FT: Frame (Twin) Fit of RFM between FT5 and G50

eharris

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Wow, that level of detail is amazing, thanks!

I do have the thinner 09067 bearings, with the 0.1" spacer.

One side (that had E80 relitavely flush with the end of F39) there was 30thou of shim. On the side (where E80 over hung the end of F39) there is a grand total of 70thou of shim (5+30+35).

Measuring F39/2, it's 4.38" between shoulders and about 6.7" overall (latter with a rule as I only have 6" calipers) and anyway it's a nice fit between FT5 and G50.

So I need to investigate these bearings, as well as the cones in the RFM. I am quite sure that they haven't been out in 60 years, and are not going to want to come.
 

Robert Watson

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Not to be too pedantic but the cups are the ones in the RFM and the cones are the ones with the rollers in them......
 

eharris

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On further reflection and having looked up RFM pivot bearings in KTB, I see that Stevens seems to be quite casual about using worn bearings in the RFM pivot. So I might just leave the cups (thank you Robert!) alone, reset the preload as per KTB and then concentrate on getting the E80 nuts flush with the end of F39/2. Given I have the alloy 0.1" outer spacer on these narrow bearings I will probably concentrate on shaving a few thou off that.
 

A_HRD

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Or someone with a lathe can shave a few thou off the E80 nuts - if, as you say, they are overhanging proud of the hollow spindle...
Peter B
 

eharris

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After some time with the micrometer I measured up the nuts, spacers etc (I checked the two E80 off the battery tray and a couple of spare H59/1 that I found) and juggled the shims about until I have a few thou of preload on the bearing but now only 10thou overhang on the end of F39/2 (at one end, the other end is flush).

The biggest problem I'm having here is that the shims are both controlling the pre-load on the bearings and making sure that the nuts come out flush with the ends of F39/2. Where as in the wheels, there's enough flexibility in the RFM/Forks to cope with the variation in length as you shim the bearings.
 

vibrac

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No dont worry about the cups I have in the past taken a few thou off the inner face of the hollow spindle because you can insert shims there as well
For wheels when a 5 thou shim in out out results in no forward and back movement if in or just a smigin when out then leave I it out, on the RFM I would leave it in then add shims on outside of bearings with the dust washers to even out nuts
 

clevtrev

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I don't think that my part is molested, but it is a used original. I have copied it several times in aluminum, but most of my builds are not stock, so it is difficult to compare.

Having measured many hollow axles, I don't think that they are built to the drawing except in the most critical areas. Some have undercuts at the shoulder, some do not. The shoulders themselves are various widths (although the distance between the shoulders is more accurate. The center diameters vary on most. They all seem to work well.

If you buy one at a jumble it is difficult to know which position it is destined for if the seller is not certain:
View attachment 28343
All of the above are stock. There are two more for the front stand pivots, but they are easily distinguished.

The easy ones to pick out of the bunch are the metric hollow axles. They have "step downs" from the bearing pad, which is .786" or 20mm to the stock brake plate hole of .75". It is very obvious on the rear axle at the bottom and less obvious (but identifiable) on the second axle from the top, which is metric. The RFM pivot is the middle hollow axle.

The imperial bearings, narrow or wide, use the same hollow axle. As a result, the narrow bearing has to be positioned in a way so the hollow axle works with the spacing of the narrow bearings widened out to fit the wide bearing hollow axle. As Chankly mentioned, two spacers are needed: one under the race at 1/8" width to compensate for the narrow race, and one under, or in between the brake plate and the bearing cone to compensate for the narrow cone.
View attachment 28344
I could not find a cone easily, but the important items are the spacers, which may be in a box of bits, but remain unrecognized.

Narrow:
View attachment 28345


I would wonder if the E80 nuts are at different positions on each side because the shims were not split between the two sides?

David
How about, they might be that way to improve the chain line ?
 

davidd

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That could be possible. Because I usually fabricate the plates and spacers on an RFM and transmission, I build everything to the chain line in the dry build from previous measurements. Because I turn the spacers for both sides of the RFM (if there is no F103 in place) I generally do not fool around with the hollow axle itself. I build around it.
DSCN3203.jpg

With no F103 on the left I can shift the chain line easily because there is a spacer on both sides. With an F103, the width of the hollow axle would be the best way to align the rear sprocket to the left.

David
 
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