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Sunday, 30 October 2016

Repairing bicycle wheel bearing cones

How to repair pitted cones with simple equipment

Many, maybe most, old bikes we repair have at least one wheel bearing cone with pits in the track where the balls roll. Here’s an example with pretty bad damage:
click on the picture to see closer in
Cones aren’t always that bad, often it’s only a single small pit.
If you keep riding on damaged cones, you can wreck the whole hub. Over time the damage to the cone is likely to get worse, then balls will be damaged, and then the bearing cup in the wheel hub will be damaged in turn. Pitted cups are rarely able to be replaced, we haven’t worked out how to repair them, so this is usually the end of a wheel – or at least the hub.
It appears to us that the usual cause of damaged wheel bearings is over-tightening of the wheel bearings. This is widespread bad practice: most brand new bikes we check have seriously over-tightened wheel bearings, and often have damaged cones after only a little riding.
It’s really important to learn to grease and adjust wheel bearings, or find a bike mechanic who does it well. Don’t presume a bike shop does it well, especially if they are selling new bikes with badly adjusted bearings.
Sheldon Brown describes how to adjust bearings in this page: http://sheldonbrown.com/cone-adjustment.html
Park Tools have a detailed tutorial on bearing service and adjustment here: http://www.parktool.com/blog/repair-help/hub-overhaul-and-adjustment#article-section-4
The usual repair for a damaged cone is to replace the cone and balls, or the whole axle assembly. This is fine if you live next door to a bike shop with a comprehensive stock of cones, but there are heaps of different sizes and shapes of cones so it is not straightforward to replace them. It is also a waste to discard a whole axle assembly because it’s missing a few milligrams of steel in a special place.
We’ve had very good results with grinding and polishing the bearing surface of damaged cones and using them again – for 1000s of km. Once or twice I’ve had re-ground cones develop a groove along the ball track, presumably because I ground off a very thin layer of case hardening, leaving only soft metal. However most cones appear to have deep enough hardness to be re-ground and work well. The job only takes a few minutes, in addition to the time it already takes to dis-assemble and inspect the bearings.
Jasper and I have developed slightly different methods. I use an angle grinder, he uses a dremel with a small grinding cylinder. Both methods have yielded good results.
We start by locking the cone and a locknut together on their axle, with about 40mm of axle behind the locknut to go into the chuck of a drill press. Like this:

If you use an angle grinder, the drill press table needs to be adjusted so the disc guard can be rested on the table, while the grinding disc contacts the cone. Then you need a steady hand. Here is how we do it:

Using a dremel (Jasper uses a cheaper “Demel” from China) is easier, perhaps a little slower, and smoother. Here’s how Jasper does it:

Here's a cone ground with the dremel, unpolished:
After grinding, the cone needs to be polished. We wrap some sandpaper around a small cylinder (such as a round pencil or a piece of brake cable outer) and sand the spinning cone until smooth.
Then the cone looks like new:

This is bush engineering, and it may appear rough. However they usually feel very good after greasing and assembling, and nearly all have lasted very well in heavy use. As far as I can see, most cheaper new wheel bearing cones aren’t ground after heat treatment, so they aren’t super accurate. The action of the balls rolling around tends to deal with small inaccuracies, and if greased and adjusted carefully, the bearing will make itself more true with time.


Thursday, 20 October 2016

Makita 7.2V cordless drill repair: lithium batteries

More than 20 years ago I bought a Makita cordless drill. It did a lot of work, but the batteries eventually died. The non-genuine batteries I bought on ebay didn’t last well, so the drill languished for years. The drill was good quality (for its time), with a keyless chuck, so I couldn’t bring myself to throw it out.
I recently repaired it, using a pair of Headway Lithium Iron Phosphate cells from a broken bike battery. It now works like new, but with much more energy storage.
I made a battery pack from two 10Ah 38120 cells, with soldered connections (all my newer Headway packs have bolted connections, which I really like). The 2 cells are connected in series to give about 6.6V, and have small Anderson plugs on a lead to connect to the drill. The drill has wires soldered onto the battery connection spring tabs (the drill needs to be unbolted and split to access these), with Anderson plugs on the outer end.
2 single-cell chargers attached via the Anderson plug and the cell series connection
Recharging is done with 2 single cell 2A chargers which came from Ping, a company which sells bike batteries. We were sent the chargers with some spare cells when we had to repair some Ping packs (fixing Ping batteries is no fun! That’s part of why I like the bolt-together Headway cells so much). Each charger connects to a single cell with alligator clips and has an LED which changes from red to green when the cell is fully charged at about 3.65V. I cut a small window in the battery pack wrapping at the cell series connection to enable each cell to be charged independently.


The little opening in the paper mache at this end is where the single cell charger clips are attached
There is no BMS to protect the cells, but the very high capacity of the cells (5 times the capacity of the original battery) means that the cells should be safe if I charge reasonably often. The Anderson plugs enable the battery to be disconnected to avoid accidental discharge.

The battery pack has a paper mache wrapping. After the connections were soldered, the cells were wrapped in thin polythene to keep them dry (an old plastic bag), then wrapped in several layers of used office paper and PVA glue (slightly diluted). This paper mache forms very nicely into shape, and dries to a tough material.
The battery pack is attached to the drill with rubber bands cut from a bicycle tube. These bind the battery onto a piece of plywood with is attached to the foot of the drill handle with string and PVA glue - a strong, cheap and versatile joining method. 
4.5mm plywood attached with string and PVA glue
bands cut from a bike tube hold the battery very firmly
Now I have a low-spec cordless drill which should last for a few more decades, with occasional battery changes.





Thursday, 6 October 2016

Dahon handle post repair

One of our Dahons broke down again recently: a split in the handle post, lower tube. It broke like this:

I removed the original cam and bolt, and tried putting a hose clamp around it and tightening as much as possible, but that didn’t work at all. Clearly the job needed a lot of clamping force to hold tight.
Here’s how I fixed it. First I drilled and sawed a longer split down the tube.
You can just see the extended slot and hole down the left side of the lower tube

Then I made a custom clamp, starting with 16mm square solid mild steel bar. I heated it in the forge, and fullered two Us into it, first with a smaller fuller, then this one which had very close to the same diameter as the handle post.

I cut the pieces off the bar. I drilled and tapped the pieces for 6mm bolts, and ground them roundish so they wouldn’t destroy anyone’s knee cap in a crash.


Not lightweight, but works really well. 

Sunday, 2 October 2016

Electric bikes for kids

We’ve had a lot of success in using ebikes for transporting our kids, despite living in challenging circumstances for this: steep country and relatively long distances. Our little fleet of electric bikes has enabled us to avoid a second car (almost unique amongst our parenting peers) and kept our family economy out of trouble during some years of high costs and low income. They’ve also helped build our children’s sense of self-worth and independence.
Parents in affluent countries spend a lot of time and a lot of the family budget on transporting their children around in cars. As well as cooking the planet, “taxi-parenting” has a high financial cost: running a second car costs are in the $5000 to $20,000 per year range, without taking into account the health costs, car storage and parking costs, or the unproductive time spent. I think that there is an even greater cost: undermining our childrens’ capability and engagement in the world. Transport has become a totally passive exercise, with even older teenagers being pushed in 2 ton prams to school each day. We are telling our children that they are incapable of getting themselves where they want or need to go, and disengaging them from the world – how many or our children are also staring at screens while being driven around?
Of course there are risks to children travelling by bike. However the health risks to children of taxi parenting are enormous: look at the declining health of children in affluent countries. Consider also the cost to their spirit and sense of themselves.
Babies and toddlers on bikes
Small children are probably the easiest to transport by bike. Heaps of baby seats are available for attachment to normal transport bikes, as well as trailers. I carried our youngest around in a rear baby seat for a few years, until he was too heavy for me to keep the front wheel on the ground when I was pushing the bike up hill. At this size it was difficult to transport our kids far by bike, until we got the Xtracycle. 

Small kids on bikes

Our first electric Xtracycle cargo bike was a total game changer for child transport. Starting when he was 6 years old, Luka travelled 1000s of km on the back of my Xtracycle and had a hoot. Transporting Luka also kept me fit and sane while Erika went back to full-time study.
Getting wet isn't so bad
Luka was around 25kg for most of his time on the back of the Xtracycle. We burnt out one Bafang SWXH hub motor on the slow, steep climbs, before installing a Bafang BPM (which has done 8000km without trouble since then). I attached footrests for  Luka, which are important for mounting and dismounting, and give stability while riding. I had intentions to fit rear handlebars, but Luka was fine holding onto either my belt (warming his fingers on cold days) or my seatpost.
Once Luka passed 30kg, he got harder to haul. He also was getting old enough to ride his own ebike, so I made him one. Interestingly, my google searches for info on kids’ electric bikes yielded nothing.

Kid’s bike 1


Luka’s first bike was small: 20” wheels and ??cm seat tube. It had a Shimano 3-speed hub with roller brake in the back and a Bafang SWXK front motor with V brakes (brake studs TIG welded on by friend Ian Aitchison).
I designed this bike to be easy to use: Luka wasn’t an experienced rider. It’s been hard to teach our kids to ride, living on the mountain, as there are very few flat places they can safely ride. Thus this bike was the first bike Luka did a lot of riding on at home.
Luka and his friend Rudy lacing the 3-speed wheel
As the bike was something of an experiment, I made a quick and easy battery box from papier mache. I glued (using Bondcrete PVA) a box from corrugated cardboard (from normal fruit boxes), then layered on scrap paper with diluted PVA. Once it had dried thoroughly in the sun, I gave it a couple of coats of enamel paint to make it somewhat water resistant. I used a heavy plastic bag as a waterproof lid. This box withstood many crashes!
To carry the battery box I had to make a custom rear rack. I used pieces of cardboard to mock up the shape of the rack and get accurate dimensions. The rack was fabricated from 6mm/1/4” mild steel round bar – I get it as straight drawn wire, which has a good finish (compared to reinforcing steel). This is easy to weld (with stick welding), strong and easily repaired, even if it is a bit heavy. After fabrication, I paint these racks with standard steel primer and enamel.
Rear rack welded and painted
Using a front motor ended up being a real problem – which was a surprise to me as I have ridden 16,000km on my front motor, 20” folding bike. With a light rider and a front motor, there isn’t enough weight on the front wheel to achieve adequate traction going uphill, when the road is wet or loose. When the road was wet, Luka’s front wheel would be skidding for kilometres on long steep climbs, making steering difficult. Getting started on our long dirt access road was very difficult: throttling would tend to cause a front wheel spin, making the bike unstable when trying to mount. 
Despite the front wheel skidding trouble, Luka travelled 100s of km on this bike, riding behind me, to play dates and wherever we needed to go locally. As Luka was growing quickly at the time, I changed handlebars to riser bars after a few months. However eventually Luka decided the front wheel skidding problem was no good, and we made him another bike with a rear motor.

Kid’s bike 2



Luka’s current bike (2016) is a folding bike salvaged from the tip, with 20” wheels, 6-speed derailleur gears and V-brakes. To avoid the trouble of making a battery box I bought a bottle battery with 18650 cells from Greenbikekit.com. The folding bike had a strong rear rack, so the whole assembly was quite quick and easy.
The rear motor works very well: no skidding, so no trouble on wet roads and Luka can even ride up our steep access road – making trips out significantly quicker.
As with all our ebikes, Luka’s bike has mounts for front and rear lights, and carries panniers. As it is a folding bike scaled for a smallish adult, it will fit him though a fair bit of growth. Like all/most folding bikes, the short wheel base puts most of the rider’s weight on the rear wheel, which gives some riders a sense that it is at risk of unplanned wheelies. I may build it a front pannier rack (like I use on my folding bike) to help balance this.
Although the bike is a cheap, steel folding bike, it seems to be quite robust, especially compared with much more expensive Dahons. Hinges and locks for the folding mechanism are simple, robust and look like they would be easy to repair – we’ve had a lot of trouble with these parts of Dahons. Being steel makes it easy to repair or modify, e.g. we could braze or TIG on disc brake mounts if it goes into frequent use by someone heavier (the long steep descents around here wear away rims using V-brakes, and risk tyre blowouts from overheated rims).

Teenagers and bikes


Jasper on his way to school. Steel-framed Dahon with 20" wheels, rear Bafang SWXH hub motor, Headway 36V battery 
Our oldest, Jasper, has been a frequent ebiker since highschool. In his last highschool year he rode to and from school nearly every day, 17km and over 800m gross altitude of steep slopes each way. This was a success from a range of aspects. For starters we were able to get Jasper to school each day, without buying a second car, and without spending hours each day driving him in it – this would have cost more than the school fees. Cycling helped Jasper develop skills and self-esteem: we were all proud of his daily achievement, reinforced by many statements of admiration by friends and neighbours at his riding up a mountain every day. The big challenges included remembering to recharge his battery every day at school. Samford Steiner School staff understood what we were doing and were very supportive. While at school Jasper used a folding bike, which gave him more options to get lifts with his bike in family or neighbour's cars - especially on the big climb. 

The parent role

If Mum rides, the daughter will ride
Getting our kids on bikes is clearly a social process, more than a technical one. As with every element of parenting, it starts with modelling. If you want your kids to cycle for transport, they need to see you cycling. We need to ride with them, a lot, to develop their skills and confidence. We’ve made a bit of a fuss about presenting our kids with particular cycling clothes, panniers and bikes, to give them ownership. I’ve also made a commitment to cycling with them whenever the younger ones want to go somewhere, if I think it’s the safest thing or when they want the sense of support. Being ready and willing to ride them somewhere when they want provides balance to my lack of willingness to drive them around. This seems like a big time commitment, but pays back in multiple ways. Riding with your kids can be one of the great pleasures of family life, especially the stops along the way. Of course teenagers are likely to do what they are programmed to do and criticise, express embarrassment, and seek the chauffeur treatment received by their peers. I’ve learnt to stick to the plan, and remember that the joke of history is on them: kids grow up to be like their parents.
A bunch of young folk on their way to a party off the mountain

Breaking the paradigm

In many communities our patterns of travel have been profoundly shaped by the car, requiring children to be driven around by their parents several times per day just to participate: in school, friendships, extra activities, etc.. This car-dependent and parent-dependent culture, plus the digital screen age, are creating an extraordinarily disengaged and de-skilled generation of children. This is a real challenge for parents who want to take steps away from high car dependency, build a less environmentally harmful and more resilient pattern of life and raise more capable kids who will be able to cheerfully adapt to a less affluent future. Taxi-parenting is a hard pattern to get out of: not only is it reinforced by the infrastructure we live in, but the paradigms of our peers accept this as normal.
Bikes and ebikes offer a strategy to disentangle from the car culture, while maintaining engagement with our spread-out communities. If your distances are big (but not too big) and you have access to safe-enough roads, electric bikes can help families travel through their weekly routine, when walking or push-biking might have been too slow or difficult. They make cycling achievable when you have to carry loads or when you are not feeling athletic. Ebikes extend your capability and help maintain transport, without a car, in communities which have been shaped by cars.