135mm will take up to 11 speed cassettes. It is possible to build custom cassettes and chainwheels are available from 9 to over 52 teeth. 9 and 10 teeth might not fit standard cassette hubs as all the ones I have seen are for the SRAM XD whic is slightly different.

IMO, 9 speed, 9 to 52 teeth, 578% bottom top ratio difference, without hub gearbox would suit almost all riding conditions and need only a single gear shifter.

Anyway, I think I'll just clean everything up and refit, unless it is obviously knackered, to use the technical term!

[lkingscott]

I prepared the first 2 parts for powder coating yesterday, except for degreasing, and worked out how to hang in the oven, which needed some brackets on the box for a tube to hang things from.

I built the heater stand and tested the heaters. One of them has a broken thermostat control. The knob has obviously been bashed in transit, breaking the plastic. As the heaters are cheap product returns, I'm fixing the heater!

I'm making an aluminium plate to replace the broken plastic...!

Many might question the lack of covers on the heater side of the box. It would be more efficient with a cover and I may make something some time. However the heaters are infrared patio heaters and without the cover I can see what's happening. So for now I'll see how it goes without the extra covers.

With just one 2kW heater running, the heat is amazing. As expected, the aluminium doesn't get hot very quickly, hardly even warm in fact. I know it will heat up during a half hour cure, but there's nothing to burn on it. I might need to cover the timber stand with some tin foil as that perceptibly warms up where it is exposed to the reflected infrared. A metal stand would have been better, but timber was quicker to knock up.

[lkingscott]

Wehey, the oven works brilliantly. Not powder coated yet, but after cleaning, I wanted to heat the parts anyway to ensure they have no contaminants which could affect the powder coat. I was able to test that parts can get to the right temperature range and no problem.

I checked with the steering tube frame part and after less than 5 minutes in front of the heater, in the box, it's over 200C.

The aluminium box does get too warm to touch after 10 minutes or more, but it's certainly not as hot as the parts for coating.

[lkingscott]

First coating attempt with the tribo gun was not a 100% success, but it's a promising start.

The tribo gun worked brilliantly and the oven too, taking only 5 to 10 minutes to fuse the powder and then I kept it in another 10 minutes to ensure it had cured, but there were 2 problems with the finish. It is a bit orange peely and there still appears to be a bit of contamination causing some imperfections. I was really surprised at the contamination as I'd taken so much care to clean it then heat it to ensure nothing strange was going on with the underlying coating.

Hopefully I can flat it out and next time I'll put a load more powder on and it will come out smoother.

I also have some clear powder coat lacquer, which I can coat it with and then polish up.

[lkingscott]

Next attempt, lots more powder and much better.

There's a couple of tiny defects and I could probably have used even more powder. However it looks much better. The tiny defects I can polish out and I can powder lacquer it.

[Paul]

I don’t know whether this is genius or madness, though it might be quicker or cheaper than getting a new bike.
Whatever, it’s a complete pleasure to watch. Thanks.

[lkingscott]

I don’t know whether this is genius or madness, though it might be quicker or cheaper than getting a new bike.
Whatever, it’s a complete pleasure to watch. Thanks.

It's taking a lot longer than expected, but I'm having fun doing it and it makes such a change from work!!!

The initial hinge fix was relatively easy, but getting the alignment right was more difficult and took a bit of fettling, as the hinge pin is not parallel with the faces, in order that the frame folds in the way it does to miss everything else. After spending the time on that, it seemed that I should put in the effort on the rest.

It has given me the chance to learn TIG brazing and powder coating too!

In parts it's not been expensive, but time it obviously has. However, if I were to do another, it would take a fraction of the time! I doubt there's many Bromptons out there needing such work though!

[Paul]

I'll know where to come when mine goes wrong!

[lkingscott]

I'll know where to come when mine goes wrong!

 

[lkingscott]

Finally I coated the main tube. It's still too hot to touch, but it looks pretty good at the moment.

I managed to drop it as I was turning it to coat the back side, so had to go over it with more powder. It was difficult then to tell the powder thickness. I can see some slight orange peel around the bottom bracket. That took longest to heat up strangely and orange peel is caused mainly due to too little powder or heating too slowly. The hinge casting is a heavier lump of metal, but side on, the infrared only sees a small area of the relatively large bottom bracket metalwork.

I think I'll put a hole in the top of the box to allow the part to be rotated as it's cooking.

[lkingscott]

It came out pretty good.

However the coating cracked and peeled around the ends of bottom bracket when I removed the plugs. One YouTube video recommends to remove plugs before heating, but that risks damaging the fragile powder coating.

I might add another coat to the bottom bracket, or just try to touch it up.

[Lightning Phil]

Fascinating watching something that isn’t in my skill set being done so well (from my perspective).

[lkingscott]

Fascinating watching something that isn’t in my skill set being done so well (from my perspective).

It wasn't in my skill set until I tried. 

I love making stuff.

I was sewing clothes for my teddies and dolls when 4 or 5 years old.

I built a transistor radio from a Ladybird book when I was 9 years old. My father was an architect and had no knowledge of such things, but was very encouraging and bought the bits I needed when I asked.

I self learnt how to solder in my teens and was soldering up computer boards with 50 or more chips for £10 each for a shop which sold kits and ready built computers, while still at school before I went to poly.

I did electrical and electronic engineering at polytechnic, which also included some embedded software. The polytechnic tried to promote a more practical attitude in their degree courses and as electronics and software never works in isolation, we were taught a bit of practical mechanics. We learnt basic gas welding, brazing and machining - we all made a toolbox and vice.

Everything else is self taught.

When I was a student and had no money, I learnt stick welding by chassis welding my car to pass its MOT (there was no internet to see how it should be done).. There were rather a lot of blow holes to start with! The original metal was more like rusty lacework before I attacked it! MIG welding was a doddle after that, point and squirt. TIG welding is a bit like gas welding with electricity (so long as the electrode doesn't touch the metal!!!)!

I learnt how to rebuild engines by pulling them apart and rebuilding, using books to know what needed machining or replacing.

I built a gas turbine from a truck turbocharger, just to see if I could do it. It worked and made all the right noises! The sound of old gas turbines starting up and Merlin engines doing aerobatics are 2 of the most beautiful sounds! 

TIG brazing and powder coating I've never done before this project.

I've lost count of other stuff I've self learnt by doing. I've sewn my own clothes, I do Woodwork, paving, built kitchens, plumbed kitchens, built bathrooms, plumbed bathrooms, rewired my house, renovated my house, built stone walls, built stud walls etc.

I don't knit, although I tried, it's just too repetitive and boring!!!

[lkingscott]

Here's a couple of pics of the brazed crack after powder coating.

The lump is visible, but better than a crack.

I could have easily welded it, but given that the crack has occurred, the stresses from welding could have easily resulted in new cracks. Also the inner tube diameter is critical for the seat post and extra weld metal inside the tube would have been a PIA to remove. Brazing uses much less heat, so should not crack again in this location.

I want to put a wax rust preventative inside the tube. I forgot to phosphoric acid treat the frame before coating (having spent some time working out what should work  ), but a weak solution of phosphoric acid in the tube now for a few hours to convert any rust in there would be better than nothing. As the plastic seat tube insert goes here, some sort of elastic adhesive would probably best prevent the rust and hold the plastic insert. I will use a wax rust preventative in all the other tubes and this tube after the insert is glued in.

[mrcharly-YHT]

'Framesaver' is very good.


More expensive than similar 'waxoyl' types, but runnier, so it tends to get to all locations.

Wish I'd used it on my Brompton, maybe it wouldn't have rusted out.

[lkingscott]

'Framesaver' is very good.


More expensive than similar 'waxoyl' types, but runnier, so it tends to get to all locations.

Wish I'd used it on my Brompton, maybe it wouldn't have rusted out.