Bike tinker man

Retired here in Malaysia I potter around some of the older bike shops, & a few hours drive away, I was at one I go to few times a year, the old Chinese guy older than me out the back has store room full of old frames bikes etc, he recently been sorting them out, his English is terrible but his son speaks pretty English.

Anyway in there the other day looking around & I spotted a few interesting ones, I’m posting these pictures for everyone’s general interest & not asking any specific questions.

There is a very small boys Raleigh suit about an 8 year old but its complete little racing bike, complete with drop handle bars & SA. three speed, its dated 1978, lovely little bike.

There is a girl’s Raleigh little bit bigger size maybe 12 year old this looks like its new although old.

There is a frame hanging up what caught my eye was the very heavy gauge BB, when I lifted it down amazingly it was not threaded ? I cannot think how it could have been intended to use, unless it was from some form of very early moped, or even designed for shaft drive, interestingly no FD or RD cable routing ?

He also has a beautiful black Eddy Merckx frame there, pity no forks, very unusual inverted V rear brake bridge, no I did not photo it, really had a good look at it beautiful.

T-Mar

Non-threaded, large diameter, bottom brackets shells were common with one piece cranks. The cups faced outwards and were press fit into the bottom bracket shell, like headset cups pressed into a head tube. The cones were located outboard of the cups and threaded onto the spindle section of the one piece crank.

Bike tinker man

T-Mar I do appreciate your comment,

Here in Malaysia the place is littered with these very cheap China type one piece cranks, I’ve only worked on a few, but those had a larger BB ID to feed the one piece elbow crank through, (like the old starting handles). This was not a large ID the same as would normally be found if it were threaded, the point that caught my eye was that the BB shell wall thickness was about 3 times thicker than one would normally find, but the thickness where the down & seat tube fit are normal thickness, & the lack of any FD or RD cabling routing strange.

I've enlarged the photo

juvela

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Frame likely intended for a Thun/Thompson type chainset where cups are interference fit to shell. No shell threads are employed.

AlexCyclistRoch

Those are referred to as "Ashtabula cranks", produced in the US since about 1930 or so, I guess from some company in Ashtabula, OH (near where the domestic cheap bike industry used to be located).

ollo_ollo

Haggle for the best price on that Merckx, find a suitable fork and build that puppy! Don

T-Mar

If the shell is a standard inner diameter, then it's almost certainly for a Thompson BB, as suggested by Juvela. Both use the same principle for the bottom bracket but the three piece cranks used with the Thompson allow for a smaller diameter shell.

I'm aware of at least one hybrid system. In 1954, CCM introduced it's Cycosonic Drive. It used the smaller BB shell but with a blister between the collars for the chainstys. The blister provided the clearance necessary to install and remove a one piece crank. Another innovation was the use of tapered roller bearings which extended life but also allowed for a bigger opening in the cups to accommodate the crank.

The lack of gear cable routing fittings on the subject frame my be due to the age and/or level. Thompsons were generally used on low end bicycles and these bicycles often used cable routing clamps, as opposed to brazed-on fittings. This was very common, even on some high end bicycles, during the early bicycle boom. Gear cable fittings would eventually trickle down through the levels, only to be replaced in the late 1980s by the plastic router installed under the shell.

The abnormally thicker shell may be due to lower strength steel and/or the manufacturing method, though the collars don't appear overly thick.

Bike tinker man

I do thank both Juvela, & T-Mar for their excellent replies:-

I must admit I've never seen those Thompons axle crank systems before, one is always learning, thanks, so that explains it, really appreciate the information.

Another good point as mentioned by T-Mar was they may have intended to use the clamp on shifter cable supports, I did look on the back of the down tube there was no form of raised ridge to support any type of friction shifters, so if they were intended no doubt to be stem mounted.