Indeed. I always take the handbook with me so they can read the manufacturers' recommendation.
Last edited:
FT: Frame (Twin) Rebuilding RFM bearing/shaft/bearings ?
- Thread starter Steve F
- Start date
Indeed. I always take the handbook with me so they can read the manufacturers' recommendation.
The expansion of the hub is a possibility, though I would think if the hub got that hot to affect the clearance, you wouldn't need to worry about brakes, as there wouldn't be any left...........
.............Hubs that have insufficient play in the bearings end up with the outer race spinning in the hub, or worse.
.............Hubs that have insufficient play in the bearings end up with the outer race spinning in the hub, or worse.I got em from Coventry spares, so I'm thinking they're right. Certainly right fit on shaft and into the swinging arm. What I'll do is call Coventry and have them measure the shaft shoulder to shoulder to see if that part's wrong
I realize the subject is taper roller bearings, but the following on the general subject of bearings might be of interest. The first two paragraphs in full from the section on "Internal Bearing Clearance" in a 1968 Skefko (SKF) ball and roller bearings catalog:
As a general rule the diametric clearance of a ball bearing should approach zero when the bearing has been fitted and is running at its normal operating temperature. For a roller bearing in a general application a certain internal clearance is desirable if the bearing is to operate satisfactorily.
All radial bearings -- except single row angular contact ball bearings and taper roller bearings, where the question of clearance does not arise until after fitting -- are delivered with a certain initial clearance which is greater than that which the bearing should have when running under service conditions. The reason for this is that when the bearing rings are fitted with an interference fit the bearing clearance is reduced due to expansion of the inner ring and/or compression of the outer ring. The magnitude of the reduction in clearance when an inner ring is mounted with a press fit depends on the degree of interference and sectional rigidity of the shaft, ring proportions, etc.
The same recommendation for zero clearance for ball bearings (and some undefined amount greater than zero for roller bearings) is in modern catalogs as well, but with less verbiage to explain the reason. For engine bearings this is an especially important factor when buying and fitting. Too much clearance and an engine will have a knock, and too little the bearing will fail prematurely. Several systems have been used for clearance grades but two common ones are a 'C suffix' after the bearing number (e.g. C3 is one grade looser than "normal") or several circles polished into the the race (e.g. two circles indicates "normal" clearance).
For the size bearings typically used in motorcycles (~2" OD) the difference in clearance between each of the various clearance grades prior to installation is only ~0.0005". Further, the amount of clearance reduction upon press fitting depends on the difference in size between the bearing and hole in the cases. As a result, worn holes won't compress the bearing as much and thus a tighter clearance grade than originally used will be needed in order to have the correct 'zero' clearance after installation. As a rough rule, pressing a bearing in an Al case will reduce the internal clearance by ~50% of the difference in size (e.g. a 0.002" press fit will reduce the internal clearance of the bearing by ~0.001").
Compounding the issue for doing this properly is that, although the steps between clearance grades is ~0.0005" on average, the range of tolerance on this is such that the adjacent grades overlap slightly. Because of this it is possible, for example, to have a bearing of one grade that is a tiny bit tighter than that of the next looser grade. As a concrete example, for Triumph 650 crankshaft bearings the difference of only one clearance grade will result in an engine that runs properly, and one that has an audible 'clunk' when letting off the throttle.
Again, although much of the above doesn't directly apply to the original question, it does give reasons for why bearing clearance is important and why it often isn't a simple matter of swapping in a new one of the same part number purchased on eBay.
As a general rule the diametric clearance of a ball bearing should approach zero when the bearing has been fitted and is running at its normal operating temperature. For a roller bearing in a general application a certain internal clearance is desirable if the bearing is to operate satisfactorily.
All radial bearings -- except single row angular contact ball bearings and taper roller bearings, where the question of clearance does not arise until after fitting -- are delivered with a certain initial clearance which is greater than that which the bearing should have when running under service conditions. The reason for this is that when the bearing rings are fitted with an interference fit the bearing clearance is reduced due to expansion of the inner ring and/or compression of the outer ring. The magnitude of the reduction in clearance when an inner ring is mounted with a press fit depends on the degree of interference and sectional rigidity of the shaft, ring proportions, etc.
The same recommendation for zero clearance for ball bearings (and some undefined amount greater than zero for roller bearings) is in modern catalogs as well, but with less verbiage to explain the reason. For engine bearings this is an especially important factor when buying and fitting. Too much clearance and an engine will have a knock, and too little the bearing will fail prematurely. Several systems have been used for clearance grades but two common ones are a 'C suffix' after the bearing number (e.g. C3 is one grade looser than "normal") or several circles polished into the the race (e.g. two circles indicates "normal" clearance).
For the size bearings typically used in motorcycles (~2" OD) the difference in clearance between each of the various clearance grades prior to installation is only ~0.0005". Further, the amount of clearance reduction upon press fitting depends on the difference in size between the bearing and hole in the cases. As a result, worn holes won't compress the bearing as much and thus a tighter clearance grade than originally used will be needed in order to have the correct 'zero' clearance after installation. As a rough rule, pressing a bearing in an Al case will reduce the internal clearance by ~50% of the difference in size (e.g. a 0.002" press fit will reduce the internal clearance of the bearing by ~0.001").
Compounding the issue for doing this properly is that, although the steps between clearance grades is ~0.0005" on average, the range of tolerance on this is such that the adjacent grades overlap slightly. Because of this it is possible, for example, to have a bearing of one grade that is a tiny bit tighter than that of the next looser grade. As a concrete example, for Triumph 650 crankshaft bearings the difference of only one clearance grade will result in an engine that runs properly, and one that has an audible 'clunk' when letting off the throttle.
Again, although much of the above doesn't directly apply to the original question, it does give reasons for why bearing clearance is important and why it often isn't a simple matter of swapping in a new one of the same part number purchased on eBay.
Steve,
The numbers on the bearing should be 09074 (cone) and 09196 (cup). Those are the wider bearings that are sometimes found in the wheels and always found in the swing arm pivot. The later narrower wheel bearings are 09067 and 09195. I would just check to make sure you have the right parts. Before the race or cup is installed in the RFM you have to insert a washer. That takes up some space also. Finally, there is an outer washer that is placed on the hollow axle before the nut goes on. I know this is in the books, but something has gone wrong.
I just pushed some bearing races in an RFM and I went to try the fit. I am using bits that have been picked out of a box and never mated. They all fit together well with no shims installed, so I suspect something is out of place on your project.
David
The numbers on the bearing should be 09074 (cone) and 09196 (cup). Those are the wider bearings that are sometimes found in the wheels and always found in the swing arm pivot. The later narrower wheel bearings are 09067 and 09195. I would just check to make sure you have the right parts. Before the race or cup is installed in the RFM you have to insert a washer. That takes up some space also. Finally, there is an outer washer that is placed on the hollow axle before the nut goes on. I know this is in the books, but something has gone wrong.
I just pushed some bearing races in an RFM and I went to try the fit. I am using bits that have been picked out of a box and never mated. They all fit together well with no shims installed, so I suspect something is out of place on your project.
David
Dear Steve,
The parts David is talking about can be seen in the cropped picture of MO22 below. The outer Pivot Bearing Dust Washer is F42 and the inner F42/1.
Right, neglected to mention F42, i.d.3/4" o.d.1 15/16"x1/16" wide. F42/1 1" i.d. and similar otherwise. Originally cad. plated steel.
When rebuilding do not forget to put F42 in before you fit the bearing outer race, I have done this many times and it is very hard to get the outer race out a gain,
Should read F42/1
There are a number of alternatives to the original arrangement if you are looking to save weight for racing I am very surprised that the costly arrangement survived the cost cutting moves of the series D perhaps there were sufficient stocks of bearings to cover the period that would determine the fate of Vincents last hope of survival..... About a year