Just a wild expensive wayout random thought question

[mountainsport]

I was wondering if this is posibble guy's to have two types of systems all built into one.I was thinking of an ebike that has a crank drive system and a front or rear hub motor that could be switched over at different intervals. For example a crank drive for hills whilst the hub motor for general usage.

Or is this just pointless,i know this would add much more weight to the bike first and foremost or can you wiz kids think of something else that seems more practical and realistic.

Mountainsport.

 

[Old_Dave]

Or is this just pointless

practical and realistic = horse for the course

 

[Deleted member 4366]

It's entirely feasible.
I've built two bikes with 2-wheel drive hubs, and three crank-drives 250w,350w and 450w, each one has advantages in some situations; however, I've come to the conclusion that ebiking nirvana is a 500w geared rear hub-motor with a lightweight 20aH battery. You should just be able to keep the weight down to 23kg any you'll have a bike with enough torque to drag you up any hill with minimal effort, enough speed to get you into trouble if you abuse it, enough range for 60 miles or more (depending on how you like to pedal), whilst still getting a smooth comfortable ride. If you like a work-out on your bike, you can always turn the power down. This setup is simple, robust and reliable. Why would you want to complicate things?

 

[KirstinS]

doesnt need to add that much wieght

For example, a great addition in mybook would be fastwind tongxin front motor to a crank drive bike. Assuming they use the same battery (i.e both 36v) you use the crank for hills and switch over to the tongxin on the flats for high speed (way over the legal limit I'm fully aware)

sounds fun to me ! And the only extra weight would a be couple of kg for motor and a few bits (contoller, throttle and system/battery switch)

 

[Deleted member 4366]

doesnt need to add that much wieght

Not sure what you mean there Kristin. Which crank-drive bike would you start with? The Pro Connect is about 24kg and a Tonaro's about 27kg. You'd have to spend thousands to get one less than 21kg, and even with a lightweight Tonxin, you'd be adding about 2.5kg, so whatever you do, it'd be difficult to get a bike as low as 23kg. Also, a Tonxin motor isn't particularly strong for speed. They can spin pretty fast, but if it's windy, you'll get that graunching noise as the rollers slip. They're much more suitable for lightweight folders or other light-weight bikes where the rider wants to provide most of the power.

 

[103Alex1]

you use the crank for hills

Not sure why you'd want the crank for hills. A powerful nippy hub motor would likely be far better for that. Crank is OK for short stretches of hill, but the peak output likely drops off on long steep climbs, or else you'll find it gets hard work. For 2-mile stretches of steep hill, for example, I will get lactic acid burn in my quads even on peak power max assist and dropping speed. Try any of the commercially available standard range bikes bikes on a proper challenging long climb and I'm sure you'll see soon enough. The higher torque (for want of a better way of putting it) commercially available £2k - £4k range ones are best but they won't out-perform bigger hub motors for hill climbing. Feel free to correct me if I'm wrong, but once you get into that territory of crank drive motor output performance management system, and you add in a hub motor too, you're hitting serious outlays - even on a build.

If you want a motor for sustained hill climbing rather than just hill starting you need consistent high power availability over a sustained period along with a 'nippy' hub motor unit (appropriate speed for your wheel size / setup).

 

[KirstinS]

Sorry, I was not very clear there. It would add around 2.5 kg as you say which is not a huge amount IMHO but the total weight depends on the bike you start with. Some of the haibikes are just over 20kg for example

Agreed re the tongxin power - but that's the idea here - dual drive. One for speed and one for power for use in the appropriate conditions.

Doesn't have to a tongxin - just an example of lightweight motor that I know can e bought in fastwind version

 

[KirstinS]

Oh an yes, in no way am I proposing this as a cost efficient idea ! It isn't - it would be bonkers for sure !

 

[Deleted member 4366]

I nominate Mountainsprt to build one as it was his suggestion. I think it'll be better if both motors can be engaged at the same time so ypu'd use the hub-motor for normal use and both motors for climbing. Why would you want to go slow if uou don't have to? You'd need a stronger battery for two motors though. I still think it's unnecessary complication. You can't beat a strong hub-motor.

 

[banbury frank]

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[flecc]

Here's one such e-bike, Giant Lafree with it's Panasonic crank drive and an added Heinzmann front hub motor, both 24 volt systems.

This owner went further though, adding a tiny generator on the carrier:

 

[mountainsport]

Here's one such e-bike, Giant Lafree with it's Panasonic crank drive and an added Heinzmann front hub motor, both 24 volt systems.

This owner went further though, adding a tiny generator on the carrier:

Nice one flecc i like that one regeneration missing though.

Mountainsport.