Electric kit for Helios Tandem?

[timw]

Hello everyone. I have a Circe Helios tandem, which has 20" wheels, and would like to add electric assistance to it. I’m considering two kits: the Ezee front hub motor and the Bafang BBS01 mid-drive kit. Can anyone offer any advice on these?

I think that the motor/battery will have more work to do on a tandem than a solo bike - we are hoping mainly for help getting up the hills, which are hard work on a tandem. We'd like enough range to cover 30 miles or so, which I imagine may need quite a big battery.

The Ezee kit should be straightforward to fit and has been done before:
http://www.pedelecs.co.uk/forum/media/ezee-powered-circe-helios-tandem.406/

I'm not completely sure whether the Bafang kit will fit. The motor would need to go on the front bottom bracket and be fitted with a 30 tooth chainring somehow. This connects via a long chain to the inner chainring (also 30 teeth) under the rear rider. I think it might work although the chain line will be altered a little. There are two other chainrings running 16 derailleur gears on the back.

Assuming the Bafang kit is an option, my main questions are:

Will the bafang mid drive, which can use all the gears, be more efficient than a hub motor in this situation? Will this translate into greater range?
Will the 250W Bafang system strong enough to cope?
How will hill-climbing ability compare between the two systems?
How about reliability?

I'd appreciate any advice or experience anyone can offer.

Thanks,
Tim

 

[Cyclezee]

Hi Tim,

Welcome to the forum.

We have converted 4 Circe Helios tandems.

Three with the eZee geared motor kit as you have already seen and one with the Heinzmann direct drive system.
You can see that one by clicking on the following link:
http://www.pedelecs.co.uk/forum/media/heinzmann-powered-circe-helios-tandem.405/

Both types can have 36v downtube or rear rack mounted battery with capacities from 11 to 15Ah
Because all these bikes have hub gears they were front wheel motors, but with the derailleur geared version a rear motor would be a possible alternative.

We offer an installation service or customers can fit the kits themselves.

 

[anotherkiwi]

Will the bafang mid drive, which can use all the gears, be more efficient than a hub motor in this situation? Will this translate into greater range?
Will the 250W Bafang system strong enough to cope?
How will hill-climbing ability compare between the two systems?
How about reliability?

When you have a hub motor you use all your gears too, maybe less often first gear. I was perplexed when I first started out and the secret of hub motor bliss is "Use the gears Luke!"

Range is dependent on the effort you put in. I get 70 km from a 10.4 Amp battery others get 35 from the same.

Yes it gives more than 250 W peak

I will tell you in a couple of weeks because my motor is on the way...

If you look after it it will last.

 

[D8ve]

The 30 tooth chain wheel Is not an issue.
The BBS uses a bespoke mount for the chain wheel.

But you can buy an aftermarket 30 tooth ring or the bbs adaptor to fit a 130 pitch(bcd?) chainring.

 

[mechaniker]

there are 30t sproket for the bafang-bbs on the market and also 36t ready to replace the original one without adapter

but I would follow John and use the front-hub
I like the Heinzmann because of the power but the ezee is also a good choice because of the freewheel.

Frank

 

[timw]

Thanks for all the responses.

Thanks John. The Ezee kit obviously works with the bike - have you had any feedback on how it performs or what kind of range can be expected? It seems to be a bit simpler than a crank drive, and with good battery options and support, so it has a lot going for it.

Any particular reason you would go with a hub drive, Frank?

There are lots of pros and cons to each system, but I'm still wondering how a BBS01 crank drive would feel in use, and whether it would have an efficiency advantage compared to a hub drive. Bearing in mind a tandem has more weight to pull up a hill, could this be more significant than on a solo bike? We're happy to pedal hard and use the gears up the hills, but just would like a bit of help.

Thanks again,
Tim

 

[D8ve]

I'm thinking that 30 tooth wheel suggests very slow grinding up hill.
Spinning the bbs has some advantage with the gears keeping it turning and driving despite slow speed.
A hub motor particularly a restricted one can( only can) become inefficient at slow to stalling speed. The current goes up and the motor can burn out. It will also eat the watts in near stalled state.
Spinning the bbs keeps you out of the stall and allows you to climb slowly without such a high heat waste.
Obviously I like crank drive. Hub is simpler and cheaper but that isn't always enough to make it better.

 

[timw]

Thanks D8ve. The 30 tooth chainring is deceptive - it's only connected to another 30 tooth ring to pass connect the power of the two riders. The derailleur gears run from 52 and 39 tooth chain rings under the rear rider. Without power, we do end up spinning the pedals as fast as we can in the lowest couple of gears, climbing slowly up the hills.

I see there is a GSM crank drive motor available also - I'll look into that one too.

 

[mechaniker]

Any particular reason you would go with a hub drive, Frank?

there is no advantage for a cranckdrive if the bike has 20" wheels and the power of a Heinzmann-Hub is higher as the Bafang bbs even on step hill but of course under consumption wattage.

good point on Heinzmann is his power but not good when the battery is empty.
Good on Ezee is the freewheel when the battery is empty you still can ride it like a normal bike and the ezee has nearly the same power as Heinzmann. The choise is yours. Myself I have Heinzmann but use with Lishui Controller and Phylion battery. Before I had a Bafang BBS in the same bike and I found it to weak.

The best is if you find somebody who has a tandem like yours for a testride because you want spend some money and for this money the result must give you a smile in your face ;-)

In a Forum you get trustworthy advise (but everybod has his own thinking or experience so it is never indepentend of own like´s but it´s your money so I always recomend testrides even when it is difficult to find somebody who already has your dreambike and give it to you for a few minit testride

 

[Benjahmin]

I have an Ezee front hub on my solo bike. I find hill climbing around Wales a blast. Most hills are climbed between 8 and 10 mph with input from me, at these speeds the motor is fine and doesn't get hot. Steeper hills can be down to 6 or 7, you can hear the grunt the motor is giving and I'm down to 2nd of 16 gears, but still the motor drives and I've only ever felt it vaguely warm and never stalled it. Wheel spin can be a problem on loose or muddy surfaces but I have a rather upright position on a hybrid frame. I imagine the extra weight of a tandem would help. Might be worth looking at a rear hub.
But if it's help with hills you need the Ezee's got the cajones to deal with 'em.

p.s. Mines the 14Ah battery I've never run it flat. At 25 miles the voltage is down but I reckon it would be good for at least another 10, being conservative.
Anyway, you could always turn the power off and feed your stoker another mars bar !

 

[Cyclezee]

Hi Tim,

Welcome to the forum.

We have converted 4 Circe Helios tandems.

Three with the eZee geared motor kit as you have already seen and one with the Heinzmann direct drive system.
You can see that one by clicking on the following link:
http://www.pedelecs.co.uk/forum/media/heinzmann-powered-circe-helios-tandem.405/

Both types can have 36v downtube or rear rack mounted battery with capacities from 11 to 15Ah
Because all these bikes have hub gears they were front wheel motors, but with the derailleur geared version a rear motor would be a possible alternative.

We offer an installation service or customers can fit the kits themselves.

One addition to the eZee battery options, there is now 19Ah rear rack mounted version available.

 

[timw]

We will probably want to use the bike unpowered for local errands (or when the power runs out) so if there is resistance in the Heinzmann motor, I think we would prefer the Ezee one. It's encouraging to hear how well the Ezee motor copes with Welsh hills. Not sure about a rear hub motor - we prefer loading luggage weight on the front of the bike as the balance seems better that way.

Given your range Benjahmin, perhaps we might hope for about 25 miles on a 14Wh battery, taking into account the tandem's disadvantage. A 19Wh option is certainly interesting.

As for crank drives, I've read discussions suggesting the crank drives should be more efficient in theory, but I don't know how much that translates to reality. Anyway, thanks for all the help.

 

[D8ve]

Er well I'm looking at 100+ miles with my 16ah battery
And it can be confirmed if anyone wants to do a twenty mile run with me using my 3ah battery that should prove it.

 

[timw]

I'm having trouble estimating a realistic range. We aren't particularly strong or lightweight cyclists, and I'm assuming a tandem will be less efficient as one battery is having to push two people. I was worried that limited range may be an issue for us which is partly why the crank drives seem interesting, if they might help extend it.

 

[Cyclezee]

I am not going to make any mileage claims because an accurate figure is practically impossible to calculate, there are just too many variables e.g. weight of rider, weight of bike, level of rider assistance, level of electric assistance, terrain etc., etc.
When it comes to tandems, provided that both riders are inputting some effort the range should not be less than a single rider on a solo bike.
If however both riders are giving minimal input and the machine is basically being used as an electric moped range is going to be poor whatever type of motor is fitted.

 

[D8ve]

You are right the battery will have to work hard to climb two people.

The questions are . What speed do you usually do on the flat?
How heavy are you all up.
How much climbing do you expect.
If you do 16mph on flat then All the flat miles are freeExcept starting.
Downhill costs when you climb.
How much assist do you want. The more work it has to do the quicker the battery goes.
How good is the bike and drive?
My Salisbury never got over 26 miles range. I returned it. Heavy rubbishy bike struggled to do 16 mph.
I worked my CDs and made 49 miles for the same battery.
Cruse at 17 on the flat sweating.
With my current setup I cruse at 17 with ease,I'm hypermiling and outperforming reasonable expectations. The motor only has to help uphill.

Think 10watts per mile for base usage. Then work hard yourself the battery will last longer. Be fat and climb a lot then the range reduces. Be fat and lazy with hills and bad gears the battery will last a few miles.

The golden rule is test ride as many as you can.
And research.
We need your input on how well a tandem can go and what range you can get for others. For information and research of course.

 

[Cyclezee]

Incidentally, I delivered an eZee bike to a customer in Oxford on Sunday morning, it is the second one that he has bought with a dual battery setup having a total capacity of 43Ah.
On my way home I got an email from another customer in Oxford who was asking about converting an Onderwater XL as his family has out grown his eZee powered Yuba el Mundo.
Personally, I wouldn't like the idea of sitting so far back and putting my nearest and dearest so far ahead when pulling out of a junction.

 

[trex]

it's usually not easy to fit a BBS01 CD kit to a tandem because most of them have an eccentric bottom bracket at the front for chain tensioning.
The front BPM motor is a much better choice on 26" wheels but too big, heavy and slow on 20" wheels. I agree with Mechaniker that a good DD motor like the Heinzmann is a pretty good choice on front 20" wheels but it's heavy and greedy on battery usage. My recommendation is the lighter weight SWX02 rear hub geared motor coupled with a 20A controller.

 

[Cyclezee]

Some photos just to illustrate some example of what we have been discussing.

Circe Helios with eZee 250rpm geared front hub motor, cadence sensor and throttle​

Circe Helios with Heinzmann 210rpm direct drive motor, torque sensor​

 

[timw]

I think I may have seen the Yuba Mundo around in Oxford, John.

I've come across a potential problem with the Bafang BBS01 idea. This is from Endless Sphere (https://endless-sphere.com/forums/viewtopic.php?f=28&t=76470&hilit=bbs*+tandem#p1154467) :

"I don't want to use the motor on the front crank ... with it running through the front crank, the stoker will always have to pedal if the motor is running unless you put an extra freewheel on their crank. It would negate any throttle only running."

So, if I put the motor on the front cranks, would the two riders' pedals will be able to get out of sync with each other? I don't think we need throttle only riding - we want to be pedalling - but A to B magazine (April 2014 issue) say the BBS01 without throttle lacked torque, although it might be possible to change in software.

Can anyone comment on this? I'd like the option of crank drive, but if someone with a better grasp of these things can rule it out as impossible, that would be progress!

Thanks again for all the input,
Tim