Crank drive comparisons - Impulse .v. Bosch .v. Panasonic

I have recently had the chance of reasonable test rides on Bosch and Panasonic drive bikes so I thought it might be helpful to offer a few personal observations about how these drive systems compare with the Impulse system I am most familiar with. I must stress these are personal opinions and other people could well ride the same bikes and come to different conclusions - it is always best to try out a variety of bikes for yourself, although this can often be difficult to arrange with limited availability of many premium brands. For reference, the bikes used for this comparison were step-thru models of a Swiss Flyer (Panasonic 25.2v system), Gepida (Bosch 2013 console / software) and Kalkhoff Agattu (Impulse 2013 software). The bikes all had similar specs (apart from the motor / battery) and had the same Nexus 8 hub gear. They are similarly priced at a little under £2000. All the bikes are available with larger capacity batteries at additional cost (Panasonic 403Wh, Bosch 400Wh and Impulse 612Wh)

 

The most striking thing, perhaps not that surprisingly (given the 25.2v battery - 302Wh) was the lack of power from the Panasonic motor. I would liken it to driving a minibus up a hill. It would climb steep hills slowly in a low gear but even gentle inclines seemed to require quite a bit of effort in higher gears. The 3 levels of assist seemed to only marginally change the feel of the assistance provided. With gentle pedalling, the torque sensor sometimes made for a jerky ride but overall it was generally quite smooth. On the plus side, this was the quietest of the 3 motors. It may be that the latest 36v system has more power but i'm told this is not noticeably the case by someone who has tried both.

 

The Bosch system (36v battery - 300Wh) was much more powerful but noticeably noisier that the other two. The four levels of assist gave clearly differentiated levels of assist. The assist was delivered smoothly across the range. The bike also felt better with the assist turned off although this might be nothing to do with the motors, just a comparison between the Gepida and the Swiss Flyer. Having said that, the bikes have the same gears and weigh about the same so they ought to be similar to ride unpowered. The Bosch console (the only bike with a display console of the three I tested) was well located, easy to read and informative.

 

The Impulse system (36v battery - 540Wh) on the Kalkhoff feels similar to the Bosch with plenty of power and clearly differentiated assist delivered through the 3 settings. Delivery is smooth and it's quieter than the Bosch, but not as quiet as the Panasonic. This year's Agattu models don't have a display console but they are available on other Kalkhoff models.

 

So, motor wise I would say there is not a lot to choose between the Bosch and the Impulse with the Panasonic being disappointing in comparison. Taking into account the battery capacity provided in the standard spec the Kalkhoff offers the best value package and all round solution for those requiring extended cycling range. If range is not important, then it would be a question of personal preference.

The TCN chinese crank drive is so much more powerful than the Bosch system,but the power is so much more refined in the Bosch.....interestingly any BPM motored hub drive (BH Neos,Kudos Arriba and Tornado) and the KTM E-race Panasonic is more powerful than any of the crank drive systems,so the pendulum,in terms of power,has swung back in favour of hub drive....however I suspect that the Bosch system is much more efficient and therefore the range is longer....we recently had opportunity to back to back test all of the foregoing,the KTM E-race Panasonic is so much more powerful than anything else out there at the moment and by quite a margin,how do they get all that torque out of 250 watts?

KudosDave

ps....I think what is happening here is that whilst crank drive is potentially the more powerful system in terms of torque delivery, the limitation is that the Shimano gear systems cannot handle any more power-the chain just cannot transfer any more power-perhaps what is needed is a different power transfer system than a chain,or maybe special chains-it would be interesting to put a strain gauge in the chain when max torque is delivered from the crank.

Whereas with hub drive the wheel can cope with much higher torque,it is only limited by the strength of the spokes,which could easily be upgraded....I suspect that the hub motor engineers are able to find a lot more power and the wheel can cope with the torque developed.

Flecc also indicated similar thoughts in one of his recent postings.

I am soon off to Eurobike,I wonder how many new hub drive bikes will be exhibited.

KudosDave

Edited August 10, 201312 yr by Kudoscycles

the KTM E-race Panasonic is so much more powerful than anything else out there at the moment and by quite a margin,how do they get all that torque out of 250 watts?

KudosDave

a misprint?

 

the KTM erace P runs on 48V battery with high discharge rate.

 

I think 48V systems should not be allowed on e-bikes because it's too easy or tempting to get 30mph+ out of them. At that sort of speed, fatal accidents are very possible.

Edited August 10, 201312 yr by trex

a misprint?

 

the KTM erace P runs on 48V battery with high discharge rate.

 

I think 48V systems should not be allowed on e-bikes because it's too easy or tempting to get 30mph+ out of them. At that sort of speed, fatal accidents are very possible.

 

Here it is in action:

 

http://www.fusionelectricbikes.co.uk/wp-content/uploads/2013/04/KTM-eRace-P650-wheelie-2000px-300x199.jpg

good gracious me, how naughty is that.......

Not a misprint,see below KTM E-Race P specification,bike meets EN15194

 

Technical Specification

 

Motor/Battery

 

Motor Panasonic 250W PCT

 

Battery 47V 8.8Ah

 

Controller LCD handlebar controller

 

 

Frame/Fork

 

Frame Size 43-48-53

 

Frame Colour Black & Silver

 

Fork Rock Shox 650b Revelat. RL 100 with 100mm travel & remote lock out

 

 

Cockpit

 

Headset Ritchey Comp Logic Zero Drop-In

 

Stem Ritchey Comp 4-axis

 

Bar Ritchey Comp 2X Flat 720

 

Grip KTM VLG864-1AD3 Neoprene

 

 

Brakes

 

Disc Tektro Rotor 180mm

 

Brakes Tektro Auriga Comp Disc with recuperation

 

 

Gears

 

Gears Shimano Deore XT 30 Speed

 

 

Drivetrain

 

Crankset Panasonic/Shimano 42-32-24

 

BB-Set Shimano Oktalink

 

Cassette Shimano HG62-10 11-34

 

Chain Shimano HG74-112

 

Pedal Welgo M21 Light Alu MTB

 

 

Wheelset/Tyres

 

Rims/Wheelset Ambrosio Pulse Black650b Disc

 

Front Hub Shimano Deore XT - 100/15TA 6b

 

Rear Hub Panasonic hub motor PCT Disc

 

Tyres Schwalbe Racing Ralph 26 x 2.25

 

 

Saddle

 

Saddle Selle Italia X1 Flow

 

Seat Post Ritchey Comp 350/27.2

 

 

Taken straight from KTM Austria website

KudosDAve

[ATTACH]6479.vB[/ATTACH]

another photo of what the KTM erace can do.

^^ controller current turned down over test range is the most likely explanation. Up it and the speed will shoot up if the battery is high discharge, but so will the consumption. Has anyone derestricted these yet and actually tried them to see if they are geared for it ?

 

W.r.t. speed, I think it's often put to one side that roadies regularly break 30, 40 and even 50mph on downhill descents. Just because they have dropped handlebars doesn't necessarily mean they are great cyclists. OK their bikes are lighter but as far as how dangerous this is to the rider, those speeds are no more or less dangerous on a road bike than an e-bike.

 

An e-biker with an 8.8Ah battery won't go more than a few miles at 30mph assisted on the flat on a derestricted KTM eRaceP.

Torque has nothing to do with speed. Motors can be designed for any torque and still comply with EN15195. To get high torque and high speed you need high power. High power does drain the battery faster.

 

Whether a motor has 1v or 48v has nothing to do with compliance, speed or torque, or power. These things depend on motor design. IIRC a 48v battery is as much as you're allowed under EN15194,

 

I agree with Kudos Dave. Hill climbing ability has nothing to do with the type of drive (hub vs crank). Neither types are more efficient than the other. Bikes that multiply your pedalling effort (current control rather than sped control) give the impression of being more efficient by making you pedal harder.

 

EN 151994 has no limit on torque, The only rating is on what label the manufacturer can stick on the motor re power. Over the last couple of years we have seen torque and power increase substantially as manufacturers have figured out the actual requirements of EN15194. I think we can expect to see bikes with enough torque to get up all but the steepest hills with little effort, like we always wanted them, and they'll still be legal. Bikes like the Ezee Forza, Kudos Tornado/Arriba, BH Emotion Neos, KTM E Race P can climb most hills with less pedal effort than the Bosch, Panasonic and Impulse crank-drives. Only on exceptionally steep hills does the balance swing the other way. Hub motors could and will be designed for even better hill-climbing. Crank drives can only be pushed so far until the limits of the transmission are met, while as there's virtually no limit for hub-drives

 

IMHO crank drives are a fashion that'll lose popularity in the future as more sophisticated higher torque hub motors take over.

...Only on exceptionally steep hills does the balance swing the other way.

 

That's still the key to me. It seems that the nicest places to ride are all in the national parks, and all the national parks around me, the Lake District, Snowdonia, Yorkshire Dales and the Peak District all come with plenty of exceptionally steep hills.

That's still the key to me. It seems that the nicest places to ride are all in the national parks, and all the national parks around me, the Lake District, Snowdonia, Yorkshire Dales and the Peak District all come with plenty of exceptionally steep hills.

 

The crank-drives can out-climb the standard 250w Bafang SWX type motors on steep hills, but some of the more recent hub-motors can out-climb them on very steep hills. When I say"exceptionally steep", I mean steeper than 30%,which most people are unlikely to encounter.

 

I have three hub-motored bikes that can out-climb any Bosch, Panasonic or Impulse drives on any hill, so it's still not a question of the type of drive, but rather on how much torque it can produce

d8veh, which hub climbs the best on the super steep stuff?

hub drive is like crank drive stuck in just one gear. You may have selected a high torque or a high speed hub motor but you are still stuck with just one gear.

Xiongda is bringing out a new dual speed motor to give it a second gear.

Hub motors can only climb well if they are big beast with a big, fat battery.

Edited August 11, 201312 yr by trex

Xiongda is bringing out a new dual speed motor to give it a second gear.

 

And SRAM already have one on the market, though with only one cycling gear. Hopefully the Xionda will also accept a multi-sprocket freewheel, or less likely, a cassette.

the xiongda XD motor New Double-speed Motor - Suzhou Xiongda Motor Co., Ltd. is not as advanced as the SRAM unit but will be easily obtainable through aliexpress. At the end of the day, it comes down to personal choice. If you don't care for the throttle then crank drive is better and if you hate chain banging then you buy a hub.

.

Hub motors can only climb well if they are big beast with a big, fat battery.

That's not the way I see it. Look at the KTM Erace 650 P. The Panasonic hub-motor is not a big beast, and neither does it have a fat battery. Also, compare the weight of a Bosch drive system with a 500w Bafang CST. Which one climbs the best?

 

You don't have to have a big battery to climb well. I have batteries that weigh less than 2kg that can deliver 7kw, which is enough to winch you up a cliff at a reasonable speed.

 

Whether you have a crank-drive or a hub-drive. If you're going up a hill at the same speed with the same pedal effort, you'll be using the same amount of torque and power. If you want an easy time climbing steep hills, then you'll be using a lot of watt-hours whichever motor you have, so if you want to go a long way like that, you need to carry a big battery.

I still think crank drive is a better implementation, given the same output from your powerplant.

the Panasonic (2013) is indeed a beautiful beast and it is powered by a very potent 48V battery. That's why it outperforms the (2011) Bosch DU25 but does it outperform the Bosch DU45 or the 48V 8-Fun BBS01? I am considering upgrading to a 48V system but to be honest, I am scared by its power.

Edited August 11, 201312 yr by trex

the xiongda XD motor New Double-speed Motor - Suzhou Xiongda Motor Co., Ltd. is not as advanced as the SRAM unit but will be easily obtainable through aliexpress. At the end of the day, it comes down to personal choice. If you don't care for the throttle then crank drive is better and if you hate chain banging then you buy a hub.

 

Thanks Trex, confirms that a freewheel thread mount is available so far more useful than the SRAM which is only any use to a moped-like market.

That's not the way I see it. Look at the KTM Erace 650 P. The Panasonic hub-motor is not a big beast, and neither does it have a fat battery. Also, compare the weight of a Bosch drive system with a 500w Bafang CST. Which one climbs the best?

 

You don't have to have a big battery to climb well. I have batteries that weigh less than 2kg that can deliver 7kw, which is enough to winch you up a cliff at a reasonable speed.

 

Whether you have a crank-drive or a hub-drive. If you're going up a hill at the same speed with the same pedal effort, you'll be using the same amount of torque and power. If you want an easy time climbing steep hills, then you'll be using a lot of watt-hours whichever motor you have, so if you want to go a long way like that, you need to carry a big battery.

 

I was of the understanding that if you are running at low speed on a steep hill the hub will be running at a lower efficiency than a crank spinning at optimum rpm, and the lower the speed the greater disparity.

If I can ride again it will be at low power outputs from the human half of the hybrid so I am very interested in which can climb the steepest hills with out significant help

hub drive is like crank drive stuck in just one gear. You may have selected a high torque or a high speed hub motor but you are still stuck with just one gear.

Xiongda is bringing out a new dual speed motor to give it a second gear.

Hub motors can only climb well if they are big beast with a big, fat battery.

Trex,what you say was true until the latest BPM-CST motor came out from Suzhou Bafang....the motor manufacturers are learning how to wind these motors to bring the torque lower down in the motor speed range,even 4 mph is ok to get onto the torque curve.

It's easy to achieve the torque higher in the motor speed and after all we are restricted by law to 15 mph power cutoff.

Now we have learnt how to do this we are working with the motor manufacturers to achieve even higher torque figures in the lower motor speed ranges,all EN15194 legal. In practice they are quite range efficient because the higher low speed torque soon allows the rider to gain speed quickly into the more efficient higher speed.

Crank drive has to consider the limitations of the chain transmission system and the Bosch system incorporates a 'soft start' take off that prevents sudden shock loads on the chain-remember how Shimano took away their guarantee on the Nexus hub gears because they were concerned that the gears may not be able to take the power of both rider plus motor. Crank drive is currently limited until someone comes up with a stronger transmission system than the bike chain-maybe belt or shaft is the answer.

However,power is not everything when it comes to the rideability of an ebike....if I were commuting to work every day I would choose the KTM Macina Bold,its just such a nice balanced relaxing bike to ride,I expect the Kalkhoffs are similarly effortless ride....sort of automatic Mercedes.

But IMHO they are not exciting,the latest KTM e-race Panasonic,BH Neos and Kudos-BPM bikes are raw power and great fun....sort of manual Porsche

The KTM e-race Panasonic is definitely the benchmark for putting 'torque on the road'.....we are currently working on a new Kudos hub drive bike for 2014 that will match it but it's difficult currently to beat that bike,maybe thats enough....the instant torque of these ebikes makes them accelerate very quickly at the traffic lights!!!

Shame we haven't got a Redbridge style event coming up,it would now be very interesting for Pedelec members to compare these bikes.

KudosDave

do you know when is the next Redbridge?

I was of the understanding that if you are running at low speed on a steep hill the hub will be running at a lower efficiency than a crank spinning at optimum rpm, and the lower the speed the greater disparity.

If I can ride again it will be at low power outputs from the human half of the hybrid so I am very interested in which can climb the steepest hills with out significant help

 

It depends what you mean by 'low speed',with the old and very cheap 8-fun motors you really had to be up to 8 mph to get onto the motor torque curve but these BPM motors will achieve that at 4 mph. If you are meaning down at 2 mph with very high cadence then yes the crank drive will allow you to climb very steep hills with max torque,low gear,high cadence-currently no hub bike will allow you to climb steep hills at such a slow speed.

If your legs are so tired that you cannot achieve that 4 mph threshold speed then crank drive is probably best. Also crank drive and torque sensor hub drive gives very intuitive power delivery which results in a very relaxed riding motion.

Recently,because of the number of different bike styles and brands at the new London Electric Bike Company shop I have had the possibility of riding many more bikes,would really like to try the Haibike FS AM(inverted Bosch crank drive) against the KTM e-race Panasonic(rear hub drive),that would be a very interesting comparison,both bikes aimed at off-road usage-unfortunately the latest 2014 Haibikes are not available until mid August,note the price of the FS AM is £650 cheaper than the previous All Mountain bike.

I am amazed the technology and design improvements that are going into this ebike market,especially considering the size of the market.

KudosDave

do you know when is the next Redbridge?

 

It is intended to be Sunday May 18.....we are also intending to repeat the Manifold Trail,Derbyshire event on Saturday May 10. Both dates reasonably definite.

KudosDave

On flat roads, a relatively neglected advantage of crank drive is the ability to multiply speed through gearing, I can easily get to 20mph+ with light pedalling, not possible with my previous hub motor. That feeling is like the years are simply rolled back.

Edited August 11, 201312 yr by trex

However,power is not everything when it comes to the rideability of an ebike....if I were commuting to work every day I would choose the KTM Macina Bold,its just such a nice balanced relaxing bike to ride,I expect the Kalkhoffs are similarly effortless ride....sort of automatic Mercedes.

But IMHO they are not exciting,the latest KTM e-race Panasonic,BH Neos and Kudos-BPM bikes are raw power and great fun....sort of manual Porsche

 

But this is where a conflict can and probably will arise with the legislators. The whole point of the regulations for pedelecs is to keep them very close to remaining bicycles in every way, moderate performance and speed that doesn't need riders to be pre-qualified or have the protection of third party insurance for others.

 

The legislators answer to "raw power and great fun" is likely to be more regulation and the loss of the bureaucracy free life the current pedelec law gives us. The German high speed and high power e-bike classes point to how unwelcome this could be, compulsory insurance and helmet wearing, registration and number plates, and worst of all, the loss of use of the off-road cycle routes we use at present.

 

That's moped land.