Non Laverda: Bearing spacer tube

chrisk

chrisk

Hero member
Location
Brisbane, Australia
I?m in the process of building up a rear wheel hub. I need to make up a bearing spacer tube. How should I measure the required length of the spacer tube?

My thoughts are to fit the bearings, measure the distance from bearing outer edges, and subtract the bearing widths. Feasible? Or is there a better way?
 
I fitted one bearing, measured from the fitted inner edge to the machined inner edge of the hub on the other side. Machined up a spacer, leaving it a gnats long and then pop into wheel and machine it so it flush.
It?s better to be minutely to long - if it too short it?ll pinch the bearing.
I had to do this to my Morini that has Laverda rear hub/ brake fitted.
 
I used steel for mine. Aluminium is a little more compliant which might be useful if you get it a wee bit too long. It wouldn't matter if it squished a little bit when you tighten up the axle nut.

The acid test is to assemble the wheel, tighten up the axle and make sure it spins freely. If it passes that test, at least you know you haven't made it too short. If the spacer is too long, it just means one of the bearings won't seat all the way home in the hub. That's not a big deal if its only a few thou, but you don't want it sticking out by 5mm.
 
If the length isn't correct the 'squash' being applied to the bearing will be incorrect , resulting in the bearing failing either sooner or later.
Also there is normally a thin steel spacer between the outer shell of the bearing and the wheel bearing housing which needs to be taken into account?
How about making up a 'tube' that has been calculated to be correct, using some all thread, insert the thin steel spacers, couple of washers outer dia to fit bearing housing, inner to allow all thread through . Build up with supporting tube in place , torque to specified wheel spindle nut. If it turns the tube is too long, too short and the all thread will lock up. I suppose you be looking for that point where you could turn the all thread with a spanner.

Bearings are designed to work with just the right amount of squash.

Maybe some one has recorded the original length of an original tube?

Andy
 
KERMIT1200 said:
Bearings are designed to work with just the right amount of squash.
Andy
Click to expand...
Could you explain this for a normal caged ball bearing for us?
Virtually every time I fit wheel bearings, when both sides are seated, there is a scrap of resistance and the spacer cannot move. A careful tap or two then with my plastic hammer on the centre of a bearing until they move without resistance, at which time the spacer also can just be moved. That is how I was taught and I have never had problems with bearing failures. This ties in with the description above of the spacer being just a smidge longer than the gap between the seated bearings.
 
The inner tube is there to support the inner bearing shell . Basically it shouldn't be being forced to move out of alignment with the outer shell. If the tube is too short the bearing will collapse  from lack of support, if too long will cause the bearing not to seat properly causing failure.

Roller, taper, angular bearings will all suffer if incorrect pressure (squash) is applied.

Over tighten a taper bearing (s) on yokes, the steering doesn't work as required even up sets the handling bearing fail quite quickly, too loose and well it just doesn't steer! OK thats the extremes but shows what too little / too much pressure can achieve .

With wheel bearings you'll looking for that pressure point where the bearings are well supported, but are not being pressurised too much or too little and thus allow the wheel to turn freely.Setup correctly and the bearings should last for a lot of miles.
 
KERMIT1200 said:
The inner tube is there to support the inner bearing shell . Basically it shouldn't be being forced to move out of alignment with the outer shell. If the tube is too short the bearing will collapse  from lack of support, if too long will cause the bearing not to seat properly causing failure.

Roller, taper, angular bearings will all suffer if incorrect pressure (squash) is applied.

Over tighten a taper bearing (s) on yokes, the steering doesn't work as required even up sets the handling bearing fail quite quickly, too loose and well it just doesn't steer! OK thats the extremes but shows what too little / too much pressure can achieve .

With wheel bearings you'll looking for that pressure point where the bearings are well supported, but are not being pressurised too much or too little and thus allow the wheel to turn freely.Setup correctly and the bearings should last for a lot of miles.
Click to expand...

I thought that the inner tube was to keep air in the tyre?
I don't understand engineering.

Paul
 
No problem at all if the outer races have a couple of 0.1mm axial clearance within the hub.  If their interferance fit within the hub bore is OK, the bearings will find a sweet spot with a gentle clout on one of the inner races, as described by Tippie.

The inner races need to be positively located and supported by the inner distance tube in order NOT to preload the bearings, ie, the distance tube can/should be slightly longer than the axial distance between the outer races in the hub.  The distance tube should be a sliding fit between both inner bearing races.  If it is tight, chances are the bearings are already loaded, if it is excessively loose, they certainly will be loaded when the axle is tightened, and quickly be knackered.

Deep groove single row ball bearings, as commonly used in motorcycle wheels, are not designed to carry axial loads.  They will tolerate slight axial loads, but that's it.

If axial loads are to be taken up with ball bearings, angular ball bearings are required.  Commonly used in bicycle headstocks and still in many motorcycle headstocks, as a paired unit in automobile wheel bearings that also carry drive shafts.  Angular bearings may be preloaded to a certain amount, but not very much.

piet
 
I sourced a section of cromo tube with the perfect 22mm ID for the Yamaha axle I'm using up front. It's thin wall cromo from a racing car roll cage (thin c/w std steel) but plenty strong enough under compression when I tighten the axle. It's lighter than any alloy one of a thickness I would trust.

Bicycle quick release axles are hollow and they will undergo a certain amount of compression once the QR lever is tightened. Correct bearing cone adjustment dictates that a certain amount of freeplay should be felt with the qR lever loose but the play will disappear once it has been tightened. Similar idea with the moto spacer tube - if it can compress when the axle nut is fully tightened this needs to be taken into a/c.
 
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