21-02-2019, 12:54 AM
(This post was last modified: 21-02-2019, 01:04 AM by Tony Press.)
Jeff,
"Whilst an original R&M was designated an MRJ1 1/4" an original (pre 1969) Hoffmann would have been labeled as an RMS12 and the equivalent SKF 402318. The bearing dimensions being 1 1/4" x 3 1/8" x 7/8" - this information from a 1950 R&M / Hoffmann / SKF catalogue."
R&M Bearing MRJ 1 1/4 and Hoffmann RMS12 equivalent in SKF is CRM 10 - not sure where the SKF 492318 comes from- possibly a later designation for that shown in early SKF listings as CRM 10 AU. I believe this was a variation with special internal clearance and possibly even slightly 'barreled' 'rollers.
I would think the likelihood of finding any SKF CRM 10 AU bearings extremely unlikely so we must use the standard CRM 10.
The recommended shaft tolerance for the 1 1/4" bore bearing is listed as k5i: +.0007" to +.0003"
Ruairidh,
"Would these bearings last longer do you think?
I was discussing with another Forum member a few weeks back how the bearing here needs regular change, unlike the front two that hardly ever wear out. Any help at the back seems a good idea in theory, do extra rollers provide that in practice?"
The full complement Roller Bearing would have greater load capacity which would lead to a longer calculated life.
Having said that as you would understand parallel rollers are subject to roller end loading when subject to miss-alignment - which happens when the shaft 'whips' - I don't know how rigid the Phoenix crank is compared to the standard heavy crank, but still being two bearing I would think some 'bending' could occur.
The full complement roller would tend to be stiffer and maybe more prone to roller end loading ?
"Whilst an original R&M was designated an MRJ1 1/4" an original (pre 1969) Hoffmann would have been labeled as an RMS12 and the equivalent SKF 402318. The bearing dimensions being 1 1/4" x 3 1/8" x 7/8" - this information from a 1950 R&M / Hoffmann / SKF catalogue."
R&M Bearing MRJ 1 1/4 and Hoffmann RMS12 equivalent in SKF is CRM 10 - not sure where the SKF 492318 comes from- possibly a later designation for that shown in early SKF listings as CRM 10 AU. I believe this was a variation with special internal clearance and possibly even slightly 'barreled' 'rollers.
I would think the likelihood of finding any SKF CRM 10 AU bearings extremely unlikely so we must use the standard CRM 10.
The recommended shaft tolerance for the 1 1/4" bore bearing is listed as k5i: +.0007" to +.0003"
Ruairidh,
"Would these bearings last longer do you think?
I was discussing with another Forum member a few weeks back how the bearing here needs regular change, unlike the front two that hardly ever wear out. Any help at the back seems a good idea in theory, do extra rollers provide that in practice?"
The full complement Roller Bearing would have greater load capacity which would lead to a longer calculated life.
Having said that as you would understand parallel rollers are subject to roller end loading when subject to miss-alignment - which happens when the shaft 'whips' - I don't know how rigid the Phoenix crank is compared to the standard heavy crank, but still being two bearing I would think some 'bending' could occur.
The full complement roller would tend to be stiffer and maybe more prone to roller end loading ?