eBrompton Build
- Thread starter StuartsProjects
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Going to try the kit as supplied first, but I already have an in-line sensor ready to fit to the lighter Aceoffix levers.
Aceoffix brake lever + inline sensor = 48g
Kit supplied brake lever with sensor = 112g
The PAS
The supplied two part PAS disc does fit on the left crank. The gap between the small curved frame tube that forms part of the triangle by the bottom bracket and the inner surface of the PAS disk is 31mm. The PAS sensor itself is 19mm high when level on the adjustable bracket and can extend to 25mm. So I cut a short bit of 10mm square hardwood, put a bit of sandpaper over the Brompton frame tube and sanded a curve on one side of the bit of wood.
Secured in place with a couple of zip ties the fitted PAS looks like this;
I might later remove the adjustable bracket and add a bit of wood as a spacer.
I was impressed with myself for finding such a simple setup for adding a PAS to eBrompton until I realised the obvious problem. Whilst that position for the PAS was easy to setup, the cable entry is pointing upwards in a please let water in mode.
Another possible issue is that the PAS sensor is a bit vulnerable to getting kicked in that position. An alternative position, where the PAS would be difficult to dislodge is position A on the picture, but that might mean modifying the sensor, which is the opposite approach if you want a quick and easy repair setup.
Motor Wheel Tyres
I had ordered a Continental Contact Urban tyre to try and when it arrived I put it on the front wheel of the non-Electric Brompton and went for a ride. Good tyres, less rolling resistance than a Marathon plus, but lighter by 200g (each!) and apparently with a similar puncture resistance. Lots of good reports about the tyre, they only cost about £16 and easy to fit.
So good for the eBrompton motor wheel I thought, but I was disappointed, they wont stay on the motor wheel rim, when the tyre gets up to pressure it tries to escape the rim, see picture.
On a close look the motor wheel rims do not look the same as standard Brompton rims, a different internal shape and narrower, 16mm versus 17.5mm.
Ah well back to the Schwalbe Racers.
Next: Do I have a battery ?
The supplied two part PAS disc does fit on the left crank. The gap between the small curved frame tube that forms part of the triangle by the bottom bracket and the inner surface of the PAS disk is 31mm. The PAS sensor itself is 19mm high when level on the adjustable bracket and can extend to 25mm. So I cut a short bit of 10mm square hardwood, put a bit of sandpaper over the Brompton frame tube and sanded a curve on one side of the bit of wood.
Secured in place with a couple of zip ties the fitted PAS looks like this;
I might later remove the adjustable bracket and add a bit of wood as a spacer.
I was impressed with myself for finding such a simple setup for adding a PAS to eBrompton until I realised the obvious problem. Whilst that position for the PAS was easy to setup, the cable entry is pointing upwards in a please let water in mode.
Another possible issue is that the PAS sensor is a bit vulnerable to getting kicked in that position. An alternative position, where the PAS would be difficult to dislodge is position A on the picture, but that might mean modifying the sensor, which is the opposite approach if you want a quick and easy repair setup.
Motor Wheel Tyres
I had ordered a Continental Contact Urban tyre to try and when it arrived I put it on the front wheel of the non-Electric Brompton and went for a ride. Good tyres, less rolling resistance than a Marathon plus, but lighter by 200g (each!) and apparently with a similar puncture resistance. Lots of good reports about the tyre, they only cost about £16 and easy to fit.
So good for the eBrompton motor wheel I thought, but I was disappointed, they wont stay on the motor wheel rim, when the tyre gets up to pressure it tries to escape the rim, see picture.
On a close look the motor wheel rims do not look the same as standard Brompton rims, a different internal shape and narrower, 16mm versus 17.5mm.
Ah well back to the Schwalbe Racers.
Next: Do I have a battery ?
Shame those didn't work out. Finding the right rims for the tyres I want to use on my 20" folder is bloody difficult - merchants on AliExpress hardly ever list all rim dimensions, and their tyre fit claims are lies, according to Schwalbe's charts. Had to buy Tern wheels in the end...
Here are pictures of a standard Brompton rim (first picture) and the supplied motor wheel rim (second picture)
You can see the differences.
Do I have a battery ?
I have been trying to get a custom battery built using a 10S1P pack of Samsung INR21700 40T or SAMSUNG INR21700 50S. Accepted that its a bit of an unknown as to how much the voltage sag under load will affect performance, but I think its worth a try. A 4Ahr or 5Ahr is enough for what I want and its a lot lighter than a 10S2P. However its been suggested by the battery builder that for the custom build a 5Ahr based on the 50S should be used, and they are not due in stock until the end of May.
So I need a battery to carry on with the build and should be able to borrow a 10S2P using Samsung cells in a 10S2P setup. This battery is from a hover board and checking on eBay these batteries are not expensive, about £65, so maybe too cheap to be safe. Anyway for now I only want to use it to check the conversion kit functions. From the times when I did a lot of flying of radio control models I have several of the fire proof storage bags, so I can put the battery in one of those.
You can see the differences.
Do I have a battery ?
I have been trying to get a custom battery built using a 10S1P pack of Samsung INR21700 40T or SAMSUNG INR21700 50S. Accepted that its a bit of an unknown as to how much the voltage sag under load will affect performance, but I think its worth a try. A 4Ahr or 5Ahr is enough for what I want and its a lot lighter than a 10S2P. However its been suggested by the battery builder that for the custom build a 5Ahr based on the 50S should be used, and they are not due in stock until the end of May.
So I need a battery to carry on with the build and should be able to borrow a 10S2P using Samsung cells in a 10S2P setup. This battery is from a hover board and checking on eBay these batteries are not expensive, about £65, so maybe too cheap to be safe. Anyway for now I only want to use it to check the conversion kit functions. From the times when I did a lot of flying of radio control models I have several of the fire proof storage bags, so I can put the battery in one of those.
They are nice tyres.
When eBrompton is finished, I intend to remove the Swytch electric kit from my old Brompton, so I have a much lighter bike for local stuff that will force a bit more exersize. The tyres on that are Marathon plus, the Continentals do run better, slightly narrower and lighter. The Marathons are around 3 years old and as there is someone on eBay selling the Continentals for £17, I ordered some to replace the Marathons.
I think you'll find that it's the rim's diameter that's different. Some tyres don't like to be re-fitted, especially if you have a bad technique and use unnecessary force to lever them over the rims, which can stretch the wire in the bead.
If those tyres are safe on those rims.... and I'm probably telling a granny how to shuck eggs but... did you use diluted washing up liquid so they slither about on the rims easily; make sure the tyres hooked in all the way around, when partly inflated?
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The rim is circa 2mm less diameter.
The Continentals are easy to fit by hand, no levers needed, so no 'unnecessary force' needed either.
Big weight saving if you can find high quality rims! With Firefox, it's easy to disable CSS on AliExpress to look closely at photos posted by reviewers, otherwise only shrunk photos are displayed, and burrs etc. can be seen. So far, I haven't found any there I'd buy for my bike. I wouldn't be surprised if a lot of third party rims were splayed in places.
I dont use washing up liquid, but for sure I make sure the tyre bead is pushed down and hooked in all the way round.
Not a Granny, but I have been for 50+ years fitting tyres to cycles such as Moulton, Raliegh RSW 16, Bikerton and for the last 20 years a Brompton.
I will give it another go when the new Continentals arrive, but it does appear to be a black and white issue, the Continental tyre fits well in the normal straight forward way on a Brompton rim but if voodoo and special chants are needed in a workshop to fit the tyre on the smaller motor wheel rim its a non-starter going out for a ride on it, just in case you do get a puncture.
Sometimes I'm happy being a satanist, as making pentagrams using salt aound the bike, is much more convenient than carrying live chickens to sacrifice for voodoo... but rum is good, the requisite mumbling for either must be easier to do when drunk.
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Putting it all together – the first time
I first needed to connect the conversion kit bits together to check it all works. Once I have done that, and given the bike a test ride, I can review and test the battery options and then can I finally work out which bag to use to store the battery controller and cables.
The conversion kit had a handle bar bag designated for the install and it could take a 10Ahr or 15Ahr battery, the bag itself weighed 182g. Using this bag and the kit as is would be the heaviest option.
I put the bag on the handlebars, facing backwards so the Brompton would fold.
I had got hold of a hover board battery, which was 10S2P of 18650 inside the plastic, supposedly fireproof case they use, for testing the setup and it should be representative of the weight of a 10S2P of 18650 battery made of quality cells that would have a capacity of up to 6.7Ahr. I put thehover board battery in the handlebar bag.
I added the controller to the bag, plugged in the 1 to 4 cable and the display, the throttle, connected up the motor wheel and turned eBrompton on. It powered up OK so I checked the wheel size was 16” and set it for mph. The wheel did spin the right way using the throttle as a tester so I plugged in the PAS and rotating the cranks did make the front wheel go.
I tidied up the cables, with all the cable slack being coiled up inside the bag. I then went for a ride.
It performs much the same as my Swytch Brompton. Only having two gears was not a problem, with the electric assist you can stay in one gear most of the time. Maybe the high gear could go up a bit, possibly change the front chain ring from 47 to 50 or 52, something to look at later.
The total weight this working eBrompton was 11.8Kg.
So that looks promising, a better quality battery which would be smaller and lighter would need a smaller lighter bag. Then tiding up the cables and getting rid of all the slack will save a bit, so the finished weight should creep under 11.5Kg, or 10.75Kg plus battery.
Who needs Titanium ?
The stem catcher is what holds the handlebars in place when the Brompton is folded, a knob on the steer tube fits inside the catcher.
When I bought the bike, the standard Brompton stem catcher had been replaced with a H&H Titanium stem catcher. They cost around £30+.
However it did not really hold the handlebars firm enough, so I gave the arms a little squeeze, like you do. The catcher snapped, oh dear.
So I put the standard Brompton stem catcher on and the weight of the bike increased by a massive 16g, not good enough. So I ordered an Aluminium one costing as much as £6.25 from China. Fits just fine, hold the bars very securely. Its lighter that the titanium one.
I first needed to connect the conversion kit bits together to check it all works. Once I have done that, and given the bike a test ride, I can review and test the battery options and then can I finally work out which bag to use to store the battery controller and cables.
The conversion kit had a handle bar bag designated for the install and it could take a 10Ahr or 15Ahr battery, the bag itself weighed 182g. Using this bag and the kit as is would be the heaviest option.
I put the bag on the handlebars, facing backwards so the Brompton would fold.
I had got hold of a hover board battery, which was 10S2P of 18650 inside the plastic, supposedly fireproof case they use, for testing the setup and it should be representative of the weight of a 10S2P of 18650 battery made of quality cells that would have a capacity of up to 6.7Ahr. I put thehover board battery in the handlebar bag.
I added the controller to the bag, plugged in the 1 to 4 cable and the display, the throttle, connected up the motor wheel and turned eBrompton on. It powered up OK so I checked the wheel size was 16” and set it for mph. The wheel did spin the right way using the throttle as a tester so I plugged in the PAS and rotating the cranks did make the front wheel go.
I tidied up the cables, with all the cable slack being coiled up inside the bag. I then went for a ride.
It performs much the same as my Swytch Brompton. Only having two gears was not a problem, with the electric assist you can stay in one gear most of the time. Maybe the high gear could go up a bit, possibly change the front chain ring from 47 to 50 or 52, something to look at later.
The total weight this working eBrompton was 11.8Kg.
So that looks promising, a better quality battery which would be smaller and lighter would need a smaller lighter bag. Then tiding up the cables and getting rid of all the slack will save a bit, so the finished weight should creep under 11.5Kg, or 10.75Kg plus battery.
Who needs Titanium ?
The stem catcher is what holds the handlebars in place when the Brompton is folded, a knob on the steer tube fits inside the catcher.
When I bought the bike, the standard Brompton stem catcher had been replaced with a H&H Titanium stem catcher. They cost around £30+.
However it did not really hold the handlebars firm enough, so I gave the arms a little squeeze, like you do. The catcher snapped, oh dear.
So I put the standard Brompton stem catcher on and the weight of the bike increased by a massive 16g, not good enough. So I ordered an Aluminium one costing as much as £6.25 from China. Fits just fine, hold the bars very securely. Its lighter that the titanium one.
Brake levers and sensors
The brake levers with built in switches as supplied with the TOPBIKEKIT could be used.
But for me that would be as a last resort. The conversion kit was only about £5 more expensive with the levers, so I thought they might be useful as spares. What I would much prefer is to keep the Aceoffix levers I had already fitted to the Brompton. The above lever weighs 112g, the Aceoffix levers are 78g lighter.
There are inline brake sensors that fit on the brake cable itself as on the Swytch kits. The 1 to 4 cable has 2 pin red Julet connectors for the brake sensors, so I bought one of the inline sensors with a 2 pin JST-SM plug.
I was not sure how the two wire brake sensors worked so I built some Julet to crocodile clip adapters so I could check. If the brake lever switch was just that, a simple switch, you would expect the resistance measured between the two wires with a multimeter to be the same when the multimeter leads were swapped around. If there was semiconductors involved in the switch\sensor then you would expect the resistance to change when you swapped the leads around.
The resistance across the two wires of the brake lever plug on the TOPBIKEKIT levers when the brake was applied was around 10ohm, and infinity when the brake lever was not active. The readings when the levers were the same when the connections were reversed. This suggests a mechanical switch.
I fitted the in-line 2 wire sensor (with the JST-SM connector on the end) to the front brake lever and carried out the same test. To fit the sensor you just pull back the brake outer at the lever and slip the sensor over the inner, so easy to fit (If they work). The similar 3 pin ones work well on my Swytchified Brompton. The test results suggested the in-line sensor was a mechanical switch also.
I cut the JST-SM connector off the in-line sensor and used one of the Julet to crocodile clip adapters I had made to connect the in-line sensor to the controller and the display did indicate brake when the lever was activated, success. I cut the JST-SM connector off soldered on a 2 pin Julet connector.
I now have a fully working eBrompton at 11.8Kg and there are still weight savings to make. The next decision is what battery to use. If a 10S1P 21700 5Ahr battery proves up to the job, that would be my preferred option, but it is likely going to be a couple of weeks before I get hold of one. The next option would be a 10S2P 18650 6Ahr which would be slightly bigger and heavier.
The brake levers with built in switches as supplied with the TOPBIKEKIT could be used.
But for me that would be as a last resort. The conversion kit was only about £5 more expensive with the levers, so I thought they might be useful as spares. What I would much prefer is to keep the Aceoffix levers I had already fitted to the Brompton. The above lever weighs 112g, the Aceoffix levers are 78g lighter.
There are inline brake sensors that fit on the brake cable itself as on the Swytch kits. The 1 to 4 cable has 2 pin red Julet connectors for the brake sensors, so I bought one of the inline sensors with a 2 pin JST-SM plug.
I was not sure how the two wire brake sensors worked so I built some Julet to crocodile clip adapters so I could check. If the brake lever switch was just that, a simple switch, you would expect the resistance measured between the two wires with a multimeter to be the same when the multimeter leads were swapped around. If there was semiconductors involved in the switch\sensor then you would expect the resistance to change when you swapped the leads around.
The resistance across the two wires of the brake lever plug on the TOPBIKEKIT levers when the brake was applied was around 10ohm, and infinity when the brake lever was not active. The readings when the levers were the same when the connections were reversed. This suggests a mechanical switch.
I fitted the in-line 2 wire sensor (with the JST-SM connector on the end) to the front brake lever and carried out the same test. To fit the sensor you just pull back the brake outer at the lever and slip the sensor over the inner, so easy to fit (If they work). The similar 3 pin ones work well on my Swytchified Brompton. The test results suggested the in-line sensor was a mechanical switch also.
I cut the JST-SM connector off the in-line sensor and used one of the Julet to crocodile clip adapters I had made to connect the in-line sensor to the controller and the display did indicate brake when the lever was activated, success. I cut the JST-SM connector off soldered on a 2 pin Julet connector.
I now have a fully working eBrompton at 11.8Kg and there are still weight savings to make. The next decision is what battery to use. If a 10S1P 21700 5Ahr battery proves up to the job, that would be my preferred option, but it is likely going to be a couple of weeks before I get hold of one. The next option would be a 10S2P 18650 6Ahr which would be slightly bigger and heavier.
That's very light! Do you find that's now light enough for you to easily carry as intended? My Dahon folding conversion with 19.2Ah battery, loads of lights, Oxford side lollipops, horn etc. etc. weighs 22.4kg, and at my current level of health it's luggable up stairs up flights of stairs at train stations, but only if I carry the battery in my rucksack. Do have to stop and catch my breath though. I recall easily springing up those same stairs carrying my racer in the 80's...
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When folded, its definetly much easier to pick up and carry, very definetly. Easy peasy to lift into a car with the battery attached.
When I have the right battery in it, I should be able to move all the battery\controller into a much smaller bag. When that stage is finished I will actually be adding a bit of weight to give it shopping trolley mode, by fitting a much lighter rear rack and decent wheels. Then of course you dont have to carry it so much in the first place.
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If price was no object, and if this "134.1g/138.1g" Titanium + Carbon rear rack even fits?
Ti Parts Workshop Titanium + Carbon Rear Rack for Brompton Bicycle
For Brompton A/C/E Line This rear rack offered the push-ability, fold-ability and stability to the Brompton. It works just the same way as the original rear rack. When unfold, it gives you the sporty and minimal design which featuring the lightest combination of titanium and carbon fiber...
www.fantastic4toys.com
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I did origionally colour the grips and brake cables in appropriate colours, just in case I forgot my right and left, which is important for cycling on the road as you know.
So the right side is Red for right and the left side is Lemon for left.
But I may change the brake cables to black so the electric cables blend in a bit more and are not so obvious.
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