How do I replace bearings in a jackshaft?

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SUMMARY

This discussion provides a detailed guide on replacing bearings in a jackshaft housing, specifically for a mid-drive electric bicycle kit. The bearings in question are identified as deep groove ball bearings with an inner diameter (ID) of 15mm, outer diameter (OD) of 28mm, and a width of 7cm, likely corresponding to the part number 6902. The process involves using a press to remove and install the bearings, ensuring that only the bearing rings are pressed to avoid damage. Proper techniques and tools are emphasized to prevent costly mistakes.

PREREQUISITES
  • Understanding of bearing specifications, specifically deep groove ball bearings.
  • Familiarity with press fit and interference fit concepts.
  • Basic mechanical skills for disassembly and assembly of components.
  • Knowledge of safe handling practices for aluminum and steel components.
NEXT STEPS
  • Research the specifications and sourcing options for 6902 deep groove ball bearings.
  • Learn about using a hydraulic press for bearing installation and removal.
  • Watch instructional videos on YouTube regarding bearing replacement in similar applications.
  • Explore techniques for heating aluminum to facilitate bearing removal and installation.
USEFUL FOR

This discussion is beneficial for DIY enthusiasts, bicycle mechanics, and anyone involved in the maintenance of electric bicycles, particularly those needing to replace bearings in jackshaft assemblies.

remush
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Hi all,
I need advice in how to replace bearings in a jackshaft housing.

The housing is about 9cm long, and is made out of Aluminium.
It has cups at each end with bearings currently fitted that need replacing.
There is a hardened solid steel shaft running through the inside of the bearings, that protrudes about 4 to 5 cm each side.

the shaft is 15mm thick.
Here's an example of something similar, except my jackshaft is just a cylinder.
example

The bearings are ID 15mm OD 28mm 7cm wide.

The shaft to bearings is a press fit, or what is sometimes called a interference fit.

I have no special tools at home to do the job. The jackshaft is a part of a mid drive electric bicycle kit, mounted on a bicycle I use as a food courier. I've found a few workshops that will take on the job but the wait time is 1 to 2 weeks, time that I wont be earning money.

Advice and suggestions welcomed and appreciated
Thank You
 
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Welcome to PF.

The bearings are probably deep groove ball bearings.
Can you read the part number and suffix?
ID 15mm, OD 28mm, 7cm wide, is probably a commodity part number 6902.
The suffix will identify the seals, probably 6902-RR or 6902-2R meaning rubber lip seals.
They will be really cheap from any bearing supplier.

To dismantle the unit, first check for and remove spring retaining clips. See if you can find a lawn mower, bike or car mechanic workshop with a small press you can use. You will have to put the assembly in some sort of press, that will push the shaft out with one bearing. Then push that bearing from the shaft, and the other from the housing.

Assembly is the opposite sequence, but you must press only on the bearing rings that are a tight fit, so you do not bruise the bearings.

If you do the job with a hammer and old water pipes, and it goes wrong, you will have to buy more bearings. Take care not to dent the shaft or fracture the aluminium casing. If the bearings are a tight fit in the casing, warm it all up so the aluminium expands and the fit is easier.

Search YouTube for a video.
 
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