[Thomas]

Hi all!

I discussed the rear hub assembly with a fellow vintage motorcyclist again and we believe that the suggestion to install a needle roller race found in the pdf below should be waived. Why?

Power is transmitted to the rear wheel via the sprocket (along with some 'off-throttle' braking effect. When the brake is applied the reverse happens. The issue here is that the brake and chain sprocket are not within the bearing, but are out-lying.This means that forces are not only in a straight(ish) line as in other motorcycles without a detachable wheel. There is also a tendency to pull/push the the wheel back and forth.This motion increases as the two wheel bearings develop any play - the motion is present in all bikes as the sprocket & drum are invariably off-centre. The brake drum has a hole through its centre and if the play is excessive then the drum will touch the sleeve and cause a bit of wear as can be seen at my sleeve (see pics). And indeed, my wear is separated by 180°, as expected. The wear is not caused by the drum/sleeve but by the wheel bearings becoming worn. Hence, instead of installing a third needle bearing one should take care for the wheel bearings! In addition, there is simply not enough metal within the drum to add a needle roller bearing (which needs a cage and adequate lubrication) and it would probably seize/fracture the drum. That means, the gap between sleeve and drum is there for good reason and the overall hub design is very reasonable (in contrast to the statement of the fellow in the letter).

Instead of selling my lovely motorcycle I will now check whether there is any play in the wheel bearings. If it is they need to be changed. If not, I might as well take them out and check again once washed out with White Spirit - they must rotate very smoothly, no noise and no 'checks' as they spin. If they're all good I'll re-pack with grease.

Cheers, Thomas

[Thomas]

Hi all!

I just checked my rear brake shoes and now see that I have the same rear wheel construction as in the 1936 Model 9 from Ytzen and with the same bolt as in Cees' Model 9. There is no third bearing supporting the rear sprocket/drum. The wheel runs completely without bearing support on the bolt/axle. In the attached pdf from singleminded (I upload it here again for convenience) I notice that it suggests an INA race or something similar (I can't identify it in this handwritten drawing). But there is nothing, of course. 

Cheers, Thomas

[Ytzen]

Dear forum readers,
My name is Ytzen Tol, and I have owned a 1936 Model 9 Sports since late last year.
On my bike too, the rear brake drum appeared to have come loose from the hub.
As this is also a concern at Velocette, it did not seem too serious to me.
However, after disconnecting and inspecting it, it appeared that previous owners had come up with some, shall we say, less professional modifications. This raises questions and perhaps I can get some answers through this forum. I have also attached some photos.
The PDF sketches referred to by Singleminded in this topic basically match the construction as applied to my bike.
However, against the wheel hub of my bike a plate has been welded in which 3 holes have been drilled again, also through the hub flange. The pitch circle of these holes is approx. 88.9 mm. (3 ½")
The original holes in the hub are on a pitch circle ca 77.8 mm. (3 1/16")
The brake drum; 20 inches with 45 teeth 5/8 x ¼. There is no mark or sign on this drum. The pitch circle on which the 3 bolts sit is approx. 88.9 mm. (3 ½")
Question is this a Sunbeam drum?
The hub: it has been drilled out so that metric tapered bearings will fit. 20 x 47 mm.
The carrier tube is of course also diameter 20 mm at the bearing positions.
The rear hub is also different from the hub in the front wheel. See picture.
Question is this perhaps an older/different type of Sunbeam hub.

[Cees van Rhijn]

Well Gentleman's
Sorry for the late reaction.
Thanks for this discussion, I learning. I think I know what to do. I let you know how I think to solve this problem.
regard Cees van Rhijn

[Rick Parkington]

Well, that's very interesting. I'd say the clear implication here is that Sunbeam were not 100% happy with the support provided by a ball bearing and went for the greater rigidity of a plain bush - INA needle rollers being a thing of the future at the time - only to find that it couldn't master the flex and packed up under load.
It's a funny thing, most of us do tiny mileages on our Sunbeams compared to what they were expected to cope with in their day so these dramas seldom occur. I rode my 9A from Edinburgh to the Isle of Man and back three years running - but I carry out my maintenance in a well lit workshop with an elevated bench and tools/equipment the original owner probably didn't even know existed. It must have been a very tough call for manufacturers to make bikes that could survive faced with the tools and knowledge of owners of the day.
Paul, yes, I'd agree that my rear wheel splines are worn - but I'd call it a symptom rather than a cause of the problem. I doubt they were ever 'tight' otherwise the QD wheel would be difficult to fit or remove. The bolts should support the spline-fit to prevent chatter that causes rapid wear. I'd guess the bolts worked loose on mine and the owner didn't notice, so the load was taken by the splines and the bolt holes wore oval. The best way to redress this, other than welding and re-machining the splines, is to make the bolts a dowel fit. It was working well until we got wiped out by a blind car driver last year - now I have bigger problems to worry about!
Cheers Rick   
   

[singleminded]

If this PDF file has loaded properly it should show the wheel bearing and modification for a 1936 model 95. having checked Sean Kelly's Sunbeam land parts lists it appears that the parts are common to the 9 as well.
this may shed some light on the subject.

[phutton]

Yes Rick, the Club's replacement sprockets are made to accept a readily available standard bearing, with a sleeve to complete the assembly - exactly as the 1927 M90 did! We can supply the sleeve and the bearing, once we replenish our stocks, which will be sometime in the first quarter of next year.

The 1936 arrangement appears different, and there is no mention in the Parts List of any bearing supporting the drum/sprocket. The wheel bearings are all taper rollers, which were probably considered to give adequate support for the drum when bolted up to the hub. Please be aware that this is just "desktop" work, and I cannot claim hands-on knowledge of the Burman gearbox models.

P.

[phutton]

Hi Rick - doesn't the movement mean that your splines are knackered?!

P.

[Rick Parkington]

Good question, Thomas! I do wonder if the club's new sprockets are made to accept a different bearing or the original. Probably the answer would be to modify the sprocket/drum and even the stub axle to take a different bearing if the problem arises - but let's hope it doesn't!
Cheers Rick 
   

[Thomas]

Ah, very valuable advice which I will follow. I wonder, though, what I need to do if the bearing once needs a replacement...  
Thanks a lot!

[Rick Parkington]

Hi Thomas, yes, that's correct - although the actual wheels are the same there is no bearing in the front brake drum. I assume this is because the load going through the rear sprocket is continuous and far greater than that created by the font brake.
Sorry, when I said 'when dismantled' I meant when the hub and drum are separated - that is, there is no external grease nipple that allows it to be done when assembled. Removal of the bearing would probably be difficult and may result in damage - obviously heat won't help as it would with a bearing in an alloy casing and I don't think you can get behind the bearing with a lever or punch. I would wash it out as best you can while fitted and pack in fresh high melting pint grease from the outside. Pushed in with the fingers it will get through to the back okay.
One final thing, in case anybody ha the same problem. On my 9A rear wheel, the three drum to hub bolts regularly came loose. I don't like using loctite on fittings like this so instead I carried around a tool to tighten them in the toolkit. When I eventually looked closer I realised that the holes in the hub had worn slightly oval, that meant there would always be some movement between drum and hub which inevitably loosened the bolts. I bored the holes slightly oversize and made bolts with shoulders to fit the new size and since then it's been fine.
Cheers Rick 

[Thomas]

Hi Rick!

The Sunbeam quickly detachable rear wheel has two bearings in the wheel hub and another in the rear sprocket/brake drum.

That is interesting and I didn't realise that until now because my 1937 front wheel does not have a third bearing, although also quickly detachable. It's obviously time to pay attention to my rear wheel.

It can only be greased when dismantled but this should be no problem...

Can you give some information about how to get the bearing out?

Cheers, Thomas

[Rick Parkington]

H Cees, I'm afraid I have no experience of the 1936 Model 9 but since nobody else has answered and I suspect it is similar to the earlier bikes, here's my opinion. The Sunbeam quickly detachable rear wheel has two bearings in the wheel hub and another in the rear sprocket/brake drum. The sprocket/drum bearing is an unusual  size that has been unobtainable for a long time. The clearance in it should be no more than in any other journal type bearing so it could be that yours may be worn out although because (I think) it's quite a narrow bearing, it's likely that there will seem to be a lot of movement when it is unsupported. I would check it with the wheel assembled on its axles but without bolting the wheel hub to the sprocket, looking for any up and down movement.
It can only be greased when dismantled but this should be no problem - there's no need to grease it regularly but use a high melting point grease.
Hope this helps and all the best
Rick   

[Cees van Rhijn]

Hello
The rear wheel brake drum frme my Model 9 is mounted in the frame with a kind of bearing bolt. Can someone inform me if this is really an extra bearing (and if so) what the clearance of this bearing is. It seems to me that this construction relieves the wheel hub against too high torsional forces. Now the clearence is more than 1,5 mm. And if it is a bearing how do you lubricate it.
.

Cees