MBB for a SunTrip bike

[antoniv]

Greetings, I would very much like to have your advice.

I am starting a solar bicycle project to participate in future editions of The Sun Trip.

Basically the vehicle must be able to support a 300W solar roof, batteries, motors and luggage.

It will be a new construction, made of steel.

I'm thinking something like a Cruzbike longtail.

The question is:

Is the MBB architecture suitable for a solar vehicle?

Possible problems that I can guess:

Low speed operation of the movable front part.
Control with lateral winds.
Impossibility (or not) of a BB engine

What do you think?

In fact, a CruzBike Silvio has already participated in the Sun Tour France. But carrying a very reduced solar surface.

 

[Henri]

I'm thinking something like a Cruzbike longtail.

I am not thinking of solar, but I do want a longtail as well! I had somebody tell me, that a flevobike tandem rides unproblematic (but have in mind that he is a well seasoned rided of varied recumbents) and so I'd hope, MBB works as well with the long wheel base and some luggage at high positions.

Impossibility (or not) of a BB engine

When you build the bike for it, it should be impossible, but the placement of the weight is probably bad for riding. You think about BB so you can use the gears? Some hub motors have gears as well. And/or a front and read hub motor can be geared differently, to excel at different speeds.
Also you can have a rear wheel with gearing and connect a motor with a chain. You can probably use certain BB motors, if they can be run with external controls or use a hub motor with a chain output at the brake disk mounts or use any motornwith the right specs and mount a sprocket. - Could even use a rear wheel with a fixed gear and put a gearbox between motor and chain without freewheel, with or without clutch, to allow for regenerative breaking.

Control with lateral winds.

Wind should have two effects:
- tilt your bike
- push your steering
I guess a carefully designed bike could have the steering impact be roughly what you need to catch your balance from the tilting impact in a sudden gust. Keeping stable in a steady stream I don't know. Would it be more challenging than on any other recumbent or upright with two wheels?

 

[antoniv]

I am not thinking of solar, but I do want a longtail as well! I had somebody tell me, that a flevobike tandem rides unproblematic (but have in mind that he is a well seasoned rided of varied recumbents) and so I'd hope, MBB works as well with the long wheel base and some luggage at high positions.

Some examples of MBB longtails that work.

 

[antoniv]

When you build the bike for it, it should be impossible, but the placement of the weight is probably bad for riding. You think about BB so you can use the gears? Some hub motors have gears as well. And/or a front and read hub motor can be geared differently, to excel at different speeds.
Also you can have a rear wheel with gearing and connect a motor with a chain. You can probably use certain BB motors, if they can be run with external controls or use a hub motor with a chain output at the brake disk mounts or use any motornwith the right specs and mount a sprocket. - Could even use a rear wheel with a fixed gear and put a gearbox between motor and chain without freewheel, with or without clutch, to allow for regenerative breaking.

I'm thinking about two motors to have safety redundancy. A DirectDrive motor in the rear wheel to take advantage of regeneration when braking and a geared motor to use on climbs. The Bafang BB motors are very interesting for solar use, but you could also use a geared hub one.

It is clear that a motor in the BB means a lot of weight in the steering, but some CruzBike has already mounted it.

 

[antoniv]

I'm very interested in the MBB architecture but I'm worried about how it will perform with the added weight of the sunroof, motor and luggage, approx 45kg (100 lbs)

I'm not worried about the strength of the structure. What I really have doubts about is how the steering will behave with the weight. Will it be much harder to handle?

For an adventure of many days, the additional work to hold the steering, could I accumulate more fatigue than an LWB in my arms?

 

[CoachellaRider]

I'm very interested in the MBB architecture but I'm worried about how it will perform with the added weight of the sunroof, motor and luggage, approx 45kg (100 lbs)

I'm not worried about the strength of the structure. What I really have doubts about is how the steering will behave with the weight. Will it be much harder to handle?

For an adventure of many days, the additional work to hold the steering, could I accumulate more fatigue than an LWB in my arms?

I hope you don't mind a very amateur answer - I'm probably one of the physically largest people on a cruzbike right now. I'm 6'7'' (200cm) with a wide set of shoulders, even at my skinniest I weigh about 100 pounds more than most people (and I'm not at my skinniest at the moment.) I've been riding for about 6 months, and I don't consider my extra weight to be much of a factor. It did take me longer to learn to ride than most of the people who post in the "learning to ride time" thread, but I couldn't say if that's because of my size or because I hadn't ridden a bike in 20 years.

A bigger concern for me would be the wind catching the sunroof. I don't know that it would be any worse than a DF though.

If you haven't ridden an MBB before, I would recommend getting one and learning it before you build your project. MBB is definitely a different dynamic than DF, and requires a different set of skills to learn.

 

[AbramClark]

I've been riding electric Cruzbikes for over 10 years. Just for fun I put a BBS02 mid drive motor on a Sofrider once and although it worked it wasn't great. The efficiency was equivalent to a rear geared hub motor which I much prefer. The geared hub motor in the rear is the perfect solution for electrifying a Cruzbike. No rolling resistance, plenty of torque, lightweight, doesn't interfere with drive train, and all wheel drive. I can see the attraction to having a direct drive for regen braking, but I suspect it's not worth the extra weight. If you get a quality hub motor it should last 5-10k miles with no maintenance, so I wouldn't mess around with 2 of them.

I really hope you pursue the solar project. It would be really cool to see one in action. It would be nice if you could make a stock frame work, but I'm having trouble picturing how to attach the front supports for the panel.

Note if you wait maybe a year Grin Tech may be selling their geared "Freegen" hub that allows regen braking.