Anyone Running Power THRU the Bottom Bracket?

[5-7HEAVEN]

If the 30mm bearings fail to support the 1” shaft, I’ll machine the shaft to fit 25mm bearings.

If that fails, then I’ll install the Staton adaptors
and 25mm bronze bushings.

The adaptors screw directly in the bicycle frame.

Unfortunately, the adaptors and bushings need to be machined a lot, in order to fit the 25mm hollow BB spindle.

That might cause the bronze bushings or steel adaptors to fall.

I’m thinking, do I machine the bushings super thin, or do I machine the BB adaptors thinner and leave more meat on the bushings?

The bushings are cheaper.
I can machine them thin and leave the steel adaptors thicker.

If the bushings fail two times, then I’ll machine the adaptors thinner and leave thicker bushings.

The chainring sprocket needs to be about 30 mm from the frame’s seat tube.

I might need to shave the face of the bearing cup, to gain more clearance.

Time will tell, if I’ll need these back-up options.

 

[Chainlube]

If it doesn't work out you can always find a rear wheel from a moby and have a left and right sprocket with a drum brake.

 

[5-7HEAVEN]

If sending engine power thru the BB fails, I'll use a jack shaft.

If the 212 breaks too many skinny bike chains,
I'll replace the 7-speed freewheel/cassette
with an 8-speed hub that I have.

Then I can use a 415 chain.

 

[5-7HEAVEN]

Other weak spots are the five M5 studs that connect
the freewheel on the right-side crank arm/pedal to the freewheel on
the 24t chainring sprocket.

The M5 studs are 70mm long and .20" diameter.

The reason they're that long is so the pedal can clear
the right side of the engine.

I eliminated the pull-start housing and replaced it with
a 1/4" clear plexiglass plate.

That makes the 212 engine a little narrower.

If these studs fail, then I'll drill both case-hardened freewheels to
accept M6(.24") maybe M8(.31") studs.

One saving grace is that there's no resisting force, other than pedaling power.

One freewheel drives another freewheel.

 

[5-7HEAVEN]

Well, having two 30mm ID x 42mm OD x 7mm wide bearings in the BB will PROBABLY fail to transmit 212 engine power to the chain side.

A 7mm wide sealed bearing just doesn't seem like enough bearing support.

That's about the only bearing that'd bolt on, OUTSIDE the BB.

I found 25.4mm ID(1.0") x 50.8mm OD(2.0") x 14.3mm wide (9/16") sealed bearings reasonably priced.

Of course, no bicycle frame will fit these giant bearings.....

so I'm thinking of fabricating a BB out of 2.5" OD w/2.0"ID and weld it either ABOVE or UNDER the bike's existing BB.

Pros of placing a new BB ABOVE the bike's original BB:

1) more ground clearance, especially for the 7" diameter chainring sprocket.

Cons: 1)raised pedals might make it a funny-looking "clown bike"; 2) the chainline moves upward. The chain might contact the chain stay.

Pros of placing the new BB below the existing one: 1) better pedalling angle than the "clown bike";

Cons: a LOT
less ground clearance, interference with the chain stay,

 

[Wrench]

Well, having two 30mm ID x 42mm OD x 7mm wide bearings in the BB will PROBABLY fail to transmit 212 engine power to the chain side.

A 7mm wide sealed bearing just doesn't seem like enough bearing support.

That's about the only bearing that'd bolt on, OUTSIDE the BB.

I found 25.4mm ID(1.0") x 50.8mm OD(2.0") x 14.3mm wide (9/16") sealed bearings reasonably priced.

Of course, no bicycle frame will fit these giant bearings.....

so I'm thinking of fabricating a BB out of 2.5" OD w/2.0"ID and weld it either ABOVE or UNDER the bike's existing BB.

Pros of placing a new BB ABOVE the bike's original BB:

1) more ground clearance, especially for the 7" diameter chainring sprocket.

Cons: 1)raised pedals might make it a funny-looking "clown bike"; 2) the chainline moves upward. The chain might contact the chain stay.

Pros of placing the new BB below the existing one: 1) better pedalling angle than the "clown bike";

Cons: a LOT
less ground clearance, interference with the chain stay,

Howzit 5-7, haven't heard from ya in a while. I was starting to think ya gave up on this project.
Good to see everything's still in the works
ALOHA Wernch

 

[Chainlube]

Well, having two 30mm ID x 42mm OD x 7mm wide bearings in the BB will PROBABLY fail to transmit 212 engine power to the chain side.

A 7mm wide sealed bearing just doesn't seem like enough bearing support.

That's about the only bearing that'd bolt on, OUTSIDE the BB.

I found 25.4mm ID(1.0") x 50.8mm OD(2.0") x 14.3mm wide (9/16") sealed bearings reasonably priced.

Of course, no bicycle frame will fit these giant bearings.....

so I'm thinking of fabricating a BB out of 2.5" OD w/2.0"ID and weld it either ABOVE or UNDER the bike's existing BB.

Pros of placing a new BB ABOVE the bike's original BB:

1) more ground clearance, especially for the 7" diameter chainring sprocket.

Cons: 1)raised pedals might make it a funny-looking "clown bike"; 2) the chainline moves upward. The chain might contact the chain stay.

Pros of placing the new BB below the existing one: 1) better pedalling angle than the "clown bike";

Cons: a LOT
less ground clearance, interference with the chain stay,

What about chopping off the stock BB and make a whole new BB with your 2.0 ID?

 

[Ralpho]

Isn't standard American BB pretty close to 2" ID? Might be easier just to use another frame.

 

[Ralpho]

2.028" ID American bottom bracket. There's a special retaining compound "Locktite 609" and primer "Locktite SF 7649" that is used for this type of application. I've never actually done this but the thought has crossed my mind with using the 2 inch bearings.

 

[Chainlube]

Isn't standard American BB pretty close to 2" ID? Might be easier just to use another frame.

It's been a long build, I don't think 5-7 wants to change it now.