Next electric bike - illegal DIY!?

Jeremy · Apr 8, 2008

I thought about the "illegal" ebike option, in fact I went so far as to try it with the big Crystalyte motor on my 'bent, but concluded that bicycle frames just aren't really designed to take three or four times the power that a rider can deliver.

I have started another electric vehicle project (although keeping my Tongxin powered 'bent) but have decided that it must be completely legal. I have purchased a small motorcycle (actually categorised as a moped) rolling frame and have ordered a motor and controller to convert it to electric (the combined cost of the motor and controller was about £400, comparable to an ebike kit).

I believe that if the electric motor power is kept below 4kW, then it will remain in the moped category (the original engine in this bike was only about 4 or 5hp). I haven't had confirmation of this from the DoT though (despite asking them the question a week or so).

The advantage of doing it this way, apart from remaining legal, is that the frame and rolling gear is working within it's original design limits, which means that the brakes, tyres, frame etc are all up to dealing with the power safely.

Jeremy

joab · Apr 8, 2008

I got the EZEE bike kit from www.ebikes.ca Homepage of the revolution. Speed limit of 32km. I now have more then 1500km and I'm very pleased with it.
See my review for more info:
http://www.pedelecs.co.uk/forum/electric-bike-reviews/1449-ezee-bike-conversion-kit.html

flecc · Apr 8, 2008

fabola said:
Today I own an Salisbury LPX (as the only e-bike experience). It is ok, but too slow and not strong enough (because it's legal!).

Not because it's legal! It's because it's the lowest powered legal bike, that's all.

There's plenty of faster legal machines out there, and many a far better bet than Cyclone or Goldenmotor products. I know of two people who are satisfied at the point of receipt of a Cyclone, but have known of many who are unhappy after owning one for a while, plus dealers in the USA who refuse to supply them any more.

We've had two members buy Goldenmotor, both failed on or straight after receipt and no resolution of the problems ever posted here.

So I've warned, but it's up to you of course. If you do want the illegal route, why not Crystalyte or the Puma motor, both with better records here and UK supply and support?
.

john · Apr 8, 2008

Jeremy said:
but concluded that bicycle frames just aren't really designed to take three or four times the power that a rider can deliver.
Jeremy

I wonder why you concluded that. A competitive cyclist can put out 400+W and travel up to 70mph on a flimsy lightweight frame. A good mountain bike (and rider) can drop 6 feet and more without damage.

BTW, keep meaning to ask you; did you think of limiting your crystalyte with an in-line resistor from the throttle. I have one on my setup so I can switch between legal/performance modes.

Jeremy · Apr 8, 2008

That's a bit like comparing a formula one car with a family saloon, isn't it? How durable would that light weight bike be if ridden every day, in all weathers, over normal roads at that sort of power and speed, I wonder.

Are bike brakes really up to reliably stopping a bike from high speeds (30mph plus), at full weight, in all weathers, on a daily basis?

I suspect that there are some bikes that will take this, like the beefy downhill mountain bikes, for example, but they have frames, wheels, tyres, brakes and suspension that are similar to mopeds in many ways.

The Crystalyte 405 I have runs at around 1100 watts max, nearly three times the power of a really good athlete. It also adds a lot of weight, my 20" front wheel alone weighs about 7kg.

The increase in weight is significant, particularly the added inertia in the wheel. This latter effect seriously upset the handling of the 'bent, which was one of the reasons I switched to the much lighter Tongxin.

Several people on the Endless Sphere forum have run ebikes at well over 30mph, but quite a few have reported that they get scary at very high speeds. It seems more sensible to me to use a base vehicle that is designed to be safe at these speeds and weight.

Jeremy

john · Apr 8, 2008

I'm not trying to put you off Jeremy. I only mentioned the frame because I have been surprised at how much punishment a quality frame can take.

I think that making an EV that can do 30 mph and is legal would be a big plus. I hope that you can get acceptance from the DoT. The 15mph limit puts a lot of people off e-bikes as many can easily exceed this speed without a motor.

Will it have pedals? Do you have a target spec yet range/weight etc?

Jeremy · Apr 8, 2008

To be honest, it's taken a lot of digging around to get the definitive interpretation of the law, but I think I have it straight now. The motorcycle in question is an old Yamaha RD50MX, which is legally a moped. The frame is relatively light (I'm guessing that it's around 35 to 40kg minus engine etc) and is already registered.

Apparently, as long as I only change the engine and transmission to an electric motor, it doesn't need to go through any form of special approval process. All I need to do is apply to get the engine type and number, plus fuel type, changed on the registration document. I've been warned that I may be asked to show that the motor power is limited to 4kW maximum and that a speed limiter is fitted.

The motor I have purchased (a Mars ME0709) and the controller (a 200 amp Kelly KD48201) is easily capable of delivering up to about 9.6kW maximum, but the controller is software programmable from a PC, so it can be limited to the 4kW legal maximum. The original engine fitted to this little bike was only a few hp, perhaps 4 or 5, so 4kW should be plenty.

I will probably add a speed limiter to keep the maximum speed down, but this is not quite clear from the regulations. They state that the "design speed" should meet the limit, not that it should be enforced by any device.

Range will be dependent on the depth of my pockets when buying batteries. The frame will take around 60 or 70 Ah of LiFePO4 at 48V, which, if my estimate of Wh per mile is reasonable, should give a useful range of around 40 to 50 miles at 30mph. I will probably only fit about 30 to 40 Ah at first, as I can't see that I will need a range of more than about 20 miles.

If I were to choose to remove the current limit and run the controller at maximum, then the acceleration would probably be quite interesting. Top speed will be limited by the maximum motor rpm, rather than the power available, and is gearing-limited to about 50mph at the moment (13t motor sprocket, 37t rear sprocket). With the controller current limit adjusted down, then the power can be reduced to set the "design speed" to a legal figure.

I am in the process of getting all the frame parts shot blasted and primed, prior to building up the rolling chassis, ready to install the motor. I have a lot of work to do, as I need to make a new seat pan and dummy fuel tank to house the batteries, plus install some hefty cabling, a contactor (to kill the power easily) and a big power fuse.

It doesn't need to have pedals, as it will remain classified as a moped. It can be ridden on an ordinary full car licence (no need for a motorcycle licence), is exempt from road tax and I've been advised that it should be relatively cheap to insure.

Jeremy

frank9755 · Apr 8, 2008

I agree with Jeremy that it is not wise to take a bike beyond its engineering limitations. Some of the more extreme creations on Endless Sphere with high powered motors and vast batteries to give them any sort of range have ceased being bikes and I would not want one of those.

However I think there is scope to extend the performance of electric bikes a little, in the direction of the limits that John suggests. Often this involves configurations that would be legal in other countries, such as the US, where 20mph is a typical speed limit or even Australia, where the limit is not on speed but only on average power output. The tongxin kit I attached to my hybrid bike was this sort of modification. As it was capable of speeds of up to 22mph it went beyond the laws in this country, but the bike, its brakes and wheels could cope with that sort of speed (which is not an unusual speed for a non-electric bike), and the very modest weight addition.

Unfortunately that Tongxin kit didn't work! If I were going to do another one now, I would either get a Tongxin with Hall sensors and a controller from someone else (eg a crystallite from ebikes.ca), or one of the tried and tested Sufou Bafang motors & controllers, from ecrazyman on ebay - which are pretty light and are giving excellent performance in (illegally fast) Ezee and Wisper bikes.

Frank

Rob Gale · May 13, 2016

The biggest question with E-Bikes in the UK. Is why does our Government choose to diversify from the rest of the EU and make Ebikes slower than other people around the EU can enjoy. For example E-Bikes in Germany can do 45Kph. So based off conversations here and UK ledgislation are we to assume that the Germans are all stupid and dont understand Scientific Principles of Engineering. The fact that they are the first Nation to have EVER put an object into Space, seems to have escaped many !... So Personaly, I think their E-Bike speed limit should be adopted right accross the EU, including the UK.

the_killjoy · May 13, 2016

But the big question is what happened to Jeremy's 'moped'

flecc · May 13, 2016

Rob Gale said:
The biggest question with E-Bikes in the UK. Is why does our Government choose to diversify from the rest of the EU and make Ebikes slower than other people around the EU can enjoy. For example E-Bikes in Germany can do 45Kph. So based off conversations here and UK ledgislation are we to assume that the Germans are all stupid and dont understand Scientific Principles of Engineering. The fact that they are the first Nation to have EVER put an object into Space, seems to have escaped many !... So Personaly, I think their E-Bike speed limit should be adopted right accross the EU, including the UK.

I'm afraid you've misunderstood the position Rob, Germany has exactly the same 25 kph pedelec law as us, it's EU wide.

In addition they have an S class of 45 kph pedelec which is subject to various restrictions. They have to be registered and have a number plate, they have to be insured for third party risks, riders must wear helmets and they are not allowed on cyclepaths. So not the same thing at all, and only a very small proportion of their pedelec sales are the S class.
.

Alan Quay · May 13, 2016

the_killjoy said:
But the big question is what happened to Jeremy's 'moped'

Jeremy left in a huff a number of years ago. I can't remember why, but he was a knowledgeable chap.

Sent from my HTC One_M8 using Tapatalk

D8ve · May 13, 2016

fabola said:
Well, the legal limit is 25kmh, so 22kmh is not so far below. Of course it could be more powerful. I have measured it to maximum 242Watt from battery (uphill and when starting). With 90 percent effiency it means 220Watts to the wheel. The legal limit here is 250 watts continous power. On flat at 22kmh it was 115 Watts from battery.

I had a crapsbury. Under powered ? Perhaps. But the frame and components were early agricultural. The effort to move that bike was terrible. Range and speed were snap.
Other legal bikes were much better. Look at the new light bikes some of them look as if they could be fast.

My current bike had good components, to day I maxed at 50 mph did around 18 miles in traffic stopping to assist someone and averaged about 27 kph.
The bike is legal. Disk brakes defiantly nessisary.
Used less than 20% of battery power to do it as well.

anotherkiwi · May 13, 2016

Jeremy said:
I will probably add a speed limiter to keep the maximum speed down, but this is not quite clear from the regulations. They state that the "design speed" should meet the limit, not that it should be enforced by any device.

Most EU countries have a 45 km/h speed limit on mopeds. If you go through a speed trap at over that your bike could come under some very careful scrutiny and another fine would complete the speed limit one...

I like the idea except for the battery box being up so high (I am presuming where the fuel tank is). The bike can handle a bit of speed because often there isn't much difference in build strength between 50cc and 125cc versions.

(NoLongerRegistered#15675) · May 13, 2016

Alan Quay said:
Jeremy left in a huff a number of years ago. I can't remember why, but he was a knowledgeable chap.

Sent from my HTC One_M8 using Tapatalk

That's probably why he left...

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