Would it be possible to change the rider v motor power ratio on a crank drive system?

[Kudoscycles]

Flecc....you seem to understand precisely how the pedal sensor system operates....perhaps you could advise why nobody has invented a pedal sensor/crank drive set up where it is possible to change the rider input-motor input ratio by manual overide....in other words if the pedal sensor detects the rider input and offers motor assist in say 1:1 ratio but if the rider gets tired he can change this to say 1:2 ratio and interpolate in between.Not an electronics expert but with the knowledge of others on this forum it would seem to me that such an arrangement would be simple to engineer.
Dave
KudosCycles

 

[Deleted member 4366]

It's very easy to do. The torque sensors sense how hard you push, The software/hardware in the controller decides how much power to give. The manufacturers can give it any power profile they wish, but most set it as a direct ratio of input (by pedal) power to output power, which I believe is daft because in some circumstances you want it the other way round - more power for less pedalling. The Storck Raddar does exactly what you suggest, but it's still proportional. The idea of giving full power with minimal effort or as soon as you start pedalling is OK for low powered (250w) motors, but could be dangerous if the power is going to be increased. Several times on my BPM motored Giant, I've forgotten to switch off the cruise control so that as soon as I let go the brake it gives full torque and the back will kick forward leaving me holding the bike upside down. It's nearly kicked in my front door a couple of times! The power algorithm in the controller needs very careful thought to get it how you want and safe.

 

[hoppy]

Dave,the easy answer is a throttle! That's why so many of us love the Tonaros. You can vary the amount of assist continuously according to how much effort you want to put in. Make sure your proposed crank drive has a throttle and gears and keep the price below a thousand pounds and it could sell big! Regards,Andy

 

[flecc]

That's almost what we have already Dave. For example the Panasonic system has it's standard rider to motor ratio at 1 to 1. The Eco ratio is set at 1 to 0.5 meaning the rider gets 50% assistance, and the high power setting gives the increased ratio. That increased ratio has grown over time. In 2007 it was originally 1 to 1.3, then grew through 1 to 1.5 to 1 to 2 currently, meaning the assistance now given in high power mode is double that of the rider input.

There's no interpolation for intermediate settings, but I question whether that's necessary. My experience of these is that it's unlikely that anyone could tell the difference between such fine changes in level.

If there's a weakness in these systems is that of the ceiling power of the motor. For example, there's many riders who could input 300 watts for a short while, even I can for a few moments, but in high power ratio the 400 watt peak motor clearly cannot produce double that input, 600 watts. So when the rider puts in anything over 200 watts, the system cannot meet it's full specification.

 

[Kudoscycles]

Hoppy(Andy)....I have decided to fit throttles to all my future bikes,when it seems relevant, but to meet the EN15194 to sell in Europe,we need this to be easy disconnect. But the Spencer Ivy crank drive bike that I rode in London noticeably reduced the power as I reduced my pedalling power,the Cannondale Bosch powered bike I rode at Eurobike also had the same characteristics but was less noticeable because there was so much more power available-I rode both bikes on the maximum PAS setting.
Flecc....I did not appreciate that the PAS control changed the ratio,I thought it just changed the motor power,always learning!....maybe the ratio should be even higher,say 1:3,that would allow a tired rider to get the full 250 watts,with only 80 watts rider input...d8veh suggests that this could be dangerous,but as Dave points out with only 250watts available that should be ok.
What does everyone think of the new TransX Gryphon bike,I really liked the style but at this stage not sure of the technology.
Eddie....we have a new bike en-ship to us,especially for use on motorhomes,its weight is only 18kgs,20" wheels,8Ah battery,easy fold,36v motor...I think it's an attractive bike and well engineered...price will be £725.00 incl vat,replacement batteries about £200.00....full details and photos available early 2012.
Happy Christmas everyone
Dave
KudosCycles

 

[flecc]

I don't really know anything about the TransX Gryphon other than the easily available information, but we are being overwhelmed by all the new crank units now, rather too many for the market now I think. Panasonic, Yamaha, Bosch, Daum, Pacific, TransX, Kalkhoff etc. The use of square and triangular section frame tubes on the Gryphon seems a bit gimmicky to me, no perceivable gain and possibly weaker.

Back to the distribution of power between rider and motor, the Swizzbee system is interesting, now out of production but an expensive variant made in the USA under the Dolphin name by Izip.

In this, the rear hub is effectively a differential like that in cars, but used in reverse. Instead of the crown wheel sending variable drive from the propshaft to two half shafts and the rear wheels, the half shafts are the hub inputs, one side from the cyclist, the other side from the motor, and the resulting inputs summed into the hubshell and therefore the wheel.

You can see from this that the input from either rider or motor are infinitely variable in proportion.

In the practical realisation of the Swizzbee, the right hand input is a derailleur cassette, the left hand input a belt drive from a 270 watt Heinzmann motor mounted in the top of the rear frame triangle just below the saddle area and cowled in with the battery and controller. The motor is throttle controlled. Below are two photos of the bike, and below those some further information links:

The diagram in the webpage from this link shows and briefly describes this arrangement designed by Michael Kutter of Switzerland, bicycle mounted.

The diagram in the webpage from this link shows and describes an as yet unrealised variation in which the output of an integrated hub motor is summed with the cyclist's derailleur input.
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[mike killay]

The easiest way to achieve what the OP wants is to have a 'click throttle' the same as on my electric boat.
Just arrange for positive click stops in the throttle as you advance it. For safety, fit a dead man button.

 

[Kudoscycles]

Hoppy....the crank drive less than £1000 is not currently possible....all the current crank drive motor manufacturers,whether European or Asian,seem to be influenced by the Bosch price point and not wish to disrupt the high prices achievable-I personally was almost thrown off the Bosch stand at Eurobike when I genuinely asked for an offer to buy 1000 Bosch motors and ship to Asia to be installed into my King bicycle...the resultant price would have not been £1000 but would have been very close to it. But we are working on producing a crank drive bike wholly manufactured in Asia, both motor and bike,but these things take time.

Dave
KudosCycles

 

[flecc]

we are working on producing a crank drive bike wholly manufactured in Asia, both motor and bike,but these things take time.

Dave
KudosCycles

The Pacific Cycles unit I wonder? It's beautifully neat and compact, possibly the best yet in these respects.

 

[hoppy]

Great news on throttles and crank drive,Dave and congratulations on your success so far. Recently you could buy a container of Tonaro crank drive bikes for about 20k GBP. I know there's lots to add for retail but direct sales would be cheaper as Powerpedals showed before appointing dealers. My Tonaro cost 870 GBP direct last April.

 

[Kudoscycles]

flecc/hoppy.....flecc>as a result of your comment I had a good look at the Pacific Cycles system and also that of MPV drive,both Taiwanese....but the opposite of Chinese manufacturers these companies don't seem interested in producing at high volume at a low price point...Pacific Cycles produce some innovative bikes but mainly in relatively(for Asia)low volume...there is however a chinese motor manufacturer looking seriously at producing 10,000 crank drive motors at a very competitive price point....they keep asking me how many crank drive bikes are sold annually in the UK,hence why I keep asking that question....unfortunately I think the honest answer may only be hundreds,what do others think?,so the market for them may be Germany which seems more to have embraced the crank drive concept.
Am off to China spring 2012 to progress the specification and discuss the fitment into a Kudos King style frame. In the meantime our dealers have shown a lot of interest in our new 'Safari' bike,hub drive is not 'last year' it is ideal for so many customers and remains good value.
Dealers are an essential part of bike distribution and servicing,direct selling is all very well until something goes wrong then the local dealer is value for money.
Dave
KudosCycles

 

[flecc]

I would have thought the sales of crank drive bikes in the UK exceeds 1000 per annum currently and quite possibly exceeding 2000, mainly Kalkhoff, Raleigh gmbh, Spencer-Ivy, BH-Emotion, Tonaro, Gepida, Haibike, plus the odd personal imports like KTM and kits from Cyclone. Realistically any order contemplated would be in hundreds rather than several thousands though.

Germany is the main market for them now, The Netherlands having realised after a brief flirtation with Panasonic powered Gazelles that hub motors are all they need. The same true of the other low countries and Denmark of course.

The market for crank drive units is oversupplied with choice now, but there remains a clear opening in the budget market. PowerPedals with the Tonaro models partly filled that, but their prices have increased markedly more recently and are at or near some of the competition.