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I'm trying to figure out the minimum specs of each components of the new party bike I'll be building to make sure nothing fails prematurely, but I also don't want to over do it because of cost and weight.

This is our current bike, for reference. We will use a similar design as a starting point, but it will be greatly improved. You can see there is seating for 7 passengers on each side (only 6 pedals because of the rear axle), 2 on the rear bench, one driver plus up to 4 standing up in the middle (dance floor), and yes they dance and party and yes we did rides with 20 passengers plus the driver, yes it was a pretty wild summer.

The new design will use gearbox instead of open spur and sprocket gearing. We will also use bigger shafting and stronger frame construction, along with better quality components.

Here's what I need to know for now :

The force required to break the inertia of the vehicle from stop to forward;

The energy required to accelerate the vehicle from 0 to 10km/h;

The force required to keep the vehicle momentum at 10km/h on a uphill direction of given angle;

The maximum torque that could be inflicted onto the components when the wheels are locked;

The minimum torque or strength rating of each components for shock load and at max rpm.

The party bike consist of a total of 12 people facing each other on each side, so 6 people on the left and 6 on the right. Each person can pedal at their own pace due to an individual freewheel for each rider. The crankset is linked to a shaft running the length of the side, so all 6 people power the same shaft on their side. Then, using a "T" 3-way right angle bevel gearbox located at midpoint on the shaft, the output of said shaft is being transferred perpendicularly towards the other side of the bike, using a 1:1 ratio. The output of the gearbox from each side then give into a third "T" gearbox that direct the power toward the front of the bike to a front wheel drive axle. There is no clutch or over-load protection at all. The rotation of the front wheels is directly linked to the rotation of the shafts and when in reverse, also rotates the pedals.

Since the driver can only steer and brake, people try to stump on the pedals as hard as they can when we're about to let go the brake at an intersection or when we're stopped, or when we start to brake, because the pedals only move forward if the wheels are moving too. With up to 12 people weighting down or pushing down the pedals and the brakes locking the wheels, there is a lot of torque applied to every components of the bike, as well as when we're going uphill, or trying to keep up a top speed on flat or uphill ground.

Considering the bike itself weight about 1 700lbs and we can have up to 20 people on the bike (but only a max of 12 to pedal) plus the driver, plus backpacks, boom box, etc, a worst case total weight could be of :

1 700lbs + (21*200lbs) + (21*5lbs) = 6 005lbs

Least worst case weight with 12 riders plus driver without gear would be of :

1 700lbs + (13*120lbs) = 3260lbs

So we are looking at minimum specs for a load of 6 000lbs, or 2 723Kg, for a front wheel drive vehicle with no suspension (the pneumatic of the tires is enough by itself for the comfort), powered by up to 12 (200lbs) riders who could put out easily 1340lbs/inch of torque each when wheels are locked, or roughly 1,8 to 2 HP each when going uphill and spinning cranks at 90 to 120 rpm while standing on the pedals. Each gearbox would collect 6 riders and the central gearbox would collect the whole output of the 12 riders and give it directly to the front axle, then to the wheels (hopefully I'll be able to find a front axle differential at below 1:3.5 ratio). With our current bike, we found a sweet spot of a 0,75:1 ratio between one rotation of the crank and 3/4 rotation of the wheel. Assuming a similar bare bike weight and tire outer diameter, we would aim for such final ratio. If my understanding of power is correct, this means the HP needed to move the bike from inertia to forward and the HP needed to have to bike moving at 10km/h in flat ground with only the normal air and tire friction, plus gravity, or to move it at 10km/h uphill, will directly tell me how much HP each rider would need to produce if they are all in sync or how many riders minimum would be needed to pedal the bike without discomfort (going at a slow pace).

The crank arms are about 170mm long (6,7"), the ratio between crank and freewheel would be of 1.6:1, the steel shaft would be of a minimum 7/8" diameter, of 5' long sections spaced at 2' between each rider (so each freewheel would be 2' apart, next to a billow block bearing) and a "T" right angle gearbox with 1:1 ratio would be in the middle of each side, collecting a 5' shaft of each side (from the front of the bike and the back of the bike) and then to output to a center "T" gearbox that could be of increaser ratio to achieve the proper crank to wheel ratio.

Wheels would be 15" rims, lets say 20" diameter tire.

What minimum and recommended ratings would my gearbox need to be ?

I was looking at the Hub City model 66 gearbox, that gives me a max of 2 330 lbs/inch of torque with 3,7 HP at 100rpm, but I don't know if it would be able to withstand 6 people stomping on the pedals (do torque adds up or is it non-linear like decibels are ?), knowing that a single rider could give 1340/1.6=838lbs/inch of torque right away ?If I go with 838*6=5028lbs/inch, I'm looking at a heck of a gearbox to withstand that initial shock load torque when we let go the brake and people are eager to start moving. It uses a 1,25" shafting. The model 65 is the same, except with dual hollow shaft and one solid shaft.

I was also thing about using a 4 way gearbox with two hollow shaft and two solid, in the middle, so I could also install a DC motor on the 4th shaft that would be the same physical shaft as the one going to the front wheel drive axle, so I can use it as a generator and electrical brake/load when going downhill and as an assistance when moving the bike alone and up/down the trailer, etc.

Hope I didn't made it too complicated !

David

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# Torque specs for 6,000lb party bike

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