FT: Frame (Twin) Rebuilding RFM bearing/shaft/bearings ?

[Steve F]

So. I have all the books and nothing I'm reading tells me about what I'm seeing.

When I took the thing apart I had shims under the taper outer races on both sides - not referenced anywhere - or shown in the spares book . Putting it back together I find.

Shoulder to shoulder on the shaft = 4.375". Put the taper bearings on the shaft and the gap between the seats of the outer races is 4.445". But the shoulder to shoulder distance in the RFM for the outer bearing seat to seat is 4.180 inches.

That tells me I have to shim the outer race on each side at least (4.445 - 4.180) /2 i.e. 0.1325"

That 'set-up' isn't mentioned in anything I read. Is this usual/common. Or have i got something odd going on. Everything I read says shim the inner race on the shaft, but for that to happen I'd have to have almost a 1/4 less shoulder to shoulder on the shaft

 

[greg brillus]

Steve, You've got the wrong bearings, meaning the cups and cones are not a match. Are these new bearings or are you refitting what was there before.....?

 

[Martyn Goodwin]

All the information you seek is in the Riders Handbook. Here is an extract from mine, the 3 rd edition, published in 1950.

Dismantling and Adjusting Hubs

Except that the rear one is wider, both hubs are of identical construction and the following remarks apply to both. After removal from the frame, remove one axle nut and lift off the brake-plate. (NOTE.—By holding the cam-arm with one hand whilst turning the nub with a spanner, the brake shoes will be applied and so will prevent the brake plate and axle from turning.) Remove any shims which there may be between the brake-plate and bearing, keeping them together for subsequent assembly, and then push or gently tap the axle out, together with the other brake-plate.

The bearings, brake drums and brake shoes can then be cleaned in readiness for re-assembly. Lying between one inner bearing race and one shoulder on the axle will be found some more shims, which are for the purpose of adjusting the bearing clearance. To check this, assemble the axle and bearing with the latter free from grease, and with the felt grease-retaining washers temporarily omitted.

Tighten the brake-plate nuts and verify that a perceptible amount of play can be felt at the rim if the axle is held firmly in the forks or in a vice and the rim alternately pulled and pushed sideways. The correct amount of play is 1/32 in., if more can be felt, shims must be removed from behind the inner bearings. The shims are of varying thickness to enable a fine adjustment to be made. If new parts are being fitted, there is a possibility that no play will be felt ; in that event, shims must be added, as the roller bearings will rapidly fail if run with insufficient clearance. When the adjustment is correct, dismantle the hub and pack each bearing fully with high-melting point grease, and replace the felt washers if the old ones appear to have been allowing grease to leak past.

The purpose of the shims between the bearings and brake plates is to adjust the clearance between the edges of the plates and the chamfer in the drums, and their thickness should be such that the wheel rotates freely, but with the minimum possible clearance between plates and drum. Attention to this point by experimenting with shim thicknesses will ensure that water and dirt are excluded from the brake.

Under normal circumstances the rate of wear in the hub bearings is low, and provided the play at the rim does not exceed 1/32 in., it is best to replace all shims in the same order as they were before. If for any reason new bearings have to be fitted, it is likely that the thickness of shims fitted will need to be altered considerably. It is essential that the axle-nuts stand slightly proud of the ends of the hollow axle, so that they are finally locked when the solid axle is tightened. If necessary, shims MUST be placed between nuts and plates to ensure this.

 

[bmetcalf]

Are you looking at the RFM pivot bearings?

 

[greg brillus]

I think he is talking about the front pivot bearings of the swing arm, not the brakes.......But I could be wrong. In which case, when you set the bearing clearance you should shim them so that with both hollow axle nuts done up nice and firm, you should just be able to spin the hollow axle with your fingers. This is NOT how you set up the wheel bearings although they are the same. The axle/shims/nuts need to be set up so that the assembly is a nice snug fit between the mating surfaces at the rear of the gearbox/primary. Generally the axle nuts should overhang the hollow axle threads by some and preferably equal amounts which varies from one machine to another. You should also set up the bearings without grease so as a false reading does not occur, then disassemble and pack the bearings in the normal way. It is time consuming but worth it when done correctly. Cheers and good luck..........Greg.

 

[chankly bore]

The bearings used on the rear frame pivot are usually H22 (09074/09196) 3/4" i.d. tapered rollers. Some machines made during the Korean war may have had H22/1 (09067/09165) bearings which have a narrower cup and cone. I have personally never known metric bearings to be used here, though they are often found in the wheels. My S.K.F. automotive catalogue says that these cups and cones can be swapped about. If you have the narrower set, they should have a spacing ring .125" on the inside, unless the factory altered this machining dimension, which is unlikely, and a .100" spacer on the outside of the cone. The 09194 cup can also be used, it just has a wider radius on the "fitting" edge.If this is a Comet, don't forget the F112 spacer on the timing side. It should measure1/2"x1.3/8"x 5/16" wide.This part is not shown anywhere. Follow Greg's advice.Cheers.

 

[BigEd]

Shimming up the taper roller bearings is something you probably don't have to do on most other makes of motor cycle. When you are working from a basket case it can be quite confusing when you find that you have three hollow axles (H15/1, H15/2 and F39/2) for hubs and RFM that are different lengths.

 

[greg brillus]

The swing arm bearings need a small amount of "Pre-load" to help maintain nil movement of the swing arm in service, whereas the wheel bearings need a small amount of running clearance to allow for lubrication mostly. Exactly the same as setting up taper roller bearings on the front wheel of an older car. Because shims are used in all three locations it is best to set them up "Dry of lubricant" so you can feel what is going on without the drag of grease In the rollers, then once you are happy, only then do you pack the bearings with grease. Keep asking questions, you will learn as you go. Cheers............Greg.

 

[Nulli Secundus]

I always thought (could be wrong) that the clearance on taper roller wheel bearings was to allow for expansion when they are warmed up by the brakes.

 

[chankly bore]

Right there! .005" in shims equals 1/32" shake at the rim, cold. Hard to explain this to some local testers.