£100 ebike project with mainly new parts

[bonzobanana]

So I won a kit like above from ebay, and that has cost me about £48 delivered and I've ordered a 24V battery and charger from aliexpress for about £30 delivered and I have various donor bikes that can be utilised for this project that cost me from nothing to around £15.

I know brushed motors have a limited lifespan before the brushes need replacing. Early ebikes used brushed motors. I've read this can be about 2,000-3,000 miles depending on how you use the motor. These sort of kits are very popular in India where they have a significant market share. I also understand these kits can be difficult to fit and require a bike that is a good match to the kit. Typically a steel frame bike with a conventional steel frame and ideally a single speed freewheel.

I just wondered if anyone has experience of these kits or perhaps a very early ebike with a brushed motor and has some insights. This is just a novelty project for me, not too serious.

I'm thinking of using a derailleur as a chain tensioner despite being a single speed freewheel so I can use a 3x crankset at the front with a front derailleur to give 3 gears. Do you think this will be possible? I've not seen it done before on such a bike.

I've watched a few youtube videos and generally installation could be problematic but people seem satisfied with performance.

However considering its throttle controlled why does it include brake levers with motor cut off connections. If you move your hand off the throttle to the brake wouldn't that cut off power anyway or is it just a bit quicker?

For those who say it won't be legal because of the throttle please read this;

https://www.pedelecs.co.uk/dft-pedal-cycles-converted-twist-go-exempt-type-approval/

It's perfectly legal for use in the UK (not Europe).

Can anyone remember the brands that did early brushed motor ebikes? I remember seeing a few but for the life of me can't think of the companies that imported them.

Yes the headlight assembly looks awful.

 

[fossyant]

So long as it won't do over 15.5. Good luck.

 

[bonzobanana]

So long as it won't do over 15.5. Good luck.

I think it can do more perhaps 18-20mph tops on a 700c bike but I'm planning to use it on a 26" wheel bike and thinking of replacing the freewheel with a 19T model I have to increase torque and sacrifice some speed. I think this will knock it back to slightly less than 17mph which is the tolerance allowed for legal ebikes 15.5mph plus 10% then allowing for the slightly smaller wheels but thick tyres should bring it down to the correct speed approximately. As you can see from the motor design there is a big gear reduction internally and then a big reduction again in the chain drive. It ends up about 20Nm torque. Some entry level ebikes with geared hub motors are only about 15Nm but then those ebikes would typically have 20" wheels. It's twist and go in theory but pedelec in reality especially for the hills. Definitely not ideal for a e-mountain bike build.

 

[steveindenmark]

I think you already appreciate that its money down the drain. 😁

 

[chris667]

I think you already appreciate that its money down the drain. 😁

No it's not! Splendid few days of tinkering. A happy time engine. Lovely!

 

[sleuthey]

The type of kit you have bought only lends itself towards single speed. If you manage to get gears then be sure to update us.

I'm surprised your considering legal speed when it doesn't meet the other EAPC laws so it will still need insurance, registration etc to use on the road in the UK.

 

[bonzobanana]

I think you already appreciate that its money down the drain. 😁

I don't think so its not like someone who goes into a bicycle showroom and buys a £6K bicycle and has lost £2k just by cycling it away from the store. There are millions of these bikes used in India it seems on a daily basis with the occasional need to replace the brushes which are cheap as chips. I'll grant you its not going to be a prestigious bike though and won't be well received at the sunday cycling club. It's a £100 ebike project and if I sold it there is a real chance I could increase the price that I paid for it.

 

[bonzobanana]

The type of kit you have bought only lends itself towards single speed. If you manage to get gears then be sure to update us.

I'm surprised your considering legal speed when it doesn't meet the other EAPC laws so it will still need insurance, registration etc to use on the road in the UK.

Please see my earlier link. Ebike kits are not treated the same as new complete ebikes. The same ebike sold as new would need special type approval but as a kit it doesn't need that. It's 100% legal if it doesn't assist beyond about 17mph (allowing for the 10% tolerance). Well 100% legal in the UK that is. Even with type approval for a twist and go new ebike you don't need insurance or registration etc.

https://www.pedelecs.co.uk/wisper-announce-dvsa-approved-full-throttle-models/

As for gears I'm going to try to fit a 3x crankset and front derailleur and use a rear derailleur as a chain tensioner and that's how I will attempt gears but it may not be possible if the chainline gets close to the motor chainline. The same sort of motor system can also have gears by alternatively welding a freewheel on the opposite side of rear wheel as long as you don't have disc brakes or alternatively you can get a cog that is bolted around the spokes on the same opposite side so again the freewheel/cassette gears are uneffected. The same sort of thing they did for those 2 stroke petrol engine conversions for bicycles.

 

[sleuthey]

Ebike kits are not treated the same as new complete ebikes. The same ebike sold as new would need special type approval but as a kit it doesn't need that. It's 100% legal if it doesn't assist beyond about 17mph (allowing for the 10% tolerance). Well 100% legal in the UK that is. Even with type approval for a twist and go new ebike you don't need insurance or registration etc.

Yep. That's why I left the throttle on my bike post conversion.

The main requirement I'm referring to is:

Its electric motor:

• should not be able to propel the bike when it’s travelling more than 15.5mph

https://www.gov.uk/electric-bike-rules

So how are you going to meet this requirement? When your doing 20mph down hill your motor will assist when you twist as you do not have Haul Sensors feeding wheel RPM to the controller.

IV nothing against this, I tried fitting this exact kit myself once, the vast majority of ebikes and scooters where I live are not legal. Im just struggling to understand how your claiming your conversion will be a legal EAPC.

 

[bonzobanana]

Yep. That's why I left the throttle on my bike post conversion.

The main requirement I'm referring to is:

Its electric motor:

• should not be able to propel the bike when it’s travelling more than 15.5mph

https://www.gov.uk/electric-bike-rules

So how are you going to meet this requirement? When your doing 20mph down hill your motor will assist when you twist as you do not have Haul Sensors feeding wheel RPM to the controller.

IV nothing against this, I tried fitting this exact kit myself once, the vast majority of ebikes and scooters where I live are not legal. Im just struggling to understand how your claiming your conversion will be a legal EAPC.

Any ebike can do excessive speeds going downhill unassisted. You might be right about technical issues that allow such a kit to go above 15.5mph assisted downhill but there were many early ebikes using brushed motors that were fully legal and still legal to use today. If that is a brushed motor issue then it was accepted but who in their right mind is using the motor downhill. I've gone downhill on non ebikes at something like 42mph on occasion. How do you work out which is doing the work gravity or the motor?

That's one of the strange issues with ebike law. I encountered a heavy legal ebike going downhill as I was walking. It was like 30mph and the bike was heavy and couldn't brake very quickly and was on a shared path and the rider had little consideration for me on the path but the bike was unassisted at the time because it was downhill. Ebikes are often more dangerous to others when the motor is not assisting as they are typically going downhill with a lot more speed and braking takes a lot longer to operate.

Yes I think the kit is fully legal based on its specification. Let's not forget you can buy a mid-drive ebike from a shop that claims to be 250W yet has a controller that peaks around 25A at 36V which is not 250W, used up hill they can be consuming over 600W often over 700W. Everyone knows they aren't 250W but they are allowed. Maybe like the Bosch dieselgate issue there will be a time when the legality of such motors will come under fire. They do strictly adhere to the 15.5mph rule though unless hacked/chipped.

In contrast these brushed motors only have a 1Nm motor approx and the 10:1 gearing takes it up to 10Nm and then the chain drive doubles that to 20Nm. This is continuous at 20Nm not a peak figure though or at least close to its continuous figure so more powerful than many realise as many hub and mid-drive motors give peak figures which they cannot sustain for a long length of time. Also brushed motors have much higher starting torque so give a much better boost from stationary which is probably the only real advantage of brushed motors to be honest. These motors happily work with lead acid batteries as well as lithium ion. Their speed is mechanically restricted not electronically restricted. The motor at maximum rpm is about 20mph on a 700c wheel with a 16T freewheel. Smaller wheels and a larger tooth freewheel will drop that 20mph to a legal speed.

 

[steveindenmark]

I don't think so its not like someone who goes into a bicycle showroom and buys a £6K bicycle and has lost £2k just by cycling it away from the store. There are millions of these bikes used in India it seems on a daily basis with the occasional need to replace the brushes which are cheap as chips. I'll grant you its not going to be a prestigious bike though and won't be well received at the sunday cycling club. It's a £100 ebike project and if I sold it there is a real chance I could increase the price that I paid for it.

Mecback
Well I hope you prove me wrong and come back with the results.