Nazca Quetzal E-Tandem Retrofit

This year, we decided to electrify our Nazca Quetzal tandem. This was mainly to enable us to extend our day range in the hilly Borders, and to enable me to do long rides at the weekend with my wife without completely tiring myself out on the climbs. The Quetzal takes a lot of energy to get up the big hills, and being much bigger than my wife, I need to put in most of the power on the steep bits. I wanted the possibility of doing long, easy rides on the tandem which was impossible without a motor.

Nazca E Quetzal
Nazca E Quetzal

We settled on a simple kit from Whoosh Bikes in England. It’s a front wheel hub drive kit with pedal assist, but not torque sensing. This is quite an important distinction that some people not used to E Assist won’t appreciate until they try (like us!).

I wanted front wheel hub drive for two reasons – firstly, I didn’t want to put any more torque through the Rohloff gear hub than necessary with a mid drive system, as changing gears requires you to back off the power unless you want a gear jam. Secondly, at very low speed on extremely steep hills, the Quetzal requires a bit of concentration to keep it balanced and it’s a lot of weight to manhandle when you’re wavering around at 3 mph. I was encouraged by a post on Facebook from Nazca that described a front hub motor test as providing extra gyroscopic stability in exactly these kind of conditions.

The kit came with a sturdy high spoke count 26 inch wheel with integral hub motor, controller, 17Ah 36V battery and a mount for the bike complete with a vast array of cables. There’s a cable for the controller, one for a thumb throttle, one for a BB pedal sensor, one for the front wheel and two for the brake sensors. All in all it’s a big pile of cabling and this is definitely a ‘retrofit’ in terms of aesthetics, with a new bunch of cables running along the bike frame and up to the bars. All cables are wired into the mount so you can’t dispense with any of them. The kit was well packed and protected in transit, and had a decent instruction manual on how to put it all together. Note that you are expected to be a competent bike mechanic, as you need to be able to do things like remove cranks to install cadence sensors and so forth.

Hub Motor Front Wheel 1
Front wheel with hub motor

I’m pretty sure that an E-kit for a recumbent tandem is definitely an extremely niche market that the manufacturers don’t even think about! Being a standard bike kit, all the cable sizes were a bit off. Whoosh recommended fitting the kit on the bike and then seeing where the cables were short. They then got me to take measurements and made up some extensions. They arrived quickly and it all worked out very nicely.

Handlebars
Handlebars – dig the controller rotated by 90 degrees

Getting the kit installed was fairly straightforward. I had to take the stoker cranks off and install a cadence sensor. Cue a couple of days’ break to buy a crank puller for square taper bottom brackets, but that went fairly painlessly. The mount had to be attached to the back of the captain’s seat – the kit is supplied with rivnuts and again it was pretty easy getting the mount installed. It is however designed for a flat bike frame tube. This setup doesn’t work quite so well on a recumbent seat, which is curved to follow the shape of your back. I was also limited in the position of the mount by both the seat stays at the top, and the bike frame at the bottom. There is literally a few millimetres space and you need some vertical movement when sliding the battery in and out. It is a very tight fit! I also had to move my seat forward an inch to make enough clearance.

Battery on back of captain's seat
Battery on back of captain’s seat – it clears the frame by about 0.5 cm at the bottom

Everything else is installed at the handlebars – controller, thumb throttle and brake cut out sensors. The brake cut out sensors stop the motor from working whenever you pull the brake levers. The thumb throttle allows you to put through a burst of power on top of whatever setting you have the controller at.

Thumb throttle
Thumb throttle

The controller itself is designed for upright bike flat bars – on the Nazca aero bars this doesn’t work quite so well. If you put it on the top part of the bar, you run the danger of hitting it with your shins. You do this once with your Garmin, note the pain and gash it creates in your shin and then decide not to put anything else up there ever again 🙂 So the controller is now down next to my right hand, but rotated 90 degrees clockwise from how it is intended to be. Not ideal, but to be honest all you need to do is push a button now and again to get the desired level of assist so it’s fine in use.

Controller
Controller

The brake magnets and sensors were a little tricky to install too – I couldn’t find a nice spot on the brakes to put the magnets, which are supposed to be zip tied onto the levers with the magnets on the main brake housing. In the end, I superglued the magnets onto the end of the lever reach knobs, which works very nicely. You need to make sure you get the distance between the magnets and sensors right, or you can find the controller thinking you’re pulling the brakes all the time and refusing to turn the motor on.

Brake sensors
Brake sensors with bad cable measurement results

The thumb throttle was a simple install next to my left hand. As previously said, Whoosh asked me to install everything, then measure up the gaps to get cable extensions. I did this, and they gave me exactly what I asked for. Somehow I completely messed up the throttle cable measurement, so I have a cable that’s a few inches too long, hence the little loop. Entirely my fault, and not Whoosh.

Installing the new front wheel was also very simple – swap the rotor, tyre and tube from the existing wheel, and then use the supplied torque washers to get the wheel installed with the correct spacing for the disc caliper. I had to experiment a bit with different spacings until I found a combination that worked. The main thing is to install the torque washers so that they are pushed flush against the dropouts to counteract the torque of the motor in the hub. The wheel itself is reasonably heavy as you would expect, but spins very freely when coasting. This was important – I wanted a kit that would not make the bike really hard to use if we ran out of power in the middle of a ride. There’s a cable to connect to the mount. All in all the bike now has quite a lot of cabling. Most of it could follow the existing brake and gear cables so it’s still fairly neat, but there’s a lot of cables at the bars, no question. If you’re an aesthete this may not appeal to you. Being a recumbent rider, I’m used to cables being zip tied to things so it’s not a problem 🙂

Front wheel cabling
Front wheel cabling – zip tied to mudguard to keep it neat

Once it was all put together, I slotted the battery in and it was ready to go. First problem I had – I couldn’t lock the battery onto the mount. There’s a key to move a little metal button in the battery down into a corresponding socket in the mount, but because of the seat ribs getting in the way, I can’t get the key into the slot. I tried a couple of rides with a velcro strap around the battery and mount which works most of the time, but discovered that on a big bump you can still knock the battery out of the mount enough for the power to disconnect. So now I put a little bit of gorilla tape across the end of the battery onto the back of the seat to keep it secure. This is not ideal, but solves the problem and only takes a few seconds to do. I haven’t figured out a better way of fixing this yet short of replacing my seat with one that has smaller ribs, which I’m not in any hurry to do.

Other than this small issue, everything works very well. You turn the controller on, and you’re ready to go. If you have the brakes pulled when you turn it on, you get an error because the controller can’t sense the magnets – you need to switch it on with the brakes not pulled. You get 5 levels of assist. Level 1 feels like nothing more than enough to remove the extra weight of the kit. 2 feels like a bit of gentle help on the hills. 3 gives you a pretty decent push on hills, 4 and 5 are like having a pro cyclist as a stoker, you fair fly up the hills on these settings. My initial doubts as to the efficacy of a 250W motor on such a heavy tandem package in very steep terrain was immediately eased – it can drag you up 15% gradients and although the motor does sound like it’s labouring a bit at such low speed, it nevertheless still works fine.

This is a cadence sensing kit, not torque sensing, so it’s not the same as a natural, but enhanced, pedalling experience such as what you get on a torque sensing setup. When the motor kicks in, it is very much like having someone giving you a bit of a push on top of your own pedalling. If you’re looking for a ‘natural’ but stronger pedalling experience, go for a torque sensing kit. This one is cheaper and doesn’t feel the same. For our use case on the tandem, it’s fine, but I wouldn’t want it on my day to day bike if I was using it all the time for commuting etc.

Cadence sensor
Cadence sensor

The kit is UK legal, i.e. 250W and cuts out at around 15.5 mph. The different levels of assist appear to fade out at different speeds, with 1 fading out at the lowest speed and 5 pretty much boosting you up to 15.5 mph before fading out. The fade out as you accelerate is very smooth, but for some reason on the way back down, the controller waits until you hit about 12 mph before kicking in. On the lower settings (1 and 2), you don’t really notice this as the assist is quite gentle and at a lower speed anyway, but on a higher setting, it can be a bit weird. You get a good push along, and then you’re maybe doing 20 mph down a little hill. You hit a steep climb, and you quickly lose speed on the heavy tandem. You drift down past 15 mph, and instead of the motor fading back in, you decrease further down to 12 mph and then the motor kicks back in full blast, and you suddenly accelerate again. So you end up dropping down a gear or two more than you need to due to the lag in the motor kicking in, and you then have to change back up again once it gives you a boost. If you’re riding at, say 14-16 mph, the motor won’t kick in when you go below 15 mph because you haven’t dropped back enough. This is the only thing about the kit I don’t like. If it kicked back in at a higher speed it would be perfect. As it stands it’s a bit annoying and doesn’t work so well when you’re hovering around the threshold of 15 mph or hitting steep hills where you want the power on straight away. We did however buy a cheapish kit for the purposes of easing the long hills on long days out, which it does very nicely.

Other than that one annoyance, the kit has been really good so far. The amount of assist you get seems to be speed related, so even on level 1, if you’re winching up a 15% slope at 3 mph, the kit will give you the full 250W to try and get you up a bit faster. And it’s amazing what a difference that assist makes. Prior to adding the motor, the bike was a bit of a handful on some of the steeper hills, such as Windydoors on the outskirts of Stow, which has a section near the top that required both of us to go fully anaerobic for the last pitch to keep the bike moving forward. With the motor, even on a low setting, We can now, if we wish, keep a nice low heart rate and cruise up in zone 1 or 2. Of course you can still put in the full effort if you want, but you don’t need to any more, which is nice.

Out and about on the E Quetzal
Out and about on the E Quetzal

Starting off is now really easy too – you clip one foot in, start pedalling, and vroom, you’re off and accelerating for very little effort. Great for uphill starts on such a heavy bike. Nazca were also right about the extra stability on steep hills – it’s easier to keep the bike tracking straight, and you can also take the pressure off the pedals just enough to change gear on the Rohloff, but still keep your feet rotating which means the motor continues to add power as you change. So climbing steep hills is simpler and more stable, and you don’t jam up the gears so easily which can be troublesome if it’s really steep as you lose speed so quickly.

We have settled on leaving the motor on setting 3 for most riding, which gets us up the steeper hills a fair bit quicker but doesn’t really do much on the flats as we are pedalling fast enough already. The overall speed increase isn’t huge, maybe 13.5 mph compared to 10.5-11 mph unassisted, but it’s a lot easier to get that speed without getting tired out quickly.

If you hold down one of the buttons when you’re stationary, the motor has a ‘walk’ mode where it supposedly propels the bike along at walking speed. In theory this is great (i.e. we have a steep drive and pushing the bike up the drive requires some effort) but in reality it’s more of a ‘jog’ mode, as even lanky me struggles to keep up with it without breaking into a trot. Just a little bit on the fast side to be truly useful.

The 17Ah battery seems to be pretty big. So far, doing the 40 mph reasonably hilly Innerleithen loop on setting 3 seems to use about a third of the battery at most. It’s hard to tell, because when you put it on level 1 it will show full still, whereas if you bump it up to level 5 it will then say about half full. Not sure how trustworthy the level meter is to be honest! It seems to be based on predicted usage on the current power setting, but I don’t know how to read that accurately yet.

During my recent lockdown double century my wife joined me for 50 miles on the Quetzal. I was keeping the same low heart rate as I did on the other bikes I used that day, and I had the power running full gas on level 5 which gave roughly the same speed as the M5 (about 16 mph average). So we had 50 miles on level 5 and the battery meter said it was still more than half full at the end. When lockdown eases we will take the bike out on a longer day and really test out the capacity, but so far it looks very good.

Tandeming part of my double century
Tandeming part of my double century

If you do run out of juice, then the hub motor kit adds no noticeable friction to the front wheel, so you can still pedal the bike home. We went out recently for a quick blast and I kept the battery at home just to see how it felt. It is slightly heavier obviously, but in the overall scope of a 30KG bike with riders and luggage, you don’t really notice a couple kilos more, and other than that the bike behaved exactly as it did before we installed the kit. So this means you can definitely do long days and judiciously use the battery as needed, and turn it off when you don’t need it should you so desire. I am hopeful that the battery is big enough to do 100 miles without running out of juice though. It isn’t a big deal to replace the front wheel, so you can disconnect and take the heavy motor wheel off, replace it with the original Quetzal wheel, leave the battery at home and other than some lightweight cabling up the frame, you’re back with the original weight Quetzal. I like this flexibility.

Overall, we both think this has been a very useful addition to the bike. It is nice to be able to keep an easy pace and still make good progress in the steep hills around here. If you lived in flat land I’m not sure it would be worth installing something like this – you can make the Quetzal go at a good pace on the flats through human power alone, but in steeper terrain it definitely takes the sting out of the hills, increases daily range and is flexible enough that it doesn’t turn your bike into an electric-only heavyweight option that is useless without a battery. The way the motor cuts in late when you hit a steep hill is definitely a bit of a niggle but I will probably get back in touch with Whoosh to see if there’s anything that can be done to reprogram that behaviour out.

Other than that – it’s a cheapish kit so I didn’t expect miracles. It feels reasonably well made, does what we wanted it to do, has what seems like a good range for such a big bike and has given us the ability to do some real ‘pleasure’ rides at a lower effort level than before. We’ll be keeping it on the bike pretty much all the time going forward from here.

Innerleithen loop
Enjoying the motor on the long climb out of Innerleithen

3 thoughts on “Nazca Quetzal E-Tandem Retrofit

  1. “The overall speed increase isn’t huge, maybe 13.5 mph compared to 10.5-11 mph unassisted”

    That’s ‘huge’ enough though and the fact you can take any route without trashing yourselves.

    Very neat – you may set a trend!

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  2. Sounds good
    I certainly enjoy a similar(Australian I think) front hub motor I installed on my delta trike- enables me to lug a 10×8 camera and tripod around without too much sweat and doing the weekly shop is a pleasant 10 mile round trip. I am getting about 50 miles on mid assist level.Battery (Samsung) is good but as soon as one bar is lost it goes down quite abruptly- it shows full power until about 40 miles -so just a question of getting used to it
    I didn’t bother installing the brake sensor things as the trike has 3 disc brakes (it’s actually a Dutch sail trike so has to be able to brake well) if I use the sail as well as the electric assist ,I might need to!
    Like yours it’s a cadence set up,the Copenhagen wheel on my StreetMachine is torque based – the only difference I notice is that if you try and start in too high a gear and can hardly turn the pedals, the cadence sensor does not trigger the motor due to lack of crank rotation ,but the torque one will immediately help you out
    What about electric assist on the M5 ! I see mention of it on their website-tyre rim based ,very small, very light ,very German and very expensive
    Maybe for my 80th birthday in a few years time!

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  3. You really need an AH meter fitted; in my experience battery lights are merely voltmeters which is not helpful as voltage stays relatively constant at low draw until about 70-80% depletion. Once you know the AH of your battery you can see how much you’ve used and correlate that to your range. Power draw will also be less when in the last 10% unless the battery controller has been programmed to cut off completely at 85-90% discharge.

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