Woosh C70 Brompton conversion

DBrown67

Pedelecer
Feb 26, 2017
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Leeds
Just received and installed my Brompton kit from Woosh today for my B75. Before I go any further I want to stress that I bought a kit from them without battery. This was because I wanted to use my existing 17AH HL battery I got in a kit from them over two years ago for my Cube MTB conversion. Plus I wanted to keep the use of the luggage block from my Brompton bag. So please bear in mind this isn't a review of their full kit.

However, I can say that installation was a doddle. One or two cables were a bit long but I was able to coil them neatly round the HL cradle mounts to shorten them. The mounts I used on the stem were Tesla pipe clips from Screwfix. Cheap as chips, and nothing to do with Tesla cars :) As you can see from the pics the way I've mounted the cradle isn't the most elegant but is there a better way? But looks aren't everything... especially with a Brompton. They can be a bit of an acquired taste for many people.

I did have one moment where I thought I'd done some serious damage to the controller (housed neatly in the base of the HL cradle). As I was screwing on the cradle to the mounts the screwdriver touched the middle two pins where the battery connects. I jumped as there was a loud spark, but no power was connected anywhere. I'm wondering if I just discharged some capacitors in a non-standard way. But those pins are very close to the mount hole and screwdrivers are usually made of metal. So I don't know what really happened. But everything was fine when I immediately tested it, but I was somewhat concerned for a minute there.

There are some other mods I've done on my B75 such as the black Joseph Kuosac bar (600mm) retaining standard height. Really feels more comfy with the ergonomic grips and wider stance. I also tried to go further with my own "black edition" by robbing the crank off a spares bike. It still keeps 44 tooth drive as standard with 48 on the outside acting as a guard. However, the 96 link B75 chain won't fit that outer ring with the 15 tooth sprocket I added a while back.

I've only completed a huge 8 miles so far (well more really as the display only shows assisted mileage completed) but I have to say I love the quietness of this C70 motor. You can hear it on quiet stretched of road of course, but I like that reassuring hum. And it's so much quicker off the mark than my MTB is... obviously the small diameter wheels helping there. I'm very pleased with the power. I'm not a fast rider by any means. I'm losing my bottle a bit when I hit 25 mph downhill :p So for me reaching 12-14 mph on the flat is quite enough. And I managed that easily in the short ride I've done and kept the motor on level 3 of the power range (1-5).

I might need to up the gearing a bit now though. As mentioned earlier, I fitted a 15 tooth sprocket some time ago to help reduce the gearing a bit. Given the 44 tooth chainring (which is standard on the B75) I find the gearing a little low. I was in top gear for most of the ride. I suppose I could just put back the 13 tooth sprocket and put it back to bog standard. I do prefer to cruise in 3rd gear as like I said, I'm not fast anyway.

Of course the bike has added weight now and I found I had to keep the battery locked at all times. On my MTB the battery just sits there (unlocked) with no issues at a 45 degree angle. Obviously jumping vertically up on my B75 is easier to dislodge the battery, added to the more bumps you'll feel on a Brompton. But overall the loaded bike with battery is still a lot less than my Cube MTB. I don't need the full fold unless I'm loading into a car for my summer camping trips to classic car shows. The 1/3 fold you see here is what I usually do when parking indoors in my hallway. What does a B75 weigh? Is it 12.5 kgs? So add a C70 and 17AH HL battery and that's the full weight now.

I will update this as I add more miles and trek a bit further afield. Service from Woosh was very good and they were helpful with the questions I had beforehand. I'm not envisaging any problems with this kit though. This battery is over two years old and so far has clocked up just short of 3000 assisted miles already on my MTB.

EDIT: The full fold is no problem at all by the way. I would remove the battery first if I was fully folding, but it can be done in situ. I just had to be careful how I routed and cable tied the cables as I didn't get it right first time! Or second... but with careful checking of the fold after each repositioning I got the perfect set up.
 

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DBrown67

Pedelecer
Feb 26, 2017
77
27
57
Leeds
Swapped the 15T sprocket for the original 13T and swapped back to the original Brompton crank with 44T chainwheel. So it's back to bog standard B75 spec. Rides much better now. I can cruise steadily on the flat at 10-12 mph in 2nd gear with a reasonably high cadence. I realise this would be too slow for most. In top gear I spin out at 21 mph on a downhill but as I say, 25 is tops for me usually. I suppose I could tweak the gearing up a touch more but next official Brompton jump is to go with 50T chainring which is the standard for all bikes other than B75. I'm wondering if that would a bit more than a tweak though. I don't want to make 3rd too high for me to use. I could combine 50 or 52T ring with the 15T sprocket. A lot of messing about with suck it and see. I'd need a new chain anyway as the B75 is only 96 links.

I managed 35 miles on the odometer at level 3 power from a full charge. However, again please bear in mind mine is a two year old battery with nigh on 3K on the clock already. So as those are 35 assisted miles I reckon I've covered over 45 miles in reality. I should use a GPS phone app next time to see how much I truly cover. I noticed the power cut out on me when I'd reached the 35 mile mark so there was obviously some power left as I instantly noticed the difference when it cut out. But that might be pre-programmed to stop the battery draining too low, but I'm no expert on that.

I want to try power level 2 next as level 3 was easily enough for me in the mixed terrain I covered. I think I only used 1st gear once on a steep climb and that wasn't a road anyway. All other climbs on roads near me were handled in 2nd gear no problem. When the battery cut out I had to cycle the last few miles home on leg power in 1st gear. So if I tweak the gearing up much more it might become unrideable for me without battery power. I remember test riding a 50/13 M3L model from Evans and I found it awful. Far too high geared. For now I'll stick to what it is, as those chainrings aren't cheap if then find out I liked it as it was before. :p
 
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Warwick2

Pedelecer
Mar 19, 2021
74
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I've just (almost) completed my conversion of an M3L, but not without issues.

The kit arrived promptly and it was a simple task to swap the Schwalbe Marathon Racer over to the Woosh wheel which, refreshingly, came with rim tape.

The first hurdle was the supplied bolts to fit the battery mount to the frame. The Woosh ones were at least 1cm too long. Easily solved, as I used the Brompton ones.

The rest of the kit - bar the pedal sensor - was easy to fit as well. The issue with the pedal sensor was that Superman works at Brompton and had tightened the cranks onto my bike! Not Woosh's fault, of course. I'd almost resigned myself to getting it to my LBS, but decided to spray some WD40 into the tapers and to lie the bike in the midday sun to cook. After some swearing, it loosened. The plastic axle cup also put up a fight going back on, but went back eventually.

I've powered it up and had a short test drive and initial impressions are good. I'll give more feedback once the weather's cooled down and I've used it more. The cables need tidying up and that'll be trial and error.

If Woosh are reading this, I'd gladly sacrifice the rim tape to gain a controller case. That feels like a significant omission to me.
 
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Warwick2

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Mar 19, 2021
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I've had a 6-mile ride today. Initially the magnet disc was slightly too far from the sensor. A quick adjustment closed the gap enough for power delivery to feed in smoothly. Hill climbing was easy, despite only having three gears. I've fitted some stick-on pads, as my weekend test ride revealed that the battery rattles in its mount.

I'm pleased so far, but I'll need a longer ride to get a better idea...
 
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Warwick2

Pedelecer
Mar 19, 2021
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I took the bike out on a short trip to the nearest village this morning and it performed well. I managed to tuck the battery terminals into the waterproof case, which was just as well, seeing as it rained.

It pulls nicely up to the 15.5mph limit, although the Brompton's gearing is limited to 3 speeds. On the flat 3rd gear was fine at power level 4. Uphill and I switched to 2nd and level 5. I should add that I've been out of the saddle most of the year, so my fitness level isn't the highest.

My last bike was a Cube Kathmandu Pro with a powerful Bosch set up, and it wouldn't be fair to compare the two bikes, but the Brompton will fit a purpose I envisage for it on a dual-mode commute.

The battery still rattles, not as much mind, but I'll investigate some options to stop it. I think it happens because it's mounted vertically, but designed to lie flat.

Anyway, I've ended up with an electric Brompton for less than half the price of a factory one, so I'm impressed thus far.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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It pulls nicely up to the 15.5mph limit
Can you please clarify? The Brompton I built that had more or less the same motor pulled strongly to about 12.5 mph after which there was a straight ramp down to zero power at about 15 mph. In other words, you could hear the motor whirring at 14 mph, but there wasn't much power.
 

Warwick2

Pedelecer
Mar 19, 2021
74
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Not sure what else I can clarify. The power feed in is quite a kick in level 5 from a standstill, as expected, but it delivers power all the way up to 15-16mph then drops out.
 

Warwick2

Pedelecer
Mar 19, 2021
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The English isn't the best in that manual. If I've read it right, you can set it up to have up to 10 power levels (0-9) and customise the power delivered at each level. That would be nice to have if I've read it correctly.

It also mentions a Slow Start parameter. What's that all about?
 

Woosh

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May 19, 2012
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Warwick2

Pedelecer
Mar 19, 2021
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Thanks for the manual link. I now have 10 power levels, starting from zero, then 20% power in level 1 up to 100% in level 9 with 10% steps in between. I'll see how that feels on the road. With just the 3 gears on the Brompton I'm hoping that I can tune my cadence using the power levels, cutting down on the need to change gear as often.
 

Warwick2

Pedelecer
Mar 19, 2021
74
20
I took it out for its first serious ride this morning. It couldn't have been a better/worse test for the set up, as it was heavy drizzle and cool. I tucked the power terminals into the pouch I rigged up and got ready to head out, with some trepidation.

I needn't have worried, as overall the bike/C70 combination worked very well. The 10 power settings also worked well, but I need to tweak the power levels so that the gaps between the upper seven levels are reduced. I found I could use the different power levels to avoid gear changes a lot of the time.

Despite the weight of the motor and the battery, the front end is still a little skittish on looser surfaces, such as the bridlepath I used. On the road it was fine, and the mile-long climb into Harbury was done with aplomb, although I had to drop into first gear.

The rain had no effect on the electrics, which was reassuring, as I intend to use the bike on a commute that involves a 7-mile journey to Leamington Station, a hop on the train to Kenilworth, then a 3-4-mile stretch to work.

My ride today of c.20 miles left 3 bars on the power meter, but - in common with other bar meters - that could be 59% or it could be 41%. A percentage reading would be so much better, but that's no reflection on Woosh, more the manufacturers.

After that ride, I'm still impressed. I'd like to have a ride on a factory electric Brompton to compare them, but I have some feedback that Woosh might like to consider:

1) The battery mount bolts that Woosh supplied are far too long, I reused the Brompton mount ones, but they are also too long (because the Brompton mount has a recess) meaning that the battery mount currently sits a few millimetres further out from the frame than necessary. This is putting undue strain/leverage on the mount. The instructions refer to the correct, shorter bolts, and this can cause confusion when assembling the kit on the bike. I did write to Woosh and they got back to me to say they didn't have any of the correct bolts in stock, but would order some if I wanted. Sorry, but that's not right, Woosh; I needed the correct bolts when assembling the set up and you really should have some in stock.

2) The battery works well, but I suspect it wasn't intended to be mounted as Woosh are doing. It rattles annoyingly, even after I've stuck some pads onto the mount. I need to source some thicker padding to eliminate the rattling. Woosh should take a look at the issue and see if they can add some padding to the mount or the battery so that the fit is good from the start.

3) Woosh should supply a controller bag with their kit, IMHO. They don't cost much and having one that allows the cables to enter it at the bottom instead of through the zip(s) would go a long way to eliminating water ingress. They do include a rim tape, but there is already one on the Brompton front wheel that can be reused. Skip the rim tape and supply a bag would be my advice.

I'll be tough and give the kit 7.5/10, but if the above issues are addressed, and the kit works long-term as well as it did today, I'd be looking at 9+/10.
 

vfr400

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Jun 12, 2011
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Woosh, can you confirm the motor max RPM or Kv? Normally, they're 328 rpm for a 16" wheel, which wouldn't give full power to 15 mph.
 

Woosh

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May 19, 2012
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328 rpm.
The Brompton tyre's circumference is 1.3m.
Best speed: 1.3 * 328 * 60 m/s = 25,584m/s = 15mph.
 

vfr400

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Jun 12, 2011
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328 rpm.
The Brompton tyre's circumference is 1.3m.
Best speed: 1.3 * 328 * 60 m/s = 25,584m/s = 15mph.
328 rpm in a 16" wheel is the same as a 201 rpm in a 26" wheel. 201 rpm is too slow to maintain 15 mph in a 26" wheel, which is why nearly all manufacturers, including you IIRC, use 240 - 260 rpm motors in their 15.5 mph restricted bikes with 26" wheels. 240 rpm still gives good power at 15 mph, but 201 rpm has passed its peak. It'll assist to 15 mph, but there's not enough power to keep it there. That's with a fairly well charged battery. When the battery is run down, it's obviously 20% slower.
 

Woosh

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May 19, 2012
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I have no trouble maintaining 15mph on my Brompton. You only need about 200W to maintain 15mph on an average bike, on flatish roads. If the rider puts in an average 70W, the motor can supply the balance 130W. Any kit can do that.
 
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vfr400

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Jun 12, 2011
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I have no trouble maintaining 15mph on my Brompton. You only need about 200W to maintain 15mph on an average bike, on flatish roads. If the rider puts in an average 70W, the motor can supply the balance 130W. Any kit can do that.
Yes, I can maintain 15 mph on a flat roaad on a bike without a motor. The question is more about what the motor can do.
 

Woosh

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it's sensible to optimise the motor for 15mph.
 

vfr400

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Jun 12, 2011
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it's sensible to optimise the motor for 15mph.
Which is why you use faster motors on all your other bikes. Their equivalent speed on a Brompton would be around 420 RPM, but there aren't many motors that spin that fast, though you'd be spot on if you ran your 328rpm one at 48v.

Personally, I thought 328 rpm was about right for a Brompton, which is not the sort of bike I'd want for fast commuting anyway. 328 rpm gives a heavier rider good power up to about 12 or 13 mph. I could definitely feeel the power dropping off after that. Maybe it's not so obvious for lighter riders.

Rider weight makes a massive difference. The right power for a 75kg rider would be 50% too much for a 50 kg rider and only 75% of what a 100kg rider would need, so it makes a big difference who's judging, like the guy who said his Gtech bike flew up hills without saying what type of hills and how heavy he was. My experience of that bike was that the steep hills that I encounter were impossible on it because without gears it wasn't possible to help the motor when you slowed down on them. It was like the cranks were locked. Pushing was the only option on hills that I could get up on bikes without motors.
 
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Warwick2

Pedelecer
Mar 19, 2021
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I now have 10 power levels, starting from zero, then 20% power in level 1 up to 100% in level 9 with 10% steps in between. I'll see how that feels on the road. With just the 3 gears on the Brompton I'm hoping that I can tune my cadence using the power levels, cutting down on the need to change gear as often.
I've tweaked the power percentages for the nine powered levels to 40, 48, 56, 64, 72, 80, 87, 93 & 100% and all seems to be good. Switching between power levels is easier than changing gear.
 
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