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sealed bearings on drive shaft and hub

Technical help for all early models, A, B, C, LC, D, LD, E & F models

sealed bearings on drive shaft and hub

Postby steve c » Sun Apr 30, 2017 5:39 pm

has any one tried sealed bearings on drive shaft and hub assembly?

lubrication for both pairs appears hit and miss , with oil lube blessed with shards of gear tooth with open bearings,

have you been fitting c3 grade bearings in this application , c3 give more clearance for hot running? do not know whether or jap bikes don't just run std clearance in a worse application ie more power

you could get 3 off 6004 20x42x12 bearings in the tailpiece or 2 off 63004 2RS 20x42x16 and a shortened spacer and an oilseal bracing it up a good amount with less load than failing 6004 or the 8mm wide ones 1604 type

Same choice for 17*42*12 rear hub, 2off SKF 6203 C3 bearings sealed or open bearings

many motor bikes use sealed bearings in these sizes for the wheel spindles with higher performance so should be fine
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Re: sealed bearings on drive shaft and hub

Postby jbcollier » Mon May 01, 2017 5:52 pm

Anything facing a seal I use a sealed bearing and then pop the inner seal out. C3 is fine and is more commonly available than nominal. Change your oil and don't shift without the clutch. Voila, no gear chunks in the oil.
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Re: sealed bearings on drive shaft and hub

Postby Steve J » Tue May 02, 2017 3:06 pm

Sealed bearings should be OK, if you want to use them. I'm not sure about using C3 clearance bearings for the pinion group or rear axle, as the depth of mesh of crownwheel & pinion is controlled by shims and gaskets, and accurate setting with looser bearings may be more difficult and less repeatable. (I did once attempt to set the clutch and crank bevels with a C3 tolerance bearing supporting the clutch bell, but went back to a standard clearance bearing as I could not set the backlash between the gears to my satisfaction.) As far as power loss is concerned, I doubt you would notice any real difference between standard and C3.

In terms of bearing failures, the one which is guaranteed to fail eventually is the 16004 bearing on the pinion closest to the gear teeth (in pre-1957 models), as that bearing takes the highest loading. In the Mk3 LD machines that bearing was replaced with the wider 6004 and a 4mm shorter spacer, and the problem seemed to be solved. The French Mk4 LD125 actually used a spacer which was 8mm shorter than the original, and a pair of 6004 bearings (which are usually cheaper than the 16004.) The problem with the bevel gear setups in the shaft drive engines is that the bearings supporting the gears are subject to end thrust as well as side loadings, and plain deep groove ball bearings are not optimised for that application. Angular contact bearings would be better for taking the end thrust when supporting bevel gears, but I guess that plain bearings are a lot cheaper. In fact, one of the bearings supporting a pinion in the final drive of the C/LC (and the NSU Prima D) had a split inner race, to provide better support when subject to end thrust.

If I intended to improve the system further, I'd be looking for a pair of taper roller bearings for the pinion group to properly deal with the end thrust - I'm not sure that fitting three standard 6004 bearings to the pinion is going to improve matters, as only the one closest to the gear will experience most of the end thrust.
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Re: sealed bearings on drive shaft and hub

Postby steve c » Tue May 02, 2017 8:56 pm

A pair of the 16mm wide bearings should be an improvement stopping wallowing of the pinion and support at the loaded end, specifying taper rollers is probably a bit of overkill for a hobby bike that could do dozens of miles a year, as the 12mm 6004 helps already. Does any dealer sell the light cone washers with washer between for the pinion set.
I will try standard bearings possibly but the is only 5 microns between them, I suspect c3 are specified for areas where combustion raises the running temperature,
I did buy an unsplt Mk3 150 so should be building it soon. Stripped the frame today for repair and blasting. Found three chain drilled slots in the front frame arch hidden with 45 year old filler and a rotten area on the lower rear frame under the panel bracket
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Re: sealed bearings on drive shaft and hub

Postby Steve J » Wed May 03, 2017 2:35 pm

OK - just remember that if you start fitting wider bearings, you are moving the centres of the bearing tracks closer together. For the one nearest the pinion head, it's moving the support for the pinion further from the point that the load is applied. I don't really see why you think the pinion 'wallows around' with 2 good bearings, or how adding a third midway between the two existing ones is going to improve matters. I've never seen any indication that there is a problem, provided the bearing closest to the gear end of the pinion is a 6004, not a 16004. (I did once have a 16004 pinion bearing fail on an early engine - it destroyed both 16004 bearings, pinion and took a couple of teeth off the crownwheel.)

If you look closely at the ratings of the 63004-2RS and 6004 bearings, you will see the static and dynamic loadings are pretty much the same, and the internal dimensions are the same - apart from the greater width, which is to allow the rubber seals to be fitted.

If you are talking about a hobby bike which covers only a few miles a year, let me reassure you. Around 1970, I rebuilt a Mk2 LD150, fitting new bearings (a 6004 and a 16004) to the pinion group. The same scooter is now sitting in my shed awaiting restoration. The engine has not been removed from the frame since 1970, and the pinion and rear axle have not been disturbed or failed since I assembled them - over 17,000 miles ago!
Unless you plan to do something radical to the engine to produce some serious power, I wouldn't waste time and effort to squeeze an extra bearing in the pinion group. However, if you do manage to produce some serious power, you'll have other more important things to worry about - like crankshaft tapers, torsion driveshafts & rear axle shafts to name just three.... :roll:

If you still need a pair of the light cone washers and spacer washer, just PM me your address and I'll put a good used set in the post to you.
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Re: sealed bearings on drive shaft and hub

Postby steve c » Wed May 03, 2017 10:29 pm

They seem a nicely made engine, I am probably dialling in to a problem that is not there but I did inherit a box of collapsed pinions with mangled teeth and was rather assuming they all ended their days due to this weak point, I am 6'2 and 15 stone and tend to find weak areas of any design quite quickly.
On the later li /GPcranks every one goes mad for NU2205 bearings even though they are nominally bigger then NU205 earlier type.
Last edited by steve c on Fri May 05, 2017 5:16 pm, edited 1 time in total.
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Re: sealed bearings on drive shaft and hub

Postby Steve J » Thu May 04, 2017 9:54 am

The engines aren't too bad, provided you treat them fairly gently! If you got a box of mangled pinions, I'll bet they came from the engines with 2 x 16004 bearings on the pinion group. I've actually got a 16004 bearing that I pulled from a transmission case a few months ago - there's about 3mm of end float, as the sides of the ball races have worn away. :o That was well on the way to total failure, although the pinion teeth were still in reasonable condition.

The other way to find out the weak points of the design is to modify & port the engine. I did that, fitted a 22mm SH2/22 carb, and rode it like an idiot (I was a lot younger and lighter in those days...) At one stage, I was averaging about 900 miles to the crankshaft - they all fractured at the taper. Torsion driveshafts can fracture if you subject them to shock loads, and you don't have to try too hard. The rear axle is very thin, and the splines holding the crown wheel can twist and eventually fracture - never build an engine without checking them carefully for cracks or twisting.

In the GP engines, the NU2205 bearing has the advantage over the NU205 bearing in that the rollers & track are wider, and it doesn't have to support any axial loads.
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Re: sealed bearings on drive shaft and hub

Postby jbcollier » Thu May 04, 2017 2:20 pm

I put a stroked Li crank in mine as well as uprated cylinder, 24 mm carb and an expansion pipe. Snapped one rear axle fairly quickly but I think that was a shimming error. Couple of K on it now with no further issues
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