Old Bike, New Tricks

I used to love cycling as a youngster, but as soon as I passed my driving test the amount of cycling dropped off. Getting motivated to jump on the bike, given that almost every route out of where I live involves climbing some hills means that my bike has been gathering dust for too long.

I’ve always owned decent bikes, not at the multi-thousand-pound lightweight carbon level, but always decent enough that the groupsets work reliably. As my weight increased I swapped a lightweight road bike for a mountain bike thinking that the riding position would be more suited to my physique and that getting off-road would be nicer than breathing diesel fumes and particulates.

The reality is that because my daily routine normally involves a lengthy commute, the desire to jump on the bike after a long workday was diminished and at the weekends the motivation was frequently not present.

Covid-19 changed that dramatically though, I’m fortunate that I’m able to work from home during the pandemic, so life rapidly adjusted to this new regime – starting work earlier, as there’s no need to commute and finishing earlier opened all sorts of opportunities for cooking family meals and getting out on the bike.

The bike in question is this, a Marin Bobcat Trail, circa 2006:

Owing to little use and the fact that I always service / maintain bikes carefully, it’s in fantastic condition despite its age. Riding it though wasn’t as much fun, I soon found that the saddle wasn’t as comfortable as I remember, and the forward riding position was leaving my hands numb after a reasonable ride distance, owing to the pressure on my palms.

Some Googling suggested that changing the handlebars for a set with some sweep, allowing the hands into a more natural position would probably help significantly. I opted for a set with both some rise and sweep, for a more upright touring position. Handlebars, a new saddle (a Fabric Scoop Radius Elite) and some deep palm grips, for added comfort, were ordered and promptly fitted.

This helped enormously, especially the handlebar changes, ride distance was less limited by comfort now and more by stamina.

The knobbly tyres were also far from ideal for road riding, so a set of Continental Double Fighter III tyres was also ordered, to offer smoother road riding while still able to cope with some looser surfaces. These still haven’t arrived owing to the incredible demand on cycling retailers during the pandemic. Lots of people are buying bikes, or servicing and dusting off old machines it seems, now we have more time to exercise.

A Spark of an Idea

For some time I’ve been looking at electric bikes; as pre-built machines they tend to be expensive and, at the cheaper end, there’s always the feeling that the bike I already own is of better quality. There’s a growing industry in after-market conversion kits that you can add to an existing bike and my thoughts turned to those as an option. I’m in the very fortunate position that I’m saving almost £300 / month in fuel costs through not having to drive to work, a privileged position I’m intensely aware of when compared to many, so it seemed a reasonable idea to invest some of those savings to help flatten some of the hills around here and try and do something about my fitness levels and largely sedentary lifestyle.

My brother had previously taken a lightweight Trek MTB and had added a motor, but went for a heavy direct-drive unit, which transformed the feel of what was a light agile bike, into something he didn’t really like, so he advised me to look at geared hub motors, which are relatively inexpensive and lighter.

There’s essentially two types of electric drive you can add to a bike (if we ignore friction drive systems), mid-drive systems that add a motor near the bottom bracket and drive the bike through the existing drivetrain. They are great for off-road and where steep hills are the norm, as like a car you can change gear and allow the motor to operate at its optimal speed/torque. Mid-drive systems are a little more complex to install and tend to be more expensive. Also, in the event of a chain / drivetrain failure you’re stuck without assistance.

The other option is hub motors. These are available in direct drive and internally geared versions. The former can be very powerful but also heavy. The latter tend to be lighter, as they consist of a smaller motor element, with an internal planetary gear system with gear ratios that mean the motor is spinning 3-13 times faster than the wheel. Hub motors can be incorporated into either the front or rear wheels, front-wheel conversions make for a very simple installation, a rear-wheel conversion will require you to swap both disc brakes and cassette/freewheels over so you will need the tools to do that.

After lots of research looking at various UK sellers, I came across Woosh Bikes, a UK company based in Southend-on-Sea. They sell both a large range of ready to go electric bikes, all assembled on their premises and also a range of geared hub kits, for converting an existing bike.

As mentioned previously, UK cycling suppliers have seen unprecedented demand during the pandemic and their website implied they had no stock until the end of June. The stock situation is no doubt worsened by the supply channel issues, since most of the parts for ebike conversions are sourced from China.

Still, no one else was offering such a comprehensive range, at such competitive prices, so I contacted Woosh to ask some questions about the ideal kit for me. As recommended I sent Woosh photos of my bike to try and identify any fitting issues and to help with recommendations for parts.

UK Ebike Law

For an ebike to meet the definition of an “electrically assisted pedal cycle” (EAPC, or ebike, or Pedelec) it has to have the following features:

  • Pedals that can be used to propel the bike
  • An electric motor with a maximum continuous power rating not exceeding 250W
  • A maximum assisted speed (when pedalling) of 25km/h (15.5 mph)

If the bike has a throttle it should not provide assistance above 6km/h (3.7mph), although bikes manufactured or imported prior to Jan 1st 2016 do not have this requirement.

It seems that within this spec there is quite a variation in interpretation, so motors with the same nominal power rating have different torque ratings and quite different peak power capabilities. The ‘maximum continuous power rating’ spec allows for significantly different peak powers. Woosh offer both 36V and 48V systems, on a range of motor types, ranging from 1.5kg Brompton kits offering 35Nm of torque, up to 5.1kg kits for fat bikes, offering 65Nm of torque.

How much power is enough?

I’d no idea what torque I needed, or how to relate to it in terms of real-world riding, but after my email exchanges with Tony at Woosh bikes, it seemed that based on the all-up weight of the bike, the XF08C kit or the SWX02C kit would be ideal. My existing rear wheel uses a Shimano cassette, so the XF08C was the obvious choice, but as it turned out by the time I’d got round to placing an order, they’d run out of stock and only had 85SX kit available.

I received a call from Andrew at Woosh explaining the stock situation and offering the 85SX kit as an alternative. I was a bit wary, having spent so long deliberating, as the 85XS is a lower torque motor (40Nm) but also it’s very light, adding just 2kg to the bike (ignoring the battery). After some more deliberation I opted for the largest battery, the 36V, 17Ah (612Wh) option and committed to the purchase.

I’d been very clear in my mind that I didn’t want the ebike conversion to do all the work, just to flatten some of the climbs and allow for longer rides, Andrew seemed confident that based on the rides I was already doing, I would find the 85SX suitable. I have to confess to being concerned that I’d be disappointed when it arrived, but equally I wanted to get the bike back in regular use so waiting for new deliveries wasn’t really an option.

The kit promptly arrived and I set about the conversion. Woosh provide pretty much everything you need in the box, along with clear instructions, but you will need some tools to remove cassettes/freewheels and bottom brackets for some installation options.

The key parts supplied in my kit were:

  • Wheel, with hub motor and rim tape
  • Battery cradle / controller (fits to the bottle bosses on downtube)
  • A thumb throttle (optional)
  • A cadence pedal sensor and magnet ring (Pedelec sensor)
  • Brake sensors (when using a thumb throttle these are a necessity and disable the motor when the brakes are operated, the inline sensors I opted for are very tidy if you have brake levers integrated with shifters)
  • A wiring loom to connect everything together, featuring very secure and waterproof connectors
  • An LCD display
  • Miscellaneous parts (cable ties, aluminium rivnuts, key for locking the battery to the cradle etc.)
  • Battery
  • Charger

Fitting the kit

Woosh provide a comprehensive instruction manual with the kit (they have a comprehensive support page here, so you can read manuals/instructions ahead of purchase), which takes you step by step through he installation steps. You can read those manuals for yourself so I’m just going to concentrate on the challenges I experienced whilst installing, that you may also come across.

Pedelec sensor

I had hoped to use the left hand (non drive) side sensor that Woosh offer, but there was insufficent space on my bottom bracket to allow for it. Instead I was supplied the magnet ring and holder below.

This part consists of a small hall-effect sensor that senses the rotation of a plastic ring, into which magnets are embedded. For my bike this proved to be the most challenging part to fit. I have a triple chainring setup on the Marin and the smallest chainring is not dissimilar to the dimensions of the magnet ring. The ring comes with a holder and I was hoping that I would be able to screw it to the smallest chainring in some way, but this just wasn’t possible. Other suggestions involved bonding it, but I wasn’t entirely happy with that option as I wanted to retain easy serviceability in the future.

Fortunately I have a 3D printer so set about designing a two-part minimal clearance adapter to securely fit the sensor ring.

You can see the design in Onshape and you are free to take a copy and modify it to your own requirements. The finished result is really elegant and allows the chainrings to be easily serviced as it’s held on with some M2 screws that fit the existing holes in the sensor ring and Nyloc self-locking nuts.

The next challenge was fitting the sensor, the standard right side mount uses a very elegant metal bracket that fits securely behind the bottom bracket cartridge or cup. Removing the bottom bracket on the Marin and trying it made it clear that there was insufficient clearance between the smallest chainring/sensor ring and the sensor. The image below was with the first prototype sensor ring mount, but even when that was slimmed down, it was clear the sensor was not going to fit.

Woosh had omitted to include the seat tube mount they’d recommended (very quickly sorted by Andy at Woosh) so as a temporary solution I broke out the CAD and the 3D printer again and designed a sensor mount that I could transplant the sensor onto, securing it to the seat tube. Things are really tight in there, so a couple of iterations were required to get the clearance correct.

For most installations the above would be unnecessary as the various other sensor options Woosh offer would be suitable, but there’s no point in being an engineer if you don’t use those skills and tools to design elegant solutions and I’m really pleased with the end result which is both secure, elegant and easily serviceable.

Battery cradle / motor controller mounting.

The battery cradle contains the motor controller and is a straightforward fit to the bottle bosses on the downtube. You may find, as I did, that to get the cradle into the correct position that allows the battery to be fully seated, the existing frame bosses are in the incorrect position (or you may not have any at all!).

Woosh thoughtfully provide a couple of aluminium rivnut threaded inserts that you can use to resolve this. In my case, the lower boss was in the perfect position, but I needed to fit a new one in the upper position. The process is as simple as drilling the correct size hole for the rivnut and I recommend keeping the clearance tight for a long-term secure mounting. For my installation I drilled to the size below and carefully enlarged the hole until the rivnut was a snug fit. I bought an inexpensive rivnut tool to fit the insert, but you can improvise quite easily with a suitable bolt/washer/nut:

In addition, I mixed up some strong epoxy adhesive and applied a small amount around the area of the rivnut that goes through the frame. This further reduces the risk of the rivnut becoming loose and turning over time, something that from experience can make removing the screws later on a problem! Finally I used some non-permanent thread-locking solution on the screws to ensure they don’t work loose but are serviceable; the battery is the heaviest part of the system and our roads are bumpy!

Brake sensors

The inline sensors I used are simple to install and very elegant, but you may need to extend the inner cable or shorten the outer sheath to take up the additional length they add. If you are making other changes at the same time, like fitting different handlebars, don’t do what I did which is to fit a longer rear brake cable that the higher handlebars required, only to find it too short after the ebike kit arrives 🙂

Final tweaks and lessons learnt

Since the original installation I’ve made a couple of tweaks to the system based on experience:

Thumb throttle

I originally fitted the throttle on the right side of the handlebars, but it did make changing gear slightly harder with the thumb shifters, as I had to move the brake lever/shifter assembly inboard as the new handlebar grips weren’t conducive to being shortened. I’ve come to realise that I use the thumb throttle very rarely and that the front chainrings see very little use (I haven’t used the smallest ring at all, even on the steepest climbs). The rear provides most of the adjustment to cadence required, so to that end I’ve moved the throttle to the left-hand side of the bars, which works much better for everyday use.

Cable ties to Velcro

Woosh provide cable ties to secure the wiring looms to the frame. They warn not to overtighten them as that can damage the wires, but another issue is serviceability, standard (non-releasable) cable ties have to be cut off and replaced if servicing is required and in particular the challenge of punctures and rear wheel removal needs to be considered. I’ve since changed all the cable ties that hold the wiring in place with these excellent hook and loop ties. Not only are they impossible to overtighten they are very secure and trivial to remove and re-fit for servicing when necessary, reducing a small amount of plastic waste.

The end result

The conclusion of all this is I’m enjoying cycling again! Since the photo above I’ve added the rear carrier and lost the triangle bag, so I can set out with a set of panniers to carry picnics, drinks and tools for some longer rides.

My concerns over motor power were not necessary, the compact Aikema 85SX motor provides plenty of assistance (I did two hill climbs, after a 10-mile ride, simply to test the capabilities of the motor as I didn’t feel totally exhausted). On a 1 mile 6% gradient I was able to cycle at the 25km/h limit with max assistance (level 5) and still be able to talk when I got to the top. I then immediately tackled a 12% gradient I hate and was able to cycle at around half that speed and again not be totally exhausted when I arrived at the top. The heart rate graphs from my rides show that I’m still working, with an average heart rate similar to that pre-modification, but I’m able to cycle for longer and the whole experience is more enjoyable. I believe the exercise I’m getting will be just as good, or better, simply as I want to go out riding now, as I see it as less of a chore and more of an opportunity.

Battery range seems good too, I’ve done 40 miles with a fully laden bike (two panniers and a heavy water bladder) and my fat a*** in the saddle, with a lengthy climb halfway and still returned home with 1 bar on the display and had plenty of assistance for the return journey. Woosh quote 50-60 miles for the battery I have, but of course that’s totally dependant on the riding conditions and all-up weight. My underlying bike was around 14.3kg prior to installation and I’m not exactly svelte! For a gentle ride I find assistance level 1 or 2 is plenty, for steep climbs a temporary increase is useful, or for when you want a faster journey with less sweat. The assistance levels feel to me as if they offer assistance up to an increasing speed threshold, rather than limit power output, so assistance levels are a trade off between desired speed, pedalling effort and desired range. The end result though is a bike that’s flexible and versatile and I’m delighted with it!

Customer service

Many UK businesses have really suffered during this pandemic, so it’s been great to find a relatively local business with such excellent support and customer service. Woosh Bikes have been great from all of my incessant pre-purchase questions, ably handled by Tony, through to after-sales support from Andy. I’m so glad I purchased this kit from a company that has thought about the products they offer, has experience in installation and offers rapid and excellent support even after they’ve taken your money.

I highly recommend talking to Woosh if you have an old bike that hasn’t seen much use recently, or if you are looking to purchase a new ebike, their prices are highly competitive and their support is excellent.

You can view their website here: https://wooshbikes.co.uk/

You can contact them through their web contact form here: https://wooshbikes.co.uk/?contactus#

Or email them about hub kits on this address: kits@wooshbikes.co.uk

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