Drag in Bionx system

[Barry Heaven]

I have read a number of articles on the benefits/disbenefits of regenerative systems. There appears to be a consensus that the benefits are not very large with the current state of technology. However it seems to me that if a system could offer power regeneration with no drawbacks it may be worth having. For direct drive hub systems the main (only?) drawback seems to be the drag that is a part of such systems and which is always present even when regen is not actively switched on.

The Bionx system does appear to be a good choice but I have seen views on this vary from there being no drag to it being perceptible. No one seems to put a figure to this however so I have difficulty in understanding if regen is worth it at all.

Can anyone enlighten me?

 

[Andrew harvey]

The Bionx system does have drag, which increases with speed.
From experience, I've used 6 different types of direct drive motors over the years, the Bionx is by far the best in terms of drag. At low speeds it appears no worse than many geared motors wityh poor freewheels.
A good bike like the Airnimal move with slick tyres and a Bionx rear hub will ride better than a cheap electric bike with freewheel every time. In a simple roll down test last year mine was overtaking my old Suzhou Bafang powered bike down the A449 into Kidderminster. The Airnimal used much slicker tyres at 80 lbs compared to the marathon plus's at 40 lbs on the other bike.
Run a Bionx with the speed restrictor engaged you will feel like you've hit a brick wall as you reach about 17 mph, how much is due to the motor disengaging on how much is due to the clogging torque of the motor it's hard to say, but if you disable the speed restrictor you will not notice the drag till you hit about 25 mph,

 

[dimmer]

Hi Barry Heaven,
i recently purchased a used Bionx p250 kit and it does have a small amount of drag,ie if you spin the back wheel of the ground it comes to rest in a few seconds as oposed to it going on for a little while,if that makes sense.
The regen is fun to use as when you touch the brakes it puts power back into the battery.
I went for a 13 mile ride today and used 50% of the battery on a mixture of hills and flat at setting 4 (which is max power).
In use i do not notice any drag when going down hill or on the flat.
It can be programed in different ways for power/regen and i like to be able to put some power back when i want to,i prefer this to my Ezee Torque i recently sold,
regards,
George.

 

[Bigbee]

sad but true

The drag can be restrictive,but Ive managed a system over the last few months.During the day I take various bits of my wifes wardrobe and make up and stash it away.When shes asleep I change clothes put on bit of lippy and eye liner and Im away on me bike.Her crutchless knickers on a road bike saddle let in too much air,but its early days ,but can give me a stiffy

this post was a joke by the way !

 

[piotrmacheta]

I have an eZee sprint hub on my bike and I'm amazed at how little drag there is - it's almost completely free turning. My friend has a direct drive hub (1500W powerful one) from the Xipi shop in Banbury and when I tried it I noticed noticable drag when pedalling. However it went so fast on power that there's no point pedalling it!

 

[flecc]

The drag on the BionX is indeed very low as Andrew has said, and much lower than the usual internally geared hub motors. It's not an important factor is choosing a BionX, and the regenerative feature is switched in by the user anyway and does not have to be used.
.

 

[Barry Heaven]

Thanks for everyone's comments (even Bigbee's). Really good to have personal experiences. The drag question was really important to me as it would be annoying to find you had a system that was a permanent problem.