Geared mid drive on FRONT wheel: Yes it can be done.

[Logic11]

Take a look at this clever front suspension:

More pics etc here:

VLR bumblebee AWD bike, ASC system, geared hubs.

The mini-moto is built according to an all-wheel drive scheme with 2x1kW gear motors, controled by two KLS4812S with addition ASC(anti-slip-control) system to prevent any wheel slip. Peak power 2kW on each motorhub. The total moment is 84N.m. Maximum speed 75 km / h. Three-crown front fork -...

endless-sphere.com

If you mounted a mid drive with it's sprocket centered on that suspension pivot point you could have a powered front wheel, with gears (or not) and no extra, hub style, unsprung weight.
Nice for 2WD setups where 2 motors will overheat half as fast or slower. ie: be more efficient.



(I noticed a pic where someone had 'swiped this suspension design and put large elastic bands around from the fork arms to that back bar rather than springs.
Anyone know who that is?)

edit:
I attached a picture of what I'm madly on about.
(it's 'geared' to reverse I know, but I didn't want to draw over the inner sprocket etc)

 

[Chalo]

Yamaha 1993:

 

[bananu7]

If you mounted a mid drive with it's sprocket centered on that suspension pivot point you could have a powered front wheel, with gears (or not) and no extra, hub style, unsprung weight.

I'm sorry, but mounted how and where, exactly? There's no space on the front fork for a motor there, and anything mounted on the part used for steering will negatively impact steering with its inertia. Well, maybe won't be an issue for longer calmer trips on longer straights, but those aren't the ones where you need AWD in the first place.

From what I've seen, the only practical use for an AWD bicycle is snow, and maybe deep mud and sand. Everywhere else it's simply better and easier to use a bigger rear wheel motor.

 

[Chalo]

From what I've seen, the only practical use for an AWD bicycle is snow, and maybe deep mud and sand. Everywhere else it's simply better and easier to use a bigger rear wheel motor.

Generally speaking, you're probably right. But there are other advantages including contextual ones. Setting up a good 2+ kW bike can easily be more than twice as expensive as setting up a 1+ kW bike, because equipment for the latter is far more common and cheaper. The parts run cooler, weight distribution across the bike is better, torque increases more than top speed, and the motors spend more time in a higher efficiency range (assuming all the motors are optimized for single motor setups, power/RPM wise).

The other night after teaching a class, I raced back home about 3 miles as fast as my 2WD bike would go. It has a 48V x 22A geared hub motor in front and a 48V x 30A geared motor in back. I saw 34 mph downhill, and 25 mph on the steepest uphill sections. After arriving at home, I checked the temperature of components and found that everything as barely warm to the touch. The controllers were slightly warmer than the hubs. On the same run at about the same speeds, my big direct drive rear hub bike still has pretty modest temperatures, but noticeably warmer whether I run it at 60A or 40A.

As for drawbacks, the dual motor bike is noisier than the big direct drive bike (which is almost completely silent), it slips the front tire a little bit on hard starts, and there's a subtle shift in steering response when getting in and out of the throttle with front wheel power (just like a FWD bike).

I like that my 2WD bike has three independent systems for getting down the road. The two motors only share a battery and a throttle, and they're independently switchable on or off.

So while the real reason I have a 2WD bike is because I had already accumulated the pieces I needed for it while doing other projects, I don't think it's an inherently bad idea.

 

[Logic11]

I'm sorry, but mounted how and where, exactly? There's no space on the front fork for a motor there, and anything mounted on the part used for steering will negatively impact steering with its inertia. Well, maybe won't be an issue for longer calmer trips on longer straights, but those aren't the ones where you need AWD in the first place.

From what I've seen, the only practical use for an AWD bicycle is snow, and maybe deep mud and sand. Everywhere else it's simply better and easier to use a bigger rear wheel motor.

I have attached a very basic picture.

See the point where the front suspension hinges:
That you would make the common center for both that (bearinged) hinge AND 2 sprockets, one inside the fork and one outside, on a common center shaft.
You can then put a chain from that inside sprocket to the wheel as the distance between them remains constant.

The outside sprocket could be a std geared sprocket set and the mid motor mounted to the top of the forks, above the front wheel, with a chain going down to the geared sprocket set.

Alternately an internally geared hub motor could simply be mounted so that it's (extended) sprocket shaft shares that common center.

You could then add another one to the other side, to balance things out, if you so wished. That would double torque, allowing a higher top speed and/or lower motor temperatures.


As for why I'd want a 2wd bicycle;
I'm in The New South Africa.
ie: what used to be a 1st world country with roads, sewage and electricity is fast becoming the kind of 3rd world nightmare you can't even imagine without a fly up one nostril and an old turd up the other.

(Thats exactly what happened in the rest of 'became independent' Africa, but apparently, we study history as a means of boring ourselves into a state of short sightedness rather than learning from past mistakes)

Tarred roads are fast becoming the slower way to travel vs driving or riding next to them.
Thats what happens when a tared road is more pothole with mini, flat topped, tarred mountains in it.
So yes; lots of soft sand and (if you're lucky just) mud.

Incase you're wondering; I walk or don't go.
Thats not liable to change as I'm the wrong colour to find employment here.

The reason you'd want 2WD bike if not doing serious off-roading is simply that 2 motors working together don't overheat. when you're in a ...er hurry!

 

[bananu7]

So while the real reason I have a 2WD bike is because I had already accumulated the pieces I needed for it while doing other projects, I don't think it's an inherently bad idea.

Well, neither do I, but as I said, I think the conditions need to be just right, making it inherently more of a niche thing.

For reference, I run a 30H hub with 45A @ 48V and it's been taking it quite well so far. It's in a hardtail frame, and the battery makes the weight balance be closer to even than I'd expect; it's a relatively small motor for this power, and a relatively large (13s10p) battery. Considering the availability both of that and the 45H motors nowadays, as well as 60A controllers both for 13s and 16s, I think it'd end up more cost-efficient for most builders to run a single non-geared rear motor.

 

[Az.]

That is not a mid drive motor, is it?

 

[Logic11]

Well, neither do I, but as I said, I think the conditions need to be just right, making it inherently more of a niche thing.

For reference, I run a 30H hub with 45A @ 48V and it's been taking it quite well so far. It's in a hardtail frame, and the battery makes the weight balance be closer to even than I'd expect; it's a relatively small motor for this power, and a relatively large (13s10p) battery. Considering the availability both of that and the 45H motors nowadays, as well as 60A controllers both for 13s and 16s, I think it'd end up more cost-efficient for most builders to run a single non-geared rear motor.

So you saw my picture and understand the concept now?

 

[Logic11]

Yamaha 1993:

That looks heavier than just a Hub Motor for a motorbike.
And waaay complicated!
Why not just a Hub oil pump in 1993!?

I assume if they redo a 2WD they'll use this idea here to keep unsprung weight down, or a hub motor, and generator.

 

[bananu7]

That looks heavier than just a Hub Motor for a motorbike.
And waaay complicated!
Why not just a Hub oil pump in 1993!?

I assume if they redo a 2WD they'll use this idea here to keep unsprung weight down, or a hub motor, and generator.

This is a heavily modded Yamaha GTS1000, it wasn't a 2WD bike; just had an unconventional front suspension.

So you saw my picture and understand the concept now?

I do and I did. Again, considering the builds running single rear drive hub motor, overheating isn't an issue of the topology, but of the chosen motor. For any given power, two motors will almost always weight more than a comparable single one that's big enough for the desired use. What's the desired power of this contraption?

 

[Logic11]

I do and I did. Again, considering the builds running single rear drive hub motor, overheating isn't an issue of the topology, but of the chosen motor. For any given power, two motors will almost always weight more than a comparable single one that's big enough for the desired use. What's the desired power of this contraption?

This isn't a question of whether a 2WD drive bike is a good idea or not.
It's all about being able to make one if you like and how it may be made to work.
ie: You don't want one, but IF you did want a geared 2WD drive bike you could now make one.
That's just a 'good to know'

I doubt I'll ever own a E-bike
$ 5000 is R 88 400 here. That's about what I'm managing to earn in 6 months if I'm lucky, despite being able to 'see' solutions looking for a problem like the above.
So basically I'm just an Engineer trying to avoid going insane from mental inactivity.

One real world problem the above solves is Unsprung Weight.
Unsprung weight is a huge issue for handling and traction etc at higher speeds.

Lets say you built a Motorbike for the Paris Dakar race or something similar.
In that situation the above means of implementing 2WD is a very good way to avoid these issues.

NB that the original suspension is also Anti-Dive under braking, making for a safer bike.
The main reason being that the rear brake will be more effective as the rear wheel would be less inclined to lift.

It may not visually appeal to those who want to look cool just like all the other sheep, but I'm quite happy to let the other sheep go their own inane way. I don't even consider their opinion of me any of my business.

The desired power is 1 000 000 000 KW!
But in the suggested configuration it would fall under the same constraints as any mid drive.

 

[lnanek]

Amusingly, I do have gears on my front wheel:


Just because it's the only wheel I had spare with a long enough axle when building out an Ariel Rider X-Class frame. I suppose it's designed for fat tires, which I'm not a fan of.

 

[Chalo]

That looks heavier than just a Hub Motor for a motorbike.
And waaay complicated!
Why not just a Hub oil pump in 1993!?

I assume if they redo a 2WD they'll use this idea here to keep unsprung weight down, or a hub motor, and generator.

There was no front drive on the Yamaha GTS1000. But it had a front swingarm that was mechanically very similar to the homemade one in the top post.

 

[bananu7]

This isn't a question of whether a 2WD drive bike is a good idea or not.
It's all about being able to make one if you like and how it may be made to work.
ie: You don't want one, but IF you did want a geared 2WD drive bike you could now make one.
That's just a 'good to know'

Fair, but even then, it's not exactly a revolutionary concept, as you probably know best. Christini has been making 2WD systems for years, and if you don't need a mechanical connection to the front wheel, KTM and Yamaha had their oil-driven motors.

Frankly instead of focusing on unsprung weight so much, I'd love to see something closer to the new Can-Am with the engine in a swingarm. Sotion has actually been selling those as kits, I think?



Take that, add tilting for steering with a mechanical linkage and you get a perfectly symmetrical AWD bike

 

[Logic11]

Fair, but even then, it's not exactly a revolutionary concept, as you probably know best. Christini has been making 2WD systems for years, and if you don't need a mechanical connection to the front wheel, KTM and Yamaha had their oil-driven motors.

Frankly instead of focusing on unsprung weight so much, I'd love to see something closer to the new Can-Am with the engine in a swingarm. Sotion has actually been selling those as kits, I think?

View attachment 361302

Take that, add tilting for steering with a mechanical linkage and you get a perfectly symmetrical AWD bike

Oh ye the Hydraulically driven front wheel; 2WD motorbike system has been around for years and did very well in the desert sand in the Paris Dakar race. I think that's where it 1st debuted.
I remember discussing the idea online a year or 2 before it's debut.
So no; I never thought 2WD bikes the new part.

Then there are a good number of hub motored 2WD systems. Both home made, like the one linked in the opening post and from retailers etc for silly prices.
Some even have ASC and ABS via the controller.

What makes this idea unique is that you can have:

• A geared front wheel using off the shelf e-bike/bike parts.
• The unsprung weight advantage.

Unsprung weight in large rear drive hub motors is already an issue discussed here a lot.
Especially when people discuss FWD.

Funny how different people think differently:
I don't see any advantage to the pictured swing arms besides:

• The unsprung weight of the motor having less leverage. (is that the right way of putting it?)
• The distance between the motor and the rear sprocket being fixed, resulting in better chain tension control = less maintenance.

Personally I'd put the motor closer to the swing arm swivel point and the shock mounting behind or above it.

Wait!? You want to put that in front and just tilt/lean that whole show to steer?
That wont work; it HAS to be able to swivel left-right relative to the rear wheel.
All lean does is make it so you don't fall over once you do steer it.
Think about it: you can lean your bike but keep your body upright and keep going straight. Try it.

 

[Logic11]

There was no front drive on the Yamaha GTS1000. But it had a front swingarm that was mechanically very similar to the homemade one in the top post.

Ah! Thx ye I wondered. I thought perhaps the drive was on the other side.

 

[Logic11]

Amusingly, I do have gears on my front wheel:
View attachment 361293

Just because it's the only wheel I had spare with a long enough axle when building out an Ariel Rider X-Class frame. I suppose it's designed for fat tires, which I'm not a fan of.

he-he!

Now I'm seeing a long armed rear derailleur going nuts as the front suspension works.
As in; have a derailleur with a bigger distance between the 2 small sprockets and a stronger spring, pointing forward.
The bigger distance between the 2 small sprockets would be to take up the increased slack caused by suspension travel.

The issue would be that the wheel slows as the shock compresses and accelerates again on rebound.
Also powering the motor would make the shock compress as the motor pulls on the chain, causing the bike to 'nose dive' on acceleration!

My idea has a similar slow-fast issue, but to a much lesser degree, that is ameliorated more as the drive inner sprocket gets smaller or the driven inner sprocket on the wheel bigger.