Electric2011 Dahon Jetstream P8

[Deleted member 4366]

The cruise control is operated from the handlebar switch - on or off. With it off, the pedal sensor is in control. As soon as you throw the switch on the handlebar, the bike tries to go the speed set on the potentiometer. It's like a throttle with no return spring that you can switch off/on. The pedal sensor always tries to give full power, so not so good for battery life.

You can buy reed switches from Maplin. They're like a little glass tube, and when you pass a magnet over them they switch. You can buy the cheapest bike computers off Ebay for about £2. The sensor is a reed switch, so you can cut it off at the computer end and use it with the magnet that comes with it. The magnet screws to the cable like it does to a spoke. You have to do a bit of trial and error with the positionibg. They work best if the magnet comes from the side and close. If you have it too far away, it doesn't switch off so well.
Miniature Reed Switches : Reed/Proximity Switches : Maplin Electronics

 

[cwah]

Thanks Dave, you're my source of inspiration!!

I still don't understand about the throttle. Isn't it simpler to just have a throttle rather than a cruiser switch with a potentiometer? With a throttle you can still adjust the speed isn't it? So why do you want to use the potentiometer instead? And with an on-off switch it's less secure as the bike can continue to roll if you don't turn it back to off position.

 

[Scottyf]

That's why D8veh uses the brake cut outs to kill it and the speed if need be.

You could do similar if you removed the spring from a half throttle and you could adjust it on the fly. Although I'm sure it wouldn't be as accurate at sticking to one speed like the pot is.

 

[Deleted member 4366]

The main problem it solves is when the pedal sensor gives too much power, so you need about half throttle for riding on the flat. I found that it's almost impossible to hold half throttle for anything more than about 10 seconds. Also, while pedalling up long steep hills with the throttle ope,n it's not so easy to get full strength pedalling. Once you've tried the potentiometer setup and got used to it, you''ll see how convenient it is. There is however one significant problem: You stop with the brakes because you've suddenly come across a friend and want to talk. You forget that the cruise is on and you let go the brake, whereupon the bike lurches forward. That's why you need reliable brake cut-offs. Not such a problem with a small motor, but dangerous with a powerful one. You soon learn the discipline of switching off the cruise before you come to a permanent stop.

 

[cwah]

But I suppose the throttle is the same as the one we find on motorcycle and moped? How do they do during long cruise? I always thought they were just using half throttle or something similar.

If the pedal sensor gives too much power, what about getting a torque sensor?
EBike Crank Torque Sensor - BMSBATTERY

 

[Deleted member 4366]

It's easier to hold a motorbike throttle constant because you're not pedalling and they have better suspension so you don't get bumped about so much.

BMSbattery have never had those torque sensors in stock during the last 12 months and they still don't have any, otherwise I would have tried one. I'm not sure if you can change the chainwheel to a bigger one, which would mean that it's no good for 20" wheel or high speed.

 

[cwah]

Not sure neither if we can change the chainwheel. I've seen some torque sensor on other places such as alibaba:
Electric Bike Torque Sensor-Electric Bike Torque Sensor Manufacturers, Suppliers and Exporters on Alibaba.com

The only concern about these torque sensor is that it seems it only work until 25kph (from BMSbattery specifications). So I won't be able to use that otherwise I'd be interested too.

 

[Deleted member 4366]

I finally got out for a bit of a ride on my Jestream. I did nearly 9 miles of gentle hills with a couple of short steep bits.

I know that there's a few people waiting for opinions on the Cute motor, so I hope they find this helpful.

Performance-wise, the bike is similar to my old Sunlova, which had the standard Bafang 250w motor and Chinese controller at 15A max. The main diference is that this one climbs better. It's is because it's a 201 rpm motor in a 20" wheel. It's designed for a 26" wheel, which would give about 15mph, so effectively it's downgeared by a ratio of 20/26. The speed would have therefore been about 12mph max, but I've got round this by running it at 44v (actual nearer 48v, and it's a 24v motor). Under most circumstances it runs up to about 17mph, but I think it can pull to about 20mph. Most of the time I had my speed control set to about half. At that setting the motor is totally silent, and it's difficult to detect that the bike is electric except I can still pedal up fairly steep hills in the middle gears. I suppose you could say that it's like an un-assisted bike, but with gravity tilted a few degrees so that you don't need so much effort. I only used the highest setting for the very steep hills, which it could still do in gears 5 or 6 out of 8. The motor is still very quiet under full power - much quieter than a Bafang.

The free-wheeling is also very good. I hit 23mph free-wheeling down a slight but long down-hill section.

Overall, I'm impressed with the motor and the general performance of the bike. I've been spoilt by the suspension on my other bikes, so it wouldn't be fair to judge how the small wheels go over the rougher surfaces, but the one thing I don't like is that the bike is very twitchy when you stand up on the pedals while you're coasting down-hill BMX style. I guess that that would be the same for any 20" wheel bike. I wouldn't want to go much faster than 25mph on it. So, my conclusion on the motor is that it's better than a Bafang, but i can't say whether it's as robust. One other thing: For the first tests, I ran it sensorless, and there was a bit of a graunch, which felt like the clutch taking up (Couldn't be the clutch necause this one has a ratchet and pawl), but now I run it sensored and the graunch has gone now, so sensored has an advantage over sensorless. I've heard a couple of people comment on this slight graunch on the Bafangs, and it could be the same reason.

I've just ordered a couple of 8Ah 6s zippy packs, which will be the permanent batteries for it. When they arrive, I'll make a proper box for them to be mounted behind the rear suspension unit. The 5.2Ah Winforce ones tht I've been using, which fit nicely in my pocket, are a little bit saggy at full power (I don't know how they claim 20C!).

Here's the data from my Speedict:
miles 8.73
Ah 2.03
max watts 686
wh per GPS mile 6.21

 

[cwah]

Thanks for this nice report Dave.

When you say it's better than the Bafang, is it just because it's much more silent, or is it more torquy or more efficient?

How's the torque compared to a Bafang? If I get a cute128 do you think I can do wheelies on a Brompton?

 

[Deleted member 4366]

Power's about the same, but smoother and quieter. Look forward to ypur report on the 128.

 

[cwah]

Isn't that quieter and smoother only because the motor is smaller?

If I get a stronger cute motor (I'm thinking either about the cute-128 or the Cute-12 1000W) wouldn't that be as loud as a Bafang?

 

[Deleted member 4366]

Isn't that quieter and smoother only because the motor is smaller?

If I get a stronger cute motor (I'm thinking either about the cute-128 or the Cute-12 1000W) wouldn't that be as loud as a Bafang?

I'm comparing it with the 250w Bafang like you have in your bike. The Cute's slightly smaller, but not much.
Best would be to try the 128 and then we'll all know if it's any good.

 

[cwah]

I'm hesitating.. I also purchased the mini hub motor from Conhismotor. But they may take forever to send it to me.

I'm just afraid the cute 128 couldn't handle all the power. I'll probably melt it at 1500W and it's not sure it can go up to 25-30 mph.

 

[Deleted member 4366]

I'm hesitating.. I also purchased the mini hub motor from Conhismotor. But they may take forever to send it to me.

I'm just afraid the cute 128 couldn't handle all the power. I'll probably melt it at 1500W and it's not sure it can go up to 25-30 mph.

Which version of the mini hub did you order, I've got one that i've never used marked 250w 36v. It feels very heavy for its size, so hopefully has a lot of copper in it.

 

[cwah]

I have this model:
http://www.conhismotor.com/ProductShow.asp?id=76

I'm planning to overvolt it to either 74V or 92V with lyen controller. Hope it can handle 1000W+ continuous and 1500W peak.

Is this motor any good?

 

[Cyclezee]

I suppose you could say that it's like an un-assisted bike, but with gravity tilted a few degrees so that you don't need so much effort.

I think that is great quote Dave

 

[morphix]

I'm going to copy what you did Dave for my JetStream P8 conversion and fit the Q100, so glad to find this thread! Any pics of your JetStream available?

 

[Deleted member 4366]

Photos here:
Dahon pictures by d8veh - Photobucket

 

[morphix]

Photos here:
Dahon pictures by d8veh - Photobucket

Very nice! Definitely looks better with a rear motor I think.

 

[Deleted member 4366]

Rther than mess about with reed switches and brackets, if I did it again I'd use those "hidden wire" brake switches that you can buy alongside your kit. As far as I can figure out figure out, these brake switches have three wires (5v 0v, signal). You can pick up the 5v supply from the throttle or PAS, and then you connect the signal to the "high voltage" beake switch wire, which is a single wire in a double connector on the controller. Unfortunately, I forgot to order these switches with my last controllers otherwise I would've already tested it, but it looks like this guy has already done it - scroll down to number 13 for a schematic.
KU63 motor controller
HWBS - Hidden Wire Brake Sensor 1pcs - BMSBATTERY