eBrompton Build

DBrown67

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Feb 26, 2017
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Just got the 10ah battery fixed to the stem of my Brompton last night. Used 2x large jubilee clips with some rubber where metal meets painted stem. Very solid and was fine on commute this morning. Doesn't look particularly elegant, but does the job. I weighed the battery/controller in bag at work yesterday, and it comes in at 2.1 Kgs, so too heavy for you. But it is noticeably lighter and more compact than the 17ah HL that got nicked. When carrying the bike I find it much easier to just tuck the back wheel under and then lift the saddle onto my shoulder and rest it there while supporting the rear wheel. More comfy and easier so long as not in confined spaces.

I'm definitely going to get a rack though, and go with the Omni wheels you posted link to. Can get those same wheels on ebay. Bit more expensive ofc at about £40 a pair, but much quicker shipping time as coming from a UK depot.

Interesting reading about tyres. I have Marathon Plus on mine and they have been great for resisting punctures. But I have had issues fitting them and taking them off etc. Maybe it's my technique but I found that where the rubber meets the wire can get split and then it's game over. New tyre needed. This has happened three times, once through a badly aligned brake block (I need to get the newer black caliper for my B75 with the extended drop). Can get these Plus tyres from Halfords website now at £27 each with free shipping. Must have just gone up £2 as I got them recently for £25 each.

However I find that the tread wears very quickly on the front tyre. I will get some pics up later. The current tyres have not been on that long... not new but not old either. And the tread has worn completely in the centre of the front tyre. Comparison to rear is night and day. I even had one fitted before that wore through to the proctective lining. Still didn't puncture though. Of course all the weight is on the front on a leccy Brompton, which causes this, but the wear is concerning.

It was interesting to note in that video review you posted that the Continental logo had't even worn off on the ones he'd had fitted for two years. Of course it's mileage that counts, not time, but that did look much better than the wear on mine.

Would be interesting to see if Woosh could confirm if these folding Continentals can be fitted to their front motor wheel without issues.
 
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Woosh

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The rim we use is identical to the original Brompton 's
 
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StuartsProjects

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Would be interesting to see if Woosh could confirm if these folding Continentals can be fitted to their front motor wheel without issues.
The Continental Contact Urban is specifically designed for Brompton rims.

A folder could be a good choice for a starter, if you dont like it as least you have a fairly light tyre to carry as a spare. Given the significant increase I have seen in real bad potholes the chances of ripping a tyre are increasing.

Warning: To change a tyre you need to take the wheel off and put it back on.
 

DBrown67

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Feb 26, 2017
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Well first day with the new kit... and sods law dictates I get a puncture on the way home. Not a normal puncture though. The MPlus tyre did not fail. It was an old tube repair that failed from a time before I fitted the Plus.

But regarding the wear of Plus these are pics I took this morning... see the comparison of front to rear. I will deffo try a folding Continental next time. Something toak a chunk out of the front as can be seen. But tyre did not fail.
 

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saneagle

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When you put a motor in a front small wheel, it wears the tyre very fast because it can't get traction like a rear one does. MPs are quite hard rubber, so they get less traction than some other tyres, but the wear rate is low. You'll probably get more grip with some other tyres, but don't expect longer life.

Did you experience your front wheel spinning on steep hills?
 

DBrown67

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Feb 26, 2017
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When you put a motor in a front small wheel, it wears the tyre very fast because it can't get traction like a rear one does. MPs are quite hard rubber, so they get less traction than some other tyres, but the wear rate is low. You'll probably get more grip with some other tyres, but don't expect longer life.

Did you experience your front wheel spinning on steep hills?
No. I never feel it spinning. I have felt it on the odd, rare occasion I was off road, so I know when it happens and it's very noticeable. But never felt it on road. I put the extra wear down to the fact all the weight is at the front and steering on road causing it. Or perhaps allowing the tyre to run slightly underinflated, but I learned my lesson on that and keep these topped up weekly/fortnightly at 100psi.

I was impressed with the Continental in the video linked earlier, due to the logo embedded in the rubber not being worn out after 1000s of miles. Now he doesn't have the weight at front that I do, because his isn't an eBrompton. But he's doing far, far higher mileage than I am.
 
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StuartsProjects

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10S1P 21700 battery arrives

So finally the battery made from 10 x Samsung INR21700-50S, 5Ahr arrived. Its small, 125mm x 78mm x 45mm and light at 826g. See picture alongside one of the batteries from my eMountain bike;


52500

But is it good enough ?

So I went for a trip, much longer than my normal shopping trips. The route was mainly flat on cycle paths and quiet roads. I went to the barrage in Cardiff bay, called in to see someone on the way back and popped into One-Stop to get some beers and returned home.

I was not hanging about doing 14mph mostly on assist level 1. There was actually quite a bit of assistance at that speed, I was not putting in a lot of effort. Total distance was 15 miles and I had about 25% battery left when I got home. Toward the end of the journey there is a 450m long hill and I went up that throttle only, battery voltage did sag down to 34V or so.

Ebrompton does have gears, 2 speed at the moment but will be upgraded to 3 speed. I don’t normally use the gears on eBrompton in electric mode, the motor gives you the assistance needed on hills. You could argue that if the gears are not used then why not remove them and save more weight. Problem with that is that if the battery goes flat or the electrics fail then the gears are real handy for getting you home. Of course with a Brompton you could also just jump on a bus or train or call a taxi to get home.

The purpose behind eBrompton was to provide a light eBike that I could use for mostly local trips to shops, bank, doctor etc. Bromptons even in their basic form are not low cost and its not the sort of bike I would risk leaving locked up somewhere as you wander around town shopping. So I take it with me but for that to work it has to be light, easy to fold and easy to wheel around when folded.

If I want to go on longer trips or on off road tracks I would take my eMountain bike, that has a 17Ahr battery better tyres and front suspension. But its about twice as heavy as eBrompton and nowhere near so easy to get on and off.

I measured some of the typical trips I would use eBrompton for and the round trip distances were;

Bank and centre of town, 6.25 miles.
Doctor, 2 miles.
Tesco 2 miles.
Sainsburys click and collect, 6.6 miles

So most all of the trips I would do on eBrompton will use no more than around 33% of the battery capacity.

At this point I have a dilemma, the 10S1P is good enough for the intended purpose, but would a 10S2P of good quality 18650 and 7Ahr be better ? Such a battery would be maybe 250g or so heavier and a bit bigger at about 151mm x 106mm x 67mm, but it should provide more range and\or offer the potential for higher assistance levels.

Choices, choices.
 

Woosh

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At this point I have a dilemma, the 10S1P is good enough for the intended purpose, but would a 10S2P of good quality 18650 and 7Ahr be better ? Such a battery would be maybe 250g or so heavier and a bit bigger at about 151mm x 106mm x 67mm, but it should provide more range and\or offer the potential for higher assistance levels.
I had similar consideration a couple of years ago. I rode my Brompton with a Bosch 36V tool battery for a year then went for 10S2P with 27100 cells, 36V 10AH. It's a perfect compromise for keeping the folding mechanism like it is, weight, range, hill climbing and charging frequency.


 

StuartsProjects

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I had similar consideration a couple of years ago. I rode my Brompton with a Bosch 36V tool battery for a year then went for 10S2P with 27100 cells, 36V 10AH. It's a perfect compromise for keeping the folding mechanism like it is, weight, range, hill climbing and charging frequency.
Whilst the 10S1P seems to be good enough, and would go in a smaller bag, which will eventually be mounted on the front bag block, it would be incredibly useful to have the option of having a physically bigger battery.

I have a small bag that the 10S1P will probably fit in with the controller, but its quite a bit of work to strengthen the bag with a plate, cut holes, fit it to the bag block, etc.

A larger bag would probably be the same amount of work, but the option would be there for better\bigger batteries.

The bag on the Brompton shown, can you buy them, and if so what is the size ?

I can see Wildman hardshell cycle bags on eBay, 22 x 8.5 x 8 cm , that the one ?
 

Woosh

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It's a standard 1.7L, I bought on Amazon. It holds the controller as well. There is already a hole at the bottom for the cables. You can see how simple the wiring is, one goes to the LCD, one to the PAS and one to the motor.
 
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StuartsProjects

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It's a standard 1.7L, I bought on Amazon. It holds the controller as well. There is already a hole at the bottom for the cables. You can see how simple the wiring is, one goes to the LCD, one to the PAS and one to the motor.
It looks like this one maybe, the length is correct and it claims to be 1.5L;

52521

I can see that a 10S1P of 21700 would fit, but it looks tight for a 10S2P of 21700 ?

The Samsung 21700 50S seems to be in a sweet spot as far as small batteries for eBikes is concerned, its 5Ahr and rated at 25A max continuous. Having used the 10S1P battery on a few hills now, its OK, but I would not be keen to drop the battery max current capability, you would expect more voltage sag under load on hills.

You can goto a 10S2P of 18650 which is not physically that big, but the cells at 3.5Ahr have a max current of 10A, so a pair of these has a lower max current than the single Samsung 21700 50S.

You can also have a 10S2P of 18650 Molicell P28A, a small increase in capacity to 5.6Ahr and a 50A max current for a 200g increase in weight, might be worth a punt.

I have extended the leads on one of those el-cheapo '200A' power meters and the load current climbing up a reasonable hill assist 5 and max throttle is circa 15.5A, so the controller is maxing out.
 

Woosh

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I use the 1.5L on my bike but Andy found it's too tight so he uses 1.7L for customers.
 

DBrown67

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Feb 26, 2017
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That is the exact battery/bag I bought from Woosh recently. Came in at 2.1 kgs on the digital scale. I used large jubilee clips to securely fix the bag to the stem with rubber protection pads. As mentioned earlier, not a good look, but it stops the battery swinging side to side which it will inevitably do using the velcro straps. I have the charging socket poking out of the zip, so no fiddling about. I just charge in situ at home in the hallway.

I lock my bike at work with a good DLock, but its a secure school ground with covered cycle rack. I've learned my lesson about leaving it locked in public after last battery got nicked. From now on (apart from work) it goes where I go.
 

StuartsProjects

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I have my battery\controller in a handlebar\stem bag at the moment.

But it makes shopping trolley mode a bit unstable, so their will (I hope) eventually be a bag on the front bag block.
 
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StuartsProjects

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But it makes shopping trolley mode a bit unstable, so their will (I hope) eventually be a bag on the front bag block.
Non-Brompton users may not appreciate the issue here.

With the controller\battery in a rear facing bag on the handlebar steering tube, when folded the battery\controller bag is on the very right outside edge of the folded Brompton. The battery is relativly heavy so the narrow wheelbase folded Brompton in trolley mode can tip over towards the right.

With the battery\controller bag on the Brompton block facing forward , when folded the bag is in the middle of the folded Brompton, more stable.
 

Woosh

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With the battery\controller bag on the Brompton block facing forward , when folded the bag is in the middle of the folded Brompton, more stable.
agreed. However, in practice the reason you would fold the bike is to stowe it away so would you move it folded for more than a few seconds?
 

Woosh

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As mentioned earlier, not a good look, but it stops the battery swinging side to side which it will inevitably do using the velcro straps.
I cabletie the top of the bag to the handlebars bolt at the top of the stem to stop the swinging from side to side. The large width of the plastic cabletie gives the bag a stabilising effect.
 

StuartsProjects

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Pushing it folded under a table with the handlebar steering stem bag is not a problem.

But I am a keen advocate of shoping trolley mode, its not a bike I would not want to leave it locked up outside.

So far it has accompanied me around Sainsburys, Tesco and Aldi.
 
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Woosh

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But I am a keen advocate of shoping trolley mode, its not a bike I would not want to leave it locked up outside.

So far it has accompanied me around Sainsburys, Tesco and Aldi.
but you wouldn't have to fold the stem when pushing your Brompton though?